beecee Posted January 9, 2019 Posted January 9, 2019 (edited) https://phys.org/news/2019-01-evidence-gigantic-star-explosions.html First evidence of gigantic remains from star explosions January 9, 2019, Lancaster University Astrophysicists have found the first ever evidence of gigantic remains being formed from repeated explosions on the surface of a dead star in the Andromeda Galaxy, 2.5 million light years from Earth. The remains or "super-remnant" measures almost 400 light years across. For comparison, it takes just 8 minutes for light from the Sun to reach us. A white dwarf is the dead core of a star. When it is paired with a companion star in a binary system, it can potentially produce a nova explosion. If the conditions are right, the white dwarf can pull gas from its companion star and when enough material builds up on the surface of the white dwarf, it triggers a thermonuclear explosion or "nova", shining a million times brighter than our Sun and initially moving at up to 10,000 km per second. Astrophysicists including Dr. Steven Williams from Lancaster University in the UK examined the nova M31N 2008-12a in the Andromeda Galaxy, one of our nearest neighbours. Read more at: https://phys.org/news/2019-01-evidence-gigantic-star-explosions.html#jCpthe paper: https://www.nature.com/articles/s41586-018-0825-4 A recurrent nova super-remnant in the Andromeda galaxy: Abstract: The accretion of hydrogen onto a white dwarf star ignites a classical nova eruption1,2—a thermonuclear runaway in the accumulated envelope of gas, leading to luminosities up to a million times that of the Sun and a high-velocity mass ejection that produces a remnant shell (mainly consisting of insterstellar medium). Close to the upper mass limit of a white dwarf3 (1.4 solar masses), rapid accretion of hydrogen (about 10−7 solar masses per year) from a stellar companion leads to frequent eruptions on timescales of years4,5 to decades6. Such binary systems are known as recurrent novae. The ejecta of recurrent novae, initially moving at velocities of up to 10,000 kilometres per second7, must ‘sweep up’ the surrounding interstellar medium, creating cavities in space around the nova binary. No remnant larger than one parsec across from any single classical or recurrent nova eruption is known8,9,10, but thousands of successive recurrent nova eruptions should be capable of generating shells hundreds of parsecs across. Here we report that the most frequently recurring nova, M31N 2008-12a in the Andromeda galaxy (Messier 31 or NGC 224), which erupts annually11, is indeed surrounded by such a super-remnant with a projected size of at least 134 by 90 parsecs. Larger than almost all known remnants of even supernova explosions12, the existence of this shell demonstrates that the nova M31N 2008-12a has erupted with high frequency for millions of years. Edited January 9, 2019 by beecee
Recommended Posts