Category Archives: Space Science

ESO: Five exoplanets found locked in a rhythmic dance

The latest report from the European Southern Observatory (ESO):

Puzzling six-exoplanet system with rhythmic movement
challenges theories of how planets form

This artist’s impression shows the view from the planet in the TOI-178 system found orbiting furthest from the star. New research by Adrien Leleu and his colleagues with several telescopes, including ESO’s Very Large Telescope, has revealed that the system boasts six exoplanets and that all but the one closest to the star are locked in a rare rhythm as they move in their orbits.  But while the orbital motion in this system is in harmony, the physical properties of the planets are more disorderly, with significant variations in density from planet to planet. This contrast challenges astronomers’ understanding of how planets form and evolve. This artist’s impression is based on the known physical parameters for the planets and the star seen, and uses a vast database of objects in the Universe.Credits: ESO

Using a combination of telescopes, including the Very Large Telescope of the European Southern Observatory (ESO’s VLT), astronomers have revealed a system consisting of six exoplanets, five of which are locked in a rare rhythm around their central star. The researchers believe the system could provide important clues about how planets, including those in the Solar System, form and evolve.

The first time the team observed TOI-178, a star some 200 light-years away in the constellation of Sculptor, they thought they had spotted two planets going around it in the same orbit. However, a closer look revealed something entirely different.

“Through further observations we realised that there were not two planets orbiting the star at roughly the same distance from it, but rather multiple planets in a very special configuration,”

says Adrien Leleu from the Université de Genève and the University of Bern, Switzerland, who led a new study of the system published today in Astronomy & Astrophysics.

The new research has revealed that the system boasts six exoplanets and that all but the one closest to the star are locked in a rhythmic dance as they move in their orbits. In other words, they are in resonance. This means that there are patterns that repeat themselves as the planets go around the star, with some planets aligning every few orbits. A similar resonance is observed in the orbits of three of Jupiter’s moons: Io, Europa and Ganymede. Io, the closest of the three to Jupiter, completes four full orbits around Jupiter for every orbit that Ganymede, the furthest away, makes, and two full orbits for every orbit Europa makes.

The five outer exoplanets of the TOI-178 system follow a much more complex chain of resonance, one of the longest yet discovered in a system of planets. While the three Jupiter moons are in a 4:2:1 resonance, the five outer planets in the TOI-178 system follow a 18:9:6:4:3 chain: while the second planet from the star (the first in the resonance chain) completes 18 orbits, the third planet from the star (second in the chain) completes 9 orbits, and so on. In fact, the scientists initially only found five planets in the system, but by following this resonant rhythm they calculated where in its orbit an additional planet would be when they next had a window to observe the system.

More than just an orbital curiosity, this dance of resonant planets provides clues about the system’s past.

“The orbits in this system are very well ordered, which tells us that this system has evolved quite gently since its birth,”

explains co-author Yann Alibert from the University of Bern. If the system had been significantly disturbed earlier in its life, for example by a giant impact, this fragile configuration of orbits would not have survived.

Disorder in the rhythmic system

But even if the arrangement of the orbits is neat and well-ordered, the densities of the planets

“are much more disorderly,” says Nathan Hara from the Université de Genève, Switzerland, who was also involved in the study. “It appears there is a planet as dense as the Earth right next to a very fluffy planet with half the density of Neptune, followed by a planet with the density of Neptune. It is not what we are used to.”

In our Solar System, for example, the planets are neatly arranged, with the rocky, denser planets closer to the central star and the fluffy, low-density gas planets farther out.

“This contrast between the rhythmic harmony of the orbital motion and the disorderly densities certainly challenges our understanding of the formation and evolution of planetary systems,”

says Leleu.

Combining techniques

To investigate the system’s unusual architecture, the team used data from the European Space Agency’s CHEOPS satellite, alongside the ground-based ESPRESSO instrument on ESO’s VLT and the NGTS and SPECULOOS, both sited at ESO’s Paranal Observatory in Chile. Since exoplanets are extremely tricky to spot directly with telescopes, astronomers must instead rely on other techniques to detect them. The main methods used are imaging transits — observing the light emitted by the central star, which dims as an exoplanet passes in front of it when observed from the Earth — and radial velocities — observing the star’s light spectrum for small signs of wobbles which happen as the exoplanets move in their orbits. The team used both methods to observe the system: CHEOPS, NGTS and SPECULOOS for transits and ESPRESSO for radial velocities.

