Sky and Telescope - May 2012 - (Page 40)
Sungrazer
ing the comet’s tail projecting up from the brightly lit dawn horizon. Until this point, Comet Lovejoy’s coma displayed a normal, condensed appearance. But this abruptly changed on December 20th when the comet’s head exhibited a long, bright tailward-pointing ray instead of a compact central condensation. This ray grew longer each day as the comet’s head became weaker and more diffuse. Comet expert Zdenek Sekanina at JPL proposed that Lovejoy’s nucleus completely disrupted about December 17.6 UT, and that the stream of resulting debris was moving rapidly outward into the tail, forming the ray-like feature. This debris ranged from boulder-sized pieces nearest the position of the comet’s former nucleus to micron-sized dust stretching well out into the tail. We may well have been witnessing the creation of innumerable future pygmy sungrazers. With the comet moving away from the Sun and the tailing growing longer each day, Comet Lovejoy looked like a searchlight beam projecting up from the horizon before it was washed out by increasing twilight. On the morning of December 22nd, observers were describing the comet’s dust and ion tails as each about 16° long and similar in brightness to the Large Magellanic Cloud. That same day the crew of the International Space Station watched the comet as it rose over Earth’s curving limb. While some observers thought that the fading of the comet’s head heralded a rapid demise of the tail, the performance of past sungrazers suggested that the show was just beginning and that Comet Lovejoy might unfurl a truly enormous tail in coming days. And it did just that. By Christmas morning the tail had grown to at least 28°! As the New Year opened, there were reports of the comet’s dust tail stretching across 40° of sky, but the head had faded so much that it could hardly be seen with the unaided eye. Like the Great Southern Comet of 1887, Comet Lovejoy had essentially become only a tail. The searchlight appearance of the tail was maintained
Dec. 16, 2011 Dec. 17, 2011
In the days following perihelion, the bright central condensation at the comet’s head evolved into a slender ray-like feature that is thought to have formed as debris from the disrupted nucleus spread outward into the tail. This view was obtained at 17:49 UT on December 24th with the Uppsala Schmidt Camera at Australia’s Siding Spring Observatory.
as it faded and grew ever more ghostly and transparent with the passing days. Although the end of the tail faded into the Milky Way in Crux and Centuarus, images showed that its length was an astounding 45° when it peaked in mid-January. This corresponded to a truly enormous 1¼ astronomical units! But because of its faintness, the tail was noticeably shorter to the unaided eye. By January 20th, the comet could only be seen visually from the darkest, pristine observing sites. Photographs in February captured only hints of the grand visitor as the comet disappeared from view, but Comet Lovejoy’s legacy will surely be remembered for a long time to come. ✦ Amateur astronomer John Bortle has a long history of observing and writing about comets, variable stars, and lunar eclipses from his home in Stormville, New York.
STEREO IMAGES COURTESY NASA / NAVAL RESEARCH LABORATORY
Dec. 18, 2011
Dec. 19, 2011
The changing appearances of Comet Lovejoy’s brilliant, sweeping dust tail and slender, straight gas tail are evident in this daily sequence obtained by the Heliospheric Imager on the STEREO A spacecraft between December 16th and 19th as the comet moved away from the Sun. Streaks emanating from bright objects are artifacts due to overexposure. The notably bright “stars” in the field are the planets Mercury (fainter of the pair) and Jupiter, which appeared relatively close together from the spacecraft’s vantage about 45° ahead of Earth on our orbit around the Sun.
