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  • richardmitnick 1:50 pm on May 13, 2018 Permalink | Reply
    Tags: , , , , , , , , , Transit spectroscopy   

    From ASU via Science News: “The recipes for solar system formation are getting a rewrite” 

    ASU Bloc

    From Arizona State University


    Science News

    May 11, 2018
    Lisa Grossman

    Exoplanets: Left to right Kepler-22b, Kepler-69c, Kepler-62e, Kepler-62f, with Earth-except for Earth these are artists’ concepts. Image credit: NASA Ames/ JPL-Caltech

    With a mortar and pestle, Christy Till blends together the makings of a distant planet. In her geology lab at Arizona State University in Tempe, Till carefully measures out powdered minerals, tips them into a metal capsule and bakes them in a high-pressure furnace that can reach close to 35,000 times Earth’s atmospheric pressure and 2,000° Celsius.

    In this interplanetary test kitchen, Till and colleagues are figuring out what might go into a planet outside of our solar system.

    “We’re mixing together high-purity powders of silica and iron and magnesium in the right proportions to make the composition we want to study,” Till says. She’s starting with the makings of what might resemble a rocky planet that’s much different from Earth. “We literally make a recipe.”

    Scientists have a few good ideas for how to concoct our own solar system. One method: Mix up a cloud of hydrogen and helium, season generously with oxygen and carbon, and sprinkle lightly with magnesium, iron and silicon. Condense and spin until the cloud forms a star surrounded by a disk. Let rest about 10 million years, until a few large lumps appear. After about 600 million years, shake gently.

    1
    GET COOKING Geologist Christy Till mixes up a mock exoplanet from powdered minerals in her Arizona lab. Abigail Weibel Photography

    But that’s only one recipe in the solar systems cookbook. Many of the planets orbiting other stars are wildly different from anything seen close to home. As the number of known exoplanets has climbed — 3,717 confirmed as of April 12 — scientists are creating new recipes.

    Seven of those exoplanets are in the TRAPPIST-1 system, one of the most exciting families of planets astronomers have discovered to date.

    A size comparison of the planets of the TRAPPIST-1 system, lined up in order of increasing distance from their host star. The planetary surfaces are portrayed with an artist’s impression of their potential surface features, including water, ice, and atmospheres. NASA


    The TRAPPIST-1 star, an ultracool dwarf, is orbited by seven Earth-size planets (NASA).

    At least three TRAPPIST-1 planets might host liquid water on their surface, making them top spots to look for signs of life (SN: 12/23/17, p. 25).

    Yet those planets shouldn’t exist. Astronomers calculated that the small star’s preplanet disk shouldn’t have contained enough rocky material to make even one Earth-sized orb, says astrophysicist Elisa Quintana of NASA’s Goddard Space Flight Center in Greenbelt, Md. Yet the disk whipped up seven.

    TRAPPIST-1 is just one of the latest in a long line of rule breakers.
    Other systems host odd characters not seen in our solar system: super-Earths, mini-Neptunes, hot Jupiters and more. Many exoplanets must have had chaotic beginnings to exist where we find them.

    These oddballs raise exciting questions about how solar systems form. Scientists want to know how much of a planet’s ultimate fate depends on its parent star, which ingredients are essential for planet building and which are just frosting on the planetary cake.

    NASA’s Transiting Exoplanet Survey Satellite, or TESS, which launched April 18, should bring in some answers.

    NASA/TESS

    TESS is expected to find thousands more exoplanets in the next two years. That crowd will help illuminate which planetary processes are the most common — and will help scientists zero in on the best planets to check for signs of life.


    CAKE POP PLANETS Yes, baking actually makes a nice analogy for planet formation. Take a look.

    Beyond the bare necessities

    All solar system recipes share some basic elements. The star and its planets form from the same cloud of gas and dust. The densest region of the cloud collapses to form the star, and the remaining material spreads itself into a rotating disk, parts of which will eventually coalesce into planets. That similarity between the star and its progeny tells Till and other scientists what to toss into the planetary stand mixer.

    “If you know the composition of the star, you can know the composition of the planets,” says astronomer Johanna Teske of the Carnegie Observatories in Pasadena, Calif. A star’s composition is revealed in the wavelengths of light the star emits and absorbs.

    When a planet is born can affect its final makeup, too. A gas giant like Jupiter first needs a rocky core about 10 times Earth’s mass before it can begin gobbling up gas. That much growth probably happens well before the disk’s gas disappears, around 10 million years after the star forms. Small, rocky planets like Earth probably form later.

    Finally, location matters. Close to the hot star, most elements are gas, which is no help for building planets from scratch. Where the disk cools toward its outer edge, more elements freeze to solid crystals or condense onto dust grains. The boundary where water freezes is called the snow line. Scientists thought that water-rich planets must either form beyond their star’s snow line, where water is abundant, or must have water delivered to them later (SN: 5/16/15, p. 8). Giant planets are also thought to form beyond the snow line, where there’s more material available.

