Fitzy Fitz posted:

y'all read this?

https://zenodo.org/records/8213330

sharknado slashfic posted:

Please do not hardon collide the birds

euphronius posted:

if you are going to post xs please at least post the whole x

sharknado slashfic posted:

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Christopher K. Mellon

@ChrisKMellon

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My friend and colleague, Robert Powell, Executive Director of the Scientific Coalition for UAP Studies, has just published a terrific new book on UAP entitled, “UFOs: A Scientist Explains What We Know (And Don’t Know).” There are many great books on the UAP topic, but none I’ve read are so thorough, succinct, and up to date. The book begins by providing the most crisp and concise account I’ve yet read of the US government’s involvement with UAP from WWII to the present. Robert then launches into a brilliant and provocative, but unstintingly objective analysis of the best available UAP data. This slender volume, under 200 pages, flows smoothly and efficiently, covering more ground with fewer words than any other I’ve seen on the UAP issue. As Robert demonstrates, one does not need to cite conspiracies or embellish the facts to make the case that UAPs are a serious issue that warrants action on the part of our government and the scientific community. Even those who are steeped in the UAP issue will enjoy Robert’s new book, find fresh information, and benefit from his wisdom and insights. If someone asked for a single volume to help them understand what the UAP fuss is all about, this is the book I’d recommend. https://amazon.com/UFOs-Scientist-Explains-What-Know/dp/1538173581…

2:29 PM · Mar 27, 2024

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helta posted:

"Combining both the incredible speed and ability to stop and stay stationary strongly suggests this was not an aircraft available at the time, either friend or adversary. (A speed of 6,200 mph and hovering would put it outside of current known capabilities today, too.)

Given the fact that the UAP also transmitted an IFF response raises the possibility that it was not a radar anomaly and that the IFF transmission was a deliberate act, perhaps a test or potentially a form of messaging. (Sparks 1238)"

quote:

The first polarized image of our galaxy's supermassive black hole, Sagittarius A*, has been released

euphronius posted:

that’s the accusation disk and the shadow not the black hole

euphronius posted:

that’s the accusation disk and the shadow not the black hole

www.reddit.com/r/pics/comments/1bp3ukt/the_first_polarized_image_of_our_galaxys posted:

adio astronomer here! This is a big deal (and I'm colleagues with those who led the research!). For those who want an overview, here is what's going on!

What is this new result about?

Sagittarius A* (Sgr A* for short) is the supermassive black hole (SMBH) at the center of our Milky Way, and weighs in at a whopping 4 million times the mass of the sun and is ~27,000 light years away from Earth (ie, it took light, the fastest thing there is, 27,000 light years to get here, and the light in this photo released today was emitted when our ancestors were in the Stone Age). We know it is a SMBH because it's incredibly well studied- in fact, you can literally watch a movie of the stars orbiting it, and this won the teams studying it the 2020 Nobel Prize in Physics. So we knew Sag A* existed by studying the stars orbiting it (and even how much mass it had thanks to those orbits), and a picture of it was released in 2022, but it was missing an important piece of information- polarization.

Polarization is often called the "twist" of light, but really what it tells you is the direction of the waves traveling at you- is it straight up and down like waves in an ocean, or perpendicular to that, or somewhere in between? (Most people know polarized light best via sunglasses and tilting their head at water to see how the light changes.) In science, polarization is important because it contains important information on magnetic fields present- which might not sound exciting, but magnetic fields are hard to measure and understand! I wrote an article once for Astronomy on magnetic fields in the universe here, but the TL;DR is magnetic fields tell us a ton about the environment the light came from, such as from the event horizon around Sag A* in this case!

So, what the team did since the release of the Sag A* photo is take more data, and decipher that polarization information! So pretty! But that's not all- the magnetic field is quite structured, which implies we might have a hidden jet at the center of our Milky Way! An astrophysical jet is when material is beamed along an axis- sometimes this material can travel at relativistic speeds and be very long, but I do not think this is the case here. Instead, it seems most likely that the jet would be fairly weak in its outflow and "only" a few light years across... but still, if this holds, it would revolutionize our understanding about our galaxies and SMBH in general!

Didn't we already have polarization information for a black hole? Why is this one such a big deal?

We do! That black hole is M87*, which is located 53 million light years from Earth and is 7 billion times the mass of the sun (so over a thousand times bigger than Sag A*). It might sound strange that we saw this black hole first, but there were a few reasons for this that boil down to "it's way harder to get a good measurement of Sag A* than M87*." First of all, it turns out there is a lot more noise towards the center of our galaxy than there is in the line of sight to a random one like M87- lots more stuff like pulsars and magnetars and dust if you look towards the center of the Milky Way! Second, it turns out Sag A* is far more variable on shorter time scales than M87*- random stray dust falls onto Sag A* quite regularly, which complicates things.

However, it's because we have the M87* data already that this is so interesting- specifically, what is striking is how Sag A's magnetic field is REALLY similar to M87's. That is pretty wild because we can see a relativistic jet being launched from it- there is literally a Hubble picture- so even though these black holes are so different in mass, if their magnetic fields are so darn similar it really implies there might be a jet in Sag A* as well that we just aren't aware of.

