NASA's Webb Images Young, Giant Exoplanets, Detects Carbon Dioxide

HR 8799 (NIRCam Image)
Credits/Image: NASA, ESA, CSA, STScI, Laurent Pueyo (STScI), William Balmer (JHU), Marshall Perrin (STScI)

51 Eridani (NIRCam Image)
Credits/Image: NASA, ESA, CSA, STScI, Laurent Pueyo (STScI), William Balmer (JHU), Marshall Perrin (STScI)

Young Gas Giant HR 8799 e (NIRCam Spectrum)
Credits/Illustration: NASA, ESA, CSA, STScI, Joseph Olmsted (STScI)

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NASA’s James Webb Space Telescope has captured direct images of multiple gas giant planets within an iconic planetary system. HR 8799, a young system 130 light-years away, has long been a key target for planet formation studies.

The observations indicate that the well-studied planets of HR 8799 are rich in carbon dioxide gas. This provides strong evidence that the system’s four giant planets formed much like Jupiter and Saturn, by slowly building solid cores that attract gas from within a protoplanetary disk, a process known as core accretion.

The results also confirm that Webb can infer the chemistry of exoplanet atmospheres through imaging. This technique complements Webb’s powerful spectroscopic instruments, which can resolve the atmospheric composition.

“By spotting these strong carbon dioxide features, we have shown there is a sizable fraction of heavier elements, like carbon, oxygen, and iron, in these planets’ atmospheres,” said William Balmer, of Johns Hopkins University in Baltimore. “Given what we know about the star they orbit, that likely indicates they formed via core accretion, which is an exciting conclusion for planets that we can directly see.”

Balmer is the lead author of the study announcing the results published today in The Astrophysical Journal. Balmer and their team’s analysis also includes Webb’s observation of a system 97 light-years away called 51 Eridani.

HR 8799 is a young system about 30 million years old, a fraction of our solar system’s 4.6 billion years. Still hot from their tumultuous formation, the planets within HR 8799 emit large amounts of infrared light that give scientists valuable data on how they formed.

Giant planets can take shape in two ways: by slowly building solid cores with heavier elements that attract gas, just like the giants in our solar system, or when particles of gas rapidly coalesce into massive objects from a young star’s cooling disk, which is made mostly of the same kind of material as the star. The first process is called core accretion, and the second is called disk instability. Knowing which formation model is more common can give scientists clues to distinguish between the types of planets they find in other systems.

“Our hope with this kind of research is to understand our own solar system, life, and ourselves in the comparison to other exoplanetary systems, so we can contextualize our existence,” Balmer said. “We want to take pictures of other solar systems and see how they’re similar or different when compared to ours. From there, we can try to get a sense of how weird our solar system really is—or how normal.”

Of the nearly 6,000 exoplanets discovered, few have been directly imaged, as even giant planets are many thousands of times fainter than their stars. The images of HR 8799 and 51 Eridani were made possible by Webb’s NIRCam (Near-Infrared Camera) coronagraph, which blocks light from bright stars to reveal otherwise hidden worlds.

This technology allowed the team to look for infrared light emitted by the planets in wavelengths that are absorbed by specific gases. The team found that the four HR 8799 planets contain more heavy elements than previously thought.

The team is paving the way for more detailed observations to determine whether objects they see orbiting other stars are truly giant planets or objects such as brown dwarfs, which form like stars but don’t accumulate enough mass to ignite nuclear fusion.

“We have other lines of evidence that hint at these four HR 8799 planets forming using this bottom-up approach” said Laurent Pueyo, an astronomer at the Space Telescope Science Institute in Baltimore, who co-led the work. “How common is this for planets we can directly image? We don't know yet, but we're proposing more Webb observations to answer that question.”

“We knew Webb could measure colors of the outer planets in directly imaged systems,” added Rémi Soummer, director of STScI’s Russell B. Makidon Optics Lab and former lead for Webb coronagraph operations. “We have been waiting for 10 years to confirm that our finely tuned operations of the telescope would also allow us to access the inner planets. Now the results are in and we can do interesting science with it.”

The NIRCam observations of HR 8799 and 51 Eridani were conducted as part of Guaranteed Time Observations programs 1194 and 1412 respectively.

The James Webb Space Telescope is the world’s premier space science observatory. 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

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NASA's Webb to Study Young Exoplanets on the Edge

Left: This is an image of the star HR 8799 taken by Hubble’s Near Infrared Camera and Multi-Object Spectrometer (NICMOS) in 1998. A mask within the camera (coronagraph) blocks most of the light from the star. Astronomers also used software to digitally subtract more starlight. Nevertheless, scattered light from HR 8799 dominates the image, obscuring four faint planets later discovered from ground-based observations. Right: A re-analysis of NICMOS data in 2011 uncovered three of the exoplanets, which were not seen in the 1998 images. Webb will probe the planets’ atmospheres at infrared wavelengths astronomers have rarely used to image distant worlds. Credits: NASA, ESA, and R. Soummer (STScI). Hi-res image

Before planets around other stars were first discovered in the 1990s, these far-flung exotic worlds lived only in the imagination of science fiction writers.

But even their creative minds could not have conceived of the variety of worlds astronomers have uncovered. Many of these worlds, called exoplanets, are vastly different from our solar system’s family of planets. They range from star-hugging “hot Jupiters” to oversized rocky planets dubbed “super Earths.” Our universe apparently is stranger than fiction.

Seeing these distant worlds isn’t easy because they get lost in the glare of their host stars. Trying to detect them is like straining to see a firefly hovering next to a lighthouse’s brilliant beacon.

That’s why astronomers have identified most of the more than 4,000 exoplanets found so far using indirect techniques, such as through a star’s slight wobble or its unexpected dimming as a planet passes in front of it, blocking some of the starlight.

These techniques work best, however, for planets orbiting close to their stars, where astronomers can detect changes over weeks or even days as the planet completes its racetrack orbit. But finding only star-skimming planets doesn’t provide astronomers with a comprehensive picture of all the possible worlds in star systems.

Another technique researchers use in the hunt for exoplanets, which are planets orbiting other stars, is one that focuses on planets that are farther away from a star’s blinding glare. Scientists have uncovered young exoplanets that are so hot they glow in infrared light using specialized imaging techniques that block out the glare from the star. In this way, some exoplanets can be directly seen and studied.

NASA’s upcoming James Webb Space Telescope will help astronomers probe farther into this bold new frontier. Webb, like some ground-based telescopes, is equipped with special optical systems called coronagraphs, which use masks designed to block out as much starlight as possible to study faint exoplanets and to uncover new worlds.

This schematic shows the positions of the four exoplanets orbiting far away from the nearby star HR 8799. The orbits appear elongated because of a slight tilt of the plane of the orbits relative to our line of sight. The size of the HR 8799 planetary system is comparable to our solar system, as indicated by the orbit of Neptune, shown to scale. Credits: NASA, ESA, and R. Soummer (STScI)

Two targets early in Webb’s mission are the planetary systems 51 Eridani and HR 8799. Out of the few dozen directly imaged planets, astronomers plan to use Webb to analyze in detail the systems that are closest to Earth and have planets at the widest separations from their stars. This means that they appear far enough away from a star’s glare to be directly observed. The HR 8799 system resides 133 light-years and 51 Eridani 96 light-years from Earth.

