Lives of Stars

lifetimes of stars how long a star lives depends on its mass greater the mass- shorter the lifetime

star’s life cycle

nebula= large cloud of gas & dust birthplace of stars

Image by NASA/STSCI/Nolan Walborn/Hubble Heritage Team nebula Image by NASA/STSCI/Nolan Walborn/Hubble Heritage Team

1. protostar Earliest stage in star’s life Contracting cloud of gas & dust w/ enough mass to make star

2. main sequence star (developed star) sun

start to run out of fuel- outer layers expand 3. red giant or supergiant start to run out of fuel- outer layers expand

depends on star ’s mass When star runs out of fuel, becomes : white dwarf or neutron star or black hole depends on star ’s mass

small & medium stars become white dwarf- cooled blue-white core left behind about size of Earth same mass as Sun

This Hubble Space Telescope image shows Sirius A, the brightest star in our nighttime sky, along with its faint, tiny stellar companion, Sirius B. Astronomers overexposed the image of Sirius A [at center] so that the dim Sirius B [tiny dot at lower left] could be seen.

when white dwarf stops glowing 5. black dwarf- when white dwarf stops glowing

giant & supergiant stars 4. supernova- explosion of a dying giant or supergiant star one of the most dazzling events in the universe

supernova

5. neutron star- small, dense star - 3 X mass of Sun

pulsar Spinning neutron star Emits pulses of radio waves

5. black hole- most massive stars form from stars that have 40 times the mass of sun gravity is so strong that nothing can escape- not even light x-rays detect them

The remains of the most massive stars collapse into black holes. This artist’s impression shows a black hole pulling matter from a companion star.

Not even light can escape from a black hole.

(unsequenced human life cycle page) supernova nebula developed star black hole protostar supergiant (unsequenced human life cycle page)

protostar nebula protostar protostar

Life Cycle of a Star nebula= huge cloud of gas & dust protostar= beginning of star Life Cycle of a Star developed star (main sequence star) red giant or supergiant= star expands, outer layers cool low mass star massive star white dwarf= dim star that forms from a red giant supernova= enormous explosion of a giant star very high mass high mass star black dwarf= runs out of fuel dead star black hole= core collapses to a tiny point with a very strong gravitational pull neutron star= dense remains of a massive star’s core