Comet

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Posts

  • Octopuses from Space! (5/20/2018) - Did you hear the one about the octopuses from space? It sounds like the title of a cheesy sci-fi movie, doesn’t it? But it isn’t, this time, or at least, yet. Instead, it’s actually an oddball theory that’s been put forth in a recently published “scientific” article that’s getting quite a lot of buzz in … Continue reading Octopuses from Space!
  • RIP Rossetta! (10/1/2016) - The “Little Mission that Could” has come to an end, but what a mission it was to watch! Rosetta Concludes Mission with a Crash (Megan Gannon, Scientific American) Rosetta Mission Ends With Spacecraft’s Dive Into Comet (Kenneth Chang, New York Times) It was such a joy to watch each historic milestone the mission passed over … Continue reading RIP Rossetta!

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Solar System Exploration: Comets (NASA)

Dictionary

comet : a celestial body that appears as a fuzzy head usually surrounding a bright nucleus, that has a usually highly eccentric orbit, that consists primarily of ice and dust, and that often develops one or more long tails when near the sun — Webster

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Encyclopedia

Comet is a icy small Solar System body that, when passing close to the Sun, warms and begins to evolve gasses, a process called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena are due to the effects of solar radiation and the solar wind acting upon the nucleus of the comet. Comet nuclei range from a few hundred metres to tens of kilometres across and are composed of loose collections of ice, dust, and small rocky particles. The coma may be up to 15 times the Earth’s diameter, while the tail may stretch one astronomical unit. If sufficiently bright, a comet may be seen from the Earth without the aid of a telescope and may subtend an arc of 30° (60 Moons) across the sky. Comets have been observed and recorded since ancient times by many cultures.

Comets usually have highly eccentric elliptical orbits, and they have a wide range of orbital periods, ranging from several years to potentially several millions of years. Short-period comets originate in the Kuiper belt or its associated scattered disc, which lie beyond the orbit of Neptune. Long-period comets are thought to originate in the Oort cloud, a spherical cloud of icy bodies extending from outside the Kuiper belt to halfway to the nearest star. Long-period comets are set in motion towards the Sun from the Oort cloud by gravitational perturbations caused by passing stars and the galactic tide. Hyperbolic comets may pass once through the inner Solar System before being flung to interstellar space. The appearance of a comet is called an apparition.

Comets are distinguished from asteroids by the presence of an extended, gravitationally unbound atmosphere surrounding their central nucleus. This atmosphere has parts termed the coma (the central part immediately surrounding the nucleus) and the tail (a typically linear section consisting of dust or gas blown out from the coma by the Sun’s light pressure or outstreaming solar wind plasma). However, extinct comets that have passed close to the Sun many times have lost nearly all of their volatile ices and dust and may come to resemble small asteroids. Asteroids are thought to have a different origin from comets, having formed inside the orbit of Jupiter rather than in the outer Solar System. The discovery of main-belt comets and active centaur minor planets has blurred the distinction between asteroids and comets.

As of November 2014 there are 5,253 known comets, a number that is steadily increasing as they are discovered. However, this represents only a tiny fraction of the total potential comet population, as the reservoir of comet-like bodies in the outer Solar System (in the Oort cloud) is estimated to be one trillion. Roughly one comet per year is visible to the naked eye, though many of those are faint and unspectacular. Comets have been visited by unmanned probes such as the European Space Agency’s Rosetta, which became the first ever to land a robotic spacecraft on a comet, and NASA’s Deep Impact, which blasted a crater on Comet Tempel 1 to study its interior. — Wikipedia

Comets (Eric Weisstein’s World of Astronomy, Wolfram Research)
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Comets (Cosmos4Kids)
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Comets, Meteors & Asteroids (Ask an Astronomer, Cornell University)

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This Perfume Smells Like a Comet (Erin Blakemore, Smithsonian)

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Phys.org - latest science and technology news stories Phys.org internet news portal provides the latest news on science including: Physics, Nanotechnology, Life Sciences, Space Science, Earth Science, Environment, Health and Medicine.

