- 2872 - EXOPLANETS - discovering more planets. On October 20, 2020, scientists revealed a series of new discoveries made by NASA’s Transiting Exoplanet Survey Satellite (TESS). The telescope that has spotted a number of strange new worlds circling star systems.
--------------------------- 2872 - EXOPLANETS - discovering more planets.
- TESS has been busy uncovering the universe's oddities since launching in 2018. A follow-up to the Kepler mission, which 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.
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- It's expected to conduct this survey over the course of two years, focusing on small chunks of the night sky at a time. The satellite, which has four cameras that snap pictures once every 30 minutes, has improvements over Kepler, and can study stars that are 30 to 100 times brighter.
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- 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 where liquid water could exist on its surface. The exoplanet is called “TOI700d” (TOI stands for Tess Object of Interest) and it’s a short distance from Earth, 101.5 light-years away, which means it’s easier for other instruments to study the planet.
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- NASA’s other exoplanet hunter, Spitzer Space Telescope, confirmed the finding.
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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. The planet is likely tidally locked, meaning only one side faces its star during orbit.
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- It sits within the realm of “habitability“. 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.
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- In the 20 computer models that simulated TOI 700 d’s environment, several of them were habitable. One model 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.
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- 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. TOI 1338 b 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 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 this solar system.
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- Kepler discovered 12 circumbinary planets in a total of 10 systems, but most of the exoplanets found in those systems were larger; scientists believe these are easier to spot because they're more visible when they slide in front of their stars. It's likely TESS will spot a lot more of these strange systems
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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 is 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 Alpha Draconis 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.
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- Because of Earth's precession, or its cyclical 26,000-year wobble, that North Star is now Polaris.
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- TESS has discovered a roughly Earth-size planet in the habitable zone of its host star, the zone of orbital distances where liquid water could be stable on a world’s surface.
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- TESS, 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. This same strategy 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 TOI 700 (TOI is short for “Tess Object of Interest”). One of the other planets is a red dwarf about 40% as massive, 40% as wide and 50% as hot as Earth’s sun.
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- The innermost world, TOI 700 b, is roughly Earth-sized and completes one orbit every 10 Earth days. The center planet, TOI 700 c, is 2.6 times bigger than our planet, meaning it’s likely a gassy “mini-Neptune,” and orbits TOI 700 every 16 days.
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- TOI 700 d, 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, putting TOI 700 d in the habitable zone.
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- All three planets may be tidally locked to TOI 700, 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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- 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 can strip away a planet’s atmosphere.
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- “Spitzer” space telescope saw TOI 700 d transit exactly when astronomers expected it to. It’s a great addition to the legacy of a mission that helped confirm two of the TRAPPIST-1 planets and identify five more.
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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.
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- TOI 700 is farther away, but it’s still close enough to be scrutinized in more detail in the future. Scientists want to pin down TOI 700 d’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 TOI 700 d is and if it’s a rocky world like Earth.
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- And in-depth observations of light that has streamed through TOI 700 d’s 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 the simulations depicted TOI 700 d as an ocean-covered world with a carbon-dioxide-dominated atmosphere, whereas another one pictured the planet as a dry, cloudless world.
- When we have real spectra from TOI 700 d, we can backtrack, match them to the closest simulated spectrum and then match that to a model.
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- At the same time that astronomers stole back Pluto and regularized the Solar System, they delivered a bounty of new worlds to ponder. Thanks to arduous ground-based studies of nearby stars, and we now have a catalog of over 4,000 “new” planets orbiting hundreds of other stars.
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- In a single decade we have discovered that our solar system is not unique among the nearly 1 trillion stars in the Milky Way. Based on the Kepler survey, we have identified over 400 exoplanets that are Earth-sized, and of these, a handful are just the right distance from their star for liquid water to potentially exist on their surfaces!
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- Water is the staff of life. Without it you cannot even begin the chemistry of life. In November, 2013, scientists announced that one fifth of all Sun-like stars in the Milky Way have an Earth-sized planet in the “water zone.” With one fifth of the 1 trillion Milky Way stars being Sun-like, this works out to 40 billion Earth-like planets with liquid water potentially existing on their surfaces.
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- That’s a lot of opportunities for the chemistry of life to commence. On Earth this happened only a few hundred million years after the surface of Earth cooled enough for standing water to exist. Then bacteria emerged and dominated the planet for the next 4 billion years.
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- Astronomers have been able to study the atmospheres of over 50 of these new worlds. Water, carbon dioxide, methane, sodium, and water vapor have all been detected in these planetary atmospheres, along with actual clouds in the atmospheres of planets such as GJ 436b and Kepler-7b.
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- Would you believe that there are planets so hot that they are evaporating right before our eyes (HD 209458b and HD 189733b)? One planet, OGLE-TR-56b, has an atmosphere hot enough to have clouds of iron gas and raindrops of liquid iron raining down on the planet’s surface.
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- For some of the more massive, Jupiter-sized planets, it could even rain diamonds! The star called 1SWASP J140747.93-394542.6 is orbited by an object that is circled by a ring system much larger than Saturn’s rings. The mass of the object is not known; it could be a brown dwarf or a low-mass star instead of a planet.
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- Because the exoplanet catalog includes nearly 1,000 other planets that transit their stars, we can eventually study their atmospheres too. The goal is to find an Earth-sized, water-supporting “Goldilocks planet” with an atmosphere showing trace amounts of oxygen.
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- Earth’s atmosphere is 22-percent oxygen because Earth has a biosphere created over the eons by bacteria and plant life. Because oxygen reacts quickly with other compounds and rocks to oxidize them, only a planet with an extensive biosphere can continuously regenerate such a massive amount of atmospheric oxygen.
