TESS Completes Its Primary Mission

Explore KELT-9 b, one of the hottest planets known. Observations from NASA's Transiting Exoplanet Survey Satellite (TESS) have revealed new details about the planet’s environment. The planet follows a close, polar orbit around a squashed star with different surface temperatures, factors that make peculiar seasons for KELT-9 b. Credit: NASA's Goddard Space Flight CenterMusic: "Migrating Species" from Universal Production MusicWatch this video on the NASA Goddard YouTube channel.Complete transcript available. This sequence illustrates the KELT-9 b system. The planet orbits close to its star on a 36-hour orbit, which makes its dayside temperatures as hot as some stars. The planet’s atmosphere is streaming away into space. Its host star has a distorted shape caused by its rapid spin, which also produces a surface with multiple temperatures. The star's polar regions are both brighter and hotter than its midsection. Credit: NASA's Goddard Space Flight Center/Chris Smith (USRA) Illustration showing one possible interpretation of KELT-9 b.Credit: NASA's Goddard Space Flight Center/Chris Smith (USRA) This sequence illustrates how the KELT-9 b system is oriented from Earth’s point of view. The planet’s transits begin near one of the star’s hot, bright poles and progress toward the cooler, dimmer equator. Credit: NASA's Goddard Space Flight Center/Chris Smith (USRA) This sequence illustrates a year as experienced by KELT-9 b. Over the course of a single orbit, the planet twice experiences cycles of heating and cooling caused by the star’s unusual pattern of surface temperatures. Between the star’s hot poles and cool equator, temperatures vary by about 1,500 F (800 C). This produces a “summer” when the planet faces a pole and a “winter” when it faces the cooler midsection. So every 36 hours, KELT-9 b experiences two summers and two winters. Credit: NASA's Goddard Space Flight Center/Chris Smith (USRA) GIF animation illustrating KELT-9 b's weird seasons.Credit: NASA's Goddard Space Flight Center Illustration of KELT-9 b eclipsing its star, its trail of escaping atmosphere gradually engulfing the viewer.Credit: NASA's Goddard Space Flight Center/Chris Smith (USRA) Animation illustrating the unusual appearance of KELT-9 b’s host star. The star’s 16-hour rotation is about 38 times faster than the Sun’s, which flattens the star along its spin axis. This also makes the poles hotter and brighter than the broadened midsection, a phenomenon called gravity darkening. Credit: NASA's Goddard Space Flight Center/Chris Smith (USRA) Measurements from NASA’s Transiting Exoplanet Survey Satellite (TESS) have enabled astronomers to greatly improve their understanding of the bizarre environment of KELT-9 b, one of the hottest planets known. Located about 670 light-years away in the constellation Cygnus, KELT-9 b was discovered in 2017 because the planet passed in front of its star for a part of each orbit, an event called a transit. Transits regularly dim the star’s light by a small but detectable amount. Between July 18 and Sept. 11, 2019, as part of the mission's yearlong campaign to observe the northern sky, TESS observed 27 transits of KELT-9 b, and these observations allowed the team to model the system’s unusual star and its impact on the planet. KELT-9 b is a gas giant world about 1.8 times bigger than Jupiter, with 2.9 times its mass. Tidal forces have locked its rotation so the same side always faces its star. The planet swings around its star in just 36 hours on an orbit that carries it almost directly above both of the star's poles. The close orbit means the planet's dayside temperature is around 7,800 degrees Fahrenheit (4,300 C), hotter than the surfaces of some stars. This intense heating also causes the planet’s atmosphere to stream away into space.Its odd host star is about twice the size of the Sun and averages about 56 percent hotter. But it spins 38 times faster than the Sun, completing a full rotation in just 16 hours. Its rapid spin distorts the star’s shape, flattening it at the poles and widening its midsection. This causes the star’s poles to heat up and brighten while its equatorial region cools and dims, a phenomenon called gravity darkening. The result is a temperature difference across the star’s surface of almost 1,500 F (800 C).With each orbit, KELT-9 b twice experiences the full range of stellar temperatures, producing what amounts to a peculiar seasonal sequence. The planet experiences “summer” when it swings over each hot pole and “winter” when it passes over the star’s cooler midsection. So KELT-9 b experiences two summers and two winters every year, with each season about nine hours. KELT-9 b begins its transit near the star's bright poles and then blocks less and less light as it travels over the star's dimmer equator. This asymmetry provides clues to the temperature and brightness changes across the star’s surface, and they permitted the team to reconstruct the star’s out-of-round shape, how it’s oriented in space, its range of surface temperatures, and other factors impacting the planet. Related pages

