Asteroid 2018 UA flew past Earth at 0.04 LD, 4th closest on record

A newly discovered asteroid designated 2018 UA flew past Earth at a very close distance of about 0.04 LD / 9.14e-5 AU (15 360 km / 9 544 miles) above Earth's surface. This is the closest known asteroid to flyby Earth since the start of the year and 4^th closest on record. Interestingly, this object was discovered about 90 minutes before its close approach. At best, it would produce a nice fireball and small meteoroids.

This object belongs to the Apollo group of asteroids. Its estimated diameter is between 2.5 and 5.5 m (8 and 18 feet).

2018 UA, previously known as ZU1CE58, was first observed at Catalina Sky Survey on October 19, about 90 minutes before its closest approach at 14:46 UTC today.

The object flew past us at a speed (relative to the Earth) of 14.14 km/s.

This is the 3^rd known asteroid to flyby Earth within 1 lunar distance since October 7 and 56^th this year.

2018 AU made history with 4^th closest flyby of any known asteroid on record.

The closest known asteroid flyby took place at 19:39 UTC on February 4, 2011 (2011 CQ1) at 0.03 LD / 7.92e-5 AU, followed by 2008 TS26 at 03:30 UTC on October 9, 2008 (2008 TS26) at 0.03 LD / 8.44e-5 AU, and 2004 FU162 at 15:35 UTC on March 31, 2004 at 0.03 LD / 8.63e-5 AU.

It is also the second largest known asteroid to fly by within 0.04 LD on record.

Note: 2018 data valid 16:30 UTC, October 19. Another close flyby was reported at 17:00 UTC: 2018 UL (0.57 LD / 0.00148; size 4.1 – 9.1 m / 13.4 – 30 feet).

References:

Asteroid 2018 UA at Minor Planet Center; at CNEOS

Featured image: ZU1CE50 flyby simulation – October 19, 2018. Credit: Tony Dunn / OrbitSimulator.com