Comet Section

ALPO COMET NEWS – AUGUST 2017

2017-July-31

When I first started writing this month’s Comet News the focus was going to be on how after 8 months that saw 8 comets reach 10th magnitude or brighter, the rest of the year was going to bring a bright comet drought. While this may still be true, a new discovery provides some hope that this Fall will see at least one come bright enough for most small telescope observers.

Evening C0mets

C/2015 V2 (Johnson) [Perihelion on 2017 June 12 at 1.64 au]

Comet Johnson is no longer visible from the northern hemisphere. By the time it heads far enough north to be seen by most northern observers it will have faded beyond the reach of all visual and most CCD observers. Southern comet watchers will still be able to follow Johnson this month as it moves through Centaurus (Aug 1-25) and Lupus (26-31). Currently around magnitude 9.0, it will fade by another magnitude this month as it moves away from the Sun (1.77 to 1.95 au) and Earth (1.35 to 1.83 au).

71P/Clark [Perihelion on 2017 June 30 at 1.59 au]

Discovered back in 1973, periodic comet 71P/Clark is making its 8th observed return. Similar to the last two months, Clark will spend all month in Scorpius. Recent reports place the comet between magnitude 10.5 and 11.0. Steady fading should continue as the comet retreats from the Sun (1.62 to 1.69 au) and Earth (0.79 to 1.04 au).

29P/Schwassmann-Wachmann 1 [Perihelion on 2019 March 7 at 5.77 au]

Regular outbursting comet 29P/Schwassmann-Wachmann 1 is now on the evening side of opposition near the Capricornus/Aquarius border. Always active, the comet can reach 12th magnitude during its outbursts. As August begins it is at magnitude 14 and slowly fading after a recent outburst. Monitoring of 29P’s outbursts will help better constrain its rotation period and outburst mechanisms. This is one comet where rapid changes in brightness and coma morphology make day-to-day monitoring worthwhile.

Morning Comets

C/2015 ER61 (PANSTARRS) [Perihelion on 2017 May 9 at 1.04 au]

C/2015 ER61 (PANSTARRS) reached perihelion back in May and has faded rather rapidly to between magnitude 10.5 to 11.5. The comet will continue to fade as it moves away from the Sun (1.69 to 2.04 au) and Earth (1.67 to 1.68 au). ER61 is a morning object this month moving through Taurus.

217P/LINEAR [Perihelion on 2017 Jul 16 at 1.24 au]

217P had a nice apparition last time around in 2009 when it brightened to 9th magnitude. This year’s apparition won’t be as good with it only brightening to 12-13th magnitude. Southern CCD observers will be able to watch it as it moves through Orion all month. The comet is now moving away from the Sun (1.25-1.36 au) and Earth (1.44-1.48 au). CCD observations are especially requested as 217P displayed some interesting jet features in 2009.

C/2017 O1 [Perihelion on 2017 Oct 13 at 1.51 au]

Comet Assassin! No it’s not the name of the latest video game your kids or grandkids are playing, but it is the possible name of a bright comet discovered by the ASAS-SN (All-Sky Automated Survey for Supernovae) project. C/2017 O1 was first seen with the the ASAS-SN quadruple 14-cm “Cassius” telescope on Cerro Tololo, Chile on July 19 UT (discovery Astronomical Telegram #10597). In the first few days after discovery, the comet experienced an outburst to magnitude ~10.5. A report by Erik Bryssinck & F.-J. Hambsch on the comets-ml suggest another small outburst occurred between July 28 and 29 UT.

What the future holds for C/2017 O1 is still unknown. Here is what we do know. C/2017 O1 appears to be a long-period comet though whether it is dynamically new or old is still to be determined. The comet is currently 1.82 au from the Sun and 1.51 au from Earth. Those distances will drop to 1.63 au and 1.07 au by the end of the month. It is a morning comet moving northeast through Eridanus (Aug 1-12), Cetus (12-19) and Taurus (19-31). Perihelion occurs on October 14 at 1.51 au from the Sun and closest approach to Earth on October 17 at 0.72 au. If its current 10th magnitude is indicative of its true brightness (and not just the result of a short-lived outburst), the comet may brighten to 7th-8th magnitude in October. At that time it will also be a northern circumpolar object.

As for the name or lack thereof, the IAU Small Body Nomenclature committee will probably decide on the official name for C/2017 O1 when the next official orbit is released. It will be interesting to see if it will be Comet ASAS-SN, Comet ASASSN or even be named after the human ASAS-SN member who first saw it.

Other Comets in the News

(457175) 2008 GO98

Gianluca Masi and Efrain Morales Rivera have submitted images this past month of comet (457175) 2008 GO98. If (457175) 2008 GO98 seems like a strange designation for a comet, it is. The designation is actually for a numbered asteroid. Between its first reported sighting in 2001 and early 2016, this object didn’t appear to display any cometary activity. All that changed in early 2016 when the object rapidly brightened from 21st to 17th magnitude. Though well observed in 2016, no one noticed the brightening or any cometary features. It wasn’t until July 3rd of this year, that Greg Leonard noticed a coma and short tail in images taken with the Mount Lemmon 1.5-m.

While on an orbit that resembles a member of the Hilda family of asteroids, backward integrations of its orbit show that it has made many close approaches to Jupiter in the past and 300 years ago was on a Centaur orbit entirely exterior to Jupiter. This all suggests that it is not an asteroid that is acting like a comet but rather a comet that mimiced an asteroid for awhile.

International Comet Quarterly

The original clearinghouse of comet photometry and observation has returned after a hiatus of 7 years. The April 2010 issue (ICQ 154) has been published. A free downloadable copy is available at the ICQ website.

As always, the Comet Section is happy to receive all comet observations, whether images, drawings or magnitude estimates. Please send your observations via email to < carl.hergenrother @ alpo-astronomy.org >.

- Carl Hergenrother (ALPO Comet Section Coordinator)

A new bright comet has been discovered. The All-Sky Automated Survey for SuperNovae (ASAS-SN) uses their 14cm “Cassius” telescope (really a Nikon AF-S NIKKOR
400mm F2.8G ED VR lens paired with a Finger Lakes ProLine PL230 CCD camera) on Cerro Tololo in Chile to conduct a search for new supernovae. On July 19, ASAS-SN came across a new comet. While CCD observers have been placing the new object between magnitude 12 and 16, a few visual observers have estimated it to be as bright as magnitude 10.

