[BAA-ebulletin 00625] Close-approach of asteroid 2005 YU55

[Rick]

[BAA-ebulletin 00625]  Close-approach of asteroid 2005 YU55
(c) 2011 British Astronomical Association -- http://www.britastro.org/

Seen from the UK on the evening of Tuesday, November 8/9, a 400-metre size asteroid 2005 YU55 will pass within 0.85 lunar-distances of us travelling at a speed of 13.7 km/s relative to the Earth.  This encounter will be the closest known for an asteroid of this size between the years, 1976 and 2028. So in this respect, it is a once in a 52-year opportunity to witness this particular skirmish.

It should first become visible from the UK and Europe on Tuesday evening, low in the west mainly in Aquila, passing 22 degrees south-west of Comet Garradd (C/2009 P1).  It should prove fascinating to follow as it approaches.  Seen from southern England (Dorset), it may be first detectableusing a CCD camera and large telescope at about 18:00UT some 23 degrees altitude in the south-west direction at about magnitude 15 moving at 5 "/sec. It will brighten by about a factor of 10 over the next 4 hours so that by 22:00UT it will be 12th magnitude and moving at around 8 "/sec, i.e. crossing the sky at a rate of 1 Moon-diameter every 3.6 minutes.  Even exposures of a few seconds will show the asteroid as a trail and only telescope mounts set up to track moving objects will be able to register it as a point source. It will attain 11th magnitude at closest approach (Nov 8 at 23:28UT) at an altitude of just 6 degrees (as seen from Dorset) and thereafter will set below the western horizon.  With a very high apparent speed (reaching almost 9 "/sec), the object will be visible through large telescopes (25cm or greater) looking like a moving point of light crossing the field of view in a minute or two. Quite an observing challenge!

2005 YU55 will be much better placed for observers and easier to see on the evening of November 9/10 when at about 18:00UT it will be 12th magnitude and moving at <1 "/sec in the east close (12 degrees away) to the nearly full Moon.  Martin Mobberley has kindly generated a finder chart showing the general position of the asteroid for the nights of Nov 9/10, 10/11 and 11/12.  The chart can be found at: http://martinmobberley.co.uk/images/2005YU55chart_mpm.jpg

If you are planning to observe then you will need to generate an ephemeris for a geographical location within a few hundred kilometres of your observing site.  You may find the Minor Planet Center website convenient to use for this purpose, located at: http://minorplanetcenter.net/iau/MPEph/MPEph.html

Be sure to enter an observatory code in the relevant box: "J95" would be a good one to use by anyone in southern England. You will have to pick a short 'ephemeris interval' say 5 minutes so that you can point your telescope at a convenient spot which the asteroid will reach some minutes after the telescope has been trained on a suitable R..A. and Dec. Enter "2005 YU55" in the large box and an ephemeris start date using the following format, "2011 11 09 1800".

The object was last observed in 2010 April when the Arecibo radio telescope was used to generate a radar image of the near-spherical object, and which was shown to be very dark and a slow rotator turning just once every 18 hours or so.  See for example: http://www.jpl.nasa.gov/asteroidwatch/newsfeatures.cfm?release=2010-144

Although a potentially hazardous object, we do know that this is the closest approach the object will make to the Earth during the next 100 years.

All observations welcome. Good luck with the weather,

Richard Miles
Director, Asteroids and Remote Planets Section
BAA

[Rick]

Sky and Telescope's take...

Earth is about to be visited by the largest close-approaching asteroid on record. Known as 2005 YU55, it is about a quarter mile (400 meters) across, round, and quite dark. When it comes closest to us, at 6:28 p.m. EST (23:28 Universal Time) on November 8th, it will be 198,000 miles (319,000 km) from Earth's surface -- closer than the Moon's orbit. Professional astronomers around the world will closely follow the asteroid as it glides across the sky.

See http://www.skyandtelescope.com/about/pressreleases/133357483.html

[Rick]

The University of Arizona's version...

Discovered by a University of Arizona astronomer six years ago, a city-block-sized space rock will race past the Earth closer than the moon in what will be the closest encounter of an object of this size in more than 60 years.

When an asteroid the size of a city block zips past the Earth about 29,000 miles per hour on Nov. 8, it will seem like an encounter with an old acquaintance to Univeristy of Arizona astronomer Robert McMillan.

Six years ago, McMillan was taking images of the night sky with an 83-year-old telescope on Kitt Peak searching for asteroids, chunks of rock that weren't swept up into one of the nascent planets during the formation of our solar system and have traveled around the sun ever since. That is how he discovered 2005 YU55.

More: http://uanews.org/node/43045

[Mike]

As usual when any astronomical event occurs we won't see a thing

[Rick]

Yeah, it helps if you've got NASA's resources...

PASADENA -- NASA's Deep Space Network antenna in Goldstone, Calif. has captured new radar images of Asteroid 2005 YU55 passing close to Earth.

The asteroid safely will fly past our planet slightly closer than the moon's orbit on Nov. 8. The last time a space rock this large came as close to Earth was in 1976, although astronomers did not know about the flyby at the time. The next known approach of an asteroid this size will be in 2028.

The image was taken on Nov. 7 at 11:45 a.m. PST, when the asteroid was approximately 860,000 miles (1.38 million kilometers) away from Earth. Tracking of the aircraft carrier-sized asteroid began at Goldstone at 9:30 a.m. PDT on Nov. 4 with the 230-foot-wide (70-meter) antenna and lasted about two hours, with an additional four hours of tracking planned each day from Nov. 6 - 10.

See http://www.nasa.gov/mission_pages/asteroids/multimedia/yu55-20111107.html

[MarkS]

As usual when any astronomical event occurs we won't see a thing

It proves, yet again, that astronomical events certainly do affect the weather!

[Rick]

Asteroid Ping experiment November 8 for suitably equipped stations

On Tuesday, November 8, at 6:28 p.m. EST, an asteroid the size of an aircraft carrier will soar past our planet at a distance closer than the Moon... and NASA scientists will be watching! Suitably equipped amateur radio stations may enjoy looking over their shoulder ...

The 400 meter diameter near-Earth asteroid 2005 YU55 will be making a 0.85 lunar distance flyby of Earth on November 8. Michael Busch at the UCLA Department of Earth and Space Sciences notes this may offer an opportunity for amateur satellite operators to observe the fly-by.

UCLA will be conducting an extensive campaign of radar observations with the Arecibo Observatory, the Deep Space Network Goldstone facility, and the Green Bank Telescope and the Very Long Baseline Array.

More: http://www.southgatearc.org/news/november2011/asteroid_ping_experiment.htm