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  • Redshift and Hubbles Law - NASA
    Redshift and Hubble's Law For very far objects (beyond about 1 billion light-years) none of the above methods work Scientists must move from direct observation to using observations in conjunction with a theory The theory used to determine these very great distances in the universe is based on the discovery by Edwin Hubble that the universe is expanding
  • StarChild: A Learning Center for Young Astronomers
    Well that's a redshift, redshift If the star is moving away By reading Doppler Shifts of all we see in the skies (clusters of galaxies, near and far) We get the big picture and a big surprise (redshifts going, redshifts going) The Universe is growing and expanding away (galaxies are speeding, speeding away) But maybe gravity will shrink it back
  • How old is the universe? - NASA
    We do not know the exact age of the universe, but we believe that it is around 13 billion years - give or take a few billion Astronomers estimate the age of the universe in two ways: (a) by looking for the oldest stars; and (b) by measuring the rate of expansion of the universe and extrapolating back to the Big Bang As Old as the Stars One way astronomers estimate the age of the universe by
  • How do we measure the distances to things in space? - NASA
    StarChild Question of the Month for November 2001 Question: How do we measure the distances to things in space? Answer: It is not an easy thing to measure the distances to objects in the since these objects are usually very far away We can't just run out there with a ruler! To measure distances in the universe, we will need to construct what is commonly referred to as a "cosmic distance
  • StarChild: Quasars
    Despite their brightness, due to their great distance from Earth, no quasars can be seen with an unaided eye Energy from quasars takes billions of years to reach the Earth's For this reason, the study of quasars can provide astronomers with information about the early stages of the universe The word quasar is short for "quasi-stellar radio source" This name, which means star-like emitters
  • StarChild: A Learning Center for Young Astronomers
    Well that's a redshift, redshift If the star is moving away By reading Doppler Shifts of all we see in the skies (clusters of galaxies, near and far) We get the big picture and a big surprise (redshifts going, redshifts going) The Universe is growing and expanding away (galaxies are speeding, speeding away)
  • StarChild: Quasars
    Quasars give off huge amounts of energy They can be a trillion times brighter than the Sun! Astronomers think that quasars are located in galaxies which have black holes at their centers The black holes may provide quasars with their energy Quasars are so bright that they drown out the light from all other stars in the same galaxy The word quasar is short for quasi-stellar radio source
  • What is a brown dwarf? - NASA
    Question: What is a brown dwarf? Answer: In order to understand what is a brown dwarf, we need to understand the difference between a star and a planet It is not easy to tell a star from a planet when you look up at the night sky with your eyes However, the two kinds of objects look very different to an astronomer using a telescope or spectroscope Planets shine by reflected light; stars
  • StarChild: Cosmology - NASA
    For more than ten years astronomers studied the expansion of the universe by measuring the redshift and brightness of distant supernovae By 1998, enough information had been gathered to lead scientists to the startling discovery that the expansion of the universe is not slowing but accelerating
  • Supernovae - NASA
    Supernovae At large distances (up to about 1 billion light-years), astronomers can no longer use methods such as parallax or Cepheid variables At such large distances, the parallax shift becomes too small and we can no longer even see individual stars in galaxies Astronomers then turn to a series of methods that use "standard candles", that is, objects whose absolute magnitude is thought to





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