This extraordinary image of the Deep Space 1 spacecraft was today released by NASA to mark International Asteroid Day 2020. The photograph was taken using the 200-inch Hale telescope on Palomar Mountain by Jet Propulsion Laboratory astronomers.
The US-based space agency wrote in an accompanying caption: “Tracing a path against the constellation Gemini.
“This image was obtained on November 16, 1998, 23 days after the spacecraft’s launch from Cape Canaveral.
“The spacecraft was receding from Earth at a speed of 1.1 miles per second relative to Earth.
“The spacecraft, just 4.9ft (1.5m) high, was four million times dimmer than the faintest star visible to the unaided eye.
“Top of the image is north. Each side of this square image is five arc-minutes or approximately 0.08 of one degree.”
The moonlet’s new moniker Dimorphos, is Greek for “having two forms,” in honour of the two different trajectories it will have before and after the spacecraft knocks it askew.
At just 525ft (160m) across, approximately the height of Egypt’s Great Pyramid of Giza, Dimorphos is one of the smallest objects to earn an official name from the IAU.
NASA will launch the Double Asteroid Redirection Test (DART) spacecraft in July 2021 to crash-land on Dimorphos in September 2022, roughly 7 million miles (11 million km) from Earth.
The collision should nudge Dimorphos into a tighter orbit around Didymos — a change that is much easier to measure than knocking a solo asteroid into a slightly different orbit around the sun, says Kleomenis Tsiganis, a planetary scientist at the Aristotle University of Thessaloniki in Greece, who is working on the DART mission and suggested the name Dimorphos.
Dimorphos currently orbits Didymos once every 12 hours.
Dr Tsiganis said by hitting it with DART, “you’re actually changing the orbital period enough — by, say, 10 minutes or 20 minutes — which could be observed even from the ground.”
Telescopes on Earth will track the immediate aftermath of the crash, and the European Space Agency (ESA) will send its Hera probe to Dimorphos in 2024.
This will ensure the moonlet asteroid is following its new intended path.