2009 March notes: 2009 DD45, 2009 EW, 2009 FH, 2009 DO111, 2009 FD

March and October are statistically the most likely months for NEOs to be discovered that will make very close passes, within 1 Lunar Distance (LD) of the Earth and this March was no exception.

March got off to a good start with the very close fly-by of NEO 2009 DD45, the picture taken during brief gaps in clouds just after midnight on the 3rd when it was at about 0.9 LD from the Earth. Unusually, it was bright enough to be observed from three days before closest approach (discovery by Rob McNaught at Siding Spring at mag +18.7), reaching mag +10 briefly at its closest when at just 0.18 LD (less than 6 Earth diameters away!), fading to 16th mag by the time I first picked it up, but then still detectable at mag +19 in the rich star fields 10°N of Vega three nights later, somewhat brighter than predicted by the MPC ephemeris.

Even before 2009 DD45 had passed Earth, the next close approach object was queuing up. 2009 EW was discovered by the Catalina Sky Survey on March 2nd and picked up from Great Shefford on March 3.0 and again on March 4.9, before being followed through the night of March 5/6th when it came to within 0.9 LD. It was last detected 30 minutes before closest approach at mag +17, moving at 466"/min, 22° above the northern horizon.

Remarkably, less than two weeks later on March 17th, another NEO, 2009 FH was discovered by Catalina, 28 hours before an encounter that would bring it to within 0.22 LD of Earth. When first picked up at Great Shefford at 19:38 UT on the 17th it was already within 1 LD, mag +15 and moving at the relatively sedate speed of 57"/min. I followed it for 2 hours by which time it was 0.8 LD from Earth and had accelerated to 75"/min. It was last reported at 05:02 UT on 18th March, 7 hours before closest approach, at mag +13 and moving at 250"/min by the Catalina Sky Survey's Mt. Lemmon 1.5-m reflector.

A very preliminary light curve from 220 brightness measurements on March 17th indicates 2009 FH has a rotational period of only 6 minutes 26 seconds, with an amplitude of about 0.3 mags. It made more than 13 full rotations during the 1h 27 minutes the observations span.

There were a number of other objects that made approaches nearly as close as the Moon, notable were 2009 DO111, passing 1.2 LD from Earth early on March 20th, as bright as mag +12 and showing rotational variations of about 1 magnitude by March 19th and also 2009 FD passing at 1.6 LD on March 27, again reaching mag +12. Unusually, this latter object was not discovered by one of the NASA funded surveys but rather by the team operating the La Sagra Observatory in Southern Spain.

2009 February notes: 2009 BL58, 2009 BG81, 2009 DS43

Early in February a few fast movers were observed, Apollo 2009 BL58 had been discovered at the end of January by the Catalina Sky Survey. When first observed on 9th Feb it was mag +17.1 and placed 5° SE of Regulus, moving swiftly SE. It was observed two nights later, 45° further on in Hydra at -25° Dec, a degree S of Alpha Corvus and although still mag +17.7, because of its altitude of only 13° was much more difficult to record. It was just a few hours away from its closest to Earth at 4.8 Lunar Distances (LD) and moving at 70"/min.

Apollo 2009 BG81 was a LINEAR discovery from Jan 31st and picked up on the evening of Feb 1st moving at 51"/min, already as close as 4.6 LD but only 19th mag. It came to 4.4 LD on Feb 2nd and was observed by three other observatories but was not reported after that date. With an estimated diameter of 7 metres 2009 BG81 was intrinsically about 4 times smaller than 2009 BL58.

At the end of the month another small Apollo, 2009 DS43 was picked up on 27th Feb in Sextans, first by LINEAR and 97 minutes later by the Catalina Sky Survey (CSS). CSS reported their observations first and were credited with the discovery. It was mag 18 and moving almost due N at 38"/min. I first observed it on the evening of 28th Feb at mag +17.8 by which time it had accelerated to 94"/min and had reached +39° Dec. By then it was at 6.9 LD and would reach its closest at 3am on 1st March at 6.7 LD. By the evening of the 1st it was at a declination of +76° midway between the Pointers and Polaris, had slowed to 81"/min and receded to 7.4 LD and was fading fast, more than 1 mag fainter than the previous night. The Minor Planet Center didn't receive any further reports of it.

