Largest Oort Cloud Comet Ever Observed Reveals Its Secrets with ALMA’s Powerful Gaze

An artist rendition of comet C/2014 UN271, the largest known comet in the Oort Cloud
Credit: NSF/AUI/NSF NRAO/M.Weiss. Hi-Res File

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Giant comet’s molecular activity and chemistry detected at record distance

A team of astronomers has made a groundbreaking discovery by detecting molecular activity in comet C/2014 UN271 (Bernardinelli-Bernstein)—the largest and second most distantly active comet ever observed from the Oort Cloud. Using the powerful Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, researchers observed this giant comet while it was more than halfway to Neptune, at an astonishing distance of 16.6 times the distance between the Sun and Earth.

C/2014 UN271 is a true behemoth, measuring nearly 85 miles (140 km) across—more than 10 times the size of most known comets. Until now, little was known about how such cold, distant objects behave. The new observations revealed complex and evolving jets of carbon monoxide gas erupting from the comet’s nucleus, providing the first direct evidence of what drives its activity so far from the Sun.

“These measurements give us a look at how this enormous, icy world works,” said lead author Nathan Roth of American University and NASA Goddard Space Flight Center. “We’re seeing explosive outgassing patterns that raise new questions about how this comet will evolve as it continues its journey toward the inner solar system.”

The ALMA telescope observed C/2014 UN271 by capturing light from carbon monoxide gas in its atmosphere and heat (thermal emission) when the comet was still very far from the Sun. Thanks to ALMA’s high sensitivity and resolution, scientists could focus on the extremely faint signal from such a cold, distant object. Building on previous ALMA observations (Lellouch+2022, A&A, 659, L1) which first characterized the large nucleus size of UN271, these new findings measured the thermal signal to further calculate the comet’s size and the amount of dust surrounding its nucleus. Their values for the nucleus size and dust mass are in agreement with previous ALMA observations and confirm it as the largest Oort Cloud comet ever found. ALMA’s ability to precisely measure these signals made this study possible, offering a clearer picture of this distant, icy giant.

The discovery not only marks the first detection of molecular outgassing in this record-setting comet, but also offers a rare glimpse into the chemistry and dynamics of objects originating from the farthest reaches of our solar system. As C/2014 UN271 approaches the Sun, scientists anticipate that more frozen gases will begin to vaporize, revealing even more about the comet’s primitive makeup and the early solar system. Such discoveries help answer fundamental questions about where Earth and its water came from, and how life-friendly environments might form elsewhere.

Source: National Radio Astronomy Observatory (NRAO)/News

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About NRAO

The National Radio Astronomy Observatory (NRAO) is a facility of the U.S. National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

About ALMA

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Southern Observatory (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science and Technology Council (NSTC) in Taiwan and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

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Finding, Tracking and Characterizing Asteroids

Top-down view of the Solar System showing the position on August 9, 2024 UTC of all asteroids and comets detected by NEOWISE during the Reactivation Mission. The blue circles and points indicate the orbits and locations of Mercury, Venus and Mars. The Earth and its orbit are shown in cyan. Filled gray circles are Main Belt asteroids, filled green circles are Near Earth asteroids and the filled yellow squares are comets. The white points indicate the objects NEOWISE detected during the last week of surveying. The tick marks on the x and y axes are in increments of 1 AU. This animation shows how solar system object detections accumulated over the course of the survey. The white points show the new detections from each successive run of the WISE Moving Object Pipeline System, and illustrate how the NEOWISE scan longituded progress around the sky.

The Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) and IPAC at the California Institute of Technology announce the NEOWISE Final Data Release.

The Final Data Release includes data acquired during the eleventh year of the NEOWISE Reactivation mission (Mainzer et al. 2014, ApJ, 792, 30), 13 December 2023 to 1 August 2024. These data are combined with data from the first ten years of NEOWISE mission into a single archive that contains ~26.9 million sets of 3.4 and 4.6 micron images and a database of ~199 billion source detections extracted from those images.

NEOWISE scanned the sky over twenty-one complete times during its 10.6 years of survey operations, with approximately six months between survey passes. Twelve or more independent exposures are made on each point of the sky during each survey epoch making the NEOWISE archive a time-domain resource for extracting multiple, independent thermal flux and position measurements of solar system small bodies and background galactic and extragalactic sources.

A guide to the NEOWISE data release, data access instructions, and supporting documentation are available at http://wise2.ipac.caltech.edu/docs/release/neowise. Access to the NEOWISE data products is available via the on-line and API services of the NASA/IPAC Infrared Science Archive (IRSA) at https://irsa.ipac.caltech.edu.

NEOWISE is a joint project of the Jet Propulsion Laboratory/California Institute of Technology and the University of California, Los Angeles, funded by the National Aeronautics and Space Administration Planetary Science Division.

NEOWISE: Mapping the Inner Solar System

This top-down view of the Solar System shows the positions of all asteroids and comets detected by NEOWISE during the Reactivation Mission, which concluded operations on August 8, 2024. The blue circles and points indicate the orbits and locations of Mercury, Venus and Mars. The Earth and its orbit are shown in cyan. Filled gray circles are Main Belt asteroids, filled green circles are Near Earth asteroids and the filled yellow squares are comets. The white points indicate the objects NEOWISE detected during the last week of surveying. The tick marks on the x and y axes are in increments of 1 AU. This animation shows how solar system object detections accumulated over the course of the survey. The white points show the new detections from each successive run of the WISE Moving Object Pipeline System, and illustrate how the NEOWISE scan longituded progress around the sky. Credit: Tommy Grav (Univ. of Arizona)

Source: NEOWISE/News

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NASA's Webb Reveals Unusual Jets of Volatile Gas from Icy Centaur 29P

Centaur 29P Outgassing (Artist's Concept)
Credits: Artwork: NASA, ESA, CSA, Leah Hustak (STScI)

Centaur 29P Outgassing (NIRSpec)
Credits: Illustration: NASA, ESA, CSA, Leah Hustak (STScI), Sara Faggi (NASA-GSFC, American University)

Centaur 29P Outgassing (Artist's Concept)

This is an animation portraying the outgassing activity of Centaur 29P/Schwassmann-Wachmann 1 based on data gathered by NASA’s James Webb Space Telescope’s NIRSpec (Near-Infrared Spectrograph) instrument. Centaur 29P is one of the most active objects in the outer solar system, undergoing quasi-periodic outbursts in brightness.

The video begins by zooming in for a closer view of an artist’s concept of Centaur 29P. The scene is overlaid with graphics that help define the four different jets of gas before the centaur is rotated so the object can be examined from different angles. Credits: Video: NASA, ESA, CSA, Leah Hustak (STScI). Video Youtube

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Inspired by the half-human, half-horse creatures that are part of Ancient Greek mythology, the field of astronomy has its own kind of centaurs: distant objects orbiting the Sun between Jupiter and Neptune. NASA’s James Webb Space Telescope has mapped the gases spewing from one of these objects, suggesting a varied composition and providing new insights into the formation and evolution of the solar system.

