stellar evolution Archives

August 28, 2024August 28, 2024 by Mark Thompson

Is Betelgeuse Actually a Binary Star?

This image, made with the Atacama Large Millimeter/submillimeter Array (ALMA), shows the red supergiant Betelgeuse — one of the largest stars known. In the millimeter continuum the star is around 1400 times larger than our Sun. The overlaid annotation shows how large the star is compared to the Solar System. Betelgeuse would engulf all four terrestrial planets — Mercury, Venus, Earth and Mars — and even the gas giant Jupiter. Only Saturn would be beyond its surface. Link Betelgeuse captured by ALMA Scientific paper

Betel-gurz or Beetle-juice has been a favourite among amateur astronomers for many years. However you pronounce it, its unexpected dimming draw even more attention to this red supergiant variable star in Orion. It has a few cycles of variability, one of them occurs over a 2,170 day period, 5 times longer than its normal pulsation period. A paper has just been published that suggests a companion star of 1.17 solar masses could be the cause. It would need an orbit about 2.43 times the radius of Betelgeuse and it might just lead to the modulation of dust in the region that causes the variations we see.

June 30, 2024June 30, 2024 by Mark Thompson

Merging Galaxies Make for Explosive Star Formation

A festive array of bright pinks and blues makes for a remarkable sight in this image captured with the Gemini North telescope, one half of the International Gemini Observatory. Resembling a cloud of cosmic confetti, this image is being released in celebration of Gemini North’s 25th anniversary. NGC 4449 is a prime example of starburst activity caused by the interacting and mingling of galaxies as it slowly absorbs its smaller galactic neighbors.

The Gemini Observatory has unveiled a striking new image that shows star formation within the irregular galaxy NGC 4449. This galaxy is categorised as a “Magellanic-type” galaxy due to its similarities with the Magellanic Clouds, although it is smaller in size. Surrounding NGC 4449 is a halo of smaller dwarf galaxies, two of which are currently merging with it. This merger is causing clouds of gas to collide, fuelling the surge in star formation observed in NGC 4449.

May 14, 2024May 14, 2024 by Matt Williams

White Dwarfs are Often Polluted With Heavier Elements. Now We Know Why

In this artist's illustration, lumps of debris from a disrupted planetesimal are irregularly spaced on a long and eccentric orbit around a white dwarf. Credit: Dr Mark Garlick/The University of Warwick

When stars exhaust their hydrogen fuel at the end of their main sequence phase, they undergo core collapse and shed their outer layers in a supernova. Whereas particularly massive stars will collapse and become black holes, stars comparable to our Sun become stellar remnants known as “white dwarfs.” These “dead stars” are extremely compact and dense, having mass comparable to a star but concentrated in a volume about the size of a planet. Despite being prevalent in our galaxy, the chemical makeup of these stellar remnants has puzzled astronomers for years.

For instance, white dwarfs consume nearby objects like comets and planetesimals, causing them to become “polluted” by trace metals and other elements. While this process is not yet well understood, it could be the key to unraveling the metal content and composition (aka. metallicity) of white dwarf stars, potentially leading to discoveries about their dynamics. In a recent paper, a team from the University of Colorado Boulder theorized that the reason white dwarf stars consume neighboring planetesimals could have to do with their formation.

April 15, 2024April 15, 2024 by Mark Thompson

Baby Stars Discharge “Sneezes” of Gas and Dust

The baby star at the center surrounded by a bright disk called a protostellar disk. Spikes of magnetic flux, gas, and dust in blue. Researchers found that the protostellar disk will expel magnetic flux, gas, and dust—much like a sneeze—during a star's formation.

I’m really not sure what to call it but a ‘dusty sneeze’ is probably as good as anything. We have known for some years that stars surround themselves with a disk of gas and dust known as the protostellar disk. The star interacts with it, occasionally discharging gas and dust regularly. Studying the magnetic fields revealed that they are weaker than expected. A new proposal suggests that the discharge mechanism ‘sneezes’ some of the magnetic flux out into space. Using ALMA, the team are hoping to understand the discharges and how they influence stellar formation.

April 9, 2024April 9, 2024 by Evan Gough

What Happens to Solar Systems When Stars Become White Dwarfs?

In a couple billion years, our Sun will be unrecognizable. It will swell up and become a red giant, then shrink again and become a white dwarf. The inner planets aren’t expected to survive all the mayhem these transitions unleash, but what will happen to them? What will happen to the outer planets?

March 31, 2024March 31, 2024 by Mark Thompson

It Takes a Supercomputer to Properly Simulate a Neutron Star’s Surface

Neutron stars, the remains of massive stars that have imploded and gone supernova at the end of their life, can still create massive flares. These incredible bursts of energy release X-rays that propagate through space. It is a complex process to simulate but astronomers have turned to a supercomputer to help. Modelling the twisting magnetic fields, the interaction with gas and dust, the surface of flaring neutron stars has been revealed in incredible 3D.

March 29, 2024March 29, 2024 by Mark Thompson

Neutron Stars are Jetting Material Away at 40% the Speed of Light

It’s a well known fact that black holes absorb anything that falls into them. Often before material ‘vanishes’ inside it forms into an accretion disk around them. Like the progenitor stars, the black holes have powerful magnetic fields and these can generate jets that blast away from the black hole. A similar process occurs in neutron stars that are orbiting other stars and recent observations holes have shown that some material in the jets travel at speeds 35-40% the speed of light.

March 12, 2024March 14, 2024 by Mark Thompson

Black Holes are Tearing Stars Apart All Around Us

Illustration of star remnants after it is shredded by a supermassive black hole. Credit: NASA

Galaxy NGC3799 lies around 16 million light years from Earth. Any event observed today within that galaxy took place 16 million years ago. One such event was observed in February 2023 when a surge in brightness in the core was followed by a rapid dimming. The observations that followed revealed that the event was a star being torn apart by a supermassive black hole at the heart of the galaxy. This is not the first time such an event has been observed but it is the first to be within our galactic backyard suggesting it may be more common that first thought.

March 6, 2024March 6, 2024 by Brian Koberlein

Webb Sees a System That Just Finished Forming its Planets

An artistic impression adapted to highlight gas dispersing from a planet-forming disk. Credit: ESO/M. Kornmesser

Nearly 5 billion years ago a region of gas gravitationally collapsed within a vast molecular cloud. At the center of the region, the Sun began to form, while around it formed a protoplanetary disk of gas and dust out of which Earth and the other planets of the solar system would form. We know this is how the solar system began because we have observed this process in systems throughout the galaxy. But there are details of the process we still don’t understand, such as why gas planets are relatively rare in our system.

February 13, 2024February 13, 2024 by Evan Gough

Dying Stars Could Have Completely New Habitable Zones

As stars like our Sun age, their habitable zones shift, and they can warm planets that were once frozen. Image Credit: ESO/L. Calçada

Aging stars that become red giants increase their luminosity and can wreak havoc on planets that were once in the star’s habitable zones. When the Sun becomes a red giant and expands, its habitable zone will move further outward, meaning Earth will likely lose its atmosphere, its water, and its life. But for planets further out, their time in the habitable zone will just begin.

Is there enough time for life to arise on these newly habitable planets?