(ORDO NEWS) — Before they die in a supernova explosion, massive stars are enveloped in a cloud of matter that drastically reduces their apparent brightness.
This process develops over just a few months, allowing us to predict the onset of a cosmic catastrophe.
Some stars end their lives by exploding in supernovae. A sudden and bright flash is accompanied by the ejection of the outer shells, leaving behind – depending on the initial size – a black hole or a neutron star.
Such a finale is typical for massive stars, red supergiants like the famous Betelgeuse, gaining eight or more solar masses.
As soon as they run out of internal resources to continue thermonuclear fusion, the core rapidly collapses and “bounces” back, exploding the star.
From the outside, this process develops unexpectedly, and it is not yet possible to predict the moment of a supernova explosion in advance.
From the same Betelgeuse, this is expected at almost any moment, which, by astronomical standards, can mean both tomorrow and in a couple of million years.
Ben Davies and his co-authors focused on type II-P supernovae. Before the outburst, such stars abruptly shed the material that surrounds them in a cloud.
During the explosion, it becomes very hot and then gradually cools down, due to which type II-P supernovae are characterized by rather slow decay.
Scientists have modeled several alternative mechanisms for the accumulation of circumstellar matter. The simulation results were compared with archival images of distant giants that subsequently exploded in II-P supernovae.
The work showed that the formation of the cloud occurs rapidly. The process takes less than a year – sometimes several months – and leads to a drop in the apparent brightness of the star by tens or even hundreds of times.
This allows us to hope that now we will be able to predict the outbreaks of some supernovae in advance. If a red supergiant is rapidly enveloped in a cloud of matter and dies out, an explosion can be expected at any moment – tomorrow or in a few months.
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