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.

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Astronomers Directly Image Debris Disk and find a Jupiter-Sized Planet Orbiting a Sunlike Star

Astronomers with the SHINE collabortion observed a debris disk containing a Super-Jupiter around a young star. Credit: ALMA (ESO/NAOJ/NRAO); M. Weiss (NRAO/AUI/NSF)

According to the most widely-accepted theory, planetary systems form from large clouds of dust and gas that form disks around young stars. Over time, these disks accrete to create planets of varying size, composition, and distance from their parent star. In the past few decades, observations in the mid- and far-infrared wavelengths have led to the discovery of debris disks around young stars (less than 100 million years old). This has allowed astronomers to study planetary systems in their early history, providing new insight into how systems form and evolve.

This includes the SpHere INfrared survey for Exoplanets (SHINE) consortium, an international team of astronomers dedicated to studying star systems in formation. Using the ESO’s Very Large Telescope (VLT), the SHINE collaboration recently directly imaged and characterized the debris disk of a nearby star (HD 114082) in visible and infrared wavelengths. Combined with data from NASA’s Transiting Exoplanet Space Satellite (TESS), they were able to detect a gas giant many times the size of Jupiter (a “Super-Jupiter”) embedded within the disk.

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An Asteroid has Been Discovered With Three Moons!

Planets aren’t the only celestial objects with moons – asteroids can have them too. They are usually other, smaller asteroids in orbit around a larger central one.  Now, a team of Thai and French astronomers found an asteroid system with three satellites.  The new four-body system makes complex gravitational problems like the three-body problem look simple by comparison.

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A 2nd Planet has been Confirmed for Proxima Centauri

An artist's illustration of the Proxima Centauri system. Proxima b in on the left, while Proxima C is on the right. Image Credit: Lorenzo Santinelli

Our closest stellar neighbour is Proxima Centauri, a small red dwarf star about 4.2 light years away from us. It’s the third member of the Alpha Centauri group, and even though it’s so close, it can’t be seen with the naked eye. In 2016 astronomers discovered a planet orbiting Proxima Centuari, named Proxima Centauri b. That planet was confirmed only a few days ago.

Now, astronomers have confirmed the existence of a second planet, Proxima Centauri c.

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This is an Actual Image of a Planet-Forming Disc in a Distant Star System

An image of AB Aurigae from the ESO's VLT and its SPHERE instrument, showing what scientists think is a baby planet forming. Image Credit: ESO/Boccaletti et al.

In 2017, astronomers used ALMA (Atacama Large Millimeter/sub-millimeter Array) to look at the star AB Aurigae. It’s a type of young star called a Herbig Ae star, and it’s less then 10 million years old. At that time, they found a dusty protoplanetary disk there, with tell-tale gaps indicating spiral arms.

Now they’ve taken another look, and found a very young planet forming there.

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Astronomers Might Have Imaged a Second Planet Around Nearby Proxima Centauri – and it Might Have a Huge Set of Rings

An artist's illustration of the Proxima Centauri system. Proxima b in on the left, while Proxima C is on the right. Image Credit: Lorenzo Santinelli

In 2016, astronomers working for the European Southern Observatory (ESO) confirmed the existence of a terrestrial planet around Earth’s closest stellar neighbor – Proxima Centauri. The discovery of this nearby extrasolar planet (Proxima b) caused no shortage of excitement because, in addition to being similar in size to Earth, it was found to orbit within the star’s habitable zone (HZ).

Thanks to an INAF-led team, a second exoplanet (a super-Earth) was found early this year around Proxima Centauri using the Radial Velocity Method. Based on the separation between the two planets, another INAF-led team attempted to observe this planet using the Direct Imaging Method. While not entirely successful, their observations raise the possibility that this planet has a system of rings around it, much like Saturn.

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New Images of the “Golf Ball” Asteroid Pallas

New images of Pallas reveal a "golf ball asteroid" landscape. Credit: MIT/Marsset et al.

