Comet Section        




Just a quick update on comets 252P/LINEAR and P/2016 BA14 (PANSTARRS). Both comets have now passed the point of closest approach to Earth. 252P passed within 0.036 AU of Earth on 21st while P/2016 BA14 passed within 0.024 AU on the 22nd.

P/2016 BA14 peaked at 12th magnitude and still shows only the most tenuous hint of cometary activity. For the most part, this comet was an imaging target and it looks like it’ll never get bright enough for easy visual observation. 252P, on the other hand, has definitely surprised. Based on its observed apparitions in 2000 and 2010, the prediction was for 252P to only get up to 10th magnitude. The caveat in that prediction is that it was never observed at perihelion so we really had no idea how bright it could get. The most recent magnitude estimates reported to the Comet Section from Luis Mansilla and Willian Souza showed the comet brightening from magnitude 7.0 on the 16th to 4.9 on the 20th. The observation from the 20th also reported a coma diameter of 1°.

P/2016 BA14 is a northern hemisphere object and will remain so. For the rest of the month it will travel through the constellations of Ursa Major (23-24), Canes Venectica (24-25), Ursa Major (25-26), Bootes (26-31), Hercules (31) as it fades from magnitude ~13 to ~15 at the end of the month.

252P took a far southern route and was invisible to northern observers. That is now changing as it moves northward through Ara (21-24), Scorpius (24-26), Ophiuchus (26-30) and Serpens (30-31). Though its recent brightness suggests a naked eye object, a near Full Moon and large coma will probably conspire to keep it a binocular or small telescope object. Since this is the first time 252P has been observed around perihelion, it may rapidly fade. The only way to know is to get out and observe it.

Frank Melillo submitted this video of P/2016 BA14 racing across the sky on March 22 over a span on 10 minutes.


As always, the Comet Section solicits all types of comet observations.

- Carl Hergenrother (ALPO Comet Section Coordinator)




March’s big story is the very close approach of not one, but two comets at the end of the month. Comets 252P/LINEAR and P/2016 BA14 (PANSTARRS) are both passing within 0.04 AU of Earth on March 21/22. 252P is already bright enough for visual observation. P/2016 BA14, on the other hand, may remain faint.

This will probably be your last month to visually observe C/2013 US10 (Catalina) as it is rapidly fading as it moves away from the Earth and Sun. Our other bright comet, C/2013 X1 (PANSTARRS), is too close to the Sun to be seen. It will reappear next month and be a nice binocular object for the next few months.

The Close Approachers

252P/LINEAR [Perihelion 2016-Mar-15 at 1.00 AU] and P/2016 BA14 (PANSTARRS) [Perihelion 2016-Mar-15 at 1.01 AU]

Both of these comets will be making the closest predicted return by a comet to Earth until 2109. 252P will be the first to flyby by making a very close approach to Earth on March 21 (13:15 UT) at 0.036 AU from the Earth (13.9 lunar distances). P/2016 BA14 will follow even more closely on the next day (March 22 at 15:31 UT)  at 0.024 AU or 9.2 lunar distances. If it seems quite a coincidence that the 3rd and 6th closest observed comet approaches (at least for objects we have good orbits for) are occurring within 27 hours of each, it is possible that these two comets are actually related to each other. Their orbits are similar though a difference in inclination of ~9° does call their relationship into question.

Both comets are expected to be low activity objects. 252P is the more active of the two and has already been reported as bright as 9-10th magnitude. It may brighten a little more by the time of close approach though it will not be an easy object as it appears to be a large, diffuse, low surface brightness object. It also helps if you live down south as 252P will be making a very rapid visit to the southern sky passing though the following constellations: Columba (Mar 1-9), Pictor (9-15), Dorado (15-16), Mensa (16-18), Octans (18-20), Apus (20-21), Ara (21-24), Scorpius (24-26), Ophiuchus (26-30) and Serpens (30-31).

