Another intermediate-mass black hole discovered at the centre of our galaxy | Hacker News Reader

Another intermediate-mass black hole discovered at the centre of our galaxy

portal.uni-koeln.de

90 pointscroes16 comments

The problem I have with this article is that it doesn't list the estimated mass.

You need to go to the paper's abstract to see that it's around 30,000 times the mass of the sun (∼3 × 10^4M⊙). For context Sag A* (the supermassive black hole at the center of the Milky Way) is about 4.1 Million times the mass of the sun.

There are more major issues I would hope the article authors would correct. I know, not likely to happen. Here's a few notes to think about -

> The analysed star cluster IRS 13 is located 0.1 light years from the centre of our galaxy. This is very close in astronomical terms, but would still require travelling from one end of our solar system to the other twenty times to cover the distance.

If the "one end to the other" metric, at best, is 2 x 100,000 AU [1] if it means the edge of the Oort cloud. That's about 3.16 light-years.

But GCIRS 13E appears to be 26,000 light-years away. Hint: 3.16 light-years x 20 is not even close to 26,000 light-years.

The article never mentions any theories on the formation of these intermediate-mass black holes, or why confirming the existence of one in our own galaxy would be meaningful science.

[1] https://en.wikipedia.org/wiki/Oort_cloud

[2] https://en.wikipedia.org/wiki/GCIRS_13E

> But GCIRS 13E appears to be 26,000 light-years away. Hint: 3.16 light-years x 20 is not even close to 26,000 light-years.

The article isn't describing how far away from Earth IRS 13 is. It's describing how far from the galactic center it is (0.1 light-year, not 26,000 light-years).

To help narrow down what the author is referring to by "one end of our solar system to the other", one can divide 0.1 light-year by 20 to get 0.005 light-year, which is about 316 AU. I'm going to assume th⁹at the reference is to the heliosphere, then, since it's apparently about 300 AU across:

"The Sun's stellar-wind bubble, the heliosphere, a region of space dominated by the Sun, has its boundary at the termination shock. Based on the Sun's peculiar motion relative to the local standard of rest, this boundary is roughly 80–100 AU from the Sun upwind of the interstellar medium and roughly 200 AU from the Sun downwind."[1]

[1] https://en.wikipedia.org/wiki/Solar_System

My understanding is that the formation of intermediate mass black holes is pretty mysterious. In principle you could get those and the supermassive from stellar mass black holes colliding but in practice it takes more time than they’ve had.

For a system this small and a black hole this big, the smoking gun evidence would be a time lapse showing the stars orbiting a point with “nothing” there.

The evidence they presented in the paper is mostly circumstantial — essentially a statistical analysis.

We have this video for Sagittarius A* : https://www.eso.org/public/videos/eso1825e/

I’m guessing that in a few years we’ll have a similar video of this area too.

> the researchers were able to observe characteristic X-rays and ionized gas rotating at a speed of several 100 km/s in a ring around the suspected location of the intermediate-mass black hole.

That's a little better than circumstantial.

Does that confirm the size of the black hole, or is it just a "strong hint"?

Fair, I have no idea if it confirms the size, though maybe the specific speed of the gas helps with that. Mostly it's evidence that there is a black hole, but it's not supermassive, and a stellar-mass one probably wouldn't have enough effect to be noticed.

You can determine the mass of something by measuring the time it takes for an orbit around it, yes.

You need the orbital radius, too.

Yep. You can get both from observations of the orbiting object.

That's the issue with timelapse of this scale. It takes many years to get a good look at it. Even in the video you linked took 20 years.

The closest approaching star found so far is estimated to be traveling at 8% of the speed of light at closest approach.

Which is enough to cause severe relativistic precession of the orbital major/minor axes! (Schwarzschild precession)

Is that gravitational lensing happening at the start of the video? Upper left, flickering rings but they seem to be around a star.

Looks like a diffraction pattern to me. The way it flickers makes me think they're running some corrective algorithm that's struggling with some of the stars. (See the bottom left as well, they both appear to be bright sources and also on the edge of the field.) Also interesting to note how it seems to show up more when the image is crisper. No clue why that might be.

https://en.wikipedia.org/wiki/Airy_disk

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