Didymos and Dimorphos: The steroids NASA aims to probe into 

According to USA’s space agency, National Aeronautics and Space Administration (NASA), several potentially hazardous asteroids such as 2021 SM-3, Didymos and Dimorphos, have passed close to Earth occasionally in recent months. Aesteroids are small, rocky objects that orbit the sun. While they haven't yet caused any harm to humans, a slight variation in their course could have disastrous consequences for our planet. Therefore, NASA launched the Double Asteroid Redirection Test (DART) mission in November last year to deflect such dangerous asteroids from their current track and avoid colliding with the Earth. Dimorphos, Didymos' moonlet (a tiny natural satellite), will be around 11 million kilometres from Earth in September 2022. Between September 26 and October 1, 2022, DART will intercept this moonlet.  

The mission's purpose is to measure the shift in the moonlet's orbit around Didymos to see how much the impact changes its velocity in space. The collision is expected to affect the moonlet's speed by a fraction of a percent and its orbital period around the larger asteroid by several minutes, which will be visible and monitored by telescopes on Earth. 

Here is all about the asteroid Dimorphos orbits: Didymos.  

What is the size of Didymos? 

Didymos, the binary pair's larger asteroid (also known as Didymos A), is about a half mile (780 metres) in diameter. Dimorphos (Didymos B) is a moonlet with a diameter of around 525 feet (160 metres). The asteroid pair approaches Earth's orbit as it orbits the Sun, occasionally reaching relatively near to our planet. It was only 0.048 AU away from Earth in 2003. The distance between the Sun and Earth is measured in astronomical units, abbreviated as AU. Didymos is around 3 AU away at its furthest point, when it is on the other side of the Sun from Earth, just beyond Mars' orbit. 

How does Didymos look like? 

Didymos has the shape of a spinning top with a high ridge extending along its equator, which is a common structure among binary asteroids. The asteroid's high rotation is assumed to be driving material toward the equator, generating a bulge in the centre. On the other hand, the structure of the moonlet is unknown, except that it appears to be rather elongated. 

How is the surface of Didymos? 

Although the surface of Didymos cannot be viewed in great detail from Earth, scientists believe it is comparable to the surfaces of similarly shaped asteroids visited by spacecraft like Bennu and Ryugu. Both asteroids have highly rough surfaces that are littered with boulders of varying sizes. They don't have the fine-grained regolith (layer of unconsolidated solid material covering the bedrock of a planet) or loose, dust-rich outer layer, that the Moon and other asteroids do. 

How was the Dimorphos moonlet formed? 

It's unclear whether binary asteroids develop in the same way or through a variety of methods. Didymos' quick spin suggests that the Dimorphos moonlet was produced by a process known as rotational fission, in which material is ejected from the asteroid due to its rapid rotation. Also, Dimorphos is said to be Didymos' only moon. 

Didymos is assumed to have begun spinning faster as a result of infrared radiation released unevenly from its Sun-warmed surface, causing a twisting force also called torque. This process could have built up enough velocity over millions of years to release material from the surface, which eventually accumulated into the moonlet. Other alternatives, though, haven't been ruled out completely. 

How long does it take Didymos to orbit around the sun? 

Didymos' orbit stretches from just outside Earth's orbit (approximately 1 AU) to just beyond Mars' orbit (about 2.27 AU) and is slightly inclined by about 3 degrees with respect to the plane of the planets called the ecliptic. Each orbit of the Sun takes 2.11 years to complete. Didymos spins quickly, rotating once every 2.26 hours. Every 11.9 hours, the moonlet circles around the bigger body. The primary asteroid and its moonlet are 0.62 miles (1 kilometre) apart in orbit.