Free Astronomy Magazine July-August 2020

20 JULY-AUGUST 2020 SPACE CHRONICLES half the mass of the Sun but four to five times hotter. “These 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 prema- turely,” says Momany, who was previously a staff astronomer at ESO’s Paranal Observatory in Chile. “In our Galaxy, these pecu- liar hot objects are generally asso- ciated with the presence of a close companion star.” Surprisingly, however, the vast ma- jority of these extreme horizontal branch stars, when observed in tightly packed stellar groups called globular clusters, do not appear to have companions. The team’s long-term monitoring of these stars, made with ESO telescopes, also revealed that there was some- Hot stars are plagued by giant magnetic spots by ESO A stronomers using European Southern Observatory (ESO) telescopes have discovered giant spots on the surface of ex- tremely hot stars hidden in stellar clusters. Not only are these stars plagued by magnetic spots, some also experience superflare events, explosions of energy several mil- lion times more energetic than similar eruptions on the Sun. The findings, published in Nature As- tronomy , help astronomers better understand these puzzling stars and open doors to resolving other elusive mysteries of stellar astron- omy. The team, led by Yazan Mo- many from the INAF Astronomical Observatory of Padua in Italy, looked at a particular type of star known as extreme horizontal branch stars — objects with about T he background image and the video above show an artist’s 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’s surface and is caused by magnetic fields. As the star rotates, the spot on its sur- face comes and goes, causing visible changes in brightness. Note that the movement does not represent the rotation of the star: it mimics the movement of a camera observing the star up close. [ESO/L. Calçada, INAF-Padua/S. Zaggia]