#Planetary Formation

[thecurioustale]

Worldbuilding: Something I Learned About Planetary Surface Gravity

Last year (hehe; it's always fun to say that at the start of a new year; actual time about 4 months ago), I made a strange discovery!

I won't slow-roll you. Here's the bottom line: In reality, i.e. based on observational data, there appears to be a plateau of surface gravity for planets up to about 500 times more massive than Earth. Most planets between 1 Earth mass and ~500 Earth masses have a surface gravity that is close to our own, i.e. 1 g. So if you're worldbuilding, and need a planet with a surface gravity that is more than a few percentage points higher than Earth's, be careful.

All right, on to the story!

I had need of such a planet for Galaxy Federal. About 125% percent or so, i.e. 1.25 g. And it was in the back of my mind that Neptunian planets often have a "surface" gravity similar to that of Earth's. "Okay," I figured, "that's probably because their giant atmospheres reduce the average planetary density. On a rocky world that wouldn't be an issue. But I'd better check to be safe."

Oh, it is always a good idea to check!

I found a paper which was reporting the plateau that I mentioned in the TL;DR. Here's what it looks like:

Gravity vs mass for Solar System bodies and exoplanets. Ballesteros, Fernando & Luque, Bartolo. (2016). Walking on Exoplanets: Is Star Wars Right?. Astrobiology. 16. 10.1089/ast.2016.1475.

What they found is that Super Earths, i.e. rocky planets with a mass greater than Earth's, did not exhibit the increase in surface gravity seen in smaller celestial bodies. There is this "plateau" where increases in planetary mass and radius are such that the surface gravity essentially levels out for a while.

This isn't something I think you could predict from amateur astronomical principles. What you would predict (certainly, what I predicted) would be what we see on the left side of the above figure, where more mass equals more surface gravity. All of the small rocky bodies in our own Solar System fall onto that left side of the graph. The plateau only really begins in the Earth range of planetary mass. You can see how Venus is included in the plateau almost perfectly, but the much less massive Mars is not.

This is a truly remarkable finding about planetary formation, and has serious implications both for fictional worldbuilding and someday for planetary colonization. That is, if these observations are truly representative of the Universe. This is a pretty big "if" that I don't have the knowledge to be able to check, except to say that there may be some bias unaccounted for because of how we detect exoplanets, such that perhaps the ones we detect are not representative of the ones we do not—so take it all with a grain of salt. This paper is 8 years old but I couldn't find anything newer following up on it.

Fully understanding how it would work is still a question mark for me. I mean, it's a question mark for the professional planetary scientists, too, so there's that, but, in addition to the unknowns that curtail their comprehension, there's a lot I don't know about astronomy that further curtails mine. My understanding is that this isn't really about the intrinsic density of the materials (i.e. substances that are more massive or less massive per mole); it would mainly have to be a consequence of how planets form, how the geological processes change in different planetary mass categories; that sort of thing. But I don't really know! I'm out of my depth.

Anyway, you can download a copy of the full paper on its entry page on ResearchGate; look for the button that says "Download full-text." And the website Centauri Dreams has a nice write-up which is where I originally discovered this.

[deep-space-netwerk]

please please please PLEASE share more on your Thoughts about gas giants!! i'd love to learn in a way that doesnt leave me baffled and half my brain leaking from my ears! you explained things so well in the psyche post and also i think things are generally more fun to learn from someone who is Excited To Share than from Published Research Papers where everything has been dried out For Professional Reasons- understandably so, mind, but i am not In The Field and dont know the terms lol

Okay it's taken me forever to get back to this but I AM SO GLAD YOU ASKED.

Like other planets, it all starts with a disk made of gas and dust orbiting an infant star, called a protoplanetary disk. Like these in the Orion Nebula, discovered by the Hubble!

To form terrestrial planets (rocky planets with relatively thin atmospheres like Mercury, Venus, Earth, and Mars), the gas in the protoplanetary disk coalesces to form hundreds and hundreds of rocky bodies called planetesimals, about a kilometer across. These planetesimals collide, and form dozens of protoplanets about the size of the moon. The protoplanets then collide as well, and stabilize to form the solar system as we know it today.

