Saturday science subject: Our galaxy's youngest supernova

What does a star look like right after blowing up? Something a little like this. As Nature reports, NASA has discovered the youngest supernova yet in our galaxy. In this case, "young" is relative—the supernova is actually 140 years old. Nonetheless, Stephen Reynolds from North Carolina State University says the discovery will allow astronomers to "examine the remnant of a supernova at a stage that's never been observed before." Nature elaborates:

The supernova remnant, dubbed G1.9+0.3, was first found by radio astronomers using the Very Large Array in 1985, but its age was unclear. Follow-up X-ray observations last year, taken with the Chandra satellite, showed that the object had enlarged by 16% over the intervening 22 years. This expansion is the fastest yet seen in a remnant, Reynolds says. The speed of the expansion has also allowed the researchers to backtrack to the time of the explosion, estimating the supernova's age at 140 years.

The find fills in a strange gap in the record of supernova explosions. Spiral galaxies such as the Milky Way are supposed to generate roughly three supernovae per century. Astronomers thus expect to see as many as 60 supernova explosions that are younger than 2,000 years old, but fewer than 10 have been found.

The Milky Way may have an anomalously low rate of stellar explosions, says Reynolds. But a search of potential supernovae, of which the latest G1.9+0.3 find is part, might help fill in the gap.

According to Robert Kirschner from the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, the discovery of G1.9+0.3 "should yield clues on how stars end their lives, expanding in a rapid shock wave that spews heavier elements such as iron and calcium into the Universe." Kirschner also told Popular Mechanics, "The calcium that's in your bones, the iron in your blood, came from a supernova that exploded before the sun was formed. It seems reasonable for us to want to know how these things get formed when stars explode."

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