ALPO COMET NEWS FOR MARCH 2018
2018-March-03
Will March be a good month of comet observing? The answer depends on the aperture of your telescope and whether you are a visual or CCD observer. The bad news, unless a surprise discovery or outburst occurs, is that no comet this month will be an easy object for small telescope visual observers. The good news is large aperture visual observers and CCD imagers have quite the varied selection of objects to observe.
This month I decided to try a different format for these monthly summaries. I’m hoping the new format makes it easier to quickly identify observing targets. The comets will be broken down into three categories: comets brighter than magnitude 10, comets between magnitudes 10 and 13, and fainter comets of interest. In some cases, the comet of interest may no longer be visible but is the subject of recent research such as this month’s discussion of long-lost (or is it?) D/1770 L1 (Lexell).
Information for each comet is now presented in tabular form. This information includes the comet’s designation and name, date of perihelion (T), perihelion distance (q), and type of orbit (JFC for Jupiter family comet with period, HFC for Halley family comet with period, LPC-DO for dynamically old long-period comet, LPC-DN for dynamically new long-period comet). At 10 day intervals, the predicted magnitude, rough J2000 RA and Dec position, heliocentric distance, geocentric distance, elongations from the Sun (E for evening object, M for morning object) and constellation is shown.
Bright Comets (magnitude less than 10)
C/2017 T1 (Henize) – This intrinsically faint comet appears to have survived long enough to reach its February 21 perihelion passage at a rather small 0.58 AU from the Sun. As additional astrometric observations were made, the Minor Planet Center orbits for Heinze oscillated between a dynamically old and dynamically new solution. The latest orbit (released on Feb 28 with positions extending through Feb 12) shows Heinze to be dynamically new. Intrinsically faint, dynamically new objects are prone to fade rapidly after perihelion or even completely disintegrate. This is definitely a comet to keep an eye on. Unfortunately that won’t be easy as the comet starts the month close to the Sun. By the 2nd half of the month, Heinze will be far enough away from the Sun to be more easily seen though by then it may be a difficult visual object and also only visible from the southern hemisphere at that time.
C/2017 T1 (Heinze) T = 2018-Feb-21 q = 0.58 AU LPC-DN
Date Mag RA DEC r delta elong const
March 01 10 21 36 +10 19 0.60 1.32 25M Peg
March 11 11 21 39 +03 17 0.69 1.40 27M Aqr
March 21 12 21 45 -03 31 0.83 1.43 34M Aqr
March 31 13 21 53 -10 13 0.98 1.43 43M Cap
Faint Comets (between magnitude 10 and 13)
While there may not be any comet brighter than 10th magnitude this month, there are quite a few comets between magnitudes 10 and 13. In fact, there are seven comets in that brightness range.
C/2016 R2 (PANSTARRS) – The highlight of the bunch remains the ‘blue comet’. No not the famed Jersey Central passenger train, but comet C/2016 R2 (PANSTARRS). This comet is rich in CO+, or the carbon monoxide ion, which gives it a dynamic ion tail and blue color. The comet is still approaching its May 2nd perihelion. Its increasing comet-Earth distance will more than counter the shrinking heliocentric distance so a slow fade should occur this month. Recent magnitude estimates are still scattered but seem to be around 10th to 11th magnitude.
C/2015 O1 (PANSTARRS), C/2015 M1 (PANSTARRS), C/2016 N6 (PANSTARRS) – These three comets are similar to C/2016 R2 in that they are all PANSTARRS discoveries and have relatively large perihelion distances at 3.73, 2.21 and 2.67 AU, respectively. Recent observations place M1 at around magnitude 11 to 12.6. The other two are in the 12th to 13th magnitude range. O1 (for part of the month) and N6 (for the entire month) are northern circumpolar objects so both will be invisible for southern hemisphere observers.
62P/Tsuchinshan and 185P/Petriew – Both of these comets are now past perihelion. Making its 4th observed return, 185P/Petriew is now over a month past perihelion and slowly fading from 12th to 13th magnitude in the evening sky. 62P/Tsuchinshan should be fainter as it fades from 13th to 14th magnitude.
66P/du Toit – This year brings the 4th observed return of 66P/du Toit. Discovered in 1944 by South African astronomer Daniel du Toit, the comet was also seen at its returns in 1974 and 2003 but missed in 1959 and 1988. It is currently on an orbit with a 14.7 year period. This return will see its closest approach to Earth since its 1944 discovery apparition. The comet-Earth distance will still be a rather distant 0.90 AU. As a result, 66P may only brighten to 11th-12th magnitude. During its 2003 return, it rapidly brightened in the months prior to perihelion so this month may see the comet start at 17th magnitude and then brighten to 13th magnitude by month’s end. It will be a difficult object for northern observers due to its southern declination.
