Quasi-satellite of Earth

As it orbits the Sun, {{mp|2016 HO|3}} appears to circle (highly elliptically) around Earth as well. The object is beyond the Hill sphere of Earth and the Sun exerts a much stronger pull on it than Earth does. Although it is too distant to be considered a true natural satellite of Earth, it is the best and most stable example to date of a near-Earth companion, or quasi-satellite.^[5]

"Since {{mp|2016 HO|3}} loops around our planet, but never ventures very far away as we both go around the Sun, we refer to it as a quasi-satellite of Earth", said Paul Chodas, manager of NASA's Center for Near-Earth Object (NEO) Studies at the Jet Propulsion Laboratory in Pasadena, California.^[6]

In its yearly trek around the Sun, asteroid {{mp|2016 HO|3}} spends about half of the time closer to the Sun than Earth is (that is, the asteroid is inside the Earth's orbit) and passes ahead of our planet, and about half of the time farther away (crosses outside Earth's orbit), causing it to fall behind. Its orbit is also tilted a little, causing it to bob up and then down once each year through Earth's orbital plane. In effect, this small asteroid is caught in a game of leap frog with Earth that will last for hundreds of years.^[6]

The asteroid's orbit also undergoes a slow, back-and-forth twist over multiple decades. "The asteroid's loops around Earth drift a little ahead or behind from year to year, but when they drift too far forward or backward, Earth's gravity is just strong enough to reverse the drift and hold onto the asteroid so that it never wanders farther away than about 100 times the distance of the moon", said Chodas. "The same effect also prevents the asteroid from approaching much closer than about 38 times the distance of the moon. In effect, this small asteroid is caught in a little dance with Earth."^[6]As of now, it has by far the most stable quasi-satellite of Earth discovered, in terms of orbit.

Physical characteristics

The size of {{mp|2016 HO|3}} has not yet been firmly established, but it is likely about {{convert |40|–|100|m|ft|abbr=on}}.^[6] Based on an assumed standard albedo for stony S-type asteroids of 0.20 and an absolute magnitude of 24.3, it measures {{convert|41|m|ft|sp=us}} in diameter.^[8]

Photometric observations in April 2017 revealed that {{mp|2016 HO|3}} is a fast rotator. Lightcurve analysis gave a rotation period of {{convert |0.467|±|0.008 |hour|minute|abbr=off}} and a brightness variation of {{val|0.80|0.05}} magnitude ({{small|U=2}}).^[8]{{refn|group=lower-alpha|name=lcdb-Reddy-2018}}

Discovery and naming

Asteroid {{mp|2016 HO|3}} was first spotted on 27 April 2016, by the Pan-STARRS 1 asteroid survey telescope on Haleakalā, Hawaii, operated by the University of Hawaii's Institute for Astronomy and funded by NASA's Planetary Defense Coordination Office.^[6] As of 2018, the object has not been named.^[2]

Gallery

See also

• Arjuna asteroid
• Natural satellite
• Quasi-satellite
• 3753 Cruithne
• 6Q0B44E
• {{mpl|2001 GO|2}}
• {{mpl|2002 AA|29}}
• {{mpl|2003 YN|107}}
• {{mpl|2006 JY|26}}
• {{mpl|2006 RH|120}}
• {{mpl|2012 FC|71}}
• {{mpl|2013 BS|45}}
• {{mpl|(419624) 2010 SO|16}}
• {{mpl|(436724) 2011 UW|158}}
• {{mpl|2002 VE|68}}, a quasi-satellite of Venus, and the first quasi-satellite discovered around any major planet

Notes

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References