73-Billion-Kilogram Asteroid Likely to Explode as It Continues to Spin at Increasing Speeds

Scientists have likened asteroid Bennu to a chocolate creme egg because of its shape. Study co-author Daniel Scheeres said that in a million years or less, Bennu would explode if it continues to spin at a faster rate.

Scheeres, along with other astronomers, published a study in Science Advances on Thursday, about asteroid Bennu using the data they gathered from OSIRIS-REx, NASA's spacecraft that is expected to retrieve a sample from the asteroid on October 20.

Scientists have mapped the gravitational field of Bennu by measuring its gravitational pull towards the OSIRIS-REx as the spacecraft orbits around it. They also modeled the tiny pebble-sized bits of dirt on the asteroid's surface and orbited as part of probing Bennu.

Asteroid Bennu is said to be as big as the Empire State Building and weighs about 73 billion kilograms, based on the previous measurements done by OSIRIS-REx that allowed researchers to measure it, The University of Colorado Boulder reported.

Bennu's Spin Rate Threatens to Tear It Apart

A report by The A Register said that Bennu is set to tear apart because of the rate it spins. The latest analysis of Bennu revealed its deeper context, and scientists discovered that unlike its rugged exterior, Bennu's interior was lesser dense.

Shaped like a spinning top, asteroid Bennu is a mound formed together by debris. Its exterior of rugged rocks does not coincide with its interior pf loose and less tightly packed rocks. What concerns most scientists is that Bennu's core is the softest part and its equator bulges out.

Study co-author and NASA-JPL scientist Andrew French said that "if you can measure the gravity field with enough precision, that places hard constraints on where the mass is located, even if you cannot see it directly."

The motion of Bennu is also affected by the Sun so much like other celestial bodies in the solar system. Solar rays from the Sun warms Bennu's surface in which some of the heat is absorbed while others are re-emitted into space that makes the asteroid spin because photons re-emitted act like a kick.

The spinning of Bennu is called the YORP effect, short for Yarkovsky-O'Keefe-Radzievskii-Paddack effect. According to the Planetary Society, Yarkovsky realized that the infrared radiation that escapes Bennu carries off momentum and heat, which creates a tiny thrust. Understanding the YORP effect on Bennu helps scientists predict its orbit and determine when it will hit the Earth.

A study suggests that the spin rate of Bennu appeared to be accelerating over time, which could someday make it explode and tear it apart. It also does not help that Bennu's core is its softest part, making it easier for the entire asteroid to explode.

When will Bennu explode?

Asteroid Bennu may be exploding, but not to worry because scientists said it would not explode anytime soon. They estimated that it could tear apart in a million years as the asteroid continues to spin itself in a destructive frenzy. However, before that, it will still be there for the OSIRIS-REx to collect some regolith samples.

Scheeres said that their team is hoping to find out how this asteroid came about, which they believe can better insight into how other small asteroids change for millions of years.

"Our findings exceeded our expectations," Scheeres said.