Asteroid Juno Spotted by ALMA Travelling Through Space

The Atacama Large Millimeter/submillimeter Array (ALMA) has captured an unprecedented view of the surface of Juno, one of the largest members of our solar system's main asteroid belt. The new images reveal a bit more about this asteroid.

"In contrast to optical telescopes, which capture the reflected light from the sun, the new ALMA images show the actual millimeter-wavelength light emitted by the asteroid," said Todd Hunter, one of the researchers, in a news release. "By using ALMA to image the thermal glow from asteroids like Juno and other bodies in our solar system, astronomers will be able to study their shape, composition, and surface properties."

The complete observation includes 10 separate images and documents about 60 percent of one rotation of the asteroid. It was conducted over the course of four hours when Juno was about 295 million kilometers from Earth. In these images, the asteroid's axis of rotation is tilted away from Earth, evealing its southern hemisphere most prominently.

Juno will make its next close approach to Earth in November 2018. Since the asteroid will be much closer than it was in the most recent observations, ALMA will be able to double its resolution, potentially revealing new details about Juno.

"This new observation clearly demonstrates that ALMA will be a very powerful tool for studying asteroids," said Arielle Moullet, NRAO astronomer. "At its highest resolution, ALMA is powerful enough to resolve the surface of many asteroids."

The findings are published in the Astrophysical Journal Letters.

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