    But the material in the disk might not stay where it began, Teske says. “There’s a lot of transport of material, both toward and away from the star,” she says. “Where that material ends up is going to impact whether it goes into planets and what types of planets form.” The amount of mixing and turbulence in the disk could contribute to which page of the cookbook astronomers turn to: Is this system making a rocky terrestrial planet, a relatively small but gaseous Neptune or a massive Jupiter?

    _________________________________________________________________
    Birthplace

    In the disk around a star, giant planets form beyond the “snow line,” where water freezes and more solids are available. Turbulence closer in knocks things around.
    3

    Source: T. Henning and D. Semenov/Chemical Reviews 2013
    _________________________________________________________________

    Some like it hot

    Like that roiling disk material, a full-grown planet can also travel far from where it formed.

    Consider “Hoptunes” (or hot Neptunes), a new class of planets first named in December in Proceedings of the National Academy of Sciences. Hoptunes are between two and six times Earth’s size (as measured by the planet’s radius) and sidled up close to their stars, orbiting in less than 10 days. That close in, there shouldn’t have been enough rocky material in the disk to form such big planets. The star’s heat should mean no solids, just gases.

    Hoptunes share certain characteristics — and unanswered questions — with hot Jupiters, the first type of exoplanet discovered, in the mid-1990s.

    “Because we’ve known about hot Jupiters for so long, some people kind of think they’re old hat,” says astronomer Rebekah Dawson of Penn State, who coauthored a review about hot Jupiters posted in January at arXiv.org. “But we still by no means have a consensus about how they got so close to their star.”

    Since the first known hot Jupiter, 51 Pegasi b, was confirmed in 1995, two explanations for that proximity have emerged. A Jupiter that formed past the star’s snow line could migrate in smoothly through the disk by trading orbital positions with the disk material itself in a sort of gravitational do-si-do. Or interactions with other planets or a nearby star could knock the planet onto an extremely elliptical or even backward orbit (SN Online: 11/1/13). Over time, the star’s gravity would steal energy from the orbit, shrinking it into a tight, close circle. Dawson thinks both processes probably happen.

    Hot Jupiters are more common around stars that contain a lot of elements heavier than hydrogen and helium, which astronomers call metals, astronomer Erik Petigura of Caltech and colleagues reported in February in The Astronomical Journal. High-metal stars probably form more planets because their disks have more solids to work with. Once a Jupiter-sized planet forms, a game of gravitational billiards could send it onto an eccentric orbit — and send smaller worlds out into space. That fits the data, too; hot Jupiters tend to lack companion worlds.

    Hoptunes follow the same pattern: They prefer metal-rich stars and have few sibling planets. But Hoptunes probably arrived at their hot orbits later in the star’s life. Getting close to a young star, a Hoptune would risk having its atmosphere stripped away. “They’re sort of in the danger zone,” Dawson says. Since Hoptunes do, in fact, have atmospheres, they were probably knocked onto an elliptical, and eventually close-in, orbit later.

    One striking exception to the hot loner rule is WASP-47b, [ApJL] a hot Jupiter with two nearby siblings between the sizes of Earth and Neptune. That planet is one reason Dawson thinks there’s more than one way to cook up a hot Jupiter.

    Rock or gas

    Hot Jupiters are so large that astronomers assume these exoplanets have thick atmospheres. But it’s harder to tell if a smaller planet is gassy like Neptune or rocky like Earth.

    To make a first guess at a planet’s composition, astronomers need to know the planet’s size and mass. Together, those numbers yield the planet’s density, which gives a sense of how much of the planet is solid like rock or diffuse like an atmosphere.

    3
    HOME SWEET HOMES New images from the Very Large Telescope in Chile reveal that dust disks around young stars can take on many different forms. The shape of a disk can affect – and be affected by – the presence of baby planets.

    ESO VLT Platform at Cerro Paranal elevation 2,635 m (8,645 ft)


    ESO/H. Avenhaus et al./E. Sissa et al./DARTT-S and SHINE collaborations

    The most popular planet detection strategies each measure one of those factors. The transit method, used by the Kepler space telescope, watches a star wink as the planet passes in front.

    NASA/Kepler Telescope

    Planet transit. NASA/Ames

    Comparing the star’s light before and during the transit reveals the planet’s size. The radial velocity method, used with telescopes on the ground, watches the star wobble in response to a planet’s gravity, which reveals the planet’s mass.

    Radial velocity Image via SuperWasp http http://www.superwasp.org-exoplanets.htm


    Radial Velocity Method-Las Cumbres Observatory

    [Left out of the discussion, Direct Imaging.

    Direct imaging-This false-color composite image traces the motion of the planet Fomalhaut b, a world captured by direct imaging.

    To me, this is a lapse in journalistic coverage as Direct Imaging is becomeing ao more powerful tool with new telescope capabilities.]

    Most of the stars observed by Kepler are too far away and too dim for direct, accurate measures of planet masses. But astronomers have inferred a size cutoff for rocky planets. Last June, researchers analyzing the full Kepler dataset noticed a surprising lack of planets between 1.5 and two times Earth’s size and suggested those 1.5 times Earth’s radius or smaller are probably rocky; two to 3.5 times Earth’s radius are probably gassy (SN Online: 6/19/17).

