The dark asteroid Raigu finally comes to light

Hayabusa 2 also gave researchers the unique opportunity to observe the asteroid from multiple angles, in which it was difficult to take “opposite” images. The fridge-sized spacecraft was involved in capturing snapshots when the asteroid and the sun were on opposite sides, an alignment that reflected astronomical scenes with the sun’s rays directly to the camera, without creating any shadows.

Thanks to the physics of optics, a rough surface that reflects light will feel slightly brighter when it is in the opposite state. This means that small, faint and distant asteroids are only seen in opposition. In fact, they are so dark that from Earth we do not see “crescent episodes” like the moon. Dominguez and Yokota find that Raigu is one of the darkest objects ever seen: reflecting about 3.5 percent of sunlight, darker than other types of asteroids and darker than a bunch of coal.

But taking close-up and contrasting images allows researchers to get detailed images of asteroid surfaces; It has improved the way the asteroid dust interacts with light, making it clear that it is actually there. Banister says the contrasting images are like looking at a grassy lawn when the sun is directly behind you, allowing you to see individual blades, when sunlight falls diagonally on the lawn, creating lots of shadows. Comparing the contrasting images with the opponents “tells you how bright your lawn is, but from a distance, it can all look smooth,” he says.

Most shadow-free images have also enabled researchers to map the structure of the Raigu surface on at least one side.

Raigu’s discovery is part of a broader effort to explore more types of asteroids to learn more about their size, content, and origins. Ryugu is like another asteroid near Earth, called Benu, which was recently visited by NASA’s OSIRIS-Rex spacecraft. These are both C-type asteroids that are shaped like a vertex, although with distinctly strong central gases. The first Hayabusa mission was joined by a more rocky, S-type asteroid. NASA’s planned Psyche mission will travel next year to an M-type asteroid full of iron and other metals, and the agency’s Lucy Kraft, which will launch this October, will move toward the D-type Trojan asteroids building blocks that Jovian formed Earth.

Andy Rivkin, a planetary astronomer at Johns Hopkins University in Baltimore, says the inhabitants of the original asteroid belt never allowed Jupiter, a scattering of space rocks, to become a planet, with stable orbits for billions of years. In contrast, asteroids near Earth orbit orbit strangely. “Something like Benu and Raigu eventually hit a planet or sun for millions of years, so they can’t stay there too long,” he says.

Ryugu was probably formed after some collisions with many large asteroids, which broke up a bunch of rocky debris that later glowed together and moved in a different direction. Meteors, or parts of asteroids and comets that hit Earth, may have similar origins, Rivkin says, although C-type meteors are not common. After comparing Raigu’s structure, terrain, and composition with various, larger asteroids, Yokota believes it may have evolved from a “parent body” called Yulalia, which is similarly dark and rich in carbon, although other asteroids have not ruled their parents. As.

Research on asteroids near Earth has had an impact on scientists’ understanding of corpses that could one day collide with Earth. “We don’t know which asteroid is going to hit Earth,” Rivkin noted early on, but scientists at NASA and elsewhere try to observe every trackable asteroid, if anyone is approaching us as soon as we arrive. Within decades of time. Sometimes their trajectories can be subtly shifted, potentially pointing them in a more dangerous direction (from Earthlings ’point of view). This may be due to being affected by small objects or for something known as the Yarkovsky effect, which when sunlight hits an asteroid and redevelops as heat, gives it a small thrust.

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