After a four year gap since the last "Meeting on Asteroids and Comets in Europe" (MACE) in Vienna in 2006, the 5th MACE took place in Visnjan/Tican, Croatia during 21-23 May (http://www.minorplanets.org/MACE2010/). Richard Miles and I attended from the UK and in all about 50 amateur and professional astronomers from all over Europe attended, together with Steve Chesley/JPL from the USA. Richard and I had the pleasure of meeting Jan Vales (P/2010 H2), discussing at length with him and others Richard's ideas on possible mechanisms that may have caused the dramatic outburst that led to Jan's discovery. The meeting also boasted comet discoverers Michel Ory (P/2008 Q2) and Eric Elst (133P/Elst-Pizarro), Korado Korlevic (183P/Korlevic-Juric and 203P/Korlevic) and of course the meeting organizer Reiner Stoss, co-founder of the La Sagra Sky Survey team that is credited with comets P/2009 QG31, P/2009 T2 and P/2009 WJ50.
Following on from the (130) Elektra result (TA 551,299), another occultation was successfully captured from Great Shefford, this time of the mag +10.5 star TYC 5573-00543-1 by (80) Sappho on June 4. The drift-scan image shows the starlight being blocked out by the minor planet for 5.5 seconds and revealing the minor planet shining faintly at mag. +11.8. John Broughton's SCANALYZER software was used to reduce the time of disappearance and reappearance (see full details here). At least one other UK observer, Tim Haymes in Maidenhead, Berkshire is also known to have succeeded in obtaining a positive result and other results are expected from France and Italy, which may lead to a determination of the asteroid's shape when all the results are in.
As well as a few very close approaches by newly discovered minor planets (the closest being 2010 JV39 to 0.65 Lunar Distances (LD) on May 26 and 2010 JL88 to 1 LD on May 17) there was also the discovery of unusual object 2010 KQ, originally added to the Minor Planet Center's NEO Confirmation page (NEOCP) on May 16 and observed from Great Shefford on the evening of May 17. Soon after my positions were sent in to the Minor Planet Center, Associate Director Gareth Williams removed it from the NEOCP with a note "was not a minor planet", adding it instead to his "Distant Artificial Satellites Observation Page" at http://www.minorplanetcenter.org/iau/SpaceJunk/SpaceJunk.html and indicated to me that further observations would still be useful. I got another set of measures the next night and sent them in to the MPC as Artificial Satellite positions. The next day all the positions obtained from discovery to May 18 were published in MPEC 2010-K15, announcing the object as minor planet 2010 KQ! It would approach the Earth to within 1.28 LD on May 21 and then gradually drift away, in an orbit quite similar to the Earth's (q=0.997 AU, P=396 days, e=0.055).
In the next week, spectral measurements were obtained by Richard Miles using the 2.0 Faulkes Telescope North and S.J. Bus using the NASA IRTF telescope, both on Hawaii and both observers determined independently that the spectrum of 2010 KQ does not match any known asteroid type, but is very similar to space weathered titanium dioxide paint and conclude that 2010 KQ is in fact very likely to be artificial. With further positional observations made in June it appears that the object made a very close approach to Earth in 1975, but it has not yet been possible to definitively match it to a spacecraft launch near that time.
Tuesday, 8 June 2010
Friday, 2 April 2010
2010 March notes: WISE and Pan-STARRS
Generally poor observing conditions throughout March hampered observing but a number of new NEOs were followed, after they had been posted on the Minor Planet Center's NEO confirmation page (NEOCP), which is now at this new address:http://www.minorplanetcenter.org/iau/NEO/ToConfirm.html
Although the majority of new objects in March were discovered as usual by the Catalina Sky Survey/Mt. Lemmon telescopes, the WISE Infrared Space Telescope has started to make a significant contribution. About 1 in 5 of the objects added to the NEOCP in February and March were WISE discoveries, however, these are likely to be "extra" objects. WISE is in a polar orbit and scans a great circle aligned 90 degrees from the Sun and so most if not all of the WISE discoveries are unlikely to have been found at that time by the other NASA funded surveys that tend to cover the opposition area of the sky, though some may eventually have been picked up by the ground based surveys as the objects tracked across the sky.
WISE uses a 16" mirror to observe in four bands in the infrared and converting the measured IR brightness into likely visual band magnitudes to be included on the NEOCP for Earthbound observers is tricky, some objects being relatively bright in the IR and others fainter. Many of the WISE discoveries are being listed with V magnitudes of 22-23 but some are brighter than these estimates would indicate and potentially in reach of amateurs.
