![]() ![]() This is why these clouds of material are often called stellar nuseries they are places where many stars form.Īs the protostar gains mass, its core gets hotter and more dense. The cloud doesn't collapse into just one large star, but different knots of material will each become it's own protostar. That hot core is called a protostar and will eventually become a star. As the knot collapses, the material at the center begins to heat up. Turbulence within the cloud causes knots to form which can then collapse under it's own gravitational attraction. These clouds are clouds that form between the stars and consist primarily of molecular gas and dust. (Credit: NASA/ESA/Hubble Heritage Team)Īll stars begin their lives from the collapse of material in a giant molecular cloud. ![]() Hubble image of the Eagle Nebula, a stellar nursery. The fate and life of a star depends primarily on it's mass. Using observations of stars in all phases of their lives, astronomers have constructed a lifecycle that all stars appear to go through. Stellar EvolutionĪ star is born, lives, and dies, much like everything else in nature. However, eventually these reactions will no longer generate sufficient heat to support the star agains its own gravity and the star will collapse. If the star is large enough, it can go through a series of less-efficient nuclear reactions to produce internal heat. When the star runs out of nuclear fuel, it comes to the end of its time on the main sequence. So, until it reaches the main sequence, hydrostatic support is provided by the heat generated from the contraction.Īt some point, the star will run out of material in its core for those nuclear reactions. This phase of the star's life is called the main sequence.īefore a star reaches the main sequence, the star is contracting and its core is not yet hot or dense enough to begin nuclear reactions. (Credit: NASA and the Night Sky Network)ĭuring most a star's lifetime, the interior heat and radiation is provided by nuclear reactions in the star's core. An astronomer could calculate the distance to this newly-discovered star by comparing its brightness as seen from Earth against the brightness for a certain color on the main sequence.Diagram showing the lifecycles of Sun-like and massive stars. A main sequence star of a particular color has a narrow band of brightness when seen from a standard distance. Nowadays, a new star may be classified as main sequence just by its color. A star located on the upper main sequence may only last a few million years. Our Sun is located on the lower main sequence and is predicted to last between 10 and 12 billion years. This type uses other elements (for example, carbon, nitrogen and oxygen) with higher atomic numbers as nuclear catalysts.īecause of these different types of fusion, stars on the lower main sequence last much longer than stars on the upper main sequence. The lower main sequence (cooler and less bright with a lower mass) produces energy by another type of nuclear fusion. The upper main sequence (hot and bright with the most mass) produces energy by one type of nuclear fusion involving only hydrogen and helium. Stars get the energy they produce through nuclear fusion of hydrogen into helium. Any star that has a mass greater than 1.5 times the Sun's mass is grouped into the upper main sequence any star with a mass lower than 1.5 solar masses belongs to the lower main sequence. The main sequence is sometimes divided into two parts. In general, the hottest and brightest stars (in the upper-left of the Hertzsprung-Russell diagram) also have the most mass. It does not spend so much time in its red giant phase. After this happens, the star is no longer on the main sequence. When a star begins to run out of fuel, it gets much bigger and colder and turns into a red giant. ![]() They stay on the main sequence for millions or billions of years. Stars are created from nebula and first appear on the main sequence. You can see an example of the band of main-sequence stars to the right. The main sequence appears as a band going from the upper-left (hot and bright) to the lower-right (cooler and less bright). Hertzsprung-Russell diagrams are graphs that measure each star's brightness against its temperature or color. This is because stars on the main sequence are highly stable, so they remain there a long time. Most of the stars in the Milky Way galaxy and most other galaxies are also main-sequence stars. Any star that is plotted in that area is a main-sequence star. The main sequence is a region on a Hertzsprung-Russell Diagram where most stars appear. Hertzsprung-Russell diagram showing stars in the main sequence. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |