Kepler's Supernova: Astronomers witnessed star's explosive demise even before telescopes existed

More than 400 years ago, skywatchers, including famous German astronomer Johannes Kepler, saw a supernova explosion that destroyed a star about 20,000 light years away from Earth in our Milky Way galaxy - that's before telescopes existed.

Residing about 13,000 light-years away in the constellation Ophiuchus, Kepler's supernova remnant is the result of a Type Ia supernova, which occurs when a white dwarf star surpasses a certain mass limit after interacting with a companion star. This causes a thermonuclear explosion that destroys the white dwarf and propels its remains outward.

According to NASA, The Kepler supernova is the last supernova seen inside the disk of our Milky Way galaxy, with the exception of the Cassiopeia A supernova, which was reported to have been seen around 1680. This means that it is likely that we will soon witness another stellar explosion. The closest supernova to have been seen recently was 1987A, which was spotted in 1987 in the Large Magellanic Cloud.

Before telescopes existed, Johannes Kepler saw a supernova explosion destroy a star. 🌟 Born #OTD 451 years ago, his name and legacy have lived on in Kepler’s supernova and our Kepler space telescope 🔭✨: https://t.co/hLh95otBDj #HappyBirthday pic.twitter.com/fZDv9epAAk

— NASA Ames (@NASAAmes) December 27, 2022

In 2004, astronomers probed the expanding remains of Kepler's supernova using three of NASA's powerful observatories - the Hubble Space Telescope, the Spitzer Space Telescope, and the Chandra X-ray Observatory.

By analyzing Chandra X-ray spectra, which provide the intensity of X-rays at different wavelengths, scientists in 2020 tracked the speed of 15 small knots of debris in the Kepler supernova remnant. The fastest knot was determined to be moving at a rate of 23 million miles per hour, the highest speed ever recorded for supernova remnant debris in X-rays. Out of the 15 knots, eight are confirmed to be moving away from Earth, while only two are known to be heading towards it.