<p>Photos of the <a href="https://en.wikipedia.org/wiki/Galactic_Center" rel="nofollow noreferrer">galactic center</a> aren't too bright because of all the gas and dust between us and it. <a href="https://upload.wikimedia.org/wikipedia/commons/1/11/Galactic_Cntr_full_cropped.jpg" rel="nofollow noreferrer">For example</a> (in infrared):</p>

<p><img src="https://upload.wikimedia.org/wikipedia/commons/1/11/Galactic_Cntr_full_cropped.jpg" alt="Galactic center"></p>

<p>I'm guessing, though, that you're talking about other galaxies, because there are no views of the galactic center of the Milky Way face-on. Although the galactic center is pretty luminous, just not in the wavelengths we're used to.</p>

<p>Anyway, the galactic center has lots of stars - many massive, but a handful like our Sun. They're young, though, which is odd, as there isn't much star formation happening.</p>

<p>The main attraction, though, is <a href="https://en.wikipedia.org/wiki/Sagittarius_A*" rel="nofollow noreferrer">Sagittarius A*</a>, a radio source that is apparently a <a href="https://en.wikipedia.org/wiki/Supermassive_black_hole" rel="nofollow noreferrer">supermassive black hole</a>. It's actually a subset of the more complex radio source <a href="https://en.wikipedia.org/wiki/Sagittarius_A" rel="nofollow noreferrer">Sagittarius A</a>. So far, astronomers think that most galaxies have supermassive black holes in their centers.</p>

<p>We know that it has to be really massive because of how it perturbs the <a href="https://upload.wikimedia.org/wikipedia/commons/c/c1/Galactic_centre_orbits.svg" rel="nofollow noreferrer">orbits of stars nearby</a>:</p>

<p><img src="https://upload.wikimedia.org/wikipedia/commons/thumb/c/c1/Galactic_centre_orbits.svg/1000px-Galactic_centre_orbits.svg.png" alt="Star orbits near Sagittarius A*"></p>

<p>We know it's massive and we know it's a very strong radio source. A supermassive black hole is just about the only thing it could be.</p>

<p>Courtesy of WayfaringStranger: <a href="https://apod.nasa.gov/apod/ap130906.html" rel="nofollow noreferrer">An awesome picture from NASA</a>:</p>

<p><img src="https://apod.nasa.gov/apod/image/1309/sgra_gasChandra.jpg" alt="Awesome picture from NASA"></p>

<p>In <a href="http://arxiv.org/pdf/0808.2870v1.pdf" rel="nofollow noreferrer">this paper</a> by Ghez et al., the orbits of stars were monitored and a mass of the central object was determined to be $4.1 \pm 0.6 \times 10^6 M_{\odot}$. <a href="http://www.aanda.org/articles/aa/pdf/2009/28/aa10922-08.pdf" rel="nofollow noreferrer">This</a> paper discusses the properties of the star cluster itself.</p>

CC BY-SA 3.0
2015-01-17T15:18:23.947Z
APOD with X-ray emissions: http://apod.nasa.gov/apod/ap130906.html
Wayfaring Stranger
CC BY-SA 3.0
2015-01-17T15:20:04.573Z
@WayfaringStranger Thanks; I've added that in. Sort of.
HDE 226868
CC BY-SA 3.0
2015-01-17T21:37:40.507Z
You could give the mass and a reference to a paper that determines it...
ProfRob
CC BY-SA 3.0
2015-01-17T21:46:20.583Z
@RobJeffries I'll see if I can find one.
HDE 226868
CC BY-SA 3.0
2015-01-17T21:53:21.497Z
@RobJeffries Got it.
HDE 226868
CC BY-SA 3.0
2015-01-18T00:54:03.457Z
Why isn't the supermassive black hole on the major axis (and on one of the two foci) of ***all*** those ellipses?
Peter Mortensen
CC BY-SA 3.0
2015-01-18T01:04:22.933Z
@PeterMortensen I don't have a good answer, but I know that there's more matter in the area than just the black hole, so it's not the only influence.
HDE 226868
CC BY-SA 3.0
2015-01-18T02:56:06.257Z
Nasa doesn't generally copyright their material. ["NASA still images; audio files; video; and computer files used in the rendition of 3-dimensional models, such as texture maps and polygon data in any format, generally are not copyrighted."](http://www.nasa.gov/multimedia/guidelines/index.html) Your tax dollars at work!
blahdiblah
CC BY-SA 3.0
2015-01-18T03:53:33.513Z
@HDE 226868: Perhaps due to uncertainty in the measurements - difficulty of extrapolation?
Peter Mortensen
CC BY-SA 3.0
2015-01-18T05:20:16.623Z
@PeterMortensen: Perspective. When an ellipse is seen from a direction not perpendicular to its plane, the image is still an ellipse (in the picture plane), but the axes and foci of the image ellipse are not the image of the axes and foci of the original ellipse.
hmakholm left over Monica
CC BY-SA 3.0
2015-01-17T15:17:12.993Z
2015-01-18T20:25:25.027Z
2017-03-10T09:42:47.307Z
HDE 226868
<p>It's big. It's bright. It's white. It's so intense. But what is at the center of the Milky Way?</p>

