Yarkovsky effect

In astrophysics, the Yarkovsky effect is a special force that affects spinning objects in space. This force happens because these objects don't give off heat evenly in all directions. Instead, they release heat more in some directions than others.

This effect is very important for small space rocks, like meteoroids or small asteroids that are between about 10 centimeters and 10 kilometers wide. For these smaller objects, the Yarkovsky effect can change their paths as they move around the Sun.

Scientists study this effect to better understand how these space rocks move and where they might go in the future. It helps us predict their orbits and learn more about the solar system.

History of discovery

The Yarkovsky effect was discovered by Ivan Osipovich Yarkovsky, a Polish-Russian engineer, who noticed that the daily heating of a rotating object in space could create a small force. This force, though tiny, might change the paths of small space objects over a long time, especially meteoroids and small asteroids.

Later, the Estonian astronomer Ernst J. Öpik remembered Yarkovsky's idea and talked about how it might affect the movement of meteoroids in the Solar System.

Mechanism

The Yarkovsky effect happens because an object takes time to heat up and cool down when sunlight shines on it. This means the object is warmest a little after the Sun is at its brightest, not exactly when. This creates a small force that changes the object's path.

For bigger objects, like asteroids more than 100 meters across, this force makes them move slowly away from the Sun if they spin in one direction, or toward the Sun if they spin the other way. Smaller objects feel a different kind of force that can pull them toward the Sun, especially if they spin very fast or are shaped in certain ways. Over millions of years, this tiny force can change an asteroid's path enough to move it from the asteroid belt closer to the Sun.

Measurement

The Yarkovsky effect was first measured on the asteroid 6489 Golevka. Over twelve years, it moved 15 kilometers from where scientists expected it to be. This was figured out using observations from the Arecibo radio telescope in 1991, 1995, and 1999.

It is difficult to predict exactly how the Yarkovsky effect will change an asteroid's path because it depends on many factors that are hard to know, like the asteroid's shape and how it reflects light, called its albedo. The effect can also be influenced by shadows and the way heat is re-released from the asteroid's surface. It works alongside something called radiation pressure, which can also push asteroids slightly over time.

Scientists are studying ways to use the Yarkovsky effect to move asteroids that might come close to Earth. One idea is to change the asteroid's surface or use sunlight to change how the effect works, which could move the asteroid away from Earth. The OSIRIS-REx mission, launched in 2016, looked at the Yarkovsky effect on asteroid Bennu.

In 2020, scientists measured the Yarkovsky effect on the asteroid 99942 Apophis. This helped them understand the chance of it hitting Earth in 2068. In 2021, using data from the Gaia satellite and observations from the ground, scientists were able to measure the effect very precisely and showed that Apophis will not hit Earth for at least the next 100 years.