Messier 30 (also known as M30 or NGC 7099) is a globular cluster of stars in the southern constellation of Capricornus. 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." This cluster 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 with a compressed core one arcminute wide. It is best observed around August.
M30 is located at a distance of about 27,100 light-years from Earth, and is about 93 light-years across. The estimated age is roughly 12.93 billion years and it has a combined mass of about 160,000 times the mass of the Sun. The cluster is following a retrograde orbit through the inner galactic halo, suggesting that it was acquired from a satellite galaxy rather than forming within the Milky Way. It is currently located at a distance of about 22.2 kly (6.8 kpc) from the center of the galaxy, compared to an estimated 26 kly (8.0 kpc) for the Sun.
The M30 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.
|Observation data (J2000 epoch)|
|Right ascension||21h 40m 22.12s|
|Declination||–23° 10′ 47.5″|
|Distance||27.14 ± 0.65 kly (8.3 ± 0.20 kpc)|
|Apparent magnitude (V)||+7.7|
|Apparent dimensions (V)||12'.0|
|Metallicity||= –2.27 dex|
|Estimated age||12.93 Gyr|
|Other designations||M30, NGC 7099, GCl 122|
Alpha2 Capricorni (α2 Capricorni), or Algedi , is a triple star system in the southern constellation of Capricornus. It is visible to the naked eye with an apparent visual magnitude of +3.57, forming part of the double star Alpha Capricorni along with α¹ Capricorni. Based upon an annual parallax shift of 30.82 mas as seen from the Earth, the star is located 106 light years from the Sun.August
August is the eighth month of the year in the Julian and Gregorian calendars, and the fifth of seven months to have a length of 31 days. It was originally named Sextilis in Latin because it was the sixth month in the original ten-month Roman calendar under Romulus in 753 BC, and March was the first month of the year. About 700 BC, it became the eighth month when January and February were added to the year before March by King Numa Pompilius, who also gave it 29 days. Julius Caesar added two days when he created the Julian calendar in 46 BC (708 AUC), giving it its modern length of 31 days. In 8 BC, it was renamed in honor of Augustus. According to a Senatus consultum quoted by Macrobius, he chose this month because it was the time of several of his great triumphs, including the conquest of Egypt.In the Southern Hemisphere, August is the seasonal equivalent of February in the Northern Hemisphere. In many European countries, August is the holiday month for most workers. Numerous religious holidays occurred during August in ancient Rome.Certain meteor showers take place in August. The Kappa Cygnids take place in August, with the dates varying each year. The Alpha Capricornids meteor shower takes place as early as July 10 and ends at around August 10, and the Southern Delta Aquariids take place from mid-July to mid-August, with the peak usually around July 28–29. The Perseids, a major meteor shower, typically takes place between July 17 and August 24, with the days of the peak varying yearly. The star cluster of Messier 30 is best observed around August.
Among the aborigines of the Canary Islands, especially among the Guanches of Tenerife, the month of August received in the name of Beñesmer or Beñesmen, which was also the harvest festival held this month.Capricornus
Capricornus is one of the constellations of the zodiac. Its name is Latin for "horned goat" or "goat horn" or "having horns like a goat's", and it is commonly represented in the form of a sea-goat: a mythical creature that is half goat, half fish. Its symbol is (Unicode ♑).
Capricornus is one of the 88 modern constellations, and was also one of the 48 constellations listed by the 2nd century astronomer Ptolemy. Under its modern boundaries it is bordered by Aquila, Sagittarius, Microscopium, Piscis Austrinus, and Aquarius. The constellation is located in an area of sky called the Sea or the Water, consisting of many water-related constellations such as Aquarius, Pisces and Eridanus. It is the smallest constellation in the zodiac.Chi Capricorni
Chi Capricorni, Latinized from χ Capricorni, is a star in the southern constellation of Capricornus. Based upon an annual parallax shift of 18.14 mas as seen from the Earth, the star is located about 180 light years from the Sun. It is visible to the naked eye with an apparent visual magnitude of +5.28.Eta Capricorni
Eta Capricorni, Latinized from η Capricorni, is a binary star system in the southern constellation of Capricornus. It can be seen with the naked eye, having a combined apparent visual magnitude of +4.84. Based upon an annual parallax shift of 20.20 mas as seen from the Earth, the star is located about 161 light years from the Sun.
The pair orbit each other with a period of 27.85 years, a semimajor axis of 0.265 arc seconds, an eccentricity of 0.410. The primary member, component A, is a white-hued A-type main sequence star with an apparent magnitude of +5.02. Its companion, component B, has an apparent magnitude of +7.39.Kappa Capricorni
Kappa Capricorni (κ Cap, κ Capricorni) is a solitary star in the constellation Capricornus. It is visible to the naked eye with an apparent visual magnitude of +4.73. Based upon an annual parallax shift of 11.09 mas as seen from the Earth, the star is located about 294 light years from the Sun.
