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---------------------- 2280 - Life in the Universe?.
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- Exoplanets are common, we have found over 4,000 but as for life we are the only evidence so far. But, we do have the math correct and we do have this equation complete. This is the equation that estimates the chances of detecting life on another planet. What are the odds?
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- There are many planets known as hot super-Earths whizzing about so close to their stars that a year lasts less than a day. These planets are so hot, they probably have giant lava lakes, which are melted rock that will not be supporting life.
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- We have discovered planets that circle their stars in hours and others that take almost a million years to orbit their stars. And, thousands of orbits in between these extremes. We have discovered planets that revolve around two stars. We have discovered rogue planets that don’t orbit any star but just wander about in space.
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- The very first exoplanet found, 51 Pegasi b, was discovered in 1955. It is a giant planet orbiting so close to its star it swings around it in just four days.
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- Today we have confirmed over 4,000 exoplanets. The majority were discovered by the Kepler space telescope, launched in 2009. Kepler’s mission was to see how many planets it could find orbiting some 150,000 stars in one tiny patch of sky.
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- - (See Review 2145 for more details about the Kepler space telescope)
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- Kepler’s patch of sky was about as much as you can cover with your hand with your arm outstretched. Kepler simply staired at this patch looking at stars hoping to see planets passing in front of their light.
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- Are places where life might evolve common in the universe or vanishingly rare, leaving us effectively without hope of ever knowing whether another living world exists?
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- Kepler’s discoveries showed us that there are more planets than there are stars, and at least a quarter are Earth-size planets in their star’s so-called habitable zone, where conditions are neither too hot nor too cold for life. They are called the “Goldielocks Zones”
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- With a minimum of 100 billion stars in the Milky Way, that means there are at least 25 billion places where life could conceivably take hold in our galaxy alone, and, our galaxy is one among trillions of galaxies in the Observable Universe.
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- Kepler’s discoveries have changed the way we approach one of the great mysteries of existence. The question is no longer, is there life beyond Earth? It’s a pretty sure bet there is. The question now is, how do we find it?
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- - The Kepler telescope, after detecting thousands of exoplanets, was retired last year when it ran out of fuel, but new telescopes promise dramatic improvements in the hunt.
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- The revelation that the galaxy is teeming with planets has reenergized the search for life. TESS is a satellite designed to find an Earth-like planet orbiting a sunlike star. The Transiting Exoplanet Survey Satellite (TESS) space telescope was launched last year , 2018. Like Kepler, TESS looks for a slight dimming in the luminosity of a star when a planet passes, or transits, in front of it.
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- {See Review 2223 for more of the details about the TESS spac3 mission.}
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- TESS is scanning nearly the whole sky, with the goal of identifying about 50 exoplanets with rocky surfaces like Earth’s that could be investigated by more powerful telescopes coming on line, beginning with the James Webb Space Telescope to be launched in 2021.
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- The spectral signatures of the elements are like colored bar codes. Every chemical compound absorbs a unique set of wavelengths of light. (We see leaves as green, for instance, because chlorophyll is a light-hungry molecule that absorbs red and blue, so the only light reflected is green.)
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- Chemical compounds in a transiting planet’s upper atmosphere might leave their spectral fingerprints in starlight passing through. Theoretically, if there are gases in a planet’s atmosphere from living creatures, we could see the evidence in the light that reaches us.
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- There’s an outside chance a rocky planet orbits a star close enough for the Webb telescope to capture sufficient light to investigate it for signs of life.
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- In addition to a planet’s size and distance from its star, they might be able to study its terrain and check for cloud cover. Here are some other planet hunters:
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- ELT, Extremely Large Telescope Captures visible and near- infrared spectrum images
16 times as sharp as those of the Hubble Space Telescope.
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- SUBARU telescope Coronagraphic removes distant starlight reaching the Subaru telescope, allowing astronomers to directly image exoplanets.
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- Ground-based scopes can hold heavy, powerful optics that are comparatively easy to maintain. But Earth’s atmosphere filters and distorts starlight, limiting what these telescopes can see in outer space.
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- STARSHADE is a flower-shaped light shield more than a hundred feet in diameter, the Starshade will work in tandem with a telescope. It will block a host star’s light, allowing astronomers a direct view of its exoplanets.
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- Deployed in space a shade of a space telescope ,more than 100 feet in diameter, would block the light from a star. The telescope would capture an image of a planet when it’s between Star shade’s petals, seeking evidence that life may exist on the planet.
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- TESS, Transiting Exoplanet Survey Satellite Detects small planets orbiting bright stars, which could be good candidates for more in-depth habitability studies.
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- James Webb Space Telescope. Studies distant stars and exoplanets using four instruments, including infrared cameras and spectrographs.
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- The SUBARU observatory, along with 12 others, sits atop the summit of Mauna Kea, on Hawaii’s Big Island. The Subaru’s 8.2-meter (27 feet) reflector is among the largest single-piece mirrors in the world. (Subaru is the Japanese name for the Pleiades star cluster.)
