Northolt Branch Observatories

Periodic comet 21P/Giacobini-Zinner, 37 days before perihelion
The inner coma is tear-shaped, the bright central condensation appears very elongated. The outer coma is growing, and the comet appears to become more active. It shows a broad tail at least 8 arcminutes long (extending beyond our field of view). 21P will come within 0.39 AU (58.6 million km) from Earth on September 10th, when it should reach +7 mag. Now it is approaching 9th magnitude.
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Periodic comet 21P/Giacobini-Zinner, 37 days before perihelion
The inner coma is tear-shaped, the bright central condensation appears very elongated. The outer coma is growing, and the comet appears to become more active. It shows a broad tail at least 8 arcminutes long (extending beyond our field of view). Two short but prominent jets (30" in PA 53°, 25" in PA 92°) are visible with Larson-Sekanina filter. In hindsight, we see the same feature in images taken on July 25th, Ju...ly 31st and August 2nd (https://goo.gl/fhp6MJ, https://goo.gl/zL2mLb, https://goo.gl/JhEGCh). No sign of it was visible on July 15th. 21P will come within 0.39 AU (58.6 million km) from Earth on September 10th, when it should reach +7 mag. Now it is approaching 9th magnitude.
Photometry (APASS V comparison stars unfiltered, 270" aperture radius): m1 = 9.4 ± 0.1 mag Nuclear magnitude (Gaia DR2 G magnitude unfiltered, 8" aperture radius): m2 = 11.6 ± 0.1 mag
Measurement in ICQ format: 21 2018 08 03.99 C 9.4 AQ 25.4Y 7A800 9.1 8.0m254 ICQ XX BAMaaI C 9.10mG2x ICY KPR 0 U9*0.03 2.1s 2.1
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Comet 29P/Schwassmann-Wachmann in outburst
We confirm an observation by J.-F. Soulier, who reported 29P to be as bright as 14.2 mag on the morning of August 1st. Now, about 2.2 days into the outburst, we see a bright circular coma with a diameter of 20.5 arcseconds, superimposed on a fainter outer coma. 29P undergoes regular outbursts, but this is the brightest outburst of the year. We have seen it brighten to 12.3 mag in August 2017 (https://goo.gl/KyB9Nb). Our last observat...ions date from July 24th, when the comet was about 16.5 mag.
Photometry (APASS V comparison stars unfiltered, 42" aperture radius): m1 = 14.1 ± 0.1 mag Nuclear magnitude (Gaia DR2 G magntiude unfiltered, 8" aperture radius): m2 = 14.7 ± 0.1 mag
Measurement in ICQ format: 29 2018 08 03.05 C 14.1 AQ 25.4Y 7A800 1.4 ICQ XX BAMaaI C 1.40mG2x ICY KPR 0 U9*0.03 2.1s 2.1
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A107IQ9 is a possible new comet that was first observed at ATLAS survey on July 22nd (with precoveries from Zwicky Transient Factory, Palomar Mountain, from July 15th). It will reach perihelion in late August, at a distance of 1.56 AU from the Sun. A107IQ9 is currently visible at +18.8 mag, and is not predicted to get any brighter than this.
A107IQ9 appears to be in an orbit typical for a Halley-type comet, with an orbital period of about 150 ± 10 years and an inclination of ...154°.
We have observed this object before, on July 24th (see https://goo.gl/tX8hYh).
Photometry (Gaia DR2 G magnitude unfiltered, 8" aperture radius): m1 = 18.6 ± 0.2 mag Slightly fuzzy; coma 14" in diameter, no tail visible
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Near Earth asteroids 2061 Anza and (162168) 1999 GT6
2061 Anza is an Amor-type asteroid with a diameter of about 2.6 km. It will make a close approach on August 23rd, at a distance of 0.20 AU (30 million km) from Earth. Now it is visible at +15.6 mag and brightening. Anza is a C-type asteroid, which suggests that it probably has a dark surface. Its rotation period is 11.5 hours, with an amplitude of 0.3 mag. This indicates that it is moderately elongated. Nothing else is know...n about its physical properties.