40 May 2012 sky & telescope
ANU / UNIVERSITY OF ARIZONA / NASA / ROBERT H. MCNAUGHT
Table of Contents for the Digital Edition of Sky and Telescope - May 2012
Sky and Telescope - May 2012
Table of Contents
Spectrum
Letters
75, 50 & 25 Years Ago
News Notes
Saturn’s Raging Superstorm
Stars Above, Earth Below: Astronomy in National Parks
The Remarkable Case of Comet Lovejoy
In This Section
May’s Sky at a Glance
Binocular Highlight
Planetary Almanac
Northern Hemisphere’s Sky
Sun, Moon, and Planets
Celestial Calendar
Exploring the Solar System
Deep-Sky Wonders
Going Deep
S&T Test Report
New Product Showcase
Telescope Workshop
Planetary Imaging with Your DSLR Camera
Gallery
Focal Point
Sky and Telescope - May 2012
Sky and Telescope - May 2012 - (Page Intro)
Sky and Telescope - May 2012 - Sky and Telescope - May 2012 (Page Cover1)
Sky and Telescope - May 2012 - Sky and Telescope - May 2012 (Page Cover2)
Sky and Telescope - May 2012 - Sky and Telescope - May 2012 (Page 3)
Sky and Telescope - May 2012 - Table of Contents (Page 4)
Sky and Telescope - May 2012 - Table of Contents (Page 5)
Sky and Telescope - May 2012 - Spectrum (Page 6)
Sky and Telescope - May 2012 - Spectrum (Page 7)
Sky and Telescope - May 2012 - Letters (Page 8)
Sky and Telescope - May 2012 - Letters (Page 9)
Sky and Telescope - May 2012 - 75, 50 & 25 Years Ago (Page 10)
Sky and Telescope - May 2012 - 75, 50 & 25 Years Ago (Page 11)
Sky and Telescope - May 2012 - News Notes (Page 12)
Sky and Telescope - May 2012 - News Notes (Page 13)
Sky and Telescope - May 2012 - News Notes (Page 14)
Sky and Telescope - May 2012 - News Notes (Page 15)
Sky and Telescope - May 2012 - News Notes (Page 16)
Sky and Telescope - May 2012 - News Notes (Page 17)
Sky and Telescope - May 2012 - News Notes (Page 18)
Sky and Telescope - May 2012 - News Notes (Page 19)
Sky and Telescope - May 2012 - Saturn’s Raging Superstorm (Page 20)
Sky and Telescope - May 2012 - Saturn’s Raging Superstorm (Page 21)
Sky and Telescope - May 2012 - Saturn’s Raging Superstorm (Page 22)
Sky and Telescope - May 2012 - Saturn’s Raging Superstorm (Page 23)
Sky and Telescope - May 2012 - Saturn’s Raging Superstorm (Page 24)
Sky and Telescope - May 2012 - Saturn’s Raging Superstorm (Page 25)
Sky and Telescope - May 2012 - Stars Above, Earth Below: Astronomy in National Parks (Page 26)
Sky and Telescope - May 2012 - Stars Above, Earth Below: Astronomy in National Parks (Page 27)
Sky and Telescope - May 2012 - Stars Above, Earth Below: Astronomy in National Parks (Page 28)
Sky and Telescope - May 2012 - Stars Above, Earth Below: Astronomy in National Parks (Page 29)
Sky and Telescope - May 2012 - Stars Above, Earth Below: Astronomy in National Parks (Page 30)
Sky and Telescope - May 2012 - Stars Above, Earth Below: Astronomy in National Parks (Page 31)
Sky and Telescope - May 2012 - Stars Above, Earth Below: Astronomy in National Parks (Page 32)
Sky and Telescope - May 2012 - Stars Above, Earth Below: Astronomy in National Parks (Page 33)
Sky and Telescope - May 2012 - Stars Above, Earth Below: Astronomy in National Parks (Page 34)
Sky and Telescope - May 2012 - Stars Above, Earth Below: Astronomy in National Parks (Page 35)
Sky and Telescope - May 2012 - The Remarkable Case of Comet Lovejoy (Page 36)