Take a tour through TOI 700, a planetary system 100 light-years away in the constellation Dorado. One of the system’s residents is TOI 700 d, the first Earth-size habitable-zone planet discovered by NASA’s Transiting Exoplanet Survey Satellite. Credit: NASA’s Goddard Space Flight Center.Music: "Family Tree" from Universal Production MusicWatch this video on the NASA Goddard YouTube channel.Complete transcript available. Researchers modeled 20 potential versions of TOI 700 d. This illustration is based on an ocean-covered simulation of the planet with a carbon-dioxide dominated atmosphere similar to that of early Mars. All the planets in the system are believed to be tidally locked to the star, which means they rotate once per orbit, so one side constantly faces the star. The stark temperature difference between the day and night sides create wind patterns and cloud formations very different from Earth’s in this version of TOI 700 d.Credit: NASA's Goddard Space Flight Center/Chris Smith (USRA) TESS transit data of TOI 700 b suggests the world is almost exactly Earth-size and is likely rocky, as shown in this animation. Credit: NASA's Goddard Space Flight Center/Chris Smith (USRA) TOI 700 c is around 2.6 times Earth's size and is likely gaseous.Credit: NASA's Goddard Space Flight Center/Chris Smith (USRA) The outermost planet, TOI 700 d, is the only one of the known worlds in this system in the habitable zone. It is about 1.2 times Earth’s size, and, as shown in this animation, is probably rocky.Credit: NASA's Goddard Space Flight Center/Chris Smith (USRA) The architecture of the TOI 700 system is shown in this animation that starts edge-on and then moves to a top-down view. The only planet currently known to be in the habitable zone is TOI 700 d. Credit: NASA's Goddard Space Flight Center/Chris Smith (USRA) Researchers created 20 different 3D climate models of TOI 700 d to determine if any version resulted in surface temperatures and pressures suitable for what scientists regard to be potentially habitable worlds. The simulations used a variety of surface types and atmospheric compositions. This animation shows the temperature and wind patterns for a cloudless, all-land planet with an atmosphere similar to Earth's. The winds move away from the night-side of the planet and converge on the point directly facing the star. The simulated data shows what detectable molecules are in the atmosphere. Credit: Engelmann-Suissa et al./NASA's Goddard Space Flight Center Another simulation of TOI 700 d depicts an ocean-covered world with a dense, carbon-dioxide-dominated atmosphere similar to what scientists suspect surrounded Mars when it was young. The result is an environment where the temperature is almost uniformly hot everywhere on the planet. Credit: Engelmann-Suissa et al./NASA's Goddard Space Flight Center NASA’s Transiting Exoplanet Survey Satellite (TESS) has discovered its first Earth-size planet in its star’s habitable zone, the range of distances where conditions may be just right to allow the presence of liquid water on the surface. Scientists confirmed the find, called TOI 700 d, using NASA’s Spitzer Space Telescope and have modeled the planet’s potential environments to help inform future observations.TOI 700 is a small, cool M dwarf star located just over 100 light-years away in the southern constellation Dorado. It’s roughly 40% of the Sun’s mass and size and 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.The innermost planet, called TOI 700 b, is almost exactly Earth-size, is probably rocky and completes an orbit every 10 days. The middle planet, TOI 700 c, is 2.6 times larger than Earth — between the sizes of Earth and Neptune — orbits every 16 days and is likely a gas-dominated world. TOI 700 d, the outermost known planet in the system and the only one in the habitable zone, measures 20% larger than Earth, orbits every 37 days and receives from its star 86% of the energy that the Sun provides to Earth. All of the planets are thought to be tidally locked to their star, which means they rotate once per orbit so that one side is constantly bathed in daylight.The Spitzer data increased scientists’ confidence that TOI 700 d is a real planet and sharpened their measurements of its orbital period by 56% and its size by 38%. It also ruled