The mystery of the pulsating blue stars

[Sagan]

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-Universit?t Erlangen-N?rnberg (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-myster...stars.html#jCp

[CloudMaker]

Maybe they are blue because they have ice..... ice means they have water.... could they have life?

[Sagan]

• the color of a star depends on its surface temperature. But a blue star doesn’t emit only blue light, nor does a red star emit only red light. They emit visible light of all colors to some degree. It’s just that their spectrum peaks at a particular color.

• So why are there blue stars, yellow stars, red stars, but no green stars? As it turns out, there are green stars, that is, stars that radiate much of their light in the green part of the spectrum. But the total combination of the full range of colors of a “green” star appears white to our eyes. If you pass the color from a whitish star through a prism, you’ll see all the colors, including green, spread out in a continuum.

• Astronomers came to understand that bluer stars are intrinsically brighter because they are more massive than white or red stars, and more massive stars burn much faster and hotter than less massive stars. The bluish type-O stars, for example, are only 30-50 times more massive than yellow-white stars like our sun. But O stars burn a million times brighter, so they have far shorter lifetimes. O and B stars only last a few million years before they die in spectacular supernova explosions, while cooler and less massive K and M stars burn steadily for billions of years.

• Some 88% of stars in the universe seem to be the cooler type K and M. Only 1 in 3,000,000 stars are type O. Even middle-weights like our type-G Sun comprise only 8% of all known stars.