Tag Archives: TESS

A Snapshot of Gliese 486b's journey around its parent star (Render Area)

Nearby Super-Earth could be perfect for atmospheric investigation

An international team of astronomers has discovered a nearby exoplanet orbiting a red dwarf star that is perfect for deeper investigation. In particular, this exoplanet could be a prime target for precise atmospheric measurements, something that, for planets outside the solar system, has so-far eluded astronomers.

The team’s findings documenting the discovery of this relatively close super-Earth–so-called because they have a mass greater than our planet but still lower than planets like Uranus and Neptune which are classified as ‘ice giants’–are published in the latest edition of the journal Science.

The team discovered Gliese 486 b whilst surveying 350 small red dwarf stars for signs of low-mass planets using the CARMENES spectrograph mounted on the 3.5m telescope at the Calar Alto Observatory telescope, Spain. The exoplanet was found due to the ‘wobble’ it caused in the orbit of its parent star.

A snapshot of the super-Earth Gliese 486 b as it orbits a red dwarf star (Render Image)

“Our team is searching primarily for Earth-like and super-Earth planets orbiting nearby stars. In this case, we have found a nearby super-Earth, just 26 light-years away orbiting a small star every 1.5 or so Earth days,” Karen Collins, an astronomer at the Center for Astrophysics, Harvard & Smithsonian, and a co-author on the paper tells ZME Science. “We were certainly excited to have found a transit signal in the light curve of a star that is so close to the Sun in astronomical terms.

“We quickly realized that Gliese 486 b, with radial velocity mass measurements in hand, would likely become a prime target for additional detailed follow-up studies, particularly atmospheric investigations.”

Karen Collins, Center for Astrophysics, Harvard & Smithsonian

These investigations could include searching for the conditions necessary for life, or even for biomarkers left behind by simple lifeforms.

The astronomers were able to spot Gliese 486 b thanks to the ‘wobble’ it caused in its parent star’s orbit (Render Area)

Colins continues by explaining that it is Gliese 486 b’s proximity–it is the third closest transiting exoplanet yet to be uncovered– that, amongst other things like its temperature, makes it a good candidate for more in-depth study. “Because Gliese 486 b is so close to the solar system, relative to most known transiting exoplanets, we may be able to probe the atmosphere of the planet using the upcoming James Webb Space Telescope and possibly other telescopes,” she explains.

That is, of course, if it actually has an atmosphere.

What We Know About Gliese 486 b So Far…

Whilst the team of astronomers may not yet be certain that Gliese 486 b has an atmosphere, there are some things that they do know about the exoplanet and its red dwarf home star.

Artistic impression of the surface of the newly discovered hot super-Earth Gliese 486b. With a
temperature of about 700 Kelvin (430 °C), Gliese 486b possibly has an atmosphere (Render Area)

“It is only about 30% larger than Earth but has a mass of about 2.8 times that of our planet,” study author Trifon Trifonov, Max Planck Institute for Astronomy, explains to ZME Science. The researcher adds that models suggest that the exoplanet’s composition is similar to Venus and Earth, including a metallic core. “Anyone standing on Gliese 486 b would feel a gravitational pull that is about 70% stronger than what we experience on Earth.”

In addition to being denser than the earth, Gliese 486 b is also much hotter according to Trifon. This is because the exoplanet revolves around its host star on a circular orbit every 1.47 days, with one side permanently pointing towards its parent star.

“The proximity to the red dwarf Gliese 486 heats the planet significantly, making its landscape hot and dry, interspersed with volcanos and glowing lava rivers,” Trifon says. “There are quite a few super-Earth type exoplanets already discovered. All of these exoplanets are exceptional on their own. In this context, the physical characteristics of Gliese 486 b are not uncommon. However, the proximity of Gliese 486 b, allowed us to measure its mass with unprecedented precision, thanks to observations done with the CARMENES and the MAROON-X instruments.”

From the information the astronomers do possess regarding Gliese 486 b, especially its mass, Collins adds that the clues it also has an appreciable atmosphere are in place.

“Because we do know that the planet surface gravity is relatively high–about 70% stronger than Earth–we believe that there is a chance the planet may have retained an appreciable atmosphere.”

