The mystery of the pulsating blue stars

[Judi Lynn]

August 9, 2017





In the middle of the large Chilean Atacama desert, a team of Polish astronomers are patiently monitoring millions of celestial bodies night after night with the help of a modern robotic telescope. In 2013, the team was surprised when they discovered, in the course of their survey, stars that pulsated much faster than expected. In the following years, the team that included Dr. Marilyn Latour, an astronomer from the Dr. Remeis-Sternwarte Bamberg, the astronomical institute of Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), studied these stars in more detail and concluded that they had stumbled upon a new class of variable star.

Many classes of star exhibit variations in brightness. Unlike our Sun, these stars are not stable; their surface oscillates, meaning that the surface expands and shrinks by a few percent. This is what happens in the case of the more familiar Cepheids and RR Lyrae stars, which have oscillation periods that extend over a few hours to hundreds of days.

The researchers discovered a dozen stars that seemed at first sight to show variations that were very similar to those of the Cepheids and RR Lyrae stars but have much shorter (20-40 minutes) oscillation periods and, at the same time, are much bluer in colour. This indicates that the newly identified stars are hotter and more compact. It was because of these characteristics that it was proposed to give this new class of variable stars the acronym BLAPS, i.e. Blue Large-Amplitude Pulsators. What kind of stars these were, however, remained an enigma.

The nature of the newly discovered stars

For the astronomers, these new stars posed a riddle. At first, they assumed that BLAPs could be hot dwarf stars since they have similar oscillation periods. Hot dwarf stars are old stars approaching the end of their lives. They generate their energy by means of the thermonuclear fusion of helium to form carbon. The Sun, being in an earlier phase of its life, is currently converting hydrogen to helium.

Read more at: https://phys.org/news/2017-08-mystery-pulsating-blue-stars.html#jCp

Science:
https://www.democraticunderground.com/122853040