    Dozens more planets have had their masses inferred indirectly, mostly those in multiplanet systems where astronomers can observe how planets tug on one another. From what astronomers can tell, super-Earths — planets between one and about 10 times Earth’s mass — come in a wide range of compositions.

    The Kepler mission is about to end, as the spacecraft’s fuel is running out. TESS will pick up where Kepler leaves off. The new planet-hunting space telescope will revolutionize the study of super-Earth densities. It will scan 85 percent of the sky for bright, nearby stars to pick out the best planets for follow-up study. As part of its primary mission, TESS will find at least 50 planets smaller than Neptune that can have their masses measured precisely, too. “Having masses … will help us understand the compositions,” says Quintana, a TESS team member. “We can see: Is there a true transition line where planets go rocky to gaseous? Or is it totally random? Or does it depend on the star?”

    Star power

    All kinds of planets’ fates do, in fact, depend on the stars, Petigura’s recent work suggests. In a February report in The Astronomical Journal, he and colleagues measured the metal contents of 1,305 planet-hosting stars in Kepler’s field of view.

    The researchers learned that large planets and close-in planets — with orbital periods of 10 days or less — are more common around metal-rich stars. But the team was surprised to find that small planets and planets that orbit far from their stars show up around stars of all sorts of compositions. “They form efficiently everywhere,” Petigura says.

    That could mean that metal-rich stars had disks that extended closer to the stars. With enough material close to the star, hot super-Earths could have formed where they currently spin. The existence of hot super-Earths might even suggest that hot Jupiters can form close to the star after all. A super-Earth or mini-Neptune could represent the core of what was once a hot Jupiter that didn’t quite gather enough gas before the disk dissipated, or whose atmosphere was blown off by the star (SN Online: 10/31/17).

    Weird water

    Some scientists are looking to stars to reveal what’s inside a planet. The help is welcome because density is a crude measure for understanding what a planet is made of. Planets with the same mass and radius can have very different compositions and natures — look at hellish Venus and livable Earth.

    Take the case of TRAPPIST-1, which has seven Earth-sized worlds and is 39 light-years away. Astronomers are anxious to check at least three of the planets for signs of life
    (SN: 12/23/17, p. 25). But those planets might be so waterlogged that any signs of life would be hard to detect, says exogeologist Cayman Unterborn of Arizona State. So much water would change a planet’s chemistry in a way that makes it hard to tell life from nonlife. Based on the planets’ radii (measured by their transits) and their masses (measured by their gravitational influence on one another), Unterborn and colleagues used density to calculate a bizarre set of interiors for the worlds, which the team reported March 19 in Nature Astronomy.

    The TRAPPIST-1 planets have low densities for their size, Unterborn says, suggesting that their masses are mostly light material like water ice. TRAPPIST-1b, the innermost planet, seems to be 15 percent water by mass (Earth is less than 0.1 percent water). The fifth planet out, TRAPPIST-1f, may be at least half water by mass. If the planet formed with all that water already in it, it would have had 1,000 Earth oceans’ worth of water. That amount of water would compress into exotic phases of ice not found at normal pressures on Earth. “That is so much water that the chemistry of how that planet crystallized is not something we have ever imagined,” Unterborn says.

    _______________________________________________________
    Size it up

    Measuring a planet’s mass and radius gives astronomers a sense of planetary makeup. This plot compares the TRAPPIST-1 planets (purple) with Earth, Venus, an exoplanet named K2-229b and a couple of other worlds.

    5

    Source: A. Santerne et al/Nature Astronomy 2018

    _______________________________________________________

    But there’s a glitch. Unterborn’s analysis was based on the most accurate published masses for the TRAPPIST-1 worlds at the time. But on February 5, the same day his paper was accepted in Nature Astronomy, a group led by astronomer Simon Grimm of the University of Bern in Switzerland posted more precise mass measurements at Astronomy and Astrophysics. Those masses make the soggiest planets look merely damp.

    Clearly, Unterborn says, density is not destiny. Studying a planet based on its mass and radius has its limits.

    Looking deeper

    As a next step, Unterborn and colleagues have published a series of papers suggesting how stellar compositions can tell the likelihood that a group of planets have plate tectonics, or how much oxygen the planet atmospheres may have. Better geologic models may ultimately help reveal if a single planet is habitable.

    But Unterborn is wary of translating composition from a star to any individual planet — existing geochemical models aren’t good enough. The recent case of K2-229b makes that clear. Astronomer Alexandre Santerne of the Laboratory of Astrophysics of Marseille in France and colleagues recently tried to see if a star’s composition could describe the interior of its newly discovered exoplanet, K2-229b. The team reported online March 26 in Nature Astronomy that the planet has a size similar to Earth’s but a makeup more like Mercury’s: 70 percent metallic core, 30 percent silicate mantle by mass. (The researchers nicknamed the planet Freddy, for Queen front man Freddie Mercury, Santerne wrote on Twitter.) That composition is not what they’d expect from the star alone.

    __________________________________________________
    Hints from the star

    Based on its mass and radius, an exoplanet named K2-229b is about Earth’s size but more similar to Mercury in composition, astronomers suggest.

