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Unusually High CO Abundance of the First Active Interstellar Comet – Space Ref

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Status Report
From: arXiv.org e-Print archive
Posted: Wednesday, April 22, 2020

Cordiner, M. A., Milam, S. N., Biver, N., Bockelée-Morvan, D., Roth, N. X., Bergin, E. A., Jehin, E., Remijan, A. J., Charnley, S. B., Mumma, M. J., Boissier, J., Crovisier, J., Paganini, L., Kuan, Y.-J., Lis, D. C

Comets spend most of their lives at large distances from any star, during which time their interior compositions remain relatively unaltered. Cometary observations can therefore provide direct insight into the chemistry that occurred during their birth at the time of planet formation. To-date, there have been no confirmed observations of parent volatiles (gases released directly from the nucleus) of a comet from any planetary system other than our own. Here we present high-resolution, interferometric observations of 2I/Borisov, the first confirmed interstellar comet, obtained using the Atacama Large Millimeter/submillimeter Array (ALMA) on 15th-16th December 2019. Our observations reveal emission from hydrogen cyanide (HCN), and carbon monoxide (CO), coincident with the expected position of 2I/Borisov’s nucleus, with production rates Q(HCN)=(7.0±1.1)×1023 s−1 and Q(CO)=(4.4±0.7)×1026 s−1. While the HCN abundance relative to water (0.06-0.16%) appears similar to that of typical, previously observed comets in our Solar System, the abundance of CO (35-105%) is among the highest observed in any comet within 2~au of the Sun. This shows that 2I/Borisov must have formed in a relatively CO-rich environment – probably beyond the CO ice-line in the very cold, outer regions of a distant protoplanetary accretion disk, as part of a population of small, icy bodies analogous to our Solar System’s own proto-Kuiper Belt.

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

DOI: 10.1038/s41550-020-1087-2

Cite as: arXiv:2004.09586 [astro-ph.EP] (or arXiv:2004.09586v1 [astro-ph.EP] for this version)

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From: Martin Cordiner PhD [view email]

[v1] Mon, 20 Apr 2020 19:28:30 UTC (562 KB)

https://arxiv.org/abs/2004.09586

// end //

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

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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.

Young Herbig Ae stars like AB Aurigae are of great interest to astronomers. They’re so young they’re not main sequence stars yet, and they’re still surrounded by their circumstellar disk of gas and dust. And out of that gas and dust, young planets are forming.

The disk around AB Aurigae, which is over 500 light years away, has spiral arms that meet in a knot. Scientists believe that the knot is the precise point where a young planet is forming. A new study used the SPHERE (Spectro-Polarimetric High-contrast Exoplanet REsearch) instrument on the Very Large Telescope (VLT) to take a closer look at AB Aurigae and the planets developing inside its disk.

The new study is titled “Possible evidence of ongoing planet formation in AB Aurigae.” Lead author of the study is Anthony Boccaletti from the Observatoire de Paris, PSL University, France. The paper is published in the journal Astronomy and Astrophysics.

“Thousands of exoplanets have been identified so far, but little is known about how they form,” said lead author Boccaletti in a press release. Observing young, still-forming planets is a big deal in astronomy right now, but it’s difficult. The circumstellar disk around the star is difficult to see into, and even our best technology is barely up to the task.

Artist’s impression of circumstellar disk of debris around a distant star. These disk are common around younger stars, and they’re difficult to see into. Credit: NASA/JPL

The SPHERE instrument was critical to this work. It’s an advanced adaptive optics system, combined with a coronoagraph. It was developed to advance the study of exoplanets, with low-resolution spectrographic and polarimetric images. It images in both optical and infrared light. SPHERE allowed the team behind this study to focus on the earliest stages of planetary formation.

“We need to observe very young systems to really capture the moment when planets form,” said Boccaletti. That twisted knot where the spiral arms of AB Aurigae’s circumstellar disk meet is as close as we’ve come to capturing that moment.

These spirals indicate the birth of a baby planet. That’s because the planet’s mass has an effect on the less dense gas and dust in the disk. Essentially, the planet kicks the material in the disk, creating a visible wave: the spirals.