(162168) 1999 GT6 is an Amor-type asteroid with a diameter of 1.2-2.6 km. It made a distant flyby on June 17th, when it came within 0.26 AU (39.4 million km) of Earth. 1999 GT6 is currently observable at +16.6 mag and slowly fading. Apart from its rotation period of 3.85 hours, which is relatively fast for an asteroid of this size, not much is known about this object. The distant spiral galaxy PGC 71819, which is located about 290 million light-years from Earth, is visible in the bottom right corner of the image.
Both images were taken under hazy conditions.
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Periodic comet 21P/Giacobini-Zinner, 39 days before perihelion
Comet 21P is visible at +9.3 mag, with an apparent size of about 8 arcminutes. A broad tail at least 9.3 arcminutes long is visible, together with a possible jet pointing in the opposite direction. The inner coma appears tear-shaped, with a bright central condensation 42x22 arcseconds in diameter. 21P will come within 0.39 AU (58.6 million km) from Earth on September 10th, when it should reach 7th magnitude.
... Photometry (APASS V comparison stars unfiltered, 230" aperture radius): m1 = 9.3 ± 0.1 mag Nuclear magnitude (Gaia DR2 G magnitude unfiltered, 8" aperture radius): m2 = 11.8 ± 0.1 mag
Measurement in ICQ format: 21 2018 08 02.04 C 9.3 AQ 25.4Y 7A200 7.7 9.3m250 ICQ XX BAMaaI C 7.70mG2x ICY KPR 0 U9*0.08 2.1s 2.1
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Near Earth asteroids 2012 OD1 and 2018 NU3
2012 OD1 is an Aten-type potentially hazardous asteroid with a diameter of 570-1300 metres. It made a distant flyby on July 24th, at a distance of 0.20 AU (29.3 million km) from Earth. Now it is visible at +17.7 mag and fading, moving through a dense star field in the constellation Lacerta.
2018 NU3 is an Amor-type asteroid with a diameter of 210-480 metres. It was first observed at Pan-STARRS 1, Haleakala on July 12th, and it will m...ake a close approach on August 25th, at a distance of 0.11 AU (15.8 million km). 2018 NU3 is currently observable at +18.0 mag and brightening.
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Periodic comet 21P/Giacobini-Zinner, 40 days before perihelion
Comet 21P continues to brighten as it approaches the Earth. It will come within 0.39 AU (58.6 million km) on September 10th, which is also the day of its perihelion passage. It should reach 7th magnitude at that time. Now it is +9.5 mag, with a coma 7.3 arcminutes in diameter. The central condensation appears elongated. A broad tail at least 16.7 arcminutes long is visible, extending beyond the edge of the field o...f few.
Photometry (APASS V comparison stars unfiltered, 220" aperture radius): m1 = 9.5 ± 0.1 mag Nuclear magnitude (Gaia DR2 G magnitude unfiltered, 8" aperture radius): m2 = 11.8 ± 0.1 mag
Measurement in ICQ format: 21 2018 07 31.93 C 9.5 AQ 25.4Y 7A200 7.3 16.7m253 ICQ XX BAMaaI C 7.35mG2x ICY KPR 0 U9*0.07 2.1s 2.1
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The demise of comet C/2017 S3 (PANSTARRS)
After two spectacular outbursts in early and mid July, the nucleus of comet C/2017 S3 (PANSTARRS) has finally disintegrated. This doesn't come as a surprise: Small comets like this don't usually survive their passage by the Sun. Even though the show is now probably over, we are happy to have followed comet PANSTARRS from before the outbursts began (June 25, https://goo.gl/r4eEYK) until two nights ago, when all that was left of it was ...a cloud of debris (https://goo.gl/HkAVWr).
To remember comet PANSTARRS and show its evolution, we have put together a short video. It starts in late June when the comet was still quiet, followed by the outburst of July 1st, subsequent fading, a second - much brighter - outburst on July 15th, and finally its demise as a fuzzy cloud.
A lightcurve of C/2017 S3 (PANSTARRS) can be found here: https://goo.gl/DdpEU3.
Farewell, comet PANSTARRS!
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Near Earth asteroids 2011 GA62 and 2018 GA5
2011 GA62 is an Amor-type asteroid with a diameter of 500-1100 metres. It made a close approach on June 18th, at a distance of 0.16 AU (23 million km) from Earth. Now it is visible at +17.6 mag and fading.
