#Black holes

[mindblowingscience]

Almost 14 billion years ago, at the very beginning of the Big Bang, a mysterious energy drove an exponential expansion of the infant universe and produced all known matter, according to the prevailing inflationary universe theory. That ancient energy shared key features of the current universe's dark energy, which is the largest mystery of our time by at least one objective standard: It makes up the majority—roughly 70%—of the universe, but scientists don't know exactly what it is.

Continue Reading.

[evil-scientist]

[REDACTED] if you agree

[nasa]

A Tour of Cosmic Temperatures

We often think of space as “cold,” but its temperature can vary enormously depending on where you visit. If the difference between summer and winter on Earth feels extreme, imagine the range of temperatures between the coldest and hottest places in the universe — it’s trillions of degrees! So let’s take a tour of cosmic temperatures … from the coldest spots to the hottest temperatures yet achieved.

First, a little vocabulary: Astronomers use the Kelvin temperature scale, which is represented by the symbol K. Going up by 1 K is the same as going up 1°C, but the scale begins at 0 K, or -273°C, which is also called absolute zero. This is the temperature where the atoms in stuff stop moving. We’ll measure our temperatures in this tour in kelvins, but also convert them to make them more familiar!

We’ll start on the chilly end of the scale with our CAL (Cold Atom Lab) on the International Space Station, which can chill atoms to within one ten billionth of a degree above 0 K, just a fraction above absolute zero.

Credit: NASA's Goddard Space Flight Center/Scott Wiessinger

Just slightly warmer is the Resolve sensor inside XRISM, pronounced “crism,” short for the X-ray Imaging and Spectroscopy Mission. This is an international collaboration led by JAXA (Japan Aerospace Exploration Agency) with NASA and ESA (European Space Agency). Resolve operates at one twentieth of a degree above 0 K. Why? To measure the heat from individual X-rays striking its 36 pixels!

Credit: NASA's Goddard Space Flight Center/Scott Wiessinger

Resolve and CAL are both colder than the Boomerang Nebula, the coldest known region in the cosmos at just 1 K! This cloud of dust and gas left over from a Sun-like star is about 5,000 light-years from Earth. Scientists are studying why it’s colder than the natural background temperature of deep space.

Credit: NASA's Goddard Space Flight Center/Scott Wiessinger

Let’s talk about some temperatures closer to home. Icy gas giant Neptune is the coldest major planet. It has an average temperature of 72 K at the height in its atmosphere where the pressure is equivalent to sea level on Earth. Explore how that compares to other objects in our solar system!

Credit: NASA's Goddard Space Flight Center/Scott Wiessinger

How about Earth? According to NOAA, Death Valley set the world’s surface air temperature record on July 10, 1913. This record of 330 K has yet to be broken — but recent heat waves have come close. (If you’re curious about the coldest temperature measured on Earth, that’d be 183.95 K (-128.6°F or -89.2°C) at Vostok Station, Antarctica, on July 21, 1983.)

We monitor Earth's global average temperature to understand how our planet is changing due to human activities. Last year, 2023, was the warmest year on our record, which stretches back to 1880.

Credit: NASA's Goddard Space Flight Center/Scott Wiessinger

The inside of our planet is even hotter. Earth’s inner core is a solid sphere made of iron and nickel that’s about 759 miles (1,221 kilometers) in radius. It reaches temperatures up to 5,600 K.

Credit: NASA's Goddard Space Flight Center/Scott Wiessinger

We might assume stars would be much hotter than our planet, but the surface of Rigel is only about twice the temperature of Earth’s core at 11,000 K. Rigel is a young, blue star in the constellation Orion, and one of the brightest stars in our night sky.

Credit: NASA's Goddard Space Flight Center/Scott Wiessinger 

We study temperatures on large and small scales. The electrons in hydrogen, the most abundant element in the universe, can be stripped away from their atoms in a process called ionization at a temperature around 158,000 K. When these electrons join back up with ionized atoms, light is produced. Ionization is what makes some clouds of gas and dust, like the Orion Nebula, glow.

Credit: NASA's Goddard Space Flight Center/Scott Wiessinger

We already talked about the temperature on a star’s surface, but the material surrounding a star gets much, much hotter! Our Sun’s surface is about 5,800 K (10,000°F or 5,500°C), but the outermost layer of the solar atmosphere, called the corona, can reach millions of kelvins.

Our Parker Solar Probe became the first spacecraft to fly through the corona in 2021, helping us answer questions like why it is so much hotter than the Sun's surface. This is one of the mysteries of the Sun that solar scientists have been trying to figure out for years.