This is a yellow-hued, evolved, G-type giant star with a stellar classification of G8 III. There is a 91% probability that it is currently on the horizontal branch, rather than the red giant branch. As such, it is a red clump giant with an estimated 2.43 times the mass of the Sun and has expanded to 13.28 times the radius of the Sun. The star is about 1.2 billion years old and has a projected rotational velocity that is too small to be measured. It radiates 107 times the solar luminosity from its photosphere at an effective temperature of 5,096 K.Lambda Capricorni
Lambda Capricorni, Latinized from λ Capricorni, is a solitary star in the southern constellation of Capricornus. It is faintly visible to the naked eye with an apparent visual magnitude of +5.56. Based upon an annual parallax shift of 11.58 mas as seen from the Earth, the star is located about 282 light years from the Sun. At that distance, the visual magnitude is diminished by an extinction factor of 0.11 due to interstellar dust.This is a white-hued A-type main sequence star with a stellar classification of A1 V. It is a magnetic Ap star, indicating the spectrum displays chemically peculiar features. The star has an estimated 2.50 times the mass of the Sun and about 2.2 times the Sun's radius. It is 155 million years old and is spinning rapidly with a projected rotational velocity of 192.5 km/s. Lambda Capricorni is radiating 45 times the Sun's luminosity from its photosphere at an effective temperature of 10,674 K.Messier object
The Messier objects are a set of 110 astronomical objects cataloged by the French astronomer Charles Messier in his Catalogue des Nébuleuses et des Amas d'Étoiles ("Catalogue of Nebulae and Star Clusters").
Because Messier was interested in finding only comets, he created a list of non-comet objects that frustrated his hunt for them. The compilation of this list, in collaboration with his assistant Pierre Méchain, is known as the Messier catalogue. This catalogue of objects is one of the most famous lists of astronomical objects, and many Messier objects are still referenced by their Messier number.
The catalogue includes some astronomical objects that can be observed from Earth's Northern Hemisphere such as deep-sky objects, a characteristic which makes the Messier objects extremely popular targets for amateur astronomers.A preliminary version first appeared in the Memoirs of the French Academy of Sciences in 1771,
and the last item was added in 1966 by Kenneth Glyn Jones, based on Messier's observations.
The first version of Messier's catalogue contained 45 objects and was published in 1774 in the journal of the French Academy of Sciences in Paris. In addition to his own discoveries, this version included objects previously observed by other astronomers, with only 17 of the 45 objects being Messier's.
By 1780 the catalogue had increased to 80 objects. The final version of the catalogue containing 103 objects was published in 1781 in the Connaissance des Temps for the year 1784.
However, due to what was thought for a long time to be the incorrect addition of Messier 102, the total number remained 102. Other astronomers, using side notes in Messier's texts, eventually filled out the list up to 110 objects.The catalogue consists of a diverse range of astronomical objects, ranging from star clusters and nebulae to galaxies. For example, Messier 1 is a supernova remnant, known as the Crab Nebula, and the great spiral Andromeda Galaxy is M31. Many further inclusions followed in the next century when the first addition came from Nicolas Camille Flammarion in 1921, who added Messier 104 after finding Messier's side note in his 1781 edition exemplar of the catalogue. M105 to M107 were added by Helen Sawyer Hogg in 1947, M108 and M109 by Owen Gingerich in 1960, and M110 by Kenneth Glyn Jones in 1967.Nu Capricorni
Nu Capricorni (ν Capricorni, abbreviated Nu Cap, ν Cap) is a binary star in the southern constellation of Capricornus. It is 6.6 degrees north of the ecliptic and so is subject to occultations by the Moon. The system is about 253 light-years from the Sun.
The two components are designated Nu Capricorni A (formally named Alshat , the traditional name for the systm) and B.Phi Capricorni
Phi Capricorni (φ Cap, φ Capricorni) is a solitary star in the southern constellation of Capricornus. It is visible to the naked eye with an apparent visual magnitude of +5.16. Based upon an annual parallax shift of 5.07 mas as seen from the Earth, the star is located about 640 light years from the Sun, give or take 30 light years.
This is an evolved, orange-hued K-type giant/bright giant star with a stellar classification of K0 II-III It shows an infrared excess, which may be due to leftover material from a mass-loss event. The star has an estimated 2.63 times the mass of the Sun, and radiates 447 times the solar luminosity from its photosphere at an effective temperature of 4,490 K. Phi Capricorni is around 1.24 billion years old and is spinning with a projected rotational velocity of 3.8 km/s.Pi Capricorni
Pi Capricorni, Latinized from π Capricorni, is a triple star in the southern constellation of Capricornus. It has the traditional star name Okul or Oculus (meaning eye in Latin). The system is approximately 550 light years from Earth.