I thought light can't escape a black hole/ things get sucked in! How can we get information from one/ launch jets from one?

Technically these pictures are never of the black hole, but from a region surrounding it called the event horizon. This is the boundary that if light crosses when going towards the black hole, it can no longer escape. However, if a photon of light is just at the right trajectory by the event horizon, gravitational lensing from the massive black hole itself will cause those photons to bend around the event horizon! As such, the photons never cross this important threshold, and are what we see in the image in this "ring."

Second, it's important to note that black holes don't "suck in" anything, any more than our sun is actively sucking in the planets orbiting it. Put it this way, if our sun immediately became a black hole this very second, it would shrink to the size of just ~3 km (~2 miles), but nothing would change about the Earth's orbit! Black holes have a bigger gravitational pull just because they are literally so massive, so I don't recommend getting close to one, but my point is it's not like a vacuum cleaner sucking everything up around it. (see the video of the stars orbiting Sag A* for proof).

As for the jets- this is not material crossing the event horizon, but instead dust that comes very close and gets launched outwards. We actually do NOT understand the full details of this- it's an active area of astrophysical research- but it does have to do with the magnetic fields present around the black holes. And one reason why today's results are so valuable!

How was this picture taken?

First of all, it is important to note this is not a picture in visible light, but rather one made of radio waves. As such you are adding together the intensity from several individual radio telescopes and showing the intensity of light in 3D space and assigning a color to each intensity level. (I do this for my own research, with a much smaller radio telescope network.)

What makes this image particularly unique is it was made by a very special network of radio telescopes literally all around the world called the Event Horizon Telescope (EHT)! The EHT observes for a few days a year at 230–450 GHz simultaneously on telescopes ranging from Chile to Hawaii to France to the South Pole, then ships the data to MIT and the Max-Planck Institute in Germany for processing. (Yes, literally on disks, the data volume is too high to do via Internet... which means the South Pole data can be quite delayed compared to the other telescopes!) If it's not clear, co-adding data like this is insanely hard to do- I use telescopes like the VLA for my research, and that already gets filled with challenges in things like proper calibration- but if you manage to pull it off, it effectively gives you a telescope the size of the Earth!

To be completely clear, the EHT team is getting a very well-deserved Nobel Prize someday (or at least three leaders for it because that's the maximum that can get the prize- it really ought to be updated, but that's another rant for another day). The only question is how soon it happens!

This is so cool- what's next?!

Well, I have some good news and some bad news. The bad news is we cannot do this measurement for any other supermassive black holes for the foreseeable future, because M87* and Sag A* are the only two out there that are sufficiently large in angular resolution in the sky that you can resolve them from Earth (Sag A* because it's so close, M87* because it's a thousand times bigger than a Sag A* type SMBH, so you can resolve it in the sky even though it's millions of light years away). You would need radio telescopes in space to increase the baselines to longer distance to resolve, say, the one at the center of the Andromeda Galaxy, and while I appreciate the optimism of Redditors insisting to me otherwise there are currently no plans to build radio telescopes in space in the coming decade or two at least.

However, I said there was good news! First of all, the EHT can still get better resolution on a lot of stuff than any other telescope can and that's very valuable- for example, here is an image of a very radio bright SMBH, called Centaurus A, which shows better detail at the launch point of the jet than anything we've seen before. Second, we are going to be seeing a lot in coming years in terms of variability in both M87* and Sag A*! Black holes are not static creatures that never change, and over the years the picture of what one looks like will change over months and years. Right now, plans are underway to construct the next generation Event Horizon Telescope (ngEHT), which will build new telescopes just for EHT work to get even better resolution. The hope is you'll get snapshots of these black holes every few weeks/months, and be able to watch their evolution like a YouTube video to then run tests on things like general relativity. That is going to be fantastic and I can't wait to see it!

TL;DR- we now have a polarized picture of the black hole at the center of the Milky Way, which indicates there might be a hidden jet. Black holes are awesome!!!

Fitzy Fitz posted:

y'all read this?

https://zenodo.org/records/8213330

sharknado slashfic posted:

Maybe that's why the asterisk in the title

Orbs posted:

J'accusation disk!!!

sharknado slashfic posted:

mediaphage posted:

lol

the dreyfufos affair

Al! posted:

ring

Hatebag posted:

toggle posted:

i love this gif because it reminds me how insignificant humans are

sharknado slashfic posted:

Fitzy Fitz posted:

pretty cool that we may have a case of verified communication in that story

UwUnabomber posted:

I won a giveaway from an artist and he asked how I felt about Weekly World News and then mailed me this.

Spergin Morlock posted:

either that or it was a legit black project craft that was squawking valid IFF codes

sharknado slashfic posted:

Sleekly posted:

yeah that picture is beautiful

helta posted:

Going 6200 miles an hour though? I left out the year of the quote... 1957.

Nuclearmonkee posted:

UwUnabomber posted:

I won a giveaway from an artist and he asked how I felt about Weekly World News and then mailed me this.

Rudeboy Detective posted:

I'm pretty sure any culture advanced enough to stride between the stars probably uses Arch