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Tycho's Supernova Remnant

In 1572, Danish astronomer Tycho Brahe recorded the sudden appearance of a bright new star in the constellation Cassiopeia. The new star (a supernova) faded from view over a period of months. It is the last stellar explosion seen in our Milky Way galaxy. Now known as Tycho's Supernova Remnant, the expanding debris cloud is shown in this detailed false-color x-ray image from the orbiting Chandra Observatory. Represented in blue, the highest energy x-rays come from shocked regions along the outer edges of the supernova remnant, corresponding to gas at temperatures of 20 million degrees Celsius. X-rays from cooler gas (only 10 million degrees or so!) dominate the remnant's interior.

Tycho's supernova remnant presents several interesting contrasts with the Cassiopeia A (Cas A) supernova remnant. The debris for Tycho is distributed in clumps rather than knots as in Cas A, and its outer shock wave can be seen in smooth and continuous arcs rather than being fragmented, as in Cas A.

Also, no central point source is detected in Tycho, in contrast to Cas A. The absence of a central point source is consistent with other evidence that Tycho is a Type Ia supernova, which is thought to signal the detonation and destruction of a white dwarf star. Theory predicts that a white dwarf star will explode when infalling matter from a companion star increases the mass of the white dwarf beyond a critical mass limit, known as the Chandrasekhar limit.

At a distance of about 7,500 light-years, Tycho's Supernova Remnant is nearly 20 light-years across.