Karen Collins, Center for Astrophysics, Harvard & Smithsonian

Atmospheric Investigations

Using NASA’s Transiting Exoplanet Survey Satellite (TESS) spacecraft the astronomers were able to deduce that Gliese 486 b periodically crosses the stellar disk of its parent red dwarf star, a rare and fortuitous event.

“For transiting planets like Gliese 486 b, we have two primary methods to probe the atmospheres, if they exist,” Collins continues. “Transit spectroscopy allows us to study the planet’s atmosphere as the planet passes in front of the star from the telescope’s perspective.”

Collins says that should the exoplanet possess an atmosphere part of the light from its parent star that reaches our telescopes will have been filtered through this. This means that the light profile filtered by the atmosphere can be compared to an unfiltered version when the planet is not in front of the star.”By comparing the in-transit spectrum of the star with a spectrum of the star when the planet is not transiting, we can isolate atmospheric signals from the planet and possibly detect some of the components of the atmosphere.”

As Gliese 486 b transits the face of its parent star, astronomers should be able to use transit spectroscopy to investigate its atmosphere. (Render Area)

The second method detailed by Collins involves the detection of radiation directly from an exoplanet’s hot surface as it occupies different orbital phases across the star’s face. The emission spectrum that gives this technique its name–emission spectroscopy–reveals characteristic traits that indicate the presence of certain elements emitting and absorbing light in the exoplanet’s atmosphere.

“Its temperature of around 700 Kelvin makes it suitable for emission spectroscopy and phase curve studies in search of an atmosphere,” adds Trifonov.

The Golden Age of Exoplanet Science

Concluding our interview I ask Collins and Trionov if we are entering a ‘Golden Age’ for exoplanet science. They are both quick to correct me. “I would say we are living in it!” Trinov exclaims. “During the past three decades, astronomers have discovered thousands of exoplanets, and the number is increasing daily.

“Every day, we enhance our knowledge about the physical properties of exoplanets, their formation, and evolution.”

Trifon Trifonov, Max Planck Institute for Astronomy
NASA engineers are putting the finishing touches to the James Webb Space Telescope. The instrument will play a crucial role is the future investigation of super-Earth exoplanets. (NASA)

Collins is equally assured that exoplanet science is in its prime, but adds that there is no decline in sight. “Frankly, I believe we have been in the golden age of exoplanet science for over a decade now,” the astronomer says. “Even so, with the advent of TESS to discover and measure the size of nearby small transiting planets, precise radial velocity machines like that of the CARMENES consortium and the MAROON-X instrument to measure their masses, and soon the James Webb Space Telescope to investigate their atmospheres, it’s fair to say that we are entering the golden age of well-characterized small planet exoplanet science.”

And Collins is clear how lucky she regards herself for just being involved with astronomy at this crucial juncture in its history. “I am excited to be involved in the search for and characterization of Earth-sized and Super-Earth planets such as Gliese 486 b,” says explains enthusiastically. “Precise atmospheric measurements are likely around the corner! What will this relatively new scientist from a small but progressive astrophysics program at a school in Kentucky be involved with next? Will we soon discover an Earth twin with an Earth-like atmosphere or even signs of life in an atmosphere?

“It is almost as if I’m living in a series of Star Trek. I can’t wait to see what we discover next!”

Karen Collins, Center for Astrophysics, Harvard & Smithsonian

NASA planet-hunting satellite finds its first Earth-sized alien world

A picture of TOI 700 with one of the three planets found by TESS (NASA’s Goddard Space Flight Center)

A team of researchers announced on January 6 that NASA’s Transiting Exoplanet Survey Satellite (TESS) discovered its first Earth-sized planet which has the possibility to harbor oceans. The same day, it was also revealed that she had found her first circumbinary planet, a world orbiting two stars.

Coined TOI 700 d (TOI is short for “Tess Object of Interest”), the exoplanet is located 101.5 light-years away and is one of only a few Earth-sized worlds discovered in its star’s habitable zone so far. The discovery was confirmed by NASA’s Spitzer Space Telescope.

TESS monitors large swaths of the sky, called sectors, for 27 days at a time. This long stare allows the satellite to track changes in stellar brightness caused by an orbiting planet crossing in front of its star from our perspective, an event called a transit.

