NASA’s latest space telescope – the Transiting Exoplanet Survey Satellite, aka TESS – has just completed its primary mission, the space agency announced on August 11, 2020. Its initial research into the air took two years. During this time, TESS revolutionaryly helped our knowledge of exoplanets, worlds orbiting distant stars, to continue from where the Kepler space telescope, NASA’s first planetary fighter, stops.
TESS’s primary mission was officially completed on July 4, 2020. Following this, TESS will continue with its extended mission phase.
During the two-year survey, TESS represented about 75% of the sky, and so far has found 66 newly confirmed exoplanets and nearly 2,100 additional candidates awaiting confirmation. Patricia Boyd, project scientist for TESS at NASA’s Goddard Space Flight Center, said in a statement:
TESS produces a torrent of high quality observations that provide valuable data on a wide range of scientific topics.
In the first year, TESS observed 13 different sectors of the sky seen from the southern hemisphere, and then turned its attention to the northern sky in the second year. Each sector is a strip of 24 by 96 degrees of air, and TESS spends about a month researching each sector.
View of the TESS Southern Hemisphere sky. You can see the glowing band of our Milky Way galaxy (left), the Orion Nebula (above), and the Great Magellanic Cloud (center). The dark lines are gaps between the detectors in TESS’s camera system. Image via NASA / MIT / TESS / Ethan Kruse (USRA).
Patricia Boyd, project scientist for TESS at Goddard Space Flight Center. Image via NASA / Goddard Space Flight Center.
Now TESS is back to revisit the northern sky as it enters its extended mission. With that shift also comes some other changes and improvements, according to NASA.
TESS is now collecting data faster and more efficiently than it did during its primary mission, NASA said. The telescope’s cameras can now capture a full image every 10 minutes, three times faster than they did in the primary mission. TESS can also, by using a new fast mode, measure the brightness of thousands of stars every 20 seconds. Previously, the telescope would make similar measurements every two minutes. These enhancements are not only good for planetary hunting, they also help TESS better detect brightness changes caused by stellar oscillations and observe explosive torches of active stars in greater detail.
This extended mission phase will continue until September 2022. TESS will spend the next year observing the southern sky, and will then resume research into the northern sky for a period of 15 months. These studies will include observations along the ecliptic – the plane of the Earth’s orbit around the sun – which TESS has not yet depicted.
How do TESS find exoplanets?
Like many other telescopes, TESS uses the transit method to detect exoplanets. That is, their instruments are aimed at detecting bright declines in the brightness of stars as planets look past those stars as they do from Earth. Those temporary dips in brightness are very small, but TESS is able to see them, and determine if they are caused by a planet (in most cases, NASA said, they are).
Last January, NASA announced that TESS had discovered its first Earth-sized planet, TOI 700 d, in the habitable zone of its red dwarf star. The habitable zone is the region around a star, where temperatures on a rocky planet can allow liquid water to exist. The planet was later confirmed by NASA’s Spitzer Space Telescope. This planetary system is just over 100 light-years away in the constellation Dorado. According to Paul Hertz, director of the astrophysics division at NASA headquarters in Washington:
TESS was specifically designed and launched to find Earth-sized planets that have orbiting stars. Planets orbiting stars in the vicinity are easier to follow with larger telescopes in space and on Earth. Discovering TOI 700 d is an important scientific discovery for TESS. Confirming the size of the planet and the habitable solar status with Spitzer is another benefit for Spitzer, as the end of January comes at the end of scientific operations.
Artist concept of TOI 700 d, the first Earth-sized exoplanet that TESS found in the habitable zone of its star. This planetary system is 100 light-years away in the constellation Dorado. Image via Goddard Space Flight Center / Wikipedia.
TOI 700 d is the outermost of three known planets in the system and the only one in the habitable zone. It measures 20% larger than Earth, orbits its red dwarf star every 37 days and receives from its star 86% of the energy that the sun supplies to Earth.
It is expected that TESS will find many more Earth worlds, including those that are potentially habitable.
In June, scientists reported that TESS found a planet of Neptune, AU Mic b, orbiting a very young red dwarf star. Bryson Cale, a doctoral student at George Mason University, said:
AU Mic is a young, nearby M dwarf star. It is surrounded by a hot punch disk in which moving clumps of dust have followed, and now, thanks to TESS and Spitzer, it has a planet with a direct dimension. There is no other known system that controls all these important boxes.
The star is only 10 to 20 million years old, and the planet completes an orbit in just 8.5 days.
TESS also recently discovered its first circumbinary planet – one that revolves around two stars – called TOI 1338 b. The two stars rotate each other every 15 days. One is about 10% massier than our sun, while the other is cooler, dimmer and only 1/3 of the mass of the sun. The planet is about 6.9 times the size of Earth, between the size of Neptune and Saturn.
TESS is also good at multi-tasking, NASA said, and has studied more than just exoplanets. It has observed the eruption of a comet in our own solar system, as well as several exploding stars. It also found surprising merits in a well-known binary star system, solved a mystery about a class of pulsating stars, and explored a world experiencing star-modulated seasons.
TESS even caught a black hole in a distant galaxy in the act of tearing apart a sun-like star with its enormous gravity! Thomas Holoien, of Carnegie Observatories, is lead author of a paper describing the findings on September 27, 2019, in The Astrophysical Journal. Holoien said:
TESS data shows us just when this destructive event, named ASASSN-19bt, began to become clearer, something we could never do before. Because we quickly identified tidal disturbance with the ground-based All-Sky Automated Survey for Supernovae (ASAS-SN), we were able to track observations of longitude for the first few days. The early data will be incredibly useful for modeling the physics of these eruptions.
Last November, it was also announced that TESS would partner with Breakthrough Listening (part of Breakthrough Initiatives) in the search for foreign intelligence, aka SETI. In principle, TESS will identify objects of interest, such as potentially habitable exoplanets, for other telescopes to point out and search for radio signals or other signs of advanced technologies, called technosignatures.
In just the first few years of its mission, TESS has not only discovered thousands of new exoplanets, but has observed and witnessed a wide variety of incredible cosmic objects and phenomena. What else will it find in the coming years?
Illustration by artist from TESS. The space telescope on planetary hunting has now completed its primary mission and is now moving on to its extended mission. It has already found nearly 2,100 candidates for exoplanet and 66 confirmed new worlds. Image via NASA / Goddard Space Flight Center.
Bottom line: NASA’s planetary spacecraft TESS has completed its primary mission.
Via NASA
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