Centaurs are former trans-Neptunian objects that have been moved inside Neptune’s orbit by subtle gravitational influences of the planets in the last few million years, and may eventually become short-period comets. They are “hybrid” in the sense that they are in a transitional stage of their orbital evolution: Many share characteristics with both trans-Neptunian objects (from the cold Kuiper Belt reservoir), and short-period comets, which are objects highly altered by repeated close passages around the Sun.

Since these small icy bodies are in an orbital transitional phase, they have been the subject of various studies as scientists seek to understand their composition, the reasons behind their outgassing activity — the loss of their ices that lie underneath the surface — and how they serve as a link between primordial icy bodies in the outer solar system and evolved comets.

A team of scientists recently used Webb’s NIRSpec (Near-Infrared Spectrograph) instrument to obtain data on Centaur 29P/Schwassmann-Wachmann 1 (29P for short), an object that is known for its highly active and quasi-periodic outbursts. It varies in intensity every six to eight weeks, making it one of the most active objects in the outer solar system. They discovered a new jet of carbon monoxide (CO) and previously unseen jets of carbon dioxide (CO2) gas, which give new clues to the nature of the centaur’s nucleus. “Centaurs can be considered as some of the leftovers of our planetary system’s formation. Because they are stored at very cold temperatures, they preserve information about volatiles in the early stages of the solar system,” said Sara Faggi of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and American University in Washington, DC, lead author of the study. “Webb really opened the door to a resolution and sensitivity that was impressive to us — when we saw the data for the first time, we were excited. We had never seen anything like this.”

Webb and the Jets

Centaurs’ distant orbits and consequent faintness have inhibited detailed observations in the past. Data from prior radio wavelength observations of Centaur 29P showed a jet pointed generally toward the Sun (and Earth) composed of CO. Webb detected this face-on jet and, thanks to its large mirror and infrared capabilities, also sensitively searched for many other chemicals, including water (H2O) and CO2. The latter is one of the main forms in which carbon is stored across the solar system. No clear indication of water vapor was detected in the atmosphere of 29P, which could be related to the extremely cold temperatures present in this body.

The telescope’s unique imaging and spectral data revealed never-before-seen features: two jets of CO2 emanating in the north and south directions, and another jet of CO pointing toward the north. This was the first definitive detection of CO2 in Centaur 29P.

Based on the data gathered by Webb, the team created a 3D model of the jets to understand their orientation and origin. They found through their modeling efforts that the jets were emitted from different regions on the centaur’s nucleus, even though the nucleus itself cannot be resolved by Webb. The jets’ angles suggest the possibility that the nucleus may be an aggregate of distinct objects with different compositions; however, other scenarios can’t yet be excluded.

“The fact that Centaur 29P has such dramatic differences in the abundance of CO and CO2 across its surface suggests that 29P may be made of several pieces,” said Geronimo Villanueva, co-author of the study at NASA Goddard. “Maybe two pieces coalesced together and made this centaur, which is a mixture between very different bodies that underwent separate formation pathways. It challenges our ideas about how primordial objects are created and stored in the Kuiper Belt.”

Persisting Unanswered Questions (For Now)

The reasons for Centaur 29P’s bursts in brightness, and the mechanisms behind its outgassing activity through the CO and CO2 jets, continue to be two major areas of interest that require further investigation. In the case of comets, scientists know that their jets are often driven by the outgassing of water. However, because of the centaurs’ location, they are too cold for water ice to sublimate, meaning that the nature of their outgassing activity differs from comets. “We only had time to look at this object once, like a snapshot in time,” said Adam McKay, a co-author of the study at Appalachian State University in Boone, North Carolina. “I’d like to go back and look at Centaur 29P over a much longer period of time. Do the jets always have that orientation? Is there perhaps another carbon monoxide jet that turns on at a different point in the rotation period? Looking at these jets over time would give us much better insights into what is driving these outbursts.” The team is hopeful that as they increase their understanding of Centaur 29P, they can apply the same techniques to other centaurs. By improving the astronomical community’s collective knowledge of centaurs, we can simultaneously better our understanding on the formation and evolution of our solar system.

These findings have been published in Nature.

The observations were taken as part of General Observer program 2416.

The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).

Source: NASA's James Webb Space Telescope/News

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About This Release

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Media Contact:

Abigail Major
Space Telescope Science Institute, Baltimore, Maryland

Christine Pulliam
Space Telescope Science Institute, Baltimore, Maryland

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Contact Us: Direct inquiries to the News Team.

Related Links and Documents

• The science paper by S. Faggi et al.

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NASA’s Webb Finds Water, and a New Mystery, in Rare Main Belt Comet

Artist's Concept of Comet 238P/Read
Credits: Illustration: NASA, ESA

Comet 238P/Read (NIRCam Image)
Credits: Image: NASA, ESA, CSA, Mike Kelley (UMD)
Image Processing: Henry Hsieh (PSI), Alyssa Pagan (STScI)

Comet Spectra Comparison
Credits: Illustration: NASA, ESA, CSA, Joseph Olmsted (STScI)

Release Images

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NASA’s James Webb Space Telescope has enabled another long-sought scientific breakthrough, this time for solar system scientists studying the origins of Earth’s abundant water. Using Webb’s NIRSpec (Near-Infrared Spectrograph) instrument, astronomers have confirmed gas – specifically water vapor – around a comet in the main asteroid belt for the first time, indicating that water ice from the primordial solar system can be preserved in that region. However, the successful detection of water comes with a new puzzle: unlike other comets, Comet 238P/Read had no detectable carbon dioxide.

“Our water-soaked world, teeming with life and unique in the universe as far as we know, is something of a mystery – we’re not sure how all this water got here,” said Stefanie Milam, Webb deputy project scientist for planetary science and a co-author on the study reporting the finding. “Understanding the history of water distribution in the solar system will help us to understand other planetary systems, and if they could be on their way to hosting an Earth-like planet,” she added.

Comet Read is a main belt comet – an object that resides in the main asteroid belt but which periodically displays a halo, or coma, and tail like a comet . Main belt comets themselves are a fairly new classification, and Comet Read was one of the original three comets used to establish the category. Before that, comets were understood to reside in the Kuiper Belt and Oort Cloud, beyond the orbit of Neptune, where their ices could be preserved farther from the Sun. Frozen material that vaporizes as they approach the Sun is what gives comets their distinctive coma and streaming tail, differentiating them from asteroids. Scientists have long speculated that water ice could be preserved in the warmer asteroid belt, inside the orbit of Jupiter, but definitive proof was elusive – until Webb.

“In the past, we’ve seen objects in the main belt with all the characteristics of comets, but only with this precise spectral data from Webb can we say yes, it’s definitely water ice that is creating that effect,” explained astronomer Michael Kelley of the University of Maryland, lead author of the study.

