BAA Comet Section : Comets discovered in 2007

Updated 2016 March 9

The equations for the light curves of comets that are currently visible use only the raw observations and should give a reasonable prediction for the current brightness. If the comet has not yet been observed or has gone from view a correction for aperture is included, so that telescopic observers should expect the comet to be fainter than given by the equation. The correction is about 0.033 per centimetre. Values for the r parameter given in square brackets [ ] are assumed. The form of the light curve is either the standard m = H0 + 5 log d + K0 log r or the linear brightening m = H0 + 5 log d + L0 abs(t - T + D0) where T is the date of perihelion, t the present and D0 an offset, if L0 is +ve the comet brightens towards perihelion and if D0 is +ve the comet is brightest prior to perihelion.

Observations of new comets are given in ICQ format. More recent ones may be available in TA format from the main page.

Full details of recently discovered objects will not appear until they are available on the CBAT web pages, which is usually a fortnight after the publication of the IAUC.

For further information on the discovery of these objects see this year's SOHO discoveries.

K. Battams has suggested the identity of the Marsden-group comet C/2007 Y4 with C/2002 R4 (cf. MPEC 2002-S35). The following linkage (all the observations having been made with the C2 coronagraph), by Marsden, yields for the previous perihelion passage T = 1997 May 15.2 and an approach within 0.063 AU of the earth on 1997 June 14.7. [MPEC 2008-B49, 2008 January 25]

Karl Battams has put together a probable family tree for the fragments.

For further information on the discovery of this object see this year's SOHO discoveries.

Following recovery in 2007 the orbit was refined to give perihelion distance at 1.06 AU on 2007 September 1.7 and a period of 5.85 years. It can pass 0.07 AU from the Earth and 0.1 AU from Jupiter.

Brian Marsden notes on MPEC 2007-V49 [2007 November 6] that

The "original" and "future" barycentric values of 1/a are +0.001709 and +0.001792 (+/- 0.000005) AU^-1, respectively.

Maik Meyer found some prediscovery observations in archive imagery from 1996 and 1975, which should lead to numbering of the comet.

I managed to find this comet in three DSS images after playing around with orbits and finding the anchor point with the 1996 images. It should be visible in a plate of 1995, but was not seen. Also I could not find it in some NEAT images. In the 1975 images the comet is quite bright, probably due to the slow motion. The appearance is almost the same in the two different plates, although at a different position. I have taken the position of the center of the short trail. The 1996 image is involved with a star. Here I could only measure the end of the trail.

Seiichi Yoshida notes that:

The perihelion distance is large at 4.3 A.U., and the orbit is almost circular with an eccentricity of 0.12. Kenji Muraoka's calculation revealed that this orbit does not change significantly for 200 years in the 20th and 21st centuries.

It reaches 17.5 mag at best based on the brightness at the discovery in 2007 January. The brightness in 1996 February was similar, however, the comet was unexpectedly bright at 15.5 mag in 1975 May and June. It seems to have been a temporary outburst, as the comet returned to its normal brightness in 1977 July at 18 mag.

This comet is similar to 111P/Helin-Roman-Crockett; large perihelion distance, almost circular orbit, and a record of unexpected brightening in temporary outburst.

Brian Marsden notes on MPEC 2007-W67 [2007 November 26] that

The "original" and "future" barycentric values of 1/a are +0.000054 and +0.000749 (+/- 0.000004) AU^-1, respectively.

Brian Marsden notes on MPEC 2007-X37 [2007 December 7] that

The "original" and "future" barycentric values of 1/a are +0.001307 and +0.001402 (+/- 0.000009) AU^-1, respectively.

Gareth Williams notes on the MPEC that

2007 DU112 has a Saturn MOID of 0.30 AU. There were no encounters to within 1 AU between 2007 DU112 and Saturn between 1700 and 2179.

Calculations by Hirohisa Sato showed that if it moved in a long period elipse, the period must be greater than 200 years. The latest orbit gives an eccentricity of 0.98 and a period of over 500 years.

