From Earth a Supernova looks like a bright new star, nova means 'new' so that is where the name comes from. Some heavy and dense stars end their life as Supernova, a phenomena that does not occur very often.
Birth of a dying star
The largest part of its life a star is a stable sphere of hot gasses.
The lifetime of a star depends on its mass, very dense stars (five to thirty
time the mass of the Sun) have a relatively short live.
When a star reaches the end of its life cycle
the outer parts of the star fall towards the nucleus because of an imbalance
between gravity and energy generated
by its center. When the star has depleted its sources of nuclear energy and
can no longer produce the expansive forces that supports the star against
the compressive force of its own gravitation: the star collapses. Sometimes
this goes so terribly fast (less then a second), that it explodes. The
remainders of the star are thrown into the Universe with speeds up to several
ten thousands kilometers per second.
The result is that the star will have a very high
luminosity during the several months, when it became a supernova. Out of the matter
that is blown away and the shockwaves generated by the explosion occasionally a new star will be
born. Sometimes the nucleus of the star finally remains as a black
hole or as a neutron star, however
most stars end their lives as white
dwarfs.
A rare phenomena
Supernovas are not a daily occurance. By scientific calculations it is concluded
that they occur only once every fifty years in our Milkyway galaxy. Until
1987 the famous astronomer Johannes
Kepler was the last person to see a Supernova with his naked eyes.
And that was in 1604! Probably they have never been seen because of the many dense dustclouds
in our Milkyway galaxy.
The bright spot near the yellow arrow is Supernova SN 1987a. It is located in the Cloud of Magelhaese, near the Tarantula Nebula the lightspots you can see to the left. |
Supernova SN 1987a
On February 24, 1987 it finally happened. With telescopes at the European Southern Observatory (the largest observatory of the southern hemisphere), on top of the La Silla mountain in Chili, the Canadian astronomer Ian Shelton discovered a new star in the Cloud of Magelhaese: The Supernova SN 1987a. The SN 1987a appeared to have originated from a Blue
Giant, and not as expected in accordance of the theory of star evolution
from a Red Giant.
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