<p>A query to the <a href="https://gea.esac.esa.int/archive/" rel="noreferrer">Gaia Archive</a> within 6 arc min of target name M51 finds 20 sources with phot_g_mean_mag &lt;= 17.
<a href="http://aladin.unistra.fr/AladinLite/?target=13%2029%2052.698%2B47%2011%2042.93&amp;fov=0.37&amp;survey=P%2FPanSTARRS%2FDR1%2Fcolor-z-zg-g" rel="noreferrer">Aladin Lite</a> helps to locate them visually.
Five are circled in the lower half of the image in question:</p>
<div class="s-table-container">
<table class="s-table">
<thead>
<tr>
<th>Gaia source_id</th>
<th style="text-align: right;">ra °</th>
<th style="text-align: right;">dec °</th>
<th style="text-align: right;">parallax (mas)</th>
<th style="text-align: right;">mag<sub>g</sub></th>
</tr>
</thead>
<tbody>
<tr>
<td>1551894661845524736</td>
<td style="text-align: right;">202.4034</td>
<td style="text-align: right;">47.1522</td>
<td style="text-align: right;">8.854 ± 0.017</td>
<td style="text-align: right;">14.3</td>
</tr>
<tr>
<td>1551988532650838016</td>
<td style="text-align: right;">202.4205</td>
<td style="text-align: right;">47.1790</td>
<td style="text-align: right;">2.387 ± 0.041</td>
<td style="text-align: right;">16.4</td>
</tr>
<tr>
<td>1551988670089792256</td>
<td style="text-align: right;">202.4236</td>
<td style="text-align: right;">47.1979</td>
<td style="text-align: right;">0.632 ± 0.025</td>
<td style="text-align: right;">15.1</td>
</tr>
<tr>
<td>1551988425277200640</td>
<td style="text-align: right;">202.4323</td>
<td style="text-align: right;">47.1537</td>
<td style="text-align: right;">0.813 ± 0.025</td>
<td style="text-align: right;">15.2</td>
</tr>
<tr>
<td>1551988567010595840</td>
<td style="text-align: right;">202.4417</td>
<td style="text-align: right;">47.1800</td>
<td style="text-align: right;">1.536 ± 0.012</td>
<td style="text-align: right;">13.3</td>
</tr>
</tbody>
</table>
</div>
<p>These parallaxes indicate distances between 113 and 1600 parsecs, well within the Milky Way.</p>
<p>Of the three sources circled in the upper half, two seem to be listed in Gaia EDR3 but do not have good parallaxes there.
Aladin Lite shows <a href="http://simbad.u-strasbg.fr/simbad/sim-ref?bibcode=2008AJ....135.1567H" rel="noreferrer">SIMBAD</a> matches near all three in
<a href="https://ui.adsabs.harvard.edu/abs/2008AJ....135.1567H/abstract" rel="noreferrer">Hwang and Lee 2008</a>, a catalog of 2200 star clusters in M51.</p>
<div class="s-table-container">
<table class="s-table">
<thead>
<tr>
<th>HL2008 id</th>
<th style="text-align: right;">ra °</th>
<th style="text-align: right;">dec °</th>
<th style="text-align: right;">mag<sub>V</sub></th>
<th>Gaia source_id</th>
</tr>
</thead>
<tbody>
<tr>
<td>89770</td>
<td style="text-align: right;">202.494</td>
<td style="text-align: right;">47.216</td>
<td style="text-align: right;">20.0</td>
<td>1551988944968489984</td>
</tr>
<tr>
<td>13162</td>
<td style="text-align: right;">202.505</td>
<td style="text-align: right;">47.154</td>
<td style="text-align: right;">21.1</td>
<td>--</td>
</tr>
<tr>
<td>28066</td>
<td style="text-align: right;">202.531</td>
<td style="text-align: right;">47.167</td>
<td style="text-align: right;">19.8</td>
<td>1551987909882986368</td>
</tr>
</tbody>
</table>
</div>
CC BY-SA 4.0
2021-03-25T20:03:55.580Z
2021-03-25T20:03:55.580Z
Mike G
<p>I saw this picture of M51 (Whirlpool galaxy) and noticed many, many bright dots around and in the galaxy. I have freehand-circled a few as examples. Are these individual stars (probably supergiants) in the Whirlpool Galaxy, or are they clusters, stars in the Milky Way, or something else?</p>
<p><a href="https://i.sstatic.net/p4hnZ.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/p4hnZ.jpg" alt="Potential stars" /></a>
<br/><em>Source: <a href="https://esahubble.org/images/heic0506a/" rel="nofollow noreferrer">ESA/Hubble</a></em></p>

