SCIENCE

With a simple telescope and camera, a citizen scientist has helped professional astronomers witness the never-before-seen beginnings of a star’s explosive death. (Scientific American)

Learn more about supernova baby pictures with our Q&A resource.

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

Discussion Ideas

• New research describes the “shock breakout phase” of a supernova. What is a supernova? Take a look at our resource for some help.
  • A supernova is the sudden, bright explosion of a massive star, at least eight times more massive than the Sun.
    • Supernovae 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 briefly re-ignites in its core, and this runaway nuclear reaction causes the white dwarf to explode.
      • A type II supernova describes an explosion that ends the life of a single, massive star—although this star may be part of a binary star system. There are many variants of type II supernovae. SN 2016gkg is probably type IIb. Consult the illustration above as a reference.
        • 1. Type IIb supernovae are products of binary star systems in which the stars have very different life cycles.
        • 2. The more massive star bloats to a giant phase, expanding as it burns a shell of hydrogen around its mostly-helium core. The giant star spills this envelope of hydrogen to its companion star.
        • 3. Eventually, the giant star goes supernova. It 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.
        • 4. The supernova results in one of three types of stellar remnants: a white dwarf, a neutron star, or a black hole. The less-massive companion survives—larger and hotter due to the hydrogen it picked up from its exploded sister.
        • Right now, SN 2016gkg is shrouded by a bright nebula from the explosion. (Number 3 in the illustration.) Scientists are waiting for the nebula to cool down and fade, which will allow them to observe any stellar remnant—likely a neutron star—and companion star.)
  • SN 2016gkg lies at the edge of NGC 613, a beautiful barred spiral galaxy (just like our own Milky Way) about 26 million parsecs (85 million light-years) from Earth.
  • Astronomers think SN 2016gkg’s progenitor star was a yellow supergiant about 20 times as massive as the sun.

• Are supernovae rare?
  • No. Fifty stars are thought to explode every second in the universe, but most are too distant to be seen from Earth, too obscured by interstellar dust, or too bright and blobby for telescopes to focus on.

• Why are amateur astronomers “uniquely suited” to capture supernovae?
  • more narrow focus. “Their telescopes and imaging equipment are more attuned to brighter objects, and they tend to focus on just a few targets over the course of a night rather than a large-observatory survey that monitors the entire night sky.”
  • range of observations. “Some amateur astronomers might use only the optical wavelengths human eyes can see whereas others may try to see it in other frequencies such as infrared. Still some set up their own spectrometers—sensors that measure chemicals traces given off by a star or other object.
  • standouts. “‘They don’t discover as many [supernovae] as the professional surveys,’ says one astronomer. ‘But usually when they discover something, it’s way more important than what we discover.’”

• What is a supernova’s “shock breakout” phase?
  • A “shock breakout” describes the behavior of a star just before it goes supernova. During this phase, a “wave of energy [a shock] rolls from a star’s core to its exterior just before the star explodes. Computer models had suggested the existence of this phase, but [before Buso photographed it] no one had witnessed it.”
  • Astronomers think Buso’s homemade observatory—Observatorio Busoiano—captured light from the supernova’s first hour. Astronomers had previously seen a supernova around 3 hours after the shockwave reached the surface.

• How might the baby pictures of SN 2016gkg help astronomers better understand supernovae?
  • “In our field,” says one astronomer, “this is a fundamental question: What is the structure of the star at the moment of explosion?”
    • With Buso’s observations, scientists can begin to answer that.
      • more monitoring. “The prompt discovery and announcement of SN 2016gkg triggered extensive monitoring that began less than one day later, including X-ray, ultraviolet and optical observations.”
      • before and after. Scientists were able to compare observations of SN 2016gkg with images of the same area of sky taken with the Hubble Space Telescope years before, allowing them to tentatively identify a progenitor star. Further study “could potentially provide important information about the outermost progenitor structure and the physical processes that occur during the emergence of the shock.”
      • evolutionary phases. “By combining with theory and sophisticated computer modeling, [astronomers were] able to distinguish between different phases in the evolution of the supernova, each of which is regulated by different physical processes.”

TEACHERS TOOLKIT

Scientific American: A Star Is Shorn: The Fine Art of Spotting Supernovae Is Ideal for Amateurs

Cosmos: Caught on camera: the birth of a supernova

Nature: Amateur astronomer catches first glimpses of birth of a supernova

Nat Geo: Supernova Baby Pictures

(extra credit!) Nature: A surge of light at the birth of a supernova