P/2016 BA14 (PANSTARRS) will be taking a different path across the sky as it moves through Columba (Mar 1-11), Canis Major (11-18), Monoceros (18-20), Cancer (20-22), Leo Minor (22-23), Ursa Major (23-24), Canes Venectica (24-25), Ursa Major (25-26), Bootes (26-31), Hercules (31). Originally reported as an inactive comet, a faint tail was seen on images taken on Feb. 10 and 13 with the 4.3-m Discovery Channel Telescope in northern Arizona by University of Maryland astronomers. Unlike 252P, P/2016 BA14 is not brightening very fast and remains around 18th magnitude in images I obtained with a Sierra Stars Observatory Network telescope in Australia on Mar. 2 UT. It is questionable if the comet will ever get bright enough for visual observation. Both objects will be nice targets for CCD observers.

Efrain Morales Rivera observed both comets a few nights ago. His image show the contrast in their appearances and brightness.

Evening Comets

C/2013 US10 (Catalina) [Perihelion on 2015-Nov-15 at 0.82 AU from the Sun]

Comet Catalina is rapidly fading. After spends some months around 6th magnitude, it has now faded to 9-10th magnitude and will continue to rapidly fade as it moves away from the Sun (1.98 to 2.38 AU) and Earth (1.69 to 2.63 AU). It is a evening object located in the northern sky as it moves through Camelopardalis (Mar 1-16) and Perseus (16-31).

C/2013 X1 (PANSTARRS) [Perihelion on 2016-Apr-20 at 1.31 AU]

C/2013 X1 is too close to the Sun to be observed from Earth as its elongation drops from 18° to a minimum of 7° on March 17 then back up to 17°. Luckily we might be able to catch some glimpses of it for a few days around March 17 when it will pass within the FOV of the C3 coronagraph on the SOHO spacecraft. Next month, X1 will again be visible to Earth-based observers as it moves out of the Sun’s glare. With perihelion on April 20 at 1.31 AU from the Sun and a close approach to Earth of 0.64 AU in late June, X1 may be as bright as 6-7th magnitude from April through July.

Morning Comets

C/2014 S2 (PANSTARRS) [Perihelion on 2015-Dec-09 at 2.10 AU from the Sun]

The little comet that could, C/2014 S2 is still being reported as bright as 9th magnitude. C/2014 S2 (PANSTARRS) passed perihelion on December 9th at 2.10 AU from the Sun. As has been the case for the past few months, S2 is a northern circumpolar object moving through Ursa Minor (Mar 1-17), Draco (17-29) and Ursa Major (29-31) at declinations between +71 and +64 degrees. It is observable all night long for northern observers though it is much better placed in the morning. The comet is slowly moving away from the Sun (2.31 to 2.48 AU) and Earth (1.83 to 1.95 AU) so its brightness should fade from 9-10th magnitude to 10-11th magnitude..

New Discoveries

Since the last Comet Section News posting, two comet recoveries and two discoveries were reported.

335P/Gibbs = P/2016 A9 = P/2008 Y2 was recovered by E. Schwab of Egelsbach, Germany. He used a 1-meter reflector at the ESA’s Optical Ground Station on Tenerife island. The comet was 20th magnitude when recovered on January 10. It passed perihelion last November at 1.63 AU. Alex Gibbs discovered this comet during the course of the Catalina Sky Survey on the last day of 2008. Comet 335P is a short period with a period of 6.8 years.

336P/McNaught = P/2016 B2 = P/2006 G1 is the second return of a comet discovered by Rob McNaught in April 2006. Gareth Williams of the Minor Planet Center recovered 336P on images taken by the PanSTARRS survey on January 18 and February 14. The comet was 21st magnitude. The comet has a 11.3 year period and will reach perihelion on 2017 February 3 at 2.78 AU. It should reach a peak brightness of 18th magnitude.

C/2016 C1 (PANSTARRS) was found with the Pan-STARR1 telescope on Maui on February 12 at 19th magnitude. The long-period comet passed perihelion in January at a very distant 8.5 AU. It is likely to have gotten as bright as it will get.

C/2016 C2 (NEOWISE) was first seen on February 8 by the NEOWISE IR survey spacecraft at 19th magnitude. It has a period of 500-600 years and will reach perihelion at 1.56 AU on April 19 of this year. NEOWISE should brighten to 17th magnitude.

As always, the Comet Section is happy to receive all comet observations, whether images, drawings or magnitude estimates.
- Carl Hergenrother (ALPO Comet Section Coordinator)

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