Going after a WISE discovery with amateur equipment involves taking a large number of exposures and having to be resigned to the fact that there is a good chance that the effort will be for nothing if the object is too faint to be detected. However, WISE's IR eye is very good at picking up comets just as IRAS was 27 years ago. So if a WISE object is bright enough to be picked up it is well worth checking the images for signs of cometary activity. Three out of five WISE objects detected in March from Great Shefford turned out to be comets (P/2010 D2, C/2010 D4 and C/2010 E3).
The first Pan-STARRS 1.8-m telescope on Hawaii with its 1.4 gigapixel camera has also started submitting many hundreds of positions of minor planets to the Minor Planet Center this year and it can't be long before this gives all the other surveys some keen competition too.
Although the majority of new objects in March were discovered as usual by the Catalina Sky Survey/Mt. Lemmon telescopes, the WISE Infrared Space Telescope has started to make a significant contribution. About 1 in 5 of the objects added to the NEOCP in February and March were WISE discoveries, however, these are likely to be "extra" objects. WISE is in a polar orbit and scans a great circle aligned 90 degrees from the Sun and so most if not all of the WISE discoveries are unlikely to have been found at that time by the other NASA funded surveys that tend to cover the opposition area of the sky, though some may eventually have been picked up by the ground based surveys as the objects tracked across the sky.
WISE uses a 16" mirror to observe in four bands in the infrared and converting the measured IR brightness into likely visual band magnitudes to be included on the NEOCP for Earthbound observers is tricky, some objects being relatively bright in the IR and others fainter. Many of the WISE discoveries are being listed with V magnitudes of 22-23 but some are brighter than these estimates would indicate and potentially in reach of amateurs.
Going after a WISE discovery with amateur equipment involves taking a large number of exposures and having to be resigned to the fact that there is a good chance that the effort will be for nothing if the object is too faint to be detected. However, WISE's IR eye is very good at picking up comets just as IRAS was 27 years ago. So if a WISE object is bright enough to be picked up it is well worth checking the images for signs of cometary activity. Three out of five WISE objects detected in March from Great Shefford turned out to be comets (P/2010 D2, C/2010 D4 and C/2010 E3).
The first Pan-STARRS 1.8-m telescope on Hawaii with its 1.4 gigapixel camera has also started submitting many hundreds of positions of minor planets to the Minor Planet Center this year and it can't be long before this gives all the other surveys some keen competition too.
Friday, 5 February 2010
2010 January notes: 2010 AL30, 2010 AF40, 2010 BC, 2010 BU2 and 2010 BG5
A few relatively bright, newly discovered Near Earth Asteroids were followed during the month but the most newsworthy object 2010 AL30 passed just 0.33 Lunar Distances (LD) from Earth on 13th Jan. with the UK unfortunately shrouded in cloud. It was well observed from many other locations around the world and was last reported from Reedy Creek Observatory in Australia at 11:00UT on the 13th, less than 2 hours before closest approach and moving at 840"/min!
Less dramatic, 2010 AF40 had been discovered from Mt Lemmon on 12th Jan. and was followed from Great Shefford on the 17th and 19th. On the last date it was 16th mag., moving at about 40"/min and about 5 LD from Earth. It was last reported later on the 19th from the Sormano Observatory in Italy, going unobserved when it passed Earth at 2.3 LD about 35 hours later.
A Catalina discovery 2010 BC was followed on 16 and 17th Jan. at 17th mag. but it approached to within 8 LD by 24 Jan, maintaining 15th mag. for 4 nights, unfortunately during another cloudy period in the south of the UK.
More luck was had with the LINEAR discovery 2010 BU2, observed on three nights at the end of the month when it passed at 6.5 LD, reaching 16th mag. but with interference from the full Moon. Another LINEAR find, 2010 BG5 was moving almost due north at discovery on 25 Jan. and had already reached a dec. of +72°. It passed less than 4° from the North Pole on 28th and I picked it up in the early evening of 29th and 30th Jan, by which time it was moving at 40"/min. heading almost due south towards the northern horizon. It was at 6.6 LD and within a day of closest approach, but with the phase angle 95° and increasing it was fading fast at 19th mag.
