Close Approach of Asteroid (4179) Toutatis

4179 Toutatis was discovered by C. Pollas at Caussols (France) on January 4, 1989. 4179 Toutatis was first sighted on February 10, 1934, as object 1934 CT, and then promptly lost. It remained a lost asteroid for several decades until it  was discovered by Pollas.

According to Minor Planet Circ. 16444: "Named after the Gaulish god, protector of the tribe. This totemic deity is well known because of the cartoon series "Les aventures d'Asterix" by Uderzo and Goscinny. This tells the stories of two almost fearless heroes living in the last village under siege in Roman-occupied Gaul in 50 B.C., and whose only fear is that the sky may fall onto their heads one day. Since this object is the Apollo object with the smallest inclination known, it is a good candidate to fall on our heads one of these days... But as the chief of the village always says: "C'est pas demain la veille..." Citation written by the discoverer and A. Maury and endorsed by J. D. Mulholland, who with Maury obtained the discovery plates."

4179 Toutatis is a highly irregular body consisting of two distinct "lobes", with maximum widths of about 4.5 km and 2.4 km respectively (4.5 × 2.4 × 1.9 km; absolute magnitude H=15.3) and it had a close approach with Earth at about 18 LD (Lunar Distances = ~384,000 kilometers) or 0.0463 AU (1 AU = ~150 million kilometers) at 0640 UT on Dec. 12, 2012. Its magnitude will be between 10.5 to 11 from December 11 through December 23, 2012.

Moreover, Toutatis will be the target of a flyby by the Chinese Chang'e 2 spacecraft on December 13, 2012   Chang'e 2 was originally launched to study the Moon but was diverted in April, 2012 for the asteroid encounter.

We performed some follow-up measurements of this object just few hours before its 2012 close approach, from the I89 iTelescope network (Nerpio, Spain) on  2012, Dec. 11.9, through a 0.15-m f/7.3 refractor + CCD. Below you can see our image, single 120-second exposure, taken with the asteroid at magnitude ~10.5 and moving at ~20.7"/min. The asteroid is trailed in the image due to its fast speed. At the moment of the close approach 4179 Toutatis will move at ~ 21.86"/min. Click on the image below to see a bigger version. North is up, East is to the left.

Below you can see a short animation showing the movement of 4179 Toutatis (40 consecutive 10-second exposures). East is up, North is to the right. Click on the thumbnail for a bigger version:

Toutatis passes by Earth’s orbit roughly every 4 years. Four years ago it didn’t come quite so close (0.0502 AU). But four years before that (in September 2004) it missed us by just 0.0104 a.u., less than a quarter of its distance this time. The next notable close approach of Toutatis will be November 5, 2069, when the asteroid will fly by at a distance of only 0.0198 AU (7.7 lunar distances). See graphs below (click on it for bigger versions).

Credit: Hazards Due to Comets & Asteroids by T. Gehrels - University of Arizon Press

Credit: Hazards Due to Comets & Asteroids by T. Gehrels - University of Arizon Press

Thanks to its proximity and size Toutatis was a strong target for radar imaging. Astronomers of NASA's Goldstone radar were tracking the asteroid as it passes by Earth and they obtained images of unprecedented clarity. Click on the image below for a bigger version.

2012 Goldstone Radar Observations of (4179) Toutatis

According to  radar team member Michael Busch: "Toutatis appears to have a complicated internal structure. Our radar measurements are consistent with the asteroid's little lobe being ~15% denser than the big lobe; and they indicate 20% to 30% over-dense cores inside the two lobes.". This raises the interesting possibility that asteroid Toutatis is actually a mash up of smaller space rocks.  "Toutatis could be re-accumulated debris from an asteroid-asteroid collision in the main belt," he says.

UPDATE - December 18, 2012

The Chinese Chang'e 2 spacecraft has successfully imaged Toutatis during his flyby on December 13, 2012. See image below captured at 93–240 km distance between 16:30:09–16:30:24, maximum resolution 10 meters/pixel. Click on the image for a bigger version.

by Ernesto Guido & Nick Howes

Close Approach of PHA Asteroid 2012 QG42

M.P.E.C. 2012-Q72, issued on 2012 Aug. 28, reports the discovery of the PHA asteroid 2012 QG42 (discovery magnitude 16.8) by Catalina Sky Survey on images taken on August 26.3 with a 0.68-m Schmidt + CCD. 