Credit: NASA's Goddard Space Flight Center/Scott Wiessinger

Looking for a hotter spot? Located about 240 million light-years away, the Perseus galaxy cluster contains thousands of galaxies. It’s surrounded by a vast cloud of gas heated up to tens of millions of kelvins that glows in X-ray light. Our telescopes found a giant wave rolling through this cluster’s hot gas, likely due to a smaller cluster grazing it billions of years ago.

Credit: NASA's Goddard Space Flight Center/Scott Wiessinger

Now things are really starting to heat up! When massive stars — ones with eight times the mass of our Sun or more — run out of fuel, they put on a show. On their way to becoming black holes or neutron stars, these stars will shed their outer layers in a supernova explosion. These layers can reach temperatures of 300 million K!

Credit: NASA's Goddard Space Flight Center/Jeremy Schnittman

We couldn’t explore cosmic temperatures without talking about black holes. When stuff gets too close to a black hole, it can become part of a hot, orbiting debris disk with a conical corona swirling above it. As the material churns, it heats up and emits light, making it glow. This hot environment, which can reach temperatures of a billion kelvins, helps us find and study black holes even though they don’t emit light themselves.

JAXA’s XRISM telescope, which we mentioned at the start of our tour, uses its supercool Resolve detector to explore the scorching conditions around these intriguing, extreme objects.

Credit: NASA's Goddard Space Flight Center/CI Lab

Our universe’s origins are even hotter. Just one second after the big bang, our tiny, baby universe consisted of an extremely hot — around 10 billion K — “soup” of light and particles. It had to cool for a few minutes before the first elements could form. The oldest light we can see, the cosmic microwave background, is from about 380,000 years after the big bang, and shows us the heat left over from these earlier moments.

Credit: NASA's Goddard Space Flight Center/Scott Wiessinger

We’ve ventured far in distance and time … but the final spot on our temperature adventure is back on Earth! Scientists use the Large Hadron Collider at CERN to smash teensy particles together at superspeeds to simulate the conditions of the early universe. In 2012, they generated a plasma that was over 5 trillion K, setting a world record for the highest human-made temperature.

Want this tour as a poster? You can download it here in a vertical or horizontal version!

Credit: NASA's Goddard Space Flight Center/Scott Wiessinger

Explore the wonderful and weird cosmos with NASA Universe on X, Facebook, and Instagram. And make sure to follow us on Tumblr for your regular dose of space!

[ell-dordo]

When I get mad, I like to draw black holes

[paula-zotter]

about black holes

[lime-bloods]

I honestly didn't ever expect that I'd be in the position where I'd be using this blog not just to analyse what has come before in Homestuck, but to look toward the comic's future and do some real old-fashioned theorycrafting. but the time has come. so here goes; lime-bloods' Beyond Canon theories as of the July 6th 2024 update:

Vriska's Going to Hell

were all gonna help you! / whether you like it or not

a select few eagle-eyed readers already noticed that the sound used in last month's (Vriska: Figure shit out yourself.) is called "hell_tierwav". while it was easy to dismiss this as irrelevant composer shenanigans at the time, it's now become clear exactly what this was foreshadowing. whether it would be more apt to call this "Hell" or "Purrgatory" is probably up for debate - but whatever you call it, Vriska's been placed in a dimension seemingly tailored specifically for her personal torment.

while Vriska characteristically interprets the recreation of her childhood home as a symbol of how badass she was, the ghosts of her past - both literal, as the shades of the trolls she killed as Mindfang, and figurative, in the form of sprites wearing the faces of her dead friends - show us in no uncertain terms that Vriska's childhood home is the stage where traumas play out.

Erisolsprite puts it succinctly with his welcome to hell, but pay close attention to what exactly we're being welcomed to: this update ends on page 665. so as of this next update, we'll be starting on page 666.

Does Homestuck Have Hell?

the exact bubble of reality Vriska's currently found herself in seems to be an entirely new construction of the likes we've not yet seen in Homestuck - but that doesn't mean this kind of cosmic torment is without precedent. because while 666 is a number with Satanic connotations in the broader cultural context, it also has a very particular meaning of its own within the world of Homestuck. indeed, the latter half of the comic almost revolves around it, culminating in a climax in Act 6 Act 6 Act 6.

