ST. GEORGE — On Saturday, five asteroids are expected to fly by Earth, ranging in size from a school bus to the size of a jumbo jet, and one approach is so close it is only half the distance between the Earth and the moon.
A majority of asteroids, which are rocky fragments left over from the formation of the solar system that took place more than 4.5 billion years ago, orbit the sun along a belt situated between Mars and Jupiter. Scientists say they have reason to believe there are likely millions of these space rocks, some of which are massive, and range in size from several miles across, to less than a mile wide.
Every once in a while, a gravitational tug from one of the planets can knock these galactic boulders off course or alter their path, which can send the asteroid hurtling toward Earth. On Saturday, five of these galactic boulders will whizz by the planet.
The first object expected to make a close encounter is dubbed “2021 VC-7,” a school bus-size asteroid that is 25 feet long and will come within 115,000 miles of Earth, closer than the orbit of the moon, which is 240,000 miles from the planet.
Next up is “2021 VR-5,” a 45-foot-long space rock that is roughly the size of a house, which will come within a distance that is twice as far away, more than 247,000 miles from Earth, and from there, the distances become greater and the rocks get larger, including “2021 VU-B,” a hurling 51-foot space boulder that will pass by in an orbit that is 1.7 million miles from the planet’s surface.
A larger house-size object is next on the roster, weighing in at more than 150 million pounds at roughly 60 feet long will pass by about 3.5 million miles from Earth.
Finally, “2007 VD-138,” a 140-foot long space rock the size of a jumbo jet that is hurtling through space at more than 60,000 mph during its approach that will bring it within 3.8 million miles from the planet’s surface.
One asteroid that NASA deemed as very hazardous is expected to fly by the planet on Dec. 11, and this space rock dubbed “4660 Nereus” is massive – 3 times the size of a football field – which is roughly the size of the Eiffel tower.
Go big or go home – Comet 67-P
Comets are also known to make routine visits to the solar system. These objects are irregularly shaped and fragile and like asteroids, they are left over from the solar system formation process. But unlike asteroids, comets form in the outer solar system when dirt and dust become embedded with the comet’s surface.
They also have elliptical orbits that can intersect the orbits of the planets, bringing them very close to the sun before they are flung out into space, often beyond Pluto.
One such comet, categorized as “Comet 67-P,” had a close encounter with the third rock from the sun this week when its orbit came within 38 million miles from Earth, which is still between the orbits of Earth and Mars.
This comet is gigantic – with a nucleus that is 2.6 miles across and is one of the best-studied comets. In fact, the Rosetta spacecraft even landed on it during a mission in August 2014, which was a first at that time. The spacecraft traveled with the comet for more than two years.
Near-Earth objects and life on Earth
NASA has categorized any object that approaches the planet at a distance less than 1.3 times the distance from Earth to the sun – which is roughly within 93 million miles, as a near-earth object, or NEO, and while a majority of these objects are said to pose no risk to life on Earth, scientists are developing warning systems and diversion programs in the event one of these errant space rocks journeys too close to home.
There is a relatively small number of these near-Earth objects that pass close enough to the sun, ergo Earth, but even so, some are massive enough to warrant closer observation, since the gravitational forces from other planets can cause the orbital path of the asteroid to change over time. Those small changes in direction can also send the space rock on a collision course with Earth at some point in the future.
According to scientists, asteroids deemed potentially hazardous to life on Earth are generally at least 500 feet in length, or longer, which is roughly twice the size of the Statue of Liberty’s height, and these potentially dangerous objects typically orbit within 4.5 million miles from Earth.
In comparison, Mars and Earth are 33 million miles apart, which just goes to show how close these errant space objects can fly by Earth.
NASA’s Jet Propulsion Laboratory launched the Asteroid Watch dashboard, a site that tracks those asteroids and comets that will make a relatively close approach to Earth. The dashboard displays the date of the closest approach, the approximate size of the object, as well as the distance for each encounter and details about the object.
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