“With Webb’s observations of Comet Read, we can now demonstrate that water ice from the early solar system can be preserved in the asteroid belt,” Kelley said.

The missing carbon dioxide was a bigger surprise. Typically, carbon dioxide makes up about 10 percent of the volatile material in a comet that can be easily vaporized by the Sun’s heat. The science team presents two possible explanations for the lack of carbon dioxide. One possibility is that Comet Read had carbon dioxide when it formed but has lost that because of warm temperatures.

“Being in the asteroid belt for a long time could do it – carbon dioxide vaporizes more easily than water ice, and could percolate out over billions of years,” Kelley said. Alternatively, he said, Comet Read may have formed in a particularly warm pocket of the solar system, where no carbon dioxide was available.

The next step is taking the research beyond Comet Read to see how other main belt comets compare, says astronomer Heidi Hammel of the Association of Universities for Research in Astronomy (AURA), lead for Webb’s Guaranteed Time Observations for solar system objects and co-author of the study. “These objects in the asteroid belt are small and faint, and with Webb we can finally see what is going on with them and draw some conclusions. Do other main belt comets also lack carbon dioxide? Either way it will be exciting to find out,” Hammel said.

Co-author Milam imagines the possibilities of bringing the research even closer to home. “Now that Webb has confirmed there is water preserved as close as the asteroid belt, it would be fascinating to follow up on this discovery with a sample collection mission, and learn what else the main belt comets can tell us.”

The study is published in the journal Nature.

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About This Release

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Media Contact:

Leah Ramsay
Space Telescope Science Institute, Baltimore, Maryland

Christine Pulliam
Space Telescope Science Institute, Baltimore, Maryland

Science:

Mike Kelley (UMD)

Permissions:Content Use Policy

Contact Us: Direct inquiries to the News Team.

Related Links and Documents:

• The science paper by M. Kelley et al.
• The Planetary Science Institute press release

 

 Source: NASA's James Webb Space Telescope/News

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Hubble Confirms Largest Comet Nucleus Ever Seen

Comet C/2014 UN271 Nucleus

This sequence shows how the nucleus of Comet C/2014 UN271 (Bernardinelli-Bernstein) was isolated from a vast shell of dust and gas surrounding the solid icy nucleus. On the left is a photo of the comet taken by the NASA Hubble Space Telescope's Wide Field Camera 3 on January 8, 2022. A model of the coma (middle panel) was obtained by means of fitting the surface brightness profile assembled from the observed image on the left. This allowed for the coma to be subtracted, unveiling the point-like glow from the nucleus. Combined with radio telescope data, astronomers arrived at a precise measurement of the nucleus size. That's no small feat from something about 2 billion miles away. Though the nucleus is estimated to be as large as 85 miles across, it is so far away it cannot be resolved by Hubble. Its size is derived from its reflectivity as measured by Hubble. The nucleus is estimated to be as black as charcoal. The nucleus area is gleaned from radio observations. Credits: Science: NASA, ESA, Man-To Hui (Macau University of Science and Technology), David Jewitt (UCLA) Image Processing: Alyssa Pagan (STScI). Release Images

Comparison of Comet Nucleus Sizes

This diagram compares the size of the icy, solid nucleus of comet C/2014 UN271 (Bernardinelli-Bernstein) to several other comets. The majority of comet nuclei observed are smaller than Halley’s comet. They are typically a mile across or less. Comet C/2014 UN271 is currently the record-holder for big comets. And, it may be just the tip of the iceberg. There could be many more monsters out there for astronomers to identify as sky surveys improve in sensitivity. Though astronomers know this comet must be big to be detected so far out to a distance of over 2 billion miles from Earth, only the Hubble Space Telescope has the sharpness and sensitivity to make a definitive estimate of nucleus size. Credits: Illustration: NASA, ESA, Zena Levy (STScI).

NASA's Hubble Space Telescope has determined the size of the largest icy comet nucleus ever seen by astronomers. The estimated diameter is approximately 80 miles across, making it larger than the state of Rhode Island. The nucleus is about 50 times larger than found at the heart of most known comets. Its mass is estimated to be a staggering 500 trillion tons, a hundred thousand times greater than the mass of a typical comet found much closer to the Sun.

The behemoth comet, C/2014 UN271 (Bernardinelli-Bernstein) is barreling this way at 22,000 miles per hour from the edge of the solar system. But not to worry. It will never get closer than 1 billion miles away from the Sun, which is slightly farther than the distance of the planet Saturn. And that won't be until the year 2031.

The previous record holder is comet C/2002 VQ94, with a nucleus estimated to be 60 miles across. It was discovered in 2002 by the Lincoln Near-Earth Asteroid Research (LINEAR) project.

"This comet is literally the tip of the iceberg for many thousands of comets that are too faint to see in the more distant parts of the solar system," said David Jewitt, a professor of planetary science and astronomy at the University of California, Los Angeles (UCLA), and co-author of the new study in The Astrophysical Journal Letters . "We've always suspected this comet had to be big because it is so bright at such a large distance. Now we confirm it is."

Comet C/2014 UN271 was discovered by astronomers Pedro Bernardinelli and Gary Bernstein in archival images from the Dark Energy Survey at the Cerro Tololo Inter-American Observatory in Chile. It was first serendipitously observed in November 2010, when it was a whopping 3 billion miles from the Sun, which is nearly the average distance to Neptune. Since then, it has been intensively studied by ground- and space-based telescopes.

"This is an amazing object, given how active it is when it's still so far from the Sun," said the paper's lead author Man-To Hui of the Macau University of Science and Technology, Taipa, Macau. "We guessed the comet might be pretty big, but we needed the best data to confirm this." So, his team used Hubble to take five photos of the comet on January 8, 2022.

The challenge in measuring this comet was how to discriminate the solid nucleus from the huge dusty coma enveloping it. The comet is currently too far away for its nucleus to be visually resolved by Hubble. Instead, the Hubble data show a bright spike of light at the nucleus' location. Hui and his team next made a computer model of the surrounding coma and adjusted it to fit the Hubble images. Then, the glow of the coma was subtracted to leave behind the starlike nucleus.

Hui and his team compared the brightness of the nucleus to earlier radio observations from the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. This combined data constrains the diameter and the reflectivity of the nucleus. The new Hubble measurements are close to the earlier size estimates from ALMA, but convincingly suggest a darker nucleus surface than previously thought. "It's big and it's blacker than coal," said Jewitt.

The comet has been falling toward the Sun for well over 1 million years. It is coming from the hypothesized nesting ground of trillions of comets, called the Oort Cloud. The diffuse cloud is thought to have an inner edge at 2,000 to 5,000 times the distance between the Sun and the Earth. Its outer edge might extend at least a quarter of the way out to the distance of the nearest stars to our Sun, the Alpha Centauri system.

