Overview of Chandra

Here you will find some of the astounding discoveries about celestial objects that have been made with the images that the Chandra X-ray observatory has taken.

Composite Chandra X-ray and Optical Image of the Massive Star HD 192163 (10.14.03)

The Chandra X-ray telescope recently produced an image (shown at left) that, when composited with the optical image of the same star, created a beautiful picture that revealed a lot about a shell of gas in the Crescent Nebula that was created by winds from the massive star HD 192163. This star is about one-thousandth the age of the sun, and after roughly 4.5 million years, it began its pathway to supernova explosion.

The first step in its self-destruction was an enormous expansion to the red giant stage, ejecting its outer layers at speeds up to 20,000 miles per hour. Two thousand years later, the radiation from the now explosed inner part of the star began pushing the gas away from the fringes of the star at speeds up to and above three million miles per hour. This stellar wind soon collided with the winds from the red giant, forming a dense shell and two shock waves, one that moved outward from the shell, creating the green filamentary bodies (shown above), the other moving inward, producing gas at a temperature of one million degrees. That is shown above in blue. As mentioned, this is a composite image from both optical and x-ray telescopes. The green in the above picture is from the optical telescope, and the blue is the image from the x-ray telescope: as we know, x-ray telescopes can detect very high temperatures, which is what the blue, inward moving shell shows.

We can see that without the x-ray image combining with the optical image, this portion of the Crescent Nebula remains very confusing: it is only a mess of green streaks -- the outward moving shell. When combined with the X-ray image that shows the entire explosion, astronomers were able to determine the actual death situation of the massive star HD 192163, whose supernova explosion will occur in about 100,000 years. This image also helped astronomers determine the mass, energy, and composition of that gaseous shell, granting them greater insight into the realm of pre-supernova stars.

Source: http://www1.msfc.nasa.gov/NEWSROOM/news/photos/2003/photos03-184.html

Chandra Discovers the Violent Nature of the NGC 1637 Spiral Galaxy (10.28.03)

The Chandra X-ray observatory just completed an observation that took place over 21 months of the NGC 1637 spiral galaxy, an object that seemed to be calm when viewed through optical telescopes, but is now shown to be very violent and restless by the new X-ray images. During the 21-month observation, neutron star and black hole X-ray sources flashed in and out.

This volatile behavior is not unusual for neutron stars and black holes that orbit regular companion stars, because the gas pulled by the intense gravitational fields of the black holes and neutron stars are compressed and heated, creating powerful X-radiation which often only lasts for a few seconds. Obviously, the X-ray telescopes can observe this, showing this violent action, and the optical telescopes cannot, because the intense temperatures of the radiation flares are too high for their means of detection.  The usual observation of NGC 1637 is about fifty billion stars in a spiral formation, and about once every 100 years a supernova, indicating the death of a star, interrupts this peaceful scene, perhaps forming a neutron star or a black hole. One of these detections triggered the new Chandra observations in 1999, shortly after Chandra was launched. It appears in the observation research on days 4 and 49 of the study, but faded in a few months. However, observation continued in concert with the Hubble Space telescope and the Very Large Array radio telescope, granting a useful compilation of optical, radio, and x-ray data for the galaxy.

Source: http://www1.msfc.nasa.gov/NEWSROOM/news/photos/2003/photos03-192.html

Chandra X-Ray Images Offer Insight to Eta Carina Nebula (10.8.99)

The Eta Carina nebula was  popularized by a Hubble Space Telescope image that showed a star in it blowing off material in a supernova-like explosion. However, when the Chandra X-Ray observatory took its own pictures of the same nebula, the truth came out: it was not a supernova. The pictures above show (at left) the picture taken by the Chandra telescope and (at right) the original Hubble image and where it fits into the new Chandra image (it is the large blue body).

The X-ray image was expected to show a strong central source with a small diffusion cloud around it from the emissions of gas from the explosion. Instead, it shows three distinct structures: an outer, horseshoe-like ring that is about two light-years in diameter, a hot inner core about three light-months in diameter, and a hot, central core that is less than one light-month in diameter, possibly containing the superstar itself. The horseshoe outer ring points to another large explosion that took place more than a thousand years ago.

The Chandra image raised questions for astronomers about how a star could produce such hot and intense X-rays, because X-rays are typically believed to be made by colliding gas streams from two close stars (as in the case of HD 192163, above). The core shown in the image countered this assumption, calling for new theory.

One theory identifies Eta Carinae as something that is driven by a star so massive, it is 150 times bigger than the Sun. This huge star would create so much intense radiation that it would cause violent instabilities before the supernova explosion (as in the case of NGC 1637, above). The outer rings are the remainder of an eruption dating back at least 200 years.

A second theory about Eta Carinae calls it a death star, acting as a massive ultraviolet laser. Certain Hubble observations (from 1996) can be used to show that this theory is the most plausible of them all. Natural lasers, created when atoms or molecules in any medium combine into the same wavelength, have been observed previously, such as in masers, the microwave version of a laser. Natural infrared lasers are very rare in space, however, and if this laser really existed, would be the first of its kind observed.

Source: http://science.nasa.gov/newhome/headlines/ast08oct99_1.htm