But, in the case of gas giants, colliding protoplanets don't form fully-finished planets. Instead, they form a core, or a seed.

We think the only thing that determines whether a planet will be terrestrial or a gas giant is simply how far away from the sun it forms - that's it. As a new sun warms its evolving solar system, it heats up the material in the protoplanetary disk. Close to the sun, the disk gets hotter, and things like water and other ices melt and evaporate into gas, making them difficult for the protoplanets to gravitationally capture. However, further away, the icy compounds stay cold enough to remain solid and coalesce along with rocky particles.

That boundary in the solar system - where ices evaporate to gas on the sunward side, and remain solid on the other - is called the "Frost Line". In our solar system, the Frost Line is right between Mars and Jupiter.

The protoplanets that form past the Frost Line turn into gas giant seeds, and are able to (kinda literally) snowball, picking up both rocky and icy material. With all that solid ice available, they grow far larger and far faster than planets in the inner solar system, and their gravity gets stronger and stronger. More gravity causes them to collect even MORE material until they're heavy enough to capture extremely lightweight elements like hydrogen and helium. Which, of course, makes them get even bigger and even heavier! Runaway growth!

But weirdly, as we study more exoplanets (planets that orbit stars other than our sun), we keep finding these huge gas giants incredibly close to their stars! Like, even closer than Mercury is to ours, which is insane. These "Hot Jupiters" break so many rules - gas giants "should" only be able to form where ice stays frozen, but here they are up close and personal with their stars, like this artist's concept!

It's possible that these planets are in the process of migrating closer to their stars, and we're managing to see them before they evaporate, but we just! Keep! Finding them!

One of my favorite parts of planetary science is how much we still have to learn. We'll think we have a pretty good idea of how things work out there, and then suddenly we'll find something that we can't explain. And there's an entire universe of weird shit - we've barely begun to scratch the surface!

[lonestarflight]

"A Rocky Planet Forms

An artist's rendition of how a rocky planet forms.

As a rocky planet forms, the planet-forming material gathers in a process known as 'accretion.' It grows larger in size, and increases in temperature, along with the pressure at its core. The energy from this initial planet forming process causes the planet's elements to heat up and melt. Upon melting, layers form and separate. The heavier elements sink to the bottom, the lighter ones float to the top. This material then separates into layers as it cools, which is known as 'differentiation.' A fully formed planet slowly emerges, with an upper layer known as the crust, the mantle in the middle, and a solid iron core.

InSight is short for Interior Exploration using Seismic Investigations, Geodesy and Heat Transport. The InSight mission will help answer key questions about how the rocky planets of the solar system, as well as how rocky exoplanets, formed. So while InSight is a Mars mission, it's also more than a Mars mission.

The lander seeks the fingerprints of the processes that formed the rocky planets of the solar system, more than 4 billion years ago. It measures the planet's 'vital signs:' its 'pulse' (seismology), 'temperature' (heat flow) and 'reflexes' (precision tracking)."

Date: January 25, 2018

NASA ID: PIA22233

[ianmiller42]

Mission to Uranus

As many people know, Uranus is a planet that is tilted onto its side and that makes it very unusual. Why, and how did that happen? There is an incentive to send a mission o find out what we can, but that is extremely expensive, so if you do you want to find out as much as you can about the system. That includes looking at the moons, because their orbits follow the tilt. That tilt means the system…

[jingszo]

Scientists have discovered a rare sight in a nearby star system: Six planets orbiting their central star in a rhythmic beat. The planets move in an orbital waltz that repeats itself so precisely it can be readily set to music.

This discovery is going to become a benchmark system to study how sub-Neptunes, the most common type of planets outside of the solar system, form, evolve, what are they made of, and if they possess the right conditions to support the existence of liquid water in their surfaces.

A rare resonance

The six planets orbit a star known as HD110067, which lies around 100 light-years away in the northern constellation of Coma Berenices.

[headlinehorizon]

Red Dwarf Reveals Unexpected Planet: Headline Horizon!

