Closet Asteroid to Sun identified, Completes revolution in just 165 days

Asteroid near Venus

Astronomers have discovered an asteroid looping through the inner solar system on an exotic orbit. The unusual object is among the first asteroids ever found whose orbit is confined almost entirely within the orbit of Venus. The asteroid’s existence hints at potentially significant numbers of space rocks arcing unseen in uncharted regions nearer to the sun.

A state-of-the-art sky-surveying camera, the Zwicky Transient Facility, or ZTF, detected the asteroid on January 4, 2019. Designated 2019 AQ3, the object has the shortest «year» of any recorded asteroid, with an orbital period of just 165 days. It also appears to be an unusually big asteroidal specimen.

«We have found an extraordinary object whose orbit barely strays beyond Venus’ orbit—that’s a big deal,» said Quanzhi Ye, a postdoctoral scholar at IPAC, a data and science center for astronomy at Caltech. Ye called 2019 AQ3 a «very rare species,» further noting that «there might be many more undiscovered asteroids out there like it».

ZTF is installed on the 48-inch Samuel Oschin Telescope at the Palomar Observatory, located about 122 miles south-east of Los Angeles.

A history of asteroidal and cometary successes

Finding NEOs before they find us has long been a major topic at Caltech / IPAC. The center has led the science operations and data processing for NASA’s Wide-field Infrared Survey Explorer and NEOWISE missions since their launch in 2009. This asteroid hunter has discovered more than 34,000 new asteroids, including nearly 300 NEAs.

Tracking down 2019 AQ3

The story of how researchers nailed down 2019 AQ3’s orbit begins with Ye noting the object in ZTF’s images on January 4, 2019. Ye reported the object to the IAU Minor Planet Center, the official worldwide organization charged with gathering data on sun-orbiting objects that are not full planets, such as asteroids and comets. Ye then spent some time mining the ZTF images taken before and after this date to improve projections of the asteroid’s orbit.

Two days later, Marco Micheli, a scientist at the European Space Agency, pointed out the target’s uniqueness to the global astronomical community. Multiple other telescopes observed 2019 AQ3 on January 6 and 7, further documenting its uniqueness. A dig through the archives of the Pan-STARRS 1 telescope at the Haleakalā Observatory on the island of Maui, Hawaii, turned up evidence of 2019 AQ3 going back to 2015. With those data in hand, astronomers confidently mapped the object’s complete path around the sun.

The orbit, as it turns out, is angled vertically, taking 2019 AQ3 above and below the plane where the planets run their laps around the sun.

“The origin of this asteroid is an intriguing and open question,” said Ip. “With every additional object, we get closer to formulating and testing models about that origin, and about the history of our Solar System.”