Friday, January 6, 2023

3808 - SOLAR SYSTEM - seven planets

 

          3808  -  SOLAR  SYSTEM  -  seven planets.  With four inner, rocky planets, four outer, giant planets, and asteroids, moons, and Kuiper belt objects, our Solar System is a complex and wondrous place. Every one of the planets has some surprising and exciting facts.

           


            ---------  3808  -  SOLAR  SYSTEM  -  seven planets

            -   While only Earth contains liquid water rainfall and accumulated bodies of liquid water on its surface, other worlds have other forms of precipitation and surface liquids, as well as the potential for life.

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            -  The hottest planet resides in the clouds of Venus.   The “WISPR” data from the “Parker Solar Probe”, in monochrome, clearly matches the surface features seen by the infrared orbiter Magellan. Long wavelength light, such as infrared light, can peer through the clouds of Venus, all the way down to the surface. It’s only because the clouds themselves radiate in the infrared that phosphine can act as an absorber along the line-of-sight.

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            -  The atmospheric greenhouse effect on Venus yields consistently higher temperatures than Mercury.  The Soviet Union’s series of Venera landers are the only spacecraft to ever land and transmit data from the surface of Venus.

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            -   The longest-lived of all the landers exceeded the two-hour mark before the instruments overheated and contact was lost. To date, no spacecraft has survived for longer on the Venusian surface, where temperatures reach 900 degrees Fahrenheit .

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            -   It is the most metallic planet.  When it comes to the large, non-gaseous worlds of the Solar System, Mercury has by far the largest metallic core relative to its size. However, it’s Earth that’s the densest of all these worlds, with no other major body comparing in density, owing to the added factor of gravitational compression.

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            -        An early vapor state ensured Mercury is 75% metal, by mass.

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            -    Ceres was originally the 8th planet.  The dwarf planet Ceres is the largest world in the asteroid belt and the only one known to be in hydrostatic equilibrium. Discovered in 1801 by Giuseppe Piazzi, it was originally classified as a planet: the Solar System’s 8th planet.

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            -    By size, it’s clear that the gas giant worlds vastly outstrip any of the terrestrial planets. In terms of water, however, the giant planets, owing to their lunar systems, can possess more water than even planet Earth does.

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            -        Jupiter moons Ganymede, Callisto, and Europa individually possess more water than Earth.  Although Earth contains the most liquid water on its surface of any of the 8 planets, the most water in any form is found on Jupiter’s moon Ganymede. Next in order is Saturn’s Titan, Jupiter’s Callisto, and Jupiter’s Europa. Planet Earth has only the 5th most water, placing it ahead of Pluto, Dione, Triton, and Enceladus.

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            -   Neptune’s captured moon, Triton, surpasses Pluto and Eris in both mass and size.  When you rank all the moons, small planets, and dwarf planets in our Solar System, you find that Triton, the 7th largest moon, has more similarities to Pluto than it does to anything else in the Solar System.

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            -   Triton is larger and more massive than both Eris and Pluto, and originates from the Kuiper belt as well.

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            -    When we classify the known exoplanets by both mass and radius together, the data indicates that there are only three classes of planets:    terrestrial / rocky, with a volatile gas envelope but no self-compression, and with a volatile envelope and with self-compression. Anything above that is a star.

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            -   Planetary size peaks at a mass between that of Saturn and Jupiter, with heavier and heavier worlds getting smaller until true nuclear fusion ignites and a star is born. Saturn is just about the lowest density planet out there.  At 0.687 g/cm³, Saturn is the only planet less dense than water.

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            -    Saturn, as photographed here by Cassini during the 2008 equinox, isn’t just round, but is in hydrostatic equilibrium. With its low density and rapid rotation, Saturn is the most flattened planet in the Solar System, with an equatorial diameter that’s more than 10% larger than its polar diameter.

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            -   The images of Neptune, from October 7, 2017, with the Hubble Space Telescope, shows the presence of clouds, bands, and varying colors and temperatures across Neptune’s upper atmosphere. The rapid changes reveal Neptune’s wind speeds: the fastest in the Solar System.  With speeds over 1,100 mph, Neptune’s winds are unsurpassed.

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            -    Neptune, the 8th and outermost planet in our Solar System, as imaged by Voyager 2 during its 1989 flyby of the planet. Neptune is about four times the diameter of Earth, but a much deeper blue in color than our planet. The high-altitude clouds travel at remarkable speeds: up to 1900 km/hr, while the blue color comes from copious amounts of methane gas: reflective in visible light, but an outstanding absorber in infrared light.

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            -   Mars; 3% of all terrestrial meteorites originate there.  Winds at speeds up to 100 km/hr travel across the Martian surface. The craters caused by impacts in Mars’ past, all show different degrees of erosion. Some still have defined outer rims and clear features within them, while others are much smoother and featureless, evidence of old age and erosion.

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            -  On Earth, a small but significant percentage of our meteorites originate from Mars; it is unknown what fraction of Martian impacts originate from Earth-based rocks, and whether life stowed-away on any of them.

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            -        Infrared images of Uranus (1.6 and 2.2 microns) obtained on August 6, 2014, with adaptive optics on the 10-meter Keck telescope.  Uranus 97° axial tilt causes planet-wide changes every 21 years.  Although this is a modern, infrared view of our Solar System’s 7th planet, it was only discovered in 1781 through the serendipitous observations of William Herschel. Up until the advent of space telescopes and infrared astronomy, we had no idea that Uranus was ever anything other than featureless.

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            January 1, 2022        SOLAR  SYSTEM  -  seven planets                    3808                                                                                                                               

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            --------------------- ---  Friday, January 6, 2023  ---------------------------

             

             

             

             

                     

             

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