red giant stars Archives

January 28, 2024January 28, 2024 by Brian Koberlein

New Types of Hidden Stars Seen for the First Time

Artist’s impression of a cloud of smoke and dust being thrown out by a red giant star. Credit: Philip Lucas/University of Hertfordshire

In the early days of telescopic astronomy, you could only focus on one small region of the sky at a time. Careful observations had to be done by hand, and so much of the breakthrough work centered around a particular object in the sky. A nebula or galaxy, quasar or pulsar. But over the years we’ve been able to build telescopes capable of capturing a wide patch of sky all at once, and with automation, we can now map the entire sky. Early sky surveys took years to complete, but many modern sky surveys can look for changes on the order of weeks or days. This ability to watch for changes across the sky is changing the way we do astronomy, and it is beginning to yield some interesting results. As a case in point, an infrared sky survey is revealing hidden stars we hadn’t noticed before.

March 23, 2023March 23, 2023 by Evan Gough

The Discovery of a Hot Neptune that Shouldn’t Exist

exoplanet hot jupiter transiting its star — This artist’s impression shows an ultra-hot exoplanet as it is about to transit in front of its host star. Credit: ESO

1800 light-years away, an unlikely survivor orbits an aged star. This rare planet is called a hot Neptune, and it’s one of only a small handful of hot Neptunes astronomers have found. Hot Neptunes are so close to their stars that the overpowering stellar radiation should’ve stripped away their atmospheres, leaving only a planetary core behind.

But this planet held onto its atmosphere somehow.

October 7, 2022October 7, 2022 by Evan Gough

Binary Stars Live Complicated Lives, Especially Near the End

Artist's impression of a red giant star. If the star is in a binary pair, what happens to its sibling? Credit:NASA/ Walt Feimer

We know what will happen to our Sun.

It’ll follow the same path other stars of its ilk follow. It’ll start running out of hydrogen, swell up and cool and turn red. It’ll be a red giant, and eventually, it’ll become so voluminous that it will consume the planets closest to it and render Earth uninhabitable. Then billions of years from now, it’ll create one of those beautiful nebulae we see in Hubble images, and the remnant Sun will be a shrunken white dwarf in the center of the nebula, a much smaller vestige of the luminous body it once was.

This is the predictable life the Sun lives as a solitary star. But what happens to stars that have a solar sibling? How would its binary companion fare?

June 16, 2022June 16, 2022 by Evan Gough

Astronomers Caught Betelgeuse Just Before it Started Dimming and Might Have Seen a Pressure Wave Rippling Through its Atmosphere

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.

April 22, 2022April 22, 2022 by Shawn DiCenza

Slimmed Down Red Giants Had Their Mass Stolen By a Companion Star

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.”
PhD candidate Mr Yaguang Li from the University of Sydney, as quoted from the source article.

April 8, 2022April 8, 2022 by Brian Koberlein

Dying Star Puffs out six Smoke Rings

Artist view of V Hya in its death throes. Credit: ALMA (ESO/NAOJ/NRAO)/S. Dagnello (NRAO/AUI/NSF)

Our Sun’s days are numbered. In about 5 billion years the Sun will expand into a red giant, casting off its outer layers before settling down to become a white dwarf. It’s the inevitable fate of most sunlike stars, and the process is well understood. But as a recent study shows, there are still a few things we have to learn about dying Suns.

December 7, 2021December 7, 2021 by Evan Gough

Giant Stars and the Ultimate Fate of the Sun

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.

July 26, 2021July 26, 2021 by Andy Tomaswick

When the Sun Dies, Earth’s Magnetosphere won’t Provide Protection any More

The Earth’s magnetic field is an underappreciated wonder of the natural world. It protects our atmosphere, provides some of the most breathtaking scenery when it creates auroras, and allows people to navigate from one side of the world to the other. Unfortunately, it won’t be able to save us from the death of the Sun though. At least that’s the finding of some new research by Dr. Dimitri Veras of the University of Warwick and Dr. Aline Vidotto of Trinity College Dublin.

March 12, 2021March 9, 2021 by Paul M. Sutter

Measuring the Temperatures of Red Giants is Actually Pretty Tricky

Red giant stars are, well, red and giant. But astronomers have always had difficulty estimating their temperatures, due to their complex and turbulent atmospheres. Without an accurate gauge of their temperatures, it’s difficult to tell when they will end their lives in gigantic supernova explosions. Now a team of astronomers have developed a more effective technique for taking the temperature of red giants, based on the amount of iron in the stars.

March 11, 2021March 9, 2021 by Paul M. Sutter

The Oldest Stars Help Tell us how big the Universe is

Artist’s impression of the star in its multi-million year long and previously unobservable phase as a large, red supergiant. Credit: CAASTRO / Mats Björklund (Magipics)

Astronomers are struggling to understand the discrepancies when measuring the expansion rate of the universe with different methods, and are desperate for any creative idea to break the tension. A new method involving some of the oldest stars in the universe could just do the trick.