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TESS satellite uncovers its ‘first nearby super-Earth’

TESS satellite uncovers its ‘first nearby super-Earth’

An international team of astronomers led by Cornell’s Lisa Kaltenegger has characterized the first potentially habitable world outside of our own solar system.

Located about 31 light-years away, the super-Earth planet – named GJ 357 d – was discovered in early 2019 owing to NASA’s Transiting Exoplanet Survey Satellite (TESS), a mission designed to comb the heavens for exoplanets, according to their new modeling research in the Astrophysical Journal Letters.

“This is exciting, as this is TESS’s first discovery of a nearby super-Earth that could harbor life – TESS is a small, mighty mission with a huge reach,” said Kaltenegger, associate professor of astronomy, director of Cornell’s Carl Sagan Institute and a member of the TESS science team.

The exoplanet is more massive than our own blue planet, and Kaltenegger said the discovery will provide insight into Earth’s heavyweight planetary cousins. “With a thick atmosphere, the planet GJ 357 d could maintain liquid water on its surface like Earth, and we could pick out signs of life with telescopes that will soon be online,” she said.

Astronomers from the Institute of Astrophysics of the Canary Islands and the University of La Laguna, both in Spain, announced the discovery of the GJ 357 system July 31 in the journal Astronomy & Astrophysics. They showed that the distant solar system – with a diminutive M-type dwarf sun, about one-third the size of our own sun – harbors three planets, with one of those in that system’s habitable zone: GJ 357 d.

Last February, the TESS satellite observed that the dwarf sun GJ 357 dimmed very slightly every 3.9 days, evidence of a transiting planet moving across the star’s face. That planet was GJ 357 b, a so-called “hot Earth” about 22% larger than Earth, according to the NASA Goddard Space Flight Center, which guides TESS.

Follow-up observations from the ground led to the discovery of two more exoplanetary siblings: GJ 357 c and GJ 357 d. The international team of scientists collected Earth-based telescopic data going back two decades – to reveal the newly found exoplanets’ tiny gravitational tugs on its host star, according to NASA.

Exoplanet GJ 357 c sizzles at 260 degrees Fahrenheit and has at least 3.4 times Earth’s mass. However, the system’s outermost known sibling planet – GJ 357 d, a super-Earth – could provide Earth-like conditions and orbits the dwarf star every 55.7 days at a distance about one-fifth of Earth’s distance from the sun. It is not yet known if this planet transits its sun.

Kaltenegger, doctoral candidate Jack Madden and undergraduate student Zifan Lin ’20 simulated light fingerprints, climates and remotely detectable spectra for a planet that could range from a rocky composition to a water world.

Madden explained that investigating new discoveries provides an opportunity to test theories and models. “We built the first models of what this new world could be like,” he said. “Just knowing that liquid water can exist on the surface of this planet motivates scientists to find ways of detecting signs of life.”

Lin described the work from an undergraduate perspective: “Working on a newly discovered planet is something of a dream come true. I was among the first group of people to model its spectra, and thinking about this still overwhelms me.”

In a nod to her institute’s namesake, the late Cornell professor Carl Sagan, Kaltenegger said: “If GJ 357 d were to show signs of life, it would be at the top of everyone’s travel list – and we could answer a 1,000-year-old question on whether we are alone in the cosmos.”

In addition to Kaltenegger, Madden and Lin, co-authors of “The Habitability of GJ 357d: Possible Climates and Observability,” include Sarah Rugheimer, Oxford University; Antigona Segura, National Autonomous University of Mexico (UNAM); Rafael Luque and Eric Pallé, both of the Institute of Astrophysics of the Canary Islands and the University of La Laguna; and Néstor Espinoza, Max Planck Institute for Astronomy, Germany.

Tour the GJ 357 system, located 31 light-years away in the constellation Hydra. Astronomers confirming a planet candidate identified by NASA’s Transiting Exoplanet Survey Satellite subsequently found two additional worlds orbiting the star.

Journal Reference: Astronomy & Astrophysics

Materials provided by Cornell University

TESS discovers three new planets nearby, including temperate “sub-Neptune”

TESS discovers three new planets nearby, including temperate “sub-Neptune”

NASA’s Transiting Exoplanet Survey Satellite, or TESS, has discovered three new worlds that are among the smallest, nearest exoplanets known to date. The planets orbit a star just 73 light-years away and include a small, rocky super-Earth and two sub-Neptunes — planets about half the size of our own icy giant.

The sub-Neptune furthest out from the star appears to be within a “temperate” zone, meaning that the very top of the planet’s atmosphere is within a temperature range that could support some forms of life. However, scientists say the planet’s atmosphere is likely a thick, ultradense heat trap that renders the planet’s surface too hot to host water or life.