specifically, this repetition of a single digit is emblematic of recursive storytelling. to summarise what you can already read about in detail in my essay The World / The Wheel: when Caliborn is 'gifted' the Act 6 Act 6 supercartridge, which he is told is an "expansion" of Homestuck, it's a trick. there is no "expansion"; he's going to be trapped in a story that never ends because it keeps dividing into smaller and smaller versions of itself forever. the only way to truly beat the devil who trapped the heroes within a story is to trap him in his own story.

that's what Caliborn's "Hell" is, and that's also exactly what the Alternate Calliope achieved in Act 7 by creating the black hole which Vriska knocked Lord English into, ending Homestuck's story - something that Calliope even hints at in this very update, when she refers to the black hole as "containment"; not an accident, but a deliberately crafted prison. black holes are a symbol of recursion and regression; being sucked into one means being forced to live out your whole life over and over again, forever. so really, this is all we ever could have expected to happen when Vriska stepped into a black hole within a black hole! the presentation of the narrative even subtly hints at this; events in Beyond Canon that take place in the black hole are enclosed (in brackets), and now events that take place in a black hole-within-a-black-hole are contained within {curly brackets}, because you should always use a different kind of brackets to differentiate nested parenthesis from each other!

it is absolutely no coincidence that when Caliborn closes the curtains on his appearances in Homestuck, thinking he's won when really he's been condemned to a hell of his own making forever more, it's with a tribute to this exact same Sweet Bro and Hella Jeff strip.

IF YOU REMEMBER JUST ONE THING I SAY, OF SO MANY GREAT THINGS SAID BY ME, THEN PLEASE REMEMBER THIS. I WANTED TO PLAY A GAME.

So What Does That Mean?

one of Beyond Canon's central missions is expanding upon Homestuck's exploration of the relationships between author, text, and audience. as discussed above, a large part of Homestuck's thesis is the evil of forcing characters to live the same lives and the same stories over and over without the chance to grow or move on, and Beyond Canon picks up on this by placing Dirk in the position of trying to keep Homestuck going forever purely to appease its fans, while the Alternate Calliope continues to oppose this ideology. and while the alpha Calliope outwardly seems not to have taken a hard position on where she stands in this cosmic battle, the question posed by her device seems to be an entirely new one: can it actually be a good thing to regress, to return to ground that the story has already covered? can this path lead to something new, rather than merely stagnation?

it's so relevant that Vriska is being confronted with the crimes of her past, not only in the form of all the trolls she was personally responsible for killing but also in the form of the exact same punishment she condemned Lord English to with her heroism - complete with the herd of horses that are always present at Caliborn's demise! but where being condemned to an eternal cycle was fitting punishment for Caliborn, someone who refuses to break free of cycles of abuse and instead chooses to enact that same abuse on the world around him... if Vriska is someone who can break free of these cycles, who can change and become a better person despite what happened to her, will this punishment have the same effect? or, as Davepeta seems to believe, is forcing Vriska to reckon with her own past and traumas exactly what will allow her to break free of that cycle?

DAVE: [...] ill just be over here in the hyper gravity chamber training to beat lord english KARKAT: WE HAVE A HYPER GRAVITY CHAMBER???

it's hard not to be struck by the parallels in design and purpose between the Plot Point and Dragon Ball's Hyperbolic Time Chamber, and not just because of the Dragon Ball enthusiasts present on Beyond Canon's writing and art teams: albeit in typically Strider-bastardised form, the Time Chamber got a shoutout in Andrew Hussie's own Homestuck (see quote above), in a reference that was even picked up on by prolific theorist bladekindeyewear at the time. for the uninitiated: the Hyperbolic Time Chamber allowed its users to train for extended stretches of time, sometimes even spanning years, while a significantly smaller time period passed in the world outside - something that is actually true of real-life black holes! and with the Plot Point's own emphasis on time, represented by the hourglass included among its mechanisms, it seems to me that an essential part of making the 16-year-old Vriska ready for the trials ahead will be giving her the time to undergo the same growth her adult friends have experienced.

considering that Beyond Canon is already playing in the Ultimate Self space, where there are levels of power beyond merely the "god tiers", it also doesn't seem too farfetched to speculate that Vriska, forced to reckon with the fact that becoming a powerful Thief of Light isn't the be-all and end-all of personal growth, will take another leaf out of Dragon Ball's book here and ascend "beyond Super Saiyan". perhaps this is even the "hell tier" so cheekily alluded to in the Plot Point flash? certainly this kind of evolution would be the perfect way to challenge Dirk's belief that the Ultimate Self is the only logical final step for a character's development.

whatever the case, I believe we can take Davepeta at their word here. I don't think it's just a joke that by the end of this ordeal Vriska Serket is going to be fucking RIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIPPPPPPPPPED!

