Radio signals from the pulsar PSR B1257+12 in the constellation Virgo led Penn State professor of Astronomy and Astrophysics Alexander Wolszczan to discover the first planets ever known outside our solar system. He discovered the planets in 1991 and confirmed their existence in 1994.
Wolszczan used the worlds largest radio telescope in Arecibo, Puerto Rico, to time the radio signals coming from a distant tiny neutron star in the constellation Virgo, 7,000 trillion miles from Earth. These measurements helped him to determine that two of the planets are similar in mass to Earth and the other is about the mass of the Moon.
Until Wolszczan's discovery, the only known planets were in our solar system. His work suggests that planets may be more common in the universe than astronomers had previously thought. It will also help astronomers to understand how planets, including Earth, are formed. The planets Wolszczan found probably don't support life because the tiny pulsar they orbit bombards them with deadly radiation. However, his discovery increases the chances that somewhere in the universe planets may exist that, like Earth, are capable of supporting life.
If you wish to learn more about the pulsar planets, click here. Also, please, refer to the following selected publications:
Konacki, M. & Wolszczan, A. "Masses and Orbital Inclinations of Planets in the PSR B1257+12 System" 2003, ApJ, 591, L147.
Hansen, B. M. S. “Stellar Collisions and Pulsar Planets” 2001, in ASP Conf. Ser. 263, Stellar Collisions, Mergers, and Their Consequences, ed. M. M. Shara (San Francisco: ASP), 221.
Miller, M. C., & Hamilton, D. P. “Implications of the PSR 1257+12 Planetary System for Isolated Millisecond Pulsars” 2001, ApJ, 550, 863.
Wolszczan, A., Hoffman, I. M., Konacki, M., Anderson, S. B., Xilouris, K. M. "A 25.3 Day Periodicity in the Timing of the Pulsar PSR B1257+12: A Planet or a Heliospheric Propagation Effect?" 2000, ApJ, 540, 41.
Konacki, M., Lewandowski, W., Wolszczan, A., Doroshenko, O., & Kramer, M. "Are There Planets around the Pulsar PSR B0329+54?" 1999, ApJ, 519, 81.
Wolszczan, A., "Searches for Planets Around Neutron Stars'' 1997, Celestial Mechanics, 68, 13.
Wolszczan, A. "Confirmation of Earth--Mass Planets Orbiting the Millisecond Pulsar PSR B1257+12" 1994, Science, 264, 538.
Wolszczan, A., & Frail, D. A. “A Planetary System around the Millisecond Pulsar PSR 1257+12” 1992, Nature, 355, 145.
DuBois, C., “Planets from the Start”,
1997, Research/Penn State, vol. 18, No. 3, p.28.
Stephens, S., “Second Chance Planets”, 1996, Astronomy, January 1996, p. 50.
Fienberg, R., "Pulsars, Planets, & Pathos", 1992, Sky & Telescope, vol. 83, No. 5, p. 493.
Folger, T., "Forbidden Planets", 1992,
Discover, vol. 13, No. 4, p. 38.
Mikołajewski, M. & Mikołajewski, J., "Kosmiczne
zegary Aleksandra Wolszczana", 1992, Postępy Astronomii, vol. 40, No. 2,
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