Webb's Planetary Targets 

Two observing programs early in Webb’s mission combine the spectroscopic capabilities of the Near Infrared Spectrograph (NIRSpec) and the imaging of the Near Infrared Camera (NIRCam) and Mid-Infrared Instrument (MIRI) to study the four giant planets in the HR 8799 system. In a third program, researchers will use NIRCam to analyze the giant planet in 51 Eridani.

The four giant planets in the HR 8799 system are each roughly 10 Jupiter masses. They orbit more than 14 billion miles from a star that is slightly more massive than the Sun. The giant planet in 51 Eridani is twice the mass of Jupiter and orbits about 11 billion miles from a Sun-like star. Both planetary systems have orbits oriented face-on toward Earth. This orientation gives astronomers a unique opportunity to get a bird's-eye view down on top of the systems, like looking at the concentric rings on an archery target.

Many exoplanets found in the outer orbits of their stars are vastly different from our solar system planets. Most of the exoplanets discovered in this outer region, including those in HR 8799, are between 5 and 10 Jupiter masses, making them the most massive planets ever found to date.

These outer exoplanets are relatively young, from tens of millions to hundreds of millions of years old—much younger than our solar system’s 4.5 billion years. So they’re still glowing with heat from their formation. The images of these exoplanets are essentially baby pictures, revealing planets in their youth.

Webb will probe into the mid-infrared, a wavelength range astronomers have rarely used before to image distant worlds. This infrared “window” is difficult to observe from the ground because of thermal emission from and absorption in Earth’s atmosphere.

“Webb’s strong point is the uninhibited light coming through space in the mid-infrared range,” said Klaus Hodapp of the University of Hawaii in Hilo, lead investigator of the NIRSpec observations of the HR 8799 system. “Earth’s atmosphere is pretty difficult to work through. The major absorption molecules in our own atmosphere prevent us from seeing interesting features in planets.”

This discovery image of a Jupiter-sized extrasolar planet orbiting the nearby star 51 Eridani was taken in near-infrared light in 2014 by the Gemini Planet Imager. The bright central star is hidden behind a mask in the center of the image to enable the detection of the exoplanet, which is 1 million times fainter than 51 Eridani. The exoplanet is on the outskirts of the planetary system 11 billion miles from its star. Webb will probe the planet’s atmosphere at infrared wavelengths astronomers have rarely used to image distant worlds. Credits: International Gemini Observatory/NOIRLab/NSF/AURA, J. Rameau (University of Montreal), and C. Marois (National Research Council of Canada Herzberg). Hi-res image

The mid-infrared “is the region where Webb really will make seminal contributions to understanding what are the particular molecules, what are the properties of the atmosphere that we hope to find which we don’t really get just from the shorter, near-infrared wavelengths,” said Charles Beichman of NASA’s Jet Propulsion Laboratory in Pasadena, California, lead investigator of the NIRCam and MIRI observations of the HR 8799 system. “We’ll build on what the ground-based observatories have done, but the goal is to expand on that in a way that would be impossible without Webb.”

How Do Planets Form?

One of the researchers’ main goals in both systems is to use Webb to help determine how the exoplanets formed. Were they created through a buildup of material in the disk surrounding the star, enriched in heavy elements such as carbon, just as Jupiter probably did? Or, did they form from the collapse of a hydrogen cloud, like a star, and become smaller under the relentless pull of gravity?

Atmospheric makeup can provide clues to a planet’s birth. “One of the things we’d like to understand is the ratio of the elements that have gone into the formation of these planets,” Beichman said. “In particular, carbon versus oxygen tells you quite a lot about where the gas that formed the planet comes from. Did it come from a disk that accreted a lot of the heavier elements or did it come from the interstellar medium? So it’s what we call the carbon-to-oxygen ratio that is quite indicative of formation mechanisms.”

To answer these questions, the researchers will use Webb to probe deeper into the exoplanets’ atmospheres. NIRCam, for example, will measure the atmospheric fingerprints of elements like methane. It also will look at cloud features and the temperatures of these planets. “We already have a lot of information at these near-infrared wavelengths from ground-based facilities,” said Marshall Perrin of the Space Telescope Science Institute in Baltimore, Maryland, lead investigator of NIRCam observations of 51 Eridani b. “But the data from Webb will be much more precise, much more sensitive. We’ll have a more complete set of wavelengths, including filling in gaps where you can’t get those wavelengths from the ground.

Planets Orbiting HR 8799

This video shows four Jupiter-sized exoplanets orbiting billions of miles away from their star in the nearby HR 8799 system. The planetary system is oriented face-on toward Earth, giving astronomers a unique bird’s-eye view of the planets’ motion. The exoplanets are orbiting so far away from their star that they take anywhere from decades to centuries to complete an orbit. The video consists of seven images of the system taken over a seven-year period with the W.M. Keck Observatory on Mauna Kea, Hawaii. Keck’s coronagraph blocks out most of the starlight so that the much fainter and smaller exoplanets can be seen. Credits: Jason Wang (Caltech) and Christian Marois (NRC Herzberg)

The astronomers will also use Webb and its superb sensitivity to hunt for less-massive planets far from their star. “From ground-based observations, we know that these massive planets are relatively rare,” Perrin said. “But we also know that for the inner parts of systems, lower-mass planets are dramatically more common than larger-mass planets. So the question is, does it also hold true for these further separations out?” Beichman added, “Webb’s operation in the cold environment of space allows a search for fainter, smaller planets, impossible to detect from the ground.”

Another goal is understanding how the myriad planetary systems discovered so far were created.

“I think what we are finding is that there is a huge diversity in solar systems,” Perrin said. “You have systems where you have these hot Jupiter planets in very close orbits. You have systems where you don’t. You have systems where you have a 10-Jupiter-mass planet and ones in which you have nothing more massive than several Earths. We ultimately want to understand how the diversity of planetary system formation depends on the environment of the star, the mass of the star, all sorts of other things and eventually through these population-level studies, we hope to place our own solar system in context.

Planet Orbiting 51 Eridani

This video shows a Jupiter-sized exoplanet orbiting far away—roughly 11 billion miles—from a nearby, Sun-like star, 51 Eridani. The planetary system is oriented face-on toward Earth, giving astronomers a unique bird’s-eye view of the planet’s motion. The video consists of five images taken over four years with the Gemini South Telescope’s Gemini Planet Imager, in Chile. Gemini’s coronagraph blocks out most of the starlight so that the much fainter and smaller exoplanet can be seen. Credits: Jason Wang (Caltech)/Gemini Planet Imager Exoplanet Survey

The NIRSpec spectroscopic observations of HR 8799 and the NIRCam observations of 51 Eridani are part of the Guaranteed Time Observations programs that will be conducted shortly after Webb’s launch later this year. The NIRCam and MIRI observations of HR 8799 is a collaboration of two instrument teams and is also part of the Guaranteed Time Observations program.

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.

By Donna Weaver
Space Telescope Science Institute, Baltimore, Md. 

