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| Observation data | |
| Type | Sb |
| Right ascension (RA, α) ( J2000.0) | 00 h 42.8 m |
| Declination (Dec, δ) (J2000.0) | +41° 16' |
| Distance from Earth | 2.9 millions LY 0.92 Mpc |
| Apparent magnitude (V) | +3.4m |
| Other denominations |
M31 NGC 224 |
The Andromeda Galaxy (also known as Messier Object 31, M31, or NGC 224) is a giant spiral galaxy in the Local Group, together with the Milky Way galaxy. It is at a distance of approximately 2.9 million light years or 920 kpc, in the direction of the constellation Andromeda.
With a mass of about 1.5 times more than the Milky Way, it is the dominant galaxy of the Local Group, which consists of about 30 small galaxies plus three large spirals: Andromeda, Milky Way and M33. (With improving measurements and data, some scientists now believe that the Milky Way contains more ' dark matterDark matter is matter that can't be detected by its emitted radiation but whose presence can be inferred from gravitational effects on visible matter such as stars and galaxies. Estimates of the amount of matter in the universe based on gravitational effe' and may be more massive than M31.)
Projections indicate that the Andromeda Galaxy is on a collision course with the Milky Way, approaching at a speed of about 140 kilometres per second. Impact is predicted in about 3 billion years; the two galaxies will probably merge to form a giant elliptical.
This galaxy plays an important role in galactic studies, since it is the nearest giant spiral. In 1943, Walter BaadeWilhelm Heinrich Walter Baade ( March 24 1893 June 25 1960) was a German astronomer who emigrated to the USA in 1931. Along with Fritz Zwicky, he proposed that supernovas could create neutron stars. He took advantage of wartime blackout conditions during was the first person to resolve stars in the central region of the Andromeda Galaxy. Edwin HubbleEdwin Powell Hubble ( November 20, 1889 September 28, 1953) was a noted American astronomer, generally credited for discovering 1 and proving redshift and that the universe is expanding. Hubble was born to an insurance executive in Marshfield, Missouri an identified extragalactic cepheid variable starsA Cepheid variable is a member of a particular class of variable stars, notable for a fairly tight correlation between their period of variability and absolute stellar luminosity. Because of this correlation (discovered by Henrietta Swan Leavitt in 1912), for the first time on astronomical photos of this galaxy, enabling its distance to be determined.
Robin Barnard of the Open UniversityThe Open University (OU is a distance learning university which has students all over the UK. The administration is based at Walton Hall, Milton Keynes in Buckinghamshire although it has offices in each region of the UK. It also has over 25,000 students s has detected 10 X-ray sources in the Andromeda Galaxy, published April 5th 2004, using observations from the European Space Agency XMM-Newton orbiting observatory. He hypothesizes that these are candidate black holes or neutron stars, which are heating incoming gas to millions of kelvins and emitting X-rays. The spectrum of the neutron stars is the same as the hypothesized black holes, but can be distinguished by their masses.