Really veered asteroid

Really veered asteroid

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NASA has confirmed She managed to divert the orbital path of the asteroid Demorphos by herself DART (Double Asteroid Redirection Test) mission. The probe collided with the small orb on September 27 at a distance of about 11 million kilometers from Earth, as part of a very important test to verify the possibility of avoiding a catastrophic asteroid collision with our planet in the future. The results, which exceeded expectations, confirmed that the deflection technique works and that it can be applied to larger scales if a dangerous asteroid is identified on Earth.

Demorphos has a maximum width of 160 meters and orbits a larger asteroid, Didymus, with a maximum diameter of 780 meters. After hitting DART – which had a mass of over 600 kilograms and a central cubic body roughly 1.3 meters long – the orbital period of Demorphos (that is, the time it took the small asteroid to complete a full circle around it at Didymos) went from 11 hours 55 minutes to 11 hours 23 minutes . The 32-minute change indicates that after the collision Demorphos approached Didymus by a few tens of meters, changing its orbit.

NASA has set itself the goal of declaring the orbital period change successful for at least 73 seconds. The change detected by the various telescopes exceeds the space agency’s most optimistic prediction, explains Nancy Chabot, one of the people in charge of the mission: “It’s a 4 percent difference from the orbital period of Demorphos around Didymus. DART gave it a little boost. But if we want to repeat the experiment “In the future, we’ll have to do this many years in advance. The wake-up period is key to being able to put this kind of asteroid deflection into practice as part of a broader planetary defense strategy.”


There are billions of asteroids and their fragments in orbit around the sun. The most popular hypothesis is that it’s what’s left of the “protoplanetary disk,” the massive mass of dust and gas that orbited the Sun billions of years ago that have since elapsed since the planets and natural satellites of the solar system we see today formed. Almost all asteroids are located in the “main belt”, which is a large ring of debris orbiting the sun, between the orbits of Mars and Jupiter at a safe distance from us.

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Collisions and other events can disrupt the orbits of some of these asteroids, bring them closer to our planet, and these are the ones that are controlled. Systems for detecting and tracking the nearest asteroid over time have allowed the classification of nearly ten thousand asteroids with a diameter of at least 140 meters, which could cause significant destruction on a regional scale in the event of a collision. No known asteroid seems to pose a direct threat to Earth for the next century, but it’s still important not to get caught unprepared.

Main belt in English “asteroid belt” (NASA)

For this reason, in recent years, various research groups have worked on some experimental solutions to “letter” asteroids, that is, to change their orbit. A promising and exploration technology, the kinetic collider, is to hit the asteroid with a probe when it is still too far from Earth, so that its new path does not go beyond that of our planet. DART has demonstrated the feasibility of this technique, at least on a small scale, through a more reliable real-world experiment than computer simulation. Asteroids do not have a homogeneous density, they have very different shapes and other physical properties that are difficult to predict and include in the simulation.

Despite the important result obtained with DART, NASA has maintained some caution about the following developments of deflection systems, precisely because each asteroid has its own characteristics. Deriving from one general rule that influences the behavior of asteroids would be wrong. However, the collected data will make it possible to significantly improve the computer simulation of the collision, making it more accurate.

Asteroid Demorphos seen by DART 11 seconds before impact (NASA/Johns Hopkins APL)

Other mission data was collected by LICIACube, a satellite (cubes) roughly the size of a shoebox, operated by the Italian Space Agency (ASI) and built by Argotec, a Turin space company that specializes in producing microsatellites. After traveling for a year in DART, LICIACube detached from the probe to position itself about a thousand kilometers from the point of impact.

LICIACube approaches and moves away from Dimorphos and Didymos (ASI/NASA)

In the hours following the impact, LICIACube observed and photographed the debris cloud that rose from the Dimorphos, and is important to reconstruct the impact’s extent and effects.

Debris cloud seen by LICIACube, image contrast changed at different points to make some features more visible (ASI)

Demorphos was then observed by many telescopes on Earth and by the Hubble and James Webb telescopes, the most powerful observatory in space. The observations were used to measure the slightest differences in the apparent brightness of the asteroid and its companion Didymus, in order to verify the change in orbit. From the observation point on Earth, Dimorphos passes in front and behind Didymos, constantly producing small partial eclipses. By calculating its duration, it is possible to estimate the speed with which the smaller asteroid orbits the larger, and to obtain data to check whether the impact with DART does indeed involve a change in the orbital period.

Debris cloud created after DART collided with Dimorphos, as seen by the Hubble Space Telescope (NASA/ESA/STScI/Hubble)

Dimorphos and Didymos will continue to serve as private guards over the next few years. The European Space Agency (ESA) plans to return to visit Dimorphos and Didymos with the Hera mission in about four years to provide new details on their condition. The new mission is part of the Asteroid Impact and Deflection Assessment (AIDA), an important collaboration between space agencies dedicated to the study and development of asteroid drainage systems.

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