Media Contact:

Laura Betz
NASA's Goddard Space Flight Center, Greenbelt, Md.
laura.e.betz@nasa.gov

Editor: Lynn Jenner

Source: NASA/Solar System and Beyond

SCExAO/CHARIS Nets its First Discovery

Figure 1: Direct image of HD 33632 Ab with SCExAO/CHARIS. The companion (marked as "b") lies at a separation of about 20 AU from its star (located at the white cross), similar to the separations from the Sun to Uranus and Neptune in our solar system (Credit: T. Currie, NAOJ/NASA-Ames)

The Subaru Telescope's state-of-the-art exoplanet imaging system – the SCExAO adaptive optics module coupled with the CHARIS integral field spectrograph – has seen two full years of Open Use operation. Now, this new system has gained its first discovery and demonstrated a new approach to best selecting stars with imageable planets and other low-mass companions like brown dwarfs (failed stars).

The newly-discovered object, a brown dwarf named HD 33632 Ab, orbits a 1.5 billion year-old near-twin of the Sun star about 86 light-years from the Earth (Figure 1). It joins one of the few known imaged substellar companions orbiting Sun-like stars on solar system-like (Mercury-to-Pluto) scales. 

SCExAO/CHARIS data taken in October 2018 and complemented a month later by Keck Observatory data, revealed a detection of this object at a separation of about 20 AU (astronomical unit, the distance between the Sun and the Earth) from its host star. Follow-up, more intensive SCExAO/CHARIS data taken on August 31 and September 1 of this year, during the COVID-19 pandemic, confirmed that HD 33632 Ab exists and is a gravitationally bound companion, not an unrelated background star. The CHARIS spectrum for HD 33632 Ab has a jagged, sawtooth-like shape, indicative of water and carbon monoxide molecules (Figure 2 left).

"Thanks to SCExAO/CHARIS's incredibly sharp images, we can not only see HD 33632 Ab but get ultra-precise measurements for its position and its spectrum, which gives important clues about its atmospheric properties and its dynamics," said Thayne Currie, an affiliated researcher at Subaru, and lead author of this study.

Figure 2: Properties of HD 33632 Ab from SCExAO/CHARIS data. (left) The spectrum of HD 33632 Ab, which is shaped by absorption from water and carbon monoxide molecules in the companion's atmosphere. (right) Modeling the orbit of HD 33632 Ab and providing a direct constraint on the companion's mass. The thick black oval shows the best-fit orbit for HD 33632 Ab with open circles representing predicted locations of the companion; other thin ovals represent other possible orbits. The orbits are color-coded by the predicted mass of HD 33632 Ab. (Credit: T. Currie, NAOJ/NASA-Ames; T. Brandt, UCSB)

Unlike nearly all other faint directly-imaged companions, HD 33632 Ab has a directly determined mass instead of a mass inferred from uncertain models predicting a planet/brown dwarf's mass based on its brightness at a given age. All planets or brown dwarfs orbiting their host stars cause the star to accelerate towards it due to the force of gravity. The ultra-sensitive Gaia astrometry satellite and its predecessor astrometry mission (Hipparcos) revealed that the star around which HD 33632 Ab orbits (HD 33632 A) shows an acceleration hinting at the presence of some companion, which SCExAO/CHARIS has now imaged.

"This is the first time we have found a brown dwarf by looking around a star that is being tugged across the sky. Finding a brown dwarf always involves luck, but this time we were able to stack the odds," adds Timothy Brandt, assistant professor of physics at the University of California-Santa Barbara, coauthor, and expert on Gaia/Hipparcos astrometry data.

Modeling the Gaia/Hipparcos absolute astrometry for the star and astrometry for HD 33632 Ab from Keck and Subaru telescope data together provided a precise dynamical mass for the companion of ~46 Jupiter masses (Figure2 right). This mass is significantly higher than the limit usually thought to separate planets from brown dwarfs (13-14 Jupiter masses), although the object also has a low, more planet-like eccentricity.

HD 33632 Ab could be key reference point for understanding the atmospheres of the first imaged and best studied extrasolar planets, which orbit a star called HR 8799 and were discovered from Maunakea in 2008 and 2010. The HD 33632 system is much older than the youthful HR 8799 (40 million years old). While HD 33632 Ab is more massive than the HR 8799 planets and has a higher surface gravity, it likely has a temperature very similar to these planets. Furthermore, we have a direct mass measurement for HD 33632 Ab and also good constraints on the mass for the HR 8799 planets through other analyses. Thus, HD 33632 Ab and the HR 8799 planets together may provide a critical insight into how substellar atmospheres (planets and brown dwarfs) at a given temperature differ at a range of ages and gravities. Their mass measurements then allow us to directly link these observational differences to bulk properties, i.e., masses.

"The atmospheres of planets like HR 8799's are notoriously hard to understand and likely have very peculiar properties like thick clouds, which have proven hard to model. Having a good reference point like our SCExAO-discovered companion is crucial to understanding this and other objects much better," said Currie.

Finally, this program shows the power of approach to identifying stars that likely host imageable planets and brown dwarfs. Most direct imaging searches are 'blind' searches, targeting some subset of stars within some age range or within a common star forming region. Imaging surveys conducted with predecessor instruments like the Gemini Planet Imager on Gemini South telescope in Chile and SPHERE on the Very Large Telescope also in Chile show that the detection rate of companions with these blind surveys is very low (a few percent). The research team is carrying out a different kind of search. Specifically, they are focusing on stars, drawn from a carefully selected sample made by coauthor Timothy Brandt, that show an acceleration seen in Gaia data. This acceleration is indirect evidence that there is a massive orbiting companion that is tugging on the star. HD 33632 Ab's detection represents a proof-in-concept of this approach. While this survey has just started with SCExAO, the team already has identified multiple new candidate companions, with a detection rate significantly higher than from a blind approach.

"These observations could greatly expand the discoveries by the previous successful SEEDS survey with AO188 and HiCIAO. The SCExAO and CHARIS combination will keep the Subaru telescope at the forefront of the direct imaging of exoplanets and brown dwarfs," said Masayuki Kuzuhara and Motohide Tamura from the Astrobiology Center at the National Institutes of Natural Sciences.

Figure 3: SCExAO and CHARIS at the Nasmyth focus at the Subaru Telescope on Maunakea. Credit: Princeton University CHARIS team/NAOJ

This research was published in the Astrophysical Journal Letters on November 30, 2020 (Currie et al. "SCExAO/CHARIS Direct Imaging Discovery of a 20 au Separation, Low-Mass Ratio Brown Dwarf Companion to an Accelerating Sun-like Star".)

Relevant Links

• SCExAO/CHARIS Nets its First Discovery (Astrobiology Center December 11, 2020 press release)
• Direct Image of Newly-discovered Brown Dwarf Captured (W. M. Keck Observatory December 11, 2020 press release)

 

 Source: Subaru Telescope

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A Pair of Fledgling Planets Directly Seen Growing Around a Young Star

 Artist's illustration of exoplanets PDS 70 b and c

Credits:J. Olmsted (STScI)

 

Exoplanets PDS 70 b and c

Credits:  ESO and S. Haffert (Leiden Observatory)

Astronomers have directly imaged two exoplanets that are gravitationally carving out a wide gap within a planet-forming disk surrounding a young star. While over a dozen exoplanets have been directly imaged, this is only the second multi-planet system to be photographed. (The first was a four-planet system orbiting the star HR 8799.) Unlike HR 8799, though, the planets in this system are still growing by accreting material from the disk.

“This is the first unambiguous detection of a two-planet system carving a disk gap,” said Julien Girard of the Space Telescope Science Institute in Baltimore, Maryland.

