Astronomers estimate that a supernova explosion occurs once or twice a
century in the Milky Way and one per second in the observable universe.
The expanding blast wave and hot stellar debris slowly dissipate over
hundreds of thousands of years, eventually mixing with and becoming
indistinguishable from interstellar gas. While performing an extensive
X-ray survey of our galaxy's central regions, NASA's Swift satellite
has uncovered the previously unknown remains of a shattered star.
Designated G306.3–0.9 after the coordinates of its sky position, the new
object ranks among the youngest-known supernova remnants in our Milky Way galaxy.
"Astronomers have previously cataloged more than 300 supernova remnants
in the galaxy," said lead scientist Mark Reynolds, a postdoctoral
researcher at the University of Michigan in Ann Arbor. "Our analysis
indicates that G306.3–0.9 is likely less than 2,500 years old, making it
one of the 20 youngest remnants identified." Reynolds leads the Swift
Galactic Plane Survey, a project to image a two-degree-wide strip along
the Milky Way’s central plane at X-ray and ultraviolet energies at the
same time.
Using an estimated distance of 26,000 light-years for G306.3–0.9, the
scientists determined that the explosion’s shock wave is racing through
space at about 1.5 million mph (2.4 million km/h). The Chandra
observations reveal the presence of iron, neon, silicon and sulfur at
temperatures exceeding 50 million degrees F (28 million C), a reminder
not only of the energies involved but of the role supernovae play in
seeding the galaxy with heavy elements produced in the hearts of massive
stars.
"We don’t yet have enough information to determine what type of
supernova this was and therefore what type of star exploded, but we’ve
planned a further Chandra observation to improve the picture,” said
coauthor Jamie Kennea, also a researcher at the Swift MOC. "We see no
compelling evidence that the explosion formed a neutron star, and this
is something we hope can be determined one way or the other by future
work."
The wide view image above places G306.3–0.9 in context with
star-formation regions in southern Centaurus. Chandra X-ray observations
(blue), Spitzer infrared data (red, cyan), and radio observations
(purple) from the Australia Telescope Compact Array
are merged in this composite. The image is one degree across, which
corresponds to 450 light-years at the remnant's estimated distance.
The composite image below of G306.3–0.9 merges Chandra X-ray observations (blue), infrared data acquired by the Spitzer Space Telescope
(red and cyan) and radio observations (purple) from the Australia
Telescope Compact Array. The image is 20 arcminutes across, which
corresponds to 150 light-years at the remnant's estimated distance.
Like fresh evidence at a crime scene, young supernova remnants give
astronomers the best opportunity for understanding the nature of the
original star and the details of its demise. Supernova remnants emit
energy across the electromagnetic spectrum, from radio to gamma rays,
and important clues can be found in each energy band.
X-ray observations figure prominently in revealing the motion of the
expanding debris, its chemical content, and its interaction with the
interstellar environment, but supernova remnants fade out in X-ray light
after 10,000 years. Indeed, only half of those known in the Milky Way
galaxy have been detected in X-rays at all.
"The Swift survey leverages infrared imaging previously compiled by
NASA’s Spitzer Space Telescope and extends it into higher energies,"
said team member Michael Siegel, a research associate at the Swift
Mission Operations Center (MOC) in State College, Pa., which is operated
by Penn State University. "The infrared and X-ray surveys complement
each other because light at these energies penetrates dust clouds in the
galactic plane, while the ultraviolet is largely extinguished."
To further investigate the object, the team followed up with an
83-minute exposure using NASA’s Chandra X-ray Observatory and additional
radio observations from the Australia Telescope Compact Array (ATCA),
located near the town of Narrabri in New South Wales.
A paper describing the team’s findings will appear in an upcoming
edition of The Astrophysical Journal and was published online on Friday.
Image Credits: X-ray: NASA/CXC/Univ. of Michigan/M. Reynolds et al; Infrared: NASA/JPL-Caltech; Radio: CSIRO/ATNF/ATCA
Source: The Daily Galaxy Via NASA/SWIFT
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