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- If astronomers do detect an exoplanet with a significant oxygen atmosphere, that can only mean an alien biosphere has created it.
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- It is only a matter of time, perhaps a few decades, before enough planetary atmospheres will have been surveyed to find one with such life signs. When that day dawns, we will be able to actually estimate how much life exists in the universe!
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- The catalog of exoplanets is expanding from hundreds to thousands, and hence to tens of thousands in the near future. We know that planetary systems are not rare in the Milky Way. We know that small planets like Earth handsomely outnumber the giant planets like Jupiter, and we know that planets do find themselves in the “water zone” from time to time.
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- Statistically, over 40 billion of these Earth-like worlds may exist in our Milky Way Galaxy.
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- So far we have discovered some of these distant worlds through glitches in the movement of their parent stars, or the brief diminution of their star light, but we now have 17 exoplanets that have been directly imaged as faint dots of light near their parent stars.
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- The closest of these orbits the star Fomalhaut, located 25 light years from Earth. Larger than Jupiter, and with a distance from Fomalhaut that is four times the distance between Neptune and our Sun, this planet takes over 1,500 years to complete one orbit.
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- Most exoplanets have so far been found using the so-called “transit method‘. In using the transit method we look for repetitive short dimmings of a star, which are caused by a planet passing in front of the star when viewed from Earth. This event is called a transit.
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- When you look at a randomly chosen star you typically don't know if it has a transiting planet or even a planet at all. In order to find new transits, we typically have to look at a star for a very long time and without pause, typically for weeks and sometimes for years.
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- For the transit method to work, we need to be in the orbital plane of the planet around its star, when seen from Earth. On average, this is only the case for about every hundredth exoplanet. And so we need to observe hundreds and thousands of stars continuously.
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- The transit method is therefore not more promising than other methods, but rather resembles the proverbial search for a needle in a haystack. Its success is based primarily on the continuous observation of a large number of stars by NASA's Kepler Space Telescope. Kepler has discovered thousands of exoplanets since 2009, in total more than half of all the exoplanets known today.
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- We have now refined the standard procedure for exoplanet transit searches by simply refraining from the data binning. Part of the increased computer workload can be absorbed by modern CPU power, but we also had to design the computer code from scratch to make it as efficient as possible. Now it even works on a standard laptop. So you can even find an exoplanet on a train journey with a laptop on your knees.
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- During the nine years of operation, Kepler recorded measurement data from about 150,000 stars. We did not just randomly choose one of the 150,000 stars from the Kepler mission; instead, we focused on the second part of the mission in which transiting planets had already been discovered around a total of 517 stars.
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- To check if our method is truly better than the previous methods, we simply revisited all the brightness measurements of these 517 stars and looked for additional planets that might have been missed so far.
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- We not only found all the previously known exoplanets, but we also discovered 18 new ones. That may not sound like much, 18 out of 517. More important is the fact that all of our newly discovered planets are about the same size as Earth and thus much smaller than most known exoplanets.
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- The signal of this presumed planet passes one of our statistical tests with a probability of 85 percent. That means the chances are 85:15, or almost six to one, that this signal is genuinely caused by a planet and not by a random statistical variation of the data or by an instrumental effect.
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- Astronomers want the signal to have a probability of 99 percent, a chance of 99 to one, before we would formally grant the planetary status to the candidate.
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----------------------------- Other reviews available upon request:
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- 2847 - CHEOPS - exploring other planets. September, 2020, eight months after the space telescope CHEOPS started its journey into space. CHEOPS is the first European Space Agency mission dedicated to characterizing known exoplanets. Exoplanets are planets outside the Solar System. They were first discovered in 1995.
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- 2770 - EXOPLANETS - are we alone? Some significant developments need to happen before we can answer the question with any confidence: We will get better at detecting Earth-like planets in the habitable zone and even be able to detect what's in their atmospheres (if they have one).
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- 2702 - EXOPLANETS - new discoveries? If astronomers do detect an exoplanet with a significant oxygen atmosphere, that can only mean an alien biosphere has created it. It is only a matter of time before enough planetary atmospheres will have been surveyed to find one with such life signs. When that day dawns, we will have written a new chapter in the search for life and be able to actually estimate how much life exists in the universe!
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- 2582 - EXOPLANET - that is like Earth? - January, 2020 astronomers revealed a series of new discoveries made by NASA’s Transiting Exoplanet Survey Satellite (TESS). The telescope has spotted a number of strange new exoplanets circling star systems. One is particularly Earthlike. It would be the greatest discoveries of mankind if life was discovered on another planet.
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- 2280 - We know there is life in the Universe. We are living proof of that. But is there life on exoplanets which are planets around other suns outside our own solar system? Exoplanets are common, we have found over 4,000 but as for life we are the only evidence so far.
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- 2233 - EXOPLANETS- The TESS Space Mission. The next generation exoplanet hunter is TESS, Transiting Exoplanet Survey Satellite, has already found eight confirmed planets in its first four months of observing and some are unlike anything astronomers have seen before.
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- 2223 - for more of the details about the TESS spac3 mission.
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- 2145 - for more details about the Kepler space telescope. There are nearly 1 trillion stars in our galaxy. 20% pf them are similar to our Sun. So, there could be 20,000,000,000 earth-like planets with liquid water on the surface.
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- 2119 - Math discovers exoplanets. Detecting sinusoidal wobbles in the light spectrum will detect earth-like terrestrial planets orbiting other stars.
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- 2107 - Planets outside our own. This Review lists 8 more reviews about exoplanets.
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- 2043 - Discovering planets around other stars. List 6 more Reviews about exoplanets.
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- October 22, 2020 2872
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--------------------- --- Monday, October 26, 2020 ---------------------------
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