Nevertheless, this new planetary system, which astronomers have dubbed TOI-270, is proving to have other curious qualities. For instance, all three planets appear to be relatively close in size. In contrast, our own solar system is populated with planetary extremes, from the small, rocky worlds of Mercury, Venus, Earth, and Mars, to the much more massive Jupiter and Saturn, and the more remote ice giants of Neptune and Uranus.

There’s nothing in our solar system that resembles an intermediate planet, with a size and composition somewhere in the middle of Earth and Neptune. But TOI-270 appears to host two such planets: both sub-Neptunes are smaller than our own Neptune and not much larger than the rocky planet in the system.

Astronomers believe TOI-270’s sub-Neptunes may be a “missing link” in planetary formation, as they are of an intermediate size and could help researchers determine whether small, rocky planets like Earth and more massive, icy worlds like Neptune follow the same formation path or evolve separately.

TOI-270 is an ideal system for answering such questions, because the star itself is nearby and therefore bright, and also unusually quiet. The star is an M-dwarf, a type of star that is normally extremely active, with frequent flares and solar storms. TOI-270 appears to be an older M-dwarf that has since quieted down, giving off a steady brightness, against which scientists can measure many properties of the orbiting planets, such as their mass and atmospheric composition.

“There are a lot of little pieces of the puzzle that we can solve with this system,” says Maximilian Günther, a postdoc in MIT’s Kavli Institute for Astrophysics and Space Research and lead author of a study published today in Nature Astronomy that details the discovery. “You can really do all the things you want to do in exoplanet science, with this system.”

Compare and contrast worlds in the TOI 270 system with these illustrations. Temperatures given for TOI 270 planets are equilibrium temperatures, calculated without the warming effects of any possible atmospheres. Credit: NASA’s Goddard Space Flight Center

A planetary pattern

Günther and his colleagues detected the three new planets after looking through measurements of stellar brightness taken by TESS. The MIT-developed satellite stares at patches of the sky for 27 days at a time, monitoring thousands of stars for possible transits — characteristic dips in brightness that could signal a planet temporarily blocking the star’s light as it passes in front of it.

The team isolated several such signals from a nearby  star, located 73 light years away in the southern sky. They named the star TOI-270, for the 270th “TESS Object of Interest” identified to date. The researchers used ground-based instruments to follow up on the star’s activity, and confirmed that the signals are the result of three orbiting exoplanets: planet b, a rocky super-Earth with a roughly three-day orbit; planet c, a sub-Neptune with a five-day orbit; and planet d, another sub-Neptune slightly further out, with an 11-day orbit.

Günther notes that the planets seem to line up in what astronomers refer to as a “resonant chain,” meaning that the ratio of their orbits are close to whole integers — in this case, 3:5 for the inner pair, and 2:1 for the outer pair — and that the planets are therefore in “resonance” with each other. Astronomers have discovered other small stars with similarly resonant planetary formations. And in our own solar system, the moons of Jupiter also happen to line up in resonance with each other.

“For TOI-270, these planets line up like pearls on a string,” Günther says. “That’s a very interesting thing, because it lets us study their dynamical behavior. And you can almost expect, if there are more planets, the next one would be somewhere further out, at another integer ratio.”

“An exceptional laboratory”

TOI-270’s discovery initially caused a stir of excitement within the TESS science team, as it seemed, in the first analysis, that planet d might lie in the star’s habitable zone, a region that would be cool enough for the planet’s surface to support water, and possibly life. But the researchers soon realized that the planet’s atmosphere was probably extremely thick, and would therefore generate an intense greenhouse effect, causing the planet’s surface to be too hot to be habitable.

But Günther says there is a good possibility that the system hosts other planets, further out from planet d, that might well lie within the habitable zone. Planet d, with an 11-day orbit, is about 10 million kilometers out from the star. Günther says that, given that the star is small and relatively cool — about half as hot as the sun — its habitable zone could potentially begin at around 15 million kilometers. But whether a planet exists within this zone, and whether it is habitable, depends on a host of other parameters, such as its size, mass, and atmospheric conditions.

Fortunately, the team writes in their paper that “the host star, TOI-270, is remarkably well-suited for future habitability searches, as it is particularly quiet.” The researchers plan to focus other instruments, including the upcoming James Webb Space Telescope, on TOI-270, to pin down various properties of the three planets, as well as search for additional planets in the star’s habitable zone.

“TOI-270 is a true Disneyland for exoplanet science, and one of the prime systems TESS was set out to discover,” Günther says. “It is an exceptional laboratory for not one, but many reasons — it really ticks all the boxes.”