A preliminary orbit released by the Minor Planet Center shows C/2017 O1 to be a long-period comet currently located at 1.88 au from the Sun and 1.63 au from Earth. Since it is heading inbound to a perihelion on October 14 at 1.51 au from the Sun and a close approach to Earth on October 17 at 0.72 au, the comet should brighten. How bright is still uncertain but it may become as bright as 8th magnitude. At present, it can be seen near the Cetus-Eridanus border. Slowly traveling north, it will be a northern circumpolar object by mid-October.

The IAU announcement of the discovery of C/2017 O1 did not include a name. It will be interesting to see what name this comet ultimately carries. The acronym ASAS-SN is pronounced ‘assassin’ which will give this comet quite a unique name. An earlier system discovered comets C/2004 R2 (ASAS) and C/2006 A1 (Pojmanski) making C/2017 O1 the third discovery by the ASAS/ASAS-SN team.

With C/2015 V2 (Johnson) slowly receding from view over the next few weeks for northern observers, C/2017 O1 will provide a much needed target for northern comet observers during the second half of 2017.

Ephemerides can be produced at the MPC here.

ALPO COMET NEWS – JULY 2017

2017-July-4

The first half of 2017 saw 8 comets reach 10th magnitude or brighter. There were even times when 4 comets were observable in a night with small equipment. The second half of 2017 will see a slow down in activity. After the current crop of comets fade, it is possible that no additional comets will brighten to better than 10th magnitude till next summer.

Evening observers can continue to monitor C/2015 V2 (Johnson) as it moves south through Virgo, Hydra and into Centaurus. Morning observers can watch C/2015 ER61 (PANSTARRS) slowly fade in Aries. For large aperture visual and CCD observers, comets 29P/Schwassmann-Wachmann 1, 71P/Clark and 217P/LINEAR are between 10th and 13th magnitude.

This past June the Comet Section received comet magnitude estimates for comets 71P/Clark, C/2015 ER61 (PANSTARRS) and C/2015 V2 (Johnson) from Salvador Aguirre, Carl Hergenrother, John Sabia and Willian Souza. CCD images were received for comets 71P/Clark, C/2015 ER61 (PANSTARRS) and C/2015 V2 (Johnson) from Gianluca Masi, John D. Sabia, Chris Schur and Michael Schwartz.

Evening C0mets

C/2015 V2 (Johnson) [Perihelion on 2017 June 12 at 1.64 au]

The brightest comet this month should be Comet Johnson. Since March, it has been brighter than 10th magnitude with a peak between magnitude 7.5 and 8.0 in May/June. This month will probably be the last time most northern observers will be able to observe Johnson as it moves rapidly south through Virgo (July 1-16), Hydra (16-28), Centaurus (28-31). By the end of the month, it will be at a southern declination of -32 deg. As mentioned in the past few posts, Johnson appears brighter in small binoculars compared to larger telescopes. While its true brightness is currently between magnitude 8.0 and 8.5, binocular observers are seeing it up to 0.5-1.0 magnitudes brighter due to contamination from its large high surface dust tail. Regardless of what instrument you use, Johnson should fade by up to a magnitude during the month as its moves away from the Sun (1.66 to 1.77 au) and Earth (0.95 to 1.35 au). The image below was taken by Chris Schur on June 15 with a 10″ f/3.9 Orion astrograph and SBIG ST-10XME.

71P/Clark [Perihelion on 2017 June 30 at 1.59 au]

Discovered back in 1973, periodic comet 71P/Clark is making its 8th observed return. Similar to last month, it will spend all month in Scorpius as it moves south from -33 to -37 deg declination. Recent reports place the comet between magnitude 9.7 and 10.2. This apparition marks Clark’s best as it comes as close to the Earth as it can on its current orbit. Perihelion and closest approach to Earth occurred last month so it will be slowly moving away from the Sun (1.59 to 1.62 au) and Earth (0.63 to 0.79 au) resulting in fading from magnitude 10 to 11.

41P/Tuttle-Giacobini-Kresak [Perihelion on 2017 Apr 12 at 1.05 au]

It is now 3 months since 41P/T-G-K’s close approach to Earth in April. The comet is rapidly fading and starts the month around magnitude 11 and may fade to 15 by the end of the month. This month 41P will move through Serpens Cauda as it moves away from the Sun (1.47 to 1.73 au) and Earth (0.47 to 0.81 au).

The 4*P Coma Morphology Campaign is interested in images of comets 41P as well as 45P/H-M-P from earlier this year and images of next year’s 46P. The Campaign will use images of these comets to derive their rotational state, characterize their nucleus’ activity, characterize outbursts, and learn more about gas and dust properties in the coma (e.g., outflow velocities), chemical origin of gas species in the coma, and temporal behavior of the tail structure. This is an excellent opportunity to contribute to an amateur-professional corroboration. Though 41P is getting rather faint, the campaign is still interested in observations for as long as possible. If you would like me to facilitate your submission of images or contact with the 4*P Campaign, just let me know.

Morning Comets

29P/Schwassmann-Wachmann 1 [Perihelion on 2019 March 7 at 5.77 au]

As the number of bright comets dwindles, we are digging a little fainter for targets such as the enigmatic comet 29P/Schwassmann-Wachmann 1. This comet is always active even though it never gets much closer to the Sun than Jupiter. With an eccentricity of 0.04, it also doesn’t get too much further from the Sun than Jupiter. Currently, the comet can be classified as a Centaur with a 14.8 year period. S-W 1 also regularly experiences outbursts from its usual brightness of 16-18th magnitude to peaks near 12-13th magnitude. Recent research suggests that 29P has a slow rotation period on the order of days. Work by prolific BAA Comet Section contributor Richard Miles places the rotation period at 57 days. Further monitoring of 29P’s outbursts will help better constrain its rotation period and outburst mechanisms. This is one comet where rapid changes in brightness and coma morphology make day-to-day monitoring worthwhile. This year 29P will be near the border of Capricornus and Aquarius near declinations of -13 to -14 deg.

