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scifigeneration · 5 years ago

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Even planets have their (size) limits

by Natalie Hinkel

A planet-forming disk made from rock and gas surrounds a young star. NASA/JPL-Caltech/SwRI/MSSS/ Gerald Eichstädt /Seán Doran

Scientists have discovered over 4,000 exoplanets outside of our Solar System, according to NASA’s Exoplanet Archive.

Some of these planets orbit multiple stars at the same time. Certain planets are so close to their star that it takes only a handful of days to make one revolution, compared to the Earth which takes 365.25 days. Others slingshot around their star with extremely oblong orbits, unlike the Earth’s circular one. When it comes to how exoplanets behave and where they exist, there are many possibilities.

And yet, when it comes to sizes of planets, specifically their mass and radius, there are some limitations. And for that, we have physics to blame.

I am a planetary astrophysicist and I try to understand what makes a planet able to support life. I look at the chemical connection between stars and their exoplanets and how the interior structure and mineralogy of different sized planets compare to each other.

This sketch illustrates a family tree of exoplanets starting from the protoplanetary disk, which is a swirling disk of gas and dust surrounding a planet (much like a stellar disk but smaller). Gas and dust is pulled onto the planet, depending on the planet’s mass and gravity. NASA/Ames Research Center/JPL-Caltech/Tim Pyle

Rocky versus gaseous planets

In our Solar System, we have two kinds of planets: small, rocky, dense planets that are similar to Earth and large, gaseous planets like Jupiter. From what we astrophysicists have detected so far, all planets fall into these two categories.

In fact, when we look at the data from planet-hunting missions such as the Kepler mission or from the Transiting Exoplanet System Satellite, there is a gap in the planet sizes. Namely, there aren’t many planets that fulfill the definition of a “super-Earth,” with a radius of one and a half to twice Earth’s radius and a mass that is five to 10 times greater.

So the question is, why aren’t there any super-Earths? Why do astronomers only see small rocky planets and enormous gaseous planets?

The differences between the two kinds of planets, and the reason for this super-Earth gap, has everything to do with a planet’s atmosphere – especially when the planet is forming.

When a star is born, a huge ball of gas comes together, starts to spin, collapses in on itself and ignites a fusion reaction within the star’s core. This process isn’t perfect; there is a lot of extra gas and dust left over after the star is formed. The extra material continues to rotate around the star until it eventually forms into a stellar disk: a flat, ring-shaped collection of gas, dust, and rocks.

During all of this motion and commotion, the dust grains slam into each other, forming pebbles which then grow into larger and larger boulders until they form planets. As the planet grows in size, its mass and therefore gravity increases, allowing it to capture not only the accumulated dust and rocks – but also the gas, which forms an atmosphere.

There is lots of gas within the stellar disk – after all, hydrogen and helium are the most common elements in stars and in the universe. However, there is considerably less rocky material because only a limited amount was made during star formation.

Comparison of confirmed super-Earth planets compared to the size of the Earth. NASA/Ames/JPL-Caltech

The trouble with super-Earths

If a planet remains relatively small, with a radius less than 1.5 times Earth’s radius, then its gravity is not strong enough to hold onto a huge amount of atmosphere, like what’s on Neptune or Jupiter. If, however, it continues to grow larger, then it captures more and more gas which forms an atmosphere that causes it to swell to the size of Neptune (four times Earth’s radius) or Jupiter, 11 times Earth’s radius.

Therefore, a planet either stays small and rocky, or it becomes a large, gaseous planet. The middle ground, where a super-Earth might be formed, is very difficult because, once it has enough mass and gravitational pull, it needs the exact right circumstances to stop the avalanche of gas from piling onto the planet and puffing it up. This is sometimes referred to as “unstable equilibrium” – such that when a body (or a planet) is slightly displaced (a little bit more gas is added) it departs further from the original position (and becomes a giant planet).

Another factor to consider is that once a planet is formed, it doesn’t always stay in the same orbit. Sometimes planets move or migrate towards their host star. As the planet gets closer to the star, its atmosphere heats up causing the atoms and molecules to move very fast and escape the planet’s gravitational pull. So some of the small rocky planets are actually the cores of bigger planets that have been stripped of their atmosphere.

So, while there are no super huge rocky planets or small fluffy planets, there is still a huge amount of diversity in planet sizes, geometries and compositions.

About The Author:

Natalie Hinkel is a Planetary Astrophysicist and Senior Research Scientist at the Southwest Research Institute and Co-Investigator for the Nexus for Exoplanet System Science (NExSS), Arizona State University

This article is republished from our content partners over at The Conversation under a Creative Commons license.

#science #featured #astronomy #space #exoplanets #planets #binary stars #TESS #star formation

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spaceexp · 6 years ago

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What Recipes Produce a Habitable Planet

Houston TX (SPX) Sep 20, 2018 NASA's interdisciplinary Nexus for Exoplanet System Science (NExSS) project has awarded Rice University $7.7 million for a multidisciplinary, multi-institutional research program aimed at finding many different recipes nature might follow to produce rocky planets capable of supporting life. As any cook knows, it takes the right recipe and getting the right ingredients to make a tasty dish, Full article

#space #science

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andromeda1023 · 6 years ago

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In the last decade, we have discovered thousands of planets outside our solar system and have learned that rocky, temperate worlds are numerous in our galaxy. The next step will involve asking even bigger questions. Could some of these planets host life? And if so, will we be able to recognize life elsewhere if we see it?

A group of leading researchers in astronomy, biology and geology has come together under NASA's Nexus for Exoplanet System Science, or NExSS, to take stock of our knowledge in the search for life on distant planets and to lay the groundwork for moving the related sciences forward.

"We're moving from theorizing about life elsewhere in our galaxy to a robust science that will eventually give us the answer we seek to that profound question: Are we alone?" said Martin Still, an exoplanet scientist at NASA Headquarters, Washington.

In a set of five review papers published last week in the scientific journal Astrobiology, NExSS scientists took an inventory of the most promising signs of life, called biosignatures. The paper authors include four scientists from NASA's Jet Propulsion Laboratory in Pasadena, California. They considered how to interpret the presence of biosignatures, should we detect them on distant worlds. A primary concern is ensuring the science is strong enough to distinguish a living world from a barren planet masquerading as one.

The assessment comes as a new generation of space and ground-based telescopes are in development. NASA's James Webb Space Telescope will characterize the atmospheres of some of the first small, rocky planets. There are plans for other observatories -- such as the Giant Magellan Telescope and the Extremely Large Telescope, both in Chile -- to carry sophisticated instruments capable of detecting the first biosignatures on faraway worlds.

Through their work with NExSS, scientists aim to identify the instruments needed to detect potential life for future NASA flagship missions. The detection of atmospheric signatures of a few potentially habitable planets may possibly come before 2030, although determining whether the planets are truly habitable or have life will require more in-depth study.

Since we won't be able to visit distant planets and collect samples anytime soon, the light that a telescope observes will be all we have in the search for life outside our solar system. Telescopes can examine the light reflecting off a distant world to show us the kinds of gases in the atmosphere and their "seasonal" variations, as well as colors like green that could indicate life.

These kinds of biosignatures can all be seen on our fertile Earth from space, but the new worlds we examine will differ significantly. For example, many of the promising planets we have found are around cooler stars, which emit light in the infrared spectrum, unlike our sun's high emissions of visible-light.

"What does a living planet look like?" said Mary Parenteau, an astrobiologist and microbiologist at NASA's Ames Research Center in Silicon Valley and a co-author. "We have to be open to the possibility that life may arise in many contexts in a galaxy with so many diverse worlds -- perhaps with purple-colored life instead of the familiar green-dominated life forms on Earth, for example. That's why we are considering a broad range of biosignatures."

The scientists assert that oxygen -- the gas produced by photosynthetic organisms on Earth -- remains the most promising biosignature of life elsewhere, but it is not foolproof. Abiotic processes on a planet could also generate oxygen. Conversely, a planet lacking detectable levels of oxygen could still be alive - which was exactly the case of Earth before the global accumulation of oxygen in the atmosphere.

