See Comet 252P/LINEAR When It Flies By Earth

Big green comet! 252P/LINEAR looks like a big, fuzzy ball on March 18, 2016. The color comes from fluorescing diatomic carbon (two carbon atoms joined together). Credit: Michael Mattiazzo
A big, green comet! 252P/LINEAR looks like a big, fuzzy ball on March 18, 2016. The color comes from fluorescing diatomic carbon (two carbon atoms joined together). Credit: Michael Mattiazzo

252P/LINEAR is headed north! This comet has been in the news lately because it quickly brightened from near obscurity to naked eye visibility in just a week’s time. Why the sudden change? It’s on its way to a close but perfectly safe flyby of Earth tomorrow, when it will miss the planet by 14 times the distance of the moon (3.3 million miles / 5.3 million kilometers). That will briefly make 252P the 5th closest comet observed to fly by Earth.

As it approaches like a runaway train, the comet has not only increased in apparent size but now glows around magnitude +4. Heck, that’s bright enough to see from the suburbs, so long as the moon is out of the sky. Which it won’t be. More on that in a minute. Southern hemisphere skywatchers describe the comet as twice as tailless glow nearly twice as wide as the full moon with a small, brighter center.

Comet 252P/LINEAR passes closest to Earth tomorrow, missing us by 3.3 million miles. Credit: NASA/JPL
Comet 252P/LINEAR passes closest to Earth tomorrow, missing us by 3.3 million miles. The “P” in its name stands for “periodic”, meaning that it has a regular period around the sun, in this case 5.3 years. It was discovered in 2000. Credit: NASA/JPL

Prior to its sudden brightening, the comet was only visible in medium to large amateur telescopes very low in the southern sky in the constellation Columba the Dove (well south of Orion). It soon slipped out of view for skywatchers in mid-northern latitudes, headed for the deep southern sky. Tomorrow morning, 252P will be cruising across Apus, the Bird of Paradise, a faint constellation visible from the shores of Venezuela southward. By the 23rd, Floridians will catch it very low in the south before dawn in Ara the Altar.

252P/LINEAR passes near the Large Magellanic Cloud, a satellite galaxy of the Milky Way, on March 18th. Notice its hazy, diffuse appearance. Credit: Chris Wyatt
252P/LINEAR passes near the Large Magellanic Cloud, a satellite galaxy of the Milky Way, on March 18th. Notice its hazy, diffuse appearance. Credit: Chris Wyatt

Those of us in the central and northern U.S. will have our first opportunity for a look on Friday, March 25th when 252P climbs between three fingers to one fist high (depending on your latitude) due south in the tail of Scorpius the Scorpion shortly before dawn. Face south about two hours before sunrise, and you’ll see three bright “stars” in a triangle about 1/3 the way up from the horizon. The top two are the planets Saturn and Mars with Antares at the bottom (see map below). Both Mars and Antares have a nice reddish-orange color. Using Antares, glide your gaze down the sloping tail of Scorpius until you reach the end, marked by the brightish star, Shaula. The comet will in the area later this week.

Once it pops into the sky, it’s all gravy as 252P treks due north, rising higher and becoming better placed for viewing with each passing morning. Unfortunately, the gravy has a few lumps. Just as the comet makes its northern debut, a bright waning gibbous moon enters the morning sky in one of the worst cases of bad timing ever.

I suspect the moon will make this fuzzball challenging to spot with the naked eye, so if you’re want a look, bring your binoculars. Use the map to find the comet in binoculars and then lower the glasses to see if it might still be bright enough to see without. The moon gradually wanes during the coming week but also approaches the comet, continuing to make trouble for skywatchers. By April 1st, it will finally be far enough out of the picture. By that time, 252P is expected to fade to 6th or 7th magnitude — a bit too faint for most of us to see without binoculars.

This map shows comet 252P/LINEAR's daily progress from March 23-April 5, 2016 at 5:30 a.m.
This map shows comet 252P/LINEAR’s daily progress from March 23-April 5, 2016. Positions are shown for 5:30 a.m CDT with stars to magnitude +6. If you live in eastern time zone, the comet will be a smidge lower than the positions shown; if you live in the western U.S., a smidge higher. The bottom horizon is for southern Florida, the other shows the approximate horizon for the central and northern U.S. and southern Canada. Created with Chris Marriott’s SkyMap

The reason for its sudden rise from obscurity to celebrity is probably the fortunate coincidence of near simultaneous close approach of Earth on the 21st and reaching perihelion, its closest approach to the sun, on March 15. As if 252P/LINEAR’s close brush isn’t enough, a possible broken-off chunk of the comet traveling along a nearly identical orbit will make an ever closer pass on Tuesday, March 22. Around 11 a.m. CDT that day, P/2016 BA14, will zing just 2.1 million miles (3.4 million kilometers) or nine lunar distances of Earth, making it the second closest comet ever observed. Only Lexell’s Comet came closer (1.4 million miles / 2.2 million kilometers), but that was 246 years ago in 1770!

BA14 is expected to be faint (around magnitude +12-13) and only visible in larger amateur telescopes. It also will suffer the indignity of moonlight but not nearly as long; located high in the northern sky near the Big Dipper, we’ll see it in a dark sky starting on Friday the 25th. For more details on both comets, please check out my article on Sky & Telescope’s site.

I wish you well with this, our first naked eye comet of 2016. Please let us know if you see it by sharing your observation in the comments area. Thanks!

5 Responses

  1. John Testa

    It’s cold I found all the landmarks, I have my telescope and binoculars, but cannot find the comment

    .

    1. astrobob

      Hi John,
      It’s very possible the comet has faded more quickly. I’m preparing a deeper chart in today’s blog. Just a couple questions: what scope were you using and did you find where the comet was supposed to be and see nothing?

  2. Lynn faust

    Ive been out here looking for an hour with good binocs, but very bright moon seems to be exactly where comet should be

    1. astrobob

      Hi Lynn,
      Exactly what happened to me this morning! Finally, after days and days of overcast, it was clear, but it felt like a cruel joke with the moon so nearby. I searched as well with my 10x50s but saw nothing. I think instead I’ll just be patient and wait for the moon to thin out some more. Good luck on your next attempt, Lynn.

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