“The twist of the spiral is perfectly reproduced with a planet-driven density wave model when projection effects are accounted for.”

From the Study “Possible evidence of ongoing planet formation in AB Aurigae.”

According to Emmanuel Di Folco of the Astrophysics Laboratory of Bordeaux (LAB), France, who took part in this study, the young planets create “disturbances in the disc in the form of a wave, somewhat like the wake of a boat on a lake.” And as the young planet rotates around the central star, those disturbances become spiral arms.

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. Image Credit: ESO/Boccaletti et al, 2020
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. Image Credit: ESO/Boccaletti et al, 2020

In their paper the authors caution us that we’re still learning what goes on inside these circumstellar veils that surround young stars. We’re still in the early days of seeing into those structures, and they aren’t certain that this twist is a planet.

“SPHERE has delivered the deepest images ever obtained for AB Aur in scattered light. Among the many structures that are yet to be understood, we identified not only the inner spiral arms, but we also resolved a feature in the form of a twist in the eastern spiral at a separation of about 30 au.”

Are they certain it’s a planet? Not exactly, but the twist feature matches modelling. “The twist of the spiral is perfectly reproduced with a planet-driven density wave model when projection effects are accounted for,” the authors write.

Initial observations of AB Aurigae made with ALMA, but without SPHERE, showed the pair of spiral arms. But ALMA alone didn’t reveal as much information. It revealed tantalizing hints, though, that planets were forming.

ALMA image of the dust ring (red) and gaseous spirals (blue) of the circumstellar disk AB Aurigae reveal gaseous spiral arms inside a wide dust gap, providing a hint of planet formation. By ALMA (ESO/NAOJ/NRAO)/Tang et al. – https://www.almaobservatory.org/en/press-release/astronomers-found-spirals-inside-a-dust-gap-of-a-young-star-forming-disk/, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=87359440

Though ALMA is a powerful tool, SPHERE is even more powerful. It can see the very faint light from dust grains, and emissions that come from the inner disk. Astronomers were able to see the details in the spirals, and the “twist” at their center.

“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.”

The disk is an elaborate structure, and astronomers observed many other structures within it. Two of them were of particular interest, marked f1 and f2 in this image. Both of these are SPHERE images, each one with a different intensity threshold. Image Credit: Boccaletti et al, 2020.
The disk is an elaborate structure, and astronomers observed many other structures within it. Two of them were of particular interest, marked f1 and f2 in this image. Both of these are SPHERE images, each one with a different intensity threshold. Image Credit: Boccaletti et al, 2020.

There’s ample theory to support the birth of planets at the twist point. “In the early stage of planet formation, hydrodynamical simulations indicate that the accretion process generates at the planet location an inner and outer spiral pattern due to Lindblad resonances induced by disk-planet interactions,” the team writes.

But the observational evidence to back it all up has been difficult to come by. This study presents some of the best observations yet that back the theory up.

In their conclusion, the authors write “…the SPHERE observations of AB Aur in scattered light combined to the ALMA data in the thermal regime provide strong evidence that we are actually witnessing ongoing planet formation revealed by its associated spiral arms.”

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But it’s not proven yet. “Further observations would be required to confirm this result and to derive better mass estimates for potential planets in this location.”

Those further observations might not be too far in the future. The ESO’s Extremely Large Telescope (ELT) should see first light in 2025. With a 39 meter mirror, the ELT will be an enormous boost to our astronomical observing power.

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

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Stormy weather puts damper on SpaceX’s 1st astronaut launch – 95.7 News

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CAPE CANAVERAL, Fla. — Stormy weather is threatening to delay SpaceX’s first astronaut launch.

A SpaceX rocket is scheduled to blast off Wednesday afternoon from Kennedy Space Center, carrying a Dragon capsule with NASA astronauts Doug Hurley and Bob Behnken to the International Space Station. It will be the first time astronauts launch from Florida in nine years and a first for a private company.

The manager of NASA’s commercial crew program, Kathy Lueders, said everything was progressing well — at least on the ground.

“Now the only thing we need to do is figure out how to control the weather,” she said Monday evening as rain continued to drench the area. “We’re continuing to be vigilant and careful and make sure we do this right.”