"On early Earth, we wouldn't be able to see oxygen, despite abundant life," said Victoria Meadows, an astronomer at the University of Washington in Seattle and lead author of one of the papers. "Oxygen teaches us that seeing, or not seeing, a single biosignature is insufficient evidence for or against life -- overall context matters."

Rather than measuring a single characteristic, the NExSS scientists argue that we should be looking at a suite of traits. A planet must show itself capable of supporting life through its features, and those of its parent star.

The NExSS scientists will create a framework that can quantify how likely it is that a planet has life, based on all the available evidence. With the observation of many planets, scientists may begin to more broadly classify the "living worlds" that show common characteristics of life, versus the "non-living worlds."

"We won't have a 'yes' or 'no' answer to finding life elsewhere," said Shawn Domagal-Goldman, an astrobiologist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and a co-author. "What we will have is a high level of confidence that a planet appears alive for reasons that can only be explained by the presence of life."

News Media Contact

Calla Cofield Jet Propulsion Laboratory, Pasadena, California 818-393-1821 [email protected] Felicia Chou NASA Headquarters, Washington 202-358-0257 [email protected] 2018-147

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sciencespies · 3 years ago

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Enjoy it while you can: Dropping oxygen will eventually suffocate most life on Earth

https://sciencespies.com/environment/enjoy-it-while-you-can-dropping-oxygen-will-eventually-suffocate-most-life-on-earth/

Enjoy it while you can: Dropping oxygen will eventually suffocate most life on Earth

For now, life is flourishing on our oxygen-rich planet, but Earth wasn’t always that way – and scientists have predicted that, in the future, the atmosphere will revert back to one that’s rich in methane and low in oxygen.

This probably won’t happen for another billion years or so. But when the change comes, it’s going to happen fairly rapidly, the study from earlier this year suggests.

This shift will take the planet back to something like the state it was in before what’s known as the Great Oxidation Event (GOE) around 2.4 billion years ago.

What’s more, the researchers behind the new study say that atmospheric oxygen is unlikely to be a permanent feature of habitable worlds in general, which has implications for our efforts to detect signs of life further out in the Universe.

“The model projects that a deoxygenation of the atmosphere, with atmospheric O2 dropping sharply to levels reminiscent of the Archaean Earth, will most probably be triggered before the inception of moist greenhouse conditions in Earth’s climate system and before the extensive loss of surface water from the atmosphere,” wrote the researchers in their published paper.

At that point it’ll be the end of the road for human beings and most other life forms that rely on oxygen to get through the day, so let’s hope we figure out how to get off the planet at some point within the next billion years.

To reach their conclusions, the researchers ran detailed models of Earth’s biosphere, factoring in changes in the brightness of the Sun and the corresponding drop in carbon dioxide levels, as the gas gets broken down by increasing levels of heat. Less carbon dioxide means fewer photosynthesizing organisms such as plants, which would result in less oxygen.

Scientists have previously predicted that increased radiation from the Sun would wipe ocean waters off the face of our planet within about 2 billion years, but the new model – based on an average of just under 400,000 simulations – says the reduction in oxygen is going to kill off life first.

“The drop in oxygen is very, very extreme,” Earth scientist Chris Reinhard, from the Georgia Institute of Technology, told New Scientist earlier this year. “We’re talking around a million times less oxygen than there is today.”

What makes the study particularly relevant to the present day is our search for habitable planets outside of the Solar System.

Increasingly powerful telescopes are coming online, and scientists want to be able to know what they should be looking for in the reams of data these instruments are collecting.

It’s possible that we need to be hunting for other biosignatures besides oxygen to have the best chance of spotting life, the researchers say. Their study is part of the NASA NExSS (Nexus for Exoplanet System Science) project, which is investigating the habitability of planets other than our own.

According to the calculations run by Reinhard and environmental scientist Kazumi Ozaki, from Toho University in Japan, the oxygen-rich habitable history of Earth could end up lasting for just 20-30 percent of the planet’s lifespan as a whole – and microbial life will carry on existing long after we are gone.

“The atmosphere after the great deoxygenation is characterized by an elevated methane, low-levels of CO2, and no ozone layer,” said Ozaki. “The Earth system will probably be a world of anaerobic life forms.”

The research has been published in Nature Geoscience.

A version of this article was first published in March 2021.

#Environment

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fumpkins · 5 years ago

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Exoplanets: How we'll search for signs of life

Whether there is life elsewhere in the universe is a question people have pondered for millennia; and within the last few decades, great strides have been made in our search for signs of life outside of our solar system.

NASA missions like the space telescope Kepler have helped us document thousands of exoplanets – planets that orbit around other stars. And current NASA missions like Transiting Exoplanet Survey Satellite (TESS) are expected to vastly increase the current number of known exoplanets. It is expected that dozens will be Earth-sized rocky planets orbiting in their stars�� habitable zones, at distances where water could exist as a liquid on their surfaces. These are promising places to look for life.

This will be accomplished by missions like the soon-to-be-launched James Webb Space Telescope, which will complement and extend the discoveries of the Hubble Space Telescope by observing at infrared wavelengths. It is expected to launch in 2021, and will allow scientists to determine if rocky exoplanets have oxygen in their atmospheres. Oxygen in Earth’s atmosphere is due to photosynthesis by microbes and plants. To the extent that exoplanets resemble Earth, oxygen in their atmospheres may also be a sign of life.

Not all exoplanets will be Earth-like, though. Some will be, but others will differ from Earth enough that oxygen doesn’t necessarily come from life. So with all of these current and future exoplanets to study, how do scientists narrow down the field to those for which oxygen is most indicative of life?

To answer this question, an interdisciplinary team of researchers, led by Arizona State University (ASU), has provided a framework, called a “detectability index” which may help prioritize exoplanets that require additional study. The details of this index have recently been published in the Astrophysical Journal of the American Astronomical Society.

“The goal of the index is to provide scientists with a tool to select the very best targets for observation and to maximize the chances of detecting life,” says lead author Donald Glaser of ASU’s School of Molecular Sciences.

The oxygen detectability index for a planet like Earth is high, meaning that oxygen in Earth’s atmosphere is definitely due to life and nothing else. Seeing oxygen means life. A surprising finding by the team is that the detectability index plummets for exoplanets not-too-different from Earth.

Although Earth’s surface is largely covered in water, Earth’s oceans are only a small percentage (0.025%) of Earth’s mass. By comparison, moons in the outer solar system are typically close to 50% water ice.

“It’s easy to imagine that in another solar system like ours, an Earth-like planet could be just 0.2% water,” says co-author Steven Desch of ASU’s School of Earth and Space Exploration. “And that would be enough to change the detectability index. Oxygen would not be indicative of life on such planets, even if it were observed. That’s because an Earth-like planet that was 0.2% water—about eight times what Earth has—would have no exposed continents or land.”

Without land, rain would not weather rock and release important nutrients like phosphorus. Photosynthetic life could not produce oxygen at rates comparable to other non-biological sources.

“The detectability index tells us it’s not enough to observe oxygen in an exoplanet’s atmosphere. We must also observe oceans and land,” says Desch. “That changes how we approach the search for life on exoplanets. It helps us interpret observations we’ve made of exoplanets. It helps us pick the best target exoplanets to look for life on. And it helps us design the next generation of space telescopes so that we get all the information we need to make a positive identification of life.”

Scientists from diverse fields were brought together to create this index. The formation of the team was facilitated by NASA’s Nexus for Exoplanetary System Science (NExSS) program, which funds interdisciplinary research to develop strategies for looking for life on exoplanets. Their disciplines include theoretical and observational astrophysics, geophysics, geochemistry, astrobiology, oceanography, and ecology.

“This kind of research needs diverse teams, we can’t do it as individual scientists” says co-author Hilairy Hartnett who holds joint appointments at ASU’s School of Earth and Space Exploration and School of Molecular Sciences.

In addition to lead author Glaser and co-authors Harnett and Desch, the team includes co-authors Cayman Unterborn, Ariel Anbar, Steffen Buessecker, Theresa Fisher, Steven Glaser, Susanne Neuer, Camerian Millsaps, Joseph O’Rourke, Sara Imari Walker, and Mikhail Zolotov who collectively represent ASU’s School of Molecular Sciences, School of Earth and Space Exploration, and School of Life Sciences. Additional scientists on the team include researchers from the University of California Riverside, Johns Hopkins University and the University of Porto (Portugal).