[cal-1maf]

Before we get into black holes, there are a few myths about them that deserve to be addressed.

First off, they don’t “suck stuff in.” They exert gravity on objects the same as anything else with mass. In fact, if our sun were to be magically replaced, instantly, with a black hole of equal mass, our orbit around it wouldn’t change at all! 

Second, that they���re black because their gravitational pull is so large that not even light can escape. This one’s more complicated. Around the singularity, there is a region of space where an observer cannot see “in”, which is called the event horizon. If you’re curious, this region’s size is defined by the black hole’s “Schwarzchild Radius” (Rs), which is defined by the equation Rs = 2GM / (c^2) where G is the gravitational constant, M is the mass of the black hole, and c is the speed of light.

In simple terms, let’s say we send an astronaut into the black hole. As they approach the event horizon, they experience time passing normally. From their perspective, they fall toward the black hole, through the event horizon, and observe whatever is happening beyond it. But from our perspective as an observer, the astronaut appears to slow down. Gravity affects spacetime, and the farther down a gravity well one goes, the slower time moves. This is actually something that GPS satellites need to account for, because this difference is observably present even for Earth’s gravity!

So as observers, the astronaut’s progress continues to slow as they approach the event horizon, to the point that their progress appears to just stop when they arrive at the edge of it. This is where the astronaut will appear to be, forever…if we could still see them. Light is also affected: it appears to slow down too and its frequency decreases. This decrease of its frequency is called redshift, and as the light approaches the event horizon it redshifts out of observable frequencies. So the astronaut, and the light with which we’d observe them, disappear without ever passing the event horizon from our perspective as observers. Remember, from the astronaut’s perspective they’re moving as normal and they pass through the event horizon just fine. So while, yes light can’t escape the event horizon, we’d never see it pass into it in the first place, and that’s why black holes appear black.

The last misconception, which I’m guilty of spreading in my last post, is that all black holes are infinitely dense. This is true in some cases, but supermassive black holes can actually have very low density! When I can find a satisfying answer as to why, I will be sure to share it lol.

This has become another one of my Very Long Posts, so if you would rather absorb this information in video or audio format, PBS Space Time has an excellent video here which I found very helpful in my understanding. All the material I’ve covered in this post is in this video, actually.

[honourablejester]

I love the sentences you get with science fantasy. Just. The things you get to say.

I’m reading Starfinder’s Ports of Call sourcebook (1e), which has part of a chapter describing the galaxy the setting is set in. At the centre of said galaxy is a titanic black hole nicknamed Old Rovagug (after the vanished god of destruction) which supplies the gravity needed to hold the galaxy together. And we get this spectacular sentence, a result of the fact that Starfinder is a science fantasy setting using D&D style planes of existence:

“Like most black holes, Old Rovagug tears open millions of momentary rifts to the Negative Energy Plane every second, allowing creatures like spectral undead, gargoyle-like sceaduinars and titanic darvakkas to escape into the surrounding space. These interlopers rampage across any worlds they can reach before the oppressiveness of reality inevitably disintegrates them.”

… Like most black holes. Like most black holes, Old Rovagug tears millions of holes into the plane of death on the regular, allowing undead to escape into nearby space until the raw weight of reality reabsorbs them. As, you know. Black holes do. Apparently.

This is followed by:

“Unlike most black holes, Old Rovagug radiates light-year-wide entropic tendrils. Seeming to ignore material physics, these tendrils extend and roil outward like solar flares for thousands of years before fading and being replaced by new projections. Like black holes, they aren’t directly visible, instead being observed only by the empty spaces they leave behind—most often along the accretion disk, earning them the name Whiskers of the Sun-Eater for how they radiate from the lightless center of the galaxy.”

This black hole also radiates reality-shredding thousand-year-long entropic flares. Most black holes don’t do that. It’s just this one.

I just. I love the things you get to say. Most black holes, you know. They summon spectral undead. Didn’t you know that about them?

[mindblowingscience]

In the constellation of Cygnus, some 7,800 light-years from Earth, lurks a real space oddity. There, a black hole in a system named V404 Cygni repeatedly engages in behavior that has simultaneously baffled and delighted scientists. Now it's whipped a brand new trick out of its seemingly endless arsenal: an unseen binary companion, a star on a wide orbit of around 70,000 years. Since V404 Cygni already has a companion – a star on a close, 6.5-day orbit, on which the central black hole is leisurely feasting – the newly discovered third object makes the system a trinary.

Continue Reading.

