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- International Space station crossing the Sun, dimming the star light so slightly
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----------------------- - 2233 - EXOPLANETS - The TESS Space Mission
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- TESS launched in April and began science observations in July. It was designed to be a follow-up to the prolific Kepler space telescope, which went dark in October after almost a decade of observing. Like Kepler, TESS searches for planets by watching for dips in starlight as planets cross, or transit, in front of their stars.
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- Unlike Kepler, which stared unblinkingly at a single patch of sky for years, TESS scans a new segment of sky every month. Over two years, TESS will cover the entire 360 degrees of sky visible from Earth’s orbit.
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- In the first four orbiting segments, TESS has already spotted eight confirmed planets and more than 320 unconfirmed candidates.
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- The third-found planet is only 52 light-years away. It has the lowest temperature known for a planet orbiting a bright, nearby star.
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- That makes it a great candidate for follow-up observations with future telescopes like the James Webb Space Telescope, scheduled to launch in 2021. Webb will use starlight filtering through the atmospheres of planets like this one to measure the atmospheres’ properties and search for signs of life.
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- This particular planet is still probably too hot and gassy to host life. Its orbit takes 36 Earth days. That is still the longest known orbital period for planets transiting bright stars within 100 light-years of the sun.
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- At that distance from the star it should heat the planet’s surface to about 150° Celsius, too hot for liquid water. And at 2.84 times Earth’s size and 23.2 times Earth’s mass, its density suggests it must have a thick atmosphere, unlike Earth’s life-friendly atmosphere.
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- Despite its heat, this planet is tepid compared with most of the scorched worlds whose atmospheres astronomers can probe right now. Smaller, cooler, more Earthlike worlds are few and far between, and may not orbit such bright stars.
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- Finding more longer-period planets would helps us explore the diversity of planets that are out there. Because TESS spends such a short stretch of time looking at each segment of the sky, astronomers expect most of its planet finds to have shorter years than an Earth month. Faster orbits means more frequent transits across the planet’s star to be detected as dimming the starlight.
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- Another planet find is slightly bigger than Earth, and orbits its star every 11 hours. It’s probably a lava world.
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- TESS’s first find is a planet that orbits its star every 6.27 days, and is about 2.14 times Earth’s size and 4.8 times Earth’s mass, giving it a density similar to pure water.
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- Previous observations showed that that star also has a planet 10 times the mass of Jupiter that orbits every 5.7 years. That planet revolves on a wildly eccentric orbit, swinging between the distance of Earth and the distance of Jupiter from its star.
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- Theories of how planets develop such strange orbits suggest that this super-Jupiter should have booted the planet out of the system. It is strange that the inner super-Earth actually survived that disruptive event.
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- The second planet found by TESS has a radius just 1.3 times Earth’s. But it swings around its planet every 11 hours, giving it a surface temperature of about 540° C “It’s likely a lava world.”
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- TESS has completed about one-twelfth of its first sky survey. TESS’ orbit is held stable by the moon’s gravity, so it doesn’t need to spend any fuel to stay put. The fuel on board, used to change the direction the telescope points, is enough to last for 300 years.
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- The orbit itself was designed to be extremely stable on timescales of decades to centuries.
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- Every new planet found seems very different from all the ones discovered previously. This could suggest the rarity of the existence of earth like similar planets and if some harbor conditions for multicelular or complex life to evolve , very likely it will have very different shapes from the ones we know because they would have to cope with totally different environments.
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- Apparently each star has a system of planets. If so, only in our galaxy with 200 billion stars, there are even a greater number of planets. But the odds of having another earthlike planet with the right conditions for complex life to emerge could be very minute.
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- Earth benefited from having a tilted rotation axis which provides seasonal climate patterns, also the right moon (size, distance) which prevents Earth to excessively and randomly wobble in its rotation axis and a planet like Jupiter which deflects from the inner solar system most of the incoming celestial bodies.
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- So far the only exoplanets we can see are massive planets quite close to their stars. The current limits of our detection ability do not indicate anything regarding the abundance of or lack of planets we cannot yet detect
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- There is much more to learn and the acceleration of our learning in space is hard to keep up with. Stay tuned!
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- (More reviews on this subject, exoplanets, are available if you are interested)
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- January 11, 2019
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-------------------------- Friday, January 11, 2019 --------------------------
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