The host star, known as PDS 70, is located about 370 light-years from Earth. The young 6-million-year-old star is slightly smaller and less massive than our Sun, and is still accreting gas. It is surrounded by a disk of gas and dust that has a large gap extending from about 1.9 to 3.8 billion miles.

PDS 70 b, the innermost known planet, is located within the disk gap at a distance of about 2 billion miles from its star, similar to the orbit of Uranus in our solar system. The team estimates that it weighs anywhere from 4 to 17 times as much as Jupiter. It was first detected in 2018.

PDS 70 c, the newly discovered planet, is located near the outer edge of the disk gap at about 3.3 billion miles from the star, similar to Neptune’s distance from our Sun. It is less massive than planet b, weighing between 1 and 10 times as much as Jupiter. The two planetary orbits are near a 2-to-1 resonance, meaning that the inner planet circles the star twice in the time it takes the outer planet to go around once.

The discovery of these two worlds is significant because it provides direct evidence that forming planets can sweep enough material out of a protoplanetary disk to create an observable gap.

“With facilities like ALMA, Hubble, or large ground-based optical telescopes with adaptive optics we see disks with rings and gaps all over. The open question has been, are there planets there? In this case, the answer is yes,” explained Girard.

The team detected PDS 70 c from the ground, using the MUSE spectrograph on the European Southern Observatory’s Very Large Telescope (VLT). Their new technique relied on the combination of the high spatial resolution provided by the 8-meter telescope equipped with four lasers and the instrument’s medium spectral resolution that allows it to “lock onto” light emitted by hydrogen, which is a sign of gas accretion.

“This new observing mode was developed to study galaxies and star clusters at higher spatial resolution. But this new mode also makes it suitable for exoplanet imaging, which was not the original science driver for the MUSE instrument,” said Sebastiaan Haffert of Leiden Observatory, lead author on the paper.

“We were very surprised when we found the second planet,” Haffert added.

In the future, NASA’s James Webb Space Telescope may be able to study this system and other planet nurseries using a similar spectral technique to narrow in on various wavelengths of light from hydrogen. This would allow scientists to measure the temperature and density of gas within the disk, which would help our understanding of the growth of gas giant planets. The system might also be targeted by the WFIRST mission, which will carry a high-performance coronagraph technology demonstration that can block out the star’s light to reveal fainter light from the surrounding disk and companion planets.

These results were published in the June 3 issue of Nature Astronomy.

Source:  HubbleSite/News

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GRAVITY instrument breaks new ground in exoplanet imaging

PR Image eso1905a

GRAVITY instrument breaks new ground in exoplanet imaging 

PR Image eso1905b

HR 8799 in the constellation Pegasus

PR Image eso1905c

Surroundings of the star HR 8799 

PR Image eso1905d

Aerial view of the VLTI with tunnels superimposed 

PR Image eso1905e

VLT interferometer principle

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Videos

PR Video eso1905a

ESOcast 197 Light: GRAVITY uncovers stormy exoplanet skies

PR Video eso1905b

Orbital motion of the HR8799 system

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Cutting-edge VLTI instrument reveals details of a storm-wracked exoplanet using optical interferometry

The GRAVITY instrument on ESO’s Very Large Telescope Interferometer (VLTI) has made the first direct observation of an exoplanet using optical interferometry. This method revealed a complex exoplanetary atmosphere with clouds of iron and silicates swirling in a planet-wide storm. The technique presents unique possibilities for characterising many of the exoplanets known today.

This result was announced today in a letter in the journal Astronomy and Astrophysics by the GRAVITY Collaboration [1], in which they present observations of the exoplanet HR8799e using optical interferometry. The exoplanet was discovered in 2010 orbiting the young main-sequence star HR8799, which lies around 129 light-years from Earth in the constellation of Pegasus.

Today’s result, which reveals new characteristics of HR8799e, required an instrument with very high resolution and sensitivity. GRAVITY can use ESO’s VLT’s four unit telescopes to work together to mimic a single larger telescope using a technique known as interferometry [2]. This creates a super-telescope — the VLTI  — that collects and precisely disentangles the light from HR8799e’s atmosphere and the light from its parent star [3].

HR8799e is a ‘super-Jupiter’, a world unlike any found in our Solar System, that is both more massive and much younger than any planet orbiting the Sun. At only 30 million years old, this baby exoplanet is young enough to give scientists a window onto the formation of planets and planetary systems. The exoplanet is thoroughly inhospitable — leftover energy from its formation and a powerful greenhouse effect heat HR8799e to a hostile temperature of roughly 1000 °C.

This is the first time that optical interferometry has been used to reveal details of an exoplanet, and the new technique furnished an exquisitely detailed spectrum of unprecedented quality — ten times more detailed than earlier observations. The team’s measurements were able to reveal the composition of HR8799e’s atmosphere  — which contained some surprises.

“Our analysis showed that HR8799e has an atmosphere containing far more carbon monoxide than methane — something not expected from equilibrium chemistry,” explains team leader Sylvestre Lacour researcher CNRS at the Observatoire de Paris - PSL and the Max Planck Institute for Extraterrestrial Physics. “We can best explain this surprising result with high vertical winds within the atmosphere preventing the carbon monoxide from reacting with hydrogen to form methane.”

The team found that the atmosphere also contains clouds of iron and silicate dust. When combined with the excess of carbon monoxide, this suggests that HR8799e’s atmosphere is engaged in an enormous and violent storm.

“Our observations suggest a ball of gas illuminated from the interior, with rays of warm light swirling through stormy patches of dark clouds,” elaborates Lacour. “Convection moves around the clouds of silicate and iron particles, which disaggregate and rain down into the interior. This paints a picture of a dynamic atmosphere of a giant exoplanet at birth, undergoing complex physical and chemical processes.”

This result builds on GRAVITY’s string of impressive discoveries, which have included breakthroughs such as last year’s observation of gas swirling at 30% of the speed of light just outside the event horizon of the massive Black Hole in the Galactic Centre. It also adds a new way of observing exoplanets to the already extensive arsenal of methods available to ESO’s telescopes and instruments — paving the way to many more impressive discoveries [4].

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Notes

[1] GRAVITY was developed by a collaboration consisting of the Max Planck Institute for Extraterrestrial Physics (Germany), LESIA of Paris Observatory–PSL / CNRS / Sorbonne Université / Univ. Paris Diderot and IPAG of Université Grenoble Alpes / CNRS (France), the Max Planck Institute for Astronomy (Germany), the University of Cologne (Germany), the CENTRA–Centro de Astrofisica e Gravitação (Portugal) and ESO.

[2] Interferometry is a technique that allows astronomers to create a super-telescope by combining several smaller telescopes. ESO’s VLTI is an interferometric telescope created by combining two or more of the Unit Telescopes (UTs) of the Very Large Telescope or all four of the smaller Auxiliary Telescopes. While each UT has an impressive 8.2-m primary mirror, combining them creates a telescope with 25 times more resolving power than a single UT observing in isolation.

[3] Exoplanets can be observed using many different methods. Some are indirect, such as the radial velocity method used by ESO’s exoplanet-hunting HARPS instrument, which measures the pull a planet’s gravity has on its parent star. Direct methods, like the technique pioneered for this result, involve observing the planet itself instead of its effect on its parent star.