The telescope, which launched in April 2018, hunts for planets using the “transit method,” where it looks for telltale dips in stellar brightness that is caused by orbiting worlds crossing their parent stars’ faces from the satellite’s perspective. This was the same strategy used by NASA’s Kepler space telescope, which discovered about 70 percent of the roughly 4,000 known exoplanets.

“TESS was designed and launched specifically to find Earth-sized planets orbiting nearby stars,” said Paul Hertz, astrophysics division director at NASA Headquarters in Washington. “Planets around nearby stars are easiest to follow-up with larger telescopes in space and on Earth. Discovering TOI 700 d is a key science finding for TESS. Confirming the planet’s size and habitable zone status with Spitzer is another win for Spitzer as it approaches the end of science operations this January.”

TOI 700 d was one of three planets discovered orbiting the star TOI 700. It is the outermost known planet in the system and the only one in the habitable zone. It’s 20 percent larger than Earth, orbits every 37 days and receives from its star 86 percent of the energy that the Sun provides to Earth. The innermost planet discovered, TOI 700 b, is roughly Earth-sized and completes a full orbit every 10 days. The center planet, TOI 700 c, is 2.6 times bigger than Earth, meaning it’s likely a gassy “mini-Neptune,” and circles TOI 700 every 16 days.

TOI 700 is a small, cool M dwarf star located just over 100 light-years away in the southern constellation Dorado. It measures roughly 40 percent of our Sun’s mass and size and has about half its surface temperature. The star appears in 11 of the 13 sectors TESS observed during the mission’s first year, and scientists caught multiple transits by its three planets. It was originally misclassified in the TESS database as being more similar to the Sun, which meant the planets appeared larger and hotter than they really are.

“When we corrected the star’s parameters, the sizes of its planets dropped, and we realized the outermost one was about the size of Earth and in the habitable zone,” said Emily Gilbert, a graduate student at the University of Chicago.

Normally planets which orbit red dwarfs like TOI 700 aren’t a good place to look for life due to powerful flares from the star which will generally fry a planet’s atmosphere. However, TOI 700 d seems to be an exception to this norm. It is also tidally locked, which means that one side is always in daylight.

“In 11 months of data, we saw no flares from the star, which improves the chances TOI 700 d is habitable and makes it easier to model its atmospheric and surface conditions,” said Gilbert.

Because TOI 700 is bright, nearby, and shows no sign of stellar flares, the system is a prime candidate for precise mass measurements by current ground-based observatories. These measurements could confirm scientists’ estimates that the inner and outer planets are rocky and the middle planet is made of gas.

An artist’s depiction of K2-18b orbiting its host star (ESA/Hubble, M. Kornmesser)

This comes on the heels of the detection of water vapor in September 2019 on a potentially habitable planet for the first time. This planet, called K2-18b and discovered by the Kepler telescope, is a super-Earth that orbits a red dwarf star 110 light-years away. K2-18b is the only known exoplanet with water vapor, an atmosphere, and a temperature range that could support liquid water on its surface.

The other first for TESS was the discovery of planet TOI 1338 b which resides in the system TOI 1338, 1,300 light-years away in the constellation Pictor. The two stars there orbit each other every 15 days. One is about 10 percent more massive than the Sun, while the other is cooler, dimmer and only one-third the Sun’s mass.

TOI 1338 b is the only known planet in the system. It’s around 6.9 times larger than Earth, or between the sizes of Neptune and Saturn. The planet orbits in almost exactly the same plane as the stars, so it experiences regular stellar eclipses.

Planets orbiting two stars are usually harder to detect than those orbiting just one. TOI 1338 b’s transits are irregular, between every 93 and 95 days, and vary in depth and duration thanks to the orbital motion of its stars. TESS only sees the transits crossing the larger star; the transits of the smaller star are too faint to detect.

Future missions may be able to identify whether the TESS’s discoveries have atmospheres and, if so, even determine their compositions.

NASA’s brand new TESS telescope is already sending back impressive footage

NASA’s Transiting Exoplanet Survey Satellite (TESS) started its scientific activity on July 25, but, even before that, TESS managed to snap some awesome images of a passing comet — only discovered a month ago.

