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The Life Cycle of a Star
The Life Cycle of a Star
• Giant clouds of gas and dust
• The birthplace of stars!
Nebula
Eagle Nebula: 9.5 Light Years Tall!
http://hubblesite.org/gallery/tours/tour-m16/
Hydrogen gas is pulled together by gravity. It begins to spin, heats up, and becomes a star.
Creation of a Star
Cool Fact: Hydrogen in its core is converted into helium – this creates massive amounts of heat and light energy (this is called nuclear fusion)
A star will take one of two paths during its lifetime…
• Lifetime: Approximately 9 billion years as a main sequence star
Average Stars (such as our sun)
Hydrogen runs out. The outer layers of the star cool and expand outward
Red Giant – cool, large, red starCool Fact: When this happens to our Sun, scientists hypothesize that it will extend out as far as the Earth or even Mars.
The core of the Red Giant collapses and becomes a White Dwarf. The outer layers of the star drift away.
White Dwarf – Small, dense starCool Fact: Typically, a white dwarf has a radius equal to about 0.01 times that of the Sun, but it has a mass roughly equal to the Sun's. This gives a white dwarf a density about 1 million times that of water!
When the white dwarf runs out of energy, it eventually cools to become a black dwarf
• Black Dwarf – small, dead star
• Lifetime = approximately 10 million years
• Size = 10-1000 times the size of the Sun!
Path #2: Massive Stars!
Hydrogen runs out. The outer layers of the star cool and expand outward.
Red Super Giant – Very large, cool, red star
They continue to burn for a time and expand to an even larger volume.
Light Echoes From a Red SupergiantNASA Photo
When a star dies, it explodes into a radioactive cloud.
Supernova = extremely bright explosion (brighter than an entire galaxy)!
Kepler’s Supernova
Crab Nebula: The remains of a supernova
Cassiopeia A (Cas A, for short), the youngest supernova remnant in the Milky Way.
What is left after the Supernova is Neutron Star.
Neutron Star/Pulsar: When a Neutron Star begins to rotate, it is called a Pulsar.
Cool Fact: According to astronomer and author Frank Shu, "A sugar cube of neutron-star stuff on Earth would weigh as much as all of humanity!" Neutron stars can be observed as pulsars.
The core of a more massive star will collapse and create a black hole.
Gravity becomes so strong not even light can escape (which is why it’s called a “black hole”)
Video: Simulation of gravitational lensing by a black hole, which distorts the image of a galaxy in the background
http://commons.wikimedia.org/wiki/File:BH_LMC.png
Cool Picture: This is a simulated view of a black hole in front of the Large Magellanic Cloud.