2018 GA5 is an Amor-type asteroid with a diameter of 600-1400 metres. It will make a distant flyby on July 31st, when it comes within 0.25 AU (37 million km) from Earth. It is currently observable at +18.0 mag and brightening.... Its eccentric orbit results in frequent encounters with Jupiter, making it unstable on time scales of a few millennia. 2018 GA5 may be an extinct Jupiter-family comet (see https://goo.gl/2cFMxf).
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Periodic comet 21P/Giacobini-Zinner, 46 days before perihelion
The near-Earth comet 21P/Giacobini-Zinner continues to brighten as it approaches its perihelion. It will come within 0.39 AU (58.6 million km) of Earth on September 10th, when it is expected to reach +7 mag in August and September. Now it is +9.6 mag, moving through the constellation Cepheus. By now, it should be an easy target for binoculars or small telescopes from dark sites. The comet displays a bright central... condensation and a highly elongated coma. It continues to grow, approaching the size of our field of view (15x11 arcminutes). The broad tail can be traced to 10 arcminutes from the nucleus.
Photometry (APASS V magnitude unfiltered, 190" aperture radius): m1 = 9.6 ± 0.1 mag Nuclear magnitude (Gaia DR2 G magnitude unfiltered, 8" aperture radius): m2 = 12.5 ± 0.1 mag Inner coma 60x40 arcseconds, elongated in PA 225° Outer coma 10x7 arcminutes, elongated in PA 237° Tail 10 arcminutes long in PA 247° Comet altitude 62.5°
Measurement in ICQ format: 21 2018 07 25.99 C 9.6 AQ 25.4Y 7A540 6.3 10.1m247 ICQ XX BAMaaI C 6.30mG2x ICY KPR 0 U9*0.08 2.1s 2.1
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Comet C/2017 S3 (PANSTARRS), 21 days before perihelion
Since the outburst of July 15th, this comet continues to fade. It is now below 11th magnitude. The central condensation is completely absent, indicating that the nucleus may have disintegrated.
Our astrometry continues to deviate from the ephemeris calculated up to July 20th (see https://goo.gl/FZQGkV). As of 2018-07-26.07, the difference is -9.2" in RA and +8.4" in DE.
... C/2017 S3 will reach perihelion on August 15th, at a distance of only 0.21 AU from the Sun. The comet is now moving closer to the Sun in our sky, and it becomes more and more difficult to observe.
Photometry (APASS V unfiltered, 147" aperture radius): m1 = 11.2 ± 0.1 mag Nuclear magnitude (Gaia DR2 G magnitude unfiltered, 11" aperture radius): m2 = 14.0 ± 0.1 mag Outer coma 4.3x3.4 arcminutes, elongated in PA 325° Inner coma 51x34 arcseconds, elongated in PA 305°, diffuse without central condensation Broad tail 3.1 arcminutes long in PA 309° Comet altitude 22°
Measurement in ICQ format: 2017S3 2018 07 26.07 C 11.2 AQ 25.4Y 7a920 4.9 3.1m309 ICQ XX BAMaaI C 4.90mG2x ICY KPR 0 U9*0.06 2.1s 2.1
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Near Earth asteroids 2018 NB, 2012 OD1 and (3552) Don Quixote - and a new observation format!
Beginning on July 25th, it is possible to submit data to the Minor Planet Center via the improved ADES format. This allows to specify more details about the object and the observation process. We discontinue the use of the old obs80 format for asteroids as of today (we still use it for comets until further notice) in favour of ADES. You can find details about the changes in the offic...ial announcement by the Minor Planet Center: https://minorplanetcenter.net/mpec/K18/K1 8N52.html
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2018 NB ( = 2003 KT24) is an Amor-type asteroid with a diameter of 380-860 metres. It was first observed at Cerro Tololo Observatory, La Serena, in May 2003, and then again by ATLAS on 1 July 2018. 2018 NB made a close approach on July 21st when it came within 0.085 AU (12.8 million km) of Earth. Now it is visible at +16.0 mag and fading. We helped to confirm this object in early July (https://goo.gl/jnYhd5). On July 18th, it was found to be identical with the lost asteroid 2003 KT24 (https://goo.gl/KA6Hir).
2012 OD1 is an Aten-type potentially hazardous asteroid with a diameter of 570-1300 metres. It made a distant flyby on July 24th, at a distance of 0.20 AU (29.3 million km) from Earth. This asteroid is expected to come within 0.038 AU (5.7 million km) in July 2024. Now it is visible at +17.8 mag and brightening.
