This Hubble Space Telescope image shows Supernova 1987A within the Large Magellanic Cloud, a neighbo...

Science

35 years ago, a star exploded — now, the Webb Telescope could explain why

Astrophysicists hope to learn more about supernovas by analyzing the aftermaths of their explosions.

Credits: NASA, ESA, R. Kirshner (Harvard-Smithsonian Center for Astrophysics and Gordon and Betty Moore Foundation), and M. Mutchler and R. Avila (STScI)

The first supernova visible to the naked eye in more than 400 years was an explosion in 1987 that blazed with the power of 100 million suns for months.

Dubbed SN 1987A, it was the first supernova that modern astronomers could analyze in great detail, but the outburst faded over time. Now, astronomers endeavor to employ NASA's James Webb Space Telescope (JWST) to study the supernova's remnants and hopefully shed light on what happened after this star exploded—if its heart collapsed to either form a neutron star or a black hole.

HERE'S THE BACKGROUND — First discovered by witnesses in the Southern Hemisphere on February 23, 1987, SN 1987A exploded in the nearby Large Magellanic Cloud, a dwarf galaxy orbiting the Milky Way. Located roughly 167,000 light-years from Earth, SN 1987A was the nearest supernova seen in centuries, and it gave astronomers the best opportunity yet to examine the stages before, during, and after the death of a star.

The supernova's progenitor was a blue supergiant about 20 times the sun's mass named Sanduleak -69° 202. SN 1987A was a type II supernova, meaning the detonation happened after its star ran out of fuel and its core collapsed. Its remnants then would have rapidly imploded to form either a neutron star or a black hole.

Supernovas play critical roles in the evolution of galaxies, forging the heavier elements that help make up everything from people to planets. "Supernovae are one of the most energetic events in the universe," astronomer Mikako Matsuura at Cardiff University in Wales, lead investigator of the new proposal, tells Inverse. "Supernovae generate an enormous amount of energy, and supernova blast waves expand with enormous speed—typically one-third to one-30th light speed."

However, much remains uncertain about their extraordinarily complex inner workings. Astrophysicists often hope to learn more about them by analyzing the aftermaths of these explosions.

This Hubble Space Telescope image shows Supernova 1987A within the Large Magellanic Cloud, a neighboring galaxy to our Milky Way.Credits: NASA, ESA, R. Kirshner (Harvard-Smithsonian Center for Astrophysics and Gordon and Betty Moore Foundation), and M. Mutchler and R. Avila (STScI)

WHAT THE SCIENTISTS WANT TO DO — Since the supernova detonated, the fastest part of its blast wave has overtaken the explosions' circumstellar ring — the material SN 1987A's progenitor star expelled during its death throes about 20,000 years ago. Astronomers want to use the JWST to analyze the supernova's remnants and examine the area the blast wave hit beyond the circumstellar ring.

The supernova's blast wave, and turbulent shock waves it gives rise to as it encounters surrounding gas and dust, shattered dust grains into smaller fragments and heated them up. JWST can analyze how these giant waves are destroying this dust with unprecedented detail and in real-time.

"NASA's previous space mission, the Spitzer Space Telescope, barely resolved supernova SN 1987A; hence, we did not know how and where the blast waves impacted on dust grains," Matsuura says. "With very sharp images from JWST, we will be able to capture images of dust grains engulfed by blast waves."

JWST can also analyze hydrogen expelled from deep within the explosion. By analyzing this hydrogen's location and heat, the researchers can then see which models of the explosion best explain these stellar remains.

WHAT MIGHT THEY FIND? — "The most likely thing is that we'll see evidence for an energy source that's heating the dust," astronomer Robert Kirshner at Harvard University, proposal co-investigator, tells Inverse.

What might this energy source be? Just before scientists detected SN 1987A's light, they spotted a flash of neutrinos. "The particle process that forms neutrinos can also produce neutrons, so the explosion of SN 1987A should have left a neutron star," Matsuura says.

"For the past 35 years, we've been looking for that neutron star using the Hubble Space Telescope, the ALMA radio observatory, and other instruments," Kirshner says. "So far, the evidence is suggestive, but not conclusive. Part of the reason for that is that the shredded star has formed a lot of dust, so the path to the center is blocked from our direct view.

"But JWST is precisely the right tool for studying this problem," Kirshner continues. "Working at infrared wavelengths, it can see through the dust down toward the center of the explosion. Maybe we will see the signature of hot dust that is warmed by the neutron star."

Another possibility "is that material from the explosion has fallen back on the neutron star and pushed it over the brink to become a black hole," Kirshner adds. "How cool would it be to see evidence for that?"

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