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The Milky Way's most recent supernova was hidden... until now! (Synopsis)

By esiegel on March 30, 2016.

“When a star goes supernova, the explosion emits enough light to overshadow an entire solar system, even a galaxy. Such explosions can set off the creation of new stars. In its own way, it was not unlike being born.” -Todd Nelson

In 1604, Kepler's supernova went off, the last Milky Way supernova visible to naked-eye skywatchers here on Earth. Yet since the development of radio and X-ray astronomy, other, more recent supernova remnants in our galaxy have been found. They've only been invisible to the naked eye because of the galactic gas and dust that blocks their visible light. In 1984/5, the VLA discovered the most recent known remnant near the galactic center, and follow-up observations showed a rapid expansion.

Images credit: X-ray (NASA/CXC/NCSU/S.Reynolds et al.); Radio (NSF/NRAO/VLA/Cambridge/D.Green et al.); Infrared (2MASS/UMass/IPAC-Caltech/NASA/NSF/CfA/E.Bressert), of the supernova remnant in 1985 (L) and 2007/8 (R). Images credit: X-ray (NASA/CXC/NCSU/S.Reynolds et al.); Radio (NSF/NRAO/VLA/Cambridge/D.Green et al.); Infrared (2MASS/UMass/IPAC-Caltech/NASA/NSF/CfA/E.Bressert), of the supernova remnant in 1985 (L) and 2007/8 (R).

The most recent data not only dates this remnant to be only 110 years old, but it teaches us that it's a Type Ia supernova that formed from the merger of two white dwarfs. The standard model — of one white dwarf accruing matter from a binary companion — may not only be a minority of Type Ia events, perhaps it doesn't occur at all.

Ethan SiegelEthan Siegel, Contributor Image credit: NASA/CXC/CfA/S. Chakraborti et al., of supernova remnant G1.9+0.3. Image credit: NASA/CXC/CfA/S. Chakraborti et al., of supernova remnant G1.9+0.3. The brightest, most spectacular explosions in the Universe — supernovae — occur under two very special circumstances. One is when an ultra-massive star some 20, 50 or even 100 or more times the mass of our Sun, runs out of nuclear fuel in its core and reaches the end of its life. The inner core implodes, the outer layers undergo a runaway chain reaction of nuclear fusion, and the majority of the star blows up in a nuclear inferno: a Type II supernova. The other is when a white dwarf (or two merging white dwarfs) reach a large enough overall mass that they collapse, igniting a runaway fusion reaction that destroys the entire star: a Type Ia supernova. Yet despite other galaxies showing supernovae a few times per century, on average, no human on Earth has seen one in our Milky Way since 1604. Image credit: NASA/ESA/JHU/R.Sankrit & W.Blair, of an optical/IR/X-ray composite of the 1604 supernova remnant. Image credit: NASA/ESA/JHU/R.Sankrit & W.Blair, of an optical/IR/X-ray composite of the 1604 supernova remnant. But Kepler’s supernova wasn’t the last one at all, it was only the last one visible to the naked eyes of humanity. Being trapped within our Milky Way might mean we’re closer to any supernovae that happen than in any other galaxy, but it also means we’ve got more light-blocking dust to deal with as we attempt to observe them. Above is a supernova remnant within our own galaxy: Cassiopeia A, which occurred in 1680, but was only discovered centuries later with the development of radio astronomy. ADVERTISING inRead invented by Teads Image credit: NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration. Acknowledgement: Robert A. Fesen (Dartmouth College, USA) and James Long (ESA/Hubble), of the Cassiopeia A supernova remnant as imaged by Hubble. Image credit: NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration. Acknowledgement: Robert A. Fesen (Dartmouth College, USA) and James Long (ESA/Hubble), of the Cassiopeia A supernova remnant as imaged by Hubble. Black holes and neutron stars, the remnants of Type II supernovae, emit so strongly in the radio that Cassiopeia A is the strongest radio source as seen from Earth beyond our own Solar System. Despite the fact that it was invisible from Earth, Cassiopeia A is only 9,000 light years away: firmly in our neighborhood of the 100,000 light year diameter Milky Way. Yet below, towards the galactic center, an even newer supernova remnant was discovered in 1984/5. Recommended by Forbes OracleVoice: Finance: Your Company's Customer Satisfaction Secret Weapon MOST POPULAR Photos: Donald Trump Through The Years JPMorgan ChaseVoice: What Do Financial Volatility And Resiliency Have In Common? TRENDING ON LINKEDIN How To Tell Stories Like TED Speakers MOST POPULAR Photos: Top College In Every State Image credit: NASA/CXC/NCSU/K.Borkowski et al., of supernova remnant G1.9+0.3 as imaged by Chandra in 2013. Image credit: NASA/CXC/NCSU/K.Borkowski et al., of supernova remnant G1.9+0.3 as imaged by Chandra in 2013. Image credit: NASA/CXC/NCSU/K.Borkowski et al., of supernova remnant G1.9+0.3 as imaged by Chandra in 2013.

Go get the full story of this new observation of G1.9+0.3 over on Forbes!

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Astronomy
Supernovae

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For some reason I didn't realize the star Kepler caught going supernova wasn't in the Milky Way. I did not know our resolving power now allowed us to look that closely at individual stars in other galaxies.

Looks like you have officially learned something coming to this site.
:)

Type IA supernovae are used as standard candles. This works if they occur by accretion of mass by a white dwarf until is reaches the Chandrasekar Limit. But if I'm not missing something if they form predominantly from mergers of white dwarfs the mass involved and the amount of energy released is much less constant, and they wouldn't work as standard candles. What implications would this have for the astronomical distance scale?