{"id":21935,"date":"2020-06-01T11:00:51","date_gmt":"2020-06-01T15:00:51","guid":{"rendered":"https:\/\/hobbyspace.com\/Blog\/?p=21935"},"modified":"2020-05-31T20:21:30","modified_gmt":"2020-06-01T00:21:30","slug":"eso-small-hot-stars-observed-with-giant-magnetic-spots-and-super-flares","status":"publish","type":"post","link":"https:\/\/hobbyspace.com\/Blog\/?p=21935","title":{"rendered":"ESO: Small hot stars display giant magnetic spots and super-flares"},"content":{"rendered":"

The latest report from ESO (European Southern Observatory)<\/a>:<\/p>\n

Hot stars are plagued by giant magnetic spots, ESO data shows<\/a><\/strong><\/p>\n

<\/a>
Astronomers using ESO telescopes have discovered giant spots on the surface of extremely hot stars hidden in stellar clusters, called extreme horizontal branch stars. This image shows an artist\u2019s impression of what one of these stars, and its giant whitish spot, might look like. The spot is bright, takes up a quarter of the star\u2019s surface and is caused by magnetic fields. As the star rotates, the spot on its surface comes and goes, causing visible changes in brightness.<\/figcaption><\/figure>\n

Astronomers using European Southern Observatory (ESO) telescopes have discovered giant spots on the surface of extremely hot stars hidden in stellar clusters. Not only are these stars plagued by magnetic spots, some also experience superflare events, explosions of energy several million times more energetic than similar eruptions on the Sun. The findings, published today in Nature Astronomy, help astronomers better understand these puzzling stars and open doors to resolving other elusive mysteries of stellar astronomy.<\/p>\n

The team, led by Yazan Momany from the INAF Astronomical Observatory of Padua in Italy, looked at a particular type of star known as extreme horizontal branch stars \u2014 objects with about half the mass of the Sun but four to five times hotter.<\/p>\n

\u201cThese hot and small stars are special because we know they will bypass one of the final phases in the life of a typical star and will die prematurely,\u201d<\/em> says Momany, who was previously a staff astronomer at ESO\u2019s Paranal Observatory in Chile. \u201cIn our Galaxy, these peculiar hot objects are generally associated with the presence of a close companion star.\u201d<\/em><\/p>\n

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Spots on extreme horizontal branch stars (right) appear to be quite different from the dark sunspots on our own Sun (left), but both are caused by magnetic fields. The spots on these hot, extreme stars are brighter and hotter than the surrounding stellar surface, unlike on the Sun where we see spots as dark stains on the solar surface that are cooler than their surroundings. The spots on extreme horizontal branch stars are also significantly larger than sunspots, covering up to a quarter of the star\u2019s surface. While sunspots vary in size, a typical size is around an Earth-size planet, 3000 smaller than a giant spot on an extreme horizontal branch star.<\/figcaption><\/figure>\n

Surprisingly, however, the vast majority of these extreme horizontal branch stars, when observed in tightly packed stellar groups called globular clusters, do not appear to have companions. The team\u2019s long-term monitoring of these stars, made with ESO telescopes, also revealed that there was something more to these mysterious objects. When looking at three different globular clusters, Momany and his colleagues found that many of the extreme horizontal branch stars within them showed regular changes in their brightness over the course of just a few days to several weeks.<\/p>\n

\u201cAfter eliminating all other scenarios, there was only one remaining possibility to explain their observed brightness variations,\u201d <\/em>concludes Simone Zaggia, a study co-author from the INAF Astronomical Observatory of Padua in Italy and a former ESO Fellow: \u201cthese stars must be plagued by spots!\u201d<\/em><\/p>\n

Spots on extreme horizontal branch stars appear to be quite different from the dark sunspots on our own Sun, but both are caused by magnetic fields. The spots on these hot, extreme stars are brighter and hotter than the surrounding stellar surface, unlike on the Sun where we see spots as dark stains on the solar surface that are cooler than their surroundings. The spots on extreme horizontal branch stars are also significantly larger than sunspots, covering up to a quarter of the star\u2019s surface. These spots are incredibly persistent, lasting for decades, while individual sunspots are temporary, lasting only a few days to months. As the hot stars rotate, the spots on the surface come and go, causing the visible changes in brightness.<\/p>\n