    6

    Source: A. Santerne et al/Nature Astronomy 2018

    __________________________________________________

    Geologic models need to catch up quickly. After TESS finds the best worlds for follow-up observations, the James Webb Space Telescope, due to launch in 2020, will search some of those planets’ atmospheres for signs of life (SN: 4/30/16, p. 32). For that strategy to work, Unterborn says, scientists need a better read on the exoplanet cookbook.

    Christy Till’s pressure-packed test kitchen may help. Till is primarily a volcanologist who studies how magma erupting onto Earth’s surface can reveal conditions in Earth’s interior. “The goal is to start doing that for exoplanets,” she says.

    Till and colleagues are redoing some foundational experiments conducted for Earth 50 years ago but not yet done for exoplanets. The experiments predict which elements can go into planets’ mantles and cores, and which will form solid crusts. (Early results that Till presented in December in New Orleans at the American Geophysical Union meeting suggest that multiplying the sun’s magnesium-to-silicon ratio by 1.33 still bakes a rocky planet, but with a different flavored crust than Earth’s.)

    Till uses three piston cylinders to squash and singe synthetic exoplanets for 24 hours to see what minerals form and melt at different pressures and temperatures. The results may help answer questions like what kind of lava would erupt on a planet’s surface, what would the crust be made of and what gases might end up in the planet’s atmosphere.

    It’s early days, but Till’s recipe testing may mean scientists won’t have to wait decades for telescopes to get a close enough look at an exoplanet to judge how much like home it really is. With new cookbook chapters, Unterborn says, “we can figure out which stars are the best places to build an Earth.”

    Related journal articles
    _________________________________________________
    See the full article for further references with links.

    See the full article here .

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    ASU is the largest public university by enrollment in the United States.[11] Founded in 1885 as the Territorial Normal School at Tempe, the school underwent a series of changes in name and curriculum. In 1945 it was placed under control of the Arizona Board of Regents and was renamed Arizona State College.[12][13][14] A 1958 statewide ballot measure gave the university its present name.
    ASU is classified as a research university with very high research activity (RU/VH) by the Carnegie Classification of Institutions of Higher Education, one of 78 U.S. public universities with that designation. Since 2005 ASU has been ranked among the Top 50 research universities, public and private, in the U.S. based on research output, innovation, development, research expenditures, number of awarded patents and awarded research grant proposals. The Center for Measuring University Performance currently ranks ASU 31st among top U.S. public research universities.[15]

    ASU awards bachelor’s, master’s and doctoral degrees in 16 colleges and schools on five locations: the original Tempe campus, the West campus in northwest Phoenix, the Polytechnic campus in eastern Mesa, the Downtown Phoenix campus and the Colleges at Lake Havasu City. ASU’s “Online campus” offers 41 undergraduate degrees, 37 graduate degrees and 14 graduate or undergraduate certificates, earning ASU a Top 10 rating for Best Online Programs.[16] ASU also offers international academic program partnerships in Mexico, Europe and China. ASU is accredited as a single institution by The Higher Learning Commission.

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  • richardmitnick 10:43 am on May 4, 2018 Permalink | Reply
    Tags: , , , , , , Transit spectroscopy   

    From MIT News: “Ushering in the next phase of exoplanet discovery” 

    MIT News
    MIT Widget

    MIT News

    May 3, 2018
    Lauren Hinkel | Oceans at MIT

    NASA/TESS

    1
    “TESS is trying to take everything that people have already done and do it better and do it across the whole sky,” says Sara Seager, the Class of 1941 Professor at MIT.
    Photo: Justin Knight.

    2
    TESS will survey the sky in a series of 13 observing segments, each 27-days long. It will spend the first year on the southern ecliptic hemisphere and the second year on the northern ecliptic hemisphere. Depending on sky position, TESS targets will be observed for a minimum of 27 days up to a maximum of 351 days. Image: Roland Vanderspek.

    Professor Sara Seager previews a new era of discovery as a leader of the TESS mission, which is expected to find some 20,000 extrasolar planets.


    A SpaceX Falcon 9 rocket lifted off on April 18 from Cape Canaveral Air Force Station carrying NASA’s Transiting Exoplanet Survey Satellite, or TESS. The MIT-led mission is the next step in the search for planets outside of the solar system and orbiting other nearby stars. The mission is designed to find exoplanets by blocking their light while the planets transition across. Video: NASA

    Ever since scientists discovered the first planet outside of our solar system, 51 Pegasi b, the astronomical field of exoplanets has exploded, thanks in large part to the Kepler Space Telescope.

    NASA/Kepler Telescope

    Now, with the successful launch of the Transiting Exoplanet Survey Satellite (TESS), Professor Sara Seager sees a revolution not only in the amount of new planetary data to analyze, but also in the potential for new avenues of scientific discovery.

    “TESS is going to essentially provide the catalog of all of the best planets for following up, for observing their atmospheres and learning more about them,” Seager says. “But it would be impossible to really describe all the different things that people are hoping to do with the data.”

    For Seager, the goal is to sift through the plethora of incoming TESS data to identify exoplanet candidates. Ultimately, she says she wants to find the best planets to follow up with atmosphere studies for signs that the planet might be suitable for life.

