Liller 1 is a

globular cluster A globular cluster is a spheroidal conglomeration of stars. Globular clusters are bound together by gravity, with a higher concentration of stars towards their centers. They can contain anywhere from tens of thousands to many millions of membe ...

in the constellation

Scorpius Scorpius is a zodiac constellation located in the Southern celestial hemisphere, where it sits near the center of the Milky Way, between Libra to the west and Sagittarius to the east. Scorpius is an ancient constellation that pre-dates the Gr ...

, discovered by the American astronomer

William Liller William Liller (April 1, 1927, Philadelphia – February 28, 2021) was an American astronomer, known for his research on "planetary nebulae, comets, asteroids, magnetic activity in cool stars, the optical identification of X-ray sources, and astr ...

in 1977. It is close to the centre of the

Milky Way The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye. ...

in its

galactic bulge In astronomy, a galactic bulge (or simply bulge) is a tightly packed group of stars within a larger star formation. The term almost exclusively refers to the central group of stars found in most spiral galaxies (see galactic spheroid). Bulges ...

, only 2,600 light-years (800 pc) from the centre. Liller 1 is just under 30,000 light years from Earth.

Properties

Liller 1 is located within the

, and is heavily obscured by

dust Dust is made of fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian process), volcanic eruptions, and pollution. Dust in ho ...

, being close to the

galactic plane The galactic plane is the plane on which the majority of a disk-shaped galaxy's mass lies. The directions perpendicular to the galactic plane point to the galactic poles. In actual usage, the terms ''galactic plane'' and ''galactic poles'' usual ...

. Thus, studies of this object have mostly been conducted in wavelengths other than the optical range. The absorbing clouds of dust are not uniform, and the extinction coefficient R_''V'' is 2.5, less than the typically assumed value of 3.1. Liller 1 has a mass of around 2.3 million solar masses; this makes it one of the more massive globular clusters, along with others such as ω Centauri and

Terzan 5 Terzan 5 is a heavily obscured globular cluster belonging to the bulge (the central star concentration) of the Milky Way galaxy. It was one of six globulars discovered by French astronomer Agop Terzan in 1968 and was initially labeled ''Terzan 11' ...

. After Terzan 5, it has the highest rate of stellar collisions of any Milky Way globular cluster. It also has the highest level of emission of

gamma ray A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically ...

s of any globular cluster. This may be due to a large number of stellar collisions and pulsars, but it may also be an unrelated background gamma ray source. Liller 1 and Terzan 5 are remarkably similar. Although globular clusters are typically

metal-poor In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal physical matter in the Universe is either hydrogen or helium, and astronomers use the word ''"metals"'' as ...

, both have a relatively high metallicity; the abundance of metals for Liller 1 is estimated to be half that of the Sun. In 2021, Liller 1 was found to have two different stellar populations. One is about 12 billion years, but the other is relatively young, at 1 to 3 billion years. This suggests that it may not be a true globular cluster, but a class of star cluster that coalesced to form galactic bulges. The globular cluster contains the rapid burster called MXB 1730-335.

References

{{Reflist Globular clusters Scorpius (constellation)