Sky and Telescope - May 2012 - The Remarkable Case of Comet Lovejoy (Page 37)
Sky and Telescope - May 2012 - The Remarkable Case of Comet Lovejoy (Page 38)
Sky and Telescope - May 2012 - The Remarkable Case of Comet Lovejoy (Page 39)
Sky and Telescope - May 2012 - The Remarkable Case of Comet Lovejoy (Page 40)
Sky and Telescope - May 2012 - The Remarkable Case of Comet Lovejoy (Page 41)
Sky and Telescope - May 2012 - The Remarkable Case of Comet Lovejoy (Page 42)
Sky and Telescope - May 2012 - In This Section (Page 43)
Sky and Telescope - May 2012 - May’s Sky at a Glance (Page 44)
Sky and Telescope - May 2012 - Binocular Highlight (Page 45)
Sky and Telescope - May 2012 - Planetary Almanac (Page 46)
Sky and Telescope - May 2012 - Northern Hemisphere’s Sky (Page 47)
Sky and Telescope - May 2012 - Sun, Moon, and Planets (Page 48)
Sky and Telescope - May 2012 - Sun, Moon, and Planets (Page 49)
Sky and Telescope - May 2012 - Celestial Calendar (Page 50)
Sky and Telescope - May 2012 - Celestial Calendar (Page 51)
Sky and Telescope - May 2012 - Celestial Calendar (Page 52)
Sky and Telescope - May 2012 - Celestial Calendar (Page 53)
Sky and Telescope - May 2012 - Exploring the Solar System (Page 54)
Sky and Telescope - May 2012 - Exploring the Solar System (Page 55)
Sky and Telescope - May 2012 - Deep-Sky Wonders (Page 56)
Sky and Telescope - May 2012 - Deep-Sky Wonders (Page 57)
Sky and Telescope - May 2012 - Deep-Sky Wonders (Page 58)
Sky and Telescope - May 2012 - Deep-Sky Wonders (Page 59)
Sky and Telescope - May 2012 - Going Deep (Page 60)
Sky and Telescope - May 2012 - Going Deep (Page 61)
Sky and Telescope - May 2012 - Going Deep (Page 62)
Sky and Telescope - May 2012 - Going Deep (Page 63)
Sky and Telescope - May 2012 - S&T Test Report (Page 64)
Sky and Telescope - May 2012 - S&T Test Report (Page 65)
Sky and Telescope - May 2012 - S&T Test Report (Page 66)
Sky and Telescope - May 2012 - S&T Test Report (Page 67)
Sky and Telescope - May 2012 - New Product Showcase (Page 68)
Sky and Telescope - May 2012 - New Product Showcase (Page 69)
Sky and Telescope - May 2012 - Telescope Workshop (Page 70)
Sky and Telescope - May 2012 - Telescope Workshop (Page 71)
Sky and Telescope - May 2012 - Planetary Imaging with Your DSLR Camera (Page 72)
Sky and Telescope - May 2012 - Planetary Imaging with Your DSLR Camera (Page 73)
Sky and Telescope - May 2012 - Planetary Imaging with Your DSLR Camera (Page 74)
Sky and Telescope - May 2012 - Planetary Imaging with Your DSLR Camera (Page 75)
Sky and Telescope - May 2012 - Gallery (Page 76)
Sky and Telescope - May 2012 - Gallery (Page 77)
Sky and Telescope - May 2012 - Gallery (Page 78)
Sky and Telescope - May 2012 - Gallery (Page 79)
Sky and Telescope - May 2012 - Gallery (Page 80)
Sky and Telescope - May 2012 - Gallery (Page 81)
Sky and Telescope - May 2012 - Gallery (Page 82)
Sky and Telescope - May 2012 - Gallery (Page 83)
Sky and Telescope - May 2012 - Gallery (Page 84)
Sky and Telescope - May 2012 - Gallery (Page 85)
Sky and Telescope - May 2012 - Focal Point (Page 86)
Sky and Telescope - May 2012 - Focal Point (Page Cover3)
Sky and Telescope - May 2012 - Focal Point (Page Cover4)
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