out other possible astrophysical causes of the transit signal, such as the presence of a smaller, dimmer companion star in the system. While the exact conditions on TOI 700 d are unknown, scientists used current information, like the planet’s size and the type of star it orbits, and modeled 20 potential environments for TOI 700 d to gauge if any version would result in surface temperatures and pressures suitable for habitability.One simulation included an ocean-covered TOI 700 d with a dense, carbon-dioxide-dominated atmosphere similar to what scientists suspect surrounded Mars when it was young. The model atmosphere contains a deep layer of clouds on the star-facing side. Another model depicts TOI 700 d as a cloudless, all-land version of modern Earth, where winds flow away from the night side of the planet and converge on the point directly facing the star. For More InformationSee [https://www.nasa.gov/feature/goddard/2020/nasa-planet-hunter-finds-its-1st-earth-size-habitable-zone-world](https://www.nasa.gov/feature/goddard/2020/nasa-planet-hunter-finds-its-1st-earth-size-habitable-zone-world) Related pages

NASA’s Transiting Exoplanet Survey Satellite found its first circumbinary planet, a world orbiting two stars 1,300 light-years away. Watch to learn more about this Saturn-size world called TOI 1338 b.Credit: NASA's Goddard Space Flight CenterMusic: "Albatross" from Universal Production Music.Complete transcript available.Watch this video on the NASA Goddard YouTube channel. The stars in the TOI 1338 system make an eclipsing binary — they circle each other in our plane of view. If you could hover near the planet TOI 1338 b, as shown in this animation, you would see an eclipse every 15 days. Credit: NASA's Goddard Space Flight Center/Chris Smith (USRA) TOI 1338 b is the only known planet in this binary star system. It’s around 6.9 times Earth’s size, or between the sizes of Neptune and Saturn. It is likely a gaseous world, as shown in this animation.Credit: NASA's Goddard Space Flight Center/Chris Smith (USRA) This animation shows TOI 1338 b as it passes, or transits, in front of its stars. TESS can only detect the transits from the larger star, the transits of the smaller star are too faint to detect. Simulated data shown at the bottom of the animation illustrates how the signal from the planet’s transit looks similar to the eclipse of the large star by its companion.Credit: NASA's Goddard Space Flight Center/Chris Smith (USRA) 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. This animation shows how the angle of the planet’s orbit changes over time.Credit: NASA's Goddard Space Flight Center/Chris Smith (USRA) Take a 360-degree tour around this illustration of TOI 1338 b. A 4K still image is also available.Credit: NASA's Goddard Space Flight Center/Chris Smith (USRA) Researchers working with data from NASA’s Transiting Exoplanet Survey Satellite (TESS) have discovered the mission’s first circumbinary planet, a world orbiting two stars. The planet, called TOI 1338 b, is around 6.9 times larger than Earth, or between the sizes of Neptune and Saturn. It lies in a system 1,300 light-years away in the constellation Pictor.The stars in the system make an eclipsing binary, which occurs when the stellar companions circle each other in our plane of view. One is about 10% more massive than our Sun, while the other is cooler, dimmer and only one-third the Sun’s mass. 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. Although the planet transits irregularly, its orbit is stable for at least the next 10 million years. The orbit’s angle to us, however, changes enough that the planet transit will cease after November 2023 and resume eight years later. Related pages

When a star strays too close to a black hole, intense tides break it apart into a stream of gas. The tail of the stream escapes the system, while the rest of it swings back around, surrounding the black hole with a disk of debris. This video includes images of a tidal disruption event called ASASSN-19bt taken by NASA’s Transiting Exoplanet Survey Satellite (TESS) and Swift missions, as well as an animation showing how the event unfolded. Credit: NASA’s Goddard Space Flight CenterMusic: "Games Show Sphere 03" from Universal Production MusicWatch this video on the NASA Goddard YouTube channel.Complete transcript available. The supermassive black hole that generated ASASSN-19bt weighs around 6 million times the Sun’s mass and sits at the center of a galaxy called 2MASX J07001137-6602251, located around 375 million light-years away in the constellation Volans. As shown in this animation, the destroyed star may have been similar in size to our Sun. When it approached the black hole, the