In 1802, German astronomer Heinrich Olbers observed what he thought was a planet within the Main Asteroid Belt. In time, astronomers would come to name this body Pallas, an alternate name for the Greek warrior goddess Athena. The subsequent discovery of many more asteroids in the Main Belt would lead to Pallas being reclassified as a large asteroid, the third-largest in the Belt after Ceres and Vesta.

For centuries, astronomers have sought to get a better look at Pallas to learn more about its size, shape, and composition. As of the turn of the century, astronomers had come to conclude that it was an oblate spheroid (an elongated sphere). Thanks to a new study by an international team, the first detailed images of Pallas have finally been taken, which reveal that its shape is more akin to a “golf ball” – i.e. heavily dimpled.

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Asteroid Hygiea is Round Enough That it Could Qualify as a Dwarf Planet, the Smallest in the Solar System

A new SPHERE/VLT image of Hygiea, which could be the Solar System’s smallest dwarf planet yet. As an object in the main asteroid belt, Hygiea satisfies right away three of the four requirements to be classified as a dwarf planet: it orbits around the Sun, it is not a moon and, unlike a planet, it has not cleared the neighbourhood around its orbit. The final requirement is that it have enough mass that its own gravity pulls it into a roughly spherical shape. This is what VLT observations have now revealed about Hygiea.

Within the Main Asteroid Belt, there are a number of larger bodies that have defied traditional classification. The largest among them is Ceres, which is followed by Vesta, Pallas, and Hygeia. Until recently, Ceres was thought to be the only object in the Main Belt large enough to undergo hydrostatic equilibrium – where an object is sufficiently massive that its gravity causes it to collapse into a roughly spherical shape.

However, it now seems that there is another body in the Main Belt that has earned the designation of “dwarf planet”. Using data from the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument at the Very Large Telescope (VLT), an international team of astronomers found compelling evidence that Hygeia is actually round, making it the smallest dwarf planet in the Solar System.

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A double asteroid came uncomfortably close this weekend. Here’s what astronomers saw

The unique capabilities of the SPHERE instrument on ESO’s Very Large Telescope have enabled it to obtain the sharpest images of a double asteroid as it flew by Earth on 25 May. While this double asteroid was not itself a threatening object, scientists used the opportunity to rehearse the response to a hazardous Near-Earth Object (NEO), proving that ESO’s front-line technology could be critical in planetary defence. This artist’s impression shows both components of the double asteroid 1999 KW4 during its Earth fly-by.

On May 25th, 2019, a strange, double-asteroid (1999 KW4) flew past Earth at a distance and speed that is likely to make a lot of people nervous. As always, there was no danger, since the asteroid passed Earth at a minimum distance of 5.2 million km (3.23 million mi), over 15 times greater than the distance between Earth of the Moon, and its orbit is well-understood by scientists.

Because of this, flyby was the perfect opportunity for the International Asteroid Warning Network (IAWN) to conduct a cross-organizational observing campaign of the asteroid 1999 KW4 as it flew by Earth. The European Southern Observatory (ESO) took part in this campaign and managed to capture some images of the object using the Very Large Telescope (VLT).

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Look at This Fascinating Variety of Planet-Forming Disks Around Other Stars

This is just one of the spectacular images of dusky discs from the SPHERE instrument on ESO's Very Large Telescope. It shows the disc around the young star IM Lupi in finer detail than ever before. The collection of images shows the fascinating variety of shapes and sizes of discs. Image: ESO/H. Avenhaus et al./DARTT-S collaboration

The European Southern Observatory (ESO) has released a stunning collection of images of the circumstellar discs that surround young stars. The images were captured with the SPHERE (Spectro-Polarimetric High-contrast Exoplanet REsearch) instrument on the ESO’s Very Large Telescope (VLT) in Chile. We’ve been looking at images of circumstellar disks for quite some time, but this collection reveals the fascinating variety of shapes an sizes that these disks can take.

