Birth and Life of Stars

¶ … Birth and Life of Stars and Dwarfs

Stars twinkle and shine pretty in the night sky but they are actually complicated heavenly bodies. They are like us in that they are born, live their stellar lives, and then die. The early phases of a star's life begins when an "early phase of gravitational collapse," (Dasch) forms a "stellar embryo" (Dasch). Gas falls into the embryo, heating it up and when the embryo becomes warm enough, it begins resisting gravity. At this point, the embryo is called a "protostar" (Dasch). Grace Wolf-Chase maintains that this gas is "vast agglomerations of gas and dust" (Chase). Some of matter around the protostar begins to accumulate in a disk shape, rotating around it. Forces of gravity cause the disk to pick up speed and move toward the center. However, the gas and dust must slow down in order to fall onto the protostar. Chase notes, "Recent theoretical work suggests that this is accomplished through the interaction of the material with magnetic fields that thread the disks of protostars" (Chase). The protostar's magnetic field is eventually bent into an hourglass shape, which throws off gas, which slows down the disk. Matter from the disk is now able to fall onto the protostar. Chase surmises, "Planets may eventually form within the disk" (Chase). The resulting mass of the protostar will shape how it evolves. Stars evolve in patterns, which is also associated with their mass. There are generally three types of stars, which are high-mass stars, intermediate mass stars, and low-mass stars. In early stages, stars produce energy through a "stage of nuclear fusion called hydrogen-burning" (Dasch). Again, depending on the star's mass and density, more stages may follow this first stage. All stars finally stop burning and explode, an act that completes the star's evolution.

Jeffrey Hall observes, "Nature is filled with symmetries, and this is one of the most enchanting symmetries. The death of one star triggers the birth of new stars" (Hall). Stars die as a result of the hydrogen-burning process. As hydrogen burns, the star's core grows. Stars that have less than half of our Sun's mass will eventually burn off all of their hydrogen and "end their lives as helium white dwarfs" (Dasch). Stars that have larger masses will experience a growth in their core, which increases its temperature until nuclear fusion begins to take place. This takes place in the form of burning helium and when this starts, the star does not expand but instead becomes hotter. When all of the helium is burned away, the core of the star will shrink and its outer layers will expand and cool.

This process will eventually turn the star into a super giant. The star is still expanding, forcing the outer layers to drift from the stars gravitational force. This loss is continuous and when the star's mass becomes less than times as massive as our Sun's mass, we call it a carbon-oxygen white dwarf. White dwarfs are just one of the ways that a star can die. However, it is important to note that even when a star reaches white dwarf state, it can still become a black dwarf when it cools enough. This mass floats through space "unseen and undetected through space. It takes a very long time for a white dwarf to cool enough to become a black dwarf, and many astronomers suspect the galaxy hasn't aged enough for any to have yet formed. If any have formed, it will not be easy to find them" (McGrath). While space may look like it is not changing from Earth, we can know that it is - even in death. Red dwarf stars are the result of a dying star that is very small - anywhere from 65% to 3% of our Sun's size. Red dwarfs are cool and very faint; however, there are many of them sprinkled throughout the universe. Stars can also die and become brown dwarfs, which are actually pseudostars or "failed stars" (NASA) with not enough gas to fuel the "hydrogen-fusion reaction that powers true stars" (Heckert). Brown dwarfs are larger than red dwarfs are but they do not have enough mass to become stars.