C/2015 ER61 (PANSTARRS) [Perihelion on 2017 May 9 at 1.04 au]

C/2015 ER61 (PANSTARRS) reached perihelion back on May 9 at 1.04 au from the Sun and is moving away from the Sun (1.35 to 1.69 au) and Earth (1.56 to 1.67 au). Back in April, it experienced a 2 magnitude outburst. This outburst may have been due to a splitting event as recent CCD images have detected a secondary. Due to its increasing distance to the Sun and Earth it will slowly fade from around magnitude 10.0 to 10.5. All month, ER61 is a morning object moving through Aries.

217P/LINEAR [Perihelion on 2017 Jul 16 at 1.24 au]

217P had a nice apparition last time around in 2009 when it brightened to 9th magnitude. This year’s apparition won’t be as good with it only brightening to 12-13th magnitude. Southern CCD observers will be able to watch it as it moves through Cetus (Jul 1-10) and Taurus (10-3). Northern observers will also be able to see it though it will be at a low elevation, though it slowly climbs higher as the month progresses. The comet spends the entire month 1.24-1.25 au from the Sun and 1.43-1.44 au from Earth. CCD observations are especially requested as 217P displayed some interesting jet features in 2009.

Other Comets in the News

Last month, I discussed newly discovered C/2017 K2 (PANSTARRS). There were some questions about it in that it appeared to be a very bright Halley-type comet headed for a close perihelion in 2023. The big question was how could such a large bright object not have been seen at its last perihelion. A new orbit published by the MPC clears up some of the mystery. K2 now appears to be a long-period comet rather than a Halley-type with Perihelion occurring in December 2022 at 1.80 au.

It is too early to know how bright this comet will get. Just extrapolating its current brightness suggests it will peak near 6th magnitude. There are a few things going against K2 becoming a bright object. One, it will only come within 1.8 au of Earth and will be 2.4 au from Earth at perihelion. Two, the latest orbit makes K2 a dynamically new comet. This can help explain its high intrinsic brightness at 16 au. It also throws up a huge red flag since dynamically new comets are prone to underperforming near perihelion. Regardless, it is unprecedented to be able to monitor a long-period comet for so long as it approaches a small perihelion distance. CCD observers are asked to place K2 on there regular program and to image this comet monthly.

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

- Carl Hergenrother (ALPO Comet Section Coordinator)

COMET JOHNSON AT ITS BEST

2017-Jun-15

Saturn isn’t the only solar system body at its best this month. Comet Johnson is also at its best and is well placed as soon as it gets dark after sundown.

C/2015 V2 (Johnson) was first spotted by Jess Johnson of the Catalina Sky Survey back in November of 2015. It is a dynamically new comet with an original orbit almost indistinguishable from a parabola. Perturbations by the major planets have transformed its orbit to hyperbolic so this will be Johnson’s only trip through the inner solar system. Perihelion was only a few days ago (Jun 12) at a rather distant 1.64 au. Closest approach to Earth was earlier in the month (Jun 5) at 0.81 au.

Johnson is currently located over a dozen degrees south of Arcturus as it moves south through Virgo (finder charts can be found here and here). There has been some inconsistencies in its reported brightness. Binocular users are reporting it around magnitude 7.5 while telescope users are reporting it around magnitude 8.0 to 8.5. The plot below shows visual magnitudes submitted to the Comet Section. For the most part, those points above the green curve were made with binoculars while those below the curve were made with larger aperture telescopes. Regardless of what instruments you use, how bright do you think Johnson is?

The scatter in magnitudes may be due to Johnson’s bright broad dust tail. The tail is obvious in the below image taken by Chris Schur on June 15 with a 10″ Orion F/3.9 astrograph + SBIG ST10XME. It is possible that binocular observers are including some of the tail in their brightness estimate resulting in brighter magnitudes.

John D Sabia used a Canon DSLR and telephoto lens to image the comet on June 13. The image gives a good impression of what Johnson looks like in small apertures. The tail is also visible in this image.

So far the Comet Section has received 34 magnitude estimates from Salvador Aguirre, Carl Hergenrother, John Sabia and Willian Souza and 38 images from Charles Bell, Denis Buczynski, John Chumack, Carl Hergenrother, Manos Kardasis, Gianluca Masi, Richard Owens, Efrain Morales Rivera, John Sabia, Chris Schur and Michael Schwartz.

If you are out this weekend observing, please give Johnson a look. Whether you image it, make a magnitude estimate or just take a quick peek, submit your observations and impressions to the Comet Section.

ALPO COMET NEWS FOR JUNE 2017

2017-May-31

The nights may be getting shorter but they sure are warmer (and probably buggier as well). Two comets are nice and bright for June observers. C/2015 V2 (Johnson) is now 7th magnitude and visible for much of the night. Another long-period comet, C/2015 ER61 (PANSTARRS) is around 8th magnitude but only visible before dawn. For larger aperture observers, quickly fading 41P/Tuttle-Giacobini-Kresak and 10th magnitude 71P/Clark are also visible.

Last month the Comet Section received comet magnitude estimates for comets 41P/Tuttle-Giacobini-Kresak, C/2015 ER61 (PANSTARRS) and C/2015 V2 (Johnson) from Salvador Aguirre, Carl Hergenrother and Willian Souza. CCD images were received for comets 45P/Honda-Mrkos-Pajdusakova, C/2015 ER61 (PANSTARRS) and C/2015 V2 (Johnson) from Gianluca Masi, Richard Owens, John D. Sabia, Chris Schur and Michael Schwartz.

Evening C0mets

C/2015 V2 (Johnson) [Perihelion on 2017 June 12 at 1.64 au]

Comet Johnson will be at its best this month as it passes perihelion on June 12 at 1.64 au and closest approach to Earth on June 5 at 0.81 au. The comet is well placed and can be observed as soon as it gets dark in the evening. The comet starts the month a few degrees to the northeast of Arcturus and moves south during the month [Bootes (Jun 1-14) and Virgo (14-30)]. Currently between magnitude 7.5 and 8.0, the comet is an easy object for binocular and small telescope users. It should remain nearly as bright for most of the month through it may start to fade as it moves away from the Sun (1.64 to 1.66 au) and Earth (0.81 to 0.95 au).

