Σουπερνοβα

[Star Defender]

A white dwarf star that will one day explode in a giant thermonuclear explosion has been discovered to be alarmingly close to our Solar System. Fortunately it’s not due to explode for another million years, but if it did it would fry every living thing on Earth, and eradicate the ozone layer.

An artist’s impression of a binary system with a white dwarf harvesting gas from a companion star, which forms a disc around the white dwarf. Image: ESO/L Calçada.

 

The white dwarf is found in the binary system T Pyxidis, in the Southern Hemisphere constellation of Pyxis, along with a fairly normal Sun-like companion star. The white dwarf – the burnt out remains of an ancient star – is leeching off its partner, stealing gas from it that consequently builds up on the surface of the white dwarf. Roughly every twenty years, this build up of gas becomes a little too dense and part of the surface explodes in what we call a nova. T Pyxidis was seen going nova in 1890, 1902, 1920, 1944 and 1967, but there has been nothing since, and nobody knows why we are overdue. However, new analysis of spectral observations of the white dwarf made with the now-defunct International Ultraviolet Explorer (IUE) have revealed that it is approaching the time when it will upgrade from a nova to a full blown supernova.

 

This happens when the white dwarf accumulates so much gas that it crosses the Chandrasekhar limit, which is 1.4 times the mass of our Sun, and matter becomes so dense within the star that a thermonuclear explosion engulfs the star, utterly destroying it. The IUE data implies that it is close to this limit, and is continuing to collect more gas from its companion at a rate of 200 trillion kilograms per second. Furthermore, the observations answer a long-standing puzzle; do the recurrent nova rid the white dwarf of all its extra mass, meaning it has to start over again after each eruption, or does it have some left over after each nova? The observations conclusively show that the white dwarf doesn’t shed all its extra mass with each eruption, so over time it is gaining mass, thus explaining how it can build up to the Chandrasekhar limit.

 

There is a caveat to all this. The new analysis of the data also places this doomsday star within 1,000 parsecs (3,260 light years) of Earth. White dwarf supernovae are among the most powerful supernovae in the Universe, and at this range the radiation from the explosion would fry everything on our planet, subjecting the surface to 100,000 ergs per square centimetre, and eradicating our protective ozone layer. (In contrast Betelgeuse, the red supergiant star in Orion due to blow up as a type II supernova, will be less powerful and no risk to life on Earth, even though it is only 640 light years away) Fortunately, we have about a million years before we have to worry about that; let’s hope that our motion through the Galaxy has moved us out of firing range by then.

[Στέφανος Σοφολόγης]

Ster Defender πρέπει να αναφέρεις και την πηγή της είδησης ή να δώσεις κάποιο link. Εντυπωσιακή είδηση, αν γίνει έτσι, δεν θα προλάβει ο Ήλιος να καταστρέψει τη Γη αλλά το παραπάνω άστρο.

[Star Defender]

Δεν δινω τις πηγες μου

[raxxla]

Δεν δινω τις πηγες μου

 

Αυτό είναι τουλάχιστον αντιδεοντολογικό.

Η πηγή (ιστοσελίδα, περιοδικό ή οτιδήποτε) πρέπει να αναφέρεται και για λόγους πνευματικής ιδιοκτησίας αλλά και κυρίως αξιοπιστίας. Εξάλλου, μπορεί κάποιος να ενδιαφέρεται να δει περισσότερα.

Αν δεν είναι αντιγραφή αλλά δικά σου λόγια, τουλ. μετάφρασε τα στα ελληνικά, είναι η επίσημη γλώσσα του φόρουμ!

[themis_kart]

Δεν δινω τις πηγες μου

 

Με google search σε μια πρόταση βγήκε το άρθρο Ηλία....Δεν πειράζει καλή καρδιά

 

http://www.astronomynow.com/news/n1001/05sn/

[Star Defender]

Το εχω ειδη πει στο Sn2007bi

Και εχω πει απο που ενημερωνομαι

ΧιΧιΧιΧιΧι

Ειδου η αποδειξη

http://www.astrovox.gr/forum/viewtopic.php?t=11306

[g.moralis]

Το βάζω εδώ για να μην ανοίγω καινούργιο νήμα.

 

New Supernova Lights Up Leo

http://www.universetoday.com/77618/new-supernova-lights-up-leo/