View source for Messier 37

{{short description|Open cluster in the constellation Auriga}}
{{Infobox open cluster
| name = Messier 37
| image = [[File:M37 Mazur full.jpg|300px]]
| caption = Open cluster Messier 37 in Auriga
| epoch = J2000.0
| class = I
| constellation = [[Auriga (constellation)|Auriga]]
| ra = {{RA|5|52|18}}<ref name=mnras399_4_2146/>
| dec = {{DEC|+32|33|02}}<ref name=mnras399_4_2146/>
| dist_ly = {{Convert|4.511|kly|kpc|abbr=on|lk=on}}<ref name=mnras399_4_2146/>
| appmag_v = 6.2
| size_v = 24′
| mass_kg =
| mass_msol = 1,500<ref name=aaa477_1_165/>
| radius_ly = 10-13 ly
| v_hb =
| age = {{nowrap|346.7<ref name=mnras399_4_2146/> to 550<ref name=apj691_1_342/> [[Julian year (astronomy)|Ma]]}}
| notes =
| names = [[NGC 2099]]
}}

'''Messier 37''' (also known as '''M37''', '''[[New General Catalogue|NGC]] 2099''', or the '''Salt and Pepper Cluster''') is the brightest and richest [[open cluster]] in the [[constellation]] [[Auriga (constellation)|Auriga]]. It was discovered by the Italian astronomer [[Giovanni Battista Hodierna]] before 1654. M37 was missed by French astronomer [[Guillaume Le Gentil]] when he rediscovered [[Messier 36|M36]] and [[Messier 38|M38]] in 1749. French astronomer [[Charles Messier]] independently rediscovered M37 in September 1764 but all three of these clusters were recorded by Hodierna. It is classified as [[Robert Julius Trumpler|Trumpler]] type I,1,r or I,2,r. {{Citation needed|date=December 2024}}

M37 exists in [[Galactic anticenter|the antipodal direction]], opposite from the [[Galactic Center]] as seen from [[Earth]], so is in one of the nearby outer arms.<ref name=aaa511_A56/> Specifically it is still close enough to be in [[Orion Arm|our own]]. Estimates of its age range from 347<ref name=mnras399_4_2146/>&nbsp;million to 550<ref name=apj691_1_342/>&nbsp;million years. It has 1,500<ref name=aaa477_1_165/> times the mass of the [[Sun]] ({{solar mass}}) and contains over 500 identified stars,<ref name=apj691_1_342/> with roughly 150 stars brighter than [[apparent magnitude|magnitude]] 12.5. M37 has at least a dozen [[red giants]] and its hottest [[stellar evolution|surviving]] [[main sequence]] star is of [[stellar classification]] B9&nbsp;V. The abundance of elements other than hydrogen and helium, what astronomers term [[metallicity]], is similar to, if not slightly higher than, the abundance in the Sun.<ref name=mnras399_4_2146/> As of 2022, it contains only the third known [[planetary nebula]] associated with an open cluster.<ref>{{cite journal|doi=10.3847/2041-8213/ac88c1|title=The Planetary Nebula in the 500 Myr Old Open Cluster M37 |year=2022 |last1=Fragkou |first1=Vasiliki |last2=Parker |first2=Quentin A. |last3=Zijlstra |first3=Albert A. |last4=Vázquez |first4=Roberto |last5=Sabin |first5=Laurence |last6=Rechy-Garcia |first6=Jackeline Suzett |journal=The Astrophysical Journal Letters |volume=935 |issue=2 |pages=L35 |arxiv=2208.06101 |bibcode=2022ApJ...935L..35F |s2cid=251554540 |doi-access=free }}</ref>

At its estimated distance of around {{Convert|4,500|ly|pc|abbr=off|lk=on}}<ref name=mnras399_4_2146/> from Earth, the cluster's [[angular diameter]] of 24&nbsp;[[arcminute]]s corresponds to a physical extent of about {{Convert|20|-|25|ly|pc|abbr=on|lk=off}}. The [[tidal radius (cluster)|tidal radius]] of the cluster, where external [[gravitational perturbation]]s begin to have a significant influence on the orbits of its member stars, is about {{Convert|46|-|59|ly|pc|abbr=on|lk=off}}. This cluster is following an orbit through the [[Milky Way]] with a period of 219.3 Ma and an [[orbital eccentricity|eccentricity]] of 0.22. This will bring it as close as {{Convert|19.6|kly|kpc|abbr=on|lk=off}} to, and as distant as {{Convert|30.7|kly|kpc|abbr=on|lk=off}} from, the [[Galactic Center]]. It reaches a peak distance above the [[galactic plane]] of {{Convert|0.29|kly|kpc|abbr=on|lk=off}} and will cross the plane with a period of 31.7 Ma.<ref name=mnras399_4_2146/>

