The Dark Asteroid Ryugu Finally Goes to the Light

Hayabusa2 also gave researchers unique opportunities to observe the asteroid from multiple angles, including hard -to -capture images taken by the “opposition.” This includes maneuvering the spacecraft as much as the fridge to take snapshots while the asteroid and sun are on the opposite side of it, an alignment that provides views of the asteroid with the sun’s rays directly returning to it. camera, without any shadow.

Thanks to the physics of optics, anything with a thick surface that reflects light seems brighter when it is in opposition. This means that small, weak, and distant asteroids can only be seen in opposition. In fact, they are so dark that from Earth we cannot see a “crescent period,” such as looking at the moon. Domingue and Yokota found that Ryugu was one of the darkest objects ever seen: Reflecting almost 3.5 percent of the sunlight, much darker than other asteroid species and much darker even in a lump of carbon.

But taking photos up close and in opposition allowed the researchers to get a detailed image of the asteroid’s surface; it improves the way the asteroid dust interacts with the light, making it most clear that it actually exists. Bannister says the opposition images are like looking at a grassy lawn when the sun is behind you, allowing you to see the individual blades, as opposed to when the sun sets on the lawn, which makes many shadows. Comparing the images in opposition to those taken almost by the opposition “tells you how bristly your lawn is, but from a distance, it all looks perfectly smooth,” he says.

Most of the shadowless photographs have also enabled researchers to map Ryugu’s face, at least in part.

This Ryugu exploration is part of a much broader effort to investigate several asteroid species to find out about their shapes, sizes, and origins. Ryugu is similarly close to the Earth asteroid, called Bennu, that is recently visited by NASA’s OSIRIS-REx spacecraft. They are both C-type asteroids with shaped peaks, although there is a different emphasis on the central ridges. The first Hayabusa mission encounters a more rocky, S-type asteroid. NASA’s planned Psyche mission next year is to travel to an M-type asteroid filled with iron and other metals, and agency Lucy work, launched this October, will travel to D-type Trojan asteroids to study the building blocks that make up the Jovian worlds.

Residents of the main asteroid belt, a scattered fusion of rock cliffs that Jupiter has never allowed to form a planet, have strong orbits for billions of years, according to Andy Rivkin, a planetary astronomer at Johns Hopkins University in Baltimore. In contrast, asteroids close to Earth have winkier orbits. “Something like Bennu and Ryugu have finally hit a planet or the sun millions of years ago, so they haven’t been there in the longest,” he said.

Ryugu might have formed if something had collided with a much larger asteroid, destroying a large number of rocky debris that later accumulated and headed in different directions. The meteorite, or fragment of asteroids and comets that hit Earth, may have the same origin, even if C meteorites are not common, according to Rivkin. Comparing Ryugu’s structure, soil, and composition to different sized, mostly asteroids, Yokota believes it may have come from a “parent body” called Eulalia, which is both dark and rich in carbon, even if other asteroids have not yet been launched. as its parents.

Research on asteroids near Earth has implications for scientists ’understanding of bodies that could one day collide with Earth. “We don’t know which asteroids will hit Earth,” Rivkin quickly pointed out, but scientists at NASA and elsewhere will try to monitor every traceable asteroid, if one goes in our direction with a -abut. time within a couple of decades. Often their paths can be subtle shifts, which can point them in a more dangerous direction (from the perspective of Earthlings). This can happen thanks to the effects of small objects or something known as the Yarkovsky effect, which is when sunlight hits an asteroid and is repeated like heat, giving it a slight thrust.

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