2009 January notes: 2009 BB77, 2008 YG30, 2008 YY32, 2009 BE, 2009 BJ2, 2009 BD, EPOXI, NeXT

Congratulations to Richard Miles for his first Minor Planet discovery, 2009 BB77 picked up on Jan 30th while he was imaging Comet 17P/Holmes with the Faulkes North telescope!

January provided decent amounts of clear sky at Great Shefford, with 76 hours logged observing. Several NEOs were followed during close approaches, 2008 YG30 was mag +16 and moving at 70"/min on the night of Jan 3rd, 4 Lunar Distances (L.D.) from Earth and due to pass at 3.6 LD the next day. Early on Jan 4th, 2008 YY32 was observed and at 6 LD was already at its closest to Earth, moving at 50"/min and rather fainter at mag +18.2.

After the full moon, on the night of Jan 20th, 2009 BE was seen at mag +17 when it was at 6 LD, but unfortunately cloud prevented it from being observed again, closest approach was on Jan 23rd at 2 LD. The same night another NEO, 2009 BJ2 was imaged but was probably the most challenging object observed in the month. I had followed it the previous two nights but by Jan 20th it was at its closest at 4.7 LD and at its fastest speed of 60"/min. However it had already faded by half a magnitude to mag +19.1 and was very low in the south, in the centre of Canis Major, about 3 degrees SW of M41. The rich Milky Way star-field made identification difficult and the next (cloudy) night was spent discarding many of the 320 images that had been taken when it was masked by stars and then measuring positions from stacks of the remaining images.

Tiny NEO 2009 BD, discovered by the Mt Lemmon 1.5-m reflector of the Catalina Sky Survey on Jan 16th turned out to be quite unusual. It was moving at 10"/min at discovery, but was already only 3 LD from Earth. Over the next 9 days it would gradually drift closer, passing just 1.8 LD from Earth early on Jan 25th and was observed on 5 nights, the last time early on Jan 26th when it was below Polaris, at declination +84°, mag +18.5 and moving at 26"/min. It is probably only about 5 meters in diameter and currently in an orbit very similar to Earth's, with a period of 372 days, an inclination of 1� and a low eccentricity of 0.05. Bill Gray (author of Guide and FindOrb) writes that the available astrometry from Jan 16-26th allows the orbit to be very well determined and shows that it was last in the Earth's vicinity (at a distance of 1.2 LD) around 16 July 1955, with an uncertainty of only about +/- 1 hour! At 01:03 UT on 2nd June 2011 it is due to approach the Earth even closer at a distance of 346,658 Km (= 0.9 LD) with likely uncertainties of just 15 minutes in time and 300 Km in distance. Unfortunately it will then be far south at a declination of -50°, but coming north a few days later when it should be visible once again from northern latitudes.

Two artificial satellites were also observed with a rather unusual connection to each other: On the night of December 30th the EPOXI spacecraft was tracked while at 0.77 LD, at mag +19.2 and moving at 30"/min, midway between Vega and the head of Draco. This was 24 hours after a gravity-assist fly-by of Earth when it had approached to within 50,000Km (= 0.1 LD). EPOXI is the new name for the fly-by spacecraft of the Deep Impact mission that encountered Comet Tempel 1 in 2005 and now on its way to a rendezvous with Comet Hartley 2 in October 2010. The other satellite was the NeXT mission, being the renamed Stardust spacecraft that collected dust samples from Comet Wild 2 in 2004 and has now been re-directed to encounter Comet Tempel 1 in February 2011 to image the crater left by the impactor from Deep Impact! NeXT was seen briefly on the morning of Jan 13th and also followed for 7.5 hours the following night. When last seen it was at 1.1 LD and mag +17, moving at 11"/min, but due to skim just 9,000 Km (= 0.7 Earth diameters!) above the surface of the Earth less than 18 hours later. Unfortunately the close approach night was clouded out.