star broke apart into a stream of gas. The tail of the stream escaped the system, while the rest of it swung back around, surrounding the black hole with a disk of debris.Credit: NASA’s Goddard Space Flight Center Same as above, without star inset.Credit: NASA's Goddard Space Flight Center ASASSN-19bt occurred in TESS’s continuous viewing zone, which is always in sight of the satellite’s fourth camera. Because of this observing strategy, TESS captured ASASSN-19bt from start to finish, providing a new look at a tidal disruption event. Credit: NASA’s Goddard Space Flight Center Observations by NASA’s Swift satellite provided the earliest ultraviolet measurements from a tidal disruption to date. This allowed scientists to determine that the temperature dropped by about 50%, from around 71,500 to 35,500 degrees Fahrenheit (40,000 to 20,000 degrees Celsius), over a few days.Credit: NASA’s Goddard Space Flight Center NASA’s planet-hunting Transiting Exoplanet Survey Satellite (TESS) watched a black hole tear apart a star from start to finish, a cataclysmic phenomenon called a tidal disruption event. The blast, named ASASSN-19bt, was found on Jan. 29 by the All-Sky Automated Survey for Supernovae (ASAS-SN), a worldwide network of 20 robotic telescopes. Shortly after the discovery, ASAS-SN requested follow-up observations by NASA’s Swift satellite, ESA’s (European Space Agency’s) XMM-Newton and ground-based 1-meter telescopes in the global Las Cumbres Observatory network.The disruption occurred in TESS’s continuous viewing zone, which is always in sight of one of the satellite’s four cameras. This allowed astronomers to view the explosion from beginning to end. For More InformationSee [https://www.nasa.gov/feature/goddard/2019/nasa-s-tess-mission-spots-its-1st-star-shredding-black-hole](https://www.nasa.gov/feature/goddard/2019/nasa-s-tess-mission-spots-its-1st-star-shredding-black-hole) Related pages

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. The outermost planet, GJ 357 d, is especially intriguing to scientists because it receives as much energy from its star as Mars does from the Sun. Credit: NASA's Goddard Space Flight CenterWatch this video on the NASA Goddard YouTube channel.Music: "Golden Temple" from Killer Tracks.Complete transcript available.See the bottom of the page for a version without on-screen text. Recorre el sistema GJ 357, ubicado a 31 años luz de distancia, en la constelación Hidra. Unos astrónomos que estaban confirmando un candidato a planeta identificado por el Satélite de Sondeo de Exoplanetas en Tránsito encontraron posteriormente otros dos mundos orbitando la estrella. El planeta más exterior, GJ 357 d, es especialmente intrigante para los científicos porque recibe tanta energía de su estrella como Marte recibe del Sol. Crédito: Centro de Vuelo Espacial Goddard de la NASAMire este video en el canal de YouTube de NASA en Español.Una transcripción completa está disponible. Illustration depicting one interpretation of planet GJ 357 b.Credit: NASA's Goddard Space Flight Center/Chris Smith Illustration depicting one interpretation of planet GJ 357 c.Credit: NASA's Goddard Space Flight Center/Chris Smith Illustration depicting one interpretation of planet GJ 357 d.Credit: NASA's Goddard Space Flight Center/Chris Smith Illustration depicting one interpretation of planet GJ 357 d.Credit: NASA's Goddard Space Flight Center/Chris Smith Illustration depicting a 360-degree rotation of GJ 357 b. A 4K still image is also available for download.Credit: NASA's Goddard Space Flight Center/Chris Smith Illustration depicting a 360-degree rotation of GJ 357 c. A 4K still image is also available for download.Credit: NASA's Goddard Space Flight Center/Chris Smith Illustration depicting a 360-degree rotation of GJ 357 d. A 4K still image is also available for download.Credit: NASA's Goddard Space Flight Center/Chris Smith This diagram shows the layout of the GJ 357 system. Planet d orbits within the star’s so-called habitable zone, the orbital region where liquid water can exist on a rocky planet’s surface. If it has a dense atmosphere, which will take future studies to determine, GJ 357 d could be warm enough to permit the presence of liquid water.Credit: NASA's Goddard Space Flight Center/Chris SmithVersions of this animation with Spanish labels are also available for download. Illustration depicting the transit method for detecting exoplanets. Versions of this animation with Spanish labels are also available for download.Credit: NASA's Goddard Space Flight Center/Chris Smith Illustration depicting the radial velocity method for detecting exoplanets.Credit: NASA's Goddard Space Flight Center/Chris Smith Textless version of full video. 