'Wonderful' star reveals its hot nature

Apr 28, 2005
'Wonderful' star reveals its hot nature

For the first time an X-ray image of a pair of interacting stars has been made by NASA's Chandra X-ray Observatory.
The ability to distinguish between the interacting stars – one a highly evolved giant star and the other likely a white dwarf – allowed a team of scientists to observe an X-ray outburst from the giant star and find evidence that a bridge of hot matter is streaming between the two stars.

Image: The Chandra image shows Mira A (right), a highly evolved red giant star, and Mira B (left), a white dwarf.

"Before this observation it was assumed that all the X-rays came from a hot disk surrounding a white dwarf, so the detection of an X-ray outburst from the giant star came as a surprise," said Margarita Karovska of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., and lead author article in the latest Astrophysical Journal Letters describing this work. An ultraviolet image made by the Hubble Space Telescope was a key to identifying the location of the X-ray outburst with the giant star.

X-ray studies of this system, called Mira AB, may also provide better understanding of interactions between other binary systems consisting of a "normal" star and a collapsed star such as a white dwarf, black hole or a neutron star, where the individual stellar objects and gas flow cannot be distinguished in an image.

The separation of the X-rays from the giant star and the white dwarf was made possible by the superb angular resolution of Chandra, and the relative proximity of the star system at about 420 light years from Earth. The stars in Mira AB are about 6.5 billion miles apart, or almost twice the distance of Pluto from the Sun.

Mira A (Mira) was named "The Wonderful" star in the 17th century because its brightness was observed to wax and wane over a period of about 330 days. Because it is in the advanced, red giant phase of a star's life, it has swollen to about 600 times that of the Sun and it is pulsating. Mira A is now approaching the stage where its nuclear fuel supply will be exhausted, and it will collapse to become a white dwarf.

The internal turmoil in Mira A could create magnetic disturbances in the upper atmosphere of the star and lead to the observed X-ray outbursts, as well as the rapid loss of material from the star in a blustery, strong, stellar wind. Some of the gas and dust escaping from Mira A is captured by its companion Mira B.

In stark contrast to Mira A, Mira B is thought to be a white dwarf star about the size of the Earth. Some of the material in the wind from Mira A is captured in an accretion disk around Mira B, where collisions between rapidly moving particles produce X-rays.

One of the more intriguing aspects of the observations of Mira AB at both X-ray and ultraviolet wavelengths is the evidence for a faint bridge of material joining the two stars. The existence of a bridge would indicate that, in addition to capturing material from the stellar wind, Mira B is also pulling material directly off Mira A into the accretion disk.

Chandra observed Mira with its Advanced CCD Imaging Spectrometer on December 6, 2003 for about 19 hours. NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate, Washington. Northrop Grumman of Redondo Beach, Calif., was the prime development contractor for the observatory. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass.

Source: Chandra X-ray Center

Explore further: Heavy metal frost? A new look at a Venusian mystery

add to favorites email to friend print save as pdf

Related Stories

Recommended for you

New radio telescope ready to probe

50 minutes ago

Whirring back and forth on a turning turret, the white, 40-foot dish evokes the aura of movies such as "Golden Eye" or "Contact," but the University of Arizona team of scientists and engineers that commissioned ...

Image: Comet 67P/Churyumov–Gerasimenko

55 minutes ago

It was 45 years ago when astronomer Klim Churyumov and Svetlana Gerasimenko, one of his researchers, unwittingly began a new chapter in the history of space exploration.

Extreme ultraviolet image of a significant solar flare

1 hour ago

The sun emitted a significant solar flare on Oct. 19, 2014, peaking at 1:01 a.m. EDT. NASA's Solar Dynamics Observatory, which is always observing the sun, captured this image of the event in extreme ultraviolet ...

Heavy metal frost? A new look at a Venusian mystery

20 hours ago

Venus is hiding something beneath its brilliant shroud of clouds: a first order mystery about the planet that researchers may be a little closer to solving because of a new re-analysis of twenty-year-old ...

Exomoons Could Be Abundant Sources Of Habitability

23 hours ago

With about 4,000 planet candidates from the Kepler Space Telescope data to analyze so far, astronomers are busy trying to figure out questions about habitability. What size planet could host life? How far ...

User comments : 0