The Oort Cloud's comets didn't actually form so far from the Sun; instead, they were tossed out of the solar system billions of years ago by a gravitational "pinball game" among the massive outer planets, when the orbits of Jupiter and Saturn were still evolving. The far-flung comets only travel back toward the Sun and planets if their distant orbits are disturbed by the gravitational tug of a passing star — like shaking apples out of a tree.

Comet Bernardinelli-Bernstein follows a 3-million-year-long elliptical orbit, taking it as far from the Sun as roughly half a light-year. The comet is now less than 2 billion miles from the Sun, falling nearly perpendicular to the plane of our solar system. At that distance temperatures are only about minus 348 degrees Fahrenheit. Yet that's warm enough for carbon monoxide to sublimate off the surface to produce the dusty coma.

Comet Bernardinelli-Bernstein provides an invaluable clue to the size distribution of comets in the Oort Cloud and hence its total mass. Estimates for the Oort Cloud's mass vary widely, reaching as high as 20 times Earth's mass. First hypothesized in 1950 by Dutch astronomer Jan Oort, the Oort Cloud still remains a theory because the innumerable comets that make it up are too faint and distant to be directly observed. Ironically, this means the solar system's largest structure is all but invisible. It's estimated that NASA's pair of Voyager spacecraft won't reach the inner realm of the Oort Cloud for another 300 years and could take as long as 30,000 years to pass through it.

Circumstantial evidence come from infalling comets that can be traced back to this nesting ground. They approach the Sun from all different directions meaning the cloud must be spherical in shape. These comets are deep-freeze samples of the composition of the early solar system, preserved for billions of years. The reality of the Oort Cloud is bolstered by theoretical modeling of the formation and evolution of the solar system. The more observational evidence that can be gathered through deep sky surveys coupled with multiwavelength observations, the better astronomers will understand the Oort Cloud's role in the solar system's evolution.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, in Washington, D.C.

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Release: NASA, ESA, STScI

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Ray Villard
Space Telescope Science Institute, Baltimore, Maryland

Science Contact: Man-To Hui
State Key Laboratory of Lunar and Planetary Science, Macau University of Science and Technology, Taipa, China

David Jewitt
University of California, Los Angeles, Los Angeles, California

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Direct inquiries to the News Team.

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• Science Paper: The science paper by Man-To Hui et al., PDF (871.09 KB)
• NASA's Hubble Portal
• UCLA's Press Release
• Goddard's Video (on YouTube)

Source: HubbleSite/News

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Interstellar Comet 2I/Borisov Swings Past the Sun

Comet 2I/Borisov Near and at Perihelion

Credits: NASA, ESA, and D. Jewitt (UCLA)

Release Images

These two images, taken by NASA's Hubble Space Telescope, capture comet 2I/Borisov streaking though our solar system and on its way back to interstellar space. It is only the second interstellar object known to have passed through the solar system.

"Hubble gives us the best upper limit of the size of comet Borisov's nucleus, which is the really important part of the comet," said David Jewitt, a UCLA professor of planetary science and astronomy, whose team has captured the best and sharpest look at this first confirmed interstellar comet. "Surprisingly, our Hubble images show that its nucleus is more than 15 times smaller than earlier investigations suggested it might be. Our Hubble images show that the radius is smaller than half-a-kilometer. Knowing the size is potentially useful for beginning to estimate how common such objects may be in the solar system and our galaxy. Borisov is the first known interstellar comet, and we would like to learn how many others there are."

Crimean amateur astronomer Gennady Borisov discovered the comet on August 30, 2019 and reported the position measurements to the International Astronomical Union's Minor Planet Center in Cambridge, Massachusetts. The Center for Near-Earth Object Studies at the Jet Propulsion Laboratory, working with the Minor Planet Center, computed an orbit for the comet which shows that it came from elsewhere in our Milky Way galaxy, point of origin unknown.

Nevertheless, observations by numerous telescopes show that the comet's chemical composition is similar to the comets found inside our solar system, providing evidence that comets also form around other stars. By the middle of 2020 the comet will have already zoomed past Jupiter's distance of 500 million miles on its way back into the frozen abyss of interstellar space.

[left] November 16, 2019 photo

The comet appears in front of a distant background spiral galaxy (2MASX J10500165-0152029). The galaxy's bright central core is smeared in the image because Hubble was tracking the comet. Comet Borisov was approximately 203 million miles from Earth in this exposure. Its tail of ejected dust streaks off to the upper right. The comet has been artificially colored blue to discriminate fine detail in the halo of dust, or coma, surrounding the central nucleus. It also helps to visually separate the comet from the background galaxy.

[right] December 9, 2019 photo

Hubble revisited the comet shortly after its closest approach to the Sun where it received maximum heating after spending most of its life in frigid interstellar space. The comet also reached a breathtaking maximum speed of about 100,000 miles per hour. Comet Borisov is 185 million miles from Earth in this photo, near the inner edge of the asteroid belt but below it. The nucleus, an agglomeration of ices and dust, is still too small to be resolved. The bright central portion is a coma made up of dust leaving the surface. The comet will make its closest approach to Earth in late December at a distance of 180 million miles.

The Hubble Space Telescope is a project of international cooperation between the European Space Agency (ESA) and NASA. NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C. The Minor Planet Center and the Center for Near-Earth Orbit Studies are projects of NASA’s Near-Earth Object Observations Program of the Planetary Defense Coordination Office at NASA Headquarters.

Source: HubbleSite/News

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Contact

Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
410-338-4514
villard@stsci.edu

Stuart Wolpert
UCLA, Los Angeles, California
swolpert@stratcomm.ucla.edu

David Jewitt
UCLA, Los Angeles, California
jewitt@ucla.edu

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Related Links

• NASA's Hubble Portal
• ESA/Hubble's Release
• UCLA's Release
• STScI's Comet 2I/Borisov Release (Oct. 16, 2019)

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NASA’s Exoplanet-Hunting Mission Catches a Natural Comet Outburst in Unprecedented Detail

This animation shows an explosive outburst of dust, ice and gases from comet 46P/Wirtanen that occurred on September 26, 2018 and dissipated over the next 20 days. The images, from NASA’s TESS spacecraft, were taken every three hours during the first three days of the outburst. Credits: Farnham et al./NASA. View enlarged image

Using data from NASA’s Transiting Exoplanet Survey Satellite (TESS), astronomers at the University of Maryland (UMD), in College Park, Maryland, have captured a clear start-to-finish image sequence of an explosive emission of dust, ice and gases during the close approach of comet 46P/Wirtanen in late 2018. This is the most complete and detailed observation to date of the formation and dissipation of a naturally-occurring comet outburst. The team members reported their results in the November 22 issue of The Astrophysical Journal Letters.