    “When I came to MIT 10 years ago, [MIT scientists] were starting to work on TESS, so that was the starting point,” said Seager, the Class of 1941 Professor Chair in MIT’s Department of Earth, Atmospheric and Planetary Sciences with appointments in the departments of Physics and Aeronautics and Astronautics.

    Seager is the deputy science director of TESS, an MIT-led NASA Explorer-class mission. Her credentials include pioneering exoplanet characterization, particularly of atmospheres, that form the foundation of the field. Seager is currently hunting for exoplanets with signs of life, and TESS is the next step on that path.

    So far, scientists have confirmed 3,717 exoplanets in 2,773 systems. As an all-sky survey, TESS will build on this, observing 85 percent of the cosmos containing more than 200,000 nearby stars, and researchers expect to identify some 20,000 exoplanets.

    “TESS is trying to take everything that people have already done and do it better and do it across the whole sky,” Seager says. While this mission relies on exoplanet hunting techniques developed years ago, the returns on this work should extend far into the future.

    Planet transit. NASA/Ames

    Radial Velocity Method-Las Cumbres Observatory

    Radial velocity Image via SuperWasp http http://www.superwasp.org-exoplanets.htm

    Direct imaging-This false-color composite image traces the motion of the planet Fomalhaut b, a world captured by direct imaging.

    “TESS is almost the culmination of a couple of decades of hard work, trying to iron out the wrinkles of how to find planets by the transiting method. So, TESS isn’t changing the way we look for planets, more like it’s riding on the wave of success of how we’ve done it already.”

    The TESS science leadership team have committed to delivering at least 50 exoplanets with radii less than four times that of Earth’s along with measured masses. As part of the TESS mission, an international effort to further characterize the planet candidates and their host stars down to the list of 50 with measured masses will be ongoing, using the best ground-based telescopes available.

    For the best exoplanets for follow up, Seager likens photons reaching the satellite’s cameras to money: the more photons you have, the better. Accordingly, the cameras are optimized for nearby, bright stars. Furthermore, the cameras are calibrated to favor small, red M dwarf stars, around which small planets with a rocky surface are more easily detected than around the larger, yellow sun-size stars. Additionally, researchers tuned the satellite to exoplanets with orbits of less than 13 days, so that two transits are used for discovery.

    See the full article here .

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  • richardmitnick 9:23 pm on May 2, 2018 Permalink | Reply
    Tags: , , , , , Exoplanet Fomalhaut b On the Move, , , Transit spectroscopy   

    From Many Worlds: “Exoplanet Fomalhaut b On the Move” 

    NASA NExSS bloc

    NASA NExSS

    Many Words icon

    Many Worlds

    2018-04-30
    Marc Kaufman

    1
    Enlarge on the full blog post or the full article and enjoy. Fomalhaut b on its very long (1,700 year) and elliptica orbit, as seen here in five images taken by the Hubble Space Telescope over seven years. The reference to “20 au” means that the bar shows a distance of 20 astronomical units, or 20 times the distance from the sun to the Earth. (Jason Wang/Paul Kalas; UC Berkeley)

    Direct imaging of exoplanets remains in its infancy, but goodness what a treat it is already and what a promise of things to come.

    Almost all of the 3,714 exoplanets confirmed so far were detected via the powerful but indirect transit and radial velocity methods — measures of slightly decreased light as a planet crosses in front of its star, or the measured wobble of a star caused by the gravitational pull of a planet.

    But now 44 planets have also been detected by telescopes — in space and on the ground — looking directly at distant stars. Using increasingly sophisticated coronagraphs to block out the blinding light of the stars, these tiny and often difficult-to-identify specks are nonetheless results that are precious to scientists and the public.

    To me, they make exoplanet science accessible as perhaps nothing else so far. Additionally, they strike me as moving — and I don’t mean in orbit. Rather, as when you see your own insides via x-rays or MRIs, direct imaging of exoplanets provides a glimpse into the otherwise hidden realities of our world.

    And in the years ahead – actually, most likely the decades ahead — this kind of direct imaging of our astronomical neighborhood will become increasingly powerful and common.

    This is how the astronomers studying the Fomalhaut system describe what you are seeing:

    “The Fomalhaut system harbors a large ring of rocky debris that is analogous to our Kuiper belt. Inside this ring, the planet Fomalhaut b is on a trajectory that will send it far beyond the ring in a highly elliptical orbit.

    “The nature of the planet remains mysterious, with the leading theory being the planet is surrounded by its own ring or a sphere of dust.”

    2
    An animated simulation of one possible orbit for Fomalhaut b derived from the analysis of Hubble Space Telescope data between 2004 and 2012, presented in January 2013 by astronomers Paul Kalas and James Graham of Berkeley, Michael Fitzgerald of UCLA and Mark Clampin of NASA/Goddard. (Paul Kalas)

    Fomalhaut b was first described in 2008 by Paul Kalas, James Graham and colleagues at the University of California, Berkeley. If not the first object identified through direct imaging — a brown dwarf failed star preceded it, as well as other objects that remain planet candidates — Fomalhaut was among the very first.

