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-------------------- 2582 - EXOPLANET - that is like Earth?
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- The earlier Kepler mission discovered about 70 percent of the approximately 4,000 exoplanets known to science today, TESS is scheduled to scan 200,000 of the night's brightest stars for insight into their solar systems. It's expected to conduct this survey over the course of two years, focusing on small chunks of the night sky at a time.
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- The TESS satellite, which has four cameras that snap pictures once every 30 minutes, can study stars that are 30 to 100 times brighter. A Meteor Just Slammed Into Jupiter. And We Saw It. Ultimately, scientists hope the project will help us understand the composition of different solar systems, uncover mysteries about potentially habitable worlds, and unlock secrets about life elsewhere in the universe.
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- TESS has discovered its first Earth-sized planet in the habitable zone of a distant star. Its orbit sits in the sweet spot, where liquid water could exist on its surface. The exoplanet is a short distance from Earth, just 101.5 light-years away.
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- The star, an M dwarf star, is about 40 percent of the sun’s size and mass and nearly half as hot at the surface. The planet sits just inside the habitable zone, orbits around its star every 37 days, and is about 20 percent larger than Earth.
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- It doesn’t get as much energy from its own star as we do from Earth, receiving about 86 percent of the solar energy felt here on Earth. Researchers also suspect the planet is tidally locked, meaning only one side faces its star during orbit.
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- Using the information currently available about the exoplanet’s orbit, size and other solar system conditions, scientists are able to create models of likely environments. A tidally locked planet, for example, would have vastly different cloud systems than what you might find here on Earth.
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- In the 20 computer models that simulated this environment, several of them were considered habitable. One model, according to NASA, revealed a watery world with an atmosphere chiefly composed of carbon dioxide, when another described a scenario in which the exoplanet could be rocky and have landscapes shaped by strong winds that sweep from the exoplanet’s night side to its sunny side. A tidally locked planet would have vastly different cloud systems than what you might find here on Earth.
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- The exoplanet lives within a two-star system and is a type of exoplanet called a circumbinary planet. These types of planets are extremely difficult to spot.
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- The planet is almost seven times larger than earth, between the size of Neptune and Saturn. It also has a very strange orbit. The depth and duration of the orbit fluctuate and its transit in front of the two stars is odd, occurring every between 93 and 95 days.
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- The two stars, which haven't been named yet, orbit each other every 15 days. One of them is 10 percent more massive than the sun, and other is about one-third the mass of the sun. No other planets have been observed in the solar system.
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- TESS data also revealed evidence that the well-studied star Alpha Draconis and a nearby companion star regularly eclipse each other. It's one of the brightest examples of what's called an eclipsing binary system, where two stars are situated far from each other, but still interact gravitationally.
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- The super star is located about 270 light-years away in the constellation Draco. About 5,000 years ago, the star was considered to be a guiding light in the night sky, a North Star directing the ancient Egyptians and other ancient civilizations. Thanks to Earth's precession, or its cyclical 26,000-year wobble, that role is now played by Polaris.
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- TESS was designed and launched specifically to find Earth-sized planets orbiting nearby stars. Planets around nearby stars are easiest to follow up with larger telescopes in space and on Earth.
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- TESS, which launched in April 2018, hunts for planets using the "transit method," looking for telltale dips in stellar brightness caused by orbiting worlds crossing stars’ faces from the satellite’s perspective.
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- This same technique was used to great effect by NASA’s Kepler space telescope, which discovered about 70% of the roughly 4,000 known exoplanets.
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- TESS found three different planets circling the star. One of the other planets is a red dwarf about 40% as massive, 40% as wide and 50% as hot as Earth’s sun. The innermost planet is roughly Earth-sized and completes one orbit every 10 Earth days. The center planet is 2.6 times bigger than our planet, meaning it’s likely a gassy “mini-Neptune,” and orbits every 16 days.
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- The outermost known planet in the system, is the really intriguing one. It’s just 20% larger than Earth and completes one orbit every 37 days. The alien world receives 86% of the stellar energy that Earth gets from the sun, and is in the habitable zone.
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- All three planets may be tidally locked always showing it the same face just as Earth’s moon only ever shows us its near side. But tidal locking doesn’t necessarily preclude the possibility of life on an alien world.
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- In 11 months of data, astronomers saw no flares from the star, which improves the chances of it being habitable. Red dwarfs are generally much more active than the sun, and there’s considerable debate about how habitable their planets may be as a result. Frequent and powerful flaring, for example, can strip away a planet’s atmosphere.
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- TRAPPIST-1 is a dwarf star that lies just 40 light-years away from us and hosts seven Earth-size planets, three of which appear to be in the habitable zone. The system is a prime candidate for observation by NASA’s James Webb Space Telescope, which is scheduled to launch in 2021.
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- James Webb should be able to probe the TRAPPIST-1 worlds’ atmospheres for potential biosignature gases, such as methane and oxygen. The TESS discovery is a bit farther away, but it’s still close enough to be scrutinized in more detail in the future. And scientists do hope to learn more about it via observations by other instruments.
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- For example, they want to pin down the planet’s mass by measuring how much its gravity tugs the host star this way and that. Without knowing the mass, it’s unclear how dense the planet is, and thus, if it is a rocky world like Earth.
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- And in-depth observations of light that has streamed through the atmosphere on its way to Earth could tell us a great deal about conditions on the alien world’s surface, which remain a total mystery at the moment.
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- One of their computer simulations for the planet has an ocean-covered world with a carbon-dioxide-dominated atmosphere, whereas another simulation pictured the planet as a dry, cloudless world.
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- Someday, when we have real spectra to work with we can backtrack, match them to the closest simulated spectrum and then match that to a model.
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- Other exciting TESS news came out at AAS . For example, mission team members also announced TESS’ first circumbinary planet, a world with two suns in its sky, and revealed that the bright star Alpha Draconis and its dimmer companion mutually eclipse each other.
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- See other reviews;
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- 2280 - Life in the Universe. We are living proof. But is life out there on other planets? 7 pages. And, includes 4 other reviews abut exoplanets.
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- 2233 - More about the TESS space mission.
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- 2145 - Exoplanet in other solar systems.
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- 2119 - How math is used to discover exoplanets.
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- 2107 - Planets outside our own.
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- 2043 - Discovering planets around other stars. List 6 more Reviews about exoplanets.
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- January 11, 2020 2582
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--------------------- Saturday, January 11, 2020 --------------------
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