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. The outermost planet, GJ 357 d, is especially intriguing to scientists because it receives as much energy from its star as Mars does from the Sun. Credit: NASA's Goddard Space Flight CenterMusic: "Golden Temple" from Killer Tracks. A planet discovered by NASA’s Transiting Exoplanet Survey Satellite (TESS) has pointed the way to additional worlds orbiting the same star, one of which is located in the star’s habitable zone. If made of rock, this planet may be around twice Earth’s size. The new worlds orbit a star named GJ 357, an M-type dwarf about one-third the Sun’s mass and size and about 40% cooler that our star. The system is located 31 light-years away in the constellation Hydra. In February, TESS cameras caught the star dimming slightly every 3.9 days, revealing the presence of a transiting exoplanet — a world beyond our solar system — that passes across the face of its star during every orbit and briefly dims the star’s light.The transits TESS observed belong to GJ 357 b, a planet about 22% larger than Earth. It orbits 11 times closer to its star than Mercury does our Sun.But while researchers were looking at ground-based data to confirm the existence of the hot Earth, they uncovered two additional worlds. The farthest-known planet, named GJ 357 d, is especially intriguing. The planet’s size and composition are unknown, but a rocky world with this mass would range from about one to two times Earth’s size. GJ 357 d is located within the outer edge of its star’s habitable zone, where it receives about the same amount of stellar energy from its star as Mars does from the Sun. If the planet has a dense atmosphere, which will take future studies to determine, it could trap enough heat to warm the planet and allow liquid water on its surface.GJ 357 c, the middle planet, has a mass at least 3.4 times Earth’s, orbits the star every 9.1 days at a distance a bit more than twice that of GJ 357 b. TESS did not observe transits from this planet, which suggests its orbit is slightly tilted — perhaps by less than 1 degree — relative to the hot Earth’s orbit, so it never passes across the star from our perspective. For More InformationSee [NASA: Confirmation of Toasty TESS Planet Leads to Surprising Find of Promising World](https://www.nasa.gov/feature/goddard/2019/confirmation-of-toasty-tess-planet-leads-to-surprising-find-of-promising-world/) Related pages

NASA’s Transiting Exoplanet Survey Satellite has confirmed the tiniest planet in its catalog so far — one of three discovered around a bright, nearby star called L 98-59. As shown in the illustrations in this video, all could occupy the “Venus zone,” the range of distances from the star where a Venus-like atmosphere is possible. The outermost planet also has the potential for a Neptune-like atmosphere. Credit: NASA’s Goddard Space Flight CenterMusic: "Autumn Rush" from Killer TracksComplete transcript available.Watch this video on the NASA Goddard YouTube channel. The three planets discovered in the L98-59 system by NASA’s Transiting Exoplanet Survey Satellite are compared to Mars and Earth in order of increasing size in this illustration.Credit: NASA’s Goddard Space Flight Center Square version of the above. Illustration depicting a 360-degree rotation of L 98-59b. A 4K still image is also available for download. Illustration depicting a 360-degree rotation of L 98-59c. A 4K still image is also available for download. Illustration depicting a 360-degree rotation of L 98-59d. A 4K still image is also available for download. L 98-59b, a planet discovered in the L98-59 system by NASA’s Transiting Exoplanet Survey Satellite, is compared to Mars and Earth in order of increasing size in this illustration. L 98-59c and L 98-59d, two planets discovered in the L98-59 system by NASA’s Transiting Exoplanet Survey Satellite, are compared to Earth in order of increasing size in this illustration. Illustration depicting the L 98-59 system. Illustration depicting how much radiation bombards each planet in the L 98-59 system, as multiples of the amount of radiation Earth receives from the Sun. Unlabeled version of the above. NASA’s Transiting Exoplanet Survey Satellite (TESS) has discovered a world between the sizes of Mars and Earth orbiting a bright, cool, nearby star. The planet, called L 98-59b, marks the smallest found by TESS yet. Two other worlds orbit the same star. While all three planets’ sizes are known, further study with other telescopes will be needed to determine if they have atmospheres and, if so, which gases are present. The L 98-59 worlds nearly double the number of small exoplanets — that is, planets beyond our solar system — that have the