Dwingeloo 2
Encyclopedia
Dwingeloo 2 is a small irregular galaxy
discovered in 1996 and located about 10 million light-years away from the Earth. Its discovery was a result of Dwingeloo Obscured Galaxy Survey (DOGS) of the Zone of Avoidance
. Dwingeloo 2 is a companion galaxy of Dwingeloo 1
.
Dwingeloo 2 was first detected at radio
wavelength
s from the 21 cm emission line of neutral atom
ic hydrogen
(known to astronomers
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 Maffei 1 group, a group of galaxies adjacent to the Local Group
.
The visible radius of Dwingeloo 2 is approximately 2′, which at the distance of 3 Mpc corresponds to about 2 kpc. The neutral hydrogen is detected as far as 3.2 kpc from the center. The mass of the galaxy within this radius is estimated at 2.3 billion Solar masses. The total mass of the galaxy is about five times less than that of Dwingeloo 1.
Dwingeloo 2 has a a well defined rotating disk inclined at approximately 69° with respect to observer. The galaxy recedes from the Milky Way at the speed of about 241 km/s. The distribution of the neutral hydrogen in Dwingeloo 2 is quite irregular. Its total mass is estimated at about 100 million Solar mass
es. The irregular structure of Dwingeloo 2 is likely related to its interaction with nearby much larger galaxy Dwingeloo 1, which lies at the distance of only 24 kpc from Dwingeloo 2.
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...
discovered in 1996 and located about 10 million light-years away from the Earth. Its discovery was a result of Dwingeloo Obscured Galaxy Survey (DOGS) of the Zone of Avoidance
Zone of Avoidance
The Zone of Avoidance is the area of the night sky that is obscured by our own galaxy, the Milky Way.-Term:The ZOA was originally called the "Zone of Few Nebulae" in an 1878 paper by English astronomer Richard Proctor that referred to the distribution of "nebulae" in Sir John Herschel's General...
. Dwingeloo 2 is a companion galaxy of Dwingeloo 1
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...
.
Dwingeloo 2 was first detected at radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
s from the 21 cm emission line of neutral atom
Atom
The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...
ic hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
(known to astronomers
Astronomy
Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...
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 Maffei 1 group, a group of galaxies adjacent to the Local Group
Local Group
The Local Group is the group of galaxies that includes Earth's galaxy, the Milky Way. The group comprises more than 30 galaxies , with its gravitational center located somewhere between the Milky Way and the Andromeda Galaxy...
.
The visible radius of Dwingeloo 2 is approximately 2′, which at the distance of 3 Mpc corresponds to about 2 kpc. The neutral hydrogen is detected as far as 3.2 kpc from the center. The mass of the galaxy within this radius is estimated at 2.3 billion Solar masses. The total mass of the galaxy is about five times less than that of Dwingeloo 1.
Dwingeloo 2 has a a well defined rotating disk inclined at approximately 69° with respect to observer. The galaxy recedes from the Milky Way at the speed of about 241 km/s. The distribution of the neutral hydrogen in Dwingeloo 2 is quite irregular. Its total mass is estimated at about 100 million Solar mass
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
es. The irregular structure of Dwingeloo 2 is likely related to its interaction with nearby much larger galaxy Dwingeloo 1, which lies at the distance of only 24 kpc from Dwingeloo 2.