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- At 13,796 feet above sea level, Mauna Kea affords one of the highest, clearest views of the universe. An exoplanet orbits in front of a star much like the sun. One way to find out if a planet might contain life is to look for telltale signs called biosignatures. As starlight reflects off a planet or passes through its atmosphere, the gases absorb specific wavelengths. The spectrum observed through a telescope could show whether gases associated with life, such as oxygen, carbon dioxide, or methane, are present.
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- On Earth, chlorophyll in photosynthesizing plants absorbs red and blue light, so vegetation appears green. On other living worlds, though, photosynthesis might use a different pigment. The lavender hue of this hypothetical exoplanet, viewed from its icy moon, derives from a pigment called retinal, which is also able to convert light to metabolic energy and may have preceded chlorophyll in Earth’s early history.
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- A sharp contrast in a spectrum between the absorption of red light and reflection of near-infrared light, known as the vegetation red edge, indicates the presence of plants.
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- Until now, the search for extraterrestrial intelligence has focused on detecting an incoming radio signal. With increasing computational power and more sensitive telescopes, researchers are expanding the search to optical and infrared emissions, targeting the technology of advanced civilizations. These could include laser pulses, polluting gases, or mega structures built around a nearby star to harness its energy.
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- The light from the star swamps out the shadow from the transit planet. Trying to separate the light of a rocky, Earth-size planet from that of its star is like squinting hard enough to make out a fruit fly hovering inches in front of a floodlight. It doesn’t seem possible?
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- Earth supports life in part because its terrain is rocky, it doesn’t receive too much solar radiation, and its distance from the sun allows water to be in a liquid state. So far, 47 exoplanets have been found that fit this profile. But that number will grow as new telescopes search for planets in broader swaths of the galaxy than ever before.
- “Kepler-1638 b” is an exoplanet that is 2,867 light-years from Earth It is a planets in the habitable zone because it is likely to have liquid surface water
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- Scientists use our solar system to help determine the habitable zone around a star. To support life, planets must receive no more energy from their stars than Venus did when it had liquid surface water and no less energy than Mars did when it had water.
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- The TESS space telescope is now fully operational. It is able to survey 85 percent of the night sky, an area 400 times as large as that covered by its predecessor, Kepler.
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- Ground telescopes like the Subaru are much more powerful light-gatherers than space telescopes like the Hubble, chiefly because nobody has yet figured out how to squeeze a 27-foot mirror into a rocket and blast it into space.
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- But, ground telescopes have a serious drawback: They sit under miles of our atmosphere. Fluctuations in the air’s temperature cause light to bend erratically like a twinkling star, or the wavy air above an asphalt road in the summertime.
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- The first task is to iron out those wrinkles in the image. This is accomplished by directing the light from a star onto a shape-shifting mirror, smaller than a quarter, activated by 2,000 tiny motors.
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- Using information from a camera, the motors deform the mirror 3,000 times a second to precisely counter the atmospheric aberrations. The result a beam of starlight can be viewed that is as close as possible to what it was before our atmosphere messed it up.
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- Then send this light on to a spectrometer A spectrometer separates the light into its wavelengths, and the light spectrum becomes a biological signature to identify the various chemical elements.
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- On Earth, plants and certain bacteria produce oxygen as a by-product of photosynthesis. Oxygen is a molecule that reacts and bonds with just about everything on a planet’s surface. So if we can find evidence of it accumulating in an atmosphere something is creating it. Plants.
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- Most convincing of all would be to find oxygen along with methane, because those two gases from living organisms destroy each other. Finding them both would mean there must be constant replenishment.
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- Life could take forms other than photosynthesizing plants, and indeed even here on Earth, anaerobic life existed for billions of years before oxygen began to accumulate in the atmosphere.
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- As long as some basic requirements are met, energy, nutrients, and a liquid medium, life could evolve in ways that would produce any number of different gases. The key is finding gases in excess of what should be there.
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- There are other sorts of biological signatures we can look for too. The chlorophyll in vegetation reflects near-infrared light invisible to human eyes but easily observable with infrared telescopes. Find it in a planet’s biological signature, and you may well have found an extraterrestrial forest.
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- But the vegetation on other planets might absorb different wavelengths of light, there could be planets with Black Forests that are truly black, or planets where roses are red, and so is everything else.
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- And why stick to plants. The spectral characteristics of 137 microorganisms, including ones in extreme Earth environments that, on another planet, might be the norm. It’s no wonder the next generation of telescopes is so eagerly anticipated.
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- The first and most powerful of the next-generastion ground telescopes, Extremely Large Telescope (ELT) in the Atacama Desert of Chile, is scheduled to start operation in 2024. The light-gathering capacity of its 39-meter (128 feet) mirror will exceed all existing Subaru-size telescopes combined.
