the journey of stars

Stars are the main building blocks of galaxies. Their age, distribution and composition show the history and evolution of the galaxy. Stars manufacture and distribute carbon, nitrogen and oxygen and they share many characteristics with their planetary system, thus they are important to astronomy

Star Formation

Stars are born within clouds of dust such as the Orion Nebula. Knots with sufficient mass form in these clouds, that the gas and dust begin to collapse, causing the material in the center to heat up, this protostar will one day become a star. The fact that the collapsing clouds break up explains why stars in the milky way come in pairs or multiple form.

Not all the material formed while the cloud collapses ends up as part of a star, it can become planets, asteroids, comets or remain as dust. In some cases, the cloud may not collapse at a steady pace, causing varying brightness when looked at. A recent example of this was found in January 2004 by amateur astronomer James McNeil.

Main Sequence Star

From the beginning of the collapse to its adulthood, a star like the sun needs 50 million years. Our sun will remain in this mature phase for approximately 10 billion years.

The nuclear fusion of hydrogen fuels stars to form helium in their interiors. Energy coming from within the stars provides the pressure that prevents the stars from collapsing and makes them shine.

Main Sequence stars have a variety of brightness and color and they are classified accordingly. The red dwarfs, the smallest stars may contain only 10% the mass of the sun and emit only 0.01% its energy, yet they are the most numerous and live tens of billion of years. The hypergiants, on the other hand, are up to 100 times more massive than the sun. Though the hypergiants emit hundreds of thousands of times more energy than the sun, they live only a few million years. Today the milky way only has a few hypergiants.

Stars and Their Fates

The bigger the star the shorter it lives. When the nuclear reactions inside a star stop, there is no energy produced, which causes the core to collapse and become hotter. The hydrogen outside the core continues its fusion, but the hot core pushes the outer layers of the star outward, cooling them and transforming the star into a red giant. Depending on the size of the star, its collapsing core may be hot enough to cause more nuclear reactions, however these are usually unstable, causing the star to form a cocoon of gas and dust and its ultimate fate depends only on the size of its core.