CC BY-SA 3.0
2015-01-17T21:56:45.650Z
Its not white and intense. You might get away with saying its really intense in the infrared, but we can't see it at optical wavelengths.
ProfRob
CC BY-SA 3.0
2015-01-18T01:04:09.863Z
God, if you believe [a bad sci-fi movie](https://www.youtube.com/watch?v=QkT1-N0VqUc).
Schwern
CC BY-SA 3.0
2015-01-18T05:38:38.157Z
Super massive black hole sounds more realistic :P
Ero Sɘnnin
<galaxy><milky-way>
What is supposedly in the center of the Milky Way?
Ero Sɘnnin
# What is supposedly in the center of the Milky Way?

(Asked by: username_0 on 2015-01-17)

It's big. It's bright. It's white. It's so intense. But what is at the center of the Milky Way?

**Tags:** galaxy, milky-way

> **Comments:**
> **username_1**: Its not white and intense. You might get away with saying its really intense in the infrared, but we can't see it at optical wavelengths.  
> **username_2**: God, if you believe [a bad sci-fi movie](https://www.youtube.com/watch?v=QkT1-N0VqUc).  
> **username_0**: Super massive black hole sounds more realistic :P  

---

## 1 answers

### Answer by username_3 on 2015-01-17. Score: 15 | Accepted answer

Photos of the [galactic center](https://en.wikipedia.org/wiki/Galactic_Center) aren't too bright because of all the gas and dust between us and it. [For example](https://upload.wikimedia.org/wikipedia/commons/1/11/Galactic_Cntr_full_cropped.jpg) (in infrared):

![Galactic center](https://upload.wikimedia.org/wikipedia/commons/1/11/Galactic_Cntr_full_cropped.jpg)

I'm guessing, though, that you're talking about other galaxies, because there are no views of the galactic center of the Milky Way face-on. Although the galactic center is pretty luminous, just not in the wavelengths we're used to.

Anyway, the galactic center has lots of stars - many massive, but a handful like our Sun. They're young, though, which is odd, as there isn't much star formation happening.

The main attraction, though, is [Sagittarius A\*](https://en.wikipedia.org/wiki/Sagittarius_A*), a radio source that is apparently a [supermassive black hole](https://en.wikipedia.org/wiki/Supermassive_black_hole). It's actually a subset of the more complex radio source [Sagittarius A](https://en.wikipedia.org/wiki/Sagittarius_A). So far, astronomers think that most galaxies have supermassive black holes in their centers.

We know that it has to be really massive because of how it perturbs the [orbits of stars nearby](https://upload.wikimedia.org/wikipedia/commons/c/c1/Galactic_centre_orbits.svg):

![Star orbits near Sagittarius A*](https://upload.wikimedia.org/wikipedia/commons/thumb/c/c1/Galactic_centre_orbits.svg/1000px-Galactic_centre_orbits.svg.png)

We know it's massive and we know it's a very strong radio source. A supermassive black hole is just about the only thing it could be.

Courtesy of username_4: [An awesome picture from NASA](https://apod.nasa.gov/apod/ap130906.html):

![Awesome picture from NASA](https://apod.nasa.gov/apod/image/1309/sgra_gasChandra.jpg)

In [this paper](http://arxiv.org/pdf/0808.2870v1.pdf) by Ghez et al., the orbits of stars were monitored and a mass of the central object was determined to be $4.1 \pm 0.6 \times 10^6 M\_{\odot}$. [This](http://www.aanda.org/articles/aa/pdf/2009/28/aa10922-08.pdf) paper discusses the properties of the star cluster itself.

> **Comments:**
> **username_4**: APOD with X-ray emissions: http://apod.nasa.gov/apod/ap130906.html  
> **username_3**: @username_4 Thanks; I've added that in. Sort of.  
> **username_1**: You could give the mass and a reference to a paper that determines it...  
> **username_3**: @RobJeffries I'll see if I can find one.  
> **username_3**: @RobJeffries Got it.  
> **username_5**: Why isn't the supermassive black hole on the major axis (and on one of the two foci) of ***all*** those ellipses?  
> **username_3**: @username_5 I don't have a good answer, but I know that there's more matter in the area than just the black hole, so it's not the only influence.  
> **username_6**: Nasa doesn't generally copyright their material. ["NASA still images; audio files; video; and computer files used in the rendition of 3-dimensional models, such as texture maps and polygon data in any format, generally are not copyrighted."](http://www.nasa.gov/multimedia/guidelines/index.html) Your tax dollars at work!  
> **username_5**: @username_3: Perhaps due to uncertainty in the measurements - difficulty of extrapolation?  
> **username_7**: @username_5: Perspective. When an ellipse is seen from a direction not perpendicular to its plane, the image is still an ellipse (in the picture plane), but the axes and foci of the image ellipse are not the image of the axes and foci of the original ellipse.  

---

