Betelgeuse was the first star directly imaged -- besides our own Sun, of course. Image obtained by the Hubble Space Telescope. Credit: Andrea Dupree (Harvard-Smithsonian CfA), Ronald Gilliland (STScI), NASA and ESA
A couple of years ago, Betelgeuse generated much interest when it started dimming. That caught the attention of astronomers worldwide, who tried to understand what was happening. Was it about to go supernova?
Evidence showed that dust was the most likely culprit for the red supergiant’s dimming, though there are still questions. A new study shows that the star was behaving strangely just before the dimming.
Millions of stars that can grow up to 620 million miles in diameter, known as ‘red giants,’ exist in our galaxy, but it has been speculated for a while that there are some that are possibly much smaller. Now a team of astronomers at the University of Sydney have discovered several in this category and have published their findings in the journal Nature Astronomy.
“It’s like finding Wally… we were extremely lucky to find about 40 slimmer red giants, hidden in a sea of normal ones. The slimmer red giants are either smaller in size or less massive than normal red giants.”
An illustration of a protoplanetary disk. The solar system formed from such a disk. Astronomers suggest this birthplace was protected by a larger filament of molecular gas and dust early in history. Credit: NASA/JPL-Caltech/T. Pyle (SSC)
When young stars coalesce out of a cloud of molecular hydrogen, a disk of leftover material called a protoplanetary disk surrounds them. This disk is where planets form, and astronomers are getting better at peering into those veiled environments and watching embryonic worlds take shape. But young stars aren’t the only stars with disks of raw material rotating around them.
Some old, dying stars also have disks. Can a second generation of planets form under those conditions?
For the first time, a team of astronomers have imaged in real-time as a red supergiant star reached the end of its life. They watched as the star convulsed in its death throes before finally exploding as a supernova.
And their observations contradict previous thinking into how red supergiants behave before they blow up.
Sizes of giant stars relative to our Sun. Going from the G-type to K-type to M-types, giant stars get progressively redder (cooler) and larger. Late M-type giants are more than 100 times the size of our Sun.
Image Credit: Lowell Observatory.
Astronomers have a new tool to help them understand giant stars. It’s a detailed study of the precise temperatures and sizes of 191 giant stars. The authors of the work say that it’ll serve as a standard reference on giant stars for years to come.
It’ll also shed some light on what the Sun will go through late in its life.
From left to right, this illustration shows four snapshots of a virtual Sun-like star as it approaches a black hole with 1 million times the Sun's mass. The star stretches, looses some mass, and then begins to regain its shape as it moves away from the black hole. Credit: NASA's Goddard Space Flight Center/Taeho Ryu (MPA)
What happens to a star when it strays too close to a monster black hole? Astronomers have wondered why some stars are ripped apart, while others manage to survive a close encounter with a lurking black hole, only a little worse for wear.
To figure out the dynamics of such an event, scientists built a supercomputer simulation and tested it out on eight different types of stars. The stars were sent towards a virtual black hole, 1 million times the mass of the Sun.
Astronomers recently witnessed supernova SN 2020fqv explode inside the interacting Butterfly galaxies, located about 60 million light-years away in the constellation Virgo. Researchers quickly trained NASA's Hubble Space Telescope on the aftermath. Along with other space- and ground-based telescopes, Hubble delivered a ringside seat to the first moments of the ill-fated star's demise, giving a comprehensive view of a supernova in the very earliest stage of exploding. Hubble probed the material very close to the supernova that was ejected by the star in the last year of its life. These observations allowed researchers to understand what was happening to the star just before it died, and may provide astronomers with an early warning system for other stars on the brink of death.
Credits: NASA, ESA, Ryan Foley (UC Santa Cruz); Image Processing: Joseph DePasquale (STScI)
If it weren’t for supernova remnants we wouldn’t have much knowledge of supernovae themselves. If a supernova explosion is the end of a star’s life, then we can also thank forensic astrophysics for much of our knowledge. The massive exploding stars leave behind brilliant and mesmerizing evidence of their catastrophic ends, and much of what we know about supernovae comes from studying the remnants rather than the explosions themselves. Supernova remnants like the Crab Nebula and SN 1604 (Kepler’s Supernova) are some of our most-studied objects.
Observing an active supernova in the grip of its own destruction can be difficult. But it looks like the Hubble Space Telescope is up to the task.
We thought we understood how stars are formed. It turns out, we don’t. Not completely, anyway. A new study, recently conducted using data from the Hubble Space Telescope, is sending astronomers back to the drawing board to rewrite the accepted model of stellar formation.
Composite Image of radio and x-ray observations of the Hoinga Supernova Remnant Credit: eROSITA/MPE (X-ray), CHIPASS/SPASS/N. Hurley-Walker, ICRAR-Curtin (Radio)
Our sky is missing supernovas. Stars live for millions or billions of years. But given the sheer number of stars in the Milky Way, we should still expect these cataclysmic stellar deaths every 30-50 years. Few of those explosions will be within naked-eye-range of Earth. Nova is from the Latin meaning “new”. Over the last 2000 years, humans have seen about seven “new” stars appear in the sky – some bright enough to be seen during the day – until they faded after the initial explosion. While we haven’t seen a new star appear in the sky for over 400 years, we can see the aftermath with telescopes – supernova remnants (SNRs) – the hot expanding gases of stellar explosions. SNRs are visible up to a 150,000 years before fading into the Galaxy. So, doing the math, there should be about 1200 visible SNRs in our sky but we’ve only managed to find about 300. That was until “Hoinga” was recently discovered. Named after the hometown of first author Scientist Werner Becker, whose research team found the SNR using the eROSITA All-Sky X-ray survey, Hoinga is one of the largest SNRs ever seen.
Composite of the X-ray (pink) and radio (blue) image of Hoinga. The X-rays discovered by eROSITA are emitted by the hot debris of the exploded progenitor star. Radio antennae on Earth detect radiation emission from electrons in the outer shell of the supernova Credit: eROSITA/MPE (X-ray), CHIPASS/SPASS/N. Hurley-Walker, ICRAR-Curtin (Radio)Continue reading “An All-Sky X-Ray Survey Finds the Biggest Supernova Remnant Ever Seen”
Astronomers have spotted the remnant of a rare type of supernova explosion. It’s called a Type Iax supernova, and it’s the result of an exploding white dwarf. These are relatively rare supernovae, and astronomers think they’re responsible for creating many heavy elements.
They’ve found them in other galaxies before, but this is the first time they’ve spotted one in the Milky Way.
