Wednesday, 22 November, 2017

Tycho’s Supernova

2Cas_TychoAlso known as SN 1572, Tycho’s Supernova is a Type Ia supernova 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. It is often called Tycho’s supernova, because of the Danish astronomer’s Tycho Brahe’s extensive work “Concerning the Star, new and never before seen in the life or memory of anyone”, published in 1573. Tycho was not even close to being the first to observe the supernova, although he was probably the most accurate observer of the object. The more reliable contemporary reports state that the star itself burst forth sometime between November 2 and 6 in 1572, when it rivaled Venus in brightness. The supernova remained visible to the naked eye into 1574, gradually fading until it disappeared from view.

3SNEchoThe distance to the supernova remnant has been estimated to approximate 8,000 and 9,800 light-years. A Type Ia supernova is one in which a white dwarf star has accreted matter from a companion until it approaches the Chandrasekhar limit and explodes. A shell of gas is still expanding from its center at about 9,000 km/s. A recent study indicates a rate of expansion of below 5,000 km/s.

4tsnr2radChandra’s image of the supernova remnant shows an expanding bubble of multimillion degree debris (green and red) inside a more rapidly moving shell of extremely high energy electrons (filamentary blue). As a huge ball of exploding plasma, it was Irving Langmuir who coined the name plasma because of its similarity to blood plasma. The filamentary blue outer shell of X-ray emitting high-speed electrons is also a characteristic of plasmas. All x-rays images must use processed colours, since x-rays (as are radio waves, infra-red) are invisible to the human eye.

4tycho_chandraGamma-rays detected by Fermi’s LAT show that the remnant of Tycho’s supernova shines in the highest-energy form of light. This portrait of the shattered star includes gamma rays (magenta), X-rays (yellow, green, and blue), infrared (red) and optical data. “Fortunately, high-energy gamma rays are produced when cosmic rays strike interstellar gas and starlight. These gamma rays come to Fermi straight from their sources,” said Francesco Giordano at the University of Bari and the National Institute of Nuclear Physics in Italy.

6SN_1572_6-7keVWhen a star explodes, it is transformed into a supernova remnant, a rapidly expanding shell of hot gas bounded by the blast’s shockwave. Scientists expect that magnetic fields on either side of the shock front can trap particles between them in what amounts to a subatomic ping pong game. As they shuttle back and forth across the supernova shock, the charged particles gain energy with each traverse. Eventually they break out of their magnetic confinement, escaping the supernova remnant and freely roaming the galaxy.

Credits: NASA, Sky & Telescope, Wikipedia.

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