Materials provided by Massachusetts Institute of Technology

Astronomers Have Discovered a Peculiar Rocky Exoplanet With Three Glowing Red Suns

Astronomers have discovered a strange rocky exoplanet in a triple-star system

Astronomers have recently discovered a new strange rocky Exoplanet in a triple star system. Our sun is the only star in our solar system, but out in the wider universe stars often are locked in a dance with other stars and orbit at a mutual centre of gravity.

A catchy name was allotted, LTT 1445Ab since it orbits the primary star of the three red dwarfs of system LTT 1445, located around 22.5 light-years away from earth. Astronomer Jennifer Winters of the Harvard-Smithsonian Center said that on standing on that planet’s surface, there will be three suns in the sky with two of them far away and small in size. The paper is submitted to The Astronomical Journal and can found on arXiv.

The planet was discovered by TESS, the planet-hunting space telescope of NASA which is designed to find exoplanets that pass between us and their home star by detecting the telltale dimming since the planet blocks a certain percentage of light. Scientists can place constraints on mass and size of the planet due to the depth of dimming, tiny star movements since it is slightly pulled by the gravity of planet.

The LTT 1445Ab varies from the HD131399Ab which was discovered back in 2016. It was bigger with a 550-year orbit around one of the star in a triple system 340 light-years away from earth. The new planet is only 1.35 times the size of Earth and 8.4 times Earth’s mass and thus is denser than Earth.

The size and mass put it in the category of rocky planets like Mars, Venus etc. and is not a gas or ice giant. The chances of habitability are low. The surface temperature is expected to reach scorching 428 Kelvin and it whips around its star once every 5.36 Earth days.

Astronomers predict that LTT 1445Ab might have an atmosphere like any other rocky planet and might be a good place to test the detection of gases like methane and carbon dioxide. The atmosphere dims the starlight and can also change it based on chemical composition. The atmospheric components can be found out based on the spectrum of light through the atmosphere.

The current technology is not well developed for this task but may become possible with the Hubble’s successor, the James Webb Space Telescope which will launch in 2021. LTT 1445Ab is a good candidate for observations as there will be plenty of observations and is relatively very close in a cosmic scale at a distance of 22.5 light-years away. The dwarf star is bright enough to back-light the atmosphere but not bright enough to outshine the planet. Rocky planets are relatively common in the close orbits around red dwarf stars. Hence, looking at the LTT1445Ab closer can tell us what to expect on such planets.

Journal Reference: arXiv

TESS technology high resolution

NASA’s TESS detects Earth-sized planet for the first time

Transiting Exoplanet Survey Satellite (TESS), NASA’s space telescope for its Explorer Program has discovered a nearby system which has an Earth-sized planet. Along with it, there is also a warm planet nearly the size of Neptune. The work carried out by a group of astronomers from Carnegie Institution for Science was published in the Astrophysical Journal Letters.

For confirming the planetary nature of the signals from TESS and to calculate the mass of the discovered sub-Neptune planet, the Planet Finder Spectrograph of Magellan II telescope was used which is located at the Las Campanas Observatory, Chile.

The Planet Finder Spectrograph has been built by Shectman and Crane and it functions on the technique known as radial velocity method. Right now, this is the only way of calculating the masses of the planets. Without finding the mass, it is very tough to find out the density of the planet or even the general composition.

This method is advantageous for both influence of gravity of a star orbiting it as well as the planet’s gravity also affects the star in turn. This instrument enables astronomers to find out the tiny wobbles that are reduced because of the planet’s gravity in the star’s orbit.

The newly searched planet, the sub-neptune, HD 21749b, has the orbital period of 36 days to complete an orbit around the sun. It is the longest period among any of the TESS findings. It is predicted that most of the planets which will be discovered by TESS will have an orbital period lesser than 10 days because of the method used.

Its central star has about 80 percent of the mass of the sun and is about 53 light-years away from the earth as per lead author Diana Dragomir of MIT’s Kavli Institute for Astrophysics and Space Research. And the planet has about 23 times mass of Earth as well as its radius is about 2.7 times of earth’s radius. As per its density, one can easily image about its environment to be rocky but there are no such type of things here.

And the long period of the planet is not the only one in this system. The sibling planet, HD 21749c takes almost eight days for completing an orbit around the host star. It is much smaller in size, quite comparable to Earth, hence finding the exact mass and composition is quite a challenge but it is important for comparison to Earth.

Because of TESS, astronomers will be able to calculate the masses, measure atmospheric conditions of many exoplanets and scientists hope this will eventually set the path for finding planets which are potentially habitable.

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