Less dramatic, 2010 AF40 had been discovered from Mt Lemmon on 12th Jan. and was followed from Great Shefford on the 17th and 19th. On the last date it was 16th mag., moving at about 40"/min and about 5 LD from Earth. It was last reported later on the 19th from the Sormano Observatory in Italy, going unobserved when it passed Earth at 2.3 LD about 35 hours later.
A Catalina discovery 2010 BC was followed on 16 and 17th Jan. at 17th mag. but it approached to within 8 LD by 24 Jan, maintaining 15th mag. for 4 nights, unfortunately during another cloudy period in the south of the UK.
More luck was had with the LINEAR discovery 2010 BU2, observed on three nights at the end of the month when it passed at 6.5 LD, reaching 16th mag. but with interference from the full Moon. Another LINEAR find, 2010 BG5 was moving almost due north at discovery on 25 Jan. and had already reached a dec. of +72°. It passed less than 4° from the North Pole on 28th and I picked it up in the early evening of 29th and 30th Jan, by which time it was moving at 40"/min. heading almost due south towards the northern horizon. It was at 6.6 LD and within a day of closest approach, but with the phase angle 95° and increasing it was fading fast at 19th mag.
Friday, 8 January 2010
2009 December notes: 2009 WZ104, 9U01FF6, 2009 observing statistics
December provided a reasonable amount of observing time but the number of NEOs discovered by the surveys was much reduced, 34 new objects compared to the 116 they picked up in November, so NEO follow-up work was quieter than of late.
As well as following objects on the NEO Confirmation page, the opportunity was taken to follow 2009 WZ104 on several nights to try and determine its light curve. This is an Aten discovered on Nov. 25 by the Catalina Sky Survey and was brighter than 17th mag. for the first two weeks in December. However, not enough coverage was obtained to be able to find an unambiguous period, but it is likely to be longer than 6-8 hours.
The unusual artificial satellite 9U01FF6 mentioned last month in TA Vol 46 No 548 p211 (2009) which is in a 30+ day, very elongated orbit, taking it as close to us as 5 Earth diameters and about twice as far as the Moon at apogee, was picked up again on Dec. 27, three days before perigee. It was only 5" from the prediction calculated with FindOrb using positions from the previous two returns and taking into account Solar Radiation Pressure. Unfortunately the weather stopped any further observations but it should be visible next on the night of 6th Feb. 2010 and then in March a relatively long apparition, from the 11th-15th.
2009 overall was an exceptionally good year for observing at Great Shefford, producing the best observing figures since my observatory was commissioned in May 2002. Several statistics follow, with the previous best figures and year in parentheses: The most nights used (202 vs. 183 in 2003), the most hours spent at the telescope (938h vs. 838h in 2005), the largest amount of time the CCD shutter was open (24d 00h vs. 22d 03h in 2007) and far and away the largest number of images taken in a year (148,361 vs. 92,025 in 2007). That last statistic is in part to do with more Minor Planet photometry being done in 2009 than before, with many objects being followed for long periods of time, collecting many images during a night. The total number of images taken since 2002 passed the 1/2 million mark during the year and now stands at 570,575.
2009 generally seems to have beaten my previous records by 8-12% all round. Lets hope 2010 doesn't let us down!
As well as following objects on the NEO Confirmation page, the opportunity was taken to follow 2009 WZ104 on several nights to try and determine its light curve. This is an Aten discovered on Nov. 25 by the Catalina Sky Survey and was brighter than 17th mag. for the first two weeks in December. However, not enough coverage was obtained to be able to find an unambiguous period, but it is likely to be longer than 6-8 hours.
The unusual artificial satellite 9U01FF6 mentioned last month in TA Vol 46 No 548 p211 (2009) which is in a 30+ day, very elongated orbit, taking it as close to us as 5 Earth diameters and about twice as far as the Moon at apogee, was picked up again on Dec. 27, three days before perigee. It was only 5" from the prediction calculated with FindOrb using positions from the previous two returns and taking into account Solar Radiation Pressure. Unfortunately the weather stopped any further observations but it should be visible next on the night of 6th Feb. 2010 and then in March a relatively long apparition, from the 11th-15th.
2009 overall was an exceptionally good year for observing at Great Shefford, producing the best observing figures since my observatory was commissioned in May 2002. Several statistics follow, with the previous best figures and year in parentheses: The most nights used (202 vs. 183 in 2003), the most hours spent at the telescope (938h vs. 838h in 2005), the largest amount of time the CCD shutter was open (24d 00h vs. 22d 03h in 2007) and far and away the largest number of images taken in a year (148,361 vs. 92,025 in 2007). That last statistic is in part to do with more Minor Planet photometry being done in 2009 than before, with many objects being followed for long periods of time, collecting many images during a night. The total number of images taken since 2002 passed the 1/2 million mark during the year and now stands at 570,575.
