Asteroid Iris 7 will be opposite the sun, an arrangement called opposition, on the evening of tonight, April 30, offering skywatchers an excellent opportunity to spot this fascinating space rock.
The large main-belt asteroid which orbits the sun between Mars and Jupiter will be above the horizon for the majority of the night and into the morning of May 1. Regardless of position across the globe, Iris 7 will reach its highest in the night sky around midnight local time, and it will be seen in the constellation of Libra.
From New York City Iris 7 will be visible from 22:33 EDT (0233 GMT) when it rises to 21 degrees over the horizon to the southeast, according to In the Sky. The asteroid will reach its highest in the night sky at around 00:46 EDT (0446 GMT). Iris 7 will disappear at around 02:59 EDT (0659 GMT) when the asteroid sinks to below 21 degrees over the horizon to the southwest.
This ideal time to spot Iris 7 occurs as the asteroid makes its closest approach to the point in the sky over Earth that is exactly opposite the sun. The three celestial bodies are in a straight line with our planet in the middle of Iris 7 and the sun. Our star sinks to its lowest point below the horizon at around 12 am, meaning the point opposite it is at its highest at the same time.
During its Perigee Iris 7 will come to within around 179 million miles of Earth reaching a brightness of magnitude of 9.6. This means the asteroid will still be quite faint and thus isn't visible to the naked eye, thus requiring binoculars or a telescope to be seen.
Iris 7 was first discovered in 1846 by J. R Hind and was the seventh asteroid to be discovered. The asteroid is believed to be around 124 miles (200 kilometers) wide and it has an extremely reflective surface thanks to its composition of nickel-iron metals, magnesium, and iron silicates.
This composition and the fact that the 3.7 Earth-year orbit of Iris 7 brings it close to the sun means this asteroid is the fourth brightest space rock in the main asteroid belt, after Vesta, Ceres, and Pallas.
If you are hoping to catch a look at the Iris 7 while the asteroid is in opposition, our guides to the best telescopes and binoculars are a great place to start.
Editor's Note: If you snap an image of the asteroid Iris 7, and would like to share it with Space.com’s readers, send your photo(s), comments, and your name and location to firstname.lastname@example.org.
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Robert Lea is a science journalist in the U.K. whose articles have been published in Physics World, New Scientist, Astronomy Magazine, All About Space, Newsweek and ZME Science. He also writes about science communication for Elsevier and the European Journal of Physics. Rob holds a bachelor of science degree in physics and astronomy from the U.K.’s Open University. Follow him on Twitter @sciencef1rst.
Okay, I checked Starry Night Pro Plus 8 and Stellarium 23.1 for my location near 2330 EDT tonight. Iris 7 is some 9.4 to 9.6 apparent magnitude in Virgo. This asteroid will be very difficult to see, unless you have some good equipment and can locate its exact position among the stars.Reply