By Michael Moyer

As it flares out of the distant Oort Cloud, the newly discovered comet C/2012 S1 (ISON) appears to be heading on a trajectory that could make for one of the most spectacular night-sky events in living memory. Why is this comet expected to be so unique? Two reasons:

Astronomers predict that the comet will pass just 1.16 million miles from the Sun as it swings around its perihelion, or closest approach. (This may seem like a lot, but remember—the Sun is big. If we were to scale the Sun down to the size of Earth, the comet would pass well within the orbits of dozens of satellites.) The close approach will melt enormous amounts of the comet’s ice, releasing dust and gas and forming what should be a magnificent tail.

After it loops around the Sun and forms this tail, the comet should then pass relatively close to Earth—not near enough to cause any worry, but close enough to put on a great show. Viewers in the Northern Hemisphere will get the best view as the comet blooms in the weeks approaching Christmas 2013. The comet could grow as bright as the full moon.

Of course, comets have a habit of not living up to expectations. This one could be sucked into the Sun during its close approach, or not grow as much of a tail as astronomers hope.

But that hasn’t dampened enthusiasm for what Astronomy Now is awkwardly calling “a once-in-a-civilisation’s-lifetime” event. The comet expert John E. Bortle is already comparing ISON with the Great Comet of 1680, which, according to contemporary accounts, caused the people of New York’s Manhattan Island to be “overcome with terror at a sight in the heavens such as has seldom greeted human eyes…. In the province of New York a day of fasting and humiliation was appointed, in order that the wrath of God might be assuaged.”

We can only hope for such a show.

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    In February, <a href="http://www.nasa.gov/mission_pages/stereo/main/index.html" target="_hplink">NASA's STEREO probes</a>, two observatories that were launched in 2006 to survey the sun, reached opposite ends of the sun and thus, were able to give scientists (and the rest of us!) a never-before-seen view of the far side of the star at the center of our solar system. The composite image above was captured on June 1, 2011, <a href="http://www.nasa.gov/mission_pages/stereo/news/farside-060111.html" target="_hplink">and according to NASA</a>, "is the first complete image of the solar far side, the half of the sun invisible from Earth." <a href="http://www.huffingtonpost.com/2011/02/07/nasa-stereo-sun-images-video_n_819510.html" target="_hplink">Click here for more</a> on the STEREO probes.

  • Messenger Reaches Mercury

    While it's not a "discovery," <em>per se</em>, it's a milestone that will no doubt lead to many new findings about the smallest and innermost planet in our solar system. In March, after a 6 1/2-year, 4.9 billion mile journey, <a href="http://www.huffingtonpost.com/2011/03/18/nasa-messenger-mercury_n_837503.html" target="_hplink">NASA's Messenger spacecraft reached Mercury's orbit</a>. Messenger, the first spacecraft to orbit Mercury, <a href="http://messenger.jhuapl.edu/mer_orbit.html" target="_hplink">orbits the planet</a> every 12 hours. In November, <a href="http://www.nasa.gov/mission_pages/messenger/media/MissionExtends.html" target="_hplink">NASA announced that the spacecraft's mission</a>, which was supposed to end on March 17, 2012, would be extended for an additional year.

  • Pluto's Tiny Moon

    In July, NASA said that its Hubble Space Telescope <a href="http://www.huffingtonpost.com/2011/07/20/new-pluto-moon-hubble-space-telescope_n_904578.html" target="_hplink">discovered an eight to 21-mile-wide moon</a> circling the dwarf planet.

  • Black Hole Eats A Star

    In March, <a href="http://www.huffingtonpost.com/2011/04/07/nasa-cosmic-blast_n_846333.html" target="_hplink">NASA's Swift satellite saw an unusually long explosion of gamma-rays</a>. After studying the X-rays, <a href="http://www.huffingtonpost.com/2011/08/25/black-hole-eats-star-video_n_937150.html" target="_hplink">scientists found that they came from</a> a black hole that had become reenergized when it devoured a star. <a href="http://www.nasa.gov/home/hqnews/2011/aug/HQ_11-271_Swift_Black_Hole.html" target="_hplink">From NASA</a>: <blockquote>Astronomers soon realized the source, known as Swift J1644+57, was the result of a truly extraordinary event -- the awakening of a distant galaxy's dormant black hole as it shredded and consumed a star. The galaxy is so far away, it took the light from the event approximately 3.9 billion years to reach Earth. </blockquote>

  • Huge Mountain Discovered On Asteroid

    <a href="http://www.nasa.gov/mission_pages/dawn/main/index.html" target="_hplink">NASA's Dawn</a>, an ion-propelled spacecraft that traveled 1.7 billion miles before reaching the asteroid Vesta in July, sent back images in October revealing that <a href="http://www.huffingtonpost.com/2011/10/05/vesta-mountain-dawn-nasa_n_996282.html" target="_hplink">Vesta is home to a mountain larger than any mountain</a> on Earth. In December, NASA released new images that Dawn took when it was orbiting only 130 miles above the asteroid, the closest it will get to Vesta. Dawn will continue to image Vesta until next summer, when it will make its way to Ceres, a bigger asteroid.