    Direct imaging-This false-color composite image traces the motion of the planet Fomalhaut b, a world captured by direct imaging. Credit: NASA, ESA, and P. Kalas (University of California, Berkeley and SETI Institute)

    The data came via the Advanced Camera for Surveys [ACS] on the Hubble Space Telescope.

    NASA/ESA Hubble ACS

    NASA/ESA Hubble Telescope

    But Fomalhaut b is an unusual planet by any standard, and that resulted in a lot of early debate about whether it really was a planet. Early efforts to confirm the presence of the planet failed, in part because the efforts were made in the infrared portion of the spectrum.

    Instead, Fomalhaut b had been detected only in the optical portion of the spectrum, which is uncommon for a directly imaged planet. More specifically, it reflects bluish light, which again is unusual for a planet. Some contended that the planet detection made by Hubble was actually a noise artifact.

    A pretty serious debate ensued in 2011 but by 2013 the original Hubble data had been confirmed by two teams and its identity as a planet was broadly embraced, although the noise of the earlier debate to some extent remains.

    As Kalas told me, this is probably because “no one likes to cover the end of a debate.” Nonetheless, he said, it is over.

    “Fomalhaut b at age 440 Myr (.44 billion years) is much older than the other directly imaged planets,” Kalas explained. “The younger the planet, the greater the infrared light it emits. Thus it is not particularly unusual that it is hard to image planets in the Fomalhaut system using infrared techniques.”

    Kalas believes that a ring system around the planet could be reflecting the light. Another possibility, he said, is that two dwarf planets collided and a compact dust cloud surrounding a dwarf planet is moving through the Fomalhaut system.

    That scenario would be very difficult to test, he said, but the alternate possibility of a Saturnian exoplanet with a ring is something that the James Webb Space Telescope will be able to explore.

    In any case, the issue of whether or not the possibly first directly-imaged planet is in fact a planet has been resolved for now.

    When the International Astronomical Union held a global contest to name some of the better known exoplanets several years ago, one selected for naming was Fomalhaut b, which also now has the name “Dagon.” The star Fomalhaut is the brightest in the constellation Pisces Australis — the Southern Fish — and Dagon was a fish god of the ancient Philistines.

    3
    This animated video of Beta Pictoris and its exoplanet was made using nine images taken with the Gemini Planet Imager over more than two years years. The planet is expected to come our from behind its star later this year, and the GPI team hopes to capture that event. (Jason Wang; UC Berkeley, Gemini Planet Imager Exoplanet Survey)

    NOAO Gemini Planet Imager on Gemini South


    Gemini South telescope, Cerro Tololo Inter-American Observatory (CTIO) campus near La Serena, Chile, at an altitude of 7200 feet

    While instruments on the W.M. Keck Observatory in Hawaii, the European Very Large Telescope in Chile and the Hubble Space Telescope have succeeded in directly imaging some planets, the attention has been most focused on the two relatively newcomers. They are the Gemini Planet Imager (GPI), now on the Gemini South Telescope in Chile [above] and funded largely by American organizations and universities, and the largely European Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument, also in Chile.


    Keck Observatory, Maunakea, Hawaii, USA.4,207 m (13,802 ft), above sea level, showing also NASA’s IRTF and NAOJ Subaru

    ESO VLT Platform at Cerro Paranal elevation 2,635 m (8,645 ft)

    ESO SPHERE extreme adaptive optics system and coronagraphic facility on the extreme adaptive optics system and coronagraphic facility on the VLT, Cerro Paranal, Chile, with an elevation of 2,635 metres (8,645 ft) above sea level


    ESO/SPHERE extreme adaptive optics system and coronagraphic facility on the VLT, Cerro Paranal, Chile, with an elevation of 2,635 metres (8,645 ft) above sea level


    ESO SPHERE extreme adaptive optics system and coronagraphic facility on the extreme adaptive optics system and coronagraphic facility on the VLT, Cerro Paranal, Chile, with an elevation of 2,635 metres (8,645 ft) above sea level

    In real time, the two instruments correct for distorting atmospheric turbulences around Earth and also block the intense light of the host stars. Any residual incoming light is then scrutinized, and the brightest spots suggest a possible planet and can be photographed as such.

    The ultimate goal is have similar instruments improved until they are powerful enough to read the atmospheres of the planets through spectroscopy, which has been done so far only to a limited extent.

    Kalas, Graham and Jason Wang (a graduate student at Berkeley who put together the direct imaging movies ) are part of the GPI team, which since 2014 has been searching for Jupiter-sized and above planets orbiting some distance from their suns. The group is a member of NASA’s NExSS initiative to encourage exoplanet scientists from many disciplines to work together.

    While GPI has had successes detecting important exoplanets such as 51 Eridani b, it also studies already identified planets to increase understanding of their orbits and their characteristics.

    5
    The Gemini Planet Imager when it was being connected to the Gemini South Telescope in Chile. (Gemini Observatory)

    GPI has been especially active in studying the planet Beta Pictoris b, a super Jupiter discovered using data collected by the European Southern Observatory Very Large Telescope. While the data was first collected in 2003, it took five years to tease out the planet orbiting the young star and it took several more years to confirm the discovery and begin characterizing the planet.