2012 QG42 has an estimated size of 200 m - 500 m (H=20.4) and it will have a close approach with Earth at about 7.43 LD (Lunar Distances) or 0.019 AU at 0510 UT on 14 Sept. 2012. This asteroid will reach an average magnitude of 13.6 around September 10-12. 2012 QG42 is a current radar target for ground based radio telescopes. Astronomers at Goldstone and Arecibo will try to observe it on September as "this object should be a really strong delay-Doppler imaging target".

It was classified as a PHA ((Potentially Hazardous Asteroid). PHA are asteroids larger than approximately 100m that can come closer to Earth than 0.05 AU. None of the known PHAs is on a collision course with our planet, although astronomers are finding new ones all the time. 

We performed some follow-up measurements of this object, remotely from the Siding Spring-Faulkes Telescope South on 2012, September 04.5, through a 2.0-m  f/10.0 Ritchey-Chretien + CCD. Below you can see our image, stack of 4x10-second exposures, taken with the asteroid at magnitude ~15.2 and moving at 4.35"/min. At the moment of the close approach on 14 September, 2012 QG42 will move at ~ 49"/min.

Below you can see a short animation showing the movement of 2012 QG42 (each frame is a 10-second exposure). Click on the thumbnail for a bigger version:

UPDATE - September 14, 2012

On mpml mailing list, Brian Warner presented the first lightcurve obtained using data provided by different amateur astronomers all around the world:

"Critter is still observable but the phase angle is now around 70° whereas most  of the data are from < 20°. The amplitude and shape of the curve may be evolving  and so it becomes more and more difficult to merge all the data into a single  set. Ideally, a data set taken over the next 24 hours from stations widely-separated in longitude would be treated as "stand alone" and would help  with modeling - LOTS!"

Below you can see the plot of the current photometry for 2012 QG42. It reveals this PHA rotates once every 24.278 hours, or 24 hours, 16 minutes, 40.8 seconds. (click on the image for a bigger version).

                                    (Credit: Brian Warner)

In the meantime the radar team announced on mpml mailing list that radar echoes from 2012 QG42 have been successfully  detected at Goldstone on September 13:

"We spent most of our time during the track improving the orbit by estimating Doppler and ranging corrections to the ephemerides. The radar data are  consistent with a slow rotation period as inferred from the lightcurves  reported by Brian Warner. We have one more track scheduled at Goldstone on Sep. 15 and four tracks at Arecibo on Sep. 14-17."

by Ernesto Guido, Nick Howes & Giovanni Sostero

Close Approach of PHA Asteroid 2012 OQ

M.P.E.C. 2012-O13, issued on 2012 July 19, reports the discovery of the PHA asteroid 2012 OQ (discovery magnitude 16.1) by J75 OAM Observatory, La Sagra on images taken on July 16.9 with a 0.45-m f/2.8 reflector + CCD.

2012 OQ has an approximate size of 120 m - 270 m meters (H=21.7) and it will have a close approach with Earth at about 7.7 LD (Lunar Distances) or 0.0197 AU at 1829 UT of July 24, 2012. At the moment of its close approach this asteroid will reach the magnitude 15.9 while moving at 51"/min.

We performed some follow-up measurements of this object, while it was still on the neocp, remotely from the H06 ITelescope network (near Mayhill, NM) on  2012, Jul. 18.3, through a 0.25-m f/3.4 reflector + CCD.

Our confirmation image, stack of 34x20-second exposures

Below you can see an animation showing the movement of 2012 OQ (each frame is a 20-second exposure). Click on the thumbnail for a bigger version:

by Ernesto Guido, Giovanni Sostero and Nick Howes

PHA Asteroid 1999 XL136

M.P.E.C. 2012-N11, issued on 2012 July  9, reports the recovery of the PHA asteroid 1999 XL136 by R. H. McNaught with the 0.5-m Uppsala Schmidt + CCD in the course of the E12 Siding Spring Survey.

1999 XL136 was discovered on December 12, 1999 by LINEAR survey and observed for roughly 1 month (last observation was of January 09, 2000). It was classified as a PHA ((Potentially Hazardous Asteroid). PHA are asteroids larger than approximately 100m that can come closer to Earth than 0.05 AU. None of the known PHAs is on a collision course with our planet, although astronomers are finding new ones all the time.

