A study on the expansion of Tycho supernova remnant

Image of the Tycho Supernova remnant (Image X-ray: NASA/CXC/GSFC/B. Williams et al; Optical: DSS; Radio: NSF/NRAO/VLA)
Image of the Tycho Supernova remnant (Image X-ray: NASA/CXC/GSFC/B. Williams et al; Optical: DSS; Radio: NSF/NRAO/VLA)

An article published in “The Astrophysical Journal Letters” describes a research on the Tycho supernova remnant. That explosion was seen on Earth in 1572 in an event well documented. The expansion of the remaining materials is still interesting and a team of astronomers studied it with NASA’s Chandra X-ray Observatory, the NSF’s Karl G. Jansky Very Large Array (VLA) and many other telescopes to create a kind of film that shows it.

This supernova, also known as SN 1572 or 3C 10, was described in detail by the astronomer Tycho Brahe, hence the name. It was a historic event in the field of astronomy and not only for that century. Supernovae are exceptional events and that was visible even during the day.

At about 10,000 years from Earth, a white dwarf exploded in a supernova, perhaps pulling gas from another star or merging with another white dwarf. The remnant of the explosion is studied even today to better understand that kind of incredibly energetic phenomenon, in particular the mechanisms that trigger it.

A large part of the materials blasted from the exploded star were heated by shock waves and therefore the remnant of the Tycho supernova shine at X-rays. This remnant was observed many times using the Chandra space observatory so it was possible to create a small film that shows its evolution from 2000 to 2015. These observations were combined with those of about 30 years made in radio waves with the VLA.

These observations allowed to measure the speed of the shock wave created by the supernova in a very precise way, also thanks to the large remnant size. It’s roughly circular but there are differences in the shock wave speed in different regions. The speed differences are caused by density differences in the gas surrounding the supernova remnant. We’re talking about very high spped and the highest observed is around 20 million km/h (about 12 million mph).

These analyzes can help to look for a possible companion star of the one exploded to see if the supernova happened stealing gas from it. If there was no companion it means that there was a merger of two white dwarfs to reach the critical mass needed to trigger a supernova.

The films with X-ray and radio wave views of the Tycho supernova remnant are available on a page of the Chandra space observatory website.

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