Portal:Astronomy/Featured
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[edit] This month's featured article
The Crab Nebula (catalogue designations M1, NGC 1952) is a supernova remnant in the constellation of Taurus. The nebula was first observed in 1731 by John Bevis. It is the remnant of a supernova that was recorded by Chinese and Arab astronomers in 1054. Located at a distance of about 6,300 light years (1.93 kpc) from Earth, the nebula has a diameter of 11 ly (1.84 pc) and is expanding at a rate of about 1,500 kilometres per second.
The Crab Nebula contains a pulsar in its centre which rotates twenty eight times per second, emitting pulses of radiation from gamma rays to radio waves. The nebula was the first astronomical object identified with a historical supernova explosion.
The nebula acts as a source of radiation for studying celestial bodies that occult it. In the 1950s and 1960s, the Sun's corona was mapped from observations of the Crab's radio waves passing through it, and more recently, the thickness of the atmosphere of Saturn's moon Titan was measured as it blocked out X-rays from the nebula.
Recently featured: Mercury – Fermi Paradox – Definition of planet
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[edit] Upcoming featured articles
[edit] November 2006
The Crab Nebula (catalogue designations M1, NGC 1952) is a supernova remnant in the constellation of Taurus. The nebula was first observed in 1731 by John Bevis. It is the remnant of a supernova that was recorded by Chinese and Arab astronomers in 1054. Located at a distance of about 6,300 light years (1.93 kpc) from Earth, the nebula has a diameter of 11 ly (1.84 pc) and is expanding at a rate of about 1,500 kilometres per second.
The Crab Nebula contains a pulsar in its centre which rotates twenty eight times per second, emitting pulses of radiation from gamma rays to radio waves. The nebula was the first astronomical object identified with a historical supernova explosion.
The nebula acts as a source of radiation for studying celestial bodies that occult it. In the 1950s and 1960s, the Sun's corona was mapped from observations of the Crab's radio waves passing through it, and more recently, the thickness of the atmosphere of Saturn's moon Titan was measured as it blocked out X-rays from the nebula.
Recently featured: Mercury – Fermi Paradox – Definition of planet
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[edit] December 2006
The Hubble Deep Field (HDF) is an image of a small region in the constellation Ursa Major, based on the results of a series of observations by the Hubble Space Telescope. It covers an area 144 arcseconds across, equivalent in angular size to a tennis ball at a distance of 100 metres. The image was assembled from 342 separate exposures taken with the Space Telescope's Wide Field and Planetary Camera 2 over ten consecutive days between December 18 and December 28, 1995.
The field is so small that only a few foreground stars in the Milky Way lie within it; thus, almost all of the 3,000 objects in the image are galaxies, some of which are among the youngest and most distant known. By revealing such large numbers of very young galaxies, the HDF has become a landmark image in the study of the early universe, and it has been the source of almost 400 scientific papers since it was created.
Three years after the HDF observations were taken, a region in the south celestial hemisphere was imaged in a similar way and named the Hubble Deep Field South. The similarities between the two regions strengthened the belief that the universe is uniform over large scales and that the Earth occupies a typical region in the universe (the cosmological principle). In 2004 a deeper image, known as the Hubble Ultra Deep Field, was constructed from a total of eleven days of observations. This image is the deepest (most sensitive) astronomical image ever made at visible wavelengths.
Recently featured: Crab Nebula – Mercury – Fermi Paradox
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[edit] January 2007
Barnard's Star is a very low-mass star in the constellation Ophiuchus which was discovered by the astronomer E. E. Barnard in 1916. Barnard measured its proper motion to 10.3 arcseconds per year, which remains the largest known proper motion of any star relative to the Sun. Lying at a distance of about 1.8 parsecs or 5.96 light-years, Barnard's Star is the second closest known star system to the Sun and the fourth closest known individual star after the three components of the Alpha Centauri system.
Barnard's Star is a relatively well-studied astronomical object, and has likely received more attention than any other M dwarf star given its proximity and favourable location for observation near the celestial equator. It has also been the subject of some controversy. For a decade from the early 1960s onward, an erroneous discovery of a planet or planets in orbit around Barnard's star was accepted by astronomers. It is also notable as the target for a study on the possibility of rapid, unmanned travel to nearby star systems. Research has focused on stellar characteristics, astrometry, and refining the limits of possible planets.
Recently featured: Hubble Deep Field – Crab Nebula – Mercury
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