Forecasters put the odds of acceptable launch weather at 40%. But that doesn’t include the conditions all the way up the U.S. and Canadian coasts and across the sea to Ireland — a complicated mix of measurements unique to the Dragon crew capsule.

The Dragon’s emergency escape system can kick in, if necessary, all the way to orbit. If that happens, the capsule will need relatively calm wind and seas in which to splash down.

SpaceX will have at least two recovery ships deployed off Florida, and NASA will have two military cargo planes ready to take off. Additional planes will be stationed in New York and England to assist with a potential water rescue, according to Lueders.

Hans Koenigsmann, a vice-president for SpaceX, said the launch control team will incorporate global weather patterns and models to determine whether it’s safe to launch.

“If the weather gods are working with us,” he said, liftoff will occur at 4:33 p.m. SpaceX has a split-second launch window.

The good news is that the tropical weather headed toward Cape Canaveral should be gone in a couple days, with conditions also improving up the Eastern Seaboard later in the week.

If SpaceX doesn’t launch Wednesday, its next attempt would be Saturday.

___

The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education. The AP is solely responsible for all content.

Marcia Dunn, The Associated Press

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Extremely rare 'cosmic ring of fire' discovered in the early universe – CNET

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The ring galaxy R5519 may have been created during a massive, catastrophic collision between two galaxies in the early universe.


James Josephides/Swinburne Astronomy Productions

A violent, catastrophic collision between two galaxies has given rise to an extremely rare ring galaxy, lurking some 11 billion light years from the Earth. The monstrous, donut-shaped galaxy is making stars in its huge ring at a rate 50 times faster than our home galaxy, earning it an ominous moniker Johnny and June Cash would surely dig: The cosmic “ring of fire.”

In a paper, published in the journal Nature Astronomy on Tuesday, an international team of scientists detail the ring galaxy R5519, discovered after scouring data from the Hubble Space telescope and the W.M. Keck observatory in Hawaii. Among almost 4,000 galaxies detected in the data sets, R5519 was one of the brightest and displayed a clear ring structure. So the team investigated further — and quickly realized they’d found something unusual. 

“It is very a curious object, one that we have never seen before,” says Tiantian Yuan, an astronomer at Swinburne University in Australia and first author on the study. “The gigantic hole in this galaxy was caused by a head-on collision with another galaxy.”  

Probing the features of R5519, Yuan and her team began picking up clues as to how it formed. They ruled out gravitational lensing or a galaxy merger for its unusual structure and nearby, they detected a companion galaxy — G5593. They suspect this cosmic neighbor is the “intruder” galaxy that may have collided with R5519 around 40 million years ago. 

The two galaxies must have smashed into each other pretty much head-on — a galactic bulls-eye — and it’s likely there was already a disk of stars present in R5519. As G5593 came swooping through the galaxy, it split the disk through the guts and a wave of stars expanded from the center, as seen in the GIF above.

“The collisional formation of ring galaxies requires a thin disk to be present in the ‘victim’ galaxy before the collision occurs,” said Kenneth Freeman, an astronomer at Australian National University and co-author on the paper, in a statement. 

If R5519 is caused by a huge collision, that would make it an extremely rare cosmic phenomena. Only one in every 10, 000 galaxies in the local universe are formed in such a way. Notably, the early universe was much more crowded so the belief was these kind of collisions may have been more common. Yuan suggests the data is telling a different story.

“Previously, people think we would find more of these collisional ring galaxies in the young universe, simply because there are more collisions back then,” she says. “We find that is not the case.”

There are still some “unsolved puzzles” about the ring of fire, Yuan says. “We do not know if this ring was a first ring after the collision or it was the second ring.” She’s obtained further data from W.M. Keck to resolve this issue.

Astronomers will have to gather more data to be certain the ring is caused by a collision, rather than through natural evolution. The authors of the paper write the imaging performed by NASA’s soon-to-be-launched (and recently-assembled) James Webb Space Telescope will be able to resolve any lingering questions. Yuan says she has already discovered another ring galaxy likely formed by a head-on collision — and this is a billion years older than the “ring of fire.”

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