Image credits: Massachusetts Institute of Technology/NASA’s Goddard Space Flight Center.

The comet is named C/2018 N1 and is located some 48 million kilometers (29 million miles) from Earth, in the southern constellation Piscis Austrinus — the Latin name for “southern fish”. The comet can be seen moving right to left, orbiting the Sun, leaving behind a “tail” — which consists of gases carried away from by an outflow from the Sun called the solar wind, according to NASA.

But the comet isn’t the only interesting thing visible in the images, which also feature asteroids and stars. If you look closely, you can see some stars shifting from white to black and to white again. This comes as a result of image processing, which highlights variable stars. These stars change brightness either as a result of pulsation, rapid rotation, or by eclipsing binary neighbors.

Artistic depiction of the TESS telescope. Image credits: NASA.

TESS’ main job, however, isn’t to keep an eye out for comets and variable stars. In a two-year survey of the solar neighborhood, TESS will monitor more than 200,000 stars for temporary drops in brightness caused by planetary transits. This is the most common way of detecting a planet. Since planets don’t have their own light, it’s difficult to see them directly so, instead, they look at stars and look for dips in its luminosity, which can be indicative of a planet passing between the star and the Earth. The nature of the dip can then be used to determine certain parameters of the planet. The vast majority of the 3,815 confirmed exoplanets have been discovered using this method.

TESS is the first-ever spaceborne all-sky transit survey. It will scout the sky, looking for planets ranging from Earth-sized to gas giants, around a wide range of stellar types and orbital distances, primarily focusing on the brightest stars in Earth’s vicinity. No ground-based survey can achieve this feat, due to atmospheric perturbations.

Since the comet footage, TESS has already started its main activity. Hopefully, it won’t be long until the first results start coming in, and we have a new batch of exoplanets to study and understand.

You can read more about TESS on its NASA website, and follow its news on Twitter. It’s worth it.

Meet TESS — he’ll be finding exoplanets for the next few years

NASA’s future planet hunter has arrived — and it’s set for glory.

Like Kepler, TESS will be using the transit method illustrated here. Essentially, as a planet passes in front of its star, it creates a dip in the star’s luminosity, which can be detected. This is called a transit. Image credits: NASA Goddard Space Flight Center.

The Kepler telescope ushered in a new age of space exploration, enabling astronomers to discover thousands of exoplanets. It was a magnificent tool that was successful beyond our wildest dreams. However, it’s nearing the end of its lifetime. Crippled and almost out of fuel, Kepler is fast approaching its conclusion. But rest assured — NASA already has its replacement prepared.

NASA’s Transiting Exoplanet Survey Satellite, or TESS, will be carried in outer space by SpaceX’s Falcon 9 rocket in just a few days, on April 16, where it’s set for even greater success than Kepler. Think of it this way: if Kepler was looking through a straw, TESS will be visualizing 90% of the night sky. In other words, Kepler had a very narrow surveying angle, whereas TESS will have a much broader angle — overall, the area covered by TESS will be about 350 times larger than what Kepler could witness. This is largely owed to its unusual orbit — TESS has a never-before-used orbit which was designed to minimize the time the telescope spends obstructed by Earth or the Moon. However, there’s a trade-off.

TESS will observe the southern skies first, and then the north. The survey strips will overlap near the celestial poles, creating pockets of sky that will have longer observation times. Conveniently, the patches of sky that will be observed the most by TESS are also in ideal viewing locations for the future James Webb Space Telescope, which will be able to study planets that TESS finds in more detail. Image credits: NASA / MIT.

TESS traded resolution for this larger angle — whereas Kepler was able to find planets up to 3,000 light years away, most of the exoplanets TESS finds will be just 30 to 300 light years away. Kepler has already discovered over 2,500 planets, with another 2,500 planet candidates being currently under review. TESS is expected to find 3,000 to 4,000 planets orbiting M-dwarves — relatively small and cold stars, red dwarfs of the M spectral type. Red dwarfs are by far the most common type of star in the Milky Way, but because of their low luminosity, they are difficult to study.

Currently, TESS is at Kennedy Space Center’s Payload Hazardous Servicing Facility, getting its thrusters fueled up for flight — and we couldn’t be more excited for this mission.