Stars and the Mystery Particle

    Stars and the Mystery Particle

The Carina Nebula (Source: Wikimedia Commons)

For centuries scientists and mathematicians around the world have been fascinated by the stars. Stars could be defined as celestial objects which emit light of their own by converting hydrogen into helium by the process of nuclear fusion in their cores.

Nebulas are the birthplace of stars and are mainly composed of dust and gases. In a nebula, clumps of gases start attracting the surrounding matter into them due to their gravity and the matter crunches down in a disk, that is the beginning of becoming a star. And finally at few million degrees, a transformation takes place, fusing hydrogen atoms into helium atoms and with a burst of nuclear energy a star begins to shine.

A nebula can give birth to many protostars - young stars which are still gathering gases from their parent nebula. 

"Nature doesn't form stars in isolation," Mark Morris, of the University of California at Los Angeles, said in a statement. "It forms them in clusters, out of natal clouds that collapse under their own gravity."

Life cycle of stars (Source: Wikimedia Commons)

All the Main Sequence stars are undergoing fusion of hydrogen atoms into helium atoms and are characterized by their source of energy. The majority of the stars in the universe, including our sun, are main sequence stars. The mass of these stars can range from about a tenth of the Sun to a few hundreds. The duration of a star to be in main sequence depends on its mass. The more massive a star, the more fuel it has which burns faster, and shorter its life.  Stars live most of their life at this stage. Stars like Sun still have about 10 billion years in this stage, more massive stars live for a few million years and smaller stars, like a red dwarf, can live up to 50 billion years. Once a star runs out of its fuel, it evolves into a red giant or a red supergiant.

Red giants form from the stars with their mass ranging from 0.4 to 8 solar masses. As stars run out of their fuel, their core contracts producing more energy. This energy pushes the surface of the star making it expand. As the size is increased, energy is spread which cools the surface temperature a little making them appear red. A red giant can live for few hundred million years and after running out of fuel, there is nothing left to burn so it sheds off its outer layers and its core gets compressed due to which size of the star decreases and this type of star is called a white dwarf. White dwarfs shine a little because they are still hot. After an extremely long time, their core starts cooling down and later the whole star. And now these stars have no light to emit and are called black dwarfs.

Red supergiants form from the stars with mass more than 8 times the Sun. They are a bit like red giants, but are hotter and more massive. These red supergiants have greater gravitational pressure than red giants and can fuse heavier elements like helium into carbon and carbon atoms into magnesium. After they run out of fuel, their mass determines whether they will turn into black holes or into neutron stars. More mass is required to turn into a black hole than a neutron star.. Or in some cases, a red supergiant could end up being a supernova. During this event, a supernova could produce more energy than the Sun during its 10-billion-year lifetime. A supernova can be predicted by scientists hours before its light reaches the Earth by detecting its neutrinos. If nothing can travel faster than light, then how can they reach earth before the light of the supernova?

In February 1987, scientists detected 25 neutrinos of a supernova 3 hours before its light reached earth and later, they named the supernova 1987A. Neutrinos are the most abundant particles in the universe. Trillions of them are passing through you right now. They are the least interactive particles and can pass through 100 light years thick wall of steel without even changing their velocity. When a star is about to turn into a supernova, its core releases a wave of energy which launches neutrinos nearly at the speed of light. These neutrinos then leave the star in just a few seconds, whereas photons take time.

As far as scientists know, neutrinos never decay, which means they could last forever. Now many neutrino detectors are built around the world. Some scientists think studying neutrinos can lead them to the origin of the universe, the big bang.