“TESS spends nearly a month at a time imaging one portion of the sky. With no day or night breaks and no atmospheric interference, we have a very uniform, long-duration set of observations,” said Tony Farnham, a research scientist in the UMD Department of Astronomy and the lead author of the research paper. “As comets orbit the Sun, they can pass through TESS’ field of view. Wirtanen was a high priority for us because of its close approach in late 2018, so we decided to use its appearance in the TESS images as a test case to see what we could get out of it. We did so and were very surprised!”

Normal comet activity is driven by sunlight vaporizing the ices near the surface of the nucleus, and the outflowing gases drag dust off the nucleus to form the coma. However, many comets are known to experience occasional spontaneous outbursts that can significantly, but temporarily increase the comet's activity. It is not currently known what causes outbursts, but they are related to the conditions on the comet's surface. A number of potential trigger mechanisms have been proposed, including a thermal event, in which a heat wave penetrates into a pocket of highly volatile ices, causing the ice to rapidly vaporize and produce an explosion of activity, and a mechanical event, where a cliff collapses, exposing fresh ice to direct sunlight. Thus, studies of the outburst behavior, especially in the early brightening stages that are difficult to capture, can help us understand the physical and thermal properties of the comet.

Although Wirtanen came closest to Earth on December 16, 2018, the outburst occurred earlier in its approach, beginning on September 26, 2018. The initial brightening of the outburst occurred in two distinct phases, with an hour-long flash followed by a more gradual second stage that continued to grow brighter for another 8 hours. This second stage was likely caused by the gradual spreading of comet dust from the outburst, which causes the dust cloud to reflect more sunlight overall. After reaching peak brightness, the comet faded gradually over a period of more than two weeks. Because TESS takes detailed, composite images every 30 minutes, the team was able to view each phase in exquisite detail.

“With 20 days’ worth of very frequent images, we were able to assess changes in brightness very easily. That’s what TESS was designed for, to perform its primary job as an exoplanet surveyor,” Farnham said. “We can’t predict when comet outbursts will happen. But even if we somehow had the opportunity to schedule these observations, we couldn’t have done any better in terms of timing. The outburst happened mere days after the observations started.”

The team has generated a rough estimate of how much material may have been ejected in the outburst, about one million kilograms (2.2 million pounds), which could have left a crater on the comet of around 20 meters (about 65 feet) across. Further analysis of the estimated particle sizes in the dust tail may help improve this estimate. Observing more comets will also help to determine whether multi-stage brightening is rare or commonplace in comet outbursts.

TESS has also detected for the first time Wirtanen’s dust trail. Unlike a comet’s tail—the spray of gas and fine dust that follows behind a comet, growing as it approaches the sun—a comet’s trail is a field of larger debris that traces the comet’s orbital path as it travels around the sun. Unlike a tail, which changes direction as it is blown by the solar wind, the orientation of the trail stays more or less constant over time.

“The trail more closely follows the orbit of the comet, while the tail is offset from it, as it gets pushed around by the sun’s radiation pressure. What’s significant about the trail is that it contains the largest material,” said Michael Kelley, an associate research scientist in the UMD Department of Astronomy and a co-author of the research paper. “Tail dust is very fine, a lot like smoke. But trail dust is much larger—more like sand and pebbles. We think comets lose most of their mass through their dust trails. When the Earth runs into a comet’s dust trail, we get meteor showers.”

While the current study describes initial results, Farnham, Kelley and their colleagues look forward to further analyses of Wirtanen, as well as other comets in TESS’ field of view. “We also don’t know what causes natural outbursts and that’s ultimately what we want to find,” Farnham said. “There are at least four other comets in the same area of the sky where TESS made these observations, with a total of about 50 comets expected in the first two years’ worth of TESS data. There’s a lot that can come of these data.”

TESS is a NASA Astrophysics Explorer mission led and operated by MIT in Cambridge, Massachusetts, and managed by NASA's Goddard Space Flight Center. Additional partners include Northrop Grumman, based in Falls Church, Virginia; NASA’s Ames Research Center in California’s Silicon Valley; the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts; MIT’s Lincoln Laboratory; and the Space Telescope Science Institute in Baltimore. More than a dozen universities, research institutes and observatories worldwide are participants in the mission.

Claire Andreoli
NASA’s Goddard Space Flight Center
301-286 -1940
claire.andreoli@nasa.gov

Matthew Wright
University of Maryland, College Park
301-405-9267
mewright@umd.edu

Source: NASA/TESS

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NASA's Webb to Unlock the Mysteries of Comets and the Early Solar System

Comet Hale-Bopp

Credits: E. Kolmhofer, H. Raab; Johannes-Kepler-Observatory, Linz, Austria (http://www.sternwarte.at). Available under Creative Commons CC-by-SA 3.0.

Nucleus of Comet 19P/Borrelly

Credits: NASA/JPL

Release images

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Astronomers to study three different types of comets

Though no longer thought of as harbingers of doom, comets are still mysterious. Scientists using NASA’s James Webb Space Telescope plan to unlock some of those mysteries when they study three different types of comets to learn more about them and about the early solar system. Astronomers are already somewhat familiar with two of the comets—Read and Borrelly. The third is a “target-of-opportunity,” one that is not yet known but is expected to be discovered in the first year of Webb’s mission. If they are lucky, perhaps they will capture an interstellar comet. Or perhaps they will train Webb on a comet from the Oort Cloud, a spherical cloud of icy bodies surrounding our solar system.

Since ancient times, comets have fascinated sky-watchers, who often considered them divine omens. A Chinese historian recorded an apparition of Comet Halley as far back as 240 B.C., describing it as a “broom star.” The Babylonians and Romans also referenced the comet’s appearance, but perhaps its most famous depiction is in the Bayeux Tapestry, which commemorates the Norman Conquest of England in 1066. The tapestry shows King Harold and a crowd of fearful Englishmen pointing to Comet Halley as it looms in the sky.

We now know that comets — which are clumps of rock, dirt, dust, and ice in space — are not harbingers of doom, but there is still much we don’t know about them. Because comets have changed very little in the solar system's 4.6-billion-year history, they are among the most primitive bodies scientists can study.

Shortly after its launch in 2021, NASA’s James Webb Space Telescope will observe three different types of comets in infrared light, which is invisible to human eyes. By learning more about comets, scientists can gain new insights into what the solar system was like billions of years ago.

Webb, A Powerful Tool

These three comet studies will be conducted through Webb's Guaranteed Time Observations (GTO) program of the solar system led by Heidi Hammel, a planetary scientist who was selected by NASA as a Webb Interdisciplinary Scientist in 2002. She is also executive vice president of the Association of Universities for Research in Astronomy (AURA) in Washington, D.C. Hammel’s program will demonstrate Webb's capabilities for tracking moving targets and looking at bright objects in the solar system.

“We want to study comets with Webb because of the telescope’s very powerful capabilities in the near- and mid-infrared,” Hammel says. “What makes those wavelengths of light particularly powerful for cometary studies is that they allow us to study the chemical makeup of this dust and gas that’s come off of the comet’s nucleus and figure out what it is."