In Chinese, 牛宿 (Niú Su), meaning Ox (asterism), refers to an asterism consisting of π Capricorni, β Capricorni, α2 Capricorni, ξ2 Capricorni, ο Capricorni and ρ Capricorni. Consequently, the Chinese name for π Capricorni itself is 牛宿四 (Niú Su sì, English: the Fourth Star of Ox.)The primary member, component A, is a spectroscopic binary whose two components are separated by 0.1 arcseconds. The brighter of the two, component Aa, is a blue-white B-type bright giant or main sequence star with an apparent magnitude of +5.08. The third member, component B, is an eighth magnitude star 3.4 arcseconds from the primary.Shapley–Sawyer Concentration Class
The Shapley–Sawyer Concentration Class is a classification system on a scale of one to twelve using Roman numerals for globular clusters according to their concentration. The most highly concentrated clusters such as M75 are classified as Class I, with successively diminishing concentrations ranging to Class XII, such as Palomar 12. (The class is sometimes given with numbers [Class 1–12] rather than with Roman numerals.)Sigma Capricorni
Sigma Capricorni, Latinized from σ Capricorni, is a solitary star in the southern constellation of Capricornus. It is an evolved, orange-hued K-type giant star with an apparent magnitude of +5.31. Sigma Capricorni is located approximately 1,100 light years from Earth.Stellar collision
A stellar collision is the coming together of two stars caused by stellar dynamics within a star cluster, or by the orbital decay of a binary star due to stellar mass loss or gravitational radiation, or by other mechanisms not yet well understood.
Astronomers predict that events of this type occur in the globular clusters of our galaxy about once every 10,000 years. On 2 September 2008 scientists first observed a stellar merger in Scorpius (named V1309 Scorpii), though it was not known to be the result of a stellar merger at the time. A series of stellar collisions in a dense cluster over a short period of time can lead to an intermediate-mass black hole via "runaway stellar collisions".Any stars in the universe can collide, whether they are 'alive', meaning fusion is still active in the star, or 'dead', with fusion no longer taking place. White dwarf stars, neutron stars, black holes, main sequence stars, giant stars, and supergiants are very different in type, mass, temperature, and radius, and so react differently.A gravitational wave event that occurred on 25 August 2017, GW170817, was reported on 16 October 2017 to be associated with the merger of two neutron stars in a distant galaxy, the first such merger to be observed via gravitational radiation.Tau2 Capricorni
Tau2 Capricorni (τ2 Capricorni) is a triple star system in the constellation Capricornus. It is approximately 1,100 light years from Earth. The system has a combined apparent magnitude of +5.20. Because it is near the ecliptic, τ2 Capricorni can be occulted by the Moon, and also (rarely) by planets.
The primary component, τ2 Capricorni A, is a blue-white B-type giant with an apparent magnitude of +5.8. At a distance of only 0.34 arcseconds is the second component, τ2 Capricorni B, a blue-white B-type subgiant with an apparent magnitude of +6.3. These two stars orbit around their common centre of mass once every 420 years. A possible third component with an apparent magnitude of +9.5, detected by studying the star during occultation, is located 0.052 arcseconds away from the A component.Upsilon Capricorni
Upsilon Capricorni, Latinized from υ Capricorni, is a solitary star 0.22 degrees north of the ecliptic, in the southern constellation Capricornus. It is a M-type red giant with an apparent magnitude of +5.17, about 760 light years from Earth.Xi1 Capricorni
Xi1 Capricorni, Latinized from ξ1 Capricorni, is an orange-hued star in the constellation Capricornus. With an apparent visual magnitude of +6.34, it is near the lower limit of brightness for stars that can be seen with the naked eye. Based upon an annual parallax shift of 6.95 mas as seen from Earth, this system is located roughly 470 light years from the Sun. It is an evolved K-type giant star with a stellar classification of K0 III. With an age of 3.35 billion years, this star has an estimated 1.55 times the mass of the Sun and is radiating 89 times the Sun's luminosity from its enlarged photosphere at an effective temperature of about 4,439 K.Xi2 Capricorni
Xi2 Capricorni (ξ2 Capricorni) is a yellow-white hued star in the southern constellation of Capricornus. It is dimly visible to the naked eye on a dark night, having an apparent visual magnitude of +5.83. Based upon an annual parallax shift of 36.10 mas as seen from Earth, this system is located 90 light years from the Sun.
This is an F-type main-sequence star with a stellar classification of F7 V Fe−0.5, where the suffix notation indicates the spectrum displays a mild underabundance of iron. It is around three billion years old with 1.2 times the mass of the Sun. Although considered a single star, there is reason to suspect it forms a wide physical pair with the visual magnitude 10.94 red dwarf star LP 754–50. They have a projected separation of (28.3±0.3)×103 AU, with LP 754–50 having an estimated 0.55 times the mass of the Sun. If they are gravitationally bound, their orbital period would be around 3.7 million years.