Astronomers detect a black hole on the move | Hacker News Reader

Astronomers detect a black hole on the move

phys.org

94 pointsdnetesn26 comments

The academic article's abstract explains the research better: > We present the results from an observing campaign to confirm the peculiar motion of the supermassive black hole (SMBH) in J0437+2456 first reported in Pesce et al. Deep observations with the Arecibo Observatory have yielded a detection of neutral hydrogen (H i) emission, from which we measure a recession velocity of 4910 km s−1 for the galaxy as a whole. We have also obtained near-infrared integral field spectroscopic observations of the galactic nucleus with the Gemini North telescope, yielding spatially resolved stellar and gas kinematics with a central velocity at the innermost radii (0farcs1 ≈ 34 pc) of 4860 km s−1. Both measurements differ significantly from the ~4810 km s−1 H2O megamaser velocity of the SMBH, supporting the prior indications of a velocity offset between the SMBH and its host galaxy. However, the two measurements also differ significantly from one another, and the galaxy as a whole exhibits a complex velocity structure that implies that the system has recently been dynamically disturbed. These results make it clear that the SMBH is not at rest with respect to the systemic velocity of the galaxy, though the specific nature of the mobile SMBH—i.e., whether it traces an ongoing galaxy merger, a binary black hole system, or a gravitational-wave recoil event—remains unclear. [1]

Specifically, I was interested in how they measured the galactic velocity vs the SMBH velocity. It turns out that they have 3 velocity measures:

- galaxy as a whole recession velocity of 4910 km s−1

- center of the galaxy (specifically central velocity at the innermost radii (0farcs1 ≈ 34 pc)) of 4860 km s−1

- SMBH velocity: ~4810 km s−1

These 3 numbers differ enough from each other that it opens more questions than it answers. As the authors note, "system has recently been dynamically disturbed" but it could be explained by several possibilities including:

- an ongoing galaxy merger

- a binary black hole system

- a gravitational-wave recoil event

I love how as we get more precise measurements of all these moving bodies / systems, we will be able to piece together exactly the causes of things.

[1] https://iopscience.iop.org/article/10.3847/1538-4357/abde3d

More new science helped by Arecibo. RIP.

that made me realise that galaxies are moving. Which means that we already knew that Black Holes move?

Everything is in constant motion all the time. There's no universal "rest" reference frame although we commonly use the CMB as one for our purposes.

The interesting issue here is that the black hole seems to be moving relative to its own galaxy, which is unusual.

One day we might see an article like this, marking the beginning of the end.

Looking back 1y+ I wouldn't have thought that something so life altering was about to happen, yet it did. I remember news stories about a respiratory illness but didn't think much of it. Now I often read news stories, hoping that that's not going to be the next headline I don't think much of of, but will think back to in a year's time as something horrible that has happened.

black holes are capturing imagination because of scale and many other reasons, but their danger just not worth to even discuss. Space is empty and time is slow.

famous last words

re/ black holes, probably, maybe

> Space is empty and time is slow

Not always slow, and the paths of objects in space are largely determined. Thus we do have interesting and potentially useful efforts like this:

https://www.nasa.gov/planetarydefense/overview

The closest known black hole to Earth is 1000 lightyears away, so it's probably not much of a risk.

We just need these things to start growing exponentially.

As far as we know so far, there's still no way around the universal speed limit.

Wormholes and such

And the sleeping idiot-god at the center of everything could wake up, thus ending the universe. Same difference.

One is possible based in science, the other...possibly based in science. I was just saying that it is possible, not that it is probable.

You're unlikely to get exponential uncontrolled growth of that sort using wormholes, anyway. It's generally considered that any wormholes arranged in such a way as to enable causality-violating space-time paths (which is likely if there's a lot of them and they're being flung around with black holes) would immediately collapse. Not that there's any clear mechanism for how a wormhole could form, anyway.

CfA has been hitting it out of the park lately.

https://www.chandra.harvard.edu/press/21_releases/press_0309...

Maybe, if we were in a black hole we wouldn't know, and it would take an infinite amount of time to reach the event horizon.

very frightening and uneasy stuff to think about

I had the same thought a few weeks ago. Super unsettling.

It also made me wonder, if the center of a black hole is blindingly white, what if that’s where our souls are pulled to when we die?

isn’t it equally as likely our souls float up a dog’s butt or something

How is it white, no light is able to go in direction from the center even after crossing event horizon (if that even possible to do mantaining ability to observe anything)

If you're in a space ship and you pass the event horizon- well, what passing the event horizon means is that your light cone has tilted such that the centre of the black hole is in your future, not some distance away in space. So from your point of view, it isn't that there's a direction in space light can't come from- you can potentially see things in all directions- it's just that your definition of space and time have changed such that the singularity isn't 1 kilometer away, it's 20 minutes away. But otherwise (ignoring your destruction due to growing tidal forces) things on your spaceships work normally-ish.

Why would that be frightening? Everything we care about and can observe is obviously inside the black hole with us. Being inside a black hole wouldn't change the price of bread.

You should be able to observe the outside of the event horizon from the inside.

“In a black hole” ... maybe you mean you’ve already crossed the point of no return but not yet hit the singularity...

Eh, forgive me but also, an outside observer would say it takes an infinite amount of time for you to hit the event horizon, (and get smeared and red-shifted to nothing on it), but the in-falling frame of reference passes through the horizon as quick as any other point.

Now is the entire universe a black hole in some sense? Perhaps, but in pondering such a case I find it is no more terrifying, majestic, mysterious, and awe inspiring when contemplated that way than any other.

How could we not know? Our own light would hurdle towards the singularity, let alone our mass.

Reply on news.ycombinator.com