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{{short description|Open cluster in the constellation Cygnus}}
{{Infobox open cluster
| name = Messier 29
| image = [[File:Messier_29.jpg|300 px]]
| caption = Open cluster Messier 29 in Cygnus, conventionally taken (as looking at the object on the southern horizon). Very broad reddish nebulosity is noticeable to the west.
| epoch = [[J2000]]
| constellation = [[Cygnus (constellation)|Cygnus]]
| ra = {{RA|20|23|56}}<ref name=LeDuigou2002/>
| dec = {{DEC|+38|31|24}}<ref name=LeDuigou2002/>
| appmag_v = 7.1<ref>{{cite web |url=http://www.messier.seds.org/m/m029.html |title=Messier 29 |access-date=22 July 2024 |website=SEDS Messier Catalog}}</ref>
| size_v = {{Val|7.0|u=arcminute}}
| age = 13.2 Myr<ref name=kharchenko2005/>
| dist_ly = {{Convert|1608|pc|ly|order=flip|abbr=on|lk=on}}<ref name=Poggio2021/>
| mass_msol = {{Val|580|–|1090|fmt=commas}}<ref name=LeDuigou2002/>
| names = M29, [[New General Catalogue|NGC]] 6913, [[Collinder catalog|Cr]] 422, OCl 168<ref name="simbad" />
}}

'''Messier 29''' or '''M29''', also known as '''NGC 6913''' or the '''Cooling Tower Cluster''', is a quite small, bright [[open cluster]] of [[star]]s just south of the central bright star [[Gamma Cygni]] of a northerly [[constellation|zone of the sky]], [[Cygnus constellation|Cygnus]]. It was discovered by [[Charles Messier]] in 1764, and can be seen from [[Earth]] by using [[binoculars]].

M29 is well within the several degrees of the arms and bulge of the [[Milky Way]]. It is at least many hundreds of light years short of the yardstick distance to the [[Galactic Center]], as is between 4,000<ref name=kgj>Kenneth Glyn Jones (ed.) ''The Sky Catalogue 2000.0''</ref> and 7,200 [[light year]]s away.<ref>Preferred by most sources including Mallas/Kreimer and Burnham, and agreeing with early estimates or R.J. Trumpler 1930</ref> A 1998 popular work gives a value within this range.{{efn|Namely {{val|6000|u=light years}} }}<ref name=ks>Kepple, George Robert., Sanner, Glen W.. The Night Sky Observer's Guide: Spring & summer. United States: Willmann-Bell, 1998 at Chapter 42. Cygnus, The Swan</ref> Data from Gaia EDR3 gives a parallactic distance of about 5,240 light years.<ref name=Poggio2021/> The uncertainty is due to poorly known absorption of the cluster's light. Its [[extinction (astronomy)|extinction]] greatly is from faint surrounding nebulosity and other foreground [[interstellar matter]] of this cross-section of the [[spiral arm]]s (see [[Orion–Cygnus Arm]], which is our local arm).

According to the Sky Catalogue,<ref name=kgj/> M29 is included in the Cygnus OB1 association, and the radial velocity component of three-dimensional motion, by default factoring in the solar system's current trajectory, is one of approaching at 28 km/s (noted, thus, as negative). Its age is estimated at 10 million years, as its five hottest stars are all [[giant star|giants]] of spectral [[Stellar classification|class B0]]. Kepple and his associates give the apparent brightness of the brightest star as eighth magnitude of in the mid-wavelength (and frequency) [[photometric system|"visual" band]].<ref name=ks/>{{efn|Specifically at a V-band magnitude of 8.59}}

The cluster's [[absolute magnitude]] is estimated at −8.2, a luminosity of 160,000 solar luminosities ({{Lo|link=yes}}). The linear diameter was estimated at only 11 light years. Its Trumpler class is III,3,p,n (as it is associated with nebulosity), although Götz gives, differently, II,3,m, and Kepple gives I,2,m,n.<ref name=ks/> The Sky Catalogue lists it with 50 member stars;<ref name=kgj/> earlier Becvar estimated 20 members.