By combining the two techniques, astronomers were able to gather key information about the system and its planets, which orbit their central star much closer and much faster than the Earth orbits the Sun. The fastest (the innermost planet) completes an orbit in just a couple of days, while the slowest takes about ten times longer. The six planets have sizes ranging from about one to about three times the size of Earth, while their masses are 1.5 to 30 times the mass of Earth. Some of the planets are rocky, but larger than Earth — these planets are known as Super-Earths. Others are gas planets, like the outer planets in our Solar System, but they are much smaller — these are nicknamed Mini-Neptunes.

Although none of the six exoplanets found lies in the star’s habitable zone, the researchers suggest that, by continuing the resonance chain, they might find additional planets that could exist in or very close to this zone. ESO’s Extremely Large Telescope (ELT), which is set to begin operating this decade, will be able to directly image rocky exoplanets in a star’s habitable zone and even characterise their atmospheres, presenting an opportunity to get to know systems like TOI-178 in even greater detail.

More information

This research was presented in the paper “Six transiting planets and a chain of Laplace resonances in TOI-178” to appear in Astronomy & Astrophysics (doi: 10.1051/0004-6361/202039767).

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Stellaris: People of the Stars

 

ESO: Telescopes observe final moments of a star eaten by a black hole

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

Death by Spaghettification:
ESO Telescopes Record Last Moments of Star Devoured by a Black Hole

This illustration depicts a star (in the foreground) experiencing spaghettification as it’s sucked in by a supermassive black hole (in the background) during a ‘tidal disruption event’. In a new study, done with the help of ESO’s Very Large Telescope and ESO’s New Technology Telescope, a team of astronomers found that when a black hole devours a star, it can launch a powerful blast of material outwards.Credits ESO

Using telescopes from the European Southern Observatory (ESO) and other organisations around the world, astronomers have spotted a rare blast of light from a star being ripped apart by a supermassive black hole. The phenomenon, known as a tidal disruption event, is the closest such flare recorded to date at just over 215 million light-years from Earth, and has been studied in unprecedented detail. The research is published today in Monthly Notices of the Royal Astronomical Society.

“The idea of a black hole ‘sucking in’ a nearby star sounds like science fiction. But this is exactly what happens in a tidal disruption event,”

says Matt Nicholl, a lecturer and Royal Astronomical Society research fellow at the University of Birmingham, UK, and the lead author of the new study. But these tidal disruption events, where a star experiences what’s known as spaghettification as it’s sucked in by a black hole, are rare and not always easy to study. The team of researchers pointed ESO’s Very Large Telescope (VLT) and ESO’s New Technology Telescope (NTT) at a new flash of light that occurred last year close to a supermassive black hole, to investigate in detail what happens when a star is devoured by such a monster.

Astronomers know what should happen in theory.

“When an unlucky star wanders too close to a supermassive black hole in the centre of a galaxy, the extreme gravitational pull of the black hole shreds the star into thin streams of material,”

explains study author Thomas Wevers, an ESO Fellow in Santiago, Chile, who was at the Institute of Astronomy, University of Cambridge, UK, when he conducted the work. As some of the thin strands of stellar material fall into the black hole during this spaghettification process, a bright flare of energy is released, which astronomers can detect.

Although powerful and bright, up to now astronomers have had trouble investigating this burst of light, which is often obscured by a curtain of dust and debris. Only now have astronomers been able to shed light on the origin of this curtain.

“We found that, when a black hole devours a star, it can launch a powerful blast of material outwards that obstructs our view,” 

explains Samantha Oates, also at the University of Birmingham. This happens because the energy released as the black hole eats up stellar material propels the star’s debris outwards.

The discovery was possible because the tidal disruption event the team studied, AT2019qiz, was found just a short time after the star was ripped apart.

“Because we caught it early, we could actually see the curtain of dust and debris being drawn up as the black hole launched a powerful outflow of material with velocities up to 10 000 km/s,” says Kate Alexander, NASA Einstein Fellow at Northwestern University in the US. “This unique ‘peek behind the curtain’ provided the first opportunity to pinpoint the origin of the obscuring material and follow in real time how it engulfs the black hole.”

