Hubble Revisits Supernova 1987A

It's been more than two decades since we Earthlings got word that a star in the Large Magellanic Cloud had blown itself to smithereens.

Supernova 1987A
The supernova that was spotted in the Large Magellanic Cloud in 1987 reached 3rd magnitude and was the brightest to grace our skies in 383 years.
Courtesy David Malin, Ray Sharples, and the Anglo-Australian Observatory.
Supernova 1987A peaked at 3rd magnitude, making it a snap to spot by eye. But, with its declination of -69°, the blast was invisible to virtually everyone north of the equator. I'm jealous of my southern astro-friends because I never got to see it. (In fact, I wonder how the popular perception of and appreciation for astronomy might be different had this event been in view from northern skies — a topic for another day!)

Fortunately, the Hubble Space Telescope started observing SN 1987A within months of its launch in 1990. Those first views revealed a ring of matter thrown out by the star about 20,000 years before its demise. The supernova's expanding shock wave eventually crashed into that ring, creating a necklace of bright knots first spotted in 1995 HST images. Observers have kept tabs on this ring ever since — primarily with an instrument called the Space Telescope Imaging Spectrograph, or STIS, which astronauts installed on Hubble in 1997.

Unfortunately, an electronic failure in 2004 rendered STIS inoperable, and astronomers had to make do without its services until last year, when spacewalking astronauts replaced a faulty circuit board and brought STIS back to life.

Supernova 1987A
Supernova 1987A's ring, about a light-year across, was probably shed by the star about 20,000 years before it exploded. The dozens of bright spots around the ring mark where a shock wave unleashed by the stellar blast is slamming into the ring's material.
NASA / ESA / K. France / P. Challis / R. Kirshner
In the September 2nd edition of Science Express, a star-studded international team of astronomers describe observations of the supernova made with STIS earlier this year, the first in six years. The ejected ring is still there, now studded with about 30 hotspots. Over time, as the supernova's shock wave continues to barrel outward, these should merge into a single bright band.

More interesting is the insight being gleaned from a second shock wave, this one triggered by the ring itself and propagating back toward what's left of the progenitor star and through the supernova's expanding debris. The team reports that spectra of this inner shock reveal lots of hydrogen, as you'd expect, but they also see some other emissions that are probably from nitrogen and perhaps from carbon.

Essentially, the now-gone star has laid bare whatever was inside when it exploded, and over time careful observations by HST and other telescopes will, in Humpty Dumpty fashion, attempt to put the progenitor star back together again.

"I think a great thing here is the resurrection of STIS," notes coauthor Robert Kirshner (Harvard-Smithsonian Center for Astrophysics). "Astronauts zipping out 114 screws while wearing boxing gloves were not just doing it for the challenge! This paper shows that the instrument is back working, and that we're finding out new things about an object that is about the same age as HST."

Read more about the new findings in this University of Colorado press release.

10 thoughts on “Hubble Revisits Supernova 1987A

  1. George-EbertsGeorge Eberts

    If you wonder how much popular perception & appreciation of astronomy might have been boosted by a third magnitude object, consider the impact on the popular psychology & media if Comet McNaught had been visible from the U.S., Europe, and Japan! The millenium/2012/etc. types are always ready to pounce on astronomical images & sights.

  2. KPW

    Someone should study the “popular perception of and appreciation for astronomy” in places like Australia, South Africa, and Argentina, and how they are different now from the way they were before SN 1987A. In places with dark skies there might be little difference; people might have been generally aware of the sky, seasonal changes, astronomy, and so forth. Or all of that except astronomy, since the rest was always part of their culture. The differences between perceptions in the different cultures before, and the changes after, would make a complex and interesting study.

    I would love to see the results of that study (if anyone does it).

  3. Serena

    I would like some more analysis of the image shown above. Which features are artefacts and from where do they arise? The adjacent stars also are surrounded by similar “glowing dots” and there are two much larger faint rings of dots.

  4. Athos

    We lived intensely that event. First, it was discovered in La Silla, Chile. I took my family to Atacama desert and observed the SN 1987A with anaided eyes. We didn’t have any instrument but enjoyed the moments.
    The general press did a lot of noise, but this theme wasn’t of common interest.
    The impact of great astronomy events in the population are dependent of: 1.-How the press put it. 2.-General knowledgement of astronomy, which is scarce.

  5. athos

    There are not artifacts in this picture. The 2 brilliant stars are really nearer to us than SN. The 2 dim rings visible as making a frame to SN 1987A and its pearls’ necklace, are really matter thrown by the star before exploding. The reasons they formed are no yet clear.

  6. Chuck

    I agree with Serena – there are definitely refraction artifacts in the photo. The resolved disks of the two “nearer” stars are surrounded by 12 (four quadrants of three) 1/4 sized images of themselves. That pattern is surrounded by a starburst spectrum in several concentric and overlapping rings. The reddish star in the 4 o’clock position seems to have a similar though fainter refractive artifact and is doubly confusing in that it is aligned on one of the rings of ejecta. That recognized, this is an incredible image. Thank “heaven” and the astronauts for such an opportunity in our lifetime.

  7. Anthony BarreiroAnthony Barreiro

    Fascinating story, thanks. I’m curious — *before* the supernova exploded, would the previously ejected ring of matter have appeared as a planetary nebula?

  8. Snowball Solar System

    Is there any indication that the “necklace of bright knots” is similar to ‘cometary knots’ (CKs) in planetary nebulae, such as the Helix nebula? Could these bright knots have planetary mass that may cool to form dense (10^6 molecules/cm3) neutral CKs in time, or instead are they generally viewed, as you seem to indicate, as transitory objects that will most likely merge to form a continuous bright band?

    Finally, is anyone in the scientific community equating them with CKs from planetary nebulae?

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