SCIENCE

New observations represent the most complete image of a supernova’s immediate aftermath.  (Washington Post and Ars Technica)

Learn a little about supernovas with our introductory resource.

Teachers, scroll down for a quick list of key resources in our Teachers Toolkit.

Discussion Ideas

• New research details the immediate aftermath of a supernova. What is a supernova?
  • A supernova is the sudden, bright explosion of a massive star. (We mean massive: The star that researchers just witnessed going supernova was 10 times more massive than the sun.) Supernovas are usually divided into two major categories.
    • A type I supernova describes an explosion in a binary star system in which at least one of the stars is a white dwarf, a small star nearing the end of its life cycle. The white dwarf accumulates matter from its companion star until nuclear fusion is briefly re-ignited in its core, and this runaway nuclear reaction causes the white dwarf to explode. These types of supernovas are sometimes called thermal or thermonuclear supernovas.
    • A type II supernova describes an explosion that ends the life of a single, massive star. The candidate for this type of supernova is a red supergiant, the largest type of star in the universe in terms of volume. Red supergiants have exhausted the supply of hydrogen in their cores, and expanded as they burn a shell of hydrogen around its mostly-helium core. (Really expanded: A red supergiant could engulf our solar system past the orbit of Mars.) Eventually, the red supergiant starts to run out of helium and begins to fuse heavier elements, including carbon, neon, oxygen, silicon, and iron. These heavier elements require higher rates of fusion to counteract gravity. But, nothing can escape gravity and ultimately the core becomes so massive it collapses on itself before violently exploding. The initial gravitational collapse results in one of three types of stellar remnants: a white dwarf, a neutron star, or a black hole.

• What type of supernova was SN2013fs, the supernova described in the article?
  • Supernova 2013fs was a type II, the explosion of a single red supergiant in the galaxy NGC7610, in the constellation Pegasus.
    • Specifically, the explosion was a type II-P, which is defined by a slow decline in luminosity.

• The new research seems to focus on the circumstellar material (CSM) of SN2013fs. What is CSM? Take a look at the image up top for some help.
  • Circumstellar material describes the shell of gas expelled by the collapsing star. Unlike the gases of the star itself, CSM is not gravitationally bound to the star’s core. (This is the result of the star in its death throes furiously counteracting gravity.)
    • The star that became SN2013fs was ejecting gases at a rate of about .1 solar masses a year. The star’s CSM stretched about six light-hours, about the Sun-Pluto distance.
    • The star’s CSM was illuminated by light from the supernova before being destroyed by it. “In the past, it’s been difficult to study the CSM, because it gets swept away by ejecta (stellar shrapnel) once the star blows up. But the spectra taken by Yaron, Perley and their colleagues captured this gas shell before it vanished.”

• Supernova 2013f’s CSM showed a big spike in heavily ionized oxygen atoms, which then completely disappeared. How do astrophysicists explain this weird behavior? (This is our favorite part!)
  • The supernova blasted through there and ripped the electrons right off those oxygen atoms … then it obliterated them.
  • “The authors explain this behavior by positing that the red supergiant ejected a significant amount of material before it exploded. The light from the explosion then swept through the vicinity, eventually catching up with the material and stripping the electrons off its atoms. The sudden cutoff came when the light exited out the far side of the material, allowing it to return to a lower energy state, where it stayed until the physical debris of the explosion slammed into it about five days later.”

• Supernovas have been observed before. What makes the observations of SN2013fs a “remarkable achievement”?
  • These are the world’s first supernova “baby pictures.” (And no, they don’t look like “pictures” to non-astrophysicists.) “Young supernovae are hard to come by: without the knowledge of when and where they are going to explode, we tend to chance upon them when they are already several days old. By this time, the supernova ejecta have already swept through a large volume, destroying any information about its immediate environment,” says one astronomer.
    • Keep in mind, the supernova isn’t really a baby at this point—these baby pictures took 160 million years to reach Earth. Although really keep in mind, that’s the blink fo an astronomical eye and that region of space probably hasn’t changed too much.

• How is the discovery and documentation of SN2013fs a terrific example of the international effort of science?
  • The astronomical anomaly was first spotted by a program using the Palomar Observatory near San Diego, California. The program then sent the anomaly’s location to the Weizmann Institute of Science in Rehovot, Israel. The scientists in Israel sent a message to a researcher in Copenhagen, Denmark, who secured time at the Keck Observatory in Hawaii. Finally, “[o]ver the next days and months, colleagues running telescopes in Spain, Australia and elsewhere conducted follow-up observations to collect more data.”

TEACHERS TOOLKIT

Washington Post: The spectacular aftermath of a supernova was just seen at its earliest stage ever

Ars Technica: Observations catch a supernova three hours after it exploded

Nat Geo: Supernova 1054

NASA: What Is a Supernova?

(extra credit!) Nature Physics: Confined dense circumstellar material surrounding a regular type II supernova