NGC 1978 (also known as ESO 85-SC90) is an elliptical shaped

globular cluster A globular cluster is a spheroidal conglomeration of stars that is bound together by gravity, with a higher concentration of stars towards its center. It can contain anywhere from tens of thousands to many millions of member stars, all orbiting ...

in the constellation

Dorado Dorado (, ) is a constellation in the Southern Sky. It was named in the late 16th century and is now one of the 88 modern constellations. Its name refers to the mahi-mahi (''Coryphaena hippurus''), which is known as ''dorado'' ("golden") in Sp ...

. It is located within the

Large Magellanic Cloud The Large Magellanic Cloud (LMC) is a dwarf galaxy and satellite galaxy of the Milky Way. At a distance of around , the LMC is the second- or third-closest galaxy to the Milky Way, after the Sagittarius Dwarf Spheroidal Galaxy, Sagittarius Dwarf ...

. It was discovered by

James Dunlop James Dunlop FRSE (31 October 1793 – 22 September 1848) was a Scottish astronomer, noted for his work in Australia. He was employed by Sir Thomas Brisbane to work as astronomer's assistant at his private observatory, once located at Param ...

on November 6, 1826. At an aperture of 50 arcseconds, its apparent V-band magnitude is 10.20, but at this wavelength, it has 0.16 magnitudes of

interstellar extinction In astronomy, extinction is the absorption and scattering of electromagnetic radiation by dust and gas between an emitting astronomical object and the observer. Interstellar extinction was first documented as such in 1930 by Robert Julius Trump ...

. It appears 3.9

arcminutes A minute of arc, arcminute (abbreviated as arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of a degree. Since one degree is of a turn, or complete rotation, one arcminute is of a tu ...

wide. NGC 1978 has a

radial velocity The radial velocity or line-of-sight velocity of a target with respect to an observer is the rate of change of the vector displacement between the two points. It is formulated as the vector projection of the target-observer relative velocity ...

of 293.1 ± 0.9 km/s. The northwest half of NGC 1978 is iron-rich and younger whereas the southeast part of the cluster has very little iron. NGC 1978 is also highly elliptical (ε ~ 0.30 ± 0.02), suggesting tidal action between it and the Large Magellanic Cloud. It is rich in pulsating

asymptotic giant branch The asymptotic giant branch (AGB) is a region of the Hertzsprung–Russell diagram populated by evolved cool luminous stars. This is a period of stellar evolution undertaken by all low- to intermediate-mass stars (about 0.5 to 8 solar masses) lat ...

stars, often oxygen-rich or carbon-rich. NGC 1978 is about 2 billion years old. Its estimated mass is , and its total luminosity is , leading to a mass-to-luminosity ratio of 0.40 /. All else equal, older star clusters have higher mass-to-luminosity ratios; that is, they have lower luminosities for the same mass.

References

External links

* {{DEFAULTSORT:NGC 1978 Globular clusters ESO objects

1978 Events January * January 1 – Air India Flight 855, a Boeing 747 passenger jet, crashes off the coast of Bombay, killing 213. * January 5 – Bülent Ecevit, of Republican People's Party, CHP, forms the new government of Turkey (42nd ...

Dorado Large Magellanic Cloud 18260906