Stars & Galaxies - Study Guide

Key Terms:

  • Nova - faint star that suddenly increases in brightness (100,000 times more) then fades back to its former brightness or dimmer

  • Supernova - star that suddenly explodes into a brilliant white star

  • Binary stars - 2 stars which orbit around each other (more than a 1/3 of stars are this type)

  • Star cluster - loose grouping of stars in space which probably formed from the same nebula

  • Variable stars - change in brightness in a regular pattern or cycle

  • Quasars - faint star-like objects which are larger than any star known and the most distant objects in the Universe

  • Nuclear fusion - two hydrogen atoms fuse together to form Helium and energy

  • Absolute magnitude /Luminosity - the real brightness of a star depends only on size and temperature

  • Apparent magnitude - the brightness we see on Earth depends on distance from Earth

  • Dwarf stars - can vary from the size of Earth to our Sun, which is a dwarf

  • Giant stars - example would be Arcturus

  • Supergiant stars - more than 2,000 times the size of our Sun (Betelgeuse, Antares)

Questions?

  • What color is associated with the hottest stars?

    • Blue

  • What color is associated with the coldest stars?

    • Red

  • What is a synopsis of the life cycle of a star (generally)?

    • A star begins as a nebula, it can then become a main sequence star or a massive star (depending on the size), then it will burn to either a red giant or red super giant. If it is a red giant, then it next becomes a planetary nebula. If a red super giant, it becomes a supernova. At this point, the supernova or planetary nebula allows the star’s life cycle to be a cycle, turning back into a nebula. However, if this does not occur, then a star can either become a few things. If it was a supernova, it could then be a neutron star or black hole. If it was a planetary nebula, it could die slowly, by going from white dwarf, to brown dwarf, to lastly black dwarf before death.

  • What is the life cycle of the Sun?

    • Will continue to burn for another 5 billion years as a (dwarf) yellow star, when fuel expires it will swell into a red giant as large as Mars’ orbit, then will collapse into a white star where it will cool to death.

  • What is our closest spiral galaxy?

    • Andromeda Galaxy, which is 2.2 million light years away

  • What type of energy can stars produce?

    • Heat (infrared) energy

    • Light energy

    • Radio waves

    • Gamma and Cosmic rays

    • X-rays

    • Ultraviolet rays

  • What causes star brightness?

    • Distance from Earth

    • Temperature

    • Size of star

  • Fill in Diagram: What categories of stars go in the blank spots on the H-R diagram? Shade in the colors of the stars.

  • Hertzsprung-Russell Diagram – a scatter plot of stars showing the relationship between the stars' absolute magnitudes or luminosity versus their stellar classifications or effective temperatures. (Shows the brightest stars and their classifications)

    • What our Sun is classified as - Main Sequence star (dwarf) and G2

    • What most stars are classified as - Main Sequence stars

    • Which stars and colors are the most massive/least

      massive - Colors that are most massive are mostly blue, Stars are Super giants.