SPACE — Asteroid Bennu has been found to revolve quicker over time, according to research published in Geophysical Research Letters.

NASA's OSIRIS-REx began approaching the asteroid last year. The spacecraft travelled 2.2 million kilometers from Earth and stationed itself 19 kilometers from Bennu.

The discovery was made via ground-based telescopes and the Hubble Space Telescope. Scientists looked at data from 1999, 2005 and 2013 and observed that the asteroid was increasing its rotational speed over time.

According to the study, the OSIRIS-REx spacecraft will independently determine Bennu's speed of rotation by flying closer to the asteroid."

The scientists believe that sunlight may be causing Bennu to spin faster as it hits the asteroid from various angles. This is known as the YORP effect.

Asteroid Bennu is currently traveling across space at 101,000 kilometers per hour and is able to complete a rotation every 4.3 hours.

According to the study, Bennu's speed of rotation has increased by around 1 second per century. The asteroid is estimated to be around 4.5 billion years old.

OSIRIS-REx was sent to collect data and sample the asteroid using the Osiris Visible and Infrared Spectrometer and Osiris Thermal Emission Spectrometer.

The spacecraft will use its Touch-and-Go Sample Acquisition Mechanism to extract rocks and dirt from the surface of asteroid Bennu in July of 2020.

It is expected to travel back to Earth and drop off a capsule containing asteroid samples in September 2023.