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- Outfitted with the ELT will be fully capable of imaging rocky planets in the habitable zone of red dwarf stars, the most common stars in the galaxy. They are smaller and dimmer than our sun, a yellow dwarf, so their habitable zones are closer to the star. The nearer a planet is to its star, the more light it reflects.
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- Red dwarfs are highly energetic, frequently hurtling flares out into space. There might be ways an atmosphere could evolve that would protect nascent life from being fried by these solar tantrums. But planets around red dwarfs are also likely to be tidally locked This means they are always presenting one side to the star, in the same way our moon shows only one face to the Earth. This would render half the planet too hot for life, the other half too cold. The midline, though, might be temperate enough for life.
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- As it happens, there’s a rocky planet, called Proxima Centauri b, orbiting in the habitable zone of Proxima Centauri, a red dwarf that’s the nearest star to our own, about 4.2 light-years, or 25 trillion miles, away.
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- Even those giant ground telescopes won’t be able to separate the light of a planet from that of a star 10 billion times brighter.
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- “Starshot” is an ambitious plan in development to send tiny probes on a 20-year journey to the exoplanet Proxima Centauri b. But even a featherweight spacecraft needs fuel. The farther it goes, the more it needs. The proposed solution? Launch it from an orbiting satellite and propel it with Earth-based lasers.
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- The mother ship Situated in low Earth orbit, a satellite houses thousands of probes. When the individual probes are released, their sails automatically unfurl. Phased lasers on Earth, nearly a billion laser beams are directed at a probe to create a pulse with the power of 100 gigawatts, lasting several minutes.
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- Those few minutes are just enough to accelerate the probe to one-fifth the speed of light and into the vacuum of space, where it is able to glide. The probe reaches Proxima b after a voyage of more than 20 years. During its high-speed flyby, it takes images and records a range of data.
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- The probe beams the information back using a laser embedded in its chip. Each transmission takes about four years to reach the Earth. Each probe has a quarter-inch chip weighing five grams or less that performs the roles of a camera, computers, and navigational equipment. Images and data are beamed to Earth via laser.
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- Starshade consists of 28 panels arranged around a center hub like a giant sunflower, more than 100 feet across. The petals are precisely shaped and rippled to deflect the light from a star, leaving a super-dark shadow trailing behind. If a telescope is positioned far back in that tunnel of darkness, it will be able to capture the glimmer from an Earth-like planet visible just beyond the Starshade’s edge.
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- Starshade’s earliest likely partner is called the Wide Field Infrared Survey Telescope scheduled to be finished by the mid-2020s. The two spacecraft will work together. Starshade will move into position to block the light from a star so it can detect any planets around it and potentially sample their spectra for signs of life.
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- SETI Institute has one of the units in the Allen Telescope Array, the only facility on Earth built specifically to look for signs of extraterrestrial intelligence. The telescope array, located in the Cascade mountains in Northern California, was supposed to have 350 radio telescopes, 42 have been built to date.
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- The hope is to find an anomalous signal: one emanating neither from a natural source in the cosmos, nor from earthly interference, such as a satellite or airplane. Radio emissions captured by the ATA’s dishes are focused onto the feed, which then amplifies the signals, digitizes them, and sends them via a fiber optic cable to the facilities’ signal-processing room.
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- The first Voyager spacecraft, launched in 1977, took 35 years to enter interstellar space. Traveling at that speed, Voyager would need some 75,000 years to reach Alpha Centauri. In the current vision for Starshot, a fleet of pebble-size spaceships hurtling through space at one-fifth the speed of light could reach Alpha Centauri in a mere 20 years.
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- These tiny Niñas, Pintas, and Santa Marías would be propelled by a ground-based laser array, more powerful than a million suns.
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- The MeerKAT telescope in South Africa, an array of 64 radio dishes, each more than twice the size of the ATA’s. By piggybacking on observations conducted by other scientists. It will conduct a 24/7 stakeout of a million stars, dwarfing previous SETI radio searches.
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- Powerful as it is, MeerKAT is just a precursor to radio astronomy’s dream machine: the Square Kilometre Array, which sometime in the next decade will link hundreds of dishes in South Africa with thousands of antennas in Australia, creating the collecting area of a single dish more than a square kilometer, or about 247 acres.
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- Most important, empowered and inspired by the accelerating rate of technological development in our own civilization, we are coming to see the target of the quest in a different light. For 60 years we’ve been waiting for ET to phone Earth.
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- What we should be looking for is not a message from ET, but signs of ET just going about the business of being ET, alien and intelligent in ways that we may not yet comprehend but may still be able to perceive, by looking for evidence of technology.
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- The most obvious evidence of technology would be ones we’ve produced, or can imagine producing, ourselves. If another civilization were using similar laser propulsion to sail through space, its Starshot-like beacons would be visible to the edge of the universe.
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- Other reviews available:
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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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- February 22, 2019
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-------------------------- Saturday, February 23, 2019 --------------------------
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