C/Johnson was first seen back in November 2015 when it was 17th magnitude and located 6.5 au from the Sun. The fact that it was so bright when so far from the Sun suggests a large amount of dust was released in the years prior to discovery. This is rather typical of dynamically new comets making their first trip through the inner solar system. Dynamically new comets also usually brighten at a slow rate. While there was some hope it would brighten to 5th – 6th magnitude it looks like its current 7th magnitude is as bright as it willl get. All of that dust released over the past few years has provided Johnson with a nice bright dust tail. On June 1, the Earth is in line with Johnson’s orbit plane making the dust tail even more pronounced. The image below was taken by Chris Schur on May 28 and shows two tails pointing nearly 180 degrees apart (the broad bright dust tail to the lower left and a narrower fainter gas tail to the upper right).

71P/Clark [Perihelion on 2017 June 30 at 1.59 au]

Michael Clark discovered this comet photographically in 1973 from Mount John University Observatory in New Zealand. With an orbital period of 5.6 years, 2017 marks Clark’s 8th observed return. It spends the entire month in Scorpius (starting a few degrees to the southeast of Antares and moving slowly south from there). Its distance from the Sun is slowly decreasing as it approaches perihelion at 1.59 au on June 30. The comet will come as close to the Earth as it can on its present orbit on June 11 at 0.59 au. It is currently between magnitude 10.5 and 11.0 and should get a little brighter this month.

Morning Comets

41P/Tuttle-Giacobini-Kresak [Perihelion on 2017 Apr 12 at 1.05 au]

Now about 2 months removed from its close approach to Earth in April, 41P/T-G-K is currently between magnitude 9.5 and 10.0 and may fade to 13-14 by the end of the month. Unfortunately it did not experience one of its famous 10 magnitude outbursts. At least not yet. This month 41P will move through Hercules (Jun 1-4), Ophiuchus (4-13), Serpens Cauda (13-15), Ophiuchus (15-24) and Serpens Cauda (24-30) as it moves away from the Sun (1.24 to 1.47 au) and Earth (0.29 to 0.47 au). It is a morning object all month with an elongation that increases from 134 to 159 degrees. It starts the month between magnitude 9.5 and 10.0 and may fade to 13-14 by the end of the month.

C/2015 ER61 (PANSTARRS) [Perihelion on 2017 May 9 at 1.04 au]

June’s other long-period comet is C/2015 ER61 (PANSTARRS). It reached perihelion on May 9 at 1.04 au from the Sun and is moving away from the Sun (1.11 to 1.35 au) and Earth (1.38 to 1.56 au). Back in April, it experienced a 2 magnitude outburst. Since then the comet has settled back down and is currently 8th magnitude. Due to its increasing distance to the Sun and Earth it will slowly fade this month to 9th magnitude. All month, ER61 is a morning object moving through Pisces (Jun 1-15) and Aries (15-30).

Other Comets in the News

Newly discovered C/2017 K2 (PANSTARRS) is a bit of an enigma. Currently located 16 au from the Sun, K2 will not reach perihelion at 1.7 au until 2023! Extrapolating its current brightness results in a 5th magnitude comet for almost half of 2023. The main problem (actually there are a few) is that K2 is on a Halley-type with a 125 year period. If K2 were just as bright 125 or so years ago it would have been easily discovered. Perhaps the comet is experiencing an outburst. Only time, and monitoring, will tell.

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

- Carl Hergenrother (ALPO Comet Section Coordinator)

ALPO COMET NEWS FOR MAY 2017

2017-May-3

April was a busy month for the Comet Section as 4 comets were observed visually and 10 comets imaged with CCDs. The most exciting comet of the month was C/2017 E4 (Lovejoy). Discovered in March, this comet rapidly brightened to 6th magnitude before beginning a sudden fade. Gianluca Masi and Michael Schwartz observed it on 14 nights during April. Their latest observation shows a comet in distress and one whose nucleus may have already disintegrated. Most disintegrators are dynamically new so Lovejoy is a little strange in that it is a dynamically old comet. Still, there are a few examples of dynamically old comets that have disintegrated including C/1996 Q1 (Tabur) and even periodic comets 3P/Biela and 20D/Westphal.

Last month the Comet Section received comet magnitude estimates for comets 41P/Tuttle-Giacobini-Kresak, C/2015 ER61 (PANSTARRS), C/2015 V2 (Johnson) and C/2017 E4 (Lovejoy) from Salvador Aguirre, Carl Hergenrother and Willian Souza. In addition to C/2017 E4 (Lovejoy), CCD images were also received for comets 41P/Tuttle-Giacobini-Kresak, 45P/Honda-Mrkos-Pajdusakova, 71P/Clark, 73P/Schwassmann-Wachmann 3, 213P/Van Ness, 315P/LONEOS, C/2013 X1 (PANSTARRS), C/2015 ER61 (PANSTARRS) and C/2015 V2 (Johnson) from Charles Bell, John Chumack, Carl Hergenrother, Manos Kardasis, Gianluca Masi, Richard Owens, John D. Sabia, Chris Schur and Michael Schwartz.

This May morning observers will be able to follow a few comets in small telescopes as C/2015 ER61 (PANSTARRS) and C/2015 V2 (Johnson) are both 7th to 8th magnitude. Larger telescope users will be able to follow fading 41P/Tuttle-Giacobini-Kresak and brightening 71P/Clark.

Morning Comets

41P/Tuttle-Giacobini-Kresak [Perihelion on 2017 Apr 12 at 1.05 au]

41P/T-G-K approached to within 0.14 au of Earth on April 1 when it brightened to around magnitude 7.0. There was hope that the comet would experience an outburst like it did in 1973 but so far no luck. The comet is currently fading and is already a difficult object for many observers due to its low surface brightness coma. This month 41P will move through Hercules (May 1), Lyra (1-16) and Hercules (16-31) as it moves away from the Sun (1.08 to 1.23 au) and Earth (0.19 to 0.29 au). It is a morning object all month with an elongation that increases from 105 to 133 degrees. It starts the month between magnitude 7.5 and 8.0 and may fade to 9.0 to 10.0 by the end of the month.

Below is an image of 41P obtained by Chris Schur on April 29.