It is the hope of this team that this detectability index framework will be employed in the search for life. “The detection of life on a planet outside our solar system would change our entire understanding of our place in the universe,” says Glaser. “NASA is deeply invested in searching for life, and it is our hope that this work will be used to maximize the chance of detecting life when we look for it.”

###

Disclaimer: We can make mistakes too. Have a nice day.

New post published on: https://livescience.tech/2020/05/05/exoplanets-how-well-search-for-signs-of-life/

#PLANETS/MOONS #SPACE/PLANETARY SCIENCE

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100yearstarship · 5 years ago

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100 YEAR STARSHIP ANNOUNCES WINNERS OF THE SECOND CANOPUS AWARDS OF EXCELLENCE IN INTERSTELLAR WRITING

HOUSTON, July 22, 2019— 100 Year Starshipâ(100YSSâ) announced the winners of the Second Canopus Awards for Excellence in Interstellar Writing hosted by actress and writer Nichelle Nichols.

The awards were presented by Nichelle Nichols. While most famous for her portrayal of Lt. Uhura in the original Star Trek television show in the 1960s, Nichelle Nichols has been an active advocate for NASA and space exploration.

The winners are:

· In the category of “PREVIOUSLY PUBLISHED LONG-FORM FICTION”the winner isThe Three-Body Problemby Cixin Liu, Translated by Ken Liu (published by Tor)

· In the category of “PREVIOUSLY PUBLISHED SHORT-FORM FICTION” the winner is “Slow Bullets” by Alastair Reynolds (published by Tachyon Publications)

· In the category of “PREVIOUSLY PUBLISHED NONFICTION” the winner is Welcome to Mars: Making a Home on the Red Planet by Buzz Aldrin and Marianne Dyson (published by National Geographic)

· In the category of “ORIGINAL FICTION” the winner is “The Quest for New Cydonia” by Russell Hemmell

· In the category of “ORIGINAL NON-FICTION” the winner is “Microbots—The Seeds of Interstellar Civilization” by Robert Buckalew

· In the category of “ORIGINAL COLLEGE WRITING” the winner is “A Kingdom of Ends” by Ryan Burgess

100YSS, led by former astronaut, engineer, physician and entrepreneur Dr. Mae Jemison, is an independent, long-term global initiative working to ensure that the capabilities for human interstellar travel, beyond our solar system to another star, exist within the next 100 years.

“Imagination, varied perspectives and a well told story are critical to advancing civilizations. In particular, beginning with the simple question ‘What if?’ pushes us to look beyond the world in front of us and to envision what could be, ought to be and other realities,”said Dr. Jemison. “Both science fiction and exploratory non-fiction have inspired discovery, invention, policy, technology and exploration that has transformed our world.”

The award is named for the second brightest star in the night sky, Canopus, which connects humanity’s past, present and future through fact and fantasy. Over the millennia Canopus not only heralded planting seasons in the Rift Valley, but was a major navigation star for everyone from the Bedouin of the Sinai and the Maori of New Zealand to deep space probes like Voyager. Just as Canopus has helped explorers find their way for centuries, great writing —telling a story well ––is a guidepost for current and future interstellar achievement.

The digital presentation of the 2ndCanopus Awards was done in conjunction with Look Up Lunar Landing. Look Up Lunar Landing is the fourth international Look Up event, following the introduction of Skyfie™ in October 2018 during a 24-hour event; a November 2018 photo curation challenge with NatGeo’s SureShot; and an April 2019 project with Yuri’s Night.

Originally scheduled for live presentation in late 2017, the Canopus Award event, and the Nexus conference that it was a part of, were postponed due to insurmountable challenges faced in the wake of Hurricane Harvey that devastated the Houston area that year. In the intervening time, efforts have been made to reschedule the Nexus and while those plans are still being developed, 100YSS determined that in a desire to celebrate the accomplishments and efforts of the Canopus Awards and its judges, nominees, and winners, that the announcement of the awards would be moved online.

Canopus Award program manager and writer Jason D. Batt notes that, “100YSS is launching the awards at a particularly fortuitous time. The recent announcements of Kepler-452b exoplanet, major financial support of searches for extraterrestrial intelligence and the space probe New Horizons close encounter with Pluto and the amazing images it is generating highlight how we all look up and dream of what’s out there. The Canopus award celebrates that passion that is common to the public, researchers and science fiction fans alike.”

Award category finalists are as listed below:

“Previously Published Long-Form Fiction”(40,000 words or more):

· The Long Way to a Small, Angry Planet by Becky Chambers (Harper Voyager)

· Dark Orbitby Carolyn Ives Gilman (Tor)

· Sevenevesby Neal Stephenson (HarperCollins)

· The Three-Body Problemby Cixin Liu, Translated by Ken Liu (Tor)

· Arkwrightby Allen Steele (Tor)

“Previously Published Short-Form Fiction”(between 1,000 and 40,000 words):

· “Slow Bullets” by Alastair Reynolds (Tachyon Publications)

· “The Long Vigil” by Rhett C. Bruno (Perihelion)

· “The Citadel of Weeping Pearls” by Aliette de Bodard (Asimov’s Science Fiction)

· “Wavefronts of History and Memory” by David D. Levine (Analog Science Fiction and Fact)

· “The Four Thousand, The Eight Hundred” by Greg Egan (Subterranean Press)

· “Whom He May Devour” by Alex Shvartsman (Nautilus)

· “Love and Relativity” by Stewart C. Baker (Flash Fiction Online)

“Previously Published Nonfiction”(between 1,000 and 40,000 words):

· “A Terrestrial Planet Candidate in a Temperate Orbit Around Proxima” by Guillem Anglada-Escude, et al. (Nature)

· “A Science Critique of Auroraby Kim Stanley Robinson” by Stephen Baxter, James Benford, and Joseph Miller (Centauri Dreams)

· Welcome to Mars: Making a Home on the Red Planetby Buzz Aldrin and Marianne Dyson (National Geographic)

· “Let’s All Go to Mars” by John Lanchester (London Review of Books)

· “Our Worldship Broke!” by Jim Beall (Baen Books)

“Original Fiction”(1,000-5,000 words):

· “The Quest for New Cydonia” by Russell Hemmell

· “Luminosity” by Adeene Denton

· “Mission” by Yoshifumi Kakiuchi

· “Envoy” by K. G. Jewell

· “Sleeping Westward” by Lorraine Schein

“Original Non-Fiction”(1,000-5,000 words):

· “Motivatingly Plausible Ways to Reach the Stars” by James Blodgett

· “Microbots—The Seeds of Interstellar Civilization” by Robert Buckalew

· “An Anthropic Program for the Long-Term Survival of Humankind” by Roberto Paura

· “Terraforming Planets, Geoengineering Earth” by James Fleming

“Original College Writing”(1,000-5,000 words):

· “A Kingdom of Ends” by Ryan Burgess

· “Ethics in Space” by Greg Becker

In addition, the following works were noted as inclusion for honorable mention by our selection committee although they were not finalists in any category:

Honorable Mention

· Interstella Cinderellaby Deborah Underwood (Chronicle Books)

· Protos Mandateby Nick Kanas (Springer)

· The Arkby Patrick S. Tomlinson (Angry Robot Books)

· The Destructivesby Matthew de Abaitua (Angry Robot Books)

· “Exquisite Banality of Space” by Leslie J. Anderson, published in Uncanny Magazine

· “Spacefarer’s Creed” by Matt Noble (poetry)

· “Dispatchers from Interstellar Race Relations Log” by Janel Cloyd (poetry)

For more information about award criteria, nomination and submission, visit http://100yss.org/initiatives/canopusaward.