On July 08, 2012 E12 survey discovered a relatively bright (16.5 magnitude) object and reported it to NEOCP with the provisional designation TN42425. After the arrival of follow-up observations by different observers around the world, MPC has been able to link TN42425 to the Apollo-type asteroid 1999 XL136, so to identify them as the same object.

1999 XL136 has an approximate size of 472 meters (H=19.279) and according to the new calculated orbit it had a close approach with Earth at about 4.49 LD (Lunar Distances) or 0.011 AU at 1914 UT of 23 June 2012. At the moment of its close approach this asteroid reached the magnitude 12.7 and was moving at 134"/min.

We have been able to follow-up this object while it was still on the neocp, using remotely a 0.43-m f/6.8 reflector + CCD of ITelescope network located  in Nerpio (Spain - Mpc code I89).

Below you can see an animation showing the movement of the object in the sky. Click on the thumbnail for a bigger version:

Below there is  the magnitude and ephemeris table calculated by MPC website for 1999 XL136 from the day just before the close approach to its rediscovery on July 08:

Date            UT         Delta     r         El.     Ph.    V
2012 06 22 000000  0.023   0.996   30.0 149.4  19.7  
2012 06 23 000000  0.015   1.007   49.7 129.7  16.1
2012 06 24 000000  0.012   1.018   96.4  83.0   12.9
2012 06 25 000000  0.018   1.029  132.7  46.5  12.7  
2012 06 26 000000  0.027   1.039  146.5  32.6  13.2  
2012 06 27 000000  0.038   1.050  152.4  26.7  13.8
2012 06 28 000000  0.049   1.061  155.3  23.6  14.3   
2012 06 29 000000  0.060   1.072  156.9  21.8  14.7   
2012 06 30 000000  0.071   1.083  157.9  20.7  15.1 
2012 07 01 000000  0.082   1.094  158.4  20.0  15.4
2012 07 02 000000  0.094   1.104  158.7  19.5  15.7 
2012 07 03 000000  0.105   1.115  158.8  19.2  15.9 
2012 07 04 000000  0.117   1.126  158.8  19.1  16.2 
2012 07 05 000000  0.128   1.137  158.7  19.0  16.4 
2012 07 06 000000  0.140   1.148  158.5  19.0  16.6 
2012 07 07 000000  0.151   1.158  158.2  19.0  16.8 
2012 07 08 000000  0.163   1.169  157.8  19.2  17.0

Is it worth to note that despite its bright magnitude from June 23 to July 08, this asteroid has gone unnoticed through its close approach. Below you can see an animation showing the daily Sky Coverage by professional surveys (in red) and the position of the asteroid (yellow dot). Click on the thumbnail:

Please note that the full moon was on July 04 and that the surveys usually are not working 2-3 days before and after the full moon. Moreover this is the North America monsoon period and this affects some surveys productivity.

by Ernesto Guido, Giovanni Sostero and Nick Howes

New discovered PHA: 2009 ST19

This minor planet, belonging to the "Apollo" class, is also flagged as a "Potentially Hazardous Asteroid", an object that, because of its orbital parameters, might represent a possible threat of impact for planet Earth.

It has beeen discovered serendipitously by the Spanish amateur astronomer J. M. Bosch (Santa Maria de Montmagastrell, MPC#B74) on 2009, Sept. 16.2, ay magnitude about 17. At that time it was posted on the NEO-CP webpage of the Minor Planet Center as "jmbo11"; after a couple of days it was withdrawn, because it was not confirmed by any further observations.

On 2009, Sept. 22, the LINEAR sky survey picked-up a fast moving object, that was posted in the NEO-CP as "BQ24981". After some follow-up observations from various sites, on 2009 Sept. 23 the MPC published M.P.E.C. 2009-S72 informing that the two objects mentioned before were actually the same celestial body.

 
We performed some follow-up of this object on 2009, Sept.23.1, remotely from the Mayhill Station (NM) of the GRAS network. Click on the image below for a bigger version.

 

According to the NEODyS webpage this object. about 0.5-Km in diameter, made a close pass to Earth on 1980, Oct. 4, at a minimum possible distance of about 0.009 AU (nominal distance of about 0.04 AU).

Congratulations to J. M. Bosch for his find.

E. Guido, G. Sostero, P. Camilleri, M. Jaeger, E. Prosperi, W. Vollmann