71P/Clark [Perihelion on 2017 June 30 at 1.59 au]

Michael Clark discovered this comet photographically in 1973 from Mount John University Observatory in New Zealand. With an orbital period of 5.6 years, 2017 marks this comet’s 8th observed return. Clark will start the month in Ophiuchus (May 1-22) at 11th magnitude before moving into Scorpius (23-31) and brightening to around 10th magnitude. Its distance from the Sun will shrink from 1.68 to 1.61 au. With a geocentric distance that drops from 0.74 to 0.60 au this month, the comet will come as close to the Earth as it can on its present orbit.

C/2015 ER61 (PANSTARRS) [Perihelion on 2017 May 9 at 1.04 au]

Comet PANSTARRS experienced a 2+ magnitude outburst in early April that brought it close to magnitude 6.0. Since then the comet has settled back down to its expected brightness of magnitude 7.5 to 8.0. It will reach perihelion on May 9 at 1.04 au from the Sun but be rather far from Earth at 1.20 to 1.37 au from Earth. A morning sky object, it will be in Pisces all month long as its elongation shrinks from 56 to 52 degrees. Barring further outbursts, PANSTARRS should remain around its current magnitude all May.

C/2015 V2 (Johnson) [Perihelion on 2017 June 12 at 1.64 au]

Comet Johnson is a little more than a month from its closest approach to Earth on June 5 at 0.81 au and perihelion on June 12 at 1.64 au. There has been some controversy on the comets-ml Yahoo group as to exactly how bright this comet. Observers using binoculars (such as myself) have reported the comet as bright at magnitude 7.6. Larger telescope observers are estimating the comet to be as faint as magnitude 9.0. While the comet is obvious to me in 10×50 binoculars, it is possible that my estimates are too bright due to contamination from a very bright dust tail that is unresolvable in small binoculars. Large aperture observers can differentiate the coma from the tail resulting in fainter total magnitude measurements. Regardless, Johnson should continue to brighten by another magnitude this month as it approaches the Sun (1.73 to 1.64 au) and Earth (1.01 to 0.82 au). It is still a morning object as its moves through Hercules (May 1-2) and Bootes (2-31).

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

- Carl Hergenrother (ALPO Comet Section Coordinator)

ALPO COMET NEWS FOR APR 2017

2017-April-5

The sky is now full of bright comets. We expected periodic comet 41P/Tuttle-Giacobini-Kresak to be around 6th magnitude this month, but two others have also reached that level of brightness. C/2015 ER61 (PANSTARRS) experienced a 2 magnitude outburst on April 4 or 5 and is now 6th magnitude. Newly discovered C/2017 E4 (Lovejoy) was only first seen on March 12 and has rapidly brightened to magnitude 6.5. Considering C/2015 V2 (Johnson) is also still brightening, though it is “only” at 9th magnitude, there’s lots to see this month.

Last month the Comet Section received comet magnitude estimates for comets 2P/Encke, 41P/Tuttle-Giacobini-Kresak, C/2015 ER61 (PANSTARRS), C/2015 V2 (Johnson) and C/2017 E4 (Lovejoy) from Salvador Aguirre, Carl Hergenrother, John D. Sabia and Willian Souza. CCD images were also received for comets 41P/Tuttle-Giacobini-Kresak, 45P/Honda-Mrkos-Pajdusakova, 71P/Clark, 73P/Schwassmann-Wachmann 3, 315P/LONEOS, C/2015 ER61 (PANSTARRS), C/2015 V2 (Johnson) and C/2017 E4 (Lovejoy) from John Chumack, Carl Hergenrother, Gianluca Masi, John D. Sabia, Chris Schur and Michael Schwartz.

Morning Comets

2P/Encke [Perihelion on 2017 March 10 at 0.34 au]

Comet Encke brightened to 8th magnitude in late February before passing too close to the Sun to be seen. Willian Souza of Brazil was able to reobserve Encke on March 26 at magnitude 7.7. Encke will only be visible from the southern hemisphere as it moves through Aquarius. It will fade from 9th to 12th magnitude as it recedes from both the Sun (0.65 to 1.16 au) and Earth (0.91 to 1.16 au).

41P/Tuttle-Giacobini-Kresak [Perihelion on 2017 Apr 12 at 1.05 au]

41P/T-G-K approached to within 0.14 au of Earth on April 1. Though this comet has brightened to 6th magnitude and is well place for northern observers, it has proved a difficult object to see. As is common for intrinsically faint comets that come close to Earth, 41P is a large object with a low surface brightness coma. As a result, low magnification and dark skies are needed to see it. CCD imagers are having a better time recording this comet.

The comet should slowly fade from 6th to 7th magnitude this month. Though perihelion occurs on April 12 and its heliocentric distance doesn’t change much, its geocentric distance increases from 0.14 to 0.19 au. The comet is currently circumpolar in Draco at a declination of +64 deg. The comet will still be a northern object at the end of the month in Hercules (declination of +39 deg). While 41P is prone to enormous outbursts it has been well behaved so far.

Image below was taken by John D. Sabia on March 30 showing structure in the inner coma of 41P.

C/2015 ER61 (PANSTARRS) [Perihelion on 2017 May 9 at 1.04 au]

Up to a few days ago C/2015 ER61 (PANSTARRS) was slowly brightening and shining at magnitude 8.5. After a two magnitude outburst, the comet is now around magnitude 6.2 to 6.5. C/PANSTARRS will reach perihelion on May 9 at 1.04 au from the Sun but never gets closer to Earth than 1.18 au. For northern observers, it will be located low in the morning sky. It will be better placed for southern observers. This month its distance from the Sun increases from 1.22 au to 1.05 au. Its geocentric distance stays around 1.23 to 1.18 au as it travels through Capricornus (Apr 1-5), Aquarius (5-12), Capricornus (12-18), Aquarius (18-29) and Pisces (29-30). How bright it will be this month is uncertain. If its recent outburst is a short-lived event, the comet may fade back to 8th magnitude. Alternately, additional outbursts may further its brightening.

C/2015 V2 (Johnson) [Perihelion on 2017 June 12 at 1.64 au]

Comet Johnson is inbound with a perihelion of 1.64 au and close approach to Earth at 0.81 au this summer. It is well placed for northern observers through perihelion. Its rate of brightening has been slow so this month it is only expected to brighten from magnitude 9.5 to 8.5. During April, it is a morning object in Hercules at an elongation that increases from 108 to 118 degrees. It starts the month 1.90 au from the Sun and 1.33 au from Earth. At the end of the month, these values decrease to 1.73 au from the Sun and 1.01 au from Earth. C/Johnson is still on pace to peak between magnitude 7.5 and 8.0 this summer.