2009 generally seems to have beaten my previous records by 8-12% all round. Lets hope 2010 doesn't let us down!
Sunday, 6 December 2009
2009 November notes: 2009 VX, 2009 VZ, 2009 WJ6, 2009 WV51 and 9U01FF6
Although many nights in November had interruptions from cloud, observing time was logged on 18 nights and there were plenty of Near Earth Objects to be followed that had been discovered during the month by the surveys.
Apollo 2009 VX had been discovered on Nov. 9th by the Catalina Sky Survey (CSS) as a 19th mag. object but had brightened to 17th mag. by the time it was picked up from Great Shefford early on the morning of Nov 12th, moving at 150"/min. It was then at 2.8 Lunar Distances (LD) and would pass at 2.59 LD at 13h UT the same day.
Another relatively bright new discovery was Apollo 2009 VZ and although it didn't get any closer than 15 LD it remained above 17th magnitude for 12 nights, I recorded it at 15th mag. on Nov. 12 & 14th. 2009 VZ was intrinsically about 5 magnitudes brighter than 2009 VX, which translates to 2009 VZ having a diameter about ten-times larger than 2009 VX (approx. 300 meters vs. 30 meters), assuming similar albedos for the two objects.
2009 WJ6 was another CSS discovery from Nov 19th and was followed from Great Shefford later that same day. By then it was already about mag. +17.0, at 2.1 LD and moving at 58"/min. It reached its closest to Earth at 11am UT the next day at 0.46 LD and was reported from the Westfield site of the Astronomical Research Observatory, Illinois three hours before perigee, at a distance of 0.82 LD.
One other close approach Apollo object was 2009 WV51. Discovered at 7am on Nov 23 by the CSS it was due to pass at just 0.39 LD the next day. I picked it up on the evening of Nov 23 at 17th magnitude when it was at a distance of 2.8 LD and moving at 'just' 22"/min. Watching individual images download it was easy to see it rising and falling in brightness by approximately 1 magnitude in just a few minutes, though the lightcurve has yet to be reduced. It was last reported from the Magdalena Ridge Observatory, New Mexico on Nov. 24 at 05:43 UT with the 2.4-m reflector, at a range of about 1.8 LD. It went unobserved from Great Shefford that night at its closest approach due to bad weather, but would have been 14th magnitude and moving at over 1,000"/min in the early evening of Nov. 24.
The probable artificial satellite 9U01FF6 mentioned last month was due back at perigee early on Nov. 28 after being followed for only 44 hours by 7 observatories at the end of October. I started searching for it on the evening of Nov 23 but given a likely positional uncertainty of up to 1°, the waxing Moon only about 30° to the south and the predicted mag. being +21.2 I was not expecting much success. However, it was picked up only 5' from the predicted position and ranging in magnitude from +20.5 up to +18.9, the standard asteroid magnitude formula obviously not providing a good fit for this object! Further positions obtained on three subsequent nights allowed the effect of Solar Radiation Pressure (SRP) to be determined using FindOrb using all the available observations (26 October - 27 November 2009). SRP effectively pushes an object away from the Sun and the smaller the mass and larger the surface area of the object exposed to the Sun, the larger the discrepancy from Newtonian motion may be observed. Without taking into account SRP the RMS residual for 78 positions over the two apparitions is a very unsatisfactory 16", but taking into account SRP this drops to 0.8". The value of SRP (or Area/Mass Ratio) determined was 0.011 m2/kg which is similar to those determined using FindOrb for other distant artificial satellites, e.g.
LCROSS (incl. Centaur) size 14.5m x 4.7m, mass ~3,200kg, SRP = 0.015 m2/kg
IMP8 size 1.4m x 1.6m, mass 371kg, SRP = 0.010 m2/kg
ASTRON (1983-020A) size 6m long, mass 3250kg, SRP = 0.008 m2/kg
and is 10 times larger than the 0.0011 m2/kg value derived for 2006 RH120 (=6R10DB9), the tiny (natural) minor planet that was temporarily trapped in Earth orbit during 2006-2007. All this points to 9U01FF6 being man-made and from a posting on the SeeSat-L (Visual Satellite Observers) mailing list here http://www.satobs.org/seesat/Oct-2009/0176.html it is suggested that 9U01FF6 is very likely to be from a lunar transfer mission of some kind, but the perturbations on the orbit make identification of the specific launch very difficult. It is noted that some of the Agena rockets for the Ranger missions of the 1960s were in very similar orbits.