  • Second alignment plane of solar system discovered
    on September 29, 2020 at 2:03 pm

    A study of comet motions indicates that the solar system has a second alignment plane. Analytical investigation of the orbits of long-period comets shows that the aphelia of the comets, the point where they are farthest from the Sun, tend to fall close to either the well-known ecliptic plane where the planets reside or a newly discovered "empty ecliptic." This has important implications for models of how comets originally formed in the solar system.

  • Video shows a meteoroid skipping off Earth's...
    on September 29, 2020 at 1:23 pm

    Here's something we don't see very often: an Earth-grazing meteoroid.

  • Rosetta spacecraft detects unexpected ultraviolet...
    on September 21, 2020 at 3:00 pm

    Data from Southwest Research Institute-led instruments aboard ESA's Rosetta spacecraft have helped reveal auroral emissions in the far ultraviolet around a comet for the first time.

  • Rock types on Ryugu provide clues to the...
    on September 21, 2020 at 3:00 pm

    The asteroid Ryugu may look like a solid piece of rock, but it's more accurate to liken it to an orbiting pile of rubble. Given the relative fragility of this collection of loosely bound boulders, researchers believe that Ryugu and similar asteroids probably don't last very long due to disruptions and collisions from other asteroids. Ryugu is estimated to have adopted its current form around 10 million to 20 million years ago, which sounds like a lot compared to a human lifespan, but makes it a […]

  • Supercooled water is a stable liquid, scientists...
    on September 17, 2020 at 6:00 pm

    Supercooled water is really two liquids in one. That's the conclusion reached by a research team at the U.S. Department of Energy's Pacific Northwest National Laboratory after making the first-ever measurements of liquid water at temperatures much colder than its typical freezing point.


  • COMET P/2007 R1 = 2019 K3 (Larson)
    by Gareth V. Williams on June 3, 2019 at 9:59 pm

    M.P.E.C. 2019-L42 Issued 2019 June 3, 21:50 UT The Minor Planet Electronic Circulars contain information on unusual minor planets and routine data on comets. They are published on behalf of Division F of the International Astronomical Union by the Minor Planet Center, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. Prepared using the Tamkin Foundation Computer Network […]

  • COMET P/2000 S4 (LINEAR-Spacewatch)
    by Gareth V. Williams on June 2, 2019 at 1:45 pm

    M.P.E.C. 2019-L11 Issued 2019 June 2, 13:34 UT The Minor Planet Electronic Circulars contain information on unusual minor planets and routine data on comets. They are published on behalf of Division F of the International Astronomical Union by the Minor Planet Center, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. Prepared using the Tamkin Foundation Computer Network […]

  • COMET C/2019 K1 (ATLAS)
    by Gareth V. Williams on May 25, 2019 at 2:26 pm

    M.P.E.C. 2019-K37 Issued 2019 May 25, 14:20 UT The Minor Planet Electronic Circulars contain information on unusual minor planets and routine data on comets. They are published on behalf of Division F of the International Astronomical Union by the Minor Planet Center, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. Prepared using the Tamkin Foundation Computer Network […]

  • COMET C/2019 JU6 (ATLAS)
    by Gareth V. Williams on May 24, 2019 at 2:52 pm

    M.P.E.C. 2019-K18 Issued 2019 May 24, 14:32 UT The Minor Planet Electronic Circulars contain information on unusual minor planets and routine data on comets. They are published on behalf of Division F of the International Astronomical Union by the Minor Planet Center, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. Prepared using the Tamkin Foundation Computer Network […]

  • COMET C/2019 J3 (ATLAS)
    by Gareth V. Williams on May 23, 2019 at 6:30 pm

    M.P.E.C. 2019-K14 Issued 2019 May 23, 18:24 UT The Minor Planet Electronic Circulars contain information on unusual minor planets and routine data on comets. They are published on behalf of Division F of the International Astronomical Union by the Minor Planet Center, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. Prepared using the Tamkin Foundation Computer Network […]