The team carried out observations of AT2019qiz, located in a spiral galaxy in the constellation of Eridanus, over a 6-month period as the flare grew in luminosity and then faded away.

“Several sky surveys discovered emission from the new tidal disruption event very quickly after the star was ripped apart,” says Wevers. “We immediately pointed a suite of ground-based and space telescopes in that direction to see how the light was produced.”

Multiple observations of the event were taken over the following months with facilities that included X-shooter and EFOSC2, powerful instruments on ESO’s VLT and ESO’s NTT, which are situated in Chile. The prompt and extensive observations in ultraviolet, optical, X-ray and radio light revealed, for the first time, a direct connection between the material flowing out from the star and the bright flare emitted as it is devoured by the black hole.

“The observations showed that the star had roughly the same mass as our own Sun, and that it lost about half of that to the monster black hole, which is over a million times more massive,”

says Nicholl, who is also a visiting researcher at the University of Edinburgh.

The research helps us better understand supermassive black holes and how matter behaves in the extreme gravity environments around them. The team say AT2019qiz could even act as a ‘Rosetta stone’ for interpreting future observations of tidal disruption events. ESO’s Extremely Large Telescope (ELT), planned to start operating this decade, will enable researchers to detect increasingly fainter and faster evolving tidal disruption events, to solve further mysteries of black hole physics.

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Imagined Life: A Speculative Scientific Journey among the Exoplanets
in Search of Intelligent Aliens, Ice Creatures, and Supergravity Animals

 

ESO: Planetary disc warped and distorted in three star system

A new report from ESO (European Southern Observatory):

New Observations Show Planet-forming Disc Torn Apart
by its Three Central Stars

ALMA, in which ESO is a partner, and the SPHERE instrument on ESO’s Very Large Telescope have imaged GW Orionis, a triple star system with a peculiar inner region. The new observations revealed that this object has a warped planet-forming disc with a misaligned ring. In particular, the SPHERE image (right panel) allowed astronomers to see, for the first time, the shadow that this ring casts on the rest of the disc. This helped them figure out the 3D shape of the ring and the overall disc. The left panel shows an artistic impression of the inner region of the disc, including the ring, which is based on the 3D shape reconstructed by the team.

A team of astronomers have identified the first direct evidence that groups of stars can tear apart their planet-forming disc, leaving it warped and with tilted rings. This new research suggests exotic planets, not unlike Tatooine in Star Wars, may form in inclined rings in bent discs around multiple stars. The results were made possible thanks to observations with the European Southern Observatory’s Very Large Telescope (ESO’s VLT) and the Atacama Large Millimeter/submillimeter Array (ALMA).

Our Solar System is remarkably flat, with the planets all orbiting in the same plane. But this is not always the case, especially for planet-forming discs around multiple stars, like the object of the new study: GW Orionis. This system, located just over 1300 light-years away in the constellation of Orion, has three stars and a deformed, broken-apart disc surrounding them.

Our images reveal an extreme case where the disc is not flat at all, but is warped and has a misaligned ring that has broken away from the disc,

says Stefan Kraus, a professor of astrophysics at the University of Exeter in the UK who led the research published today in the journal Science. The misaligned ring is located in the inner part of the disc, close to the three stars.

The new research also reveals that this inner ring contains 30 Earth-masses of dust, which could be enough to form planets.

Any planets formed within the misaligned ring will orbit the star on highly oblique orbits and we predict that many planets on oblique, wide-separation orbits will be discovered in future planet imaging campaigns, for instance with the ELT,

says team member Alexander Kreplin of the University of Exeter, referring to ESO’s Extremely Large Telescope, which is planned to start operating later this decade. Since more than half the stars in the sky are born with one or more companions, this raises an exciting prospect: there could be an unknown population of exoplanets that orbit their stars on very inclined and distant orbits.