    GPI has followed Beta Pictoris b for several years now, compiling orbital and other data used for video above.

    The planet is currently behind its sun and so cannot be observed. But James Graham told me that the planet is expected to emerge late this year or early next year. It remains unclear, Graham said, whether GPI will be able to capture that emergence because it will soon be moved from the Gemini telescope in Chile to the Gemini North Telescope on Hawaii. But he certainly hopes that it will be allowed to operate until the planet reappears.

    The planet 51 Eridani b was the first exoplanet discovered by the GPI and remains one of its most important. The planet is a million times fainter than its parent star and shows the strongest methane signature ever detected on an alien planet, which should yield additional clues as to how the planet formed.

    The four-year GPI campaign from Chile has not discovered as many Jupiter-and-greater sized planets as earlier expected. Graham said that may well be because there are fewer of them than astronomers predicted, or it may be because direct imaging is difficult to do.

    But Graham said the campaign is actually nowhere near over. Much of the data collected since 2014 remains to be studied and teased apart, and other Jupiters and super Jupiters likely are hidden in the data.

    Right now the exoplanet science community, and especially those active in direct imaging, are anxiously awaiting a decision by NASA, and then Congress, about the fate of the Wide Field Infrared Survey Telescope (WFIRST.)

    Designed to be the first space telescope to carry a coronagraph and consequently a major step forward for direct imaging, it was scheduled to be NASA’s big new observatory of the 2020s.

    But the Trump Administration cancelled the mission earlier this year, Congress then restored it but with the caveat that NASA had to provide a detailed plan for its science, its technology and its cost. That plan remains an eagerly-awaited work in progress.

    Meanwhile, here is another example of what direct imaging, with the help of soon-to-be Caltech postdoc Jason Wang, can provide. The video of the HR 8799 system went viral when first made public in early last year.

    6
    The four planet system orbiting the planet HR 8977, first partially identified in 2008 by Christian Marois of the National Research Council of Canada’s Herzberg Institute of Astrophysics and Bruce Macintosh of Stanford and others. The video was created in 2017 after all four planets had been identified via direct imagine and their orbits had been followed for some years. (Jason Wang of UC Berkeley/Christian Marois of NRC Herzberg.)

    The promise of direct imaging is enormous. The collected photons can be used for spectroscopy that can potentially tell scientists about a planet’s radius, mass, age, effective temperature, clouds, molecular composition, rotation rate and atmospheric dynamics.

    For a small, potentially habitable planet, direct imaging can measure surface temperate and pressure and determine whether it can support liquid water. It can also potentially determine if the atmosphere is in the kind of disequilibrium regarding oxygen, ozone and perhaps methane that signal the presence of life.

    But almost all this is in the future since none of the current instruments are powerful enough to collect that data.

    7
    University of California at Berkeley astronomy grad student Lea Hirsch at [the very important to me] Lick Observatory [at UCSC, on Mt Hamilton This was the location running the UCO system under the great Sandra Faber, who was a major contributor to the salvation of Hubble with COSTAR]. She will be going soon to Stanford University for a postdoc with Gemini Planet Imager Principal Investigator Bruce Macintosh.

    In the meantime, researchers such as Berkeley graduate student Lea Hirsch, soon to be a Stanford postdoc, are focused on using the strengths of the different detection methods to come up with constraints on exoplanetary characteristics (such as mass and radius) that one technique alone could not provide.

    For instance, the transit technique works best for identifying planets close to their stars, direct imaging is the opposite and radial velocity is best that detecting large and relatively close-in planets. Radial velocity gives a minimum (but not maximum) mass, while transits provide an exoplanet radius.

    Planet transit. NASA/Ames

    Radial velocity Image via SuperWasp http://www.superwasp.org/exoplanets.htm

    Radial Velocity Method-Las Cumbres Observatory

    What Hirsch would like to do is determine constraints (limits) on the size of exoplanets using both radial velocity measurements and direct imaging.

    As she explained, radial velocity will give that minimum mass, but nothing more in terms of size. But in an indirect way for now, direct imaging can provide some maximum mass.

    If, for instance, astronomers know through the radial velocity method that exoplanet X orbits a certain star and is twice the size of Jupiter, they can then look for it using direct imaging with confidence that something is there. Let’s say the precision of the imaging is such that if a planet six times the size of Jupiter was present they would — over a period of time — detect it.

    A detection would indeed be great and the planet’s mass (and more) would then be known. But if no planet is detected — as often happens — then astronomers still collect important information. They know that the planet they are looking for is less than six Jupiter masses. Since the radial velocity method already determined it was at least larger than two Jupiters, scientists would then know that the planet has a mass of between two and six Jupiters.

    “All the techniques in our toolkit {of exoplanet searching} have their strengths and weaknesses,” she said. “But using those techniques together is part of our future because there’s a potential to know much more.”

    See the full article here .

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    About Many Worlds

    There are many worlds out there waiting to fire your imagination.

    Marc Kaufman is an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer, and is the author of two books on searching for life and planetary habitability. While the “Many Worlds” column is supported by the Lunar Planetary Institute/USRA and informed by NASA’s NExSS initiative, any opinions expressed are the author’s alone.

