Andromeda Galaxy

General information

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. Due to the fact that it is moving towards us, the Andromeda Galaxy is one of the few galaxies to exhibit a blue shift.

Related Topics:
Elliptical - Blue shift

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This galaxy plays an important role in galactic studies, since it is the nearest giant spiral. In 1943, Walter Baade was the first person to resolve stars in the central region of the Andromeda Galaxy. Edwin Hubble identified extragalactic cepheid variable stars for the first time on astronomical photos of this galaxy, enabling its distance to be determined.

Related Topics:
Walter Baade - Edwin Hubble - Cepheid variable stars

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Robin Barnard of the Open University 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.

Related Topics:
Robin Barnard - Open University - April 5 - 2004 - European Space Agency - XMM-Newton - Neutron stars

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In 1991 the Planetary Camera then onboard the Hubble Space Telescope imaged Andromeda's core. To everyone's surprise its nucleus showed a double structure, with two nuclear hot-spots located within a few light years of each other. Subsequent ground-based observations have led to speculation that indeed two nuclei exist, are moving with respect to each other, that one nucleus is slowly tidally disrupting the other, and that one nucleus may be the remnant of a smaller galaxy "eaten" by M31. The nuclei of many galaxies, including M31, are known to be quite violent places, and the existence of supermassive black holes are frequently postulated to explain them.

Related Topics:
Hubble Space Telescope - Supermassive black hole

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Scott Chapman, from the California Institute of Technology, and Rodrigo Ibata, from the Observatoire Astronomique de Strasbourg in France, announced in 2005 their observations with the Keck telescopes which show that the tenuous sprinkle of stars extending outward from the galaxy are actually part of the main disk itself. This means that the spiral disk of stars in Andromeda is three times larger in diameter than previously estimated. This constitutes evidence that there is a vast, extended stellar disk that makes the galaxy more than 220,000 light-years in diameter. Previously, estimates of Andromeda's size ranged from 70,000 to 120,000 light-years across.

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