What are the core, Mantle, and crust layers in terrestrial Planets?
Core: The highest-density material, consisting primarily of metals such as nickel and
iron, resides in the central core.
Mantle: Rocky material of moder
Our galaxy: the milky way Total mass: 1 trillion Msun ~100 billion Msun is stars ~few 100 billion Msun is ags ~500 billion Msun is dark matter Molecular clouds are really the dark Nebula May also be pre-star forming clouds Give galaxy its splotchy appeara
White Dwarfs Are the remaining cores of low and intermediate mass stars. Sirius, the brightest star in the night sky, has a companion that is a white dwarf. Very dense degenerate matter (mostly carbon) White dwarfs begin very hot, cool off and grow dimmer
White dwarfs (WD) Accreted material (mostly H) builds up in a thin layer on the White Dwarf Surface The temperature of accreted matter eventually becomes hot enough for hydrogen fusion (~10 million K) Fusion begins suddenly and explosively, causing a nova
Star stuff Recall that a stars mass sets its lum., temp., M-S lifetime An on-going struggle between pressure and gravity. What happens when fuel runs out also depends on stars mass
3 mass caegories o Hiogh-mass stars > 8 Msun (supernova explosion) o Inter
The evolution of the sun ( a typical low mass star). 1) Deplete H in core 2) Core contracts, heats up, rapid H burning in shell, star expands as red giant. 3) Helium flash 4) Stable core helium fusion, shell H fusion, becomes a horizontal branch star. 5)
White dwarf 8) remnant core is a WD Compound of degenerate matter (C, O, sometimes He) Are small (size of earth) but extremely dense. Will slowly cool, becoming invincible after billions of yrs.
Life track of a sun-like star Sun>subgiant>red giant>double
Star stuff Core of a high mass star is hot enough to fuse C (and heavier elements) Begins at ~600 million Kbut lasts only a few hundred yrs. High-mass stars make the elements necessary for life CNO cycle can change C into N and O Helium capture High core
Pulsars Is a neutron star that beams radiation along a magnetic axis that is not aligned with the radiation axis. The radiation beams sweep through space like lighthouse beams as the neutron star rotates A neutron star will be a pulsar if 1) magnetic axis
Mass transfer in close binaries Accretion onto a NS released tremendous energy. Those systems are called X-ray binaries Some emit 100,00 Lsun just in X-rays Hot enough to continually fuse H on surface, building up a layer of He X-ray bursts Quickly become
Black hole binaries Why cant we see inside Recall escape velocity -the velocity needed for something to escape the gravitational pull of an object For earth, Vescape ~ 11.2 km/s For moom, Vescape ~2-4 km/s For sun, Vsecape ~ 618 km/s For a black hole, Ves
Galactic recycling Supernova remnant cools and begins to emit visible light as it expands SN remnants are a galaxys particle accelerators, accelerating charged particles to near light speed Radio emission from spiraling Cosmic rays from SN Cosmic rays hig