Tag: TESS (page 1 of 2)

A Close Exoplanet Found That May Have An Atmosphere Ideal For Study

Planet Gliese 486b is close to us (in a relative sense), rocky, on the small side and may have an atmosphere.  These conclusions come from studying the planet using both the transit and radial velocity techniques, which have been the primary methods used by astronomers to find and characterize exoplanets.  Charts showing the presence of the planet using both techniques are in the blue boxes. (Render Area, Max Planck Institute for Astronomy, MPIA)

Different methods of searching for and finding distant exoplanets give different information about the planets found.

The transit method — where an exoplanets passed in front of its sun and dims the bright sunlight ever so slightly — gives astronomers not only a detection but also its radius or size.

The radial velocity method — where an exoplanet’s gravity causes its host star to “wobble” in a way that can be measured — provides different information about mass and orbit.

If a planet can be measured by both the transit and radial velocity methods, an important added dimension can be determined — how dense the planet might be.  This tells us if the planet is rocky or gaseous, watery or even if it has a central core and might have an atmosphere.  So many things have to go right that this kind of dual detection has seldom been accomplished for a  relatively small and rocky planet, but such a new planet has now been found.

The planet, Gliese 486b, is a super-Earth orbiting its host star at only 24 light-years away.  That makes the planet the third closest transiting exoplanet to Earth that is known, and the closest with a measured mass that transits a red dwarf star.

The authors of the study in the journal Science say Gliese 486b is an ideal candidate for learning how to best search for and characterize an all-important atmosphere, and to study potential habitability, too.  Future telescopes will make this kind of work more of a reality.

“Gliese 486 b is not hot enough to be a lava world,” lead author Trifon Trifonov of the Max-Planck-Institut für Astronomie and colleagues write. “But its temperature of ~700 Kelvin (800 degrees Fahrenheit) makes it suitable for emission spectroscopy and …. studies in search of an atmosphere.”

Artist impression of the surface of the newly discovered hot super-Earth Gliese 486 b. With a temperature of about 700 Kelvin (almost 800 degrees Fahrenheit), 486b possibly has an atmosphere.

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More Weird and Wild Planets

A world called TOI-849b could be the exposed, naked core of a former gas giant planet whose atmosphere was blasted away by its star.  Every day is a bad day on planet TOI-849b. . It hugs its star so tightly that a year – one trip around the star – takes less than a day. And it pays a high price for this close embrace: an estimated surface temperature of nearly 2,800 degrees Fahrenheit (1,500 degrees Celsius) It’s a scorcher even compared to Venus, which is 880 degrees Fahrenheit (471 degrees Celsius). About half the mass of our own Saturn, this planet orbits a Sun-like star more than 700 light-years from Earth. (NASA/Exoplanet Exploration Program)

The more we learn about the billions upon billions of planets that orbit beyond our solar system, the more we are surprised by the wild menagerie of objects out there.  From the start, many of these untolled planets have been startling, paradigm-breaking,  mysterious, hellish, potentially habitable and just plain weird.  Despite the confirmed detection of more than 4,000 exoplanets, the job of finding and characterizing these worlds remains in its early phases.  You could make the argument that  learning a lot more about these distant exoplanets and their solar systems is not just one of the great tasks of future astronomy, but of future science.

And that is why Many Worlds is returning to the subject of “Weird Planets,” which first appeared in this column at the opening of 2019.  It has been the most viewed column in our archive, and a day seldom goes by without someone — or some many people — decide to read it.

So here is not a really a sequel, but rather a continuation of writing about this unendingly rich subject.  And as I will describe further on,  almost all of the planets on display so far have been detected and characterized without ever having been seen.  The characteristics and colors presented in these (mostly) artistic renderings are the result of indirect observing and discovery — measuring how much light dims when a faraway planet crosses its host star, or how much the planet’s gravity causes its sun to move.

As a result, these planets are sometimes called “small, black shadows.” Scientists can infer a lot from the indirect measurements they make and from the beginnings of the grand effort to spectroscopically read the chemical makeup of exoplanet atmospheres. … Read more

The Planet Larger Than Its Star

Artist animation of WD 1856 b orbiting the white dwarf. Due to the tiny size of the white dwarf and close orbit of the planet, the animation is to scale. The slightly inclined orbit means that the planet does not entirely block the white dwarf’s light as it transits (Tasker).

