NASA Scientists are learning more about white dwarf stars. In fact, new data has shaken up practically everything that was understood about these objects.
New observations have been done in the outer space lab, Suzaku Observatory - a joint project with the Japanese. ”The discovery team, led by Yukikatsu Terada of the Institute of Physical and Chemical Research (RIKEN) in Wako, Japan, was not expecting to find a white dwarf…”
(Note: More on dwarf stars, definition and formation, http://en.wikipedia.org/wiki/Dwarf_star
Portions of the Astronomy.com article and images of the sparkling dwarf are below:
“White Dwarf Pulses Like A Pulsar” January 3, 2008
http://www.astronomy.com/asy/default.aspx?c=a&id=6442
Current knowledge of white dwarfs is being challenged by new discoveries.- NASA’s Goddard Space Flight Center
| The white dwarf in the AE Aquarii system is the first star of its type known to give off pulsar-like pulsations that are powered by its rotation and particle acceleration. Casey Reed \topurl{http://www.astronomy.com/asy/objects/images/207347main_whitedwarf_20080102_hi1.jpg} The Suzaku:
\topurl{ http://www.astronomy.com/asy/objects/images/207347main_suzaku_20080102_hi.jpg} New observations from Suzaku, a joint Japanese Aerospace Exploration Agency (JAXA) and NASA X-ray observatory, have challenged scientists’ conventional understanding of white dwarfs. Observers had believed white dwarfs were inert stellar corpses that slowly cool and fade away, but the new data tell a completely different story. At least one white dwarf, known as AE Aquarii, emits pulses of high-energy (hard) X-rays as it whirls around on its axis. “We’re seeing behavior like the pulsar in the Crab Nebula, but we’re seeing it in a white dwarf,” says Koji Mukai of NASA Goddard Space Flight Center in Greenbelt, Maryland. The Crab Nebula is the shattered remnant of a massive star that ended its life in a supernova explosion. “This is the first time such pulsar-like behavior has ever been observed in a white dwarf.” White dwarfs and pulsars represent distinct classes of compact objects that are born in the wake of stellar death. A white dwarf forms when a star similar in mass to the Sun runs out of nuclear fuel. As the outer layers puff off into space, the core gravitationally contracts into a sphere about the size of Earth, but with roughly the mass of the Sun. The white dwarf starts off scorching hot from the star’s residual heat. But with nothing to sustain nuclear reactions, it slowly cools over billions of years, eventually fading to near invisibility as a black dwarf. A pulsar is a type of neutron star, a collapsed core of an extremely massive star that exploded in a supernova. Whereas white dwarfs have incredibly high densities by earthly standards, neutron stars are even denser, cramming roughly 1.3 solar masses into a city-sized sphere. Pulsars give off radio and X-ray pulsations in lighthouse-like beams…….. |
