Some Puzzling Stellar Plastic Surgery

Want to see some of the oldest stars in the cosmos?  Follow European Southern Observatory’s gaze out to the globular star cluster NGC 6362.  It belongs to the Milky Way, and contains tens of thousands of very ancient stars. This cluster has many stars that have aged to become red giants. But, there are some stars here that look–well — almost young. Blue. Hot.

Those blueish hotties are called “blue stragglers” and they’re passing as younger stars.

How could this be?

Astronomers know that all of the stars in a globular cluster formed from the same material at roughly the same time. For most globulars, that means about  10 billion years ago. They have earned the right to look old and red. Yet, blue stragglers are bluer and more luminous — and hence more massive — than they should be after ten billion years of stellar evolution. Blue stars are hot and consume their fuel quickly, so if these stars had formed about ten billion years ago, then they should have fizzled out long ago. How did they survive?

Currently, there are two main theories that might describe how blue stragglers came about. The first suggests that stars collide and mergel which would transform them into hotter more massive objects.

The other describes a transfer of material between two companion stars.  Neither theory has been proved, but that’s why astronomers want to observe more about these young-looking stellar oldsters.

The basic idea behind both of these options is that the stars were not born as big as we see them today, but that they received an injection of extra material at some point during their lifetimes and this then gave them a new lease of life.

This brilliant ball of stars lies in the southern constellation of Ara (The Altar). It can be easily seen in a small telescope. It was first spotted in 1826 by the Scottish astronomer James Dunlop using a 22-centimeter telescope in Australia. The image shows this cluster in all its starry glory, complete with oldsters passing as young beauties.