branch of astronomy
(Redirected from Astrophysicist)

Astrophysics is the study of how stars, planets, and other things in the Universe work, and how we can learn about them. Astrophysicists use physics and chemistry to explain what astronomers find and see.[1]

Astrophysics is also the study of how the Universe started and how it is changing with time. This part of astrophysics is called cosmology.


Early 20th-century comparison of elemental, solar, and stellar spectra

For a long time, bodies in the sky seemed to be unchanging spheres moving in a circle. But on Earth, growth and decay happened, and natural motion was in a straight line. Therefore, people thought the celestial region was made of a fundamentally different kind of matter from that found on Earth.

During the 16th and 17th centuries, natural philosophers such as Nicolaus Copernicus, Johannes Kepler, Galileo,[2] Descartes,[3] and Newton,[4] began to maintain that the celestial and terrestrial regions were made of similar material and were subject to the same natural laws.[5]

When they were able to work out how the planets moved, the science of astrophysics was born. Sir Isaac Newton realized that the same rules of mechanics that he had found on the surface of the Earth also could be used to predict how the planets moved. He said, "As above, so below". By this, he meant that we can study how things work on this planet to find out how things work in space.

Later scientists looked at the light from stars using spectroscopy. They were able to work out what they were made of, and how they changed with time.

Types of astrophysics

Supernova remnant LMC N 63A imaged in x-ray (blue), optical (green) and radio (red) wavelengths. The X-ray glow is from material heated to about ten million degrees Celsius by a shock wave generated by the supernova explosion.

There are two main types of astrophysics:

An example


Cecilia Helena Payne (later Cecilia Payne-Gaposchkin) published her doctoral dissertation at Radcliffe College in 1925. She had discovered that hydrogen and helium were the main content of stars. More than that, the spectral classes relate to the temperature of stars. Despite Eddington's suggestion,[6] her discovery was so unexpected that her dissertation readers told her to modify the conclusion before publication. Later research confirmed her discovery.[7][8]



  1. Keeler, James E. 1897. The importance of astrophysical research and the relation of astrophysics to the other physical sciences. The Astrophysical Journal, 6 (4): 271–288, Bibcode:1897ApJ.....6..271K, doi:10.1086/140401, PMID 17796068
  2. Galilei, Galileo (15 April 1989), Van Helden, Albert (ed.), Sidereus Nuncius or The Sidereal Messenger, Chicago: University of Chicago Press (published 1989), pp. 21, 47, ISBN 0-226-27903-0
  3. Edward Slowik (2013) [2005]. "Descartes' Physics". Stanford Encyclopedia of Philosophy. Retrieved 2015-07-18.
  4. Westfall, Richard S. 1980 (29 April 1983), Never at rest: a biography of Isaac Newton, Cambridge: Cambridge University Press, pp. 731–732, ISBN 0-521-27435-4{{citation}}: CS1 maint: numeric names: authors list (link)
  5. Burtt, Edwin Arthur [1924] 2003. The metaphysical foundations of modern science . 2nd ed, Mineola, NY: Dover, pp. 30, 41, 241–2. ISBN 9780486425511
  6. Eddington correctly speculated that the source was fusion of hydrogen into helium, which gave off enormous energy according to Einstein's equation E = mc2.
  7. Payne C.H. 1925. Stellar Atmospheres; a contribution to the observational Study of high temperature in the reversing layers of stars (PhD Thesis), Cambridge, Massachusetts: Radcliffe College.
  8. Haramundanis, Katherine 2007. "Payne-Gaposchkin [Payne], Cecilia Helena", in Hockey, Thomas; Trimble, Virginia; Williams, Thomas R. (eds), Biographical Encyclopedia of Astronomers, New York: Springer, pp. 876–878, ISBN 978-0-387-30400-7, retrieved July 19, 2015