185P/Petriew T = 2018-Jan-27 q = 0.93 AU JFC P = 5.5 yr Date Mag RA DEC r delta elong const March 01 12 02 04 +04 31 1.04 1.34 50E Psc March 11 12 02 52 +06 52 1.11 1.38 52E Cet March 21 12 03 28 +08 49 1.19 1.45 54E Tau March 31 13 04 21 +10 18 1.28 1.54 55E Tau C/2016 R2 (PANSTARRS) T = 2018-May-02 q = 2.60 AU LPC-DO Date Mag RA DEC r delta elong const March 01 10 04 03 +30 20 2.71 2.61 84E Tau March 11 10 04 09 +32 42 2.68 2.72 76E Per March 21 11 04 18 +34 59 2.66 2.84 69E Per March 31 11 04 29 +37 11 2.64 2.95 62E Per C/2016 N6 (PANSTARRS) T = 2018-Jul-18 q = 2.67 AU LPC-DO Date Mag RA DEC r delta elong const March 01 12 15 15 +77 36 3.03 2.62 105E UMi March 11 12 12 19 +80 20 2.98 2.60 103E Cam March 21 12 10 01 +79 03 2.94 2.61 99E Dra March 31 12 08 43 +74 49 2.90 2.65 93E Cam 62P/Tsuchinshan T = 2017-Nov-16 q = 1.28 AU JFC P = 6.4 yr Date Mag RA DEC r delta elong const March 01 13 14 33 +02 35 1.78 1.04 123M Vir March 11 13 14 31 +03 22 1.85 1.02 133M Vir March 21 14 14 26 +04 11 1.92 1.02 143N Vir March 31 14 14 17 +04 54 1.98 1.04 153M Vir C/2015 O1 (PANSTARRS) T = 2018-Feb-19 q = 3.73 AU LPC-DN Date Mag RA DEC r delta elong const March 01 12 16 25 +39 11 3.73 3.44 99M Her March 11 12 16 14 +43 03 3.73 3.34 105M Her March 21 12 15 58 +46 56 3.73 3.27 110M Her March 31 12 15 37 +50 33 3.74 3.23 113M Boo 66P/du Toit T = 2018-May-19 q = 1.29 AU JFC P = 14.9 yr Date Mag RA DEC r delta elong const March 01 17 16 54 -29 02 1.65 1.41 84M Oph March 11 16 17 29 -32 11 1.57 1.28 86M Sco March 21 15 18 10 -35 10 1.50 1.16 88M Sgr March 31 13 18 57 -37 41 1.44 1.07 88M CrA C/2016 M1 (PANSTARRS) T = 2018-Aug-10 q = 2.21 AU LPC-DO Date Mag RA DEC r delta elong const March 01 11 19 14 +01 10 2.86 3.33 53M Aql March 11 11 19 22 +00 04 2.80 3.15 60M Aql March 21 11 19 29 -01 07 2.73 2.94 67M Aql March 31 11 19 35 -02 31 2.67 2.73 75M Aql
Other Comets of Interest
D/1770 L1 (Lexell) – This comet holds a few distinctions. One, it was the first Jupiter family comet to be recognized as such. Two, it holds the record for closest observed cometary approach to Earth at 0.015 AU or 5.8 lunar distances. Three, it was named not after its discoverer but its orbit computer (similar to 1P/Halley, 2P/Encke and 27P/Crommelin). Four, it was discovered by famed French comet hunter Charles Messier. Five, it hasn’t been seen since.
Quan-Zhi Ye (Caltech), Paul A. Wiegert (Western Ontario) and Man-To Hui (UCLA) have recently published their investigation into the whereabouts of Comet Lexell. They found that even though the comet has experienced numerous close approaches to Jupiter, there is a high probability that the comet still has a perihelion distance of < 3 AU and a close to even probability of having a perihelion distance of < 1 AU. A search of known comets turned up no possible linkages to Lexell but a search of known near-Earth asteroids did find a few possibilities. The authors identified NEA 2010 JL33 as the most likely object to be long-lost, and now inactive, Comet Lexell. 2010 JL33 is a dark (albedo of 0.047) object with a diameter of ~1.8 km which is consistent with a cometary nucleus. JL33’s next perihelion will occur in July 2019 at 0.71 AU. The object will be faint at 19th magnitude at that time and poorly placed at an elongation of 41 degrees.
A pre-print of the paper can be found at https://arxiv.org/pdf/1802.08904.pdf .
As always, the Comet Section is happy to receive all comet observations, whether images, drawings, magnitude estimates, and even spectra. Please send your observations via email to carl.hergenrother @ alpo-astronomy.org .
- Carl Hergenrother (ALPO Comet Section Coordinator)
