Comet Section        




May was a bit of a slow month for the Comet Section. The brightest comet of the month, C/2015 G2 (MASTER), was only observable from the southern hemisphere (where our sole southern hemisphere visual observer, Willian Souza, has been following it). The second brightest comet, C/2014 Q2 (Lovejoy), was only seen by northern observers. Though Lovejoy is still around 8th magnitude, reported observations of this comet have fallen off. Perhaps we are all experiencing some Lovejoy fatigue after 8 months of observation (I know I only ventured outside once this month to observe Lovejoy).

June is a transitional month as we watch Lovejoy and MASTER fade and await the next two potentially bright objects. Unfortunately theses upcoming objects, C/2013 US10 (Catalina) and C/2014 Q1 (PANSTARRS), will be difficult to observe especially for northerners.

Evening Comets

C/2015 G2 (MASTER) [Perihelion on 2015-May-23 at 0.78 AU from the Sun]

In the middle of May, Comet MASTER peaked at magnitude 6.0 for a few days around its May 13 perihelion, possible due to a small outburst. For much of May the comet was between magnitude 6.3 and 7.1. ALPO contributor Willian Souza of Brazil has submitted 10 magnitude estimates of MASTER. His latest estimate from May 29 shows the comet having already faded to magnitude 7.1 as it moves away from the Sun (0.79 to 1.06 AU) and Earth (0.93 to 1.88 AU).

MASTER will only be visible from the southern hemisphere this month as an evening object in Monoceros (Jun 1-7), Canis Minor (7-26) and Cancer (26-30). It will be lost in the glare of the Sun even for southern observers later in the month and won’t reappear till September. By then northern observers will also be able to observe it though it may have faded below 11th-12th magnitude by then.

Recent ALPO images and observations of C/2015 G2 (MASTER) can be found in the Comet Section Image Galleryand Magnitude Database. Finder charts can be found at the ALPO Comet Finder Chart page.

Morning Comets

C/2014 Q2 (Lovejoy) [Perihelion on 2015-Jan-30 at 1.29 AU from the Sun]

Lovejoy is circumpolar for northern observers and will spend the whole month in Ursa Minor. Now 4 months past perihelion, the comet is still around magnitude 8.0-8.5.  Its distance from the Sun (1.86 to 2.18 AU) and Earth (2.09 to 2.31 AU) continues to increase.

Recent ALPO images and observations of C/2014 Q2 (Lovejoy) can be found in the Comet Section Image Gallery and Magnitude Database. Finder charts can be found at the ALPO Comet Finder Chart page.

88P/Howell [Perihelion on 2015-Apr-06 at 1.36 AU from the Sun]

Comet Howell is now 2 months past perihelion as it recedes from the Sun (1.48 to 1.64 AU) and moves a bit closer to Earth (1.70 to 1.65 AU) . Recent observations place Howell at magnitude ~10.0 though it should fade by a magnitude or so during June. The comet can be seen in the morning sky as it moves through Cetus (Jun 1-11), Pisces (12-30).

Recent ALPO images and observations of 88P/Howell can be found in the Comet Section Image Gallery and Magnitude Database. Finder charts can be found at the ALPO Comet Finder Chart page.

C/2014 Q1 (PANSTARRS) [Perihelion on 2015-Jul-06 at 0.31 AU from the Sun]

I wish we knew more about what this comet is up to. After discovery last August at a heliocentric distance of 4.9 AU, early predictions suggested PANSTARRS would peak at 2nd magnitude this summer. As is often the case with comets new to the inner Solar System, it brightened slowly and as of late May was only around magnitude 10-11. This suggests its peak brightness is more likely to be around magnitude 6.

Unfortunately, Q1 will be a difficult comet to observe. Northern observers are completely out of luck and will never get a good shot at the comet. Southern observers will have to wait till late July before it exits the glare of the Sun. This month Q1’s heliocentric distance decreases from 0.97 to 0.36 AU while its geocentric distance drops from 1.76 to 1.30 AU.

