Tuesday 5 December 2006

2006 November notes: 2006 WV

November ended up providing the most observing time at Great Shefford since Nov 2005, 105 hours over 16 nights.

The NEO highlight of the month was 2006 WV, discovered on Nov 17th with the 0.68-m Schmidt at Catalina. At 20th mag and moving at a moderate 2"/min at discovery it was added to the NEO confirmation page and was searched for on the evening of Nov 18, but not found. Unusually it was outside the uncertainty area predicted by the Minor Planet Center, reason being that it had unusual motion because it was headed almost directly for us and was accelerating rapidly towards a very close encounter at 10am on 21 Nov, within the orbit of the Moon.

LINEAR and the Mt. Lemmon telescope of the Catalina Survey picked it up again less than 24 hours later and it was observed from Great Shefford on Nov 19.0 UT, moving at 6"/min and at mag +19. The next night was cloudy, but by 9pm on 20th Nov it had brightened up to mag +16.5 and was racing along at 150"/min! By this time it was about double the distance of the moon and closing fast. It was followed on and off all night, finally lost to the morning twilight at 6:47am on 21 Nov with the Sun just 7 degrees below the horizon, by which time it was moving at 414"/min (or the apparent diameter of the moon in about 4 minutes), mag +15 and just at the point of crossing inside the moons orbit. Although not reported again, closest approach was 3 hours later at a distance of 349,900 Km (0.91 Lunar distances).

Monday 6 November 2006

2006 October notes: 2006 RZ and 2006 TA8

The month started off with Apollo 2006 RZ (mentioned last month) passing close by the Earth on Oct 6/7. It was tracked on the 6th until about 20:15UT, moving at 86"/min at 15th mag. those positions being the last reported of the object. However, it was picked up again 4.5 hours later, through a gap in the trees, just 10 degrees above the north horizon, moving very obviously between frames. By then it was at the unusually large phase angle of 119 degrees, but unfortunately there were too few comparison stars visible in the images to measure positions.

A number of good nights during October were used to go for some very faint NEOs, an increasing number of which are being put on the NEOCP, mainly by the Catalina and Spacewatch surveys. However, there were also a proportion of bright and often fast moving objects discovered, including 2006 TA8, discovered by LINEAR at high northern declinations on Oct 12 and followed as a 16th mag object on Oct 13, 17 & 22 from Great Shefford, after which it disappeared south in the morning sky.

Thursday 5 October 2006

2006 September notes: 2006 RZ, 2006 SU49 and 2006 SO198

Generally poor weather continued here during September, still, some work was done on 14 nights, but again few long runs on any particular object could be done.

2006 RZ is a relatively rare amateur NEO discovery, having been picked up at 18th mag by H. Michels from Herrenberg on Sep 4th. It was followed from early September through to the end of the month, passing about 5 lunar distances away in the first week of October having brightened to mag 14.

Some other interesting objects were followed, 2006 SU49 being posted as an impact risk at Torino scale 1 for a number of days before being removed after being found on old NEAT and Sloan archive images going back 5 years.

2006 SO198 was discovered by LONEOS on Sep 29 and was confirmed from Great Shefford while on the NEOCP. It was at the 'fast' end of it's uncertainty area, mag 18 and moving at about 3"/min, about 11' away from the prediction. Less than 4 days later it was to make a pass just outside the orbit of the moon. It was last seen the day before at 16th mag moving at 30"/min, but would have been 14th mag and moving at 800"/min at closest, but it would have been only visible from S. Africa-India and was not reported.

Tuesday 5 September 2006

2006 August notes: 2006 ON1, 2006 QV89, 6Q0B44E

Although some work was done on 16 nights in August, many sessions were interrupted by cloud with just a couple of nights judged as good. Most of the NEOs followed were observed on single nights only, the exception being Apollo 2006 ON1 with three nights.