Molecules of gas and dust emit and absorb infrared wavelengths of light, so by analyzing this light, Webb can determine which chemicals are present. "If this is primitive material, it will give us some clues to the makeup of the early solar system,” Hammel says.

Comparing Different Comet Families

When comets venture close to the Sun, some of their ice turns into vapor. This vapor forms an envelope, or coma, of gases and dust around the central body, or nucleus. The Sun’s solar wind and radiation pressure from sunlight stream this coma away from the nucleus, creating comet tails. The word “comet” comes from the Greek "kome,” which means "hair." In ancient times, comets were thought to be stars with hair streaming off them.

Scientists using time from Hammel’s program plan to map the inner comae of three different types of comets, one of which has not yet been discovered:

A Jupiter-Family Comet (proposed target: Comet Borrelly): With an orbit strongly affected by the gravity of the giant planet Jupiter, Comet Borrelly is classified as a Jupiter-family comet. A science team led by Michael Kelley of the University of Maryland plans to study how the relatively bright comet’s gases and dust escape the nucleus, and what happens to them after they leave. The team will map individual types of gas and study the composition of the comet’s dust, which will help them understand how a comet works.

A Main-Belt Comet (proposed target: Comet Read): The second target to be studied, Comet Read, is fainter and smaller than Borrelly. It is a Main-Belt comet, meaning it orbits within the asteroid belt, even though it acts like a comet for part of its orbit. Kelley and his team will try to detect the gas—and particularly water—around this comet. This has never been done for a Main-Belt comet; until now, scientists have only been able to detect their dust.

A Target-of-Opportunity Comet: In a study led by Stefanie Milam of NASA’s Goddard Space Flight Center, scientists will investigate a target comet that is not yet known, but is expected to be discovered shortly after Webb’s launch. This third type of comet might come from the Oort Cloud, a spherical cloud surrounding our solar system very far from the planets. The outer Oort Cloud is only loosely bound to the solar system, and it is subject to gravitational forces that occasionally dislodge comets from within the cloud and send them toward the inner solar system. Alternatively, this opportunistic comet might be an interstellar interloper. To date, just two interstellar objects have been detected passing through our solar system: ‘Oumuamua in 2017, and the newly detected object called C/2019 Q4 (Borisov). “Oort Cloud comets are really long-period comets that approach the Sun very rarely, and they tend to have a lot more ice in them and a lot more volatile material,” explains Milam. “So they make these big, beautiful, bright comae. They’re usually huge apparitions on the sky, and that’s what the focus would be for that comet.” Hammel notes that we aren’t quite sure what Webb would see for an interstellar object. “One of Webb’s strengths is its ability to sense faint objects, and that makes it a great tool to study these very rare and very faint interstellar interlopers. If we could glean compositional information about its surface, that might open a whole new field of study.”

Astronomers are not limited to just these objects.

“Ultimately, these are just individual examples, but over Webb’s lifetime, we’ll eventually observe many comets, and we’ll have lots of examples from these different classes, and we can compare them all to each other,” says Kelley. “With time — and in conjunction with all the ground-based data that we’ve had and will continue to obtain — we’ll have a better understanding of where these comets come from."

Among the questions that scientists hope to answer with Webb: Are all solar system comets derived from a uniform population, and they’ve all just evolved differently? Or are they really chemically distinct from the start, and we’re just seeing that today? And, how do interstellar comets compare with local comets?

The James Webb Space Telescope will be the world’s premier space science observatory when it launches in 2021. Webb will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.

Source: NASA's James Webb Space Telescope/News Release

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Contact:

Ann Jenkins / Christine Pulliam
Space Telescope Science Institute, Baltimore, Maryland
410-338-4488 / 410-338-4366
jenkins@stsci.edu / cpulliam@stsci.edu

Related Links: NASA's Webb Portal

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ESO’s VLT Sees `Oumuamua Getting a Boost

PR Image eso1820a

Artist’s impression of the interstellar asteroid `Oumuamua

PR Image eso1820b

Predicted position of `Oumuamua versus observed position

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Videos

PR Video eso1820a

ESOcast 167: VLT sees `Oumuamua getting a boost

PR Video eso1820b

Animation of `Oumuamua outgassing

PR Video eso1820c

Animation of `Oumuamua outgassing and rotating

PR Video eso1820d

Animation of `Oumuamua passing through the Solar System

PR Video eso1820e

Animation of `Oumuamua passing through the Solar System (annotated)

PR Video eso1820f

Animation showing the expected and measured trajectory of `Oumuamua

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New results indicate interstellar nomad `Oumuamua is a comet

`Oumuamua, the first interstellar object discovered in the Solar System, is moving away from the Sun faster than expected. This anomalous behaviour was detected by a worldwide astronomical collaboration including ESO’s Very Large Telescope in Chile. The new results suggest that `Oumuamua is most likely an interstellar comet and not an asteroid. The discovery appears in the journal Nature.

`Oumuamua — the first interstellar object discovered within our Solar System — has been the subject of intense scrutiny since its discovery in October 2017 [1]. Now, by combining data from the ESO’s Very Large Telescope and other observatories, an international team of astronomers has found that the object is moving faster than predicted. The measured gain in speed is tiny and `Oumuamua is still slowing down because of the pull of the Sun — just not as fast as predicted by celestial mechanics.

The team, led by Marco Micheli (European Space Agency) explored several scenarios to explain the faster-than-predicted speed of this peculiar interstellar visitor. The most likely explanation is that `Oumuamua is venting material from its surface due to solar heating — a behaviour known as outgassing [2]. The thrust from this ejected material is thought to provide the small but steady push that is sending `Oumuamua hurtling out of the Solar System faster than expected — as of 1 June 2018  it is traveling at roughly 114 000 kilometres per hour.

Such outgassing is a behaviour typical for comets and contradicts the previous classification of `Oumuamua as an interstellar asteroid. “We think this is a tiny, weird comet,” commented Marco Micheli. “We can see in the data that its boost is getting smaller the farther away it travels from the Sun, which is typical for comets.”

Usually, when comets are warmed by the Sun they eject dust and gas, which form a cloud of material — called a coma — around them, as well as the characteristic tail. However, the research team could not detect any visual evidence of outgassing.

“We did not see any dust, coma, or tail, which is unusual,” explained co-author Karen Meech of the University of Hawaii, USA. Meech led the discovery team’s characterisation of `Oumuamua in 2017.  “We think that ‘Oumuamua may vent unusually large, coarse dust grains.”

The team speculated that perhaps the small dust grains adorning the surface of most comets eroded during `Oumuamua’s journey through interstellar space, with only larger dust grains remaining. Though a cloud of these larger particles would not be bright enough to be detected, it would explain the unexpected change to ‘Oumuamua’s speed.

Not only is `Oumuamua’s hypothesised outgassing an unsolved mystery, but also its interstellar origin. The team originally performed the new observations on `Oumuamua to exactly determine its path which would have probably allowed it to trace the object back to its parent star system. The new results means it will be more challenging to obtain this information.

