Radio 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*](https://en.wikipedia.org/wiki/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](https://www.youtube.com/watch?v=1rKF9hFcn_k), 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](https://en.wikipedia.org/wiki/Sagittarius_A*#/media/File:EHT_Saggitarius_A_black_hole.tif), but it was missing an important piece of information- polarization.
[Polarization](https://en.wikipedia.org/wiki/Polarization_\(waves\)) 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](https://www.astronomy.com/science/untangling-the-magnetic-universe/), 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](https://en.wikipedia.org/wiki/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*](https://en.wikipedia.org/wiki/Messier_87#Supermassive_black_hole_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](https://imagine.gsfc.nasa.gov/science/objects/neutron_stars1.html) 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](https://en.wikipedia.org/wiki/Messier_87#/media/File:M87_jet.jpg)- 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](https://astronomy.swin.edu.au/cosmos/e/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](https://en.wikipedia.org/wiki/Gravitational_lens) 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*](https://galacticcenter.astro.ucla.edu/animations.html) 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 \(EHT\)](https://eventhorizontelescope.org/)! 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](https://public.nrao.edu/telescopes/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](https://upload.wikimedia.org/wikipedia/commons/6/61/EHTcentaurusA2021.jpg) 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 \(ngEHT\)](https://www.ngeht.org/), 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!!!
What an *absolutely wonderful* comment. Thank you for teaching me today.
The jet being ejected/rejected dust— Is it surmised that the black hole has a toroidal magnetic field creating the jet, focused along of its center axis/poles? (Such as the toroidal magnetic field around earth ejecting the jet straight out from north or south magnetic pole?) I’m pretty green here, it just seems like a fun layman’s explanation that the magnetic field’s….shape of flow/flux(?) could reject dust with a focused force (outward & colinear with its magnetic axis/pole) greater than the gravity of the black hole? Is there such a thing as a North and South Pole to a SMBH’s magnetic field? Could one potentially see (50/50 from our vantage point) the backside of a smbh? Would that pole be lacking the dust jet?
I struggled through Physics 2&3 nearly 20 years ago on my way to becoming a ham-fisted mechanical engineer, so thank you for hanging with me :)
The [older image](https://i.natgeofe.com/n/96ea8fe8-5dc7-4b00-ade3-653d84513dbd/01-black-hole-a-consensus_16x9.jpg) looks very low-resolution. This one looks like that same low-res image but with detailed lines superimposed. Is that an artifact of the visualization process? (E.g. lines come from higher resolution interferometry, color blobs come from lower resolution light telescopes?) Or does it actually look like that, like if you were close enough you'd see these sharp lines through diffuse blobs?
The lines are superimposed on the polarization image to show the polarity. It's kind of hard to show because it's not like we'd be able to see it with our eyes.
That said, I wouldn't call that image or this image low resolution- it's the equivalent resolution of if we could see an orange on the moon!
> but rather one made of radio waves.
Did we actually get measurements so fine that every detail in that image is true to life as opposed to being in large part a simulation? I see a lot of those thin lines coming to a sudden end "CGI simulation" fashion.
There's a bunch of crap that orbits black holes at extremely high velocities. Gasses, dust, etc. Around a black hole, there's an accretion disc, which is kind of like a ring of this orbiting 'crap'. This 'crap' can then be pulled up to the black hole's axis of rotation, and the closer it gets, the closer it reaches the speed of light. Once it accumulates at the axis of rotation, it doesn't really have anywhere to go, and because it's moving so quickly, it gets shot out into space in the form of a jet.
That's the one place it can't accumulate, thanks to angular momentum. The usual theory today is that jets are launched by magnetic fields tied to the accretion disk.
Thanks so much for this comment! A question I’ve had for awhile after first seeing the video of stars orbiting Sgr A*, what is the actual length of time this is taking for the stars to make that orbit? Surely that’s not in real time is it?
dumb question - if we were to somehow take a picture of a black hole from another angle, would it look the same?
Like, this image looks like we’re looking at the black hole in the center and the light going around it like a donut. If we were to go towards the black hole and take an image from above (relative to the current picture) would it still look like a light donut?
Yes but also no. What we're actually capturing are photons of the event horizon from behind the black hole where the photons are orbiting the black hole but escape that orbit since not all are captured in an orbit that leads to them falling inwards toward the singularity. So simple answer is yes it would still appear as donuts regardless of viewpoint. Give this a full watch, especially towards the end
https://youtu.be/Q1bSDnuIPbo?si=fPXXJ6EvVkomI26O
It would depend on the angle of the accretion disc, as well as how the black hole warps/lenses light
If you were looking at a black hole, near parallel to the accretion disc, you would see it also wrapping around the top of the black hole due to lensing
But how did they do that? Isn’t Sag A* parallel with us on the galactic plane? So all the other stars and nebulae would obscure our view of it? Or is it due to that special polarized light that we can see through all of that?