[4] Recent exoplanet discoveries made using ESO telescopes include last year’s successful detection of a super-Earth orbiting Barnard’s Star, the closest single star to our Sun, and ALMA’s discovery of young planets orbiting an infant star, which used another novel technique for planet detection.

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More Information

This research was presented in the paper “First direct detection of an exoplanet by optical interferometry” in Astronomy and Astrophysics.

The team was composed of :  S. Lacour (LESIA, Observatoire de Paris - PSL, CNRS, Sorbonne Universités, UPMC Univ. Paris 06, Univ. Paris Diderot, Meudon, France [LESIA]; Max Planck Institute for Extraterrestrial Physics, Garching, Germany [MPE]), M. Nowak (LESIA), J. Wang (Department of Astronomy, California Institute of Technology, Pasadena, USA), O. Pfuhl (MPE), F. Eisenhauer (MPE), R. Abuter (ESO, Garching, Germany), A. Amorim (Universidade de Lisboa, Lisbon, Portugal; CENTRA - Centro de Astrofísica e Gravitação, IST, Universidade de Lisboa, Lisbon, Portugal), N. Anugu (Faculdade de Engenharia, Universidade do Porto, Porto, Portugal; School of Physics, Astrophysics Group, University of Exeter, Exeter, United Kingdom), M. Benisty (Univ. Grenoble Alpes, CNRS, IPAG, Grenoble, France [IPAG]), J.P. Berger (IPAG), H. Beust (IPAG), N. Blind (Observatoire de Genève, Université de Genève, Versoix, Switzerland), M. Bonnefoy (IPAG), H. Bonnet (ESO, Garching, Germany), P. Bourget (ESO, Santiago, Chile), W. Brandner (Max Planck Institute for Astronomy, Heidelberg, Germany [MPIA]), A. Buron (MPE), C. Collin (LESIA), B. Charnay (LESIA), F. Chapron (LESIA) , Y. Clénet (LESIA), V. Coudé du Foresto (LESIA), P.T. de Zeeuw (MPE; Sterrewacht Leiden, Leiden University, Leiden, The Netherlands), C. Deen (MPE), R. Dembet (LESIA), J. Dexter (MPE), G. Duvert (IPAG), A. Eckart (1st Institute of Physics, University of Cologne, Cologne, Germany;  Max Planck Institute for Radio Astronomy, Bonn, Germany), N.M. Förster Schreiber (MPE), P. Fédou (LESIA), P. Garcia (Faculdade de Engenharia, Universidade do Porto, Porto, Portugal; ESO, Santiago, Chile; CENTRA - Centro de Astrofísica e Gravitação, IST, Universidade de Lisboa, Lisbon, Portugal), R. Garcia Lopez (Dublin Institute for Advanced Studies, Dublin, Ireland; MPIA), F. Gao (MPE), E. Gendron (LESIA), R. Genzel (MPE; Departments of Physics and Astronomy, University of California, Berkeley, USA), S. Gillessen (MPE), P. Gordo (Universidade de Lisboa, Lisbon, Portugal; CENTRA - Centro de Astrofísica e Gravitação, IST, Universidade de Lisboa, Lisbon, Portugal), A. Greenbaum (Department of Astronomy, University of Michigan, Ann Arbor, USA), M. Habibi (MPE), X. Haubois (ESO, Santiago, Chile), F. Haußmann (MPE), Th. Henning (MPIA), S. Hippler (MPIA), M. Horrobin (1st Institute of Physics, University of Cologne, Cologne, Germany), Z. Hubert (LESIA), A. Jimenez Rosales (MPE), L. Jocou (IPAG), S. Kendrew (European Space Agency, Space Telescope Science Institute, Baltimore, USA; MPIA), P. Kervella (LESIA), J. Kolb (ESO, Santiago, Chile), A.-M. Lagrange (IPAG), V. Lapeyrère (LESIA), J.-B. Le Bouquin (IPAG), P. Léna (LESIA), M. Lippa (MPE), R. Lenzen (MPIA), A.-L. Maire (STAR Institute, Université de Liège, Liège, Belgium; MPIA), P. Mollière (Sterrewacht Leiden, Leiden University, Leiden, The Netherlands), T. Ott (MPE), T. Paumard (LESIA), K. Perraut (IPAG), G. Perrin (LESIA), L. Pueyo (Space Telescope Science Institute, Baltimore, USA), S. Rabien (MPE), A. Ramírez (ESO, Santiago, Chile), C. Rau (MPE), G. Rodríguez-Coira (LESIA), G. Rousset (LESIA), J. Sanchez-Bermudez (Instituto de Astronomía, Universidad Nacional Autónoma de México, Mexico City, Mexico; MPIA), S. Scheithauer (MPIA), N. Schuhler (ESO, Santiago, Chile), O. Straub (LESIA; MPE), C. Straubmeier (1st Institute of Physics, University of Cologne, Cologne, Germany), E. Sturm (MPE), L.J. Tacconi (MPE), F. Vincent (LESIA), E.F. van Dishoeck (MPE; Sterrewacht Leiden, Leiden University, Leiden, The Netherlands), S. von Fellenberg (MPE), I. Wank (1st Institute of Physics, University of Cologne, Cologne, Germany), I. Waisberg (MPE) , F. Widmann (MPE), E. Wieprecht (MPE), M. Wiest (1st Institute of Physics, University of Cologne, Cologne, Germany), E. Wiezorrek (MPE), J. Woillez (ESO, Garching, Germany), S. Yazici (MPE; 1st Institute of Physics, University of Cologne, Cologne, Germany), D. Ziegler (LESIA), and G. Zins (ESO, Santiago, Chile).

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It has 16 Member States: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Ireland, 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. Also at Paranal ESO will host and operate the Cherenkov Telescope Array South, the world’s largest and most sensitive gamma-ray observatory. 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

• Research paper 
• Photos of GRAVITY
• Photos of the VLT

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Contacts

Sylvestre Lacour
CNRS/LESIA, Observatoire de Paris - PSL
5 place Jules Janssen, Meudon, France
Tel: +33 6 81 92 53 89
Email: Sylvestre.lacour@observatoiredeparis.psl.eu

Mathias Nowak
CNRS/LESIA, Observatoire de Paris - PSL
5 place Jules Janssen, Meudon, France
Tel: +33 1 45 07 76 70
Cell: +33 6 76 02 14 48
Email: Mathias.nowak@observatoiredeparis.psl.eu

Dr. Paul Mollière
Sterrewacht Leiden, Huygens Laboratory
Leiden, The Netherlands
Tel: +31 64 2729185
Email: molliere@strw.leidenuniv.nl

Calum Turner
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6670
Email: pio@eso.org

Source: ESO/News

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NRAO Media Tip Sheet: May 2016

ALMA image of dusty cometary ring around HR 8799, the only star where multiple planets have been imaged. The new data suggest the planets either migrated or another undiscovered planet is present. The zoom-in portion of the image, taken with ESO's Very Large Telescope, shows the location of the known planets in this system in relation to a graphical representation of the central star. Credit: Booth et al., ALMA (NRAO/ESO/NAOJ); A. Zurlo, et al.

VLBA image of Compact Symmetric Object J13262+3152, called "an archetypical example" of such an object.

Credit: Tremblay, et al., NRAO/AUI/NSF

Patent for surface treatment for self-calibrating radiometer awarded to NRAO engineer Galen Watts.

