Star lifecycle Star Lifecycle Some background Knowledge Nuclear

Star lifecycle

Star Lifecycle Some background Knowledge: ØNuclear fusion - combining smaller elements into larger elements. Leftover mass is converted into energy. (Done best in stars only) ØNuclear fission - splitting larger elements into smaller elements with the release of energy in the process. (Done in nuclear power plants here on Earth)

Star Lifecycle What is a star? Ø A star is a really hot ball of gas, with hydrogen fusing into helium at its core. Ø Stars produce light energy, heat energy, and electromagnetic waves. Ø Stars spend the majority of their lives fusing hydrogen, and when the hydrogen fuel is gone, stars fuse helium into carbon. Ø The more massive stars can fuse carbon into even heavier elements like Iron (Fe).

Star lifecycle ØA nebula is a cloud of dust and gas, composed primarily of hydrogen (97%) and helium (3%). ØWithin a nebula, there are varying regions when gravity causes this dust and gas to “clump” together.

Star Lifecycle ØAs these “clumps” gather more atoms (mass), their gravitational attraction to other atoms increases, pulling more atoms into the “clump. ” ØAll stars begin as Nebulae ØGravity pulls a nebula together into a protostar (If it has enough mass)

Star Lifecycle Ø A star is officially born when nuclear fusion starts ØIf a star doesn’t have enough mass to start nuclear fusion, it becomes a brown dwarf.

Star lifecycle Ø Stars life spans depend on their mass Ø Stars with less mass actually live longer because they burn slower. Ø Massive and super massive stars live fast and hard and die young. Ø Our sun is 4. 6 billion years old. Currently halfway through its lifespan. ØStars spend the majority of their lives fusing Hydrogen into Helium (the main-sequence stage)

Star lifecycle • When the hydrogen fuel is gone, stars fuse Helium into Carbon. • The more massive stars can fuse carbon into even heavier elements. • Iron (Fe)is generally the largest element being fused in stars. • Larger elements than Fe are usually produced via supernovas

Star Lifecycle

Star Lifecycle • When a star has finished it’s main sequence and begins to die: Death of Stars: Ø After a star runs out of fuel, it becomes a white dwarf, a neutron star, or a black hole. Low to medium mass stars: Ø Star ---> red giant ---> planetary nebula ---> white dwarf ---> black dwarf

Star lifecycle

Star lifecycle High Mass Stars: ØStar ---> supergiant ---> supernova ---> neutron star or black hole (most massive stars) ØPulsars – Spinning neutron stars that give off pulses of radio sources. Left over from super massive star supernovas. ØBlack Holes – From the most massive stars (More than 40 times bigger than our sun). Ø Nothing can escape the gravity of a black hole, not even light.

Star Lifecycle

Star lifecycle Our sun: (An average Joe type of star) ØAbout half way through it’s life. ØWe can calculate an approximate mass and rate at which it is burning fuel (fusion Hydrogen to Helium). ØFrom those numbers we can make a good estimate of just how long the sun has left before it goes Red Giant to white dwarf finishing as a black dwarf eventually.