NGC 6745
Encyclopedia
NGC 6745 is an irregular galaxy
about 206 million light-year
s (63.5 mega-parsec
s) away in the constellation
Lyra
. It is actually a triplet of galaxies in the process of colliding.
The three galaxies have been colliding for hundreds of millions of years. After passing through the larger galaxy (NGC 6745A), the smaller one (NCG 6745B) is now moving away. The larger galaxy was probably a spiral galaxy
before the collision, but was damaged and now appears peculiar
. It is unlikely that any stars in the two galaxies collided directly because of the vast distances between them. The gas
, dust
, and ambient magnetic field
s of the galaxies, however, do interact directly in a collision. As a result of this interaction, the smaller galaxy has probably lost most of its interstellar medium
to the larger one.
The age of NGC 6745 is estimated to be ~10 Myr.
Irregular galaxy
An irregular galaxy is a galaxy that does not have a distinct regular shape, like a spiral or an elliptical galaxy. The shape of an irregular galaxy is uncommon – they do not fall into any of the regular classes of the Hubble sequence, and they are often chaotic in appearance, with neither a...
about 206 million light-year
Light-year
A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...
s (63.5 mega-parsec
Parsec
The parsec is a unit of length used in astronomy. It is about 3.26 light-years, or just under 31 trillion kilometres ....
s) away in the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
Lyra
Lyra
Lyra is a small constellation. It is one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and remains one of the 88 modern constellations recognized by the International Astronomical Union. Its principal star, Vega — a corner of the Summer Triangle — is one of the brightest...
. It is actually a triplet of galaxies in the process of colliding.
The three galaxies have been colliding for hundreds of millions of years. After passing through the larger galaxy (NGC 6745A), the smaller one (NCG 6745B) is now moving away. The larger galaxy was probably a spiral galaxy
Spiral galaxy
A spiral galaxy is a certain kind of galaxy originally described by Edwin Hubble in his 1936 work The Realm of the Nebulae and, as such, forms part of the Hubble sequence. Spiral galaxies consist of a flat, rotating disk containing stars, gas and dust, and a central concentration of stars known as...
before the collision, but was damaged and now appears peculiar
Peculiar galaxy
A peculiar galaxy is a galaxy which is unusual in its size, shape, or composition. Peculiar galaxies come about as a result of interactions between galaxies, and they may contain atypical amounts of dust or gas, may have higher or lower surface brightness than a typical galaxy, or may have...
. It is unlikely that any stars in the two galaxies collided directly because of the vast distances between them. The gas
Gas
Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...
, dust
Dust
Dust consists of particles in the atmosphere that arise from various sources such as soil dust lifted up by wind , volcanic eruptions, and pollution...
, and ambient magnetic field
Magnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...
s of the galaxies, however, do interact directly in a collision. As a result of this interaction, the smaller galaxy has probably lost most of its interstellar medium
Interstellar medium
In astronomy, the interstellar medium is the matter that exists in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, dust, and cosmic rays. It fills interstellar space and blends smoothly into the surrounding intergalactic space...
to the larger one.
The age of NGC 6745 is estimated to be ~10 Myr.