Comet 252P LINEAR Greens Northern Hemisphere Skies on March 29

Summary: Comet 252P LINEAR greens Northern Hemisphere skies for telescope observers at mid-northern latitudes Tuesday, March 29.

Comet 252P/LINEAR (upper right) poses near the Large Magellanic Cloud in southern skyscape: NASA History Office @NASA History, via Twitter March 20, 2016

On Tuesday, March 29, 2016, Comet 252P LINEAR greens Northern Hemisphere skies over mid-northern latitudes after first greening Southern Hemisphere skies with a brightness that could be seen without optical aids.

Photographs capture Comet 252P as a greenish mist. The greenness is visible via telescopes but not to unaided eyes. The green color is caused by fluorescing molecules of diatomic carbon (C2), emitted as carbon vapor by active comets. Solar ultraviolet light illuminates the diatomic carbon emissions.

Comet 252P/LINEAR, formally designated as Comet 252P, is sustaining a brightness that abruptly increased by 100 times above its expected value earlier in March. The increased brightness of Comet 252P, however, pales in comparison with other more luminous natural objects, such as the moon, night’s brightest natural object.

“Don’t expect Comet LINEAR to be obvious with a long tail,” J. Kelly Beatty, senior editor at Sky & Telescope, notes in the astronomy magazine’s online article Thursday, March 24, 2016. “Its light isn’t concentrated in a single point but instead is spread out in a soft round glow, larger than the Moon but many thousands of times dimmer.”

Best viewing in the Northern Hemisphere occurs close to the southern horizon at about 1 1/2 hours before sunrise. Sky & Telescope has designed a diagram that plots locations of Comet 252P, at eight hour intervals, along its northward path through Wednesday, March 30. The diagram represents southern horizon visibility of Comet 252P for mid-northern latitudes viewers.

Comet 252P’s path across Northern Hemisphere skies trails through easily recognizable landmarks. The moon, two distinctive constellations and two planets all share the sky with Comet 252P.

The constellations of Sagittarius and Scorpius appear as left and right flanks, respectively, of Comet 252P’s passage across Northern Hemisphere skies. Both constellations appear in the low southern sky before dawn.

The eight stars that form Sagittarius’s bow and arrow as well as the constellation’s teapot asterism (recognizable pattern of stars in Earth’s nighttime sky) hover distinctively above the southern horizon. An imaginary line extending from Sagittarius’s brightest star, Epsilon Sagittarii, at the base of the spout, links with Saturn, positioned to the right of Comet 252P.

Scorpius the Scorpion’s brightest star, Alpha Scorpii, shines for the unaided eye as a red supergiant, with a diameter 300 times that of Earth’s sun, in the constellatory scorpion’s heart. The star’s popular name, Antares, derives from Ancient Greek for “equal to Mars” and characterizes its Mars-like ruddy brightness.

To the right of Comet 252P, ruddy Antares forms an unmistakable triangle with reddish Mars, to the upper right, and pale yellow Saturn, to the upper left. Comet 252P roughly aligns horizontally with Saturn and Mars before dawn Tuesday. The comet’s more northerly climb in the sky by Thursday, March 31, places it on a diagonal alignment with Saturn and Antares.

The moon serves as competitor with and locator of Comet 252P for mid-northern latitude viewers during the last three days of March. The left side is illuminated for Northern Hemisphere viewers of the moon’s two phases at the end of March. Located to the right of Comet 252P, the moon runs glary interference with its illuminated quarter as the nearer side to the green comet.

On Tuesday, March 29, the moon is completing its waning gibbous phase. The moon’s sixth phase lights up 51 to 99 percent of the lunar disc. Tuesday’s visibility is at 80 percent.

On Wednesday, March 30, the moon hangs 3 degrees, or approximately two finger-widths of an outstretched arm, below Comet 252P’s lower right. Wednesday’s moon is phasing as the last, or third, quarter in the eight-phase lunar cycle. The last quarter illuminates 50 percent of the lunar disc. On Wednesday, visibility reaches 62 percent.

Comet 252P/LINEAR’s telltale name attests to its standing as the 252nd confirmed periodic (P) comet discovered by the Lincoln Near-Earth Asteroid Research (LINEAR) project. Funded by the National Aeronautics and Space Administration (NASA) and the U.S. Air Force, Massachusetts Institute of Technology’s Lincoln Laboratory site on the White Sands Missile Range (WSMR) in New Mexico discovered Comet 252P Friday, April 7, 2000.

Comet 252P is being shadowed by a smaller comet, originally thought to be an asteroid. Comet P/2016 BA14 was discovered Friday, Jan. 22, 2016, by the University of Hawaii’s PanSTARRS (Panoramic Survey Telescope and Rapid Response System) telescope at Haleakalā, Maui. Similarity in orbit with that of Comet 252P leads to the hypothesis of Comet P/2016 BA14 as a cometary fragment.

By April Fool’s Day, April 1, Comet 252P is fading from sight as its orbit takes it further away from Earth. Viewing in April’s early days requires a telescope.

Comet 252P/Linear's path across Earth's skies March 2016: The SETI Institute @SETIInstitute, via Twitter March 26, 2016

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

Comet 252P/LINEAR (upper right) poses near the Large Magellanic Cloud in southern skyscape: NASA History Office @NASA History, via Twitter March 20, 2016, @ https://twitter.com/NASAhistory/status/711613277802000384

Comet 252P/Linear's path across Earth's skies March 2016: The SETI Institute @SETIInstitute, via Twitter March 26, 2016, @ https://twitter.com/SETIInstitute/status/713727760380915713

For further information:

Agle, D.C.; Dwayne Brown; Laurie Cantillo. "A 'Tail' of Two Comets." NASA > Topics > Topics A-Z > Comets > Feature. March 18, 2016.
Available @ https://www.nasa.gov/feature/jpl/a-tail-of-two-comets

Astro Bob (Bob King). “See Comet 252P/LINEAR When It Flies By Earth.” AreaVoices. March 20, 2016.
Available @ http://astrobob.areavoices.com/2016/03/20/see-comet-252plinear-when-it-flies-by-earth/

The Editors of Sky Telescope. “Comet 252P/LINEAR Soars Into Predawn View This Week.” Sky and Telescope. March 24, 2016.
Available @ http://www.skyandtelescope.com/press-releases/how-to-spot-comet-252p-linear/

NASA History Office @NASAhistory. “Comet 252P/Linear is seen next to the Large Magellanic Cloud in this southern skyscape.” Twitter. March 20, 2016.
Available @ https://twitter.com/NASAhistory/status/711613277802000384

The SETI Institute @SETIInstitute. "See a Green Comet in the Night Sky: Where and When to Look." Twitter. March 26, 2016.
Available @ https://twitter.com/SETIInstitute/status/713727760380915713