- 3045 - EXOPLANETS - and the search or life? Astronomers have been working hard adding the number of planets found to exist in other solar systems in our Milky Way Galaxy. By 2020, astronomers have discovered over 4,000 planets in other solar systems. 1995 was when the first planet outside our own solar system was found.
--------------- 3045 - EXOPLANETS - and the search or life?
- Astronomers have been working hard to reduce the number of planets in our Solar System. Thus a new word: “ I’ve been Pluto’ed” comes into our vocabulary. Pluto has been demoted to a dwarf planet and we are left with only eight planets in our Solar System, with Neptune being the furthest out.
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- At the same time astronomers have been working hard adding the number of planets found to exist in other solar systems in our Milky Way Galaxy. By 2020, astronomers have discovered over 4,000 planets in other solar systems. 1995 was when the first planet outside our own solar system was found.
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- We do not have sensitive enough instruments now to determine if there is life on any of these planets. And, we tend to find the giant gaseous planets like Jupiter because the smaller rocky planets like Earth are too small to see. But, new instruments are under development.
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- There are four ways planets are being discovered with our existing technology:
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----------------- (1) Radial velocity - A planet orbiting a star will tug on the star with its own gravity. This causes the star to wobble, just a little. If we observe the star’s light spectrum we see the blue shift when the wobble is towards us and the redshift when the wobble is away from us.
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- Knowing the amount of shift in the light spectrum astronomers can calculate the minimum mass of the planet causing the wobble. Velocity shifts of as little as 2 miles per hour can be detected.
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----------------- (2) Transit method - if a planet’s orbital plane is along our line of sight the planet will pass in front of the star on each orbit. When the planet passes in front of the star it blocks some of the light and the star’s apparent brightness dims for a brief moment.
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- This method knows the inclination of the orbit and, with the radial velocity method, can calculate the exact mass of the planet.
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---------------- (3) Microlensing - If a star and planet pass in front of a more distant star the gravity of the star and planet will bend the light of the more distant star and act as a lens, magnifying the star’s light causing it to brighten for a short time.
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- A smooth increase in brightness signifies the occulting star and a blip on this brightening light curve signifies an orbiting planet.
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----------------- (4) Direct-Imaging - This is the most difficult method because the image of the planet is reflected light and that is drowned out by the brighter light of the parent star. Methods have been developed to subtract out the star light and some planets have been discovered this way.
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- In 1991 the first exoplanet was discovered. In 1993 the first planet orbiting a binary star was discovered . In 1993 another planet was discovered in a star cluster. In 1995 the first planet was discovered orbiting a normal star, that we would call a solar system.
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- The closest planet is 10.5 lightyears away (Epsilon Eridan). The farthest planet discovered to date is 21,000 lightyears away. The fastest orbiting planet takes 1.212 days to orbit its star. The longest period planet takes 12.9 years to orbit its star. The planets range in size from 2% that of Earth to 132% that of Jupiter in these early discoveries.
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- Astronomers expected to find small rocky planets close to their stars and giant gaseous planets orbiting farther away from their stars. That fits our model of how we believe our solar system was formed. But, that is not what they are finding so far. The planet around 51 Pegasi, the first discovered, is half the size of Jupiter (149 times that of Earth) yet orbits closer to the star than Mercury does to our Sun.
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- The definition of a planet is a round object that has a mass less than 12 times that of Jupiter. It has a cold interior and is incapable of producing a nuclear reaction at its core.
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- If the round mass is 12-75 times Jupiter it is a Brown Dwarf that has a high core temperature capable of igniting deuterium, but not high enough to ignite hydrogen.
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- If the mass is greater than 75 Jupiter’s its interior gets hot enough to go nuclear, burn hydrogen, and become a star.
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- HD69830 has 3 planets, 12.1, 10.5, 18.4 the size of Earth , which is form 3.3% to 5.8% the size of Jupiter. These are Neptune size planets. The star is 5.95 magnitude brightness and just visible to the naked eye.
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- 55Cancri has 4 planets ranging from 4.5% to 392% the mass of Jupiter, or 14.3, 69, 249, and 1,250 times that of Earth. This system most resembles our own Solar System.
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- HD149026b is a planet 115% the mass of Saturn yet only 90% its diameter, meaning it is much denser than Saturn. The core of the planet is a heavy metal surrounded by liquid metallic hydrogen and an outer layer of hydrogen and helium gases.
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- For mass comparisons: Mercury is 6% Earths, Venus 82% Earths, Mars 11% Earths, and Jupiter 318% Earths.
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- We can not say that planets are all formed in accretion disks around a parent star. Numerous giant planets have been found traveling through the galaxy alone, unattached to any star. These are free floating planets. The ones found are about 5,000,000 years old, 1/1000 that of our solar system.
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- It is a mystery how these planets formed. The astronomers are using models that predict age and mass as a function of the object’s surface temperature and luminosity.
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- Improvements in Doppler technology have allowed the radial velocity method to measures velocity shifts as low as 2 miles per hour. The smallest planet found is near Gliese 876 just 15 lightyears away. Here two Jupiter sized planets orbit their star in 30 and 61 days. The third planet in this solar system was discovered to be only 7.5 Earth mass orbiting the star in 1.94 days. Its orbiting speed is only 15 miles per hour.
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- The objective of this planet search is , of course, is there life on another planet. The Earth is 4,600,000,000 years old and has been habitable for 3,700,000,000 years. Long enough for life to evolve.
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- All you really need for a habitable planet is for it to have a long period of liquid water. Of course, life also needs carbon, nitrogen and oxygen and energy, starlight, heat, or chemical energy. But, if it has liquid water it probably also has these things too.
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- Astronomers will be focusing on the habitable zones of each solar system for the small rocky planet or moon that would likely have life. How exciting is that? Other reviews about exoplanets:
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- 3043 - PLANETS - how many are out there? We are content in thinking we have discovered the planets in our solar system. We have eight planets circling he Sun. Nine if you count Pluto. Then more planetoids are being discovered orbiting farther from the Sun than Pluto.
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- 3044 - EXOPLANET - Pegasi and Doppler shift astronomy? The planet “51 Pegasi b” was discovered in 1995. It was the first planet discovered orbiting a normal star, like our Sun. When watching the star astronomers were able to detect a rhythmic wobble using the “Doppler Shift Technique.”
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- 2914 - EXOPLANETS - what it is like on frontline of discovery? We’re getting better and better at detecting exoplanets. Using the “transit method” of detection, the Kepler Space Telescope examined over 530,000 stars and discovered over 2,600 exoplanets in nine years. “TESS“, the telescope that is successor to Kepler, is still active, and has so far identified over 1800 candidate exoplanets, with 46 confirmed by 2020.
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- 2891 - EXOPLANETS - thousands have been found? Exoplanets are planets orbiting the other stars, outside our solar system, in other solar systems that are far, far away. They have been found by searching astronomers Most exoplanets have been found using the “transit method“.
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- 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
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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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- 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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February 12, 2021 EXOPLANETS - and the search or life? 691 3045
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