What is a star?
|Automatic translation||Updated June 01, 2013|
A star is a aster like the sun shining through nuclear reactions that occur in the middle.
The number of stars in the universe is estimated between 1022 and 1023. Apart from the Sun, the stars are too faint to be observed in daylight.
Image: Birth of a star, image made from data of X-ray telescope Chandra (blue) and data from the Spitzer Infrared Telescope (red and orange). NB: The astronomers classify stars in dwarf or giant.
Neutron stars are very small but very dense (1 billion tons per cubic centimeter). They concentrate the mass of a star like the Sun in a radius of about 10 km, corresponding to what is called the Chandrasekhar mass. These are the remnants of very massive stars with more than ten solar masses.
If it turns quickly on its own when it projects along its magnetic axis a thin brush of radiation, it is then called "pulsar".
Image: IC 443 follows a stellar explosion, the ultimate fate of massive stars. In this false color composite image, we see the remains of the supernova still vibrating across the radio spectrum (blue), optical (red) and x-rays (green).