ALMA, in which ESO is a partner, and the SPHERE instrument on ESO’s Very Large Telescope have imaged GW Orionis, a triple star system with a peculiar inner region. Unlike the flat planet-forming discs we see around many stars, GW Orionis features a warped disc, deformed by the movements of the three stars at its centre. The ALMA image (left) shows the disc’s ringed structure, with the innermost ring separated from the rest of the disc. The SPHERE observations (right) allowed astronomers to see for the first time the shadow of this innermost ring on the rest of the disc, which made it possible for them to reconstruct its warped shape.

To reach these conclusions, the team observed GW Orionis for over 11 years. Starting in 2008, they used the AMBER and later the GRAVITY instruments on ESO’s VLT Interferometer in Chile, which combines the light from different VLT telescopes, to study the gravitational dance of the three stars in the system and map their orbits.

We found that the three stars do not orbit in the same plane, but their orbits are misaligned with respect to each other and with respect to the disc,

says Alison Young of the Universities of Exeter and Leicester and a member of the team.

They also observed the system with the SPHERE instrument on ESO’s VLT and with ALMA, in which ESO is a partner, and were able to image the inner ring and confirm its misalignment. ESO’s SPHERE also allowed them to see, for the first time, the shadow that this ring casts on the rest of the disc. This helped them figure out the 3D shape of the ring and the overall disc.

The international team, which includes researchers from the UK, Belgium, Chile, France and the US, then combined their exhaustive observations with computer simulations to understand what had happened to the system. For the first time, they were able to clearly link the observed misalignments to the theoretical “disc-tearing effect”, which suggests that the conflicting gravitational pull of stars in different planes can warp and break their discs.

Their simulations showed that the misalignment in the orbits of the three stars could cause the disc around them to break into distinct rings, which is exactly what they see in their observations. The observed shape of the inner ring also matches predictions from numerical simulations on how the disc would tear.

ALMA, in which ESO is a partner, and the SPHERE instrument on ESO’s Very Large Telescope have imaged GW Orionis, a triple star system with a peculiar inner region. Unlike the flat planet-forming discs we see around many stars, GW Orionis features a warped disc, deformed by the movements of the three stars at its centre. This composite image shows both the ALMA and SPHERE observations of the disc.  The ALMA image shows the disc’s ringed structure, with the innermost ring (part of which is visible as an oblong dot at the very centre of the image) separated from the rest of the disc. The SPHERE observations allowed astronomers to see for the first time the shadow of this innermost ring on the rest of the disc, which made it possible for them to reconstruct its warped shape.

Interestingly, another team who studied the same system using ALMA believe another ingredient is needed to understand the system.

We think that the presence of a planet between these rings is needed to explain why the disc tore apart,

says Jiaqing Bi of the University of Victoria in Canada who led a study of GW Orionis published in The Astrophysical Journal Letters in May this year. His team identified three dust rings in the ALMA observations, with the outermost ring being the largest ever observed in planet-forming discs.

Future observations with ESO’s ELT and other telescopes may help astronomers fully unravel the nature of GW Orionis and reveal young planets forming around its three stars.

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The Planet Factory:
Exoplanets and the Search for a Second Earth

Video: Launch of the HOPE Mars Mission [Updated]

7:58  pm EDT: The upper stage firing went as planned and the probe was successfully deployed. Communications with the vehicle have been established and the solar panels were deployed. The spacecraft’s next job is to use its attitude thrusters to orient itself so as to maximize power generation from the sun. The probe will reach Mars next February.  After going into orbit, the spacecraft’s instruments will study the atmosphere and weather on the Red Planet.

6:31  pm EDT: The launch has succeeded so far in reaching low earth orbit. The upper stage with the probe is now in a coast period before the stage will fire its engine for 4 minutes to send the Hope probe on its route to Mars. The stage will then separate from the probe soon after the engine boost ends. The firing should start at around 6:54 pm EDT (22:54 UTC).

The countdown is nearing liftoff for the  launch of the UAE Hope orbiter mission to Mars on a Japanese H-IIA rocket from the Tenaghashima Space Centre in Japan. Below is the webcast.

5:35 pm EDT: Currently all systems are green for liftoff at 5:38 pm EDT.