  • 'Star Wars'-Like Planet

    <a href="http://www.huffingtonpost.com/2011/09/15/kepler-16b-planet-two-suns_n_964799.html" target="_hplink">NASA's Kepler spacecraft found a planet</a> that orbits two suns, driving fans of the "Star Wars" franchise <a href="http://blog.moviefone.com/2011/09/16/astronomers-discover-real-life-tatooine-star-wars/" target="_hplink">to call it a real-life Tatooine</a>. Astronomers announced Kepler-16b, which is the first circumbinary planet -- meaning it orbits two stars -- in September. <a href="http://www.huffingtonpost.com/2011/09/15/kepler-16b-planet-two-suns_n_964799.html" target="_hplink">Click here for more</a> on Kepler-16b.

  • 'Habitable Zone' Planet Found

    Scientists in early December <a href="http://www.huffingtonpost.com/2011/12/05/kepler-22b-new-planet-discovered-habitable-zone_n_1129591.html" target="_hplink">announced the discovery of Kepler-22b</a>, a planet with a temperature of around 72 degrees that's in the so-called <a href="http://en.wikipedia.org/wiki/Habitable_zone" target="_hplink">"Goldilocks," or habitable zone</a>. While the temperature of the 600-light-year away planet could sustain water, it has a radius of 2.4 times that of Earth's, so <a href="http://www.huffingtonpost.com/huff-wires/20111206/us-sci-alien-planet/" target="_hplink">it's probably too big</a> to harbor life.

  • Biggest Black Holes Ever Discovered

    Astronomers announced in early December that <a href="http://www.huffingtonpost.com/2011/12/05/black-hole-scientists-discover-huge_n_1129727.html" target="_hplink">they had found the biggest black holes to date</a>. The massive black holes, which are 10 billion times the size of the sun, are located over 300 million light years away.

  • Europa's 'Great Lakes'

    Scientists had long-thought that a large body of water existed under the surface of Europa, Jupiter's moon, but it was thought to be tens of miles below an icy crust. In November, though, astronomers analyzing data from <a href="http://solarsystem.nasa.gov/galileo/" target="_hplink">NASA's Galileo spacecraft</a> found evidence that suggests blocks of ice interact with water below the surface, which could mean that nutrients and energy are moving between the underground ocean and icy shell. <a href="http://www.ig.utexas.edu/people/staff/britneys/" target="_hplink">Britney Schmidt</a>, the lead author of the study, <a href="http://www.nature.com/nature/journal/v479/n7374/full/nature10608.html" target="_hplink">which appeared in the journal Nature</a>, said that the interaction "could make Europa and its ocean more habitable for life." <a href="http://www.huffingtonpost.com/2011/11/17/europa-water-jupiter-moon-photo-video_n_1099463.html#s480278&title=Europa" target="_hplink">Click here to read more</a> about water on Europa.

  • 'Bubbles' At The Edge Of Solar System

    NASA's Voyager probes -- launched over 30 years ago -- found huge magnetic "bubbles" at the edge of the solar system. "The sun's magnetic field extends all the way to the edge of the solar system," astronomer Merav Opher of Boston University <a href="http://www.nasa.gov/mission_pages/voyager/heliosphere-surprise.html" target="_hplink">said in a NASA statement</a>. "Because the sun spins, its magnetic field becomes twisted and wrinkled, a bit like a ballerina's skirt. Far, far away from the sun, where the Voyagers are, the folds of the skirt bunch up." Voyager 1 and Voyager 2 were launched in 1977. Voyager 1 is currently 11 billion miles away and may exit our solar system within the next few years.

  • Gypsum On Mars

    In December, scientists announced that NASA's <a href="http://www.huffingtonpost.com/2011/12/08/mars-water-opportunity-rover-gypsum_n_1136483.html" target="_hplink">Mars Rover Opportunity may have found gypsum </a>that had been deposited by water. "This tells a slam-dunk story that water flowed through underground fractures in the rock," <a href="http://astro.cornell.edu/people/facstaff-detail.php?pers_id=112" target="_hplink">Steve Squyres</a>, a planetary scientist at Cornell University and the principal investigator for Opportunity <a href="http://www.nasa.gov/mission_pages/mer/news/mer20111207.html" target="_hplink">said in a NASA statement</a>. NASA's Curiosity Rover <a href="http://www.huffingtonpost.com/2011/11/26/nasa-mars-curiosity-launc_n_1113995.html" target="_hplink">is en route to the Red Planet</a> and will arrive in August 2012.

  • Earth-Size Planets Discovered

    Weeks after <a href="http://www.huffingtonpost.com/2011/12/05/kepler-22b-new-planet-discovered-habitable-zone_n_1129591.html" target="_hplink">the announcement of Kepler-22b</a>, scientists said that <a href="http://www.huffingtonpost.com/2011/12/20/new-planets-kepler-exoplanets_n_1161213.html" target="_hplink">they'd discovered Kepler-20e and Kepler-20f</a>, two planets that are about the size of Earth. While the planets are too close to their sun-like star to harbor life as we know it, the discovery proved that the Kepler spacecraft was capable of spotting planets that are Earth-size, and brings us one step closer to finding a true Earth twin. <a href="http://www.huffingtonpost.com/2011/12/20/new-planets-kepler-exoplanets_n_1161213.html" target="_hplink">Click here for more</a> on the new planets.

  • Charles Camarda: NASA Innovation