Image below was taken on April 2 by Chris Schur.

C/2017 E4 (Lovejoy) [Perihelion on 2017 April 23 at 0.49 au]

The latest Comet Lovejoy was discovered by Australian amateur Terry Lovejoy with a CCD-equipped 14″ SCT f/1.9 Hyperstar system. The first magnitude estimates placed it near magnitude 12 but the comet rapidly brightened and is now around magnitude 6.5. As April starts, C/Lovejoy is located 0.72 au from the Sun and 0.61 au from Earth. At perihelion on April 23, it will be 0.49 and 1.10 au from the Sun and Earth. The comet could brighten by an additional magnitude or two by then. Lovejoy will become more difficult to observe as the month progresses as its elongation from the Sun shrinks from 45 deg to 20 deg. The comet will remain a morning object all month as it moves through Pegasus (Apr 1-12), Andromeda (12-27) and Triangulum (27-30).

Image below was taken on April 5 by Gianluca Masi and Michael Schwartz.

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

- Carl Hergenrother (ALPO Comet Section Coordinator)

ALPO COMET NEWS FOR Mar 2017

2017-March-1

This month visual observers will be able to follow four bright comets (five, if you include 2P/Encke though it may already be too close to the Sun for most observers as the month begins). Comet 45P/Honda-Mrkos-Pajdusakova is rapidly fading after passing 0.08 au from Earth last month. 41P/Tuttle-Giacobini-Kresak takes its turn passing close to the Earth (0.14 au) on April 1 and may reach 6th magnitude by the end of March. Two long-period comets should also become brighter than 10th magnitude [C/2015 ER61 (PANSTARRS) and C/2015 V2 (Johnson)].

Last month the Comet Section received comet magnitude estimates for comets 2P/Encke, 41P/Tuttle-Giacobini-Kresak and 45P/Honda-Mrkos-Pajdusakova from Salvador Aguirre and Carl Hergenrother. CCD images were also received for comets 2P/Encke, 41P/Tuttle-Giacobini-Kresak, 45P/Honda-Mrkos-Pajdusakova and C/2015 V2 (Johnson) from Richard Owens, Efrain Morales Rivera and John D. Sabia.

Evening Comets

2P/Encke [Perihelion on 2017 March 10 at 0.34 au]

If you live in the northern hemisphere and haven’t see Encke yet this apparition, the clock is ticking. On March 1, Encke will be a 7th-8th magnitude object located low in the western evening sky at an elongation of only 24 degrees. The comet rapidly drops closer to the Sun and will be invisible only a few days into March. A second opportunity to see Encke will occur between March 9 and 14 via our computers as the comet will be within the field-of-view of the LASCO C3 instrument on the SOHO spacecraft. Observers south of the equator will be able to observe Encke towards the end of the month as it reappears in the morning sky at 8th magnitude. The comet starts the month at a heliocentric distance of 0.41 au. Perihelion occurs on March 10 at 0.34 au. By the end of the month it will be at 0.64 au from the Sun. Its distance from Earth drops from 0.81 au on the 1st to 0.66 au on the 12th before increasing to 0.91 au at the end of the month. Encke will be traveling through Pisces (Mar 1-10) and Aquarius (11-31).

45P/Honda-Mrkos-Pajdusakova [Perihelion on 2016 December 31 at 0.53 au]

Comet 45P/Honda-Mrkos-Pajdusakova is rapidly fading after its close approach to Earth (0.08 au) on Feb 11. Though it was a small condensed object with a long gas tail prior to perihelion, it became a large, low surface brightness object post-perihelion. As is often the case with such objects, observing conditions and the equipment used can greatly affect the view. The comet can easily be missed if the sky was too bright or too high of a magnification was used. As a result, the comet was considered a disappointment by some. Salvador Aguirre and Carl Hergenrother were able to observe the comet in 7×50 and 10×50 binoculars at around magnitude 6.5 a few days prior to close approach. In my 10×50s the coma was over a half degree in diameter. Unfortunately the date of close approach and the days after were compromised by a nearly Full Moon. By the time the Moon was out of the sky, 45P had faded to magnitude 7.6. This month the comet starts at 9th magnitude but continues fading to 13th by the end of March as it moves through Leo (Mar 1-2, 6-9, 13-31) and Leo Minor (2-6, 8-13). Its distances from the Sun and Earth increase from 1.23 to 1.64 au and from 0.25 to 0.74 au, respectively.

41P/Tuttle-Giacobini-Kresak [Perihelion on 2017 Apr 12 at 1.05 au]

Comet 41P/Tuttle-Giacobini-Kresak will also make an impressive close approach to Earth. Though it won’t come as close as 45P did back in February, 41P is an intrinsically brighter comet and will appear brighter in apparent magnitude. Still, 41P may be more difficult to see than its brightness suggests to those observing under less than dark skies. The comet starts the month around magnitude 9.6 and will brighten to magnitude 8.3 on 3/11, 7.2 on 3/21, and 6.5 on 3/31. Closest approach occurs on April 1 at 0.14 au. This is nearly the closest this comet can come to Earth on its current orbit and it won’t pass this close again till 2066.

T-G-K is outburst prone and experienced two 10-magnitude outbursts in 1973. Smaller outbursts also occurred in 1995 and 2001. If T-G-K were to experience an outburst during this return it could become a naked eye object. During March, T-G-K moves from 1.19 to 1.06 au from the Sun and 0.22 to 0.14 au from Earth. It will be located in Leo (Mar 1-5), Leo Minor (5-12), Ursa Major (12-29), Draco (29-31) as its elongation drops from 155 to 110 degrees in the evening sky.

Morning Comets

C/2015 V2 (Johnson) [Perihelion on 2017 June 12 at 1.64 au]

Comet Johnson is inbound with a perihelion of 1.64 au and close approach to Earth at 0.81 au this summer. It is well placed for northern observers through perihelion. Its rate of brightening has been slow so this month it is only expected to brighten from magnitude 10.4 to 9.6. During March, it is a morning object in Hercules (Mar 1-31) at an elongation that increases from 101 to 108 degrees. It starts the month 2.13 au from the Sun and 1.70 au from Earth. At the end of the month, these values decrease to 1.90 au from the Sun and 1.34 au from Earth.

