Scientists obtain image of a star on the precipice
22/11/2024 6:07
Scientists have taken a
close-up picture of a star apparently in its death throes,
surrounded by gas and dust as it heads toward its demise in a
huge explosion called a supernova - the first time the events of
this pivotal stage have ever been imaged.
What makes this even more remarkable, according to the
researchers, is that the observed star resides not in our Milky
Way galaxy but in a neighboring galaxy called the Large
Magellanic Cloud.
It is the first zoomed-in image of a mature star in another
galaxy, though a stellar newborn in the Large Magellanic Cloud
was spotted in research published last year. Zoomed-in means the
image captures the star and its immediate surroundings.
The dying star, named WOH G64, is located about 160,000
light-years from Earth. A light-year is the distance light
travels in a year, 5.9 trillion miles (9.5 trillion km).
The image, somewhat fuzzy, was obtained using the European
Southern Observatory's Chile-based Very Large Telescope
Interferometer. It shows the star surrounded by a glowing
egg-shaped cocoon of gas and dust - called a nebula - apparently
ejected by the star. A faint oval ring beyond the cocoon,
perhaps made of more dust, is also seen.
"The star is in the last stage of its life before a stellar
demise," said astronomer Keiichi Ohnaka of Universidad Andrés
Bello in Chile, lead author of the study published on Thursday
in the journal Astronomy & Astrophysics.
"The reason we see these shapes is that the star is ejecting
more material in some directions than in other directions.
Otherwise, the structures would look spherical," Ohnaka said.
Another possible explanation for these shapes is the
gravitational influence of an as-yet undetected companion star,
Ohnaka said.
Before it started to blow off material, WOH G64 was
estimated at about 25 to 40 times the mass of the sun, according
to astronomer and study co-author Jacco van Loon of Keele
University in England. It is a type of massive star called a red
supergiant.
"Its estimated mass means it has lived for about 10 to 20
million years, and will soon die," van Loon said.
This represents the first image of a star "in this late
stage possibly going through a never-before-witnessed
metamorphosis prior to explosion," van Loon added.
"For the first time we have been able to see the structures
that wrap a star in its death throes," van Loon said. "Even in
our Milky Way galaxy we do not have such image."
Massive stars have shorter lives than less massive ones. For
instance, the sun is already more than 4.5 billion years old and
has billions more to go.
WOH G64's diameter is immense as it puffs up before its
expected explosion in the relatively near future. If it were
placed at the center of our solar system, it would extend all
the way to the orbit of Saturn, the sixth planet from the sun.
"We found out that WOH G64 has changed its appearance
noticeably in the last 10 years," Ohnaka said, adding that it
was becoming dimmer perhaps because its starlight is shrouded in
gas and dust it has expelled.
"This gives us a rare opportunity to witness a star's life
in real time, in particular the last stages of a heavyweight
star before its death in a supernova explosion," Ohnaka added.
The Large Magellanic Cloud is a satellite galaxy of the
Milky Way, as is another nearby galaxy called the Small
Magellanic Cloud. Both are smaller than our galaxy and offer
different galactic conditions.
The Large Magellanic Cloud, for instance, has less dust than
the Milky Way and a smaller content of what astronomers call
metallic elements - those other than hydrogen and helium. That
characteristic, van Loon said, "may make a difference in the way
stars live and die."
"Such conditions were more common in the early universe and
may resemble the Milky Way when it was young," van Loon added.
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