A new report from the European Southern Observatory (ESO):

Metal scar found on cannibal star

When a star like our Sun reaches the end of its life, it can ingest the surrounding planets and asteroids that were born with it. Now, using the European Southern Observatory’s Very Large Telescope (ESO’s VLT) in Chile, researchers have found a unique signature of this process for the first time — a scar imprinted on the surface of a white dwarf star. The results are published today in The Astrophysical Journal Letters.

“It is well known that some white dwarfs — slowly cooling embers of stars like our Sun — are cannibalising pieces of their planetary systems. Now we have discovered that the star’s magnetic field plays a key role in this process, resulting in a scar on the white dwarf’s surface,”

says Stefano Bagnulo, an astronomer at Armagh Observatory and Planetarium in Northern Ireland, UK, and lead author of the study.

The scar the team observed is a concentration of metals imprinted on the surface of the white dwarf WD 0816-310, the Earth-sized remnant of a star similar to, but somewhat larger than, our Sun.

“We have demonstrated that these metals originate from a planetary fragment as large as or possibly larger than Vesta, which is about 500 kilometres across and the second-largest asteroid in the Solar System,”

says Jay Farihi, a professor at University College London, UK, and co-author on the study.

The observations also provided clues to how the star got its metal scar. The team noticed that the strength of the metal detection changed as the star rotated, suggesting that the metals are concentrated on a specific area on the white dwarf’s surface, rather than smoothly spread across it. They also found that these changes were synchronised with changes in the white dwarf’s magnetic field, indicating that this metal scar is located on one of its magnetic poles. Put together, these clues indicate that the magnetic field funneled metals onto the star, creating the scar [1].

“Surprisingly, the material was not evenly mixed over the surface of the star, as predicted by theory. Instead, this scar is a concentrated patch of planetary material, held in place by the same magnetic field that has guided the infalling fragments,”

says co-author John Landstreet, a professor at Western University, Canada, who is also affiliated with the Armagh Observatory and Planetarium.

“Nothing like this has been seen before.”

To reach these conclusions, the team used a ‘Swiss-army knife’ instrument on the VLT called FORS2, which allowed them to detect the metal scar and connect it to the star’s magnetic field.

“ESO has the unique combination of capabilities needed to observe faint objects such as white dwarfs, and sensitively measure stellar magnetic fields,”

says Bagnulo. In their study, the team also relied on archival data from the VLT’s X-shooter instrument to confirm their findings.

Harnessing the power of observations like these, astronomers can reveal the bulk composition of exoplanets, planets orbiting other stars outside the Solar System. This unique study also shows how planetary systems can remain dynamically active, even after ‘death’.

Notes

[1] Previously, astronomers have observed numerous white dwarfs polluted by metals that were scattered over the surface of the star. These are known to originate from disrupted planets or asteroids that veer too close to the star, following star-grazing orbits similar to those of comets in our Solar System. However, for WD 0816-310, the team is confident that vaporised material was ionised and guided onto the magnetic poles by the white dwarf’s magnetic field. The process shares similarities to how auroras form on Earth and on Jupiter.

Links

• Research paper
• Photos of the VLT
• For journalists: subscribe to receive our releases under embargo in your language
• For scientists: got a story? Pitch your research

=== Amazon Ads ===

Celestron – NexStar 130SLT Computerized Telescope –
Compact and Portable –
Newtonian Reflector Optical Design –
SkyAlign Technology –
Computerized Hand Control –
130mm Aperture

====

For the Love of Mars:
A Human History of the Red Planet

A new report from the European Southern Observatory (ESO):

Brightest and fastest-growing: astronomers identify
record-breaking quasar

Using the European Southern Observatory’s (ESO) Very Large Telescope (VLT), astronomers have characterised a bright quasar, finding it to be not only the brightest of its kind, but also the most luminous object ever observed. Quasars are the bright cores of distant galaxies and they are powered by supermassive black holes. The black hole in this record-breaking quasar is growing in mass by the equivalent of one Sun per day, making it the fastest-growing black hole to date.

The black holes powering quasars collect matter from their surroundings in a process so energetic that it emits vast amounts of light. So much so that quasars are some of the brightest objects in our sky, meaning even distant ones are visible from Earth. As a general rule, the most luminous quasars indicate the fastest-growing supermassive black holes.

