Thursday, June 9, 2011

Supernova Remnant 1987A Brightens

Located in the Large Magellanic Cloud in the outskirts of the Tarantula Nebula, SN (Supernova) 1987A sits approximately 168,000 light-years away and became the closest known supernova since SN 1604. SN 1604 was about 20,000 light years away and burst in April 2011, needless to say it was discovered in 1604 by Johannes Kepler. February 23, 1987 was that famous day in which light from this supernova (SN 1978A; most supernova take names in what year they were discovered) was observed and provided great insight for astronomers: no supernova had ever been this close to earth in 400 years.

Supernova 1978A, Circumstellar rings visible in the small upper-right corner.
The supernova debris, which had faded over may years, had started to brighten June 9. If the supernova was dimming, then another light-source had to be lightening the debris. This marked SN 1987 from a supernova to a supernova remnant, like the beautiful Crab nebula.  Robert Kirshner, of the Harvard-Smithsonian Center for Astrophysics, comments: "Supernova 1987A has become the youngest supernova remnant visible to us." Kirshner leads a long-term study of this now supernova remnant with NASA's Hubble; since 1990, Hubble has provided a perpetual record of data that has helped greatly. The ejecta (debris shot out of the supernova) has been expanding, but fading. Now, the supernova is brightening, and a team of astronomers explain the ejecta and make known the Hubble's help from a paper entitled X-raying the Ejecta of Supernova 1987A.
Since the explosion, the ejecta have been expanding, and now the outer parts of the ejecta are colliding with the ring...The dense, central part of the ejecta contains most of the mass from the disrupted star and acts as a calorimeter for the energy input to the SN. Here we determine the energy input by tracking the energy output with the Hubble Space Telescope (HST).
In the image below, the ring of material is the ejecta; it blew of a great deal of years before it exploded. The ring you see pictured is actually approximately one light-year (six trillion miles) across. Inside the ring comes the 'insides' of the star, making the supernova ejecta shoot out farther. Radioactive elements are making the ejecta shine brighter, resulting the fading over time. But, rather than fading, it's brightening, suggesting the fact that something new is making it shine. "It's only possible to see this brightening because SN 1987A is so close and Hubble has such sharp vision," Kirshner said.

Supernova Remnants usually look like a 'bubble,' like Tycho's Supernova (viewed below) and consist of materials ejected from an exploding star. The debris will generally impact a surrounding ring and create a powerful shock that will generate X-rays. "We show that this increase is the result of heat deposited by X-rays produced as the ejecta interacts with the surrounding material," rests at the bottom of the abstract in the paper mentioned earlier. "We believe that the strong X-ray flux produced in the ring collision is the dominant source of energy input to the ejecta," they continue to say farther down in the paper. The X-rays mentioned are illuminating the debris and 'shock-heating' it, making it glow; just like other supernova remnants in our galaxy and others.

On account of the age of this remnant, the history of the star's last years may be decoded to find more information about Supernovae and remnants. "Young supernova remnants have personality," Kirshner agreed!

Tycho's Supernova; note the 'bubble' form

"Eventually, that history will be lost when the bulk of the expanding stellar debris hits the surrounding ring and shreds it," warns ScienceDaily to encourage those to view it now. It's not every day that you'll get to see a young supernova remnant! X-raying the Ejecta of Supernova 1987A, tells us the future of SN 1987A, with these last remarks.
In the future the density of the ejecta will decrease and the fraction of X-rays absorbed will grow...As a result the ionization will increase and a smaller fraction of the X-ray flux will produce line excitation, while a larger fraction will go into heating, leading to an increase in the mid-IR flux and a flattening of the optical light curves. With time the X-rays will also penetrate deeper layers of the ejecta, thereby allowing us to probe the chemical structure of the innermost ejecta. This will be a novel form of X-ray tomography.

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    NEWS 09-12-11 from NASA