C/2015 ER61 (PANSTARRS) [Perihelion on 2017 May 9 at 1.04 au]

C/2015 ER61 (PANSTARRS) will reach perihelion on May 9 at 1.04 au from the Sun but never gets closer to Earth than 1.18 au. As a result, ER61 may only brighten to 8th magnitude at is brightest in May. For northern observers, it will be located low in the morning sky. It will be better placed for southern observers. This month its distance from the Sun increases from 1.54 au to 1.23 au. Its geocentric distance grows from 1.58 to 1.23 au as it travels through Sagittarius (Mar 1-27) and Capricornus (27-31). It is currently 10-11th magnitude and may brighten to 9th magnitude by the end of the month though its rate of brightening also appears to be rather slow.

73P/Schwassmann-Wachmann 3 [Perihelion on 2017 March 16 at 0.97 au]

A newly discovered component of the split comet 73P/Schwassmann-Wachmann 3 was observed in outburst during February. Component 73P-BT is currently 11-12th magnitude and located within arc minutes of the primary component 73P-C (a little fainter at 13th magnitude). CCD imagers and large aperture visual observers are asked to monitor this comet for additional outbursts or splitting events. The comet is located low in the eastern morning sky and will only get lower as the month progresses. 73P has a long history of splitting events following an initial split in 1995. Though hundreds to thousands of components were observed during its close flyby of Earth in 2006, components C and BT are the only two known to be currently active.

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

- Carl Hergenrother (ALPO Comet Section Coordinator)

ALPO COMET NEWS FOR FEB 2017

2017-February-11

Sorry for the late update. The big story this month is the extreme close approach of comet 45P/Honda-Mrkos-Pajdusakova to Earth on February 11 at 0.08 au. A few other comets, including frequent visitor 2P/Encke, will be visible in small telescopes.

Evening Comets

2P/Encke [Perihelion on 2017 March 10 at 0.34 au]

Comet Encke is making its 63rd observed apparition since it was first seen in 1786. Encke will become a visual object this February as it brightens from 10th to 7th magnitude in Pisces. Its elongation drops from 46 to 24 degrees. as its distance from the Sun decreases from 0.91 to 0.42 au and geocentric distance decreases from 1.27 to 0.81 au.

41P/Tuttle-Giacobini-Kresak [Perihelion on 2017 Apr 12 at 1.05 au]

This comet was discovered on three separate occasions: in 1858 by Horace Tuttle, 1907 by Michel Giacobini and 1951 by Lubor Kresak. 2017 marks 41P’s 11th observed apparition. Nominally 41P should become 6th magnitude by late March. I say nominally because this comet is prone to outbursts. In 1973, T-G-K experienced two 10-magnitude outbursts. Smaller outbursts also occurred in 1995 and 2001. If T-G-K were to experience an outburst during this return it could become a naked eye object. Perihelion is on April 13 at 1.05 au and close approach to Earth is on March 27 at 0.14 au. During February, T-G-K will brighten from 13th to 9th magnitude as it moves from 1.40 to 1.19 au from the Sun and 0.42 to 0.22 au from Earth. It will be located in Leo near opposition all month.

Morning Comets

45P/Honda-Mrkos-Pajdusakova [Perihelion on 2016 December 31 at 0.53 au]

Comet 45P/H-M-P brightened up to 6th magnitude before it was lost in the glow of dusk in early January. At that time is was highly condensed and displayed a hint of bluish-green in my 30×125 binoculars. The comet is currently racing higher into the eastern sky at dawn. Salvador Aguirre spotted it on Feb 10 at magnitude 6.5. A night earlier, I spotted it in 10×50s as a large diffuse glow over 1/2 degree across. Its appearance was very similar to that of 252P/LINEAR which made a close approach last year. Unfortunately, the best for this comet is probably over as large, diffuse, low surface brightness objects usually don’t fare well against a bright Moon. The comet will still be visible to small telescope and binocular observers throughout the month but will be fading (probably no brighter than 9th magnitude by the end of the month). This month, its heliocentric distance increases from 0.83 to 1.23 au while its geocentric distance initially decreases from 0.16 au to February 11’s close approach at 0.08 au and back to 0.25 au as it moves through Aquila (Feb 1-7), Hercules (7-11), Corona Borealis (11-13), Bootes (13-15), Canes Venatici (15-20), Coma Berenices (20-21), Ursa Major (21-25) and Leo (25-28). Elongation climbs from a still too low 17 degrees on the 1st to 45 deg on the 7th, 90 deg on the 12th, and a close to opposition 159 deg at the end of the month.

C/2015 ER61 (PANSTARRS) [Perihelion on 2017 May 9 at 1.04 au]

C/2015 ER61 (PANSTARRS) will reach perihelion on May 9 at 1.04 au from the Sun but never gets closer to Earth than 1.18 au. As a result, ER61 may only brighten to 8th magnitude at is brightest in May. For northern observers, it will be located low in the morning sky. It will be better placed for southern observers. This month its distance from the Sun increases from 1.86 au to 1.54 au. Its geocentric distance grows from 2.08 to 1.58 au as it travels through Ophiuchus (Feb 1-23) and Sagittarius (23-28). It is currently 10-11th magnitude and may brighten to 9th magnitude by the end of the month.

C/2015 V2 (Johnson) [Perihelion on 2017 June 12 at 1.64 au]

Comet Johnson is inbound with a perihelion of 1.64 au and close approach to Earth at 0.81 au this summer. It is well placed for northern observers through perihelion. Now is a good time for CCD imagers and large aperture visual observers to watch C/Johnson brighten from its current 10th magnitude to a peak of 6-7th magnitude. This month, it is a morning object in Bootes (Feb 1-9) and Hercules (9-28) at an elongation that increases from 96 to 101 degrees. It starts the month 2.36 au from the Sun and 2.05 au from Earth. At the end of the month, these values decrease to 2.13 au from the Sun and 1.70 au from Earth.

