Messier 30

{{short description|Globular cluster in the constellation Capricornus}}

{{Use dmy dates|date=February 2021}}

{{Infobox globular cluster

| name = Messier 30

| image = File:M30 NASA.jpg

| caption = Open cluster Messier 30 in Capricornus

| epoch = J2000

| class = V

| ra = {{RA|21|40|22.12}}

| dec = {{DEC|–23|10|47.5}}

| dist_ly = {{cvt|27.14|+/-|0.65|kly|kpc|lk=on|sigfig=2}}

| appmag_v = 7.2{{cite web |url=http://www.messier.seds.org/m/m030.html |title=Messier 30 |access-date=22 July 2024 |website=SEDS Messier Catalog}}

| size_v = 12'.0

| constellation = Capricornus

| mass_msol = {{Val|1.6|e=5}}

| radius_ly =

| v_hb =

| age = 12.93 Gyr

| metal_fe = –2.27

| notes =

| names = M30, NGC 7099, GCl 122

}}

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.{{efn|Thus, its northern limit for good visibility is a few degrees south of the Arctic Circle, all year}} 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, forming a patch of hazy light some 4 arcminutes wide that is slightly elongated along the east–west axis. 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.

It is longest observable (opposed to the Sun) in the first half of August.{{efn|This is when it is risen, throughout the night, so culminates about midnight. The Earth's orbit means the sun leaves Capricornus, as if it heads east a few degrees NNE, on about 15 or 16 February, having figured in the constellation for a month.}}

M30 is centered 27,100 light-years away from Earth with a roughly 2.5% margin of error, and is about 93 light-years across. The estimated age is roughly 12.9 billion years and it forms a mass of about 160,000 times the mass of the Sun ({{solar mass}}). 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. It is in this epoch {{cvt|22.2|kly|kpc}}, from the center of the galaxy, compared to an estimated {{cvt|26|kly|kpc}} for the Sun.

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. 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.

File:M30map.png

See also

References and footnotes

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}}

Notes

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