stellar evolution Archives

December 13, 2022December 13, 2022 by Matt Williams

Astronomers Spot Three Interacting Systems with Twin Discs

Artist's conceptualization of the dusty TYC 8241 2652 system as it might have appeared several years ago when it was emitting large amounts of excess infrared radiation. Credit: Gemini Observatory/AURA artwork by Lynette Cook. https://www.gemini.edu/node/11836

According to the most widely-accepted theory about star formation (Nebular Hypothesis), stars and planets form from huge clouds of dust and gas. These clouds undergo gravitational collapse at their center, leading to the birth of new stars, while the rest of the material forms disks around it. Over time, these disks become ring structures that accrete to form systems of planets, planetoids, asteroid belts, and Kuiper belts. For some time, astronomers have questioned how interactions between early stellar environments may affect their formation and evolution.

For instance, it has been theorized that gravitational interactions with a passing star or shock waves from a supernova might have triggered the core collapse that led to our Sun. To investigate this possibility, an international team of astronomers observed three interacting twin disc systems using the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) on the ESO’s Very Large Telescope (VLT). Their findings show that due to their dense stellar environments, gravitational encounters between early-stage star systems play a significant role in their evolution.

October 26, 2022October 26, 2022 by Brian Koberlein

The Smallest, Lightest Neutron Star Ever Seen Could be a “Strange Star”

The supernova remnant HESS J1731-347 surrounding a small neutron star. Credit: Victor Doroshenko

The life of every star is a fight against gravity. Stars are so massive they risk collapsing under their own weight, but this is balanced by the heat and pressure a star generates through nuclear fusion. Eventually, that comes to an end. The outer layers of a star will be cast off, and the remaining core will become a stellar remnant. Which kind of remnant depends on the mass of the core.

July 30, 2022July 30, 2022 by Brian Koberlein

When Stars eat Their Planets, the Carnage can be Seen Billions of Years Later

Artist view of a large planet soon to be devoured by its star. Credit: NASA, ESA, and G. Bacon (STScI). Science Credit: NASA, ESA, and C. Haswell (The Open University, UK)

The vast majority of stars have planets. We know that from observations of exoplanetary systems. We also know some stars don’t have planets, and perhaps they never had planets. This raises an interesting question. Suppose we see an old star that has no planets. How do we know if ever did? Maybe the star lost its planets during a close approach by another star, or maybe the planets spiraled inward and were consumed like Chronos eating his children. How could we possibly tell? A recent study on the arXiv answers half that question.

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.

January 18, 2022January 18, 2022 by Evan Gough

These Newly-Discovered Planets are Doomed

An artist’s rendition of what a planetary system similar to TOI-2337b, TOI-4329b, and TOI-2669b might look like, where a hot Jupiter-like exoplanet orbits an evolved, dying star. Image Credit: Karen Teramura/University of Hawai?i Institute for Astronomy

Astronomers have spied three more exoplanets. But the discovery might not last long. Each planet is in a separate solar system, and each orbits perilously close to its star. Even worse, all of the stars are dying.

The results?

Three doomed planets.

November 29, 2021November 29, 2021 by Nancy Atkinson

NASA Simulation Shows What Happens When Stars Get Too Close to Black Holes

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.

What they found was surprising.

September 29, 2021September 29, 2021 by Brian Koberlein

Aging White Dwarfs Become Even More Magnetic

An artist view of a highly magnetized neutron star -- a magnetar. It's thought that these objects have solid surfaces and suffer eruptions when their magnetic fields are disturbed. Credit: Carl Knox/ OzGrav

In a few billion years the Sun will end its life as a white dwarf. As the Sun runs out of hydrogen to fuse for energy it will collapse under its own weight. Gravity will compress the Sun until it’s roughly the size of Earth, at which point a bit of quantum physics will kick in. Electrons from the Sun’s atoms will push back against gravity, creating what is known as degeneracy pressure. Once a star reaches this state it will cool over time, and the once brilliant star will eventually fade into the dark.

September 7, 2021September 7, 2021 by Paul M. Sutter

Many Sunlike Stars Gobbled up Some of Their Planets

New research shows that other sunlike stars in our galaxy aren’t so kind to their planets. Up to a quarter of them may consume planets before they even establish a solar system. That consumption leaves behind a distinct chemical fingerprint in the stars, which can help researchers understand how common planetary systems are…and how often they get destroyed.

August 11, 2021August 11, 2021 by Brian Koberlein

Astronomers Find a Nearby Star That a Spitting Image of a Young Sun

Illustration of what the Sun may have been like 4 billion years ago. Credit: NASA's Goddard Space Flight Center/Conceptual Image Lab

Our Sun is about 4.6 billion years old. We know that from models of Sun-like stars, as well as through our observations of other stars of similar mass. We know that the Sun has grown hotter over time, and we know that in about 5 billion years it will become a red giant star before ending its life as a white dwarf. But there are many things about the Sun’s history that we don’t understand. How active was it in its youth? What properties of the young Sun allowed life to form on Earth billions of years ago?

March 19, 2021March 19, 2021 by Matthew Cimone

An All-Sky X-Ray Survey Finds the Biggest Supernova Remnant Ever Seen

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.