Brian Marsden notes on MPEC 2007-K74 [2007 May 31] that

The "original" and "future" barycentric values of 1/a are +0.015359 and +0.016098 (+/- 0.000087) AU^-1, respectively.

6 observations received so far suggest a preliminary light curve of m = 8.6 + 5 log d + [15] log r

Observations in ICQ format, last observation 2007 April 14, updated 2007 April 16.

Terry provided this information to the comet mail list:

I use 2 Digital SLR cameras to image the sky, and then process the images using IRIS then examine them using the blink technique on a computer monitor. After a very intense search effort in 2006 without success (one near miss with 2006M4), I had wound back my efforts in 2007 (partly because of 2006P1 and partly because of fatigue!). March 15 was only the second time this year I had done any searches in the morning sky. While downloading images from the camera on March 15 I noticed a cometary object at the edge of 16 raw images centred at RA 20h57m DEC -51d 18m made between 17h22m and 17h46m UT. Normally, the raw unprocessed images show only the brightest objects so I was very suprised that this could be an undiscovered comet. At first I though it was simply a bright deep sky object, but after processing the the intense telltale green hue and generally morphology strongly suggested comet. Additionally, when I blinked the processed images it showed small but clear motion. Astrometry quickly revealed no known object in that location. At this point I was very sure I had something :)

The following day there was an agonising wait for cometrise (about midnight from my location) and I notified a number of people for followup observations. John Drummond being located further east had the first opportunity to see the comet. Sure enough John phoned me to confirm the existence of the comet around 11pm local time. Its the first time I have spoken to John and what a way to introduce yourself! Dan Green contacted me late on March 16 UT to advise me that the comet had been announced, but as per standard procedure the comet would not be named until an orbit was calculated and it was determined the comet was not an existing named one.

All told I estimate I have examined about 1000 image fields since late 2004, which would equate to about 1000 hours (it takes me 10 minutes to actually examine an image, but there are other time consuming tasks like setup/development/identifying suspect objects, etc). Unfortunately I don't keep records on time taken and images examined.

Rob McNaught informs me that unusually cloudy weather has severly hampered coverage of the Siding Springs survey. Additionally, I also checked SWAN this morning and the last posted image is February 18. Moonlight problably explained why visual observers hadn't got to the comet first.

Here are some of my images of the comet (including the discovery set).

Juan Jose Gonzalez observed it on April 13.2 estimating it at 7.8 in 7x50B.

Brian Marsden notes on MPEC 2007-K75 [2007 May 31] that

The "original" and "future" barycentric values of 1/a are +0.000617 and +0.000816 (+/- 0.000036) AU^-1, respectively.

20 observations received so far suggest a preliminary light curve of m = 8.3 + 5 log d + 16.3 log r

Observations in ICQ format, last observation 2007 April 15, updated 2007 April 16.

Images by Michael Jaeger and Gerald Rehman on September 14 suggest that it was around 11th magnitude, roughly a magnitude brighter than expected, so it is highly likely to reach easy binocular visibility. Within a week a few visual observations were suggesting that it might have brightened to 9.5. Only a few visual observations are available, and these give a relatively faint absolute magnitude, so it may not survive perihelion.

Martin McKenna, observing from Northern Ireland on the evening of October 3 with a 22cm Dobsonian, estimated the comet at around 7.5, noting that it was strongly condensed with a 3' coma. I observed it on October 15.77 with 20x80B, noting a strongly condensed coma and a total magnitude of 6.7.

After perihelion it faded fairly quickly and by mid November was 8th magnitude. The observations are best fitted by a linear light curve, peaking before perihelion.

Brian Marsden notes on MPEC 2007-K76 [2007 May 31] that

The "original" and "future" barycentric values of 1/a are +0.000679 and -0.000184 (+/- 0.000075) AU^-1, respectively.

Non- gravitational parameters A1 = +1.44 +/- 0.17, A2 = +0.5613 +/- 0.0779.

53 observations received so far suggest a preliminary light curve of m = 6.3 + 5 log d + 0.0496 (dT - 11.2)

Brian Marsden notes on MPEC 2007-K77 [2007 May 31] that

The "original" and "future" barycentric values of 1/a are +0.000167 and +0.000086 (+/- 0.000131) AU^-1, respectively.