(3552) Don Quixote is an unusual Amor-type asteroid and possible periodic comet with a diameter of 19 km. It orbits the Sun in an eccentric orbit once every 8.8 years. Don Quixote reached perihelion in May 2018 and is now visible at +16.2 mag. In 2013, a tail and comet have been observed, showing that Don Quixote is actually a comet (see https://goo.gl/pa2CZL for details).
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2018 NB is an Amor-type asteroid with a diameter of 380-860 metres. It was first observed by ATLAS on July 1st, and made a close approach on July 21st when it came within 0.085 AU (12.8 million km) of Earth. Now it is visible at +15.9 mag and fading.
#SpotTheAsteroid
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Comet C/2017 S3 (PANSTARRS), 22 days before perihelion
Since its recent outbursts on July 1 and July 15, this comet has faded considerably. It has lost its bright central condensation, and now appears more diffuse than last week (see https://goo.gl/aU87vJ). The coma appears more elongated. We find our astrometry to be inconsistent with measurements made before the outburst of July 20th, confirming a recent report by B. Lütkenhöner (comets-ml). The deviation at the time of our... observations (2018 07 25.054) is about -6.7" in RA and +5.9" in DE. This suggests that a significant change of the orbit occured around the time of the outburst. C/2017 S3 will reach perihelion on August 15th, at a distance of only 0.21 AU from the Sun. It is not expected to survive beyond perihelion. The comet is now moving closer to the Sun in our sky, and it becomes more and more difficult to observe.
Photometry (APASS V unfiltered, 137" aperture radius): m1 = 10.7 ± 0.1 mag Nuclear magnitude (Gaia DR2 G magnitude unfiltered, 8" aperture radius): m2 = 13.9 ± 0.1 mag Very diffuse, no central condensation Inner coma 55x36 arcseconds, elongated in PA 306° Outer coma 4 arcminutes in diameter, broad tail 3.7 arcminutes long in PA 312° Comet altitude 22.1°
Measurement in ICQ format: 2017S3 2018 07 25.05 C 10.7 AQ 25.4Y 7A200 4.5 3.7m312 ICQ XX BAMaaI C 4.55mG2x ICY KPR 0 U9*0.02 2.1s 2.1
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The NEO Confirmation Page object MB135, which we observed yesterday, has been designated 2018 OW. It is a main-belt asteroid with a diameter of 900m-2000m. 2018 OW is currently observable at mag +18.7.
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The NEO Confirmation Page object MB135, which was first observed on July 20th at Vedrus Observatory, Azovskaya, Russia, is a main belt asteroid with a diameter of 1.1-2.5 km. We observed it last night at +18.9 mag. MB135 will come to opposition in early August, just a few weeks before perihelion. It is expected to reach +18.0 mag at that time.
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Comet 29P/Schwassmann-Wachmann, 48 days before opposition
29P/Schwassmann-Wachmann is a distant comet, orbiting on an unusual nearly circular orbit between Jupiter and Saturn with a period of 14.7 years. It will come to opposition in September. 29P is noticeable for its frequent recurring outbursts (see https://goo.gl/fSpi3m). Similar in appearance to our last observation from July 12th (https://goo.gl/3giPnc), we saw it in a quiescent state last night.
Photometry (APASS V un...filtered, 74" aperture radius): m1 = 13.9 ± 0.1 mag Nuclear magnitude (Gaia DR2 G magnitude unfiltered, 8" aperture radius): m2 = 16.6 ± 0.1 mag Bright central condensation Outer coma diffuse, 2.5 arcminutes in diameter, elongated in PA 159° Comet altitude 31.8°
Measurement in ICQ format: 29 2018 07 24.04 C 13.9 AQ 25.4Y 7A200 2.5 ICQ XX BAMaaI C 2.45mG2x ICY KPR 0 U9*0.03 2.1s 2.1
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A107IQ9 is a possible new comet that was first observed at ATLAS survey on July 22nd. It will reach perihelion in late August. A107IQ9 is currently visible at +18.9 mag, and is not predicted to get any brighter than this.
Photometry (APASS V unfiltered, 13" aperture radius): m1 = 18.9 +/- 0.2 mag Fuzzy; coma 13" in diameter, possible tail 16" long in PA 138°
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