Astro Bob – 2/8 – Supernova 2014J in M82: What’s left after the party’s over?

Supernova 2014J in M82: What’s left after the party’s over?


Supernova 2014J in M82, the Cigar Galaxy, appears to have peaked in late Jan.-early Feb. at around magnitude 10.5. It’s now slowly beginning to fade. This photo taken Jan. 31 near peak. Credit: Joseph Brimacombe

Even with the moon filling out and lighting up the sky this week, supernova 2014J remains an easy catch in 4-inch and larger telescopes. One advantage of all the bitter cold weather in the U.S. Midwest has been a succession of clear nights like we haven’t seen in months. Maybe years.

Like many, I’ve had lots of opportunities to get out and see the progress of the star since its discovery on Jan. 21. Last night it still glowed at magnitude 10.9, a slight decline in brightness since peaking early this month at about 10.5.

M82 is also called the Starburst Galaxy. Vigorous new star formation blasts fiery-looking plumes of glowing hydrogen out of its central regions. Click to enlarge. Credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA)

Color photos show the supernova tinted orange, reddened by dust clouds within the galaxy. This reddening is no surprise given how dusty the Cigar Galaxy is. M82 produces far more new stars than the Milky Way, the reason it’s also known as the Starburst Galaxy.

Powerful stellar winds from so many new stars sweeps dust and gas from the core and sends it flying across the galaxy. Later, even more dust is released when older generations of stars evolve, expand (or explode as supernova) and leave behind ice and silicate ash that filters and reddens the light of the supernova.

Curves showing how the supernova in M82 started out faint (left), and peaked at the beginning of this month. Notice how much fainter 2014J is in blue light compared to red. Visual observations are shown in green. Credit: AAVSO

You can see the dramatic effects of reddening in the light curves created by the American Association of Variable Star Observers (AAVSO) based on observations compiled by amateur astronomers. In blue light (lower curve) 2014J peaked at magnitude 11.6, but in red light (top) it was nearly two magnitudes brighter.

Had the supernova erupted in a less dusty part of the galaxy, it’s estimated that it would have peaked closer to magnitude 9, putting it within reach of 50mm binoculars!

Dust is likely behind the difficulty in finding the pre-explosion progenitor star and its companion. Professional astronomers have dug through archival pictures and data from the Chandra X-ray and Hubble Space telescopes as far back as 1999 but nothing’s turned up yet.

The progenitor and evolution of a Type Ia supernova. Credit: NASA, ESA, and A. Field (STScI)

Unlike a Type II supernova explosion of a supergiant star, 2014J involved the cataclysmic destruction of a planet-sized white dwarf star in close orbit around a red giant star. Material siphoned off the companion built up on the dwarf’s surface until it reached critical mass and self-destructed in a supernova explosion. Astronomers call this a Type Ia blast.

Clouds of dust are silhouetted against the young star cluster IC 2944 in the Milky Way galaxy. Similar clusters and dust clouds litter M82. Credit: ESO

White dwarfs and their companions are small and faint compared to a supergiant progenitor, making the search that much more difficult. Based on deep (long-time exposure) archival images taken with the Hubble Space Telescope and the galaxy’s distance of about 12 million light years, a team of astronomers recently proposed that the dwarf’s companion is a subgiant, a star larger, brighter and further evolved than the sun but not yet in the red giant stage. Procyon in the constellation Canis Minor is a good example of a subgiant.

Subgiants can be more or less massive. If more massive, they evolve into helium stars with powerful winds and rapid mass loss, making them worthy competitors in an intergalactic version of TV’s “The Biggest Loser”.

Another view of the supernova in the dusty galaxy M82 taken on Jan. 29 near Trieste, Italy with an 8-inch telescope. Credit: Giorgio Rizzarelli

If less massive, the remnant would develop into a helium white dwarf. Astronomers will be studying the explosion site for a long time looking for clues of what’s been left behind. Like detectives in a murder case, they hope to reconstruct the scene of this catalclysmic crime.

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By olinstarwalker

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