Near Earth Orbit (NEO) Asteroid Pass

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Near Earth Orbit (NEO) Asteroid Pass

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1998 OR2 - Near Earth Orbit (NEO) Asteroid Pass
Joe Cali

In late April and early May, an asteroid, designated 1998 OR2 will pass moderately close to Earth. Perigee distance is about 6 million km or 15 x Earth-Moon distance.
1998-OR2-orbit-animation.gif
Source: NASA Solar System Orbit Explorer

The object travels approximately 80 degrees over a 2 week period centred on perigee. Perigee [Apr 29] favours the southern hemisphere with the object at a declination of 23 south. However, the asteroid, a 14th magnitude object at time of writing (April 9) is about to enter Cancer heading south. It crosses the celestial equator on April 25 when it will be magnitude 11.5 and quite observable from the northern hemisphere.
1998 OR2 PATH APRIL 09-MAY 7 copy.jpg
Source: Starry Night Pro v8

At closest approach, 22:00 EST on April 29, the asteroid will move through the constellation of Hydra at about 1o every three hours against background stars, this is approximately 2/3 the rate that the Moon moves against background stars. The magnitude at closest approach is 10.8. This is not an event for the casual observer, more of an expert level or at least for an intermediate level user with a small to medium size scope. Magnitude 10.8 is near the visual magnitude limit for a pair of 7x50mm binoculars. Magnitude 11 is moderately easy in an 80mm refractor. Easier in anything over 100mm aperture.

These objects are so small that they look like a star so the easiest way to visually identify and observe these objects is by observing the motion as it passes close to a nearby star field of similar brightness stars. On April 29, at the very sociable hours of 8:30-10:00pm, 1998 OR2 passes through a field of similarly bright stars. During this observing window, the asteroid passes within 50” of a magnitude 10.7 star at 21:15 EST. In my opinion, this is the prime time to observe the motion of this object.
1998-OR2-PATH-APRIL-29-overlays.jpg
Source: Starry Night Pro v8


More detail of orbital elements, ephemerides are available in an article on my website http://joe-cali.com.
You will note that the ephemerides have been calculated for Canberra. Time zone is UT+10. Parallax to the northern hemisphere is less than 0.1 degrees. If you don't want to do the time conversion either enter the Besselian elements into your planetarium app or run the NASA Horizons Web App to generate an ephemeris for your location.

Enjoy

Joe
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Amateur astronomer since 1978...................Web site : http://joe-cali.com/
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