Updates and background info:

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Xtronaut: The Game of Solar System Exploration

ESO: VLT sees evidence of a planet forming in disc of dust and gas around star AB Aurigae

The latest news from ESO (European Southern Observatory):

ESO Telescope Sees Signs of Planet Birth
The Twist Marks the Spot

This image shows the disc around the young AB Aurigae star, where ESO’s Very Large Telescope (VLT) has spotted signs of planet birth. Close to the centre of the image, in the inner region of the disc, we see the ‘twist’ (in very bright yellow) that scientists believe marks the spot where a planet is forming. This twist lies at about the same distance from the AB Aurigae star as Neptune from the Sun.
The image was obtained with the VLT’s SPHERE instrument in polarised light.

Observations made with the European Southern Observatory’s Very Large Telescope (ESO’s VLT) have revealed the telltale signs of a star system being born. Around the young star AB Aurigae lies a dense disc of dust and gas in which astronomers have spotted a prominent spiral structure with a ‘twist’ that marks the site where a planet may be forming. The observed feature could be the first direct evidence of a baby planet coming into existence.

“Thousands of exoplanets have been identified so far, but little is known about how they form,”

says Anthony Boccaletti who led the study from the Observatoire de Paris, PSL University, France. Astronomers know planets are born in dusty discs surrounding young stars, like AB Aurigae, as cold gas and dust clump together. The new observations with ESO’s VLT, published in Astronomy & Astrophysics, provide crucial clues to help scientists better understand this process.

“We need to observe very young systems to really capture the moment when planets form,”

says Boccaletti. But until now astronomers had been unable to take sufficiently sharp and deep images of these young discs to find the ‘twist’ that marks the spot where a baby planet may be coming to existence.

The new images feature a stunning spiral of dust and gas around AB Aurigae, located 520 light-years away from Earth in the constellation of Auriga (The Charioteer). Spirals of this type signal the presence of baby planets, which ‘kick’ the gas, creating

“disturbances in the disc in the form of a wave, somewhat like the wake of a boat on a lake,”

explains Emmanuel Di Folco of the Astrophysics Laboratory of Bordeaux (LAB), France, who also participated in the study. As the planet rotates around the central star, this wave gets shaped into a spiral arm. The very bright yellow ‘twist’ region close to the centre of the new AB Aurigae image, which lies at about the same distance from the star as Neptune from the Sun, is one of these disturbance sites where the team believe a planet is being made.

The images of the AB Aurigae system showing the disc around it. The image on the right is a zoomed-in version of the area indicated by a red square on the image on the left. It shows the inner region of the disc, including the very-bright-yellow ‘twist’ (circled in white) that scientists believe marks the spot where a planet is forming. This twist lies at about the same distance from the AB Aurigae star as Neptune from the Sun. The blue circle represents the size of the orbit of Neptune. The images were obtained with the SPHERE instrument on ESO’s Very Large Telescope in polarised light.

Observations of the AB Aurigae system made a few years ago with the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner, provided the first hints of ongoing planet formation around the star. In the ALMA images, scientists spotted two spiral arms of gas close to the star, lying within the disc’s inner region. Then, in 2019 and early 2020, Boccaletti and a team of astronomers from France, Taiwan, the US and Belgium set out to capture a clearer picture by turning the SPHERE instrument on ESO’s VLT in Chile toward the star. The SPHERE images are the deepest images of the AB Aurigae system obtained to date.

With SPHERE’s powerful imaging system, astronomers could see the fainter light from small dust grains and emissions coming from the inner disc. They confirmed the presence of the spiral arms first detected by ALMA and also spotted another remarkable feature, a ‘twist’, that points to the presence of ongoing planet formation in the disc.

“The twist is expected from some theoretical models of planet formation,”

says co-author Anne Dutrey, also at LAB.

“It corresponds to the connection of two spirals  — one winding inwards of the planet’s orbit, the other expanding outwards — which join at the planet location. They allow gas and dust from the disc to accrete onto the forming planet and make it grow.”

ESO is constructing the 39-metre Extremely Large Telescope, which will draw on the cutting-edge work of ALMA and SPHERE to study extrasolar worlds. As Boccaletti explains, this powerful telescope will allow astronomers to get even more detailed views of planets in the making.

“We should be able to see directly and more precisely how the dynamics of the gas contributes to the formation of planets,”

he concludes.

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Fire in the Sky:
Cosmic Collisions, Killer Asteroids, and
the Race to Defend Earth