SN 1572
From Wikipedia, the free encyclopedia
| Supernova SN 1572 | |
 X-ray image of the SN 1572 remnant |
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| Observation data (Epoch ?) | |
|---|---|
| Supernova type | Type Ia |
| Remnant type | Nebula |
| Host Galaxy | Milky Way |
| Constellation | Cassiopeia |
| Right ascension | 0h 25.3m |
| Declination | +64° 09′ |
| Galactic coordinates | G.120.1+1.4 |
| Discovery Date | November 1572 |
| Peak magnitude (V) | -4 |
| Distance | 7500 light-years |
| Physical characteristics | |
| Progenitor | Unknown |
| Progenitor type | Unknown |
| Colour (B-V) | Unknown |
SN 1572 or "B Cassiopeiae" (B Cas) was a supernova of Type Ia in the constellation Cassiopeia, one of about eight supernovae visible to the naked eye in historical records. It burst forth in early November 1572 and was independently discovered by many individuals.
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[edit] Historic Description
The appearance of the Milky Way supernova of 1572 was perhaps one of the two or three most important events in the history of astronomy. The "new star" helped to shatter stale, ancient models of the heavens and to inaugurate a tremendous revolution in astronomy that began with the realized need to produce better astrometric star catalogues (and thus the need for more precise astronomical observing instruments). The supernova of 1572 is often called "Tycho's supernova", because of the extensive work that Tycho Brahe (1573, 1602, 1610) did in both observing the new star and in analyzing his own observations and those of many other observers. But Tycho was not even close to being the first to observe the 1572 supernova, although he was apparently the most accurate observer of the object (though not by much over some of his European colleagues like Wolfgang Schuler and Francesco Maurolico).
The more reliable contemporary reports state that the new star itself burst forth sometime between 1572 November 2 and 6, when it rivalled Venus in brightness. The supernova remained visible to the naked eye into 1574, gradually fading until it disappeared from view.
[edit] The Supernova Remnant of SN 1572
[edit] Radiological Detection
The search for a supernova remnant was negative until a half-century ago, when Hanbury Brown and Hazard (1952) reported a radio detection at 158.5 MHz. This was confirmed at wavelength 1.9 m by Baldwin and Edge (1957), and the remnant was also identified tentatively in the second Cambridge radio-source catalogue as object "2C 34" and identified more firmly as "3C 10" in the third Cambridge list (Edge et al. 1959). There is no dispute that 3C 10 is the remnant of the supernova observed in 1572-1573. Following a review article by Minkowski (1968), the designation 3C 10 appears to be that most commonly used in the literature when referring to the radio remnant of B Cas (though some authors use the tabulated Galactic designation G120.7+2.1 of Green 1984, and many authors commonly refer to it as "Tycho's supernova remnant" --- somewhat of a misnomer, as Tycho saw the pointlike supernova, not the expansive radio remnant). Because the radio remnant was reported before the optical supernova-remnant wisps were discovered, the designation 3C 10 is used by some to signify the remnant at all wavelengths.
SN 1572 is associated with the radio source G.120·1+1·4. It has an apparent diameter of 7.4 arc minutes, and is located approximately 7,500 light years from our Solar system.
[edit] Optical Detection
The supernova remnant of B Cas was discovered in the 1960s by scientists with a Palomar Mountain telescope as a very faint nebula. It was later photographed by a telescope on the international ROSAT spacecraft. The supernova was probably of Type Ia, in which a white dwarf star has accreted matter from a companion until it reaches the Chandrasekhar limit and explodes. This type of supernova does not typically create the spectacular nebula more typical of Type II supernovas, such as SN 1054 which created the Crab Nebula. A shell of gas is still expanding from its center at about 9,000 km/s.
[edit] Discovery of the Companion Star
In October 2004, a letter in Nature reported the discovery of a G2 star, similar in type to our own Sun. It is thought to be the companion star that contributed mass to the white dwarf that ultimately resulted in the supernova. A subsequent study, published in March 2005, revealed further details about this star: labeled Tycho G, it was likely a main sequence star or subgiant prior to the explosion, but had some of its mass stripped away and its outer layers shock-heated from the effects of the supernova. Tycho G's current velocity is perhaps the strongest evidence that it was the companion star to the white dwarf, as it is traveling at a rate of 136 km/s, which is more than forty times faster than the mean velocity of other stars in its stellar neighbourhood.