In the latest news, astronomers have made a surprising discovery - a planet much larger than expected orbiting a red dwarf star. This revelation challenges previous theories on planetary formation around these common stars.

[mindblowingscience]

Clouds of dust and gas not far from our solar system are giving astronomers a rare glimpse into the earliest stages of planet formation. These clouds, which are between 200,000 and 500,000 years old and lie within 700 light-years of Earth, have been spotted hosting dusty, gas-rich disks around a central star — the birthplaces of planets. Photos of these features, captured by the Atacama Large Millimeter/submillimeter Array (ALMA), were unveiled on Monday (Jan. 8) at the American Astronomical Society conference being held in New Orleans and online.

Continue Reading.

[siryl]

David A. Hardy's "Lift-Off Jupiter" a.k.a. "Jupiter Rocket," a revised version of "Lift-Off" a.k.a. "Marshmallow Moon."

[siryl]

Inspired by the Tears of the Oracle cover?

-Ancient worlds

[spacenutspod]

SpaceTime Series 28 Episode 20 The Astronomy, Space and Science News Podcast New Discoveries on Earth's Elements, Uranus's Moon Ariel, and the Fate of Comet Atlas In this episode of SpaceTime, we delve into a groundbreaking study that challenges long-held beliefs about the origins of Earth's missing moderately volatile elements, such as copper and zinc. This research suggests that rather than being lost during the early formation of the solar system, these essential elements were likely retained by the first planetesimals and lost later due to violent cosmic collisions during planetary growth, reshaping our understanding of planetary chemistry and habitability. Uranus's Moon Ariel: A Window to Its Interior We also explore the fascinating trench-like features on Uranus's moon Ariel, which may serve as conduits for internal materials. New research indicates that these medial grooves could provide insights into Ariel's geological history and potential subsurface oceans, highlighting the complex interplay of tectonic and volcanic activities on the moon's surface. Comet Atlas: A Dying Wonder Additionally, we discuss the fate of Comet G3 Atlas, which has recently passed perilously close to the Sun, resulting in the fragmentation of its nucleus. As it fades from view, Atlas becomes a headless wonder, leaving behind a trail of debris that will continue to orbit the Sun. This episode also features a look at the stunning night skies of February, including the iconic constellations and celestial events to observe. 00:00 Space Time Series 28 Episode 20 for broadcast on 14 February 2025 00:49 New insights into Earth's missing elements 06:30 Trench-like features on Uranus's moon Ariel 12:15 The demise of Comet G3 Atlas 18:00 February night sky highlights 22:45 The constellation Orion and its myths 27:00 Exploring the Pleiades and other celestial wonders 30:15 The significance of the Milky Way in stargazing www.spacetimewithstuartgary.com www.bitesz.com 🌏 Get Our Exclusive NordVPN deal here ➼ www.bitesz.com/nordvpn. Enjoy incredible discounts and bonuses! Plus, it��s risk-free with Nord’s 30-day money-back guarantee! ✌ Check out our newest sponsor - Old Glory - Iconic Music and Sports Merch and now with official NASA merchandise. Well worth checking out... Become a supporter of this Podcast for as little as $3 per month and access commercial-free episodes plus bonuses: https://www.spacetimewithstuartgary.com/about ✍️ Episode References NASA https://www.nasa.gov Science Advances https://www.science.org/journal/sciadv Planetary Science Journal https://www.journals.elsevier.com/planetary-science-journal Sky and Telescope https://skyandtelescope.org

[wnewsroom365]

বিভিন্ন গ্রহের কক্ষপথ আলাদা কেন? কি তথ্য জানালেন বিজ্ঞানীরা!

