Messier 30

Messier 30
Open cluster Messier 30 in Capricornus
Observation data (J2000 epoch)
ClassV[1]
ConstellationCapricornus
Right ascension21h 40m 22.12s[2]
Declination–23° 10′ 47.5″[2]
Distance27.14 ± 0.65 kly (8.3 ± 0.20 kpc)[3][4]
Apparent magnitude (V)7.2[5]
Apparent dimensions (V)12'.0
Physical characteristics
Mass1.6×105[6] M☉
Metallicity = –2.27[7] dex
Estimated age12.93 Gyr[8]
Other designationsM30, NGC 7099, GCl 122[9]
See also: Globular cluster, List of globular clusters

Messier 30 (also known as M30, NGC 7099, or the Jellyfish Cluster) is a globular cluster of stars in the southeast of the southern constellation of Capricornus, at about the declination of the Sun when the latter is at December solstice.[a] It was discovered by the French astronomer Charles Messier in 1764, who described it as a circular nebula without a star. In the New General Catalogue, compiled during the 1880s, it was described as a "remarkable globular, bright, large, slightly oval." It can be easily viewed with a pair of 10×50 binoculars,[10] forming a patch of hazy light some 4 arcminutes wide that is slightly elongated along the east–west axis.[10] With a larger instrument, individual stars can be resolved and the cluster will cover an angle of up to 12 arcminutes across graduating into a compressed core about one arcminute wide that has further star density within.[11]

It is longest observable (opposed to the Sun) in the first half of August.[b][10]

M30 is centered 27,100 light-years away from Earth with a roughly 2.5% margin of error,[4] and is about 93 light-years across.[11] The estimated age is roughly 12.9 billion years[8] and it forms a mass of about 160,000 times the mass of the Sun (M☉).[6] The cluster is following a retrograde orbit (against the general flow) through the inner galactic halo, suggesting that it was acquired from a satellite galaxy rather than forming within the Milky Way.[8] It is in this epoch 22.2 kly (6.8 kpc), from the center of the galaxy, compared to an estimated 26 kly (8.0 kpc) for the Sun.[12]

The cluster has passed through a dynamic process called core collapse and now has a concentration of mass at its core of about a million times the Sun's mass per cubic parsec. This makes it one of the highest density regions in the Milky Way galaxy. Stars in such close proximity will experience a high rate of interactions that can create binary star systems, as well as a type of star called a blue straggler that is formed by mass transfer.[3] A process of mass segregation may have caused the central region to gain a greater proportion of higher mass stars, creating a color gradient with increasing blueness toward the middle of the cluster.[13]

Masp showing the location of M30
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  2. ^ a b Cite error: The named reference aj140_6_1830 was invoked but never defined (see the help page).
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  4. ^ a b Cite error: The named reference aa555_36 was invoked but never defined (see the help page).
  5. ^ "Messier 30". SEDS Messier Catalog. Retrieved 22 July 2024.
  6. ^ a b Cite error: The named reference mnras392_1_113 was invoked but never defined (see the help page).
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  8. ^ a b c Cite error: The named reference mnras404_3_1203 was invoked but never defined (see the help page).
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  10. ^ a b c Cite error: The named reference jbaa118_4_231 was invoked but never defined (see the help page).
  11. ^ a b Cite error: The named reference omeara1998 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference aj117_1_277 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference aj119_3_1259 was invoked but never defined (see the help page).


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