9 observations received so far suggest a preliminary light curve of m = 2.8 + 5 log d + [15] log r

Observations in ICQ format, last observation 2008 June, updated 2008 July.

Brian Marsden notes on MPEC 2007-K15 [2007 May 18] that further [astrometric] observations of this comet are very desirable.

The comet was numbered following recovery.

Brian Marsden notes on MPEC 2007-O22 [2007 July 19] that

The "original" and "future" barycentric values of 1/a are +0.000104 and +0.000030 (+/- 0.000033) AU^-1, respectively.

Brian Marsden notes on MPEC 2007-O23 [2007 July 19] that

The "original" and "future" barycentric values of 1/a are +0.002530 and +0.002528 (+/- 0.000084) AU^-1, respectively.

Brian Marsden notes on MPEC 2007-N33 [2007 July 13] that further [astrometric] observations of this comet are very desirable.

Brian Marsden notes on MPEC 2008-P18 [2008 August 4] that

The "original" and "future" barycentric values of 1/a are +0.000724 and +0.000575 (+/- 0.000043) AU^-1, respectively.

Brian Marsden notes on MPEC 2007-O24 [2007 July 19] that further [astrometric] observations of this comet are desirable.

This particular comet (designated C/2007K5) was found as a small faint but still rather obvious blue-green haze in my images from the evening of May 26. My initial estimate is mag 13, but I admit I have not attempted more precise photometry and visually the comet could well be brighter. Interestingly the discovery was made during a bright waxing moon and in the evening sky where moderate light pollution prevails. On the evening I had both cameras (a Canon 300D + Canon 350D) mounted the usual way with the 300D pointed towards -18 declination and the 350D pointed towards declination -11. This allows me to image 13 degree wide sweep of sky from west to east. Some 12 individual starfields were covered with both cameras, with 12 subexposures of 90 seconds for each starfield.

The following day, I downloaded the images from my 300D and ran them through the usual automated processing steps (IRIS is used for this). This processing step outputs 2 images per starfield effectively separated by 10 minutes so that moving objects like comets can be identified. By 'blinking' the 2 images one can see objects like asteroids and comets bobbing backwards and forwards. On examining the first image I almost immediately noticed a moving small hazy object with a distinctive blue green colour typical of many comets. I knew I had something for sure, and notified a number of other for confirmation of a possible comet.

Confirmation came on May 28 when both John Drummond and I made followup observations, which were then sent to Dan Green at CBAT. Further followup was obtained on May 29 by Rob McNaught before an official circular (IAUC 8840) announced the new comet as C/2007 K5. Interesting, C/2007 K5 required less than 20 hours of actual searching in contrast to the estimated 1400 hours for C/2007 E2.

The comet itself appears to be quite faint, and will problably remain that way, but a comet none-the-less. Further astrometry is require to calculate an orbit and once this is done the comet will be named.

Brian Marsden notes on MPEC 2007-O25 [2007 July 19] that further [astrometric] observations of this comet are desirable.

Brian Marsden notes on MPEC 2007-P28 [2007 August 10] that

The "original" and "future" barycentric values of 1/a are +0.005141 and +0.005184 (+/- 0.000073) AU^-1, respectively.

Rob notes

This object resulted from southerly winds forcing me to survey in the north, looking in a small area unsurveyed in the last month! Every one is pleasing, but I'm not going to lose sight of the fact that this is a team effort using some great software (in recent years largely down to Ed Beshore and Eric Christensen). Steve Larson's group, as with some others, have all been enthusuiasts, committed to the project and discovery. Thus the naming policy adopted within the group; the observer/discoverer gets a personal credit in the naming. Having a survey name by default would certainly take much of the shine off the discovery process for me, and I think for most people it is both an incentive and a motivation.

Our current funding will go thru to the end of 2008, but after that there is no guarantee of funding for the project in general or the Uppsala telescope. Any possible new project might involve a different telescope, different location, different people and different naming policy. Still, I've had a great innings and a few more before the end of next year would be most pleasing!