Credit: NRAO/AUI/NSF

NRAO engineers Tod Boyd and Matt Morgan, recipients of the 2015 IEEE Antenna and Propagation Society Harold A. Wheeler Applications Prize Paper Award. Credit: NRAO/AUI/NSF

1. Cometary Belt around Distant Multi-planet System Hints at Hidden or Wandering Planets

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have made the first high-resolution image of the cometary belt (a region analogous to our own Kuiper belt) around HR 8799, the only star where multiple planets have been imaged directly. The shape of this dusty disk, particularly its inner edge, is surprisingly inconsistent with the orbits of the planets, suggesting that either they changed position over time or there is at least one more planet in the system yet to be discovered. "These data really allow us to see the inner edge of this disk for the first time," explains Mark Booth from Pontificia Universidad Católica de Chile and lead author of the study. "By studying the interactions between the planets and the disk, this new observation shows that either the planets that we see have had different orbits in the past or there is at least one more planet in the system that is too small to have been detected." The disk, which fills a region 150 to 420 times the Sun-Earth distance, is produced by the ongoing collisions of cometary bodies in the outer reaches of this star system. ALMA was able to image the emission from millimeter-size debris in the disk; according to the researchers, the small size of these dust grains suggests that the planets in the system are larger than Jupiter. Previous observations with other telescopes at shorter wavelengths did not detect this discrepancy in the disk. It is not clear if this difference is due to the low resolution of the previous observations or because different wavelengths are sensitive to different grain sizes, which would be distributed slightly differently. HR 8799 is a young star approximately 1.5 times the mass of the Sun located 129 light-years from Earth in the direction of the constellation Pegasus. "This is the very first time that a multi-planet system with orbiting dust is imaged, allowing for direct comparison with the formation and dynamics of our own Solar System," explains Antonio Hales, co-author of the study from the National Radio Astronomy Observatory in Charlottesville, Va. The astronomers are reporting their results in the Monthly Notices of the Royal Astronomical Society.

Reference: "Resolving the Planetesimal Belt of HR 8799 with ALMA," Booth et al.; Monthly Notices of the Royal Astronomical Society [http://dx.doi.org/10.1093/mnrasl/slw040], May 2016. Preprint: http://arxiv.org/abs/1603.04853

2. VLBA Study Doubles Sample of Youngest Radio Galaxies

Astronomers using the National Science Foundation's Very Long Baseline Array (VLBA) have found 15 new examples of a rare type of object that may yield valuable clues about how radio-emitting galaxies and their environments evolve in their early stages of development. The objects, called compact symmetric objects (CSOs), are small, young versions of the supermassive black hole-powered "engines" that propel fast-moving jets of material outward from radio galaxies. Following up on a large-scale VLBA survey done in 2006, the scientists made more-detailed observations of objects they identified as possible CSOs. Of 103 such candidates, they confirmed 24, 15 of which are newly identified as CSOs. Using McDonald Observatory's Hobby-Eberly Telescope, they determined distances to some of the objects, which allowed them to measure the objects' sizes. "This doubles the number of these objects known," said Steven Tremblay, of Curtin University in Australia. Enlarging the sample of known CSOs, the astronomers said, can be a big help to understanding radio galaxies in general. With sizes as small as 5 light-years across, and ages from only 20 to 2,000 years, CSOs represent an important early stage in the development of the much larger and older radio-emitting galaxies. Even at this early stage, the scientists said the CSOs in their sample show a distinction between higher-powered and lower-powered objects that also typifies older radio galaxies. "Understanding these young objects is vital to understanding their larger cousins," said Greg Taylor, of the University of New Mexico. The astronomers are reporting their results in the Monthly Notices of the Royal Astronomical Society.

Reference: "Compact Symmetric Objects and Supermassive Binary Black Holes in the VLBA Imaging and Polarimetry Survey," Tremblay et al.; Monthly Notices of the Royal Astronomical Society, May 2016. Preprint: http://arxiv.org/abs/1603.03094

3. Innovation from NRAO Engineer Yields New Patent

Galen Watts, an engineer at the National Radio Astronomy Observatory's Green Bank Microwave Electronics Group, received a patent (U.S. Patent Number: 9,343,815) for a surface treatment application for radiometers that aids in their self-calibration. Radiometers are devices that measure the actual energy of microwaves and other forms of electromagnetic radiation. Radio astronomers and other researchers use microwave radiometry to discover the molecular and atomic composition as well as the temperature of many objects on Earth and even the most distant celestial objects. They do this by examining the content of these objects’ naturally emitted microwave signals. To make accurate readings, however, a radiometer has to be properly calibrated. The new surface treatment application, developed by Watts, aids in radiometer self-calibration by reflecting an image of the feed horn back onto itself in a manner that doesn't set up standing waves. Similar applications could also be useful for reducing antenna side-lobes (extraneous readings in radio astronomy), reducing radar cross-sections of objects, and eliminating resonances from stray reflections in quasi-optical component assemblies.

4. NRAO Engineers Receive IEEE Antenna and Propagation Society Award

NRAO engineers Mathew A. Morgan and Tod A. Boyd have been awarded jointly the 2015 IEEE Antenna and Propagation Society Harold A. Wheeler Applications Prize Paper Award, which is presented to the authors of the best applications paper published in the IEEE Transactions on Antennas and Propagation during the previous year. Their paper, "A 10-100 GHz Double-Ridged Horn Antenna and Coax Launcher," was published in August 2015 and reports on the development of a novel radio antenna. It is described as an ultra-wideband, double-ridged horn antenna with a bandwidth that covers a ten-fold range in frequencies. This is believed to be the first such decade-bandwidth horn in the millimeter-wave frequency range, covering -- in this case -- 10-100 GHz. Such horns can be used for test and measurement applications, including material characterization. It was originally designed as a scale model for an even higher-frequency horn covering 100 GHz - 1 THz. For this award, they will each receive a certificate and share in the $1,000 honorarium. The award will be presented at the IEEE APS/URSI Symposium Awards Ceremony, June 29, 2016, in Fajardo, Puerto Rico.

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

ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), NSC and ASIAA (Taiwan), and KASI (Republic of South Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ.

Contacts:

Charles Blue, Public Information Officer
(434) 296-0314; cblue@nrao.edu

Dave Finley, Public Information Officer
(575) 835-7302; dfinley@nrao.edu

Source: National Radio Astronomy Observatory (NRAO)

Gemini Observatory / University of Hawai‘i, Institute for Astronomy

Artist's rendering of a possible exoplanetary system with a gas-giant planet orbiting close to his parent star which is more massive than our sun. 

Artwork by Lynette Cook

Credit: Gemini Observatory/AURA.  Full Resolution TIFF (6MB) | Full Resolution JPEG (2MB) | Medium Resolution JPEG (296KB)

Gemini Observatory’s Planet-Finding Campaign finds that, around many types of stars, distant gas-giant planets are rare and prefer to cling close to their parent stars. The impact on theories of planetary formation could be significant.

Finding extrasolar planets has become so commonplace that it seems astronomers merely have to look up and another world is discovered. However, results from Gemini Observatory’s recently completed Planet-Finding Campaign – the deepest, most extensive direct imaging survey to date – show the vast outlying orbital space around many types of stars is largely devoid of gas-giant planets, which apparently tend to dwell close to their parent stars.