New images from the SPHERE instrument on ESO’s Very Large Telescope are revealing the dusty discs surrounding nearby young stars in greater detail than previously achieved. They show a bizarre variety of shapes, sizes and structures, including the likely effects of planets still in the process of forming. Image: ESO/H. Avenhaus et al./E. Sissa et al./DARTT-S and SHINE collaborations

We have a widely-accepted model of star formation supported by ample evidence, including images like these ones from the ESO. The model starts with a cloud of gas and dust called a giant molecular cloud. Within that cloud, a pocket of gas and dust begins to coalesce. Eventually, as gravity causes material to fall inward, the pocket becomes more massive, and exerts even more gravitational pull. More gas and dust continues to be drawn in.

The material that falls in also gives some angular momentum to the pocket, which causes rotation. Once enough material is accumulated, fusion ignites and a star is born. At that point, there is a proto-star inside the cloud, with unused gas and dust remaining in a rotating ring around the proto-star. That left over rotating ring is called a circumstellar disc, out of which planets eventually form.

There are other images of circumstellar discs, but they’ve been challenging to capture. To image any amount of detail in the disks requires blocking out the light of the star at the center of the disk. That’s where SPHERE comes in.

A detailed view of the SPHERE instrument and its main subsystems. SPHERE is installed on the ESO’s VLT and saw first light in 2014. Image: ESO

SPHERE was added to the ESO’s Very Large Telescope in 2014. It’s primary job is to directly image exoplanets, but it also has the ability to capture images of circumstellar discs. To do that, it separates two types of light: polarized, and non-polarized.

Light coming directly from a star—in these images, a young star still surrounded by a circumstellar disc—is non-polarized. But once that starlight is scattered by the material in the disk itself, the light becomes polarized. SPHERE, as its name suggests, is able to separate the two types of light and isolate just the light from the disk. That is how the instrument captures such fascinating images of the disks.

An edge-on view of the disc surrounding the star GSC 07396-00759. The disc extends from the lower-left to the upper-right and the central grey region shows where the star was masked out. Credit:
ESO/E. Sissa et al.

Ever since it became clear that exoplanets are not rare, and that most stars—maybe all stars—have planets orbiting them, understanding solar system formation has become a hot topic. The problem has been that we can’t really see it happening in real time. We can look at our own Solar System, and other fully formed ones, and make guesses about how they formed. But planet formation is hidden inside those circumstellar disss. Seeing into those disks is crucial to understanding the link between the properties of the disk itself and the planets that form in the system.

The discs imaged in this collection are mostly from a study called the DARTTS-S (Discs ARound T Tauri Stars with SPHERE) survey. T Tauri stars are young stars less than 10 million years old. At that age, planets are still in the process of forming. The stars range from 230 to 550 light-years away from Earth. In astronomical terms, that’s pretty close. But the blinding bright light of the stars still makes it very difficult to capture the faint light of the discs.

One of the images is not a T Tauri star and is not from the DARTTS-S study. The disc around the star GSC 07396-00759, in the image above, is actually from the SHINE (SpHere INfrared survey for Exoplanets) survey, though the images itself was captured with SPHERE. GSC 07396-00759 is a red star that’s part of a multiple star system that was part of the DARTTS-S study. The puzzling thing is that red star is the same age as the T TAURI star in the same system, but the ring around the red star is much more evolved. Why the two discs around two stars the same age are so different from each other in terms of time-scale and evolution is a puzzle, and is one of the reasons why astronomers want to study these discs much more closely.

We can study our own Solar System, and look at the positions and characteristics of the planets and the asteroid belt and Kuiper Belt. From that we can try to guess how it all formed, but our only chance to understand how it all came together is to look at other younger solar systems as they form.

The SPHERE instrument, and other future instruments like the James Webb Space Telescope, will allow us to look into the circumstellar discs around other stars, and to tease out the details of planetary formation. These new images from SPHERE are a tantalizing taste of the detail and variety we can expect to see.