VIDEO ANNOUCEMENT

https://www.facebook.com/100YearStarship/

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ABOUT100YEARSTARSHIP™

100YearStarship™ (100YSS)is an independent, non-governmental, long-term initiative to ensure the capabilities for human interstellar flight exist as soon as possible, and definitely with in the next 100 years. 100YSS was started in 2012 with seed-funding through a competitive grant from DARPA (Defense Advanced Research Projects Agency) for the purpose of fostering the type of explosive innovation and technology and social advances born from addressing such an incredible challenge. To foster such innovation, 100YSS engages in collaborative international programs and projects in research and innovation, science, technology, engineering and mathematics (STEM) capacity building, entrepreneurship and education projects with and between organizations, companies, universities and individuals. Based in Houston, TX, 100YSS recently opened an affiliate in Brussels, 100YSS@EU and is in the process of developing affiliates in Africa and Asia.

100YSSispartofthe DorothyJemisonFoundationforExcellence.Formoreinformation,visitwww.100yss.org.

Find us on social media:

Facebook: www.facebook.com/100YearStarship

Twitter: @100YSS

#Canopus Award #Intersellar #writing #2019 #100 Year Starship

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100ysspress · 5 years ago

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100 YEAR STARSHIP ANNOUNCES WINNERS OF THE SECOND CANOPUS AWARDS OF EXCELLENCE IN INTERSTELLAR WRITING

HOUSTON, July 22, 2019— 100 Year Starshipâ(100YSSâ) announced the winners of the Second Canopus Awards for Excellence in Interstellar Writing hosted by actress and writer Nichelle Nichols.

The winners are:

· In the category of “PREVIOUSLY PUBLISHED LONG-FORM FICTION”the winner isThe Three-Body Problemby Cixin Liu, Translated by Ken Liu (published by Tor)

· In the category of “PREVIOUSLY PUBLISHED SHORT-FORM FICTION” the winner is “Slow Bullets” by Alastair Reynolds (published by Tachyon Publications)

· In the category of “PREVIOUSLY PUBLISHED NONFICTION” the winner is Welcome to Mars: Making a Home on the Red Planet by Buzz Aldrin and Marianne Dyson (published by National Geographic)

· In the category of “ORIGINAL FICTION” the winner is “The Quest for New Cydonia” by Russell Hemmell

· In the category of “ORIGINAL NON-FICTION” the winner is “Microbots—The Seeds of Interstellar Civilization” by Robert Buckalew

· In the category of “ORIGINAL COLLEGE WRITING” the winner is “A Kingdom of Ends” by Ryan Burgess

Award category finalists are as listed below:

“Previously Published Long-Form Fiction”(40,000 words or more):

· The Long Way to a Small, Angry Planet by Becky Chambers (Harper Voyager)

· Dark Orbitby Carolyn Ives Gilman (Tor)

· Sevenevesby Neal Stephenson (HarperCollins)

· The Three-Body Problemby Cixin Liu, Translated by Ken Liu (Tor)

· Arkwrightby Allen Steele (Tor)

“Previously Published Short-Form Fiction”(between 1,000 and 40,000 words):

· “Slow Bullets” by Alastair Reynolds (Tachyon Publications)

· “The Long Vigil” by Rhett C. Bruno (Perihelion)

· “The Citadel of Weeping Pearls” by Aliette de Bodard (Asimov’s Science Fiction)

· “Wavefronts of History and Memory” by David D. Levine (Analog Science Fiction and Fact)

· “The Four Thousand, The Eight Hundred” by Greg Egan (Subterranean Press)

· “Whom He May Devour” by Alex Shvartsman (Nautilus)

· “Love and Relativity” by Stewart C. Baker (Flash Fiction Online)

“Previously Published Nonfiction”(between 1,000 and 40,000 words):

· “A Terrestrial Planet Candidate in a Temperate Orbit Around Proxima” by Guillem Anglada-Escude, et al. (Nature)

· “A Science Critique of Auroraby Kim Stanley Robinson” by Stephen Baxter, James Benford, and Joseph Miller (Centauri Dreams)

· Welcome to Mars: Making a Home on the Red Planetby Buzz Aldrin and Marianne Dyson (National Geographic)

· “Let’s All Go to Mars” by John Lanchester (London Review of Books)

· “Our Worldship Broke!” by Jim Beall (Baen Books)

“Original Fiction”(1,000-5,000 words):

· “The Quest for New Cydonia” by Russell Hemmell

· “Luminosity” by Adeene Denton

· “Mission” by Yoshifumi Kakiuchi

· “Envoy” by K. G. Jewell

· “Sleeping Westward” by Lorraine Schein

“Original Non-Fiction”(1,000-5,000 words):

· “Motivatingly Plausible Ways to Reach the Stars” by James Blodgett

· “Microbots—The Seeds of Interstellar Civilization” by Robert Buckalew

· “An Anthropic Program for the Long-Term Survival of Humankind” by Roberto Paura

· “Terraforming Planets, Geoengineering Earth” by James Fleming

“Original College Writing”(1,000-5,000 words):

· “A Kingdom of Ends” by Ryan Burgess

· “Ethics in Space” by Greg Becker

In addition, the following works were noted as inclusion for honorable mention by our selection committee although they were not finalists in any category:

Honorable Mention

· Interstella Cinderellaby Deborah Underwood (Chronicle Books)

· Protos Mandateby Nick Kanas (Springer)

· The Arkby Patrick S. Tomlinson (Angry Robot Books)

· The Destructivesby Matthew de Abaitua (Angry Robot Books)

· “Exquisite Banality of Space” by Leslie J. Anderson, published in Uncanny Magazine

· “Spacefarer’s Creed” by Matt Noble (poetry)

· “Dispatchers from Interstellar Race Relations Log” by Janel Cloyd (poetry)

For more information about award criteria, nomination and submission, visit http://100yss.org/initiatives/canopusaward.

VIDEO ANNOUCEMENT

https://www.facebook.com/100YearStarship/

- ### -

ABOUT100YEARSTARSHIP™

100YSSispartofthe DorothyJemisonFoundationforExcellence.Formoreinformation,visitwww.100yss.org.

Find us on social media:

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Twitter: @100YSS

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mitchbattros · 6 years ago

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Gravitational Forces In Protoplanetary Disks May Push Super-Earths Close To Their Stars

The galaxy is littered with planetary systems vastly different from ours. In the solar system, the planet closest to the Sun -- Mercury, with an orbit of 88 days -- is also the smallest. But NASA's Kepler spacecraft has discovered thousands of systems full of very large planets -- called super-Earths -- in very small orbits that zip around their host star several times every 10 days.

Now, researchers may have a better understanding how such planets formed. A team of Penn State-led astronomers found that as planets form out of the chaotic churn of gravitational, hydrodynamic -- or, drag -- and magnetic forces and collisions within the dusty, gaseous protoplanetary disk that surrounds a star as a planetary system starts to form, the orbits of these planets eventually get in synch, causing them to slide -- follow the leader-style -- toward the star. The team's computer simulations result in planetary systems with properties that match up with those of actual planetary systems observed by the Kepler space telescope of solar systems. Both simulations and observations show large, rocky super-Earths orbiting very close to their host stars, according to Daniel Carrera, assistant research professor of astronomy at Penn State's Eberly College of Science. He said the simulation is a step toward understanding why super-Earths gather so close to their host stars. The simulations may also shed light on why super-Earths are often located so close to their host star where there doesn't seem to be enough solid material in the protoplanetary disk to form a planet, let alone a big planet, according to the researchers, who report their findings in the Monthly Notices of the Royal Astronomical Society. "When stars are very young, they are surrounded by a disc that is mostly gas with some dust -- and that dust grows into the planets, like the Earth and these super-Earths," said Carrera. "But the particular puzzle for us is that this disc doesn't go the all way to the star -- there's a cavity there. And yet we see these planets closer to the star than the edge of that disc." The astronomers' computer simulation shows that, over time, the planets' and disk's gravitational forces lock the planets into synchronized orbits -- resonance -- with each other. The planets then begin to migrate in unison, with some moving closer to the edge of the disk. The combination of the gas disk affecting the outer planets and the gravitational interactions among the outer and inner planets can continue to push the inner planets very closer to the star, even interior to the edge of the disk. "With the first discoveries of Jupiter-size exoplanets orbiting close to their host star, astronomers were inspired to develop multiple models for how such planets could form, including chaotic interactions in multiple planet systems, tidal effects and migration through the gas disk," said Eric Ford, professor of astronomy and astrophysics, director of Penn State's Center for Exoplanets and Habitable Worlds and Institute for CyberScience (ICS) faculty co-hire. "However, these models did not predict the more recent discoveries of super-Earth-size planets orbiting so close to their host star. Some astronomers had suggested that such planets must have formed very near their current locations. Our work is important because it demonstrates how short-period super-Earth-size planets could have formed and migrated to their current locations thanks to the complex interactions of multiple planet systems." Carrera said more work remains to confirm that the theory is correct. "We've shown that it's possible for planets to get that close to a star in this simulation, but it doesn't mean that it's the only way that the universe chose to make them," said Carrera. "Someone might come up with a different idea of a way to get the planets that close to a star. And, so, the next step is to test the idea, revise it, make predictions that you can test against observations." Future research may also explore why our super-Earthless solar system is different from most other solar systems, Carrera added. "Super-Earths in very close orbits are by far the most common type of exoplanet that we observe, and yet they don't exist in our own solar system and that makes us wonder why," said Carrera. According to the researchers, the best published estimates suggest that about 30 percent of solar-like stars have some planets close to the host star than the Earth is to the Sun. However, they note that additional planets are could go undetected, especially small planets far from their star. Andre Izidoro, researcher, Sao Paulo State University -- UNESP, worked with Carrera and Ford on the study, that began thanks to collaborations formed as part of NASA's Nexus for Exoplanet Systems Science. Computations for this research were performed on the Penn State's Institute for CyberScience Advanced CyberInfrastructure (ICS-ACI) and the CyberLAMP computer cluster. The National Science Foundation, NASA and Penn State's Center for Exoplanets and Habitable Worlds supported this work. Read the full article

