The dark asteroid Dragon Palace finally enters the light


Hayabusa2 also provides researchers with unique opportunities to observe the asteroid from multiple angles, including difficult-to-obtain images taken at “opposite” locations. This involves manipulating a refrigerator-sized spacecraft to capture a snapshot when the asteroid and the sun are on either side of it. This alignment can provide a view of the asteroid, and the sun’s rays are reflected directly back to the camera without any shadows.

Due to optical physics, any object with a rough surface that reflects light will look slightly brighter when opposed. This means that small, faint, and distant asteroids can actually only be seen during an opposition. In fact, they are so dark that we cannot see the “new moon phase” like the moon from the earth. Domingue and Yokota discovered that Ryugu is one of the darkest celestial bodies ever: it reflects only about 3.5% of sunlight, and it is darker than other types of asteroids, even darker than a piece of coal.

But close-range and hedge photography allowed researchers to obtain detailed images of the asteroid’s surface. It enhances the way in which asteroid dust interacts with light, making it clearer that it does exist. Bannister said that the opposite image is like when the sun is directly behind you looking at a grassy lawn, you can see individual leaves, rather than when the sun is obliquely shining on the lawn, it creates a lot of shadows. Comparing the opposition image with the image taken near the opposition, “tell you how dense your lawn is, but from a distance, it may look completely smooth,” she said.

Most unshaded photos also allow researchers to map the surface structure of the Dragon Palace, at least on one side.

This exploration of the Dragon Palace is part of a broader effort to investigate various types of asteroids to learn more about their shape, content, and origin. Ryugu is similar to another near-Earth asteroid called Bennu. Recently visited By NASA OSIRIS-REx spacecraftThey are all C-shaped asteroids, shaped like the top, but the central ridge is differently protruding. The first Hayabusa mission rendezvous with a more rocky S-type asteroid. NASA’s Psyche mission will go to an M-type asteroid full of iron and other metals next year. The agency’s Lucy CraftIt will be launched in October this year and will go to the D-type Trojan asteroid to study the components that form the world of Jupiter.

Andy Rifkin, a planetary astronomer at Johns Hopkins University in Baltimore, said that the inhabitants of the main asteroid belt are scattered groups of space rocks where Jupiter has never been allowed to become a planet and has maintained a stable orbit for billions of years. In contrast, the orbits of near-Earth asteroids are even stranger. “Things like Bennu and Ryugu will eventually hit planets or the sun in millions of years, so they cannot stay there for a long time,” he said.

Ryugu was most likely formed when something collided with a larger asteroid, breaking a pile of rock fragments, which later gathered together and moved on different trajectories. Rivkin said that meteorites or large asteroids and comets that hit the Earth may have similar origins, although C-type meteorites are not common. After comparing the structure, topography and composition of Ryukyu with other larger asteroids, Yokota believes that it may have originated from a “mother body” called Euleria. Although other asteroids have not yet been ruled, it is the same. Dark and rich in carbon as its parent.

The study of near-Earth asteroids is of great significance for scientists to understand celestial bodies that may one day collide with the Earth. “We know that no asteroid will hit the Earth,” Rifkin was quick to point out, but scientists at NASA and elsewhere try to monitor every traceable asteroid, just in case one arrives in our direction. The time of the year. Occasionally their trajectory will change subtly, possibly pointing them in a more dangerous direction (from the perspective of a human being on Earth). This may happen due to the impact of smaller objects or what is known as the Yakovsky effect, which is when sunlight hits an asteroid and is re-radiated as heat, giving it a tiny thrust.


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