A SUPERNOVA IN THE MAKING!

[ΙΑΝΟΣ]

Παιδιά διαβάστε την πιο πρόσφατη και πολύ ενδιαφέρουσα δημοσίευση του Dr. Matthew Templeton που έκανε για την AAVSO σχετικά με τον αστέρα P Cyg.

 

Η αναδημοσίευση είναι από την ιστοσελίδα της AAVSO: http://www.aavso.org/

 

A SUPERNOVA IN THE MAKING - Dr. Matthew Templeton, AAVSO

This time of the year is a great time for astronomy, since these months bring into view the densest star fields of the Milky Way. Southern hemisphere observers are treated to the awesome view of the Galactic bulge, while northern observers get lovely Cygnus all evening long. Cygnus has some remarkable objects for variable star observing, including the high-amplitude Mira variables Chi, R, and U Cyg that all come close to naked eye visibility during maxima, and the famous long-period Cepheid X Cyg. Another bright variable in Cygnus is only modestly variable today, but will one day -- some day -- put on a show seconded only by our own Sun.

P Cygni is a supermassive star, freshly-born from one of the many star-forming regions in Cygnus. At a modest apparent magnitude of 4.5, it appears somewhat nondescript, but this hides the fact that it's one of the most luminous stars in our Galaxy. It was first discovered as an apparent Nova in 1600 by Blaeu, and remained visible for nearly a quarter of a century -- much longer than any "novae" we know today. It returned later in the seventeenth century and has varied between 4.5 and 5.5 since then. We now know that it isn't a traditional nova, but a Luminous Blue Variable (LBV). These are the most massive stars known, doomed to live for just a few million years before their nuclear fuel runs out, and they die spectacular deaths as supernovae.

Supermassive stars are super-rare; only a handful exist in any star-forming galaxy at a given moment in time, and they're *only* found in galaxies currently forming stars. Their lives are so short that they come and go only during active star formation. The brightest (by far) in Earth's skies is the great eta Carinae, and its famous "homunculus" nebula was created by its own huge wind. P Cygni also has a wind, and the spectroscopic nebular line feature of blue-shifted absorption tails with red-shifted emission are given the name "P Cygni profiles" for the phenomenon first discovered in P Cygni.

P Cygni is currently (as of June 19, 2007) around m(vis) of 4.8, and it has varied by about half a magnitude around that value for the past several decades. Arne Henden released a Special Notice (#47, 2007 May 19) requesting monitoring of P Cygni, and visual observations are certainly welcome as always. It's a treat within the rich star fields of the July Milky Way, but don't expect it to vary by much over the observing season. But who knows -- if you're lucky, you might just be the first person to catch the first light of a Galactic supernova in nearly 400 years.

 

Φιλικά, AAVSO DXA