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night-lights-2019-blog · 6 years ago

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In the search for habitable worlds beyond our solar system, the detection of liquid water at the surface of a planet is one of the most sought-after discoveries for today’s astrobiologists. Methods to detect surface water have been proposed, including rotational mapping and specular reflection (or the glint of light reflecting off an extrasolar ocean). However, both of these techniques could produce false positives.

A team of researchers recently used a simulation of Earth to address this issue and to help improve the robustness these extrasolar ocean detection methods. Their work takes into account the affect of clouds that cause forward-scattering of light, and landmasses that would cause the glint off of an ocean to ‘blink’ as the planet rotates. The results indicates that it could be possible to detect glint measurements for ‘between 1 and 10 habitable zone exoplanets orbiting the nearest G, K, and M dwarfs.’ The necessary observations would require the use of a ‘space-based, high-contrast, direct-imaging telescope with a diameter between 6 and 15 m.’

The study, “Detecting Ocean Glint on Exoplanets Using Multiphase Mapping,” was published in The Astronomical Journal. The work was supported by the Nexus for Exoplanet System Science (NExSS). NExSS is a NASA research coordination network supported in part by the NASA Astrobiology Program. This program element is shared between NASA’s Planetary Science Division (PSD) and the Astrophysics Division.

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for-all-mankind · 8 years ago

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Exoplanets seen orbiting alien sun for first time.

For the first time in history, a telescope has directly observed the orbital motion of planets in a solar system other than our own.

Using the W.M. Keck observatory in Hawaii, Dr. Christian Marois of Canada’s Herzberg Institute of Astrophysics photographed the star HR 8799 periodically between 2009 and 2015. Jason Wang of UC Berkeley combined the eight images into an animation showing the relative motion of the star’s four planets. The planet closest to the star has an orbital period of 40 Earth years, while the furthest away is over 400. Three of the four planets were photographed directly in 2008, and were among the first exoplanets to be directly imaged. Because exoplanets are so far away from our solar system, light from their parent star is too bright to separate them in telescopic observations. Only recently has technology been developed to block out the parent star’s light. UC Berkeley is part of the Nexus for Exoplanet System Science, or NExSS, a NASA-sponsored group which aims to stimulate academic science into exoplanets and exoplanetary solar systems. The HR 8799 system is over 129 light years away.

More information here. P/C: UC Berkeley.

#UC Berkley #NASA #exoplanets #planetary science #NExSS #science #astrophysics

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scifigeneration · 5 years ago

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Accelerating exoplanet discovery using chemical fingerprints of stars

by Natalie Hinkel

Planets form from a disc of dust orbiting a star. Mopic/Shutterstock.com

Stars are born when huge clouds of dust and gas collapse in on themselves and ignite. These clouds are made up of raw elements, like oxygen and titanium, and each cloud has a unique composition that imprints on the star. And within the stellar afterbirth – from the material that didn’t find its way into the star – planets are formed.

Finding planets orbiting distant stars, or exoplanets, is difficult. There are tried and true methods that involve using large telescopes to detect these tiny objects. But I’ve developed a faster and more powerful strategy for planet hunting that is based on the chemistry of the star. I am a planetary astrophysicist. Admittedly, this is a title that I made up because I wanted something that actually described what I do. I study the elements within stars, their patterns, and how they are connected to planets.

I created an enormous database of stars and their elemental compositions. Some of those stars have planets orbiting them; others don’t. When a star has an orbiting planet, it could be the smaller rocky type, a large gas one, or both. However, not every star can have a giant Jupiter-sized planets – since these planets require a huge amount of elements and materials to form.

Together with a small team of researchers from Arizona State University, University of California, Riverside, Vanderbilt University and New York University, I used software that searches for complex patterns within stellar data to figure out which stars are likely to have planets orbiting them based only on the star’s chemical composition.

Now, instead of looking through huge all-sky telescope surveys hoping to find a signature of a planet, my team can fast-track the discovery and characterization of planets by analyzing the composition of their host stars. Of the 4,200 stars that we analyzed, we found that approximately 360 stars have a greater than 90% chance of hosting a giant planet. Now we are working to get time on a telescope to test our predictions.

Stars and planets are chemically linked to one another, since they both form within the same molecular cloud. The raw ingredients within the planet ultimately creates an environment that’s ‘alive’ and conducive to life – or not. NASA/JPL-Caltech

The Hypatia Catalog and its elements

The algorithm we developed uses the chemical composition of stars that we know have orbiting giant planets to determine which combination of elements – or chemical fingerprint – is common to stars that host planets. My team then used this algorithm to look at the chemistry of stars not known to have planets to provide a prediction score that a star is likely to host a planet.

This is the logo for the Hypatia Catalog showing an artist depiction of Hypatia. Some of the most important elements in stars are listed along the outside. Nahks Tr'Ehnl, CC BY-SA

Light shines from the interior of a star and is absorbed by atoms in its upper layer, creating a stellar spectra. The absorbed wavelengths reveal what type of elements from the periodic table are present. Using a technique called spectroscopy, scientists are able to measure the light from the star and measure the amount, or abundance, of those elements. I compiled the largest catalog of elements in nearby stars in the Hypatia Catalog. I named it to honor one of the first known female astronomers who was a powerhouse in 400 A.D.

I use the Hypatia Catalog to understand planets from a more chemical or compositional perspective. Each star is made up of different combinations and quantities of elements, which is reflected in the planets orbiting the star. There can be a huge variety in the chemical composition of planets from their interiors to their surfaces.

Physically detecting exoplanets

There are two primary techniques for finding or detecting exoplanets.

The first is the “radial velocity” technique, which detects when a star wobbles in the presence of a planet with a strong gravitational force.

Another strategy is to look for a “blip” in the light a star emits, which happens when a planet moves in front of the star (with respect to the Earth) and actually dims the stellar light. Both of these methods look for ways that the planet influences the star. However, it’s difficult to detect planets because they are so small compared with their star – it would be like trying to observe a person being influenced by a raindrop.

The radial velocity and “blip” methods look at the physical relationship between a star and a planet. These are important because they determine the temperature, orbit and dynamics that exoplanet scientists use to define whether a planet may be habitable. However, none of these detection methods take into account what the star and planet are made of. And yet, understanding the composition of the planet is vital to predicting whether it is habitable.

