stellar evolution Archives

February 6, 2024February 6, 2024 by Mark Thompson

Astronomers See 18 Examples of Stars Getting Torn Apart by Black Holes

MIT scientists have identified 18 new tidal disruption events (TDEs) — extreme instances when a nearby star is tidally drawn into a black hole and ripped to shreds. The detections more than double the number of known TDEs in the nearby universe. Credits:Credit: Courtesy of the researchers, edited by MIT News

Black holes have always held a special fascination for me ever since I was a geeky kid looking up at the stars. Their intense forces are the stuff of science fiction and can tear a star to pieces. This process is violent and can send bursts of electromagnetic radiation across the Cosmos. A paper recently published announces the discovery of 18 new tidal events just like this, doubling the number of identified shredded stars.

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.

January 2, 2024January 2, 2024 by Mark Thompson

Simulation Perfectly Matches What We See When Neutron Stars Collide

Numerical simulation of the resulting ejecta material of two merging neutron stars. Red colors refer to ejected material with a high fraction of neutrons which will appear typically redder than blue material that contains a higher fraction of protons. © I. Markin (University of Potsdam)

There are many mysteries in the world of astronomy and a fair number relate to the processes during the end of the life of a super massive star. Throw in the complexity of collisions and you have a real head scratching problem on your hands. In 2017 colliding neutron stars were detected and the data has allowed a new simulation to be tested with predictions beautifully matching observation.

July 21, 2023July 21, 2023 by Brian Koberlein

One Side of This White Dwarf is Covered in Hydrogen While the Other Side is Helium.

Illustration of the newly-discovered white dwarf. Credit: K. Miller, Caltech/IPAC

Sunlike stars and those smaller than the Sun end their lives as white dwarfs. Without a continued source of energy from hydrogen fusion, these stars eventually collapse under their own weight. They would continue collapsing were it not for the pressure of electrons. As long as the remaining mass of a star is less than about 1.4 Suns, the electron pressure and gravitational pull will balance each other, creating a white dwarf.

July 13, 2023July 13, 2023 by Brian Koberlein

Celebrate a Year of JWST With This Ludicrous Image of Rho Ophiuchi

JWST image of the star forming region Rho Ophiuchi. Credit: NASA, ESA, CSA, STScI, Klaus Pontoppidan (STScI)

Astronomy is driven by data. We take spectra of distant galaxies, plot the temperatures and brightness of main sequence stars, and graph the gravitational chirps of merging black holes. All of this data allows us to understand the universe around us. We don’t need images to do that, just data. But we still capture images even when we already have the data. We value them for their wondrous beauty, and for the stories they tell. This is why to celebrate a year of gathering data the James Webb Space Telescope (JWST) released a stunningly beautiful image that also tells a wondrous tale.

July 10, 2023July 10, 2023 by Brian Koberlein

A Neutron Star is Unwinding a Companion Star

Artist impression of a star being stripped by its companion. Credit: Elisa Schösser

Close binary stars play several important roles in astronomy. For example, Type Ia supernovae, used to measure galactic distances, occur when a neutron star in a binary system reaches critical mass. These stars are also the source of x-ray binaries and microquasars, which help astronomers understand supermassive black holes and active galactic nuclei. But the evolutionary process of close binaries is still not entirely understood. That’s changing thanks in part to a new discovery of a close binary in its intermediate stage.

July 2, 2023July 2, 2023 by Brian Koberlein

A Planet Was Swallowed by a Red Giant, But it Survived

Artist view of Halla as two stars merge to become the star Baekdu. Credit: W. M. Keck Observatory/Adam Makarenko

The Sun is going to kill us. Not anytime soon, but it will kill us. At the moment the Sun keeps itself going by fusing hydrogen into helium and other heavier elements, but in five or so billion years it is going to run out of hydrogen. When that happens, the Sun will make a desperate attempt to keep going by fusing helium. During this period it will swell to a red giant, likely so large that it engulfs the Earth, baking it to a crisp in its diffuse hot atmosphere.

June 9, 2023June 12, 2023 by Brian Koberlein

Has JWST Finally Found the First Stars in the Universe?

Artist's view of several Population III stars. Credit: NASA/WMAP Science Team

In astronomy, elements other than hydrogen and helium are called metals. While that might make your high-school chemistry teacher cringe, it makes sense for astronomers. The two lightest elements were the first to appear in the universe. They are the atomic remnants of the big bang and make up more than 99% of atoms in the universe. All the other elements, from carbon to iron to gold, were created through astrophysical processes. Things like nuclear fusion in stellar cores, supernova explosions, and collisions of white dwarfs and neutron stars.

May 22, 2023May 22, 2023 by Brian Koberlein

There's So Much Going on in This Star-Forming Nebula

A view of the Lupus 3 dark nebula and nearby protostars. Credit: CTIO/NOIRLab/DOE/NSF/AURA/ T.A. Rector (University of Alaska Anchorage/NSF’s NOIRLab)

There are some astronomical images that capture rapturous beauty, with their brilliant colors and interplay of shadow and light. A beautiful image can be enough to stir the soul, but in astronomy they often also have a story to tell. An example of this can be seen in a recent image released by NSF’s NOIRLab.

April 29, 2023April 29, 2023 by Brian Koberlein

These Stars are Already Merging, but Their Future Will Be Catastrophic

Artist's view of the contact binary that will eventually merge as black holes. Credit: UCL / J. daSilva

Close-orbiting binaries are a ticking time bomb. Over time they spiral ever closer to each other until they merge in a cataclysmic explosion such as a supernova. But in the middle of their story, things can get interesting. Some stars collapse into a white dwarf before merging with their partner, others edge so close to each other that their surfaces touch for a time, becoming contact binaries before finally colliding. But one newly discovered binary system will have a wild ride before its final demise.