Asteroid cruised close to Earth on Friday
This undated image released by NASA and taken by the NASA Dawn spacecraft shows the south pole of the giant asteroid Vesta. Vesta is much larger than the new asteroid that shot by Earth this Friday, 2019 NJ2. (AP Photo/NASA)
An asteroid was expected to travel closely past the Earth on Friday, but according to data collected by the Center for Near Object Studies, this extraterrestrial tourist is only one of many.
The asteroid, called 2019 NJ2, is somewhere between 28 and 63 metres in diameter, and is travelling at 48,456 kilometres per hour, or 13.46 km per second.
The Center for Near Object Studies (CNEOS) tracks, as the name suggests, near-earth objects (NEOs, for short). A near-earth object is an asteroid or comet that will be passing close to the Earth’s orbit as it hurtles through space, tugged about by the gravitational pull of the planets and objects around it.
Although it sounds frightening, the Earth has likely had millions of NEOs streak safely past it over its long, long lifetime -- what is considered “close” in astronomical numbers is far from what the average person would expect.
This newest asteroid will be between 5 million and 5.1 million kilometers away from the Earth at its closest brush with our planet.
To put this in perspective, the Earth is approximately 225 million km away from Mars, on average (their respective orbits mean that sometimes they are closer and sometimes they are farther away from each other).
The asteroid is classified as an Apollo, which is a type of asteroid that crosses Earth’s orbit in a fashion similar to the first asteroid given that name, which was discovered in 1862. Apollo-type asteroids have orbital patterns larger than Earth’s, but they cross over the same path that Earth travels around the sun.
But how often do asteroids pass by us as we spin unaware through the cosmos?
CNEOS has records on their website dating back to 1970 that update the cumulative total of known NEOs every month. The most recent cumulative data is from July 15, 2019, and lists 20,552 as the number of NEOs the Center has observed since starting to take records.
More than 500 asteroids have passed within 7.5 million km of the Earth this year since January alone.
But only around 30 NEOs have passed within one lunar distance from the Earth in the same period of time. One lunar distance is a unit of measurement based on the distance between the centre of the Earth and the moon: roughly 384,000 km.
Asteroids are only classified as PHAs (potentially hazardous asteroids) by CNEOS if they are not only passing closer than 7.5 million km to the Earth, but are also large enough to do significant damage if there was an impact. Asteroids under 140 metres in diameter fall below the cut-off, so our new asteroid -- at a measly 63 metres diameter according to the highest estimation -- is not going to be causing any dinosaur-level extinctions anytime soon.
The two NEOs that have passed the closest to Earth since the start of 2019 are 2019 JH7, which came within 72,960 km on May 16, and was three- to seven-metres long, and 2019 AS5, which came within a shocking 15,360 km of the Earth on Jan 8, but was only about one- to two-metres long.
Although the vast majority of these NEOs do not pose a high threat level to the Earth, NASA did warn us this past May that meteors could be more dangerous than we think. In December of 2018, a meteor exploded over the Bering Sea with a force 10 times that of the Hiroshima atomic bomb, but was largely unnoticed due to the remote location.
This is the first time that 2019 NJ2 has passed closely to Earth, but it is predicted to do so once again 100 years from now, on July 7, 2119.