[spacetelescopescience]

When an astronomer spies stars or gas moving with speeds or temperatures suggesting they are orbiting something massive and small, it’s a clue that a black hole is nearby. Check out what scientists watch out for in their search for black holes: https://webbtelescope.pub/3MZtygj

[nasa]

Black Hole Friday Deals!

Get these deals before they are sucked into a black hole and gone forever! This “Black Hole Friday,” we have some cosmic savings that are sure to be out of this world.

Your classic black holes — the ultimate storage solution.

Galactic 5-for-1 special! Learn more about Stephan’s Quintet.

Limited-time offer game DLC! Try your hand at the Roman Space Observer Video Game, Black Hole edition, available this weekend only.

Standard candles: Exploding stars that are reliably bright. Multi-functional — can be used to measure distances in space!

Feed the black hole in your stomach. Spaghettification’s on the menu.

Act quickly before the stars in this widow system are gone!

Add some planets to your solar system! Grab our Exoplanet Bundle.

Get ready to ride this (gravitational) wave before this Black Hole Merger ends!

Be the center of attention in this stylish accretion disk skirt. Made of 100% recycled cosmic material.

Should you ever travel to a black hole? No. But if you do, here’s a free guide to make your trip as safe* as possible. *Note: black holes are never safe. 

Make sure to follow us on Tumblr for your regular dose of space!

[aspaceinthecosmos]

hello! i've got some GROUNDBREAKING space news for you!

scientists have uncovered evidence for a gravitational wave background (GWB) in our universe, and the way they went about it is fascinating.

To fully understand what's going on here, we need to go into a bit of background information.

First of all: what are gravitational waves? gravitational waves are often called 'ripples' in spacetime, often caused by extremely energetic processes such as black holes colliding, or two neutron stars orbiting each other closely.

So, how did scientists figure this out? They used 67 pulsars (known as the Pulsar Timing Array) throughout the Milky Way, practically creating a galaxy-sized telescope in order to study this.

Pulsars are the extremely dense cores of massive stars, left over after they go supernova. These are fascinating on their own, but for this project, they had an essential feature: Pulsars rapidly rotate (think up to hundreds of rotations per second), spewing radiation out in pulses from their magnetic poles. For some pulsars, these radiation jets cross Earth's line of sight, and we get incredibly constant bursts of radio signals, which can be catalogued and used as a sort of standard, universal clock.

Here is a link to a gif showing the rotation of a pulsar. Please be warned for flashing and eyestrain.

For 15 years, a team of astronomers working for the North American Nanohertz Observatory for Gravitational Waves (NANOGrav), used radio telescopes around the globe to track minuscule changes in the signal patterns from pulsars. The changes they found are due to the slight movement of spacetime between us and the pulsars, stretching and compressing the paths of their radio waves as extremely low frequency gravitational waves pass through the universe (yes, that includes you. your atoms, as well as the atoms making up everything around you, are very slowly shifting position, dancing along to the heartbeat of the universe).

At the moment, scientists are still debating what could have caused this gravitational wave background, but some there are some leading theories: the GWB could be caused by trillions of binary black hole systems (black holes orbiting each other) throughout the universe. It could also be due to cosmic inflation, or even the big bang itself. Scientists just don't know yet, but the opportunities this discovery opens up are incredible.

The knowledge of the GWB could help us better understand the formation of early galaxies, or even help us understand the origin of the universe.

[amnhnyc]

How do we discover new types of objects in space? One way is to invent new kinds of telescopes. Join Museum Curator Michael Shara on an exploration of evolving telescope technologies, the most powerful telescopes ever built, and how the future of stargazing might already be in your pocket.

Along the way, learn about the “wild and crazy” things stars do through Shara’s research into novas (stellar explosions that often repeat over time) and supernovas (the explosive deaths of stars).

[minmin-vs-physics]

[28/10/24] i locked in on black holes tonight after a lot of dilly dallying bc i have a gr exam tmr. really pumping the music helped A LOT. im kinda cooked bc this prof is in a whole other intellectual tax bracket and is known to have devastating exams (i have experienced them before). there is a LOT of math i am Not Confident on.

still, i was lowkey w0w bc black holes are so metal. at one point i wanted to do black hole physics and idk every kid wants to know more abt black holes bc they're so cool and wow im finally doing gr??? that's wild.

my friend once described our gr lecture as a pbs spacetime video and i Could Not stop laughing. but he's right! it feels like we've passed the event horizon of pop science now.

its always nice to get a moment of clarity after two L's in a row. time for another fight!

Supermassive Black Hole - Muse obviously in theme