Brian Marsden notes on MPEC 2007-Q24 [2007 August 26] that

The "original" and "future" barycentric values of 1/a are +0.000352 and +0.000381 (+/- 0.000205) AU^-1, respectively.

Brian Marsden notes on MPEC 2007-W68 [2007 November 26] that

The "original" and "future" barycentric values of 1/a are +0.000603 and +0.000979 (+/- 0.000036) AU^-1, respectively.

Orbit computations by Hirohisa Sato suggested a long period ellipse with a period of around 1000 years and this was confirmed by further observations.

Brian Marsden notes on MPEC 2007-Q25 [2007 August 26] that

The "original" and "future" barycentric values of 1/a are +0.006249 and +0.006082 (+/- 0.000047) AU^-1, respectively.

Images from August and November 2000 were found in archival LONEOS and NEAT observations by Syuichi Nakano in early September and it was given the designation 2000 P3 for this return. Following publication of the identification on MPEC 2007-R04 further images from September and December 2000 were found in the NEAT archives by Maik Meyer and Reinder Bouma.

Quanzhi Ye has also discovered a number of SOHO comets. This is the first discovery of a comet from Taiwan and the observatory is a non- professional one. The Lulin Sky Survey is a co-operative project between China and Taiwan.

The comet emerged from conjunction for near equatorial observers around December 15 and rapidly moved into the morning sky. By Christmas it was visible to observers between 50 N and 40 S. The comet became visible to UK observers in early 2009, and was a naked eye object in 2009 February. It will remain visible until early May.

The comet passed through the SOHO C3 field between November 17 and December 4. It should have been around 7th magnitude to visual observers, but was clearly fainter than this. However Michael Mattiazzo did locate the 9th magnitude nuclear condensation in C3 images from December 1. On observation by Juan Jose Gonzalez Suarez on December 21.3 made it 7.6 in 25x100B, rather fainter than expected from the pre conjunction light curve.

Michael Mattiazzo points out:

We are observing comet 2007 N3 (Lulin) "edge-on". The orbital inclination of the comet is 178 degrees. i.e. virtually in the same orbital plane as the Earth. This means from Earth's perspective, we will observe the comet edge-on throughout the apparition! The effect of this is to enhance the surface brightness of the comet and its dust tail. Take the deep sky example of an edge-on galaxy being more readily observable than one that is face-on.

Recently posted images are displaying the sharp sunward pointing dust tail (antitail) in PA 100, along with the ion tail at PA 280. The dust tail should remain at approximately PA 100 to 110 and appear as a sharply defined "needle-like" appendage. Since most of the dust particles are released in the comets wake, the dust tail will rapidly lengthen after Lulin's flyby of the Earth on Feb 24, length uncertain but perhaps a few degrees long. The ion tail however will appear considerably shortened, since it will be pointing directly away from the Sun when the comet is located at opposition on Feb 26.

In the period 2009 February 24 - March 4, C/2007 N3 (Lulin) reaches a near backward scattering geometry (phase angle < 10 degrees, with a minimum of 0.1 degrees (!) on Feb. 26.3). Using a linear phase coefficient of beta = 0.02, a maximum brightening of about 0.6 magnitudes on Feb. 26 is possible. In a moonless dark sky, there are good opportunities for photometric measurements. The so-called opposition effect, mainly observed between scatter angle 173 and 180 degrees at moon and asteroids, is unlikely.

Brian Marsden notes on MPEC 2008-E12 [2008 March 3] that

The "original" and "future" barycentric values of 1/a are +0.000019 and +0.000813 (+/- 0.000008) AU^-1, respectively.

178 observations received so far suggest a preliminary corrected light curve of m = 5.6 + 5 log d + 8.2 log r

Observations in ICQ format, last observation 2009 March, updated 2009 March.

Brian Marsden notes on MPEC 2007-Q20 [2007 August 24] that further [astrometric] observations of this comet are very desirable.

Brian Marsden notes on MPEC 2007-S20 [2007 September 19] that further [astrometric] observations of this comet are very desirable.