Apollo 2006 QV89 was observed while it was on the NEOCP and is interesting because its minimum orbital intersection distance with the Earth (MOID) is currently given as 0.00001 AU or about 1,000 miles. At the time of writing (Sep 5th) it is listed with a 1 in ~800 chance of collision with Earth in 2019, so just as well it is only about 30 metres in diameter... Further positions in the coming days are desirable.

On Aug 29th positions for 6Q0B44E were obtained, discovered by the Catalina survey the day before and subsequently found to be in an unstable 80 day orbit around the Earth. It is still unclear whether this is an artificial satellite re-captured by the Earth similar to the Apollo 12 S-IVB third stage J002E3 back in 2003 or whether it is a very small (1-5 metre diameter) NEO temporarily captured by Earth. As noted by Bill Gray, with the current data, it looks as if this object probably entered the Earth/Moon system sometime between about 2000 and 2003, though dates as far back as 1991 are quite possible. Paul Chodas (JPL) comments that it will stay in Earth orbit for at least three more years.

Tuesday 1 August 2006

2006 July notes

With the summer monsoon having taken hold in the southern USA, stopping the big surveys from operating for most of the month, time was spent catching some NEOs at their second and subsequent oppositions.

Working with Roger Dymock we also went after some more normal main belt minor planets on the FUAP (Follow Up Astrometric Program) target list at http://asteroidi.uai.it/ which is maintained by Sergio Foglia on behalf of the UAI Minor Planets Section. This site lists minor planets of mag +18.5 or brighter that are in need of observation, whether newly discovered and under-observed, or awaiting recovery at their second or subsequent oppositions.

The last week of the month saw a flurry of NEO discoveries from the surveys in a brief respite from their bad weather, with several objects at mag 16-17.

Wednesday 28 June 2006

2006 June notes: 2006 KZ112 and 2006 MU6

Several objects were followed over a period of a couple of weeks during the month, including 2006 KZ112 which has an interesting 'Encke like' orbit (2006 KZ112: q=0.29, e=0.89, i=38, P=4.0, Encke: q=0.33, e=0.85, i=12, P=3.3).

Of the other objects observed, 2006 MU6 was picked up on June 27 after being discovered by Spacewatch on June 20th and is a possible Mars Trojan (though the uncertainties on the orbital elements are still large). Already very faint it is predicted to fade quickly.

Saturday 3 June 2006

2006 May notes: 2006 JE, 2006 GY2, 2006 HX57, 2006 JV26 and 2006 JF42

May was on the way to being my worst month since Nov 2003 until the unsettled spell finally ended on 27 May and four of the last five nights were clear.

The month had started well with some fast movers - 2006 JE was a LINEAR discovery that I managed to confirm when it was on the NEOCP, about 1/2 degree off track and moving at 94"/min. A much easier target because it was over 4 mags brighter at +14.0 but travelling at about the same speed was 2006 GY2 on May 15.9, just a few hours before it passed 7 lunar distances from Earth and the same time as it was being observed from Arecibo and Goldstone and found to be a binary with components of 400 m and 80 m diameter. 2006 HX57 was observed on May 6.0 at mag 16.5, moving at 92"/min and also 2006 JV26 on May 8.9 at mag 16.5 and moving at 290"/min, less than 3 lunar distances away.

An interesting object discovered on May 11 by the Catalina Sky Survey was 2006 JF42, observed from May 15-31, deep in the glow of evening twilight. It has a very short period of only 201 days (shorter than Venus) but with an eccentric orbit taking it from 0.28 AU at perihelion to 1.06 AU at aphelion, with the most favourable viewing circumstances being when aphelion occurs around May 21, when it would be placed in the opposition region of the sky south of the ecliptic. This year aphelion was only two weeks later but the best elongation achieved was only 96 degrees.

Friday 5 May 2006

2006 April notes: Integral, 2006 GA, 2006 GC, Comet 73P/Schwassmann-Wachmann

April was a much better month than the last few, with 19 usable nights.