An artist’s impression of how common planets are around the stars in the Milky Way. The planets, their orbits and their host stars are all vastly magnified. ESO/M. Kornmesser, CC BY-ND

Planetary composition is key to habitability

The planet Earth is “alive” – it moves and shifts in a complex way. The surface conditions, like temperature and weather, are maintained by relying on the movement of the continents, for example by plate tectonics. The cycling of different elements or molecules, like the oxygen-carbon dioxide cycle, helps organisms breathe. In order for exoplanets to truly be habitable for life, basic elements must be present within the planet to make sure that these key processes happen.

We exoplanetary scientists don’t currently have the technology to directly observe the surface or interior of a planet outside of our Solar System. This is partially because planets are so small compared to their star, so we’d need high-powered telescopes. It is also because planets don’t shine or emit their own light.

Therefore, my colleagues and I use the stellar composition as a proxy for the planet’s makeup. The algorithm that we developed is a unique one, because it looks at the elemental link between a star and its planet from the very beginning. This makes the approximately 360 likely giant planet host stars we found even more remarkable, because they were identified by the chemical fingerprint.

As part of this research published in The Astrophysical Journal, we studied a variety of different elements, up to 16 at a time. We wanted to see how those elements influenced each other and which were the most important for planet detection and possible formation.

We found that carbon, oxygen, sodium and iron were the most important elements when predicting that a star had a giant planet. Carbon, oxygen and iron are all very important elements when it comes to building rocky and or gas planets. However, we were surprised to discover that sodium also seemed to be a critical ingredient of stars that form giant planets. Sodium is not considered to be a major planet-forming element within the Solar System.

For practical reasons we didn’t use the algorithm to look at Earth-like planets. Rather we focused our study, and trained our algorithm, on big gaseous planets where humans couldn’t survive. Most of the exoplanets that astronomers have discovered to date have sizes similar to Neptune or Jupiter because they are easier to detect.

However, as new missions like TESS and CHEOPS discover smaller, Earth-sized planets, we will have more data with which to train the algorithm to look for rocky planets like Earth.

About The Author:

This article is republished from our content partners at The Conversation under a Creative Commons license.

#science #astronomy #space #science news #NASA #exoplanets #TESS #space telescopes #CHEOPS

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spaceexp · 6 years ago

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Will We Know Life When We See It? NASA-led Group Takes Stock of the Science

Exoplanets - Exobiology logo. June 25, 2018 In the last decade we have discovered thousands of planets outside our solar system and have learned that rocky, temperate worlds are numerous in our galaxy. The next step will involve asking even bigger questions. Could some of these planets host life? And if so, will we be able to recognize life elsewhere if we see it?

Image above: Artist's conception of what life could look like on the surface of a distant planet. Image Credit: NASA. A group of leading researchers in astronomy, biology and geology have come together under NASA’s Nexus for Exoplanet System Science, or NExSS, to take stock of our knowledge in the search for life on distant planets and to lay the groundwork for moving the related sciences forward. “We’re moving from theorizing about life elsewhere in our galaxy to a robust science that will eventually give us the answer we seek to that profound question: Are we alone?” said Martin Still, NASA exoplanet scientist at Headquarters, Washington. In a set of five review papers published last week in the scientific journal Astrobiology, NExSS scientists took an inventory of the most promising signs of life, called biosignatures. They considered how to interpret the presence of biosignatures, should we detect them on distant worlds. A primary concern is ensuring the science is strong enough to distinguish a living world from a barren planet masquerading as one. The assessment comes as a new generation of space and ground-based telescopes are in development. NASA’s James Webb Space Telescope will characterize the atmospheres of some of the first small, rocky planets. Other observatories— such as the Giant Magellan Telescope and the Extremely Large Telescope, both in Chile— are planning to carry sophisticated instruments capable of detecting the first biosignatures on faraway worlds.

Image above: Life can leave "fingerprints" of its presence in the atmosphere and on the surface of a planet. These potential signs of life, or biosignatures, can be detected with telescopes. Image Credits: NASA/Aaron Gronstal. Through their work with NExSS, scientists aim to identify the instruments needed to detect potential life for future NASA flagship missions. The detection of atmospheric signatures of a few potentially habitable planets may possibly come before 2030, although whether the planets are truly habitable or have life will require more in-depth study. Since we won’t be able to visit distant planets and collect samples anytime soon, the light that a telescope observes will be all we have in the search for life outside our solar system. Telescopes can examine the light reflecting off a distant world to show us the kinds of gases in the atmosphere and their "seasonal" variations, as well as colors like green that could indicate life. These kinds of biosignatures can all be seen on our fertile Earth from space, but the new worlds we examine will differ significantly. For example, many of the promising planets we have found are around cooler stars, which emit light in the infrared spectrum, rather than our sun’s high emissions of visible-light.

Image above: Abiotic processes can fool us into thinking a barren planet is alive. Rather than measuring a single characteristic of a planet, we should consider a suite of traits to build the case for life. Image Credits: NASA/Aaron Gronstal. “What does a living planet look like?” said Mary Parenteau, an astrobiologist and microbiologist at NASA’s Ames Research Center in Silicon Valley and a co-author. “We have to be open to the possibility that life may arise in many contexts in a galaxy with so many diverse worlds — perhaps with purple-colored life instead of the familiar green-dominated life forms on Earth, for example. That’s why we are considering a broad range of biosignatures.” The scientists assert that oxygen — the gas produced by photosynthetic organisms on Earth — remains the most promising biosignature of life elsewhere, but it is not foolproof. Abiotic processes on a planet could also generate oxygen. Conversely, a planet lacking detectable levels of oxygen could still be alive — which was exactly the case of Earth before the global accumulation of oxygen in the atmosphere. “On early Earth, we wouldn’t be able to see oxygen, despite abundant life,” said Victoria Meadows, an astronomer at the University of Washington in Seattle and lead author of one of the papers. “Oxygen teaches us that seeing, or not seeing, a single biosignature is insufficient evidence for or against life — overall context matters.”

Image above: Since the data we collect from planets will be limited, scientists will quantify how likely a planet has life based on all the available evidence. Follow-up observations are required for confirmation. Image Credits: NASA/Aaron Gronstal. Rather than measuring a single characteristic, the NExSS scientists argue that we should be looking at a suite of traits. A planet must show itself capable of supporting life through its features, and those of its parent star. The NExSS scientists will create a framework that can quantify how likely it is that a planet has life, based on all the available evidence. With the observation of many planets, scientists may begin to more broadly classify the “living worlds” that show common characteristics of life, versus the “non-living worlds.” “We won’t have a ‘yes’ or ‘no’ answer to finding life elsewhere,” said Shawn Domagal-Goldman, an astrobiologist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland and a co-author. “What we will have is a high level of confidence that a planet appears alive for reasons that can only be explained by the presence of life.” Related links: Nexus for Exoplanet System Science (NExSS): https://nexss.info/ Five review papers: https://www.liebertpub.com/toc/ast/18/6 Astrobiology: https://www.nasa.gov/content/the-search-for-life Exoplanets: https://www.nasa.gov/content/the-search-for-life Images (mentioned), Text, Credits: NASA/Sarah Loff/Felicia Chou. Greetings, Orbiter.ch Full article

#space #science

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hellarificscience · 8 years ago

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Four Planets Orbiting Star HR 8799: a gif seven years in the making

Tasked with figuring out if life could possibly exist outside the solar system, NASA created the Nexus for Exoplanet System Science (NExSS) to “better locate and study distant star systems that hold hope of harboring living inhabitants”.

Just recently (Feb 2017), NExSS released an extraordinary time-lapse video - using images taken over seven years from the Keck Observatory in Hawaii - as part of a collaboration with UC Berkeley and Herzberg Astrophysics.

The film, quite simply titled “Four Planets Orbiting Star HR 8799″, features four exoplanets as they partially circle their parent star HR 8799. The events that we see unfolding are taking place a mind blowing 130 light years away.

The planets appear as “white dots” while the parent star was purposefully “blacked out” to create a truly unique perspective on an otherwise ubiquitous astronomical event.

The authors say that the central star HR 8799 is “slightly larger and more massive than our Sun, while each of the planets is thought to be a few times the mass of Jupiter”. They are now continuing research on whether any of these planets or even the moons of these planets have the potential to harbor any form of life.