“The true nature of this enigmatic interstellar nomad may remain a mystery,” concluded team member Olivier Hainaut, an astronomer at ESO. “`Oumuamua’s recently-detected gain in speed makes it more difficult to be able to trace the path it took from its extrasolar home star.”

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Notes

[1]`Oumuamua, pronounced “oh-MOO-ah-MOO-ah”, was first discovered using the Pan-STARRS telescope at the Haleakala Observatory, Hawaii. Its name means “scout” in Hawaiian, and reflects its nature as the first known object of interstellar origin to have entered the Solar System.  The original observations indicated it was an elongated, tiny object whose colour were similar to that of a comet.

[2] The team tested several hypothesis to explain the unexpected change in speed. They analysed if solar radiation pressure, the Yarkovsky effect, or friction-like effects could explain the observations. It was also checked if the gain in speed could have been caused by an impulse event (such as a collision), by `Oumuamua being a binary object or by `Oumuamua being a magnetised object.  The unlikely theory that `Oumuamua is an interstellar spaceship was also rejected: the facts that the smooth and continuous change in speed is not typical for thrusters and that the object is tumbling on all three axis speak against it being an artificial object.

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More Information

The research team’s work is presented in the scientific paper “Non-gravitational acceleration in the trajectory of 1I/2017 U1 (`Oumuamua)”, which will be published in the journal Nature on 27 June 2018.

The international team of astronomers in this study consists of Marco Micheli (European Space Agency & INAF, Italy), Davide Farnocchia (NASA Jet Propulsion Laboratory, USA), Karen J. Meech (University of Hawaii Institute for Astronomy, USA), Marc W. Buie (Southwest Research Institute, USA), Olivier R. Hainaut (European Southern Observatory, Germany), Dina Prialnik (Tel Aviv University School of Geosciences, Israel), Harold A. Weaver (Johns Hopkins University Applied Physics Laboratory, USA), Paul W. Chodas (NASA Jet Propulsion Laboratory, USA), Jan T. Kleyna (University of Hawaii Institute for Astronomy, USA), Robert Weryk (University of Hawaii Institute for Astronomy, USA), Richard J. Wainscoat (University of Hawaii Institute for Astronomy, USA), Harald Ebeling (University of Hawaii Institute for Astronomy, USA), Jacqueline V. Keane (University of Hawaii Institute for Astronomy, USA), Kenneth C. Chambers (University of Hawaii Institute for Astronomy, USA), Detlef Koschny (European Space Agency, European Space Research and Technology Centre, & Technical University of Munich, Germany), and Anastassios E. Petropoulos (NASA Jet Propulsion Laboratory, USA).

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It has 15 Member States: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile and with Australia as a strategic partner. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its world-leading Very Large Telescope Interferometer as well as two survey telescopes, VISTA working in the infrared and the visible-light VLT Survey Telescope. ESO is also a major partner in two facilities on Chajnantor, APEX and ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre Extremely Large Telescope, the ELT, which will become “the world’s biggest eye on the sky”.

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Links

• Images of Hubble
• Hubblesite release
• ESA/Hubble press release
• Institute for Astronomy (University of Hawaii) press release
• Canada-France-Hawaii Telescope press release
• European Space Agency press release
• TED talk by Karen Meech
• Nature Blog post by Olivier Hainaut
• Science paper
• Press release about the discovery of `Oumuamua

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Contacts:

Olivier Hainaut
European Southern Observatory
Garching, Germany
Tel: +49 89 3200 6752
Email: ohainaut@eso.org

Marco Micheli
Space Situational Awareness Near-Earth Object Coordination Centre, European Space Agency
Frascati, Italy
Tel: +39 06 941 80365
Email: marco.micheli@esa.int

Karen Meech
Institute for Astronomy, University of Hawaii
Honolulu, USA
Cell: +1 720 231 7048
Email: meech@IfA.Hawaii.Edu

Richard Hook
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: pio@eso.org

Source: ESO/News

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Large, Distant Comets More Common Than Previously Thought

This illustration shows how scientists used data from NASA's WISE spacecraft to determine the nucleus sizes of comets. They subtracted a model of how dust and gas behave in comets in order to obtain the core size. Credit: NASA/JPL-Caltech. › Larger view

Comets that take more than 200 years to make one revolution around the Sun are notoriously difficult to study. Because they spend most of their time far from our area of the solar system, many "long-period comets" will never approach the Sun in a person's lifetime. In fact, those that travel inward from the Oort Cloud -- a group of icy bodies beginning roughly 186 billion miles (300 billion kilometers) away from the Sun -- can have periods of thousands or even millions of years.

NASA's WISE spacecraft, scanning the entire sky at infrared wavelengths, has delivered new insights about these distant wanderers. Scientists found that there are about seven times more long-period comets measuring at least 0.6 miles (1 kilometer) across than had been predicted previously. They also found that long-period comets are on average up to twice as large as "Jupiter family comets," whose orbits are shaped by Jupiter's gravity and have periods of less than 20 years. 

Researchers also observed that in eight months, three to five times as many long-period comets passed by the Sun than had been predicted. The findings are published in the Astronomical Journal.

"The number of comets speaks to the amount of material left over from the solar system's formation," said James Bauer, lead author of the study and now a research professor at the University of Maryland, College Park. "We now know that there are more relatively large chunks of ancient material coming from the Oort Cloud than we thought."

The Oort Cloud is too distant to be seen by current telescopes, but is thought to be a spherical distribution of small icy bodies at the outermost edge of the solar system. The density of comets within it is low, so the odds of comets colliding within it are rare. Long-period comets that WISE observed probably got kicked out of the Oort Cloud millions of years ago. The observations were carried out during the spacecraft's primary mission before it was renamed NEOWISE and reactivated to target near-Earth objects (NEOs).

"Our study is a rare look at objects perturbed out of the Oort Cloud," said Amy Mainzer, study co-author based at NASA's Jet Propulsion Laboratory, Pasadena, California, and principal investigator of the NEOWISE mission. "They are the most pristine examples of what the solar system was like when it formed."

Astronomers already had broader estimates of how many long-period and Jupiter family comets are in our solar system, but had no good way of measuring the sizes of long-period comets. That is because a comet has a "coma," a cloud of gas and dust that appears hazy in images and obscures the cometary nucleus. But by using the WISE data showing the infrared glow of this coma, scientists were able to "subtract" the coma from the overall comet and estimate the nucleus sizes of these comets. The data came from 2010 WISE observations of 95 Jupiter family comets and 56 long-period comets.

The results reinforce the idea that comets that pass by the Sun more often tend to be smaller than those spending much more time away from the Sun. That is because Jupiter family comets get more heat exposure, which causes volatile substances like water to sublimate and drag away other material from the comet's surface as well. 