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

- Carl Hergenrother (ALPO Comet Section Coordinator)

ALPO COMET NEWS FOR JAN 2017

2017-January-1

Happy New Year! 2017 promises to be a busy year for comet observers as no less than 7 comets are predicted to become brighter than 10th magnitude: 2P/Encke, 41P/Tuttle-Giacobini-Kresak, 45P/Honda-Mrkos-Pajdusakova, 96P/Machholz, C/2015 ER61 (PANSTARRS), C/2015 V2 (Johnson), C/2016 U1 (NEOWISE). Of course there are the comets yet to be discovered as well as the dozens of fainter comets within reach of CCDs.

The last month of 2016 was a productive one for the ALPO Comet Section. CCD imagers continued to monitor a number of comets, both bright and faint, while visual observations were reported for the month’s two brightest comets. While January will see a slow down in visual observations as we lose our two bright comets to the glare of the Sun, the action will pick up again in February.

During December, CCD observers Denis Buczynski, Carl Hergenrother, Efrain Rivera Morales, Richard Owens and John D. Sabia contributed images of the following comets: 2P/Encke, 41P/Tuttle-Giacobini-Kresak, 43P/Wolf-Harrington, 45P/Honda-Mrkos-Pajdusakova, 56P/Slaughter-Burnham, 74P/Smirnova-Cherynkh, 93P/Lovas, 174P/Echeclus, 226P/Pigott-LINEAR-Kowalski, 315P/LONEOS, C/2010 U3 (Boattini), C/2013 US10 (Catalina), C/2015 VL62 (Lemmon-Yeung-PANSTARRS), C/2015 V2 (Johnson), C/2015 X7 (ATLAS), C/2016 N4 (MASTER), and C/2016 T2 (Matheny). Visual comet magnitude estimates were submitted by Carl Hergenrother, John D. Sabia and Willian Souza for 45P/Honda-Mrkos-Pajdusakova and C/2016 U1 (NEOWISE).

The effort to digitize the archives of the Comet Section and place them online continues. Currently the Section Gallery contains over 2300 images and drawings of 215 different comets.

Evening Comets

45P/Honda-Mrkos-Pajdusakova [Perihelion on 2016 December 31 at 0.53 au]

Comet 45P/H-M-P has been brightening as predicted with visual observers placing it at magnitude 7.2-7.3 at the end of December. After passing perihelion on New Year’s Eve, its orbit will carry 45P between the Sun and Earth. As a result, we will lose sight of the comet during the first week of January. Not to worry, the best is yet to come as 45P will become an easily observable object (up to 6th-7th magnitude) in the morning sky starting in early February as it passes within 0.08 au of Earth. This month, its heliocentric distance increases from 0.53 to 0.84 au while its geocentric distance crashes from 0.68 to 0.16 au as it moves through Capricornus (Jan 1-15) and Aquarius (15-31) in the evening sky.

The image below was taken by Richard Owens on December 27.

2P/Encke [Perihelion on 2017 March 10 at 0.34 au]

Comet Encke is back again and making its 63rd observed apparition since it was first seen in 1786. Encke will become a visual object this February as it brightens to 7th magnitude. This month, the comet rapidly brightens from ~13th to 10th magnitude. The Section asks that CCD imagers monitor Encke as it approaches perihelion. Note, that Encke’s appearance depends on what filter is used. The comet may still appear asteroidal in the red while a large gas coma is already detectable in the blue. This month Encke is an evening object moving through Pisces as its elongation drops from 97 to 68 degrees. Its distance from the Sun decreases from 1.39 to 0.91 au while its geocentric distance decreases from 1.42 to 1.26 au.

Morning Comets

C/2015 V2 (Johnson) [Perihelion on 2017 June 12 at 1.64 au]

Jess Johnson of the Catalina Sky Survey discovered this long period comet on November 3, 2015 with the 0.68-m Catalina Schmidt. The comet is inbound with a perihelion of 1.64 au and close approach to Earth at 0.81 au this summer. It is well placed for northern observers through perihelion. Now is a good time for CCD imagers and large aperture visual observers to watch C/Johnson brighten from its current 12th magnitude to a peak of 6-7th magnitude. This month, it is a morning object in Bootes at an elongation that increases from 89 to 96 degrees. It starts the month 2.64 au from the Sun and 2.47 au from Earth. At the end of the month, these values decrease to 2.36 au from the Sun and 2.05 au from Earth.

C/2016 U1 (NEOWISE) [Perihelion on 2017 January 14 at 0.32 au]

Comet NEOWISE is a surprise comet. Only 19th magnitude when discovered in late October, the comet rapidly brightened and was approaching magnitude 8.0 at the end of December. The comet will be lost to most observers during the first week of the month as it moves too close to the Sun. At that time it may be as bright as 7th magnitude. Southern hemisphere observers may be able to pick the comet up again in February though it may already be too faint for visual observation. Northern observers won’t get another shot at NEOWISE till August when it may be too faint even for CCD imagers. This month its distance from the Sun drops from 0.49 au to a perihelion on January 14 of 0.32 au. The distance grows to 0.61 au at the end of the month. Its geocentric distance grows from 0.89 to 1.48 au. Though mostly unseen, C/NEOWISE will travel through Ophiuchus (Jan 1-7), Serpens (7-10), Scutum (10-11), Sagittarius (11-26) and Microscopium (26-31).

New Discoveries

Only one comet discovery was reported in the past month. Yet another interesting asteroid on a very cometary orbit was announced.

C/2016 X1 (Lemmon) is a long-period comet with a large perihelion distance of 7.6 au. It was found by G. J. Leonard with the Mount Lemmon 1.5-m reflector. Even though perihelion will not occur till May of 2019, the comet shouldn’t get much brighter than its current 20th magnitude.

Last month we reported on 2016 VY17, an apparently asteroidal object on a Halley-type orbit. A similar object has been recently announced. 2016 VZ18 is on a long-period comet orbit with a period of ~2700 years. Perihelion will occur in early March at 0.91 au. in early April it will approach to within 0.53 au of Earth. If it remains inactive, VZ18 will not get any brighter than magnitude 20. If it does ‘turn on’, it could become much brighter. CCD observers are encouraged to monitor this object and send your images and photometry to the Comet Section. Who knows, maybe you will be the first to notice VZ18 as an active comet.

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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