This is an artist’s impression of supernova 1993J,
which exploded in the galaxy M81. Using the Hubble Space Telescope, astronomers
have identified the blue helium-burning companion star, seen at the center of
the expanding nebula of debris from the supernova.
Image Credit:
NASA, ESA, G. Bacon (STScI)
Using NASA’s Hubble Space Telescope, astronomers have discovered a companion
star to a rare type of supernova. The discovery confirms a long-held theory that
the supernova, dubbed SN 1993J, occurred inside what is called a binary system,
where two interacting stars caused a cosmic explosion.
"This is like a crime scene, and we finally identified the robber," said Alex
Filippenko, professor of astronomy at University of California (UC) at Berkeley.
"The companion star stole a bunch of hydrogen before the primary star
exploded."
SN 1993J is an example of a Type IIb supernova, unusual stellar explosions
that contains much less hydrogen than found in a typical supernova. Astronomers
believe the companion star took most of the hydrogen surrounding the exploding
main star and continued to burn as a super-hot helium star.
“A binary system is likely required to lose the majority of the primary
star’s hydrogen envelope prior to the explosion. The problem is that, to date,
direct observations of the predicted binary companion star have been difficult
to obtain since it is so faint relative to the supernova itself,” said lead
researcher Ori Fox of UC Berkeley.
SN 1993J resides in the Messier 81 galaxy, about 11 million light-years away
in the direction of Ursa Major, the Great Bear constellation. Since its
discovery 21 years ago, scientists have been looking for the companion star.
Observations at the W. M. Keck Observatory on Mauna Kea, Hawaii, suggested that
the missing companion star radiated large amounts of ultraviolet (UV) light, but
the area of the supernova was so crowded that scientists could not be sure they
were measuring the right star.
The team combined optical light data and Hubble’s UV light images to
construct a spectrum that matched the predicted glow of a companion star, also
known as the continuum emission. Scientists were only recently able to directly
detect this light.
“We were able to get that UV spectrum with Hubble. This conclusively shows
that you have an excess of continuum emission in the UV, even after the light
from other stars has been subtracted,” said Azalee Bostroem of the Space
Telescope Science Institute (STScI) in Baltimore, Maryland.
Astronomers estimate a supernova occurs once every second somewhere in the
universe, yet they don’t fully understand how stars explode. Further research
will help astronomers better understand the properties of this companion star
and the different types of supernovae.
The results of this study were published in the July 20 issue of the
Astrophysical Journal.
The Hubble Space Telescope is a project of international cooperation between
NASA and the European Space Agency. NASA's Goddard Space Flight Center in
Greenbelt, Maryland, manages the telescope, while STScI conducts science
operations. STScI is operated for NASA by the Association of Universities for
Research in Astronomy, Inc., in Washington.
For images and more information about Hubble, visit:
NASA
Guillermo Gonzalo Sánchez Achutegui
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