"Our results mean there's an evolutionary difference between Jupiter family and long-period comets," Bauer said.

The existence of so many more long-period comets than predicted suggests that more of them have likely impacted planets, delivering icy materials from the outer reaches of the solar system. 

Researchers also found clustering in the orbits of the long-period comets they studied, suggesting there could have been larger bodies that broke apart to form these groups. 

The results will be important for assessing the likelihood of comets impacting our solar system's planets, including Earth. 

"Comets travel much faster than asteroids, and some of them are very big," Mainzer said. "Studies like this will help us define what kind of hazard long-period comets may pose." 

NASA's Jet Propulsion Laboratory in Pasadena, California, managed and operated WISE for NASA's Science Mission Directorate in Washington. The NEOWISE project is funded by the Near Earth Object Observation Program, now part of NASA's Planetary Defense Coordination Office. The spacecraft was put into hibernation mode in 2011 after twice scanned the entire sky, thereby completing its main objectives. In September 2013, WISE was reactivated, renamed NEOWISE and assigned a new mission to assist NASA's efforts to identify potentially hazardous near-Earth objects.

For more information on WISE, visit:  https://www.nasa.gov/wise


News Media Contact

Elizabeth Landau
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-6425
elizabeth.landau@jpl.nasa.gov

Source: JPL-Caltech/News

Unique Fragment from Earth’s Formation Returns after Billions of Years in Cold Storage

PR Image eso1614a

Artist's impression of the unique rocky comet C/2014 S3 (PANSTARRS)

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The unique rocky comet C/2014 S3 (PANSTARRS) 

PR Image eso1614c

The unique rocky comet C/2014 S3 (PANSTARRS)

Videos

 

PR Video eso1614a

The unique rocky comet C/2014 S3 (PANSTARRS)

Tailless Manx comet from Oort Cloud brings clues about the origin of the Solar System

 

Astronomers have found a unique object that appears to be made of inner Solar System material from the time of Earth’s formation, which has been preserved in the Oort Cloud far from the Sun for billions of years. Observations with ESO’s Very Large Telescope, and the Canada France Hawai`i Telescope, show that C/2014 S3 (PANSTARRS) is the first object to be discovered on a long-period cometary orbit that has the characteristics of a pristine inner Solar System asteroid. It may provide important clues about how the Solar System formed.

In a paper to be published today in the journal Science Advances, lead author Karen Meech of the University of Hawai`i’s Institute for Astronomy and her colleagues conclude that C/2014 S3 (PANSTARRS) formed in the inner Solar System at the same time as the Earth itself, but was ejected at a very early stage.

Their observations indicate that it is an ancient rocky body, rather than a contemporary asteroid that strayed out. As such, it is one of the potential building blocks of the rocky planets, such as the Earth, that was expelled from the inner Solar System and preserved in the deep freeze of the Oort Cloud for billions of years [1].

Karen Meech explains the unexpected observation: “We already knew of many asteroids, but they have all been baked by billions of years near the Sun. This one is the first uncooked asteroid we could observe: it has been preserved in the best freezer there is.”

C/2014 S3 (PANSTARRS) was originally identified by the Pan-STARRS1 telescope as a weakly active comet a little over twice as far from the Sun as the Earth. Its current long orbital period (around 860 years) suggests that its source is in the Oort Cloud, and it was nudged comparatively recently into an orbit that brings it closer to the Sun.

The team immediately noticed that C/2014 S3 (PANSTARRS) was unusual, as it does not have the characteristic tail that most long-period comets have when they approach so close to the Sun. As a result, it has been dubbed a Manx comet, after the tailless cat. Within weeks of its discovery, the team obtained spectra of the very faint object with ESO’s Very Large Telescope in Chile.

Careful study of the light reflected by C/2014 S3 (PANSTARRS) indicates that it is typical of asteroids known as S-type, which are usually found in the inner asteroid main belt. It does not look like a typical comet, which are believed to form in the outer Solar System and are icy, rather than rocky. It appears that the material has undergone very little processing, indicating that it has been deep frozen for a very long time. The very weak comet-like activity associated with C/2014 S3 (PANSTARRS), which is consistent with the sublimation of water ice, is about a million times lower than active long-period comets at a similar distance from the Sun.

The authors conclude that this object is probably made of fresh inner Solar System material that has been stored in the Oort Cloud and is now making its way back into the inner Solar System.

A number of theoretical models are able to reproduce much of the structure we see in the Solar System. An important difference between these models is what they predict about the objects that make up the Oort Cloud. Different models predict significantly different ratios of icy to rocky objects. This first discovery of a rocky object from the Oort Cloud is therefore an important test of the different predictions of the models. The authors estimate that observations of 50–100 of these Manx comets are needed to distinguish between the current models, opening up another rich vein in the study of the origins of the Solar System.

Co-author Olivier Hainaut (ESO, Garching, Germany), concludes: “We’ve found the first rocky comet, and we are looking for others. Depending how many we find, we will know whether the giant planets danced across the Solar System when they were young, or if they grew up quietly without moving much.”

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Notes

[1] The Oort cloud is a huge region surrounding the Sun like a giant, thick soap bubble. It is estimated that it contains trillions of tiny icy bodies. Occasionally, one of these bodies gets nudged and falls into the inner Solar System, where the heat of the sun turns it into a comet. These icy bodies are thought to have been ejected from the region of the giant planets as these were forming, in the early days of the Solar System.

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More information

This research was presented in a paper entitled “Inner Solar System Material Discovered in the Oort Cloud”, by Karen Meech et al., in the journal Science Advances.

The team is composed of Karen J. Meech (Institute for Astronomy, University of Hawai`i, USA), Bin Yang (ESO, Santiago, Chile), Jan Kleyna (Institute for Astronomy, University of Hawai`i, USA), Olivier R. Hainaut (ESO, Garching, Germany), Svetlana Berdyugina (Institute for Astronomy, University of Hawai’i, USA; Kiepenheuer Institut für Sonnenphysik, Freiburg, Germany), Jacqueline V. Keane (Institute for Astronomy, University of Hawai`i, USA), Marco Micheli (ESA, Frascati, Italy), Alessandro Morbidelli (Laboratoire Lagrange/Observatoire de la Côte d’Azur/CNRS/Université Nice Sophia Antipolis, France) and Richard J. Wainscoat (Institute for Astronomy, University of Hawai`i, USA).

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

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Links

• Research paper
• Photos of the VLT
• Canada France Hawai`i Telescope

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Contacts


Karen Meech
Institute for Astronomy, University of Hawai`i
Honolulu, HI, USA
Tel: +1 808 956 6828
Cell: +1 720 231 7048
Email: meech@ifa.hawaii.edu

Olivier Hainaut
ESO Astronomer
Garching bei München, Germany
Tel: +49 89 3200 6752
Cell: +49 151 2262 0554
Email: ohainaut@eso.org

Richard Hook
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org

Source: ESO