[tarotpathways]

Horoscopes

Daily Horoscope for June 13, 2024: Insights from Tarot and Astrology Welcome to your daily horoscope for June 13, 2024! Today, we delve into the insights provided by planetary placements, astrology, numerology, and tarot cards to give you a comprehensive guide on what to expect. Whether you’re looking for guidance on personal growth, relationships, or career, we’ve got you covered. Aries Tarot…

[ianmiller42]

Water on Rocks in Space

You will be aware of the famous line, “Water water everywhere, and not a drop to drink.” In fact it appears that water IS, if not everywhere, it is fairly close to it. The latest discovery, according to Physics World, is that water has been found on two stony S-type asteroids, which have been considered to have been formed dry. “Hydrated minerals” have been detected on hundreds of asteroids, but…

[worldwidebreakingnews]

Unraveling the mysteries of lunar formation and challenging conventional wisdom about the Moon's origin. The Day Our Moon Turned Itself Inside Out

[physalian]

Small fantasy worldbuilding elements you might want to think about:

A currency that isn’t gold-standard/having gold be as valuable as tin

A currency that runs entirely on a perishable resource, like cocoa beans

A clock that isn’t 24-hours

More or less than four seasons/seasons other than the ones we know

Fantastical weather patterns like irregular cloud formations, iridescent rain

Multiple moons/no moon

Planetary rings

A northern lights effect, but near the equator

Roads that aren’t brown or grey/black, like San Juan’s blue bricks

Jewelry beyond precious gems and metals

Marriage signifiers other than wedding bands

The husband taking the wife's name / newlyweds inventing a new surname upon marriage

No concept of virginity or bastardry

More than 2 genders/no concept of gender

Monotheism, but not creationism

Gods that don’t look like people

Domesticated pets that aren’t re-skinned dogs and cats

Some normalized supernatural element that has nothing to do with the plot

Magical communication that isn’t Fantasy Zoom

“Books” that aren’t bound or scrolls

A nonverbal means of communicating, like sign language

A race of people who are obligate carnivores/ vegetarians/ vegans/ pescatarians (not religious, biological imperative)

I’ve done about half of these myself in one WIP or another and a little detail here or there goes a long way in reminding the audience that this isn’t Kansas anymore.

[niqhtlord01]

Humans are weird: Human cameramen are crazy

( Please come see me on my new patreon and support me for early access to stories and personal story requests :D https://www.patreon.com/NiqhtLord Every bit helps)

The greatest decision Intergalactic Wave 6 ever made was hiring Reggie Bradford.

At the time of Finch’s hiring IW6 was a relatively small news organization based in the outer worlds. Barely reaching four systems on a good day compared to the top contenders like Celestial Times which was broadcasted in inner core systems and pulled in an average of twenty to thirty systems each broadcast. The anchors for IW6 were locals, a Temrelien that needed a third grade translator unit just to be barely understood and a Myporie which couldn’t see the color green.

As the underdog’s underdog, IW6 more often fed off larger stories reported by other stations or small local stories relevant to a handful of worlds.  Nothing interesting happened in their corner of the universe so as long as they broke even they were fine to never reach further than the length of their arm.

Reggie Bradford was a hired on as a cameraman to work for one of the planetary studios on Orbin VIII. You’d find him either working in the back making sure the camera bots were functioning or, more often, when they weren’t he’d be manning the forty pound cameras himself. The studio crews were always amazed how this seemingly out of shape man could heft the heavy outdated camera unit like it was as light as a pen.

They wondered what a lone human was doing so far out in the boonies as he would say, but he would always shrug and say that he felt like this is where he belonged; a notion IW6 would be most grateful for in the coming days.

When the Intherax/Coalition war broke out it was the biggest news story to hit the plasma streams since the death of Empress Karen III when she was eaten by her own corganai.

The Intherax were a militaristic society, trained from birth to kill before anything else, and spanned some fifty star systems not including client kingdoms and vassals. General galactic dealings with them often boiled down to standing aside from whatever they wanted and hoping it wasn’t you or your world, lest the invasion armadas would descend and obliterate what little civilization your people had been able to achieve and then be sold into slavery.

This time however when the Intherax made a proclamation to annex the colony worlds of Jense, Shatu’a, and New Hamburg the current occupants politely told them to bugger off and formed a Coalition for mutual defense. From there dozens of governing powers flocked to the coalition and added their strength to it in what they saw as the best chance of finally checking Intherax aggression once and for all.

Ever one for a challenge, the Interax declared war on this new found coalition and opened the conflict by orbital bombarding Jense until it was little more than a cold husk of rock trapped in the decaying orbit of its system’s sun.

