Dwingeloo 2 is a small
irregular galaxy
An irregular galaxy is a galaxy that does not have a distinct regular shape, unlike a spiral or an elliptical galaxy. Irregular galaxies do not fall into any of the regular classes of the Hubble sequence, and they are often chaotic in appearance, ...
discovered in 1996 and located about 10 million
light-years away from the Earth. Its discovery was a result of the Dwingeloo Obscured Galaxy Survey (DOGS) of the
Zone of Avoidance
The Zone of Avoidance (ZOA, ZoA), or Zone of Galactic Obscuration (ZGO), is the area of the sky that is obscured by the Milky Way.
The Zone of Avoidance was originally called the Zone of Few Nebulae in an 1878 paper by English astronomer Richard ...
using the
Dwingeloo Radio Observatory. Dwingeloo 2 is a companion galaxy of
Dwingeloo 1
Dwingeloo 1 is a barred spiral galaxy about 10 million light-years away from the Earth, in the constellation Cassiopeia. It lies in the Zone of Avoidance and is heavily obscured by the Milky Way. The size and mass of Dwingeloo 1 are comparabl ...
.
[
Dwingeloo 2 was first detected at ]radio
Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmi ...
wavelength
In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats.
It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, t ...
s from the 21 cm emission line
A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to identi ...
of neutral atom
Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons.
Every solid, liquid, gas, ...
ic hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...
(known to astronomer
An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, moons, comets and galaxies – in either ...
s as HI) in the course of follow-up observations after the discovery of Dwingeloo 1.[ Dwingeloo 2 is thought to be a member of the ]IC 342/Maffei Group
The IC 342/Maffei Group (also known as the IC 342 Group or the Maffei 1 Group) corresponds to one or two galaxy groups close to the Local Group. The member galaxies are mostly concentrated around either IC 342 or Maffei 1, which would be the brig ...
, a galaxy group
A galaxy group or group of galaxies (GrG) is an aggregation of galaxies comprising about 50 or fewer gravitationally bound members, each at least as luminous as the Milky Way (about 1010 times the luminosity of the Sun); collections of galaxie ...
adjacent to the Local Group
The Local Group is the galaxy group that includes the Milky Way.
It has a total diameter of roughly , and a total mass of the order of .
It consists of two collections of galaxies in a "dumbbell" shape: the Milky Way and its satellites form ...
.[
The visible radius of Dwingeloo 2 is approximately 2′, which at the distance of 3 Mpc corresponds to about 2 kpc.][
The irregular structure of Dwingeloo 2 is likely related to its interaction with the much larger nearby galaxy Dwingeloo 1, which lies at a distance of only 24 kpc from Dwingeloo 2.][
]
References
External links
*
{{Sky, 02, 54, 08.47, +, 59, 00, 19.1
Irregular galaxies
IC 342/Maffei Group
Astronomical objects discovered in 1996
101304
Cassiopeia (constellation)