It has been an exciting month for planets. Just days after the announcement of a detection of phosphine in the clouds of Venus, another first in planet discoveries was declared. The new find is the first planet observed to be orbiting a white dwarf; a dead star that is much smaller than the planet it hosts.

Planet WD 1856+534 b was first spotted by the NASA’s Transiting Exoplanet Survey Satellite (TESS) and confirmed with a series of observations from ground-based telescopes. The results showed the light from a white dwarf being periodically dimmed by a staggering 56% for brief 8 minutes.

For comparison, one of the easiest exoplanet types to detect is a hot Jupiter that would typically cause a 1% dip in brightness of its star over a period of a few hours.

This suggested a Jupiter-sized planet was closely orbiting a white dwarf that was similar in size to the Earth. Light from the white dwarf is obscured each time the planet passes in front of (or transits) the dead star’s surface on its orbit. Interestingly, the light dip is shaped like the letter V, showing a gentle gradient decreasing and rising from the maximum occultation. The lack of a sharp drop in brightness implied the planet’s orbit was slightly inclined so that it grazed the white dwarf’s surface and only obscured part of the much smaller star.

Light dip (transit) observations of WD 1856 observed with the Gran Telescopio Canarias (GTC) in visible light. The red curve is the best-fitting models. The V-shape suggests the planet is grazing the white dwarf and does not obscure it completely (Vanderburg et al. 2020, Figure 1a).

Although certainly unusual, WD 1856 b is not the first planet known to orbit a smaller star. The first extrasolar planets to be discovered orbit another type of stellar remnant known as a neutron star. While white dwarfs typically have sizes similar to a terrestrial planet, neutron stars have city-sized diameters of order 10 km.

The fact both these cases involve dead stars is no coincidence. In order to orbit, the mass of the planet must be much less than that of the star.… Read more

Tatooine Worlds

Science fiction has become science.  No habitable planets orbiting two suns like the fictional Tatooine have been detected so far, but more than a dozen “circumbinary planets” have been identified and many more are predicted.  Exoplanets orbiting a host star that orbits its own companion star are even more common. (Lucasfilm)

When the the first Star Wars movie came out in 1977, it featured the now-iconic two-sun, “circumbinary” planet Tatooine.  At that time astronomers didn’t really know if such solar systems existed, with more than one sun and at least one planet.

Indeed, the first extra-solar planet wasn’t detected until the early 1990s.  And the first actual circumbinary planet was detected in 2005, and it was a Jupiter-size planet orbiting a system composed of a sun-like star and a brown dwarf.  Tatooine was definitely not a Jupiter-size planet.

But since then, the presence and distribution of circumbinaries has grown to a dozen and some the planets discovered orbiting the two stars have been smaller.  The most recent discovery was announced this week and was made using the Transiting Exoplanet Survey Satellite (TESS) space telescope

The new planet, called TOI (TESS Object of Interest)-1338 b, is about 6.9 times larger than Earth. It orbits its pair of host stars every 95 days, while the stars themselves orbit each other in 15 days.

As is common with binary stars, one is more massive and much brighter than the other (5976 K and 3657 K, respectively, with our sun at  5780 K),  and as the planet orbits around it blocks some of the light from the brighter star.

This transit allows astronomers to measure the size of the planet.  The transit — as scientific luck, or skill, would have it — was first found in the TESS data by a high school student working at NASA with over the summer,  Wolf Cukier

“I was looking through the data for everything the volunteers had flagged as an eclipsing binary, a system where two stars circle around each other and from our view eclipse each other every orbit,” Cukier said. “About three days into my internship, I saw a signal from a system called TOI 1338.”

“At first I thought it was a stellar eclipse, but the timing was wrong. It turned out to be a planet.”

With all of the data available from observations past and current, planet hunting clearly isn’t the scientific Wild West that it used to be — although the results remain often eye-popping and surprising.… Read more

A Southern Sky Extravaganza From TESS

Candidate exoplanets as seen by TESS in a southern sky mosaic from 13 observing sectors. (NASA/MIT/TESS)

NASA’s Transiting Exoplanet Survey Satellite (TESS) has finished its one year full-sky observation of  Southern sky and has found hundreds of candidate exoplanets and 29 confirmed planets.  It is now maneuvering  its array of wide-field telescopes and cameras to focus on the northern sky to do the same kind of exploration.