Rodney Austin commments on the comet mailing list:

As a little bit of an aside to this discovery. This is second official discovery of a comet from Mt John, not counting the independent discovery by Alan Thomas of Comet Barbon in 1966; (a miscommunication between Mt John and the Carter Observatory in Wellington saw Alan miss out on getting co-credit).

The first official discovery was by Mike Clark (P/Clark) in 1973. At that time I was working at Mt John myself, and was off duty that evening - comethunting (!) only about 100 metres away from the building where Mike was busy taking plates for the Bamburg Observatory patrol. He found the comet on inspecting his plates the following day. He started looking VERY closely at his plates after just missing the discovery of the SN in NGC 5253 the previous year.

I have been in touch with Alan Gilmore who says that he was as surprised as everyone else over this one.

Brian Marsden notes on MPEC 2007-U59 [2007 October 23] that

The "original" and "future" barycentric values of 1/a are +0.000309 and +0.000412 (+/- 0.000152) AU^-1, respectively.

28 observations received so far suggest a preliminary corrected light curve of m = 2.0 + 5 log d + 13.2 log r

Brian Marsden notes on MPEC 2007-V52 [2007 November 6] that further [astrometric] observations of this comet are desirable.

The orbit is from C2 observations only. The current C3 observations increasingly deviate to more than 0.5 arcmin west and almost 1 arcmin north of the computed position by the end of the sequence.

One reason being given for the failure to number the object is that it may not be a comet, despite its cometary designation. Demonstrating that the light curve is non-asteroidal may be one solution, or clear evidence of a coma or tail would certainly confirm it.

According to the linked orbit by S. Nakano the comet will approach Earth in 2035 at 0.27 AU, in 2038 at 0.19 AU and in 2043 at 0.30 AU.

Brian Marsden notes on MPEC 2007-V52 [2007 November 6] that further [astrometric] observations of this comet are desirable.

Independent orbit computations by Hirohisa Sato and Kenji Muraoka suggest an orbital period of around 60 years, with perihelion at 5.7 AU in summer 2008. This was confirmed, with the latest orbit giving a period of around 44 years and perihelion at 5.5 AU in September 2008.

44 observations received so far suggest a preliminary light curve of m = 7.4 + 5 log d + 13.4 log r

Brian Marsden notes on MPEC 2008-E09 [2008 March 1] that

The "original" and "future" barycentric values of 1/a are +0.000627 and +0.000476 (+/- 0.000004) AU^-1, respectively.

Brian Marsden notes on MPEC 2007-Y06 [2007 December 17] that further [astrometric] observations of this comet are desirable.

Dimitry Chestnov suggests

I think that P/2007 T2 (Kowalski) = D/1770 L1 (Lexell). They both have almost the same orbital elements (at the observed epoches) and both orbits are unstable. Tisserand parameters TJ of these comets are very close. I know that some comets, that frequently approach Jupiter, tend to jump between two distinct orbits several times.

As we know, D/1770 L1 (Lexell) was thrown out from its orbit by Jupiter in 1779 to a distant, even probably a hyperbolic, orbit (too high uncertainty for quantitative estimate). In 2004, P/2007 T2 was injected by Jupiter from a distant orbit to its present orbit, that resembles orbit of D/1770 L1.

Using EXORB software, I generated 1000 "Monte-Carlo" clones of P/2007 T2 and went back in time in tens of years ago in SOLEX. Some of the clones came from time to time to orbits similar to D/1770 L1.

K. Kinoshita's web site (http://jcometobs.web.fc2.com/pcmt/k07t2.htm) indicates that P/2007 T2 passed 0.0195 AU from Jupiter on 2004 September 29 and that the orbital period was altered from 9.8 years to 5.4 years. Prior to that date, there were no significant close encounters back to the 1893 apparition (the earliest date the comet's orbit is integrated to), when the period was about 9.2 years.