==Sky charts==
{{Gallery
 | title=
 | width=250
 | height=250
 | align=center
 | File:M37 charta.png|M37 appears as the central yellow dot in this large-scale (close range), detailed map
 | File:M37map.png|Small-scale (outline) map.  Cocchierre (Italian) translates to Auriga.
}}

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

==References==
{{reflist|refs=
<ref name=mnras399_4_2146>{{citation | display-authors=1 | last1=Wu | first1=Zhen-Yu | last2=Zhou | first2=Xu | last3=Ma | first3=Jun | last4=Du | first4=Cui-Hua | title=The orbits of open clusters in the Galaxy | journal=[[Monthly Notices of the Royal Astronomical Society]] | volume=399 | issue=4 | pages=2146–2164 |date=November 2009 | doi=10.1111/j.1365-2966.2009.15416.x | doi-access=free | bibcode=2009MNRAS.399.2146W |arxiv = 0909.3737 | s2cid=6066790 }}</ref>

<ref name=aaa511_A56>{{citation | display-authors=1 | last1=Pancino | first1=E. | last2=Carrera | first2=R. | last3=Rossetti | first3=E. | last4=Gallart | first4=C. | title=Chemical abundance analysis of the open clusters Cr 110, NGC 2099 (M 37), NGC 2420, NGC 7789, and M 67 (NGC 2682) | journal=[[Astronomy and Astrophysics]] | volume=511 | page=A56 |date=February 2010 | doi=10.1051/0004-6361/200912965 | bibcode=2010A&A...511A..56P |arxiv = 0910.0723 | s2cid=15143348 }}</ref>

<ref name=apj691_1_342>{{citation | display-authors=1 | last1=Hartman | first1=J. D. | last2=Gaudi | first2=B. S. | last3=Pinsonneault | first3=M. H. | last4=Stanek | first4=K. Z. | last5=Holman | first5=M. J. | last6=McLeod | first6=B. A. | last7=Meibom | first7=S. | last8=Barranco | first8=J. A. | last9=Kalirai | first9=J. S. | title=Deep MMT Transit Survey of the Open Cluster M37. III. Stellar Rotation at 550 Myr | journal=[[The Astrophysical Journal]] | volume=691 | issue=1 | pages=342–364 |date=January 2009 | doi=10.1088/0004-637X/691/1/342 | bibcode=2009ApJ...691..342H |arxiv = 0803.1488 | s2cid=10102360 }}</ref>

<ref name=aaa477_1_165>{{citation | display-authors=1 | last1=Piskunov | first1=A. E. | last2=Schilbach | first2=E. | last3=Kharchenko | first3=N. V. | last4=Röser | first4=S. | last5=Scholz | first5=R.-D. | title=Tidal radii and masses of open clusters | journal=Astronomy and Astrophysics | volume=477 | issue=1 | pages=165–172 |date=January 2008 | doi=10.1051/0004-6361:20078525 | bibcode=2008A&A...477..165P | doi-access=free }}</ref>

}}

==External links==
{{commons category}}
* [http://www.messier.seds.org/m/m037.html Messier 37, SEDS Messier pages]
* {{cite web|title=M37 – Open Cluster|url=http://www.deepskyvideos.com/videos/messier/M37_open_cluster.html|work=Deep Sky Videos|publisher=[[Brady Haran]]|author=Szymanek, Nik|author-link=Nik Szymanek|author2=Norton, Andy |author3=Merrifield, Michael }}

{{Portal bar|Astronomy|Stars|Outer space}}
{{Catalogs|M=37|NGC=2099}}
{{Messier objects}}
{{Ngc25}}
{{Auriga (constellation)}}
{{Sky|05|52|19||32|33|02|4400}}

{{DEFAULTSORT:Messier 37}}
[[Category:Open clusters|Messier 037]]
[[Category:Auriga|Messier 037]]
[[Category:Messier objects|037]]
[[Category:NGC objects|Messier 037]]
[[Category:Perseus Arm]]
[[Category:Astronomical objects discovered in 1654|?]]