The Asteroids, also known as Minor Planets, are small "planets" orbiting the Sun, mostly between Mars and Jupiter. The largest, Ceres, has a diameter of about 933 km, most are much smaller. Over one hundred thousand have had their orbits described, but only a few of the larger ones are bright enough to be picked up in binoculars. Mostly this will be only for a month or two either side of opposition, when the asteroid is on the opposite side of the Earth to the Sun. It is then at its closest to the Earth and is also fully lit by the Sun as seen from the Earth.
Details are given of the asteroids which reach an opposition magnitude 9.0 or brighter during 2012. At this magnitude an object should be visible in 50 mm aperture binoculars from a dark site, with clear skies and without too much Moon light.
For each asteroid charts are included showing its path. The charts show stars to magnitude 9.5 and each has a circle on it representing a 5° field. This is a typical field for 8x50 or 10x50 binoculars. In addition there is a table showing the position (right ascension and declination) of the asteroid at 10 day intervals while it is at magnitude 9.5 or brighter.
Charts are for the southern hemisphere with south at the top and east to the right. Anyone using a chart in the northern hemisphere would need to turn it upside down. The charts would give a "true" view when the asteroid is due north. When to the east or west, the sky would appear to be rotated, clockwise if to the east and anticlockwise when to the west, as seen from the southern hemisphere.
The table below lists all asteroids which meet the criterion of magnitude at their opposition in 2012. The magnitude given is that at opposition, which is usually when the asteroid is at its brightest.
For further details of asteroids visit the JPL small-body database browser.
Asteroids with opposition magnitudes 9 or brighter during 2012
|Asteroid||Opposition date||Magnitude||Range of dates brighter than 9.5|
|(15) Eunomia||2011 Nov 29||7.9||2012 Aug 18 to 2012 Feb 12|
|(433) Eros||2012 Feb 7||8.6||2011 Dec 29 to 2012 Mar 11|
|(5) Astraea||2012 Mar 11||9.0||2012 Feb 20 to Mar 29|
|(11) Parthenope||2012 Sep 3||9.0||2012 Aug 10 to Sep 24|
|(2) Pallas||2012 Sep 24||8.3||2012 Jul 28 on through 2013|
|(4) Vesta||2012 Dec 9||6.4||At all times.|
|(1) Ceres||2012 Dec 18||6.7||At all times.|
|(9) Metis||2013 Jan 1||8.5||2012 Nov 18 to 2013 Feb 9|
Close approaches by AsteroidsAs at September 2011 the closest approach reported of an asteroid to the Earth during 2011 was on February 4 when a small body designated at 2011 CQ1 was some 11900 km from the Earth's centre, so about 5500 km from the Earth's surface. In addition there have been 14 other bodies which have come closer to the Earth than the moon. Most of these were in the first half of the year, the second half year list is apparently not yet complete. The majority of these asteroids were discovered only very close to the time of their close approach, in some cases after! The closest approach at present known for the rest of 2011 is by 2005 YU55 on November 9 at a distance of about 326000km. Further details of there and other close fly-bys can be found at the JPL near earth object web site
At present the closest approach predicted for 2012 is on May 20, when 2010 KK37 passes us at a distance of about 343 000km. The average distance of the moon is 384 000km. Others close passes are likely to be discovered nearer to the date they occur.
The closest approach of an asteroid predicted for future years is on 13 April 2029 (14 April in NZ),when (99942) Apophis will pass at about 35000km, one-tenth of the distance of the Moon. This may well be bright enough to be briefly visible by eye. Unfortunately for NZ its time of closest approach is estimated to be about 10 am.
A 33 year list of predicted close approaches can be found at the Harvard IAU site. The information above was obtained from this site.