DART really deflected the asteroid

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NASA has confirmed that it has succeeded in redirecting the orbit of the asteroid Dimorphos with its DART (Double Asteroid Redirection Test) mission. The probe crashed into the small celestial body about 11 million kilometers from Earth on September 27, as part of a very important test to check the possibility of avoiding catastrophic asteroid collisions with our planet in the future. Far exceeding expectations, the results confirmed that the deflection technology works and that it could be applied on a larger scale if an asteroid dangerous to Earth is identified.

Dimorphos has a maximum width of 160 meters and orbits a larger asteroid, Didymos, with a maximum diameter of 780 meters. After the impact of DART – which had a mass of over 600 kilograms and a nearly cuboid central body with a side length of 1.3 meters – the orbital period of Dimorphos lasted (d. went from 11 hours and 55 minutes to 11 hours and 23 minutes. The change of 32 minutes indicates that after the collision, Dimorphos approached Didymos by a few tens of meters and changed its orbit.

NASA had set itself the goal of declaring a change in orbital time of at least 73 seconds to be a success. The variation, seen by various telescopes, exceeds the space agency’s most optimistic predictions, as Nancy Chabot, one of the people responsible for the mission, explained: “It’s a 4 percent variation in the orbital period of Dimorphos around Didymos. DART just gave him a little push. But if we want to repeat the experience in the future, we have to do it many years in advance. The alert time is key to being able to put this type of asteroid anomaly into practice as part of a broader strategy to defend the planet ».

(NASA)

There are billions of asteroids and their fragments orbiting the Sun. The most common hypothesis is that they are the remnants of the “protoplanetary disk,” the vast mass of dust and gas that orbited the Sun billions of years ago, since the Planets and natural satellites of the solar system as we see them today came into existence. Almost all asteroids are in the “main belt,” a large ring of debris surrounding the Sun, between the orbits of Mars and Jupiter, a safe distance from us.

Collisions and other events can upset the orbits of some of these asteroids, bringing them closer to our planet, and these are exactly what is being kept in check. The detection and tracking systems of the nearest asteroids have, over time, made it possible to catalog almost ten thousand with a diameter of at least 140 meters, which could wreak great devastation at a regional level in the event of an impact. No known asteroid appears to pose a direct threat to Earth for the next century, but it’s still important not to be caught unprepared.

The main belt, in English “asteroid belt” (NASA)

For this reason, various research groups have been working on some experimental solutions in recent years to “deflect” the asteroids, i.e. change their orbit. The best-studied and most promising technique, the kinetic impactor, consists of hitting the asteroid with a probe when it is still very far from Earth, so that its new orbit no longer crosses that of our planet. DART demonstrated the feasibility of this technique, at least on a small scale, with a real experiment that is more reliable than computer simulations. Asteroids do not have a homogeneous density, they have very different shapes and other physical properties that are difficult to predict and include in a simulation.

Despite the important results obtained with DART, NASA has exercised caution in the next developments of the deflection systems precisely because each asteroid has its own characteristics. Inferring implications for asteroid behavior from a single general rule would be a mistake. However, the data collected will allow the computer simulations of collisions to be greatly refined and made more accurate.

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

Other key data was collected by LICIACube, a shoebox-sized satellite (Cubesat) managed by the Italian Space Agency (ASI) and built by Argotec, a Turin-based space company specializing in the manufacture of microsatellites. After a year’s journey accompanied by DART, LICIACube had separated from the probe to position itself about a thousand kilometers from the impact site.

LICIACube approaching and receding from Dimorphos and Didymos (ASI/NASA)

In the hours after the collision, LICIACube observed and photographed the plume of debris rising from Dimorphos, which is important to reconstructing the magnitude and impact of the impact.

The cloud of debris seen by LICIACube, the contrast of the image has been changed in various places to highlight some features more clearly (ASI)

Dimorphos was then monitored by numerous telescopes on Earth and by the Hubble and James Webb Space Telescopes, the most powerful observatory in space. The observations were used to measure the smallest deviations in the apparent brightness of the asteroid and its companion Didymos to verify the change in orbit. From the observation point on Earth, Dimorphos passes in front of and behind Didymos, continuously creating small partial solar eclipses. By calculating their durations, it is possible to estimate the speed at which the smaller asteroid rotates around the larger one and obtain data to verify that the impact with DART did in fact involve a change in orbital period.

The debris cloud formed after DART’s impact on Dimorphos as seen by the Hubble Space Telescope (NASA / ESA / STScI / Hubble)

Dimorphos and Didymos will continue to be special guards for the next few years. The European Space Agency (ESA) plans to revisit 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), the important collaboration between space agencies dedicated to the study and development of asteroid deflection systems.

#DART #deflected #asteroid

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