How long stars live

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University of Toronto St. George
Astronomy & Astrophysics
Stefan Mochnacki

Astronomy 1 February 15, 2010 How long stars live N Most stars form in clusters. We can use the H-R diagram of a cluster to figure out how old the cluster is. o Look at a cluster, young stars: lots of gas and dust. Older no gas and dust from when it was formed o Measure luminosity and spectral classessurface temps. Then you plot them all up. o Pleiades , you can see with your naked eye. o Peeling away from 100 million years, that tells you that every star in that cluster is lifetime of less than 100 million years you know they have already died. o All of the young stars are dead in the 7Gyr, only the old stars are left N The one that turns away form the main sequence closer to the bottom is the oldest cluster. Star Formation N Stars are born and the die. N Spectroscopy, hydrogen emits or absorbs a HUGE amount of red light. N Dark region is a region of presence of a lot of gas and dust which blocks out gas and light (DUST LANE) N Between the spirals balls of hydrogen balls and dust are related N Red Nebulae hydrogen gas. Aslo, dust and blue stars N Lots of blue stars lots of young stars Most distant stars we can see are blue because although these stars are rare, they are extrememly luminous. N Blue stars are rare and exotic. N Elliptical galaxy, functionally dead. Usually enormous with trillions of stars. N Sentoras A, lots of gas, eating up another galaxy. N Taking pictures in multiple parts of the electromagnetic spectrum is essential to understand star formation. N Infrared light shows cold dust. N Where there is a lot of dust there are a lot of red nebulae and blue stars. N Orion, 2 blue stars. Orion Nebula, full of young stars embedded in the gas.
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