The artificial satellite Integral wandered into the field of component 73P-N/Schwassmann-Wachmann on the morning of April 12th, moving at about 230"/min. Not knowing whether it was a close approaching NEO or a very unusual artificial satellite I followed it for 50 minutes until it ran into bright twilight, which was long enough to work out an orbit for it and to pick it up again 2 nights later. Thanks go to Tony Beresford and Mike McCants for identifying it for me.
Artificial Satellite Integral passes through the field of view of faint fragments of comet 73P/Schwassmann-Wachmann

A couple of NEOs were followed for several weeks (2006 GA & 2006 GC) but most were observed for much shorter arcs. A fair proportion of the early mornings during the month were spent imaging over 30 of the components of 73P as it approached the Earth.

Saturday 4 February 2006

2006 January notes: 2006 BA, 2006 BV39, 2006 BF56, 2006 BH99

The first half of January was very poor with just 3 usable nights, but the second half was better with 10 nights and brought some interesting fast movers...

On Jan 20/21st 2006 BA was observed at mag +16.5, passing by at 2 lunar distances (l.d.) and moving at 60"/min.

Then on Jan 26th the Spacewatch 1.8-m reflector discovered 2006 BV39, confirmed 15 hours later from Klet in the Czech Republic. It was about 4 l.d. at discovery and closing fast. In conversation with Monty Robson at 932 (John J. McCarthy Observatory in Connecticut) on the morning of the 27th I mentioned that 2006 BV39 would be an interesting target the next night. Nowhere had reported it to the Minor Planet Center after Klet's confirmation when I tried but failed to find it at midnight on the 28th. On checking with Monty, he mentioned that he had got it the night before but had not reduced the astrometry. He kindly measured the positions immediately and sent them through to me, allowing me to update the ephemeris and then to locate the NEO. It was 23' W of the MPC's prediction and would have been very difficult to find without the correction. By this time it was moving at 210"/min and was just 5,000 miles outside the Moon's orbit. I followed it until 05:14UT on the 29th by which time it had accelerated to 277"/min and had crossed 28,000 miles inside the Moon's orbit with closest approach about 2 hours later at 0.9 l.d. This was the third NEO I have tracked while inside the Moon's orbit in four months!

Just a few hours later news came through of a mag +21 NEO discovered from Mt. Lemmon with the 1.5-m reflector at 7:22UT and followed by them for 5 hours, during which time the apparent speed went from 10"/min to 14"/min. Obviously approaching fast, it was confirmed almost simultaneously from Klet and Great Shefford at about 22:10UT that night and given the designation 2006 BF56 by the Minor Planet Center. By then it was mag +19.5, moving at 48"/min and was about 3 l.d. away. It was followed from Great Shefford until 06:42UT when it was lost in morning twilight, by which time it was about mag +17.5, had accelerated up to 346"/min and was only 23,000 miles outside the Moon's orbit. It crossed inside the Moon's orbit just 15 minutes later and closest approach was at 10:32UT when it passed at 0.5 l.d. Although not reported after 06:42UT it was anyway unobservable by 12:00UT on 29th, having faded back to mag +21 again but also moving at 1,000"/min! The entire apparition was over in less than 1.5 days during which time it had covered nearly 180 degrees of sky.

Although badly hampered by cloud, 2006 BH99 was then observed on the night of Jan 30 at mag +17 at 2.7 l.d., moving at 90"/min, passing by at just 1.2 l.d. about 14 hours later. Quite a busy few days!

Monday 2 January 2006

2005 December notes: 2005 YQ96, 2005 YW

There were not many long observing runs on NEOs during December, but probably the most interesting result was helping confirm the discovery of 2005 YQ96 on December 30th, which with an aphelion distance of 0.992 AU makes it the 6th known "Apohele", or Minor Planet with it's orbit completely inside the Earth's orbit.

Also, 2005 YW discovered on December 21 was examined carefully on a couple of nights for signs of cometary activity but it appeared stellar in a 26 minute exposure in good conditions on the 28th. This object has a period of about 2000 years and with perihelion at 2.0 AU due next winter it is possible it may eventually show activity. Unfortunately it will be lost in twilight this coming spring and will pull away from the Sun next winter but at far southerly declinations, not visible from the UK.