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T Pyxidis

April 14, 2016

Every now and then, a star can blow its top. Five years ago tonight, for example, a faint star in a faint constellation was seen to explode. For a while, it glowed thousands of times brighter than normal.

T Pyxidis is about 16,000 light-years away. It consists of two stars that orbit each other. One star dumps material onto the other. When the pressure in the infalling material gets too high, it triggers a nuclear explosion.

We’ve seen several of these blasts. Light from the first one reached Earth in 1890. No one saw it then, but photographic plates captured it. Light from subsequent explosions reached Earth in 1902, 1920, 1944, and 1966. Then nearly half a century passed before the most recent eruption, which came in 2011.

Images from Hubble Space Telescope suggest that the star hasn’t always been so cantankerous. Instead, it started exploding only in the past 150 years. The Hubble images show debris hurled into space during each explosion. But there’s no material very far from the star, indicating that the first explosion probably occurred around the year 1866.

Although T Pyxidis has faded, you can still see its constellation tonight — if you have a good star chart and can get away from city lights. Pyxis is in low the southern sky as night falls, and wheels to the southwest later on. The obscure constellation represents a magnetic compass. But it’s best known for an explosive resident — T Pyxidis.


Script by Ken Croswell, Copyright 2015

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