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Royal Astronomical Society of New ZealandThe Brighter Asteroids in 2009: (7) Iris |
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Royal Astronomical Society of New ZealandThe Brighter Asteroids in 2009: (7) Iris |
Chart showing path of Iris from March to May 2009 Positions of Iris near its time of opposition 2009
Iris will be in Sagittarius when it brightens to magnitude 9.5 early in June 2009. It is at opposition on July 4 with a magnitude 8.7. After opposition it fades again back to 9.5 in mid August.
The distance of Iris from the Sun varies between 1.833 and 2.937 AU, so that at the most favourable oppositions the asteroid is about 0.83 AU from the Earth. At the 2009 opposition the distance of Iris from the Sun is 2.58 AU and 1.56 AU from the Earth. So the 2009 opposition is an average sort of affair.
At the poorest oppositions, eg in May 2012, Iris' brightest magnitude is 9.5. At the best oppositions it can be as bright as 6.7. No such opposition will occur in the near future.
Iris's diameter is 200 km. Its orbital period is 3.68 years, the orbit being inclined at 5.527° to the ecliptic.
Iris was discovered in 1847 on August 13 by J R Hinds in London. This was his first asteroid discovery
The chart is a southern hemisphere view with north at the bottom and east to the right. Stars to magnitude 9.0 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.
| Date 2009 | R.A hr min |
Dec ° ' |
Mag | Const |
| Jun 4 | 19 18.9 | -19 50 | 9.6 | Sagittarius |
| Jun 14 | 19 11.9 | -19 38 | 9.3 | Sagittarius |
| Jun 24 | 19 02.8 | -19 29 | 9.0 | Sagittarius |
| Ju1 4 | 18 52.2 | -19 21 | 8.7 | Sagittarius |
| Jul 14 | 19 41.5 | -19 15 | 8.9 | Sagittarius |
| Jul 24 | 18 31.6 | -19 09 | 9.1 | Sagittarius |
| Aug 3 | 18 23.9 | -19 05 | 9.3 | Sagittarius |
| Aug 13 | 18 18.8 | -19 01 | 9.5 | Sagittarius |
| Aug 23 | 18 16.9 | -19 00 | 9.7 | Sagittarius |
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