2019 OK

Near-Earth asteroid 2019 OK is a football-field-sized asteroid that safely passed close to Earth on July 24, 2019, with very little warning.

During its close pass by Earth, the asteroid came within about 40,000 miles (65,000 kilometers) of the planet’s surface, or one-fifth the distance to the Moon. 2019 OK is estimated to measure between 195 and 425 feet (60 to 130 meters) in diameter.

Other asteroids have passed closer to Earth — and a few small asteroids have impacted our atmosphere soon after they were discovered — but none has been as large as asteroid 2019 OK. This makes it the largest asteroid known to pass so close to Earth.

“An asteroid of this size coming this close to Earth is a pretty Unusual event — on the order of about twice a century,” said Paul Chodas, manager of NASA’s Center for Near-Earth Object Studies at the Jet Propulsion Laboratory in Pasadena, California.

If 2019 OK had entered the Earth’s atmosphere, and exploded over land, like the 2013 fireball over Chelyabinsk, Russia the blast could have devastated an area roughly 50 miles (80 kilometers) across. If such an unlikely event were to occur over an ocean, the sea would probably absorb most of the energy from the impact.

Asteroid 2019 OK was named by the International Astronomical Union’s Minor Planet Center using the center’s designation for asteroids based on the date of discovery.

Asteroid 2019 OK was first detected by amateur astronomers Cristovao Jacques, Eduardo Pimentel and Joao Ribeiro de Barros at the Southern Observatory for Near-Earth Asteroids Research (SONEAR) in the state of Minas Gerais, Brazil. It was spotted the same day it passed close to Earth.

There were several factors that made it hard to detect the asteroid. Its orbit is highly elliptical and takes it from within the orbit of Venus to well beyond the orbit of Mars. The time it spends near Earth and is detectable by current telescope capabilities is relatively short.

Astronomers hunting asteroids and comets close to our planet — near-Earth objects or NEOs — watch for movement against a background of stars. If an object doesn’t appear to be moving, it’s hard to tell if a point of light is an asteroid or a star.

As asteroid 2019 OK approached Earth, its position in the sky made it look like it wasn’t moving much until the last few days when its motion finally became apparent in the sky images.

Asteroid 2019 OK is estimated to be 195 to 425 feet (60 to 130 meters) in diameter.

It orbits the Sun at distances ranging from about 0.46 astronomical units (AU) to 3.4 AU. One astronomical unit is the distance from the Sun to Earth, or an average of 93 million miles (150 million kilometers). This means the asteroid’s distance from the Sun ranges from about 42.8 million miles (68.9 million kilometers) to about 316 million miles (509 million kilometers).

Asteroid 2019 OK completes an orbit of the Sun every 2.72 years, or once every 993 days. Its highly elliptical orbit takes it from within the orbit of Venus to well beyond the orbit of Mars.

Asteroid 2019 OK is classified as an Apollo asteroid, a class of objects named for asteroid 1862 Apollo. These asteroids have an orbit that is larger than Earth’s orbit around the Sun and their path crosses Earth’s orbit.

The 2019 flyby is the closest asteroid 2019 OK will come to Earth for at least the next 200 years.

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