{"id":56122,"date":"2024-03-13T14:28:42","date_gmt":"2024-03-13T14:28:42","guid":{"rendered":"http:\/\/178dda8b-1abc-4ebb-b7bb-a128f50159c4"},"modified":"2024-03-13T14:32:30","modified_gmt":"2024-03-13T14:32:30","slug":"why-do-some-galaxies-have-more-supernovae-than-others","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/rss_feed\/why-do-some-galaxies-have-more-supernovae-than-others\/","title":{"rendered":"Why do some galaxies have more supernovae than others?"},"content":{"rendered":"

While the Milky Way hasn\u2019t had a supernova in 400 years, other galaxies are bursting with them. Why is this, and why are supernovae important? <\/p>

By Chris Lintott\n <\/p>

Published: Wednesday, 13 March 2024 at 14:28 PM<\/p>

\n\n

Astronomers all over the world dream of a bright supernova. We haven\u2019t caught such an event in our own Galaxy since before the telescope was invented, and a typical system like the Milky Way might expect no more than one a century.<\/p>

Some galaxies<\/a> seem blessed. M61, for example, a rare spiral galaxy in the Virgo Cluster, has had eight since 1900.<\/p>

Image from Kitt Peak National Observatory of galaxy NGC 6496, showing the locations of Supernova 2004et and Supernova 2017eaw. Credits: KPNO, NSF’s NOIRLab, AURA, Alyssa Pagan (STScI)<\/figcaption><\/figure>
Why some galaxies should have more supernovae<\/a> is something of a puzzle. Most supernovae represent the death of massive stars, and so galaxies with more supernovae are likely to have more massive stars.<\/p>
As such behemoths burn through their fuel quickly, living for only a few hundred million years or so, their presence indicates recent star formation.<\/p>
Supernovae are therefore signs that a galaxy is alive and happily making stars.<\/p>
**Read more from Chris Lintott:<\/strong><\/em><\/p>**
**How do black holes form?<\/strong><\/em><\/a><\/li>**
**How do binary stars survive in star clusters?<\/strong><\/em><\/a><\/li>**
Solving the three-body problem in astronomy<\/strong><\/em><\/a><\/li><\/ul>
Galaxies that have more supernovae do have higher rates of star formation but otherwise appear completely normal, with little to distinguish them from their neighbours.<\/p>
An interesting study takes a close look at NGC 2770, a spiral galaxy that appears to buck this trend.<\/p>
3 definite supernovae have been found in the galaxy in the last 20 years \u2013 in 1999, 2007 and 2008 \u2013 and a fourth candidate, in 2015, is either a supernova or an outburst from a type of giant star called a luminous blue variable.<\/p>
$\"Three$
Three images of NGC 2770 from early 2008 show the rare occurrence of two supernovae. Credit: ESO<\/figcaption><\/figure>
Despite these fireworks, NGC 2270 seems to have a normal, rather than an enhanced, star formation rate. What\u2019s going on?<\/p>
Previous attempts to work out how many stars NGC 2770 is forming depended on observations made with a radio telescope in Westerbork, the Netherlands.<\/p>
Hydrogen is the fuel for star formation and so finding a galaxy rich in the gas usually means a more productive stellar nursery. Based on these observations, NGC 2770 seemed to have a star formation rate of about one solar mass per year \u2013 more or less the same as our own Milky Way.<\/p>
To explain the observed burst of supernovae, a rate of 20 times that would be necessary.<\/p>
So, how do we explain this difference? In the study I mentioned above, a team led by Michal Michalowski of the Adam Mickiewicz University<\/a> in Poland lay the blame on dust, so often a confounding factor in observations.<\/p>
Dust \u2013 particles of silicon and carbon \u2013 absorbs light, making the galaxy appear fainter in the wavelengths that reveal star formation than would otherwise be the case.<\/p>
Dust is associated with star formation, so it\u2019s not unexpected for the two to go together, but the size of the correction is surprising.<\/p>
Once dust is properly measured and accounted for, the star formation rate for the galaxy is nearly 50 solar masses per year: more than enough to explain the supernovae.<\/p>
$\"The$
The dusty lanes of our own galaxy the Milky Way, with the Rho Ophiuchi and Antares region visible on the right. Credit: ESO\/S. Guisard (www.eso.org\/~sguisard)<\/figcaption><\/figure>
But why does NGC 2770 have such a high star formation rate? One possibility is that it may have just survived an interaction with a neighbouring galaxy.<\/p>
There\u2019s a faint bridge of matter linking the main galaxy to one of its companions, a typical sign of an ongoing merger.<\/p>
Such interactions often stir up gas, triggering star formation. It\u2019s possible that our own Milky Way might undergo a similar burst of star formation in a few billion years when it interacts with Andromeda.<\/p>
Impatient astronomers may not want to wait that long, though, and will be keeping their fingers crossed in the meantime.<\/p>
Chris was reading <\/strong><\/em>NGC 2770: high supernova rate due to interaction<\/strong>**by Micha\u0142 J. Micha\u0142owski et al. Read it online at** **https:\/\/arxiv.org\/abs\/2008.08091<\/a>.<\/strong><\/em><\/p>**
**This article originally appeared in the October 2020 issue of BBC Sky at Night Magazine.<\/strong><\/em><\/p> <\/body><\/html>\n**
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