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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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.

  • Rosetta witnesses birth of baby bow shock around...
    on December 12, 2018 at 3:17 pm

    A new study reveals that, contrary to first impressions, Rosetta did detect signs of an infant bow shock at the comet it explored for two years – the first ever seen forming anywhere in the solar system. […]

  • Geminids meteor shower: An astrophysicist on what...
    on December 11, 2018 at 2:50 pm

    The Geminids meteor shower peaks on the mornings of December 13 and 14, 2018 – but if you look up any time there's a clear night sky up until December 17, you might just catch a glimpse of a Geminid meteor. […]

  • Learning from lunar lights
    on December 7, 2018 at 2:35 pm

    Every few hours observing the moon, ESA's 'NELIOTA' project discovers a brilliant flash of light across its surface – the result of an object hurtling through space and striking our unprotected rocky neighbour at vast speed. Based at the Kryoneri telescope of the National Observatory of Athens, this important project is now being extended to January 2021. […]

  • Unknown treasure trove of planets found hiding in...
    on December 6, 2018 at 7:33 pm

    "Super-Earths" and Neptune-sized planets could be forming around young stars in much greater numbers than scientists thought, new research by an international team of astronomers suggests. […]

  • An exoplanet loses its atmosphere in the form of...
    on December 6, 2018 at 7:00 pm

    A new study led by scientists from the Instituto de Astrofísica de Canarias (IAC) reveals that the giant exoplanet WASP-69b carries a comet-like tail made up of helium particles escaping from its gravitational field and propelled by the ultraviolet radiation of its star. The results of this work are published today in the journal Science. […]


  • COMET C/2017 M4 (ATLAS)
    by Gareth V. Williams on June 23, 2017 at 3:34 pm

    M.P.E.C. 2017-M45 Issued 2017 June 23, 15:30 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/2017 M3 (PANSTARRS)
    by Gareth V. Williams on June 23, 2017 at 3:23 pm

    M.P.E.C. 2017-M44 Issued 2017 June 23, 15:20 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 P/2004 T1 = 2017 M2 (LINEAR-NEAT)
    by Gareth V. Williams on June 22, 2017 at 10:39 am

    M.P.E.C. 2017-M40 Issued 2017 June 22, 10:35 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/2010 A2 (LINEAR)
    by Gareth V. Williams on June 21, 2017 at 10:46 am

    M.P.E.C. 2017-M38 Issued 2017 June 21, 10:43 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/2009 S2 = 2017 M1 (McNaught)
    by Gareth V. Williams on June 20, 2017 at 11:54 am

    M.P.E.C. 2017-M28 Issued 2017 June 20, 11:51 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 […]