At this turning point, NASA and the Massachusetts Institute of Technology — which played a major role in designing and now operating the mission — have put together mosaic images from the first year’s observations, and they are quite something.

Constructed from 208 TESS images taken during the mission’s first year of science operations, these images are a unique  space-based look at the entire Southern sky — including the Milky Way seen edgewise, the Large and Small Magellenic galaxies, and other large stars already known to have exoplanet.

“Analysis of TESS data focuses on individual stars and planets one at a time, but I wanted to step back and highlight everything at once, really emphasizing the spectacular view TESS gives us of the entire sky,” said Ethan Kruse, a NASA Postdoctoral Program Fellow who assembled the mosaic at NASA’s Goddard Space Flight Center.

Overlaying the figures of selected constellations helps clarify the scale of the TESS southern mosaic. TESS has discovered 29 exoplanets, or worlds beyond our solar system, and more than 1,000 candidate planets astronomers are now investigating. NASA/MIT/TESS

The mission is designed to vastly increase the number of known exoplanets, which are now theorized to orbit all — or most — stars in the sky.

TESS searches for  the nearest and brightest main sequence stars hosting transiting exoplanets, which are the most favorable targets for detailed investigations.

This animation shows how a dip in the observed brightness of a star may indicate the presence of a planet passing in front of it, an occurrence known as a transit. This is how TESS identified planet.
(NASA’s Goddard Space Flight Center)

While previous sky surveys with ground-based telescopes have mainly detected giant exoplanets, TESS will find many small planets around the nearest stars in the sky.  The mission will also provide prime targets for further characterization by the James Webb Space Telescope, as well as other large ground-based and space-based telescopes of the future.

The TESS observatory uses an array of wide-field cameras to perform a survey of 85% of the sky.… Read more

Exoplanets Discoveries Flood in From TESS

NASA’s Transiting Exoplanet Survey Satellite (TESS) has hundreds of “objects of interest” waiting to be confirmed as planets in the data from the space telescope’s four cameras.  These three were the first confirmed TESS discoveries, identified last year during its first three months of observing. By the time the mission is done, TESS’s wide-field cameras will have covered the whole sky in search of transiting exoplanets around 200,000 of the nearest (and brightest) stars. (NASA / MIT / TESS)

The newest space telescope in the sky — NASA’s Transiting Exoplanet Survey Satellite, TESS — has been searching for exoplanets for less than a year, but already it has quite a collection to its name.

The TESS mission is to find relatively nearby planets orbiting bright and stable suns, and so expectations were high from the onset about the discovery of important new planets and solar systems.  At a meeting this week at the Massachusetts Institute of Technology devoted to TESS  results,  principal investigator George Ricker pronounced the early verdict.

The space telescope, he said,  “has far exceeded our most optimistic hopes.”  The count is up to 21 new planets and 850 additional  candidate worlds waiting to be confirmed.

Equally or perhaps more important is that the planets and solar systems being discovered promise important results.  They have not yet included any Earth-sized rocky planet in a sun’s habitable zone — what is generally considered the most likely, though hardly the only, kind of planet to harbor life — but they did include planets that offer a great deal when it comes to atmospheres and how they can be investigated.

This infographic illustrates key features of the TOI 270 system, located about 73 light-years away in the southern constellation Pictor. The three known planets were discovered by NASA’s Transiting Exoplanet Survey Satellite through periodic dips in starlight caused by each orbiting world. Insets show information about the planets, including their relative sizes, and how they compare to Earth. Temperatures given for TOI 270’s planets are equilibrium temperatures, (NASA’s Goddard Space Flight Center/Scott Wiessinger)

One of the newest three-planet system is called TOI-270, and it’s about 75 light years from Earth. The star at the center of the system is a red dwarf, a bit less than half the size of the sun.

Despite its small size, it’s brighter than most of the nearby stars we know host planets. And it’s stable, making its solar system especially valuable.

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Our Ever-Growing Menagerie of Exoplanets

While we have never seen an exoplanet with anything near this kind of detail, scientists and artists now do know enough to represent them with characteristics that are plausible, given what is known about them..  (NASA)

With so many exoplanets already detected, with the pace of discovery continuing to be so fast, and with efforts to find more distant worlds so constant and global,  it’s easy to become somewhat blase´ about new discoveries.  After so many “firsts,” and so many different kinds of planets found in very different ways, it certainly seems that some of the thrill may be gone.

