# B Our galaxy hosts millions of Black Holes

1. Aug 11, 2017

### wolram

According to this article millions of Black Holes exist in our Galaxy, And within a few years mergers will be detected by Ligo,

According to Kaplinghat, they may not have to wait too long, relatively speaking. "If the current ideas about stellar evolution are right, then our calculations indicate that mergers of even 50-solar-mass black holes will be detected in a few years," he said.

https://www.sciencedaily.com/releases/2017/08/170807155403.htm

What do you think?

2. Aug 11, 2017

### Fervent Freyja

I honestly assumed that we already knew that black holes were that numerous in our galaxy. I wouldn't be surprised if there were more than that.

As far as LIGO, I have my doubts that it will produce meaningful data anytime soon- I'll probably be long gone.

I'm also thinking about what is happening to my Kindergartner in her 3rd day of school at the moment.

3. Aug 11, 2017

### phinds

A subject which is, and should be, WAY more important than black holes

4. Aug 11, 2017

### phyzguy

Umm - what? You don't consider the black hole mergers already detected by LIGO to be "meaningful"?

5. Aug 11, 2017

### George Jones

Staff Emeritus
I am not sure what you mean by this. LIGO already has produced meaningful data, and I am sure it will produce loads more meaningful data in the years to come.

When my daughter (about to start grade six), an only child, went to kindergarten, she did not want to come home at the end of the day , i.e., she wanted to stay with the other kids.

6. Aug 11, 2017

### wolram

I don:t want to be a damp squid but there has been comments that the Ligo results have a question mark against them, some thing about a lightning storm corresponding with the detection

7. Aug 11, 2017

### Staff: Mentor

We have another long thread about this "question mark" already. There's not enough there to call the LIGO results into question.

8. Aug 11, 2017

### George Jones

Staff Emeritus
The paper "On the times lags from LIGO signals"

https://arxiv.org/abs/1706.04191v2

has been accepted for publication. From the abstract:

See the discussion at
https://telescoper.wordpress.com/2017/08/10/on-the-time-lags-of-the-ligo-signals/

I suspect that this criticism will not remain viable when a detector at a third location comes on line.

9. Aug 11, 2017

### Staff: Mentor

10. Aug 11, 2017

### Fervent Freyja

Don't you know, women are master's of multi-tasking? Really though, I don't know what to do. After she got out of the first day, she informed me that one girl kept poking her in the face (over and over), another ignored her during free-play, and when she complimented one girl on her shirt, the girl got crying upset with her and said she didn't like the color of her shirt but her mother made her wear it. And, when I let her checkmate me later that afternoon, she laughed and then with her little finger pointedly called me a *loser*! I'm not kidding. My own child. Something she'd seen occur in class just on the very first day. She cried when I explained to her what it really meant. I wish I could put surveillance on her, so that I would know just exactly WHAT happened every day.

I'm not saying it cannot be used to better understand some objects in space one day or denying that smaller gravitational oscillations exist, just that there's still a possibility of misattribution and misinterpretation, stemming from long ago. If someone told me that a bird only ever sings, I'm not going to assume it can chirp, nor will force it and mistake it's last notes as a chirp. I might look at the echoes, however. We are talking about objects that we don't have real great parameters on to begin with; and so, that combined with our failure to understand the mechanics of gravity in context with the more meaningful systems we use, I just don't see how exaggerating the importance of those events get them closer to understanding very much more about the universe than a computational team armed with 10 Titan supercomputers at the same cost.

Oh, 6th grade, I bet you are in for it really soon! That's got to be the most stressful years for Dad! Sounds like you really enjoyed her early childhood, so she will probably do very well through the next few years. She will definitely need you no matter how rebellious, you are key prevention and guidance at this stage.

That does make me feel better. I figure mine will end up liking both her teacher and peers more than me.

11. Aug 11, 2017

### stoomart

Hopefully we'll pick up more detections while Virgo is online for a bit.

Here's a link to the paper on arXiv: https://arxiv.org/abs/1703.02551

Stellar-remnant black holes should be abundant in the local universe. For example, $m_\rm{bh}$ $> 30M_\odot$ black holes should have a local number density of $10^{14}~\rm{Gpc^{-3}}$ with an occupation rate of $\sim 1$ per $1000~M_\odot$ of stars formed in galaxies with $M_\star \lesssim 10^{10}~M_\odot$ (see Figures 2 and 3). These numbers are robust to within factors of $\sim 2$ for different stellar evolution codes and popular IMF choices. Such an abundant black hole population provides an ample source for binary systems that eventually merge for reasonable choices of parameters that characterize the merger process.​

Last edited: Aug 11, 2017
12. Aug 16, 2017

### Blank_Stare

Here's a fun fact for you. If you assist a butterfly to exit it's cocoon, by peeling away the shell for it, it will be unlikely to ever fly. The very act of escaping that tiny prison causes the wings to develop into strong, flight capable appendages.

Your daughter will grow in her own ways, and do it better, if some of the crap that she deals with everyday stays exclusively hers. She'll let you know when there are "big issues" that require adult intervention.

Give her a hug for me.

13. Aug 16, 2017

### snorkack

What is the likely distance from Sun to nearest black hole?
How visible is a solitary black hole travelling at high speed through tenuous interstellar matter?

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