Recent ALPO images and observations of C/2014 Q1 (PANSTARRS) can be found in the Comet Section Image Gallery and Magnitude Database. Finder charts can be found at the ALPO Comet Finder Chart page.

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

Another inbound comet predicted to be bright this year is C/2013 US10 (Catalina). Located in Sculptor all month long, Catalina is well placed for southern observers but a difficult sight for northern watchers. The comet is currently between magnitude 11 and 12 and should continue to brighten as it approaches its November perihelion. It is still a rather distance 2.76 AU from the Sun at the start of the month and 2.38 AU at the end. Its distance from Earth drops from 2.68 to 1.82 AU.

Recent ALPO images and observations of C/2013 US10 (Catalina) can be found in the Comet Section Image Gallery and Magnitude Database. Finder charts can be found at the ALPO Comet Finder Chart page.

New Discoveries

A new crop of discoveries were announced in May. As usual, PANSTARRS leads the way in discoveries.

C/2015 GX (PANSTARRS) was initially classified as an asteroid following its April 8th discovery by the Pan-STARRS 1.8-m telescope. Over a month later on May 9, Roberto Haver detected cometary activity with a 0.37-m telescope in Frasso Sabino, Italy. Additional observations show C/2015 GX to be a Halley-type periodic comet with a period of 65 years and perihelion on 2015 August 26 at 1.97 AU from the Sun. The comet was around 20th magnitude at discovery and shouldn’t get much brighter then 18th magnitude (though Halley-types have a habit of brightening rapidly near perihelion).

C/2015 H2 (PANSTARRS) was discovered on April 24. Perihelion will be at a distant 4.95 AU in September of 2016. Currently 19th magnitude, this PANSTARRS discovery may only brighten up to 17th magnitude or so.

C/2015 J1 (PANSTARRS) passed perihelion last July at 6.03 AU. When first seen on May 14 it was a faint 20th magnitude which is as bright as it should get.

C/2015 J2 (PANSTARRS) is similar to the last two comet finds. It is also a faint high-q long-period comet. Found on May 15 it will pass perihelion in September at 4.32 AU and shouldn’t get much brighter than its current 18-19th magnitude.

P/2015 J3 (NEOWISE) is a short-period comet with a period of 6.4 years and perihelion of 1.50 AU. Discovered by the NEOWISE program being conducted by the WISE IR spacecraft, NEOWISE is a faint comet that shouldn’t get brighter than 19th magnitude.

C/2015 K1 (MASTER) is the second discovery of 2015 by the “Mobile Astronomical System of the Telescope-Robots” project. Similar to C/2015 G2, K1 was found with one of their 0.4-m telescopes in South Africa. It passed perihelion back in October at 2.57 AU from the Sun when it should have been around 14th magnitude. Located deep in the southern sky it went unnoticed at the time. The comet is now 16-17th magnitude and fading.

C/2015 K2 (PANSTARRS) is a runt. Even though it will come reasonably close to the Sun at 1.46 AU on 2015-Jun-08 and was 0.56 AU from Earth when discovered on May 18, the comet is an extremely faint 20-21th magnitude.

C/2015 K4 (PANSTARRS) is a long-period comet discovered by PANSTARRS on May 24 at 18-19th magnitude. With perihelion already passed (2015-May-01 at 2.01 AU), the comet is as bright as it will get.

51P-D/Harrington is a piece of the main nucleus of comet 51P/Harrington which experienced splitting events in 1994 and 2001. Component D was observed to separate from 51P back in late 2001. Surprisingly, Pan-STARRS recovered component D on May 30 at 22nd magnitude. 51P-A (the primary) and 51P-D are separated by a little over half of a degree on the sky. 51P-A has recently been observed at 16th magnitude as it approaches its August perihelion at 1.70 AU from the Sun (when it’ll be 13th magnitude).

As always, the Comet Section is happy to receive all comet observations, whether images, drawings or magnitude estimates.

- Carl Hergenrother (Acting ALPO Comet Section Coordinator)

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