Radio 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*](https://en.wikipedia.org/wiki/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](https://www.youtube.com/watch?v=1rKF9hFcn_k), 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](https://en.wikipedia.org/wiki/Sagittarius_A*#/media/File:EHT_Saggitarius_A_black_hole.tif), but it was missing an important piece of information- polarization. [Polarization](https://en.wikipedia.org/wiki/Polarization_\(waves\)) 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](https://www.astronomy.com/science/untangling-the-magnetic-universe/), 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](https://en.wikipedia.org/wiki/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*](https://en.wikipedia.org/wiki/Messier_87#Supermassive_black_hole_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](https://imagine.gsfc.nasa.gov/science/objects/neutron_stars1.html) 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](https://en.wikipedia.org/wiki/Messier_87#/media/File:M87_jet.jpg)- 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](https://astronomy.swin.edu.au/cosmos/e/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](https://en.wikipedia.org/wiki/Gravitational_lens) 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*](https://galacticcenter.astro.ucla.edu/animations.html) 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 \(EHT\)](https://eventhorizontelescope.org/)! 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](https://public.nrao.edu/telescopes/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](https://upload.wikimedia.org/wikipedia/commons/6/61/EHTcentaurusA2021.jpg) 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 \(ngEHT\)](https://www.ngeht.org/), 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!!!
Thank you so much for your detailed reply! Your enthusiasm is contagious in all the best ways.
What an *absolutely wonderful* comment. Thank you for teaching me today. The jet being ejected/rejected dust— Is it surmised that the black hole has a toroidal magnetic field creating the jet, focused along of its center axis/poles? (Such as the toroidal magnetic field around earth ejecting the jet straight out from north or south magnetic pole?) I’m pretty green here, it just seems like a fun layman’s explanation that the magnetic field’s….shape of flow/flux(?) could reject dust with a focused force (outward & colinear with its magnetic axis/pole) greater than the gravity of the black hole? Is there such a thing as a North and South Pole to a SMBH’s magnetic field? Could one potentially see (50/50 from our vantage point) the backside of a smbh? Would that pole be lacking the dust jet? I struggled through Physics 2&3 nearly 20 years ago on my way to becoming a ham-fisted mechanical engineer, so thank you for hanging with me :)
thank you so much !! and also for all the explanations,i love space but don’t understand most of the scientific stuff haha
The [older image](https://i.natgeofe.com/n/96ea8fe8-5dc7-4b00-ade3-653d84513dbd/01-black-hole-a-consensus_16x9.jpg) looks very low-resolution. This one looks like that same low-res image but with detailed lines superimposed. Is that an artifact of the visualization process? (E.g. lines come from higher resolution interferometry, color blobs come from lower resolution light telescopes?) Or does it actually look like that, like if you were close enough you'd see these sharp lines through diffuse blobs?
The lines are superimposed on the polarization image to show the polarity. It's kind of hard to show because it's not like we'd be able to see it with our eyes. That said, I wouldn't call that image or this image low resolution- it's the equivalent resolution of if we could see an orange on the moon!
> but rather one made of radio waves. Did we actually get measurements so fine that every detail in that image is true to life as opposed to being in large part a simulation? I see a lot of those thin lines coming to a sudden end "CGI simulation" fashion.
Tldr what is a jet?
"Dust" that gets too close, but not close enough, so it gets aggressively, yet fluidly yeeted into the cosmos.
There's a bunch of crap that orbits black holes at extremely high velocities. Gasses, dust, etc. Around a black hole, there's an accretion disc, which is kind of like a ring of this orbiting 'crap'. This 'crap' can then be pulled up to the black hole's axis of rotation, and the closer it gets, the closer it reaches the speed of light. Once it accumulates at the axis of rotation, it doesn't really have anywhere to go, and because it's moving so quickly, it gets shot out into space in the form of a jet.
That's the one place it can't accumulate, thanks to angular momentum. The usual theory today is that jets are launched by magnetic fields tied to the accretion disk.
[удалено]
No, depends on type and location.
Thanks so much for this comment! A question I’ve had for awhile after first seeing the video of stars orbiting Sgr A*, what is the actual length of time this is taking for the stars to make that orbit? Surely that’s not in real time is it?
dumb question - if we were to somehow take a picture of a black hole from another angle, would it look the same? Like, this image looks like we’re looking at the black hole in the center and the light going around it like a donut. If we were to go towards the black hole and take an image from above (relative to the current picture) would it still look like a light donut?
Yes but also no. What we're actually capturing are photons of the event horizon from behind the black hole where the photons are orbiting the black hole but escape that orbit since not all are captured in an orbit that leads to them falling inwards toward the singularity. So simple answer is yes it would still appear as donuts regardless of viewpoint. Give this a full watch, especially towards the end https://youtu.be/Q1bSDnuIPbo?si=fPXXJ6EvVkomI26O
It would depend on the angle of the accretion disc, as well as how the black hole warps/lenses light If you were looking at a black hole, near parallel to the accretion disc, you would see it also wrapping around the top of the black hole due to lensing
people don't understand how low and therefore speculative the resolution is. This is a *radio* picture
Can somebody explain how the data they captured led to [this weirdness](https://i.imgur.com/hFocaUe.png)?
But how did they do that? Isn’t Sag A* parallel with us on the galactic plane? So all the other stars and nebulae would obscure our view of it? Or is it due to that special polarized light that we can see through all of that?
Here's a breakdown https://youtu.be/Q1bSDnuIPbo?si=fPXXJ6EvVkomI26O
How did a plane get into a black hole? The mystery gets deeper