Who knows, aliens on one of these planets could have a very similar video of earth circling our sun and be wondering the very same thing...

Video Credit & CC BY License:

J. Wang (UC Berkeley) & C. Marois (Herzberg Astrophysics), NExSS (NASA), Keck Obs.

#science #astronomy #cool

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sciencespies · 4 years ago

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The cost of visiting Earth may be too astronomical for aliens

https://sciencespies.com/space/the-cost-of-visiting-earth-may-be-too-astronomical-for-aliens/

The cost of visiting Earth may be too astronomical for aliens

In 1950, Italian-American physicist Enrico Fermi sat down to lunch with some of his colleagues at the Los Alamos National Laboratory, where he had worked five years prior as part of the Manhattan Project.

According to various accounts, the conversation turned to aliens and the recent spate of UFOs. Into this, Fermi issued a statement that would go down in the annals of history: “Where is everybody?”

This became the basis of the Fermi Paradox, which refers to the disparity between high probability estimates for the existence of extraterrestrial intelligence (ETI) and the apparent lack of evidence.

Since Fermi’s time, there have been several proposed resolutions to his question, which includes the very real possibility that interstellar colonization follows the basic rule of Percolation Theory.

One of the key assumptions behind the Fermi Paradox is that given the abundance of planets and the age of the Universe, an advanced exo-civilization should have colonized a significant portion of our galaxy by now.

This is certainly not without merit, considering that within the Milky Way galaxy alone (which is over 13.5 billion years old), there are an estimated 100 to 400 billion stars.

Another key assumption is that intelligent species will be motivated to colonize other star systems as part of some natural drive to explore and extend the reach of their civilization.

Last, but certainly not least, it assumes that interstellar space travel would be feasible and even practical for an advanced exo-civilization.

But this, in turn, comes down to the assumption that technological advances will provide solutions to the single-greatest challenge of interstellar travel.

In short, the amount of energy it would take for a spacecraft to travel from one star to another is prohibitively large, especially where large, crewed spacecraft would be concerned.

Relativity is a harsh mistress

In 1905, Einstein published his seminal paper in which he advanced his Special Theory of Relativity. This was Einstein’s attempt to reconcile Newton’s Laws of Motion with Maxwell’s Equations of electromagnetism in order to explain the behavior of light.

This theory essentially states that the speed of light (in addition to being constant) is an absolute limit beyond which objects cannot travel.

This is summarized by the famous equation, E=mc2, which is otherwise known as the “mass-energy equivalence.” Put simply, this formula describes the energy (E) of a particle in its rest frame as the product of mass (m) with the speed of light squared (c2) – approx. 300,000 km/s; 186,000 mi/s. A consequence of this is that as an object approaches the speed of light, its mass invariably increases.

Therefore, for an object to reach the speed of light, an infinite amount of energy would have to be expended accelerating it. Once c was achieved, the mass of the object would also become infinite.

In short, achieving the speed of light is impossible, never mind exceeding it. So barring some tremendous revolution in our understanding of physics, a Faster-Than-Light (FTL) propulsion system can never exist.

Such is the consequence of living in a relativistic Universe, where traveling at even a fraction of the speed of light requires tremendous amounts of energy.

And while some very interesting and innovative ideas have been produced over the years by physicists and engineers who want to see interstellar travel become a reality, none of the crewed concepts are what you might call “cost-effective.”

A Matter of Principle

This raises a very important philosophical question that is related to the Fermi Paradox and the existence of ETIs. This is none other than the Copernican Principle, named in honor of famed astronomer Nicolaus Copernicus.

To break it down, this principle is an extension of Copernicus’ argument about the Earth, how it was not in a unique and privileged position to view the Universe.

Extended to the cosmological realm, the principle basically asserts that when considering the possibility of intelligent life, one should not assume that Earth (or humanity) is unique.

Similarly, this principle holds that the Universe as we see it today is representative of the norm – aka, that it is in a state of equilibrium.

The opposing view that humanity is in a unique and privileged position to observe the Universe is what is known as the Anthropic Principle.

In a nutshell, this principle states that the very act of observing the Universe for signs of life and intelligence requires that the laws that govern it be conducive to life and intelligence.

If we accept the Copernican Principle as a guiding principle, we are forced to concede that any intelligent species would face the same challenges with interstellar flight as we do.

And since we do not foresee a way around these, barring major a breakthrough in our understanding of physics, perhaps no other species has found one either.

Could this be the reason for the “Great Silence”?

Origin

The notion that distance and time may be a factor (in relation to the Fermi Paradox) has received quite a bit of consideration over time.

Carl Sagan and William I. Newman suggested in their 1981 study, “Galactic civilizations: Population dynamics and interstellar diffusion,” that signals and probes by ETIs may simply not have reached Earth yet. This was met with criticism by other scientists who argued that it contradicted the Copernican Principle.

By Sagan and Newman’s own estimates, the time it would take for an ETI to have explored the entire galaxy is equal to or less than the age of our galaxy itself (13.5 billion years). If an exo-civilization’s probes or signals have not reached us yet, this would imply that sentient life started to emerge in the more recent past.

In other words, the galaxy is in a state of disequilibrium, moving from a state of being uninhabited to inhabited.

However, it was Geoffrey A. Landis who made what is perhaps the most compelling argument about the limits imposed by the laws of physics.

In his 1993 paper, “The Fermi paradox: an approach based on percolation theory,” he argued that as a consequence of Relativity, an exo-civilization would only be able to expand so far throughout the galaxy.

Central to Landis’ argument was the mathematical and physics statistics concept known as “percolation theory,” which describes how a network behaves when nodes or links are removed.

In accordance with this theory, when enough of the network’s links are removed, it will break down into smaller connected clusters.

According to Landis, this same process is useful in describing what happens to people engaged in migration.

In short, Landis proposed that in a galaxy where intelligent life is statistically likely, there will not be a “uniformity of motive” among extraterrestrial civilizations. Instead, his model assumes a wide variety of motives, with some choosing to venture out and colonize while others choose to “stay at home.”

As he explained it:

“Since it is possible, given a large enough number of extraterrestrial civilizations, one or more would have certainly undertaken to do so, possibly for motives unknowable to us. Colonization will take an extremely long time, and will be very expensive.

“It is quite reasonable to suppose that not all civilizations will be interested in making such a large expenditure for a pay off far in the future. Human society consists of a mixture of cultures which explore and colonize, some times over extremely large distances, and cultures which have no interest in doing so.”

To summarize, an advanced species would not colonize the galaxy rapidly or consistently. Instead, it would “percolate” outwards to a finite distance, where increasing costs and the lag time between communications imposed limits and colonies evolved their own cultures.

Thus, colonization wouldn’t be uniform but would happen in clusters with large areas remaining uncolonized at any given time.

A similar argument was made in 2019 by Adam Frank and a team of exoplanet researchers from NASA’s Nexus for Exoplanetary Systems Science (NExSS).

In a study titled “The Fermi Paradox and the Aurora Effect: Exo-civilization Settlement, Expansion, and Steady States,” they argued that settlement of the galaxy would also occur in clusters because not all potentially-habitable planets would be hospitable for a colonizing species.

Of course, Landis’ model contains some inherent assumptions of its own, which he laid out beforehand.

First, there was the assumption that interstellar travel is difficult due to the laws of physics and that there is a maximum distance over which colonies can be directly established. Hence, a civilization will only colonize within a reasonable distance from its home, beyond which secondary colonization will occur later.

Second, Landis also makes the assumption that the parent civilization will have a weak grasp over any colonies it creates, and the time needed for these to develop their own colonization capability will be very long. Hence, any colony established will develop its own culture over time, and its people will have a sense of self and identity distinct from that of the parent civilization.

As we explored in a previous article, it would take between 1,000 and 81,000 years to reach Proxima Centauri (4.24 light-years away) using current technology.

While there are concepts that would allow for relativistic travel (a fraction of the speed of light), the travel time would still be anywhere from a few decades to over a century. What’s more, the cost would be extremely prohibitive (more on that below).