What followed was best described as two sides of no holds bar warfare as the Coalition retaliated with the first ever invasion of Intherax territory against the world called Kai’de.

Naturally every news organization wanted to be seen covering the war, including IW6. Sadly they did not have anyone either brave enough to send so they settled on sending someone they believed was stupid enough and sent Reggie.

They expected to get some b-roll of soldiers marching or shots of fleet warships in formation. They never expected nor asked him to go into active combat. So when the first feed came back during their late night broadcast they were surprised to see that Reggie was onboard an assault ship breaking through atmosphere.

“Reggie,” the Temrelien spoke with every other word shifting tone from the broken translator, “where are you?”

“I’m currently with brave members of the 27th Dragoons as they head to take the fight to the surface of Kai’de.”

Reggie waved a hand at the soldiers who in turn gave a rousing cheer and slammed their feet against the metal decking.

“Orders came in late last night for a massed landing to take the enemy by surprise. From what I understand the Intherax military had not expected coalition forces to invade their territory and have not had time to establish proper defenses.”

Both news anchors looked at each other in confusion.

“If that’s the case isn’t this broadcast putting the entire attack at risk?”

To their surprise Reggie laughed as the camera shook.

“The plan was to get them by surprise, but judging from the amount of anti-air fire,” he said as the assault ship rocked back and forth, “I don’t think they were fooled.”

The camera panned right suddenly as one of the armored dragoons grabbed it and spoke directly into it.

“We want them to know we’re coming! Because we’re going to kill them all!! AHAHAHAH!!”

Another chorus of cheers and whoops came from the soldiers as the soldier let go of the camera and Reggie readjusted it. The anchors wanted to continue their questions when the leader of the dragoons shouted out and interrupted them.

“60 seconds!”

With the order given the soldiers stopped their foolery and began hefting their weapons. Reggie panned the camera over them as they slapped in fresh clips or attached power cables from their backpack generators to their more heavy weaponry.

In awestruck silence the anchors and their viewers watched as the assault shuttle slammed hard into the surface and the boarding ramp flew open.

“GO GO GO GO!!!!” the dragoon leader shouted as the soldiers poured out screaming their battle cries. Reggie waited and filmed them as they disembarked but did not join the first out the ramp. A inclination that saved him as enemy gun fire began raking the ramp striking several soldiers down in clouds of viscera and gore.

The censors barely had time to cut the feed while the horrified anchors composed themselves to resume the broadcast.

In the hours that followed IW6 confirmed that Reggie had survived the battle and had been with the unit of dragoons for the entire duration. During those hours he had recorded the entire engagement from ramp down, to storming city streets as the Intherax deployed building sized walkers, to the hoisting of the coalition flag over the central governing building at the heart of the city.

With this footage viewership numbers for IW6 skyrocketed overnight as none of the other networks had been able to capture such stunning footage. In fact, by the intake of broadcasts none of them had been able to attach an anchor or cameramen to the initial assault save for Reggie. When asked how he had been able to get approved for such a deployment he did not say which only further added to the mystery. Yet for the moment IW6 was far from ready to look a gift horse in the mouth.

Reggie’s footage was shown over and over on IW6 and was soon sublicensed to other networks and shown there. Exploits of the dragoons became known galaxy wide as Reggie followed them through battle after battle; never afraid to risk his life to capture the perfect moment.

When the Intherax fleet arrived in orbit and began to bombard the planet while also fighting the coalition fleet Reggie had forgone sheltering in nearby bunker complexes to film the orbital strikes as they hurtled down all around them.

Thick columns of pure energy shattered buildings and mountains alike as the ground quaked and there stood a lone Reggie filming it all. Even when the anchors begged him to find shelter he simply panned the camera over the city to show entire skyscrapers be reduced to molten mounds the oozed and sludged through the city streets.

By the time the battle had finally ended thanks to Reggie’s footage IW6 climbed the viewership charts to be the third most watched network galaxy wide. Much to the dismay of IW6 it also drew the attention of Reggie the cameraman to the other outlets who began showering him with ever more lavish offers for employment.

Too their surprise he denied them all and said that he was right where he belonged.