Surely the detection of a clearly “Earth-like planet” would cause new excitement — one that is not only orbiting in the habitable zone of its host star but also has signs of a potentially nurturing atmosphere in a generally supportive cosmic neighborhood.

But while many an exoplanet has been described as somewhat “Earth-like” and potentially habitable, further observation has consistently reduced the possibility of the planets actually hosting some form of biology.  The technology and knowledge base needed to find distant life is surely advancing, but it may well still have a long way to go.

In just the last few days, however, a slew of discoveries have been reported that highlight the allure and science of our new Exoplanet Era.  They may not be blockbusters by themselves, but they are together part of an immense scientific exploration under way, one that is re-shaping our understanding of the cosmos and preparing us for bigger discoveries and insights to come.


Already 3,940 exoplanets have been identified (as of April 17) with an additional 3,504 candidates waiting to be confirmed or discarded.  this is but the start since it is widely held now that virtually every star out there has a planet, or planets, orbiting it.   That’s billions of billions of planets.  This image is a collection of NASA exoplanet renderings.

What I have in mind are these discoveries:

  • The first Earth-sized planet detected by NASA’s year-old orbiting telescope TESS (Transiting Exoplanet Survey Satellite.)  TESS is designed to find planets orbiting massive stars in our near neighborhood, and it has already made 10 confirmed discoveries.  But finding a small exoplanet — 85 percent the size of Earth — is a promising result for a mission designed to not only locate as many as 20,000 new exoplanets, but to find 500 to 1,000 the rough size of Earth or SuperEarth. 
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NASA’s Planet-Hunter TESS Has Just Been Launched to Check Out the Near Exoplanet Neighborhood


A SpaceX Falcon 9 rocket transporting the TESS satellite lifts off from launch complex 40 at the Cape Canaveral Air Force Station in Cape Canaveral, Fla., Wednesday, April 18, 2018. The space telescope will survey almost the entire sky, staring at the brightest, closest stars in an effort to find any planets that might be encircling them. (AP Photo/John Raoux)

On January 5, 2010, NASA issued  landmark press release : the Kepler Space Telescope had discovered its first five new extra-solar planets.

The previous twenty years had seen the discovery of just over 400 planets beyond the solar system. The majority of these new worlds were Jupiter-mass gas giants, many bunched up against their star on orbits far shorter than that of Mercury. We had learnt that our planetary system was not alone in the Galaxy, but small rocky worlds on temperate orbits might still have been rare.

Based on just six weeks of data, these first discoveries from Kepler were also hot Jupiters; the easiest planets to find due to their large size and swiftly repeating signature as they zipped around the star. But expectations were high that this would be just the beginning.

“We expected Jupiter-size planets in short orbits to be the first planets Kepler could detect,” said Jon Morse, director of the Astrophysics Division at NASA Headquarters at the time the discovery was announced. “It’s only a matter of time before more Kepler observations lead to smaller planets with longer period orbits, coming closer and closer to the discovery of the first Earth analog.”

Morse’s prediction was to prove absolutely right. Now at the end of its life, the Kepler Space Telescope has found 2,343 confirmed planets, 30 of which are smaller than twice the size of the Earth and in the so-called “Habitable Zone”, meaning they receive similar levels of insolation –the amount of solar radiation reaching a given area–to our own planet.

Yet, the question remains: were any of these indeed Earth analogs?

In just a few decades, thanks to Kepler, the Hubble Space Telescope and scores of astronomers at ground-based observatories, we have gone from suspecting the presence of exoplanets to knowing there are more exoplanets than stars in our galaxy. (NASA/Ames Research Station; Jessie Dotson and Wendy Stenzel)

It was a question that Kepler was not equipped to answer. Kepler identifies the presence of a planet by looking for the periodic dip in starlight as a planet passes across the star’s surface.… Read more

The Just-Approved European ARIEL Mission Will Be First Dedicated to Probing Exoplanet Atmospheres


The Ariel space telescope will explore the atmospheres of exoplanets. (Artist impression, ESA)

The European Space Agency (ESA) has approved the ARIEL space mission—the world’s first dedicated exoplanet atmosphere sniffer— to fly in 2028.

ARIEL stands for the “Atmospheric Remote-sensing Infrared Exoplanet Large-Survey mission.” It is a space telescope that can detect which atoms and molecules are present in the atmosphere of an exoplanet.