CC BY-SA 4.0
2021-03-23T22:16:49.030Z
You noticed a red object on the lower left of the image, which excludes clusters. I would suspect they are foreground stars. You could check their positions in any astronomical positioning database, or the free Stellarium app.
AtmosphericPrisonEscape
CC BY-SA 4.0
2021-03-23T23:40:20.077Z
I just opened Stellarium and I could relate most to a foreground star. That doesn't mean the others aren't foreground stars either. It's not completely impossible that they're very bright stars like Cepheids in M51, too.
planetmaker
CC BY-SA 4.0
2021-03-24T12:23:37.177Z
Some of them have a distinct diffraction cross, so likely foreground stars. Some are more diffused, could they be clusters of Whirlpool?
Alchimista
<star><galaxy><milky-way><identify-this-object><nebula>
Are the bright dots in this image individual stars?
slowerthanstopped
# Are the bright dots in this image individual stars?

(Asked by: username_0 on 2021-03-23)

I saw this picture of M51 (Whirlpool galaxy) and noticed many, many bright dots around and in the galaxy. I have freehand-circled a few as examples. Are these individual stars (probably supergiants) in the Whirlpool Galaxy, or are they clusters, stars in the Milky Way, or something else?

[![Potential stars](https://i.sstatic.net/p4hnZ.jpg)](https://i.sstatic.net/p4hnZ.jpg)
  
*Source: [ESA/Hubble](https://esahubble.org/images/heic0506a/)*

**Tags:** star, galaxy, milky-way, identify-this-object, nebula
> **Comments:**
> **username_1**: You noticed a red object on the lower left of the image, which excludes clusters. I would suspect they are foreground stars. You could check their positions in any astronomical positioning database, or the free Stellarium app.  
> **username_2**: I just opened Stellarium and I could relate most to a foreground star. That doesn't mean the others aren't foreground stars either. It's not completely impossible that they're very bright stars like Cepheids in M51, too.  
> **username_3**: Some of them have a distinct diffraction cross, so likely foreground stars. Some are more diffused, could they be clusters of Whirlpool?  

---

## 1 answers

### Answer by username_4 on 2021-03-25. Score: 5 | Accepted answer

A query to the [Gaia Archive](https://gea.esac.esa.int/archive/) within 6 arc min of target name M51 finds 20 sources with phot\_g\_mean\_mag <= 17.
[Aladin Lite](http://aladin.unistra.fr/AladinLite/?target=13%2029%2052.698%2B47%2011%2042.93&fov=0.37&survey=P%2FPanSTARRS%2FDR1%2Fcolor-z-zg-g) helps to locate them visually.
Five are circled in the lower half of the image in question:

| Gaia source\_id | ra ° | dec ° | parallax (mas) | magg |
| --- | --- | --- | --- | --- |
| 1551894661845524736 | 202.4034 | 47.1522 | 8.854 ± 0.017 | 14.3 |
| 1551988532650838016 | 202.4205 | 47.1790 | 2.387 ± 0.041 | 16.4 |
| 1551988670089792256 | 202.4236 | 47.1979 | 0.632 ± 0.025 | 15.1 |
| 1551988425277200640 | 202.4323 | 47.1537 | 0.813 ± 0.025 | 15.2 |
| 1551988567010595840 | 202.4417 | 47.1800 | 1.536 ± 0.012 | 13.3 |

These parallaxes indicate distances between 113 and 1600 parsecs, well within the Milky Way.

Of the three sources circled in the upper half, two seem to be listed in Gaia EDR3 but do not have good parallaxes there.
Aladin Lite shows [SIMBAD](http://simbad.u-strasbg.fr/simbad/sim-ref?bibcode=2008AJ....135.1567H) matches near all three in
[Hwang and Lee 2008](https://ui.adsabs.harvard.edu/abs/2008AJ....135.1567H/abstract), a catalog of 2200 star clusters in M51.

| HL2008 id | ra ° | dec ° | magV | Gaia source\_id |
| --- | --- | --- | --- | --- |
| 89770 | 202.494 | 47.216 | 20.0 | 1551988944968489984 |
| 13162 | 202.505 | 47.154 | 21.1 | -- |
| 28066 | 202.531 | 47.167 | 19.8 | 1551987909882986368 |


---