best potential for this kind of follow-up.L 98-59b is around 80% Earth’s size and about 10% smaller than the previous record holder discovered by TESS. Its host star, L 98-59, is an M dwarf about one-third the mass of the Sun and lies about 35 light-years away in the southern constellation Volans. While L 98-59b is a record for TESS, even smaller planets have been discovered in data collected by NASA’s Kepler satellite, including Kepler-37b, which is only 20% larger than the Moon. The two other worlds in the system, L 98-59c and L 98-59d, are respectively around 1.4 and 1.6 times Earth’s size. All three were discovered by TESS using transits, periodic dips in the star’s brightness caused when each planet passes in front of it. Related pages

This visualization shows TESS's first field image and information about three early exoplanet detections. The locations of Pi Mensae c, LHS 3844b, and HD21749b appear, as well as information about the systems and animations of what the planets might look like. This visualization shows TESS's first field image and locations of six supernovae detected by TESS. NASA’s Transiting Exoplanet Survey Satellite (TESS) has found three confirmed exoplanets, or worlds beyond our solar system, in its first three months of observations. The mission’s sensitive cameras also captured 100 short-lived changes — most of them likely stellar outbursts — in the same region of the sky. They include six supernova explosions whose brightening light was recorded by TESS even before the outbursts were discovered by ground-based telescopes. The new discoveries show that TESS is delivering on its goal of discovering planets around nearby bright stars. Using ground-based telescopes, astronomers are now conducting follow-up observations on more than 280 TESS exoplanet candidates. The first confirmed discovery is a world called Pi Mensae c about twice Earth’s size. Every six days, the new planet orbits the star Pi Mensae, located about 60 light-years away and visible to the unaided eye in the southern constellation Mensa. The bright star Pi Mensae is similar to the Sun in mass and size.Next is LHS 3844b, a rocky planet about 1.3 times Earth’s size located about 49 light-years away in the constellation Indus, making it among the closest transiting exoplanets known. The star is a cool M-type dwarf star about one-fifth the size of our Sun. Completing an orbit every 11 hours, the planet lies so close to its star that some of its rocky surface on the daytime side may form pools of molten lava.The third — and possibly fourth — planets orbit HD 21749, a K-type star about 80 percent the Sun’s mass and located 53 light-years away in the southern constellation Reticulum. The confirmed planet, HD 21749b, is about three times Earth’s size and 23 times its mass, orbits every 36 days, and has a surface temperature around 300 degrees Fahrenheit (150 degrees Celsius). It is the longest-period transiting planet within 100 light-years of the solar system, and it has the coolest surface temperature of a transiting exoplanet around a star brighter than 10th magnitude, or about 25 times fainter than the limit of unaided human vision. What’s even more exciting are hints the system holds a second candidate planet about the size of Earth that orbits the star every eight days. If confirmed, it could be the smallest TESS planet to date.In its primary two-year mission, TESS will observe nearly the whole sky, providing a rich catalog of worlds around nearby stars. Their proximity to Earth will enable detailed characterization of the planets through follow-up observations from space- and ground-based telescopes. But in its month-long stare into each sector, TESS records many additional phenomena, including comets, asteroids, flare stars, eclipsing binaries, white dwarf stars and supernovae, resulting in an astronomical treasure trove.In the first TESS sector alone, observed between July 25 and Aug. 22, 2018, the mission caught dozens of short-lived, or transient, events, including images of six supernovae in distant galaxies that were later seen by ground-based telescopes.These early observations hold the key to understanding a class of supernovae that serve as an important yardstick for cosmological studies. Type Ia supernovae form through two channels. One involves the merger of two orbiting white dwarfs, compact remnants of stars like the Sun. The other occurs in systems where a white dwarf draws gas from a normal star, gradually gaining mass until it becomes unstable and explodes. Astronomers don’t know which scenario is more common, but TESS could detect modifications to the early light of the explosion caused by the presence of stellar companion. Related pages