“It seems that gas-giant exoplanets are like clinging offspring,” says Michael Liu of the University of Hawaii’s Institute for Astronomy and leader of the Gemini Planet-Finding Campaign. “Most tend to shun orbital zones far from their parents. In our search, we could have found gas giants beyond orbital distances corresponding to Uranus and Neptune in our own Solar System, but we didn’t find any.” The Campaign was conducted at the Gemini South telescope in Chile, with funding support for the team from the National Science Foundation and NASA. The Campaign’s results, Liu says, will help scientists better understand how gas-giant planets form, as the orbital distances of planets are a key signature that astronomers use to test exoplanet formation theories.

Eric Nielsen of the University of Hawaii, who leads a new paper about the Campaign’s search for planets around stars more massive than the Sun, adds that the findings have implications beyond the specific stars imaged by the team. "The two largest planets in our Solar System, Jupiter and Saturn, are huddled close to our Sun, within 10 times the distance between the Earth and Sun,” he points out. “We found that this lack of gas-giant planets in more distant orbits is typical for nearby stars over a wide range of masses."

Two additional papers from the Campaign will be published soon and reveal similar tendencies around other classes of stars. However, not all gas-giant exoplanets snuggle so close to home. In 2008, astronomers using the Gemini North telescope and W.M. Keck Observatory on Hawaii’s Mauna Kea took the first-ever direct images of a family of planets around the star HR 8799, finding gas-giant planets at large orbital separations (about 25-70 times the Earth-Sun distance). This discovery came after examining only a few stars, suggesting such large-separation gas giants could be common. The latest Gemini results, from a much more extensive imaging search, show that gas-giant planets at such distances are in fact uncommon.

Liu sums up the situation this way: “We’ve known for nearly 20 years that gas-giant planets exist around other stars, at least orbiting close-in. Thanks to leaps in direct imaging methods, we can now learn how far away planets can typically reside. The answer is that they usually avoid significant areas of real estate around their host stars. The early findings, like HR 8799, probably skewed our perceptions.”

The team’s second new paper explores systems where dust disks around young stars show holes, which astronomers have long suspected are cleared by the gravitational force of orbiting planets. “It makes sense that where you see debris cleared away that a planet would be responsible, but we did not know what types of planets might be causing this. It appears that instead of massive planets, smaller planets that we can’t detect directly could be responsible,” said Zahed Wahhaj of the European Southern Observatory and lead author on the survey’s paper on dusty disk stars. Finally, the third new paper from the team looks at the very youngest stars close to Earth. “A younger system should have brighter, easier to detect planets,” according to the lead author Beth Biller of the Max Planck Institute for Astronomy.

“Around other stars, NASA's Kepler telescope has shown that planets larger than the Earth and within the orbit of Mercury are plentiful,” explains Biller. “The NICI Campaign demonstrates that gas-giant planets beyond the distance of the orbit of Neptune are rare.” The soon-to-be-delivered Gemini Planet Imager will begin to bridge this gap likely revealing, for the first time, how common giant planets are in orbits similar to the gas-giant planets of our own Solar System.

The observations for the Campaign were obtained with the Gemini instrument known as NICI, the Near-Infrared Coronagraphic Imager, which was the first instrument for an 8-10 meter-class telescope designed specifically for finding faint companions around bright stars. NICI was built by Doug Toomey (Mauna Kea Infrared), Christ Ftaclas, and Mark Chun (University of Hawai‘i), with funding from NASA.

The first two papers from the Campaign have been accepted for publication in The Astrophysical Journal (Nielsen et al. and Wahhaj et al.), and the third paper (Biller et al.) will be published later this summer.

The NICI Campaign team is composed of PI Michael Liu, co-PI Mark Chun (University of Hawaii), co-PI Laird Close (University of Arizona), Doug Toomey (Mauna Kea Infrared), Christ Ftaclas (University of Hawaii), Zahed Wahhaj (European Southern Observatory), Beth Biller (Max Planck Institute for Astronomy), Eric Nielsen (University of Hawaii), Evgenya Shkolnik (DTM, Carnegie Institution of Washington), Adam Burrows (Princeton University), Neill Reid (Space Telescope Science Institute), Niranjan Thatte, Matthias Tecza, Fraser Clarke (University of Oxford), Jane Gregorio Hetem, Elisabete De Gouveia Dal Pino (University of Sao Paolo), Silvia Alencar (University of Minas Gerais), Pawel Artymowicz (University of Toronto), Doug Lin (University of California Santa Cruz), Shigeru Ida (Tokyo Institute of Technology), Alan Boss (DTM, Carnegie Institution of Washington), and Mark Kuchner (NASA Goddard), Tom Hayward and Markus Hartung (Gemini Observatory), Jared Males, and Andy Skemer (University of Arizona).

Media Contacts:

• Peter Michaud
  Gemini Observatory
  Hilo, HI 96720
  Office: +1 (808) 974-2510
  Cell: +1 (808) 936-6643
  pmichaud@gemini.edu

• Roy Gal
  Institute for Astronomy
  University of Hawaii at Manoa
  Honolulu, HI 96822
  Office: +1 (808) 956-6235
  rgal@ifa.hawaii.edu

Science Contacts:

• Michael Liu
  Institute for Astronomy
  University of Hawaii at Manoa
  Honolulu, HI 96822
  Office: +1 (808) 956-6666
  mliu@ifa.hawaii.edu

• Eric Nielsen
  Institute for Astronomy
  University of Hawaii at Manoa
  Honolulu, HI 96822
  Office: +1 (808) 956-9841
  Cell: 408 394-4582
  enielsen@ifa.hawaii.edu

Source: Gemini Observatory

The Gemini Planet Imager Produces Stunning Observations in Its First Year

Figure 1. GPI imaging of the planetary system HR 8799 in K band, showing 3 of the 4 planets. (Planet b is outside the field of view shown here, off to the left.) These data were obtained on November 17, 2013 during the first week of operation of GPI and in relatively challenging weather conditions, but with GPI’s advanced adaptive optics system and coronagraph the planets can still be clearly seen and their spectra measured (see Figure 2). Image credit: Christian Marois (NRC Canada), Patrick Ingraham (Stanford University) and the GPI Team.  Full-resolution image

Figure 2. GPI spectroscopy of planets c and d in the HR 8799 system. While earlier work showed that the planets have similar overall brightness and colors, these newly-measured spectra show surprisingly large differences. The spectrum of planet d increases smoothly from 1.9-2.2 microns while planet c’s spectrum shows a sharper kink upwards just beyond 2 microns. These new GPI results indicate that these similar-mass and equal-age planets nonetheless have significant differences in atmospheric properties, for in-stance more open spaces between patchy cloud cover on planet c versus uniform cloud cover on planet d, or perhaps differences in atmospheric chemistry. These data are helping refine and improve a new generation of atmospheric models to explain these effects. Image credit: Patrick Ingraham (Stanford University), Mark Marley (NASA Ames), Didier Saumon (Los Alamos National Laboratory) and the GPI Team.  Full-resolution image