The mission was selected as a medium class mission in the ESA Cosmic Vision program; the agency’s decadal plan for space missions that spans 2015 – 2025.

One of the central themes for Cosmic Vision is uncovering the conditions for planet formation and the origins of life. This has resulted in three dedicated exoplanet missions within the same decadal plan. ARIEL will join CHEOPS (in the small class mission category) and PLATO (another medium class mission) in studying worlds beyond our own sun.

Yet ARIEL is a different type of telescope from the other exoplanet-focused missions. To understand why, we need to examine what properties we can observe of these distance exo-worlds.

Exoplanet missions can be broadly divided into two types. The first type are the exoplanet hunter missions that search the skies for new worlds.

These are spacecraft and instruments such as the NASA Kepler Space Telescope. Since it launched in 2009, Kepler has been an incredibly prolific planet hunter. The telescope has found thousands of planets, modeled their orbits and told us about the distribution of their sizes.

From Kepler, we have learnt that planet formation is common, that it can occur around stars far different from our own sun, and that these worlds can have a vast range of sizes and myriad of orbits quite unlike our own Solar System.


Current and future (or proposed) space missions with capacities to identify and characterize exoplanets.  The very productive CoRotT mission is, however, missing.  It searched for and found many exoplanets from 2006 to 2013.  (NASA,ESA: T. Wynne/JPL, composited by Barbara Aulicino)


However, the information Kepler is able to provide about individual planets is very limited. The telescope monitors stars for the tiny drop in light as the planet crosses (or “transits”) the star’s surface. From this, astronomers can measure the radius of the planet and its orbital period but nothing about the planet’s surface conditions.

The result is a little like knowing the number of students and distribution of grades in a particular school, but having no idea if the student who sits in the third row actually likes math.… Read more

Storming the One-Meter-Per-Second Barrier

Kitt Peak National Observatory mountain top at Dusk looking north. Visible in the picture are the NOAO 4-meter Mayall, the Steward Observatory 90-inch, the University of Arizona Lunar and Planetary Laboratory Spacewatch Telescopes, LOTIS, 0.4-meter Visitor Center Telescope, Case Western Reserve University Observatory and the SARA Observatory. Credit: P. Marenfeld (NOAO/AURA/NSF)

The Kitt Peak National Observatory, on the Tohono O’odham reservation outside Tucson, will be home to a next-generation spectrometer and related system which will allow astronomers to detect much smaller exoplanets through the radial velocity method.  P. Marenfeld (NOAO/AURA/NSF)

When the first exoplanet was identified via the radial velocity method, the Swiss team was able to detect a wobble in the star 51 Pegasi at a rate of 50 meters per second.   The wobble is the star’s movement back and forth caused by the gravitational pull of the planet, and in that first case it was dramatic — the effects of a giant Jupiter-sized planet orbiting extremely close to the star.

Many of the early exoplanet discoveries were of similarly large planets close to their host stars, but it wasn’t because there are so many of them in the cosmos.  Rather, it was a function of the capabilities of the spectrographs and other instruments used to view the star.  They were pioneering breakthroughs, but they didn’t have the precision needed to measure wobbles other than the large, dramatic ones caused by a close-in, huge planet.

That was the mid 1990s, and radial velocity astronomers have worked tirelessly since to “beat down” that 50 meters per second number.  And twenty years later, radial velocity astronomers using far more precise instruments and more refined techniques have succeeded substantially:  1 meter per second of wobble is now achieved for the quietest stars.  That has vastly improved their ability to find smaller exoplanets further from their stars and is a major achievement.  But it has nonetheless been a major frustration for astronomers because to detect terrestrial exoplanets in the Earth-sized range, they have to get much more precise  — in the range of tens of centimeters per second.

A number of efforts to build systems that can get that low are underway, most notably the ESPRESSO spectrograph scheduled to begin work on the High Accuracy Radial Vlocity Planet Searcher (HARPS) in Chile next year. Then earlier this month an ambitious NASA-National Science Foundation project was awarded to Penn State University to join the race.  The next-generation spectrograph is scheduled to be finished in 2019 and installed at the Kitt Peak National Observatory in Arizona, and its stated goal is to reach the 20 to 30 centimeters per second range.

Suvrath Mahadevan, an assistant professor at Penn State, is principal investigator for the project.  It is called NEID, which means ‘to see’ in the language of the Tohono O’odham, on whose land the Kitt Peak observatory is located.… Read more

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