Apollo 2009 VX had been discovered on Nov. 9th by the Catalina Sky Survey (CSS) as a 19th mag. object but had brightened to 17th mag. by the time it was picked up from Great Shefford early on the morning of Nov 12th, moving at 150"/min. It was then at 2.8 Lunar Distances (LD) and would pass at 2.59 LD at 13h UT the same day.
Another relatively bright new discovery was Apollo 2009 VZ and although it didn't get any closer than 15 LD it remained above 17th magnitude for 12 nights, I recorded it at 15th mag. on Nov. 12 & 14th. 2009 VZ was intrinsically about 5 magnitudes brighter than 2009 VX, which translates to 2009 VZ having a diameter about ten-times larger than 2009 VX (approx. 300 meters vs. 30 meters), assuming similar albedos for the two objects.
2009 WJ6 was another CSS discovery from Nov 19th and was followed from Great Shefford later that same day. By then it was already about mag. +17.0, at 2.1 LD and moving at 58"/min. It reached its closest to Earth at 11am UT the next day at 0.46 LD and was reported from the Westfield site of the Astronomical Research Observatory, Illinois three hours before perigee, at a distance of 0.82 LD.
One other close approach Apollo object was 2009 WV51. Discovered at 7am on Nov 23 by the CSS it was due to pass at just 0.39 LD the next day. I picked it up on the evening of Nov 23 at 17th magnitude when it was at a distance of 2.8 LD and moving at 'just' 22"/min. Watching individual images download it was easy to see it rising and falling in brightness by approximately 1 magnitude in just a few minutes, though the lightcurve has yet to be reduced. It was last reported from the Magdalena Ridge Observatory, New Mexico on Nov. 24 at 05:43 UT with the 2.4-m reflector, at a range of about 1.8 LD. It went unobserved from Great Shefford that night at its closest approach due to bad weather, but would have been 14th magnitude and moving at over 1,000"/min in the early evening of Nov. 24.
The probable artificial satellite 9U01FF6 mentioned last month was due back at perigee early on Nov. 28 after being followed for only 44 hours by 7 observatories at the end of October. I started searching for it on the evening of Nov 23 but given a likely positional uncertainty of up to 1°, the waxing Moon only about 30° to the south and the predicted mag. being +21.2 I was not expecting much success. However, it was picked up only 5' from the predicted position and ranging in magnitude from +20.5 up to +18.9, the standard asteroid magnitude formula obviously not providing a good fit for this object! Further positions obtained on three subsequent nights allowed the effect of Solar Radiation Pressure (SRP) to be determined using FindOrb using all the available observations (26 October - 27 November 2009). SRP effectively pushes an object away from the Sun and the smaller the mass and larger the surface area of the object exposed to the Sun, the larger the discrepancy from Newtonian motion may be observed. Without taking into account SRP the RMS residual for 78 positions over the two apparitions is a very unsatisfactory 16", but taking into account SRP this drops to 0.8". The value of SRP (or Area/Mass Ratio) determined was 0.011 m2/kg which is similar to those determined using FindOrb for other distant artificial satellites, e.g.
LCROSS (incl. Centaur) size 14.5m x 4.7m, mass ~3,200kg, SRP = 0.015 m2/kg
IMP8 size 1.4m x 1.6m, mass 371kg, SRP = 0.010 m2/kg
ASTRON (1983-020A) size 6m long, mass 3250kg, SRP = 0.008 m2/kg
and is 10 times larger than the 0.0011 m2/kg value derived for 2006 RH120 (=6R10DB9), the tiny (natural) minor planet that was temporarily trapped in Earth orbit during 2006-2007. All this points to 9U01FF6 being man-made and from a posting on the SeeSat-L (Visual Satellite Observers) mailing list here http://www.satobs.org/seesat/Oct-2009/0176.html it is suggested that 9U01FF6 is very likely to be from a lunar transfer mission of some kind, but the perturbations on the orbit make identification of the specific launch very difficult. It is noted that some of the Agena rockets for the Ranger missions of the 1960s were in very similar orbits.
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