But getting colonists to another star system is just the beginning.

Once they have settled a nearby habitable planet (and not all died off) and have the infrastructure for interstellar communications, it would still take eight-and-a-half years to send a message to Earth and receive an answer. That’s simply not practical for any civilization hoping to maintain centralized control or cultural hegemony over its colonies.

Space is expensive!

To put things in perspective, consider the costs associated with humanity’s own history of space exploration. Sending astronauts to the Moon as part of the Apollo Program between 1961 and 1973 cost a hefty US$25.4 billion, which works out to about US$150 billion today (when adjusted for inflation).

But Apollo did not occur in a vacuum, and first required Project Mercury and Project Gemini as stepping stones.

These two programs, which put the first American astronauts in orbit and developed the necessary expertise for getting to the Moon, respectively ran about US$2.3 billion and US$10 billion (when adjusted).

Add them all up, and you get a grand total of around US$163 billion spent from 1958 to 1972.

By comparison, Project Artemis, which will return astronauts to the Moon for the first time since 1972, will cost US$35 billion over just the next four years!

That doesn’t include the costs of getting all the various components to this stage in the game, like the development of the SLS thus far, the Orion space capsule, and research into the Lunar Gateway, human landing systems (HLS), and robotic missions.

That’s a lot of money just to get to Earth’s only satellite. But that’s nothing compared to the costs of interstellar missions!

Going interstellar?

Since the dawn of the Space Age, many theoretical proposals have been made for sending spacecraft to the nearest stars.

At the heart of each and every one of these proposals was the same concern: can we reach the nearest stars in our lifetimes?

In order to meet this challenge, scientists contemplated a number of advanced propulsion strategies that would be capable of pushing spacecraft to relativistic speeds.

Of these, the most straightforward was definitely Project Orion (1958 to 1963), which would rely on a method known as Nuclear Pulse Propulsion (NPP).

Led by Ted Taylor of General Atomics and physicist Freeman Dyson from the Institute for Advanced Study at Princeton University, this project envisioned a massive starship that would use the explosive force generated by nuclear warheads to generate thrust.

These warheads would be released behind the spacecraft and detonated, creating nuclear pulses. These would be absorbed by a rear-mounted pressure plate (aka, “pusher”) that translate the explosive force into forward momentum.

Though inelegant, the system was brutally simple and effective, and could theoretically achieve speeds of up to 5 percent the speed of light (5.4×107km/hr, or 0.05c).

Alas, the cost. According to estimates produced by Dyson in 1968, an Orion spacecraft would weight between 400,000 and 4,000,000 metric tons.

Dyson’s most conservative estimates also placed the cost of building such a craft at US$367 billion (US$2.75 trillion when adjusted for inflation). That’s about 78 percent of the US government’s annual revenue for 2019, and 10 percent of the country’s GDP.

Another idea was to build rockets that rely on thermonuclear reactions to generate thrust.

Specifically, the concept of Fusion Propulsion was investigated by the British Interplanetary Society between 1973 and 1978 as part of a feasibility study known as Project Daedalus.

The resulting design called for a two-stage spacecraft that would generate thrust by fusing pellets of a deuterium/helium-3 in a reaction chamber using electron lasers.

This would create a high-energy plasma that would then be converted to thrust by a magnetic nozzle.

The first stage of the spacecraft would operate for just over 2 years and accelerate the spacecraft to 7.1 percent the speed of light (0.071c). This stage would then be jettisoned and the second stage would take over and accelerate the spacecraft up to about 12 percent of light speed (0.12c) over the course of 1.8 years.

The second-stage engine would then be shut down, and the ship would enter into a 46-year cruise period.

According to the Project’s estimates, the mission would take 50 years to reach Barnard’s Star (less than 6 light-years away). Adjusted for Proxima Centauri, the same craft could make the trip in 36 years.

But in addition to technological barriers identified by the Project, there was also the sheer costs involved.

Even by the modest standard of an uncrewed concept, a fully-fueled Daedalus would weigh as much as 60,000 metric tons […]. Adjust to 2020, the price tag for a fully-assembled Daedalus would cost close to US$6 trillion. Icarus Interstellar, an international organization of volunteer citizen scientists (founded in 2009), has since attempted to revitalize the concept with Project Icarus.

Another bold and daring idea is Antimatter Propulsion, which would rely on the annihilation of matter and antimatter (hydrogen and antihydrogen particles).

This reaction unleashed as much energy as a thermonuclear detonation, as well as a shower of subatomic particles (pions and muons).

These particles, which would then travel at one-third the speed of light, are channeled by a magnetic nozzle to generate thrust.

Unfortunately, the cost of producing even a single gram of antimatter fuel is estimated to be around US$1 trillion.

According to a report by Robert Frisbee of NASA’s Advanced Propulsion Technology Group (NASA Eagleworks), a two-stage antimatter rocket would need over 815,000 metric tons (900,000 US tons) of fuel to make the journey to Proxima Centauri in approximately 40 years.

A more optimistic report by Dr. Darrel Smith & Jonathan Webby of the Embry-Riddle Aeronautical University states that a spacecraft weighing 400 metric tons (441 US tons) and 170 metric tons (187 US tons) of antimatter fuel could reach 0.5 the speed of light.

At this rate, the craft could reach Proxima Centauri in a little over 8 years, but there’s no cost-effective way to do this and no guarantees there ever will be.

In all cases, propellant makes up a large fraction of these concept’s overall mass. To address this, variations have been proposed that could generate their own propellant.

In the case of fusion rockets, there’s the Bussard Ramjet, which uses an enormous electromagnetic funnel to “scoop” hydrogen from the interstellar medium and magnetic fields to compress it to the point that fusion occurs.

Similarly, there’s the Vacuum to Antimatter Rocket Interstellar Explorer System (VARIES), which also creates its own fuel out of the interstellar medium. Proposed by Richard Obousy of Icarus Interstellar, a VARIES ship would rely on large lasers (powered by enormous solar arrays) that would create particles of antimatter when fired at empty space.

Alas, neither of these ideas are possible using current technology, nor are they within the realm of cost-effectiveness (not by a long shot).

Under the circumstances, and barring several major technological developments that would reduce the associated costs, it would be fair to say that any idea for interstellar crewed missions is simply impractical.

Sending probes to other stars within our lifetimes is still within the realm of possibility, especially those that rely on Directed-Energy Propulsion (DEP).

As proposals like Breakthrough Starshot or Project Dragonfly show, these sails could be accelerated to relativistic speeds and have all the necessary hardware to gather pictures and basic data on any orbiting exoplanets.

However, such probes are a potentially-reliable and cost-effective means of interstellar exploration, not colonization.

What’s more, the time-lag involved in interstellar communications would still place constraints on how far these probes could explore while still reporting back to Earth.

Therefore, an exo-civilization is not likely to send probes very far beyond the boundaries of its territory.

Criticisms

A possible criticism of percolation theory is that it allows for many scenarios and interpretations that would permit contact to have happened at this point.

If we assume that an intelligent species would similarly take 4.5 billion years to emerge (the time between Earth’s formation and modern humans), and consider that our galaxy has been around for 13.5 billion years, that still leaves a 9 billion years window.

For 9 billion years, multiple civilizations could have come and gone, and while no one species could have colonized the entire galaxy, it’s hard to imagine that this activity would have gone unnoticed.

Under the circumstances, one may be forced to conclude that in addition to their being limits to how a civilization can reach that there are other limiting factors at work here (Great Filter, anyone?)

However, it is important to remind ourselves that no proposed resolution to the Fermi Paradox is without its share of holes.

Also, expecting a theory or theorist to have all the answers to a subject as complex (yet data-poor) as the existence of extraterrestrials is about as unrealistic as expecting consistency in the behavior of ETIs themselves!

Overall, this hypothesis is highly useful because of the way it breaks down many of the assumptions inherent to “Fact A.”

It also presents an entirely logical starting point for answering the fundamental question. Why haven’t we heard from any ETIs? Because it’s unrealistic to conclude that they should have colonized the better part of the galaxy by now, especially when the laws of physics (as we know them) preclude such a thing.

This article was originally published by Universe Today. Read the original article.

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