About 140
years ago, our time, a stellar explosion lit up our galaxy with a blinding
flash of light, sending out powerful shock waves to boot. Now, astronomers have
spotted the youthful remains from the explosion.
The newly
discovered remains mark the youngest known supernova remnant in the Milky Way,
snagging the record from the previous holder, 330-year-old Cassiopeia
A.
Ever since
Cass-A was discovered in the 1950s, astronomers had been searching for
"missing supernovae" and their remnants. At around the same time of
the Cass-A discovery, astronomers also realized two or three supernovae should
light up the Milky Way every century, resulting in about 60 supernova remnants
younger than 2,000 years old. To date, just 10 such remnants have been
confirmed.
And so G1.9+0.3,
the new remnant detailed in the June 10 issue of the Astrophysical Journal
Letters, is the prize from the astronomers' 50-year galactic hunt.
Stellar
explosions
Supernovae
are considered some of the most violent events in the universe. They are
massive stars at the end of their lives, exploding with such force that they
generate a flash of radiation and shock waves akin to a sonic boom.
Debris
thrown outward by the explosion sometimes crashes into surrounding material,
resulting in a supernova remnant. This shell of hot gas and high-energy
particles glows as X-rays, radio waves and other wavelengths of radiation for
thousands of years.
Supernovae
and their remnants are critical for creating and distributing the majority of
the elements in the universe through the interstellar medium, spreading
everything from cobalt to gold to radium to planets, plants, people and far
beyond.
Youthful
remains
The new
supernova remnant discovery involved NASA's Chandra X-ray Observatory and
National Radio Astronomy Observatory's Very Large Array (VLA) radio telescope.
By
comparing X-ray and radio images from 1985 and 2007, which show the supernova
remnant is expanding, the astronomers estimated G1.9+0.3's age. A new VLA image
taken this year confirms the age and expansion rate of 35 million mph (56
million kph), which is an unprecedented expansion speed for a supernova
remnant.
The
astronomers estimate the centenarian is hiding out about 1,000 light-years from
the galactic center, or roughly 25,000 light-years from us. A light-year is the
distance light travels in one year, or about 6 trillion miles (10 trillion
kilometers). So in
reality, the explosion occurred about 25,140 years ago and the light reached
us 140 years ago.
However,
the bright burst would have been invisible to celestial enthusiasts with only
optical telescopes at the time, due to a veil of interstellar gas and dust.
"If
not for all the interstellar 'gunk' between us and this object, people would
have seen this supernova as a new star in the constellation Sagittarius in the
years around 1870 to 1900," said lead researcher Stephen Reynolds, an
astrophysicist at North Carolina State University.
G1.9+0.3
most probably originated from a Type Ia supernova, the researchers say, in
which a white dwarf star siphons hydrogen from a companion star and thus bulks
up its mass. When the white dwarf reaches a weight that's 1.4 times more
massive than the sun, the star explodes.
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