Figure 3. GPI imaging polarimetry of the circumstellar disk around HR 4796A, a ring of dust and planetesimals similar in some ways to a scaled up version of the solar system’s Kuiper Belt. These GPI observations reveal a complex pattern of variations in brightness and polarization around the HR 4796A disk. The western side (tilted closer to the Earth) appears brighter in polarized light, while in total intensity the eastern side appears slightly brighter, particularly just to the east of the widest apparent separation points of the disk. Reconciling this complex and apparently-contradictory pattern of brighter and darker regions required a major overhaul of our understanding of this circumstellar disk. Image credit: Marshall Perrin (Space Telescope Science Institute), Gaspard Duchene (UC Berkeley), Max Millar-Blanchaer (University of Toronto), and the GPI Team.  Full-resolution image

Figure 4. Diagram depicting the GPI team's revised model for the orientation and composition of the HR 4796A ring. To explain the observed polarization levels, the disk must consist of relatively large (> 5 µm) silicate dust particles, which scatter light most strongly and polarize it more for forward scattering. To explain the relative faintness of the east side in total intensity, the disk must be dense enough to be slightly opaque, comparable to Saturn’s optically thick rings, such that on the near side of the disk our view of its brightly illuminated inner portion is partially obscured. This revised model requires the disk to be much narrower and flatter than expected, and poses a new challenge for theories of disk dynamics to explain. GPI’s high contrast imaging and polarimetry capabilities together were essential for this new synthesis. Image credit: Marshall Perrin (Space Telescope Science Institute).  Full-resolution image

Stunning exoplanet images and spectra from the first year of science operations with the Gemini Planet Imager (GPI) were featured today in a press conference at the 225th meeting of the American Astronomical Society (AAS) in Seattle, Washington. The Gemini Planet Imager GPI is an advanced instrument designed to observe the environments close to bright stars to detect and study Jupiter-like exoplanets (planets around other stars) and see protostellar material (disk, rings) that might be lurking next to the star. 

Marshall Perrin (Space Telescope Science Institute), one of the instrument’s team leaders, presented a pair of recent and promising results at the press conference. He revealed some of the most detailed images and spectra ever of the multiple planet system HR 8799. His presentation also included never-seen details in the dusty ring of the young star HR 4796A. “GPI’s advanced imaging capabilities have delivered exquisite images and data,” said Perrin. “These improved views are helping us piece together what’s going on around these stars, yet also posing many new questions.” 

The GPI spectra obtained for two of the planetary members of the HR 8799 system presents a challenge for astronomers. GPI team member Patrick Ingraham (Stanford University), lead the paper on HR 8799. Ingraham reports that the shape of the spectra for the two planets differ more profoundly than expected based on their similar colors, indicating significant differences between the companions. “Current atmospheric models of exoplanets cannot fully explain the subtle differences in color that GPI has revealed. We infer that it may be differences in the coverage of the clouds or their composition.” Ingraham adds, "The fact that GPI was able to extract new knowledge from these planets on the first commissioning run in such a short amount of time, and in conditions that it was not even designed to work, is a real testament to how revolutionary GPI will be to the field of exoplanets." 

Perrin, who is working to understand the dusty ring around the young star HR 4796A, said that the new GPI data present an unprecedented level of detail in studies of the ring’s polarized light. “GPI not only sees the disk more clearly than previous instruments, it can also measure how polarized its light appears, which has proven crucial in under-standing its physical properties.” Specifically, the GPI measurements of the ring show it must be partially opaque, implying it is far denser and more tightly compressed than similar dust found in the outskirts of our own Solar System, which is more diffuse. The ring circling HR 4796A is about twice the diameter of the planetary orbits in our Solar System and its star about twice our Sun’s mass. “These data taken during GPI commissioning show how exquisitely well its polarization mode works for studying disks. Such observations are critical in advancing our understanding of all types and sizes of planetary systems – and ultimately how unique our own solar system might be,” said Perrin. 

During the commissioning phase, the GPI team observed a variety of targets, ranging from asteroids in our solar system, to an old star near its death. Other teams of scientists have been using GPI as well and already astronomers around the world have published eight papers in peer-reviewed journals using GPI data. “This might be the most productive new instrument Gemini has ever had,” said Professor James Graham of the University of California, who leads the GPI science team and who will describe the GPI exoplanet survey (see below) in a talk scheduled at the AAS meeting on Thursday, January 8th. 

The Gemini Observatory staff integrated the complex instrument into the telescope’s software and helped to characterize GPI’s performance. “Even though it’s so complicated, GPI now operates almost automatically,” said Gemini’s instrument scientist for GPI Fredrik Rantakyro. “This allows us to start routine science operations.” The instrument is now available to astronomers and their proposals are scheduled to start ob-serving in early 2015. In addition, “shared risk” observations are already underway, starting in November 2014. 

The one thing GPI hasn’t done yet is discovered a new planet. “For the early tests, we concentrated on known planets or disks” said GPI PI Bruce Macintosh. Now that GPI is fully operational, the search for new planets has begun. In addition to observations by astronomers world-wide, the Gemini Planet Imager Exoplanet Survey (GPIES) will look at 600 carefully selected stars over the next few years. GPI ‘sees’ planets through the infrared light they emit when they’re young, so the GPIES team has assembled a list of the youngest and closest stars. So far the team has observed 50 stars, and analysis of the data is ongoing. Discovering a planet requires confirmation observations to distinguish a true planet orbiting the target star from a distant star that happens to sneak into GPI’s field of view - a process that could take years with previous instruments. The GPIES team found one such object in their first survey run, but GPI observations were sensitive enough to almost immediately rule it out. Macintosh said, “With GPI, we can tell almost instantly that something isn’t a planet – rather than months of uncertainty, we can get over our disappointment almost immediately. Now it’s time to find some real planets!” 

About GPI/GPIES

 

The Gemini Planet Imager (GPI) instrument was constructed by an international collaboration led by Lawrence Livermore National Laboratory under Gemini’s supervision. The GPI Exoplanet Survey (GPIES) is the core science program to be carried out with it. GPIES is led by Bruce Macintosh, now a professor at Stanford University and James Graham, professor at the University of California at Berkeley and is designed to find young, Jupiter-like exoplanets. They survey will observe 600 young nearby stars in 890 hours over three years. Targets have been carefully selected by team members at Arizona State University, the University of Georgia, and UCLA. The core of the data processing architecture is led by Marshall Perrin of the Space Telescope Science Institute, with the core software originally written by University of Montreal, data management infrastructure from UC Berkeley and Cornell University, and contributions from all the other team institutions. The SETI institute located in California manages GPIES’s communications and public out-reach. Several teams located at the Dunlap Institute, the University of Western Ontario, the University of Chicago, the Lowell Observatory, NASA Ames, the American Museum of Natural History, University of Arizona and the University of California at San Diego and at Santa Cruz also contribute to the survey. The GPI Exoplanet Survey is supported by the NASA Origins Program NNX14AG80, the NSF AAG pro-gram, and grants from other institutions including the University of California Office of the President. Dropbox Inc. has generously provided storage space for the entire survey's archive. 

Media Contacts:

• Peter Michaud
  Public Information and Outreach Manager
  Gemini Observatory, Hilo, HI
  Email: pmichaud@gemini.edu
  Cell: (808) 936-6643
  Desk: (808) 974-2510

Science Contacts:

• Marshall Perrin
  STScI
  Email: mperrin@stsci.edu
  Phone: (410) 507-5483

• James R. Graham
  University of California Berkeley
  Email: jrg@berkeley.edu
  Cell: (510) 926-9820

Source: Gemini Observatory