We have discovered the fastest-growing black hole known to date. It has a mass of 17 billion Suns, and eats just over a Sun per day. This makes it the most luminous object in the known Universe,

says Christian Wolf, an astronomer at the Australian National University (ANU) and lead author of the study published today in Nature Astronomy. The quasar, called J0529-4351, is so far away from Earth that its light took over 12 billion years to reach us.

The matter being pulled in toward this black hole, in the form of a disc, emits so much energy that J0529-4351 is over 500 trillion times more luminous than the Sun [1].

All this light comes from a hot accretion disc that measures seven light-years in diameter — this must be the largest accretion disc in the Universe,

says ANU PhD student and co-author Samuel Lai. Seven light-years is about 15 000 times the distance from the Sun to the orbit of Neptune.

And, remarkably, this record-breaking quasar was hiding in plain sight.

It is a surprise that it has remained unknown until today, when we already know about a million less impressive quasars. It has literally been staring us in the face until now,

says co-author Christopher Onken, an astronomer at ANU. He added that this object showed up in images from the ESO Schmidt Southern Sky Survey dating back to 1980, but it was not recognised as a quasar until decades later.

Finding quasars requires precise observational data from large areas of the sky. The resulting datasets are so large, researchers often use machine-learning models to analyse them and tell quasars apart from other celestial objects. However, these models are trained on existing data, which limits the potential candidates to objects similar to those already known. If a new quasar is more luminous than any other previously observed, the programme might reject it and classify it instead as a star not too distant from Earth.

An automated analysis of data from the European Space Agency’s Gaia satellite passed over J0529-4351 for being too bright to be a quasar, suggesting it to be a star instead. The researchers identified it as a distant quasar last year using observations from the ANU 2.3-metre telescope at the Siding Spring Observatory in Australia. Discovering that it was the most luminous quasar ever observed, however, required a larger telescope and measurements from a more precise instrument. The X-shooter spectrograph on ESO’s VLT in the Chilean Atacama Desert provided the crucial data.

The fastest-growing black hole ever observed will also be a perfect target for the GRAVITY+ upgrade on ESO’s VLT Interferometer (VLTI), which is designed to accurately measure the mass of black holes, including those far away from Earth. Additionally, ESO’s Extremely Large Telescope (ELT), a 39-metre telescope under construction in the Chilean Atacama Desert, will make identifying and characterising such elusive objects even more feasible.

Finding and studying distant supermassive black holes could shed light on some of the mysteries of the early Universe, including how they and their host galaxies formed and evolved. But that’s not the only reason why Wolf searches for them.

“Personally, I simply like the chase,” he says. “For a few minutes a day, I get to feel like a child again, playing treasure hunt, and now I bring everything to the table that I have learned since.”

Notes

[1] A few years ago, NASA and the European Space Agency reported that the Hubble Space Telescope had discovered a quasar, J043947.08+163415.7, as bright as 600 trillion Suns. However, that quasar’s brightness was magnified by a ‘lensing’ galaxy, located between us and the distant quasar. The actual luminosity of J043947.08+163415.7 is estimated to be equivalent to about 11 trillion Suns (1 trillion is a million million: 1 000 000 000 000 or 10¹²).

Links

• Research paper
• Photos of the VLT
• Find out more about ESO’s Extremely Large Telescope on our dedicated website and press kit
• For journalists: subscribe to receive our releases under embargo in your language
• For scientists: got a story? Pitch your research

=== Amazon Ads ===

Celestron – NexStar 130SLT Computerized Telescope –
Compact and Portable –
Newtonian Reflector Optical Design –
SkyAlign Technology –
Computerized Hand Control –
130mm Aperture

====

For the Love of Mars:
A Human History of the Red Planet

A new report from the European Southern Observatory (ESO):

Missing link found:
Supernovae give rise to black holes or neutron stars

Astronomers have found a direct link between the explosive deaths of massive stars and the formation of the most compact and enigmatic objects in the Universe — black holes and neutron stars. With the help of the European Southern Observatory’s Very Large Telescope (ESO’s VLT) and ESO’s New Technology Telescope (NTT), two teams were able to observe the aftermath of a supernova explosion in a nearby galaxy, finding evidence for the mysterious compact object it left behind.