    This site is for everyone interested in the burgeoning field of exoplanet detection and research, from the general public to scientists in the field. It will present columns, news stories and in-depth features, as well as the work of guest writers.

    About NExSS

    The Nexus for Exoplanet System Science (NExSS) is a NASA research coordination network dedicated to the study of planetary habitability. The goals of NExSS are to investigate the diversity of exoplanets and to learn how their history, geology, and climate interact to create the conditions for life. NExSS investigators also strive to put planets into an architectural context — as solar systems built over the eons through dynamical processes and sculpted by stars. Based on our understanding of our own solar system and habitable planet Earth, researchers in the network aim to identify where habitable niches are most likely to occur, which planets are most likely to be habitable. Leveraging current NASA investments in research and missions, NExSS will accelerate the discovery and characterization of other potentially life-bearing worlds in the galaxy, using a systems science approach.
    The National Aeronautics and Space Administration (NASA) is the agency of the United States government that is responsible for the nation’s civilian space program and for aeronautics and aerospace research.

    President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

    Since that time, most U.S. space exploration efforts have been led by NASA, including the Apollo moon-landing missions, the Skylab space station, and later the Space Shuttle. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program (LSP) which provides oversight of launch operations and countdown management for unmanned NASA launches. Most recently, NASA announced a new Space Launch System that it said would take the agency’s astronauts farther into space than ever before and lay the cornerstone for future human space exploration efforts by the U.S.

    NASA science is focused on better understanding Earth through the Earth Observing System, advancing heliophysics through the efforts of the Science Mission Directorate’s Heliophysics Research Program, exploring bodies throughout the Solar System with advanced robotic missions such as New Horizons, and researching astrophysics topics, such as the Big Bang, through the Great Observatories [Hubble, Chandra, Spitzer, and associated programs. NASA shares data with various national and international organizations such as from the [JAXA]Greenhouse Gases Observing Satellite.

     
  • richardmitnick 4:07 pm on November 2, 2017 Permalink | Reply
    Tags: , , , , Cold Trap in a Hot Jupiter’s Atmosphere, , Kepler-13Ab, Transit spectroscopy   

    From Centauri Dreams: “Cold Trap in a Hot Jupiter’s Atmosphere” 

    Centauri Dreams

    November 2, 2017
    Paul Gilster

    The other day I looked at how we can use transit spectroscopy to study the atmospheres of exoplanets. Consider this a matter of eclipses, the first occurring when the planet moves in front of its star as seen from Earth.

    Planet transit. NASA/Ames

    We can measure the size of the planet and also see light from the star as it moves through the planetary atmosphere, giving us information about its composition. The secondary eclipse, when the planet disappears behind the star, is also quite useful. Here, we can study the atmosphere in terms of its thermal variations.

    In my recent post, I used a diagram from Sara Seager to show primary and secondary eclipse in relation to a host star. The image below, by Josh Winn, is useful because it drills down into the specifics.

    1
    Image: A comparison between transits and secondary eclipses (also sometimes called occultations). In a planetary transit, the planet crosses in front of the star (see lower dip) blocking a fraction of the star’s brightness. In a secondary eclipse, the planet crosses behind the star, blocking the planet’s brightness (see dip in the middle). The latter dip in brightness is fainter due to the faintness of the planet. Credit: Josh Winn. See A New Discovery of a Secondary Eclipse for more background as it applies to the HAT-P-11 system.

    Secondary eclipses have been significant in the study of Kepler-13Ab, a world where conditions could not be more different on the planet’s nightside vs. its dayside. A ‘hot Jupiter’ some 1730 light years from Earth, this is a world close enough to its parent star that it is tidally locked. Researchers led by Thomas Beatty (Pennsylvania State) have used the Hubble Space Telescope to determine that that the dayside here can surpass a blistering 3000 Kelvin.

    By contrast, the nightside of Kepler-13Ab, turned forever away from the star, is a place where titanium oxide snow can fall. The process is intriguing: Any titanium oxide gas on the star-facing side is carried by strong winds around to the nightside, where the gas condenses into clouds and eventually falls as snow. A gravitational tug six times greater than Jupiter’s pulls the titanium oxide into the lower atmosphere, forming a ‘cold trap’ — an atmospheric layer that is colder than the layers both below and above it. Ascending gases drop back into the trap.

    Science paper:
    Evidence for Atmospheric Cold-trap Processes in the Noninverted Emission Spectrum of Kepler-13Ab Using HST/WFC3

    Centauri Dreams

    See the full article here .

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    Tracking Research into Deep Space Exploration

    Alpha Centauri and other nearby stars seem impossible destinations not just for manned missions but even for robotic probes like Cassini or Galileo. Nonetheless, serious work on propulsion, communications, long-life electronics and spacecraft autonomy continues at NASA, ESA and many other venues, some in academia, some in private industry. The goal of reaching the stars is a distant one and the work remains low-key, but fascinating ideas continue to emerge. This site will track current research. I’ll also throw in the occasional musing about the literary and cultural implications of interstellar flight. Ultimately, the challenge may be as much philosophical as technological: to reassert the value of the long haul in a time of jittery short-term thinking.

     
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