2008 November notes: 2008 VV4 = 2001 XQ, 2004 XK3

With the amount of clear skies in November only amounting to about 40% of that in October, it was a rather disappointing month.

An 18th mag object discovered by the Catalina survey and observed while it was still listed on the NEO Confirmation page on Nov 7th was subsequently given the temporary ID 2008 VV4 and re-observed on Nov 12th by which time JPL was listing it as a "Virtual Impactor" with 17 possible impacts predicted, the first in 2021. While checking for other NEO targets to observe that night I noticed that 2008 VV4 was in the same area of sky and had very similar speed and direction of motion as the Amor object 2001 XQ, as listed on the Minor Planet Center's List of Bright Recovery Opportunities page at http://www.cfa.harvard.edu/iau/NEO/BrightRecovery.html.

2008 VV4 turned out to be the same as the earlier object, 17° from its predicted position and the recovery of 2001 XQ was announced in MPEC 2008-V57. With a period of 6.96 years the circumstances of this apparition were similar to when first discovered in Dec 2001, with the object being at perihelion in early December and moving swiftly south from high northern declinations during November. With the extra 7 years of orbital arc available, JPL was able to calculate that there was no danger of collision with the Earth and it was removed from their risk page at http://neo.jpl.nasa.gov/risk/.

Another object observed while on the NEO Confirmation Page and ending up being a re-discovery of a previously observed object was 2004 XK3. This time it had been picked up by LINEAR as a fast moving 15th mag object and was 14th mag when I observed it only 15 hours later. It was identified within hours by the Minor Planet Center as 2004 XK3 and removed from the NEOCP. With a period of 1.36 years it had done almost exactly three revolutions in the four years since discovery and in fact was only 7° away from the place in the sky where I had observed it four years earlier.

2008 October: Observing statistics, 2008 UL90, 2008 UT95, 2008 TT26, 2008 TC26, 2008 TQ10, 2008 TR10, 2008 UX202

After months of disappointing weather throughout the summer at Great Shefford, October proved to be exceptionally good, with the largest number of hours (125h) recorded at the telescope in a single month since I commissioned the observatory in 2002.

The big news early in the month was the brief appearance of 2008 TC3, hours before impacting Earth early on Oct 7th. However, there were plenty of other new objects discovered by the surveys during the month, with over 50 being observed after having been put on the NEO Confirmation Page (NEOCP) by the Minor Planet Center.

One of the more interesting objects was 2008 UL90, a member of the rare Interior Earth Objects, or so called Apohele class, with orbits entirely inside the orbit of the Earth. There are only 14 definite or suspected members of this class to date. This one was at 66 degrees elongation in the morning sky when observed. It should brighten slightly to about mag +19.7 and the elongation increase by just a couple of degrees by mid-November before it slips back into the glare of the Sun during December.

A few fast movers were also followed, 2008 UT95 was last caught moving at 40"/min, just over 4 Lunar Distances (LD) from Earth on the night of Oct 31/Nov 1st, two days before passing Earth at 1.5 LD, but it was not reported from any observatory after Nov 1st. 2008 TT26 was well observed from a number of observatories during October and briefly reached mag +14 around Oct 22/23 when it was recorded moving at about 50"/min, at a distance of about 3.5 LD.

The good weather brought another record for me, a total of 12 new minor planets discovered during the month, with 9 of them found in the field of NEOCP objects. One, 2008 TC26, turned out to be a Hungaria class object, with an orbit inside the main belt, just further out than Mars and was found in the same field of view as two(!) NEOCP objects, 2008 TQ10 and 2008 TR10. The last of the new objects found was 2008 UX202 on 28 Oct and confirmed 3 nights later. This turned out to have a perihelion distance of 1.68 A.U., just outside the aphelion distance of Mars and like 2008 TC26 is in the inner zone of the main belt.