When massive stars reach the end of their lives, they collapse under their own gravity so rapidly that a violent explosion known as a supernova ensues. Astronomers believe that, after all the excitement of the explosion, what is left is the ultra-dense core, or compact remnant, of the star. Depending on how massive the star is, the compact remnant will be either a neutron star — an object so dense that a teaspoon of its material would weigh around a trillion kilograms here on Earth — or a black hole — an object from which nothing, not even light, can escape.

Astronomers have found many clues hinting at this chain of events in the past, such as finding a neutron star within the Crab Nebula, the gas cloud left behind when a star exploded nearly a thousand years ago. But they had never before seen this process happen in real time, meaning that direct evidence of a supernova leaving behind a compact remnant has remained elusive.

In our work, we establish such a direct link

says Ping Chen, a researcher at the Weizmann Institute of Science, Israel, and lead author of a study published today in Nature and presented at the 243rd American Astronomical Society meeting in New Orleans, USA.

The researchers’ lucky break came in May 2022, when South African amateur astronomer Berto Monard discovered the supernova SN 2022jli in the spiral arm of the nearby galaxy NGC 157, located 75 million light-years away. Two separate teams turned their attention to the aftermath of this explosion and found it to have a unique behaviour.

After the explosion, the brightness of most supernovae simply fades away with time; astronomers see a smooth, gradual decline in the explosion’s ‘light curve’. But SN 2022jli’s behaviour is very peculiar: as the overall brightness declines, it doesn’t do so smoothly, but instead oscillates up and down every 12 days or so.

In SN 2022jli’s data we see a repeating sequence of brightening and fading

says Thomas Moore, a doctoral student at Queen’s University Belfast, Northern Ireland, who led a study of the supernova published late last year in the Astrophysical Journal. Moore noted in his paper.

This is the first time that repeated periodic oscillations, over many cycles, have been detected in a supernova light curve

Both the Moore and Chen teams believe that the presence of more than one star in the SN 2022jli system could explain this behaviour. In fact, it’s not unusual for massive stars to be in orbit with a companion star in what is known as a binary system, and the star that caused SN 2022jli was no exception. What is remarkable about this system, however, is that the companion star appears to have survived the violent death of its partner and the two objects, the compact remnant and the companion, likely kept orbiting each other.

The data collected by the Moore team, which included observations with ESO’s NTT in Chile’s Atacama Desert, did not allow them to pin down exactly how the interaction between the two objects caused the highs and lows in the light curve. But the Chen team had additional observations. They found the same regular fluctuations in the system’s visible brightness that the Moore team had detected, and they also spotted periodic movements of hydrogen gas and bursts of gamma rays in the system. Their observations were made possible thanks to a fleet of instruments on the ground and in space, including X-shooter on ESO’s VLT, also located in Chile.

Putting all the clues together, the two teams generally agree that when the companion star interacted with the material thrown out during the supernova explosion, its hydrogen-rich atmosphere became puffier than usual. Then, as the compact object left behind after the explosion zipped through the companion’s atmosphere on its orbit, it would steal hydrogen gas, forming a hot disc of matter around itself. This periodic stealing of matter, or accretion, released lots of energy that was picked up as regular changes of brightness in the observations.

Even though the teams could not observe light coming from the compact object itself, they concluded that this energetic stealing can only be due to an unseen neutron star, or possibly a black hole, attracting matter from the companion star’s puffy atmosphere.

Our research is like solving a puzzle by gathering all possible evidence,” Chen says. “All these pieces lining up lead to the truth.”

With the presence of a black hole or neutron star confirmed, there is still plenty to unravel about this enigmatic system, including the exact nature of the compact object or what end could await this binary system. Next-generation telescopes such as ESO’s Extremely Large Telescope, scheduled to begin operation later this decade, will help with this, allowing astronomers to reveal unprecedented details of this unique system.

Links

• Chen et al. paper
• Moore et al. paper
• Photos of the VLT
• Photos of the NTT
• Find out more about ESO’s Extremely Large Telescope on our dedicated website and press kit
• For journalists: subscribe to receive our releases under embargo in your language
• For scientists: got a story? Pitch your research

=== Amazon Ads ===

Celestron – NexStar 130SLT Computerized Telescope –
Compact and Portable –
Newtonian Reflector Optical Design –
SkyAlign Technology –
Computerized Hand Control –
130mm Aperture

====

For the Love of Mars:
A Human History of the Red Planet