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The Brighter Asteroids in 2012:     (433) Eros



Charts showing path of Eros from December 2011 to March 2012       Positions of Eros for 2012


Eros at Opposition in 2012

Eros is at opposition in early February when it will reach magnitude 8.55 from February 1 to 5 and be 8.6 or brighter between January 27 and February 11. It is actually closest to the Earth on January 31 with a distance of 0.179 Astronomical Units, just under 27 million kilometres. This is about 70 times the mean distance of the Moon. Hence Eros is a Near Earth Asteroid so being the first NEA to be discovered.

Full moon is on February 8 (NZDT) so there will be considerable moonlight at the time Eros is brightest. However Eros is always some distance from the moon so the asteroid is likely to be visible in binoculars.

Eros first brightens to magnitude 9.5 on December 29 as it moves from Leo Minor into Leo. It will then be well north of the celestial equator and low in New Zealand skies. Over the next few weeks during the period near opposition, Eros will be moving to the south as seen from the Earth, rather than the more normal west. After being in Leo, Eros will move into Sextans on January 20 and then cross Hydra during February. It will move into Antlia at the beginning of March as its magnitude drops back to 9.5.

The southerly motion will bring it higher into southern hemisphere skies. It is just south of the equator when brightest at the beginning of February. The north to south motion is similar to that of (1036) Ganymed, the largest NEA, which was at opposition at the end of October 2011 and brightened to magnitude 8.3.

Discovery and History of Eros.
Eros was discovered by G. Witt at Berlin on 1898 August 13. It was also observed a little earlier the same night by A. Chalois at Nice. It was the first asteroid to be discovered that crossed the orbit of Mars to make a close approach to the Earth. At its opposition in 1900/1901 and again at the close approach in 1931 the parallax of was used to determine the distance of the Sun. The parallax is the apparent change in position of Eros as seen from different parts of the Earth.

The previous best determinations of the Sun's distance had been made by observations of the transit of Venus in the 18th and 19th centuries. So it seems appropriate that Eros should make another close approach in 2012 with another transit of Venus also occurring in June. The determinations of the Sun's distance using Eros remained the most accurate until radar measures later in the 20th century.

Eros was visited by the NASA spacecraft NEAR Shoemaker in 2000 when the elongated shape of the asteroid was imaged. In 2001 it descended to the surface. Eros is roughly cylindrical with dimensions about 34km x 11km x 11 km.

Eros's orbital period is 1.761 years, just over 643 days. Its distance from the Sun varies from 1.134 to 1.78 AU with a mean distance 1.46 AU. Thus at aphelion it is beyond the orbit of Mars. The eccentricity of the orbit is 0.223 and its inclination to the ecliptic is 10.8°.

Favourable oppositions of Eros always occur close to the end of January. At that time the Earth is 0.985 AU from the Sun. At the closest oppositions Eros is 0.149 AU from the Earth. The last close opposition of Eros was 1975 January 23 with at a distance of 0.151 AU, the next is 2056 January 24 at 0.150 AU. The close oppositions occur alternately at intervals of 37 and 44 years.


Charts showing the path of Eros from December 2011 to March 2012.

The charts show a southern hemisphere view of the sky with north at the bottom and east to the right. Stars to magnitude 9.5 are shown, which is about the limiting magnitude of 50 mm aperture binoculars. The circle on the chart represents a field of view 5° in diameter, a fairly typical field of view for binoculars.

There are 4 charts in all covering the time from the end of December 2011 to March 2012 during which Eros moves south through 60°. The stars at the top of one chart are repeated at the bottom of the next. On each chart Eros moves from bottom to top.

Path of Eros 2011 to 2012

End of December to early January

Eros, moving south, crosses from Leo Minor to Leo at the end of December 2011. It brightens to magnitude 9.5 on December 29 and to 9.0 b January 11.

Eros is about 3.8° from ζLeo, magnitude 3.42, on January 2
and 4° from γLeo, magnitude 2.23, on January 6.
Path of Eros in 2011 and 2012.

Path of Eros 2012

Mid January

Eros moves from Leo into Sextans on January 21. By then it will be at magnitude 8.7.

Eros is about 8° from Regulus, αLeo, magnitude 1.41, on January 15.
Path of Eros in January 2012.

Path of Eros 2012

Late January to early February

Eros is at its brightest during the period covered by this chart. It crosses into Hydra from Sextans on February 6 when it will be at magnitude 8.55.

Eros is about 1.6° from βSex, magnitude 5.06, on January 27. and 3° from λHya, magnitude 3.60, on February 8
Eros in early February 2012.

Path of Eros 2012

Early February to March

Eros crosses Hydra during February and moves into Antlia early March. By then its motion through the stars will have slowed. It fades from magnitude 8.6 on February 10 to 9.5 by March 11. The chart also shows the path of Eros during the rest of March as it loops and starts moving back to the east. On March 31 its magnitude will be 10.3

Eros is about 2° from μHya, magnitude 3.8, on February 11 and 12.
On March 11, when at magnitude 9.5, Eros will be only 5.5' from θAnt, magnitude 4.79
Eros in February and March 2012.

Chart prepared using GUIDE 8.0. Program produced by Project Pluto.


Positional data for Eros, from the end of December 2011 to February 2012

Also shown are the distance of Eros from the Earth and the Sun. Distances are given in Astronomical Units, AU. 1 AU is the average distance of the Earth from the Sun, million 149.6km. The moon's average distance is 0.00257 AU, 384 400km.
Date
2012
R.A
hr min
Dec
 °  '
 Mag.  Earth
dist. AU
Sun
dist. AU
Const
2011 Dec 22 10 15.4 +32 22 9.8 0.2631.151Leo Minor
2011 Dec 27 10 24.3 +29 01 9.8 0.2451.145Leo Minor
Jan 1 10 31.4 +25 13 9.4 0.2291.140Leo
Jan 6 10 36.6 +20 57 9.2 0.2141.137Leo
Jan 11 10 39.8 +16 13 9.0 0.2021.135Leo
Jan 16 10 41.1 +11 06 8.9 0.2021.135Leo
Jan 21 10 40.2 +05 41 8.7 0.1851.134Sextans
Jan 26 10 37.4 +00 08 8.6 0.1801.136Sextans
Jan 31 10 32.8 -05 20 8.6 0.1791.138Sextans
Feb 5 10 26.8 -10 28 8.6 0.1801.143Sextans
Feb 10 10 19.7 -15 04 8.6 0.1851.148Hydra
Feb 15 10 12.2 -18 59 8.7 0.1921.154Hydra
Feb 20 10 04.6 -22 08 8.8 0.2011.162Hydra
Feb 25 09 57.6 -24 30 9.0 0.2121.171Hydra
Mar 1 09 51.6 -26 11 9.2 0.2261.180Hydra
Mar 6 09 47.2 -27 16 9.4 0.2411.191Antlia
Mar 11 09 44.3 -27 52 9.5 0.2571.202Antlia
Mar 16 09 43.1 -28 03 9.7 0.2761.214Antlia
Mar 21 09 43.5 +27 56 9.9 0.2951.227Antlia

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