North of 47 degrees north, the cluster is for part or all of the day above the horizon. It can be made out in [[binoculars]] in a good sky. In telescopes, lowest powers are best. The brightest of its stars form a "stubby [[Ursa Major|dipper]]", per Mallas. The four brightest stars form a quadrilateral, and another set a small triangle just north of the northernmost of the four. It is often known as the "[[cooling tower]]" due to its resemblance to the hyperboloid-shaped structures. A few fainter stars are around them, but the cluster appears quite isolated, especially in smaller telescopes. In photographs, many faint Milky Way background stars appear.

Messier 29 can be found quite easily as it is about 1.7 degrees south{{efn|Specifically [[boxing the compass|-by-east]]}} of [[Gamma Cygni|Gamma or 37 Cygni (Sadr)]]. Angularly close, and almost certainly nearby in space, is diffuse nebulosity.

The especially hot binary Wolf–Rayet star [[WR 143]] (WC4+Be) (HD 195177) can be found near this cluster.

==See also==
* [[List of Messier objects]]

==References and footnotes==
{{Reflist|refs=

<ref name="simbad">{{cite simbad | title=M 29 | accessdate=2006-12-08 }}</ref>

<ref name=LeDuigou2002>{{citation
| title=Characteristics of new star cluster candidates in the Cygnus area
| last1=Le Duigou | first1=J. -M. | last2=Knödlseder | first2=J.
| journal=Astronomy and Astrophysics | postscript=.
| volume=392 | issue=3 | pages=869–884 | date=September 2002
| doi=10.1051/0004-6361:20020984 | bibcode=2002A&A...392..869L | doi-access=free }}</ref>

<ref name=kharchenko2005>{{Citation
| last1=Kharchenko | first1=N. V. | last2=Piskunov | first2=A. E.
| last3=Röser | first3=S. | last4=Schilbach | first4=E.
| last5=Scholz | first5=R.-D. | display-authors=1
| title=Astrophysical parameters of Galactic open clusters
| journal=Astronomy and Astrophysics
| volume=438 | issue=3 | pages=1163–1173 | year=2005
| bibcode=2005A&A...438.1163K | arxiv=astro-ph/0501674
| doi=10.1051/0004-6361:20042523 | s2cid=9079873 | postscript=. }}</ref>

<ref name=Poggio2021>{{Citation
| last1=Poggio | first1=E. | last2=Drimmel | first2=R.
| last3=Cantat-Gaudin | first3=T. | last4=Ramos | first4=P.
| last5=Ripepi | first5=V. | display-authors=1
| title=Galactic spiral structure revealed by Gaia EDR3
| journal=Astronomy and Astrophysics
| volume=651 | pages=A104 | year=2021
| bibcode=2021A&A...651A.104P | arxiv=2103.01970
| doi=10.1051/0004-6361/202140687 | postscript=. }}</ref>

}}
{{notelist}}

==External links==
{{Commons}}
* [http://www.messier.seds.org/m/m029.html Messier 29, SEDS Messier pages]
* [http://veryoldphotons.com/object.html?M29 Messier 29] RGB Image
* [https://www.perseus.gr/Astro-DSO-NGC-6913.htm Messier 29] LRGB image – 2 hrs total exposure
* {{cite web|last=Lawrence|first=Pete|title=M29 – Open Cluster|url=http://www.deepskyvideos.com/videos/messier/M29.html|work=Deep Sky Videos|publisher=[[Brady Haran]]}}
* {{WikiSky|NGC 6913}}

{{Portal bar|Astronomy|Stars|Outer space}}
{{Messier objects}}
{{Ngc70}}
{{Cygnus (constellation)}}
{{Sky|20|23|56||38|31.4|00|4000}}

[[Category:Open clusters|Messier 029]]
[[Category:Cygnus (constellation)|Messier 029]]
[[Category:Messier objects|029]]
[[Category:NGC objects|Messier 029]]
[[Category:Orion–Cygnus Arm]]
[[Category:Astronomical objects discovered in 1764|17640729]]
[[Category:Discoveries by Charles Messier]]

Messier 29 - Revision history

imported>Robby: /* External links */ link to Commons is now defined on Wikidata