at Penn State
In collaboration with
Supernova remnants are the dramatic objects produced by the violent explosion of a massive star at the end of its life. This explosion, called a supernova, is one of the most energetic events in the universe, and causes a single star to briefly outshine the entire galaxy in which it is located. Supernovas in our own galaxy have produced spectacular light shows in the night (and often in the daytime) sky, but the last supernova in the Milky Way galaxy that was visible from Earth was in 1604. This is why the supernova discovered in the Large Magellanic Cloud (a nearby galaxy) in 1987 (called SN1987A) was so exciting to astronomers: it was the only supernova visible with the naked eye in the last 400 years!
Astronomers believe that supernovas occur in our galaxy roughly once every hundred years on average. Why are such infrequent events so interesting and important? The enormous amount of energy released in a supernova explosion has major effects on the interstellar medium (the gas between the stars). The explosion itself involves the core of the massive star, which is primarily composed of iron by the time it explodes. When the star is born, it is made of 90% hydrogen and 10% helium. The nuclear fusion that occurs in the center of the star combines hydrogen nuclei (protons) to form helium nuclei, releasing the energy that fuels the star during most of its life. Once the hydrogen in the core is exhausted, the helium is fused to form carbon, nitrogen, and oxygen, releasing more energy. This process continues, with the inner core of the star being converted to larger and larger nuclei, until finally the star is composed of an iron/nickel core surrounding by shells of silicon/sulpher, neon/magnesium, carbon/nitrogen/oxygen, helium, and hydrogen. The structure is like an onion. Once the inner core is converted to iron/nickel, no more energy is available from the fusion process and the inner core collapses catastrophically to form a neutron star or black hole. In the resulting explosion, the outer layers of the star are blown out into space with a velocity of up to 15,000 km/s (more than 30 million mph!).
There are two primary results. In the first place, this enormous explosion has a strong effect on the interstellar medium (ISM). It blasts a hole in the ISM that gradually expands until it reaches up to several hundred light years in diameter. This interior of this bubble in the ISM is extremely hot (typically several million degrees Celsius) but may only have one proton in every liter of volume. The interstellar medium is strongly disturbed by these supernova explosions, which are believed to have a strong effect on how gas is distributed in our galaxy. The shock waves from these explosions may also be responsible for collapsing interstellar clouds to form new stars, thus closing the cycle of stellar evolution.
Supernova remnants are also extremely important for distributing various elements through the interstellar medium. The Big Bang produced very little material besides hydrogen and helium, yet we know that most of our planet is composed of other elements. These other elements were produced inside stars and during supernova explosions, and were disbursed into the interstellar medium by supernova remnants. Eventually, the remnants cool and collapse to form interstellar clouds from which new stars and planets can be formed. (Click here for more information on how the elements are formed in stars and distributed through the galaxy by supernova explosions.)
The very tenous gas in the interior of the supernova remnant glows at X-ray wavelengths and can be observed by X-ray telescopes. (The gas around the edges of the remnant may produce optical and/or radio emission.) X-ray observations of supernova remnants have been a valuable source of information on the interactions between the explosion and the surrounding gas, and have been used to create our present understanding of the supernova explosion. At Penn State, we have been observing the X-rays from supernova remnants utilizing X-ray space telescopes on board ROSAT, Chandra, and XMM-Newton satellite observatories. We present highlights of our supernova remnant-science with some spectacular images.
|SNR 1987A: The remnant of supernova SN 1987A in the Large Magellanic Cloud. This is a very young supernova remnant, and gives us the first opportunity to observe the birth of a supernova remnant (Click on the image in the left for more details).|
|Cassiopeia A: Oxygen-rich Galactic supernova remnant(Click on the image in the left for more details).|
|G292+1.8: Oxygen-rich Galactic supernova remnant (Click on the image in the left for more details).|
|N103B: Type Ia supernova remnant in the Large Magellanic Cloud (Click on the image in the left for more details).|
|RCW 103: Galatic supernova remnant with a peculiar central compact object .|
|Sagittarius A East: Supernova remnant in the Galactic center (Click on the image in the left for more details).|
|N49: Supernova remnant in the Large Magellanic Cloud (Click on the image in the left for more details).|
|N49B: Supernova remnant in the Large Magellanic Cloud (Click on the image in the left for more details).|
|SNR 0103-72.6: New oxygen-rich supernova remnant in the Small Magellanic Cloud (Click on the image in the left for more details).|
|VRO 42.05.01 (G166.0+4.3): Galactic supernova remnant with peculiar morphology (Click on the image in the left for more details).||
|G63.7+1.1: Crab-like Galactic Supernova remnant.|
|SNR 0540-69.3: Oxygen-rich supernova remnant in the Large Magellanic Cloud.|
|G299.2-2.9: Galactic supernova remnant.|
|Orion-Eridanus superbubble: We have also studied X-ray emission from a related object, the very old superbubble known as the Orion-Eridanus superbubble. This is a large cavity in the interstellar medium created by stellar winds from the Orion OB1 association and possibly reheated by supernova explosions from this same association. This soft X-ray map was made by the ROSAT satellite (from Snowden et al. 1995, ApJ, 439, 399). Click here for more details.|
?NEED MORE SUPERNOVA REMNANTS?
of Galactic radio supernova remnants.
Chandra Supernova Remnant Catalog by Chandra X-ray Center.
Supernova Remnants Observed with Chandra - by the Penn State public outreach program.
MOST Supernova Remnant Catalogue (MSC)