By Will Dunham
WASHINGTON (Reuters) – Scientists have taken a close-up picture of a dying star, surrounded by gas and dust as it headed for its demise in a massive explosion called a supernova – the first such event of its kind. they used to have pictures.
What makes this even more surprising, according to the researchers, is that the observed star does not reside in our own Milky Way but in a nearby galaxy called the Large Magellanic Cloud.
It is the first drawn-in image of an adult star in another star, although a newborn in the Large Magellanic Cloud was identified in research published last year. Zoomed-in means that the image captures the stars and their locations.
The dying star, called WOH G64, is located about 160,000 light-years from Earth. A light-year is the distance traveled by light in a year, 5.9 trillion miles (9.5 trillion km).
This seemingly mysterious image was obtained using the European Southern Observatory’s Chile-based Very Large Telescope Interferometer. It shows the star surrounded by a bright egg-shaped shell of gas and dust – called a nebula – apparently ejected by the star. A faint oval ring beyond, probably made of a lot of dust, is also visible.
“The star is in the last stage of its life before it collapses,” said astronomer Keiichi Ohnaka of the Universidad Andrés Bello in Chile, lead author of the study published Thursday in the journal Astronomy & Astrophysics.
“The reason we see these shapes is that the star is emitting more material in some directions than in others. Otherwise, the shapes would look like circles,” said Ohnaka.
One possible explanation for these patterns is the gravitational pull of another star that hasn’t been detected yet, Ohnaka said.
Before it began ejecting objects, WOH G64 was estimated to be 25 to 40 times the length of the sun, according to astronomer and study co-author Jacco van Loon of Keele University in England. It is a type of giant star called a red supergiant.
“Its estimated weight means it lived for about 10 to 20 million years, and it will die soon,” said van Loon.
This represents the first image of a star “in this late period that may not have witnessed a metamorphosis before it exploded,” van Loon added.
“For the first time we have been able to see the structures that surround a star in its dying state,” said van Loon. “Even in our own galaxy we don’t have such a picture.”
Major stars have shorter lifespans. For example, the sun is over 4.5 billion years old and has billions more to go.
WOH G64 has a large diameter as it brags about its expected explosion in the near future. If it were placed at the center of our solar system, it would stretch all the way to Saturn’s orbit, the sixth planet from the sun.
“We found that WOH G64 has changed its appearance significantly over the past decade,” Ohnaka said, adding that it is now dimming because its starlight is obscured by the gas and dust it has ejected.
“This gives us a rare opportunity to see the life of a star in real time, especially the final stages of a heavyweight star before it dies 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 example, is less dusty than the Milky Way and contains less of what astronomers call metallic elements – other than hydrogen and helium. That quality, van Loon said, “can make a difference in how a star lives and dies.”
“Such conditions were often seen in early skies and may resemble the Milky Way when it was young,” van Loon added.
(Reporting by Will Dunham, Editing by Rosalba O’Brien)