Monday, May 24, 2021

The new light from Andromeda

In 1885, a new light suddenly came on within the Andromeda Galaxy (M31).
Initially this new star was noticed by some amateur astronomers around Europe, but they did not report their observations. The first to report the discovery was the German astronomer Hartwig on August 20, 1885, who was observing from the Dorpat Observatory in Estonia.
Astronomers soon realized that the new light was nothing more than a supernova, the first and so far only observed inside the Andromeda Galaxy. SN 1885A (name by which it is now called) was also the first supernova observed outside the Milky Way, although at the time of its discovery in 1885 it was not yet clear whether M31 was an external galaxy similar to the Milky Way or only a nebula inside it.
Today's researchers, based on the observations of the time, were able to reconstruct the light curve of the supernova. On August 21th, SN 1885A had an apparent magnitude of +6 (at the limit of visibility with the naked eye), but already six months later its magnitude had reduced to the fourteenth.
Using the Hubble Space Telescope, astronomers were also able to discover what the rest of the supernova might be. The supernova is believed to have originated from the thermonuclear explosion of a white dwarf.
Credit: David Dayag.

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