These details are important because of the examinations of the orbital motion of D/1770 L1 (Lexell) after its last close encounter with Jupiter (0.0015-0.0016 AU) in 1779. In 1976, E. I. Kazimirchak-Polonskaya and S. D. Shaporev concluded that the comet was probably placed into an orbit with a period of 260 years, although a much longer period was not out of the question. In 2003, Kinoshita found that the comet was ejected into an orbit with a period of about 200 years. Kinoshita also indicated the perihelion distance was likely increased to 5.2 AU by the 1779 encounter. From both of these sets of calculations, it is probably safe to say that comet Lexell would not have returned to the sun's vicinity before 1984, if not much later.

Kazuo Kinoshita's calculations reveal that the orbital elements of this comet have not changed much since 1939.

It was discovered about two months after the perihelion passage in 1990. That was probably because it had been located in the southern sky until that time.

Maybe this comet tends to be brightest after perihelion passage. If so, the comet may brighten rapidly after this, and may reach 14.5 mag in February.

However, it was not discovered in September or October in 1990 when it must have been observable and bright. So maybe a temporary outburst occured in 1990 November.

Brian Marsden notes on MPEC 2008-A27 [2008 January 7] that further [astrometric] observations of this comet are desirable.

Brian Marsden notes on MPEC 2007-Y07 [2007 December 17] that

The "original" and "future" barycentric values of 1/a are +0.021240 and +0.021733 (+/- 0.000001) AU^-1, respectively.

Brian Marsden notes on MPEC 2007-Y08 [2007 December 17] that further [astrometric] observations of this comet are desirable.

Brian Marsden notes on MPEC 2008-P51 [2008 August 11] that

The "original" and "future" barycentric values of 1/a are +0.000168 and +0.000065 (+/- 0.000003) AU^-1, respectively.

Brian Marsden notes on MPEC 2007-X46 [2007 December 10] that further [astrometric] observations of this comet are desirable.

Brian Marsden notes on MPEC 2008-Q26 [2008 August 25] that

The "original" and "future" barycentric values of 1/a are +0.000066 and +0.000093 (+/- 0.000007) AU^-1, respectively.

Additional observations of the comet as asteroid 2007 WM63 were published in 2010.

The comet brightened rapidly and came within general visual range in early March 2008. It reached binocular visibility in late April, but few UK observations were made as the comet was rather far south, and very diffuse. Southern Hemisphere observers had a better view, and were able to view it through perihelion. The brightening seemed to slow down during May, with many observers reporting it at around 6th magnitude, for example Alexandre Amorim reporting it at 5.9 in 10x50B on May 24.92. It peaked at around 5th magnitude near the time of perihelion in late June.

It moved into view from the UK after perihelion and was imaged on July 25 by Peter Carson, from Leigh on Sea, Essex. It was visible as a weakly condensed binocular object in August. It had faded to around 10th magnitude by early September and had become quite diffuse, but then went into a steep decline, with CCD observations suggesting that it was 18th magnitude by late October.

Cedric Bemer points out the possibility of a meteor shower from the comet. The miss distance for the orbits is 0.0178 AU and the earth passed this point 27.5 days later. Maximum was likely on August 21.9 or 27.6, with a radiant of 168 -14.

Brian Marsden notes on MPEC 2008-E10[2008 March 1] that

The "original" and "future" barycentric values of 1/a are -0.000002 and +0.000631 (+/- 0.000012) AU^-1, respectively.

171 observations received so far suggest a preliminary light curve of m = 8.6 + 5 log d + 9.6 log r.

It is an intrinsically faint comet and may not get within visual range.

Brian Marsden notes on MPEC 2008-B23 [2008 January 21] that

The "original" and "future" barycentric values of 1/a are +0.000146 and +0.000542 (+/- 0.000052) AU^-1, respectively.

Brian Marsden notes on MPEC 2008-E13 [2008 March 3] that

The "original" and "future" barycentric values of 1/a are +0.000141 and +0.000391 (+/- 0.000071) AU^-1, respectively.

Brian Marsden notes on MPEC 2008-E14 [2008 March 3] that

The "original" and "future" barycentric values of 1/a are +0.001295 and +0.001272 (+/- 0.000063) AU^-1, respectively.