Occultation

Sometimes things in space hide each other.

This is called an occultation. It happens when one object moves in front of another. Then, the object in the back is hidden from view.

A moon can pass in front of a star. This makes the star disappear for a short time.

This can happen very fast. It may take less than one second.

Other things can hide stars too. A planet can move in front of a star. Even the sun can be hidden by the moon. This is called an eclipse.

Scientists use these events to learn. They can find out how big a space object is. They can also see where stars are located.

It is a very special thing to see in the sky.

An occultation is a special event in space. It happens when one object moves in front of another. This blocks the object in the back from view.

Most often, we see the Moon hide a star. The Moon moves in its orbit around Earth. This can make a star disappear very quickly. It may take less than 0.1 seconds to happen.

Sometimes, a planet moves in front of a star. This is much rarer. If a planet only blocks part of a star, it is called a transit. If the Moon blocks the Sun, we call it an eclipse.

Scientists use these events to study the sky. They time these events to learn about the Moon's shape. They also use them to find the size of small objects. For example, watching an asteroid hide a star helps measure the asteroid.

Even small moons can hide things. Scientists found a ring around the dwarf planet Haumea this way. These events help us understand our space neighbors.

An occultation is a special event in space. It happens when one object moves in front of another. This blocks the object in the back from view.

You can think of it like a person walking in front of a streetlamp. For a moment, the light is hidden from your eyes. In astronomy, this term is used when a closer object blocks a distant one. If the closer object only blocks part of the farther one, it is called a transit. If a shadow is cast onto the observer, we call it an eclipse.

Lunar occultations are very common events. This is when the Moon passes in front of a star. The Moon moves in its orbit around the Earth. Because the Moon has a very thin atmosphere, a star can disappear or reappear very quickly. This can happen in 0.1 seconds or less at the Moon's edge, also called its limb.

Observers often look for stars that hide on the Moon's dark limb. This is because there is no bright glare to make watching difficult. Some famous stars like Regulus, Spica, and Antares might be hidden by the Moon.

Scientists use these events to learn many things about space. By timing how long a star is hidden, they can study the Moon's topography, which means its surface shape. They can also find the size of stars. This helps them figure out how hot those stars are.

Early radio astronomers used occultations to find the exact positions of radio sources. This helped them identify a special object called a quasar. Even the rings of Uranus were discovered this way in 1977. Watching a planet hide a star can even help us study the atmosphere of dwarf planets like Pluto.

Many different objects can cause an occultation. Planets can hide stars, but these events are rare. For example, Venus hid the star Regulus in 1959. The next time Venus hides Regulus will be in 2044. Sometimes, one planet can even hide another planet. This is a very rare mutual planetary occultation. The last one happened in 1818, and the next will be in 2065. The rarest event is when Jupiter hides Saturn. The next time this happens will be on February 10, 7541.

Even small asteroids and dwarf planets can cause these events. When an asteroid passes in front of a star, it can help us see the asteroid's shape. In 1983, the asteroid 2 Pallas hid a star. Scientists used many locations to map its shape. On March 3, 1998, over 38 observatories watched the asteroid 39 Laetitia. This helped them learn about its size. In 2017, the dwarf planet Haumea was seen during a transit. This helped scientists find a ring around it. These tiny shadows help us map our solar system.

An occultation is an astronomical event where one object moves in front of another. This movement blocks the background object from view.

While the term is used in many fields, it is most common in astronomy. If a foreground object only partially covers the object behind it, the event is called a transit. If the two objects result in a shadow falling on the observer, it is called an eclipse. A total solar eclipse is actually a type of occultation where the Moon occults the Sun.

Lunar occultations are the most frequent type of this event. They occur when the Moon passes in front of a star during its orbit around Earth. Because the Moon has a very thin atmosphere, the transition happens very fast. A star can disappear or reappear at the Moon's edge, or limb, in 0.1 seconds or less. Astronomers often prefer to watch these events on the Moon's dark limb. The lack of glare on the dark side makes it much easier to time the event accurately.

Scientists use the timing of these events to gather vital data. By measuring exactly when a star vanishes, they can refine their knowledge of lunar topography, which is the study of the Moon's surface features. Photoelectric analysis of these moments has also revealed binary stars. These are stars that appear as one but are actually two stars orbiting each other. Additionally, timing occultations helps measure the angular diameter of stars. This measurement is useful for determining the effective temperatures of those stars.

Occultations can also involve planets. When a planet hides a star, the event is quite rare. For example, Venus occulted the star Regulus in 1959. The next time Venus will occult Regulus is in 2044. Planets also have significant angular sizes, which differs from stars. Because of this, a lunar occultation of a planet creates a narrow zone on Earth where only a partial occultation is seen. This allows observers in that specific zone to see the planet's disk being slowly blocked by the Moon.

Some of the rarest events involve mutual planetary occultations. This happens when one planet passes in front of another. If the closer planet looks larger than the distant one, it is a mutual occultation. One such event involving Venus and Jupiter occurred in 1818. The next will happen on November 22, 2065. An even rarer event is when Jupiter occults Saturn. This is one of the rarest known events in the sky. The last one occurred in 6857 B.C.E., and the next will not happen until February 10, 7541.

Small bodies like asteroids and dwarf planets also cause occultations. These events are incredibly useful for measuring the size and position of distant objects. By having many observers at different locations watch an occultation, scientists can create a cross-sectional profile of a body's shape. In 1983, the asteroid 2 Pallas was mapped using observations from 130 different locations. In 1998, over 38 observatories watched the asteroid 39 Laetitia. These precise measurements help scientists understand the dimensions of objects like Ixion and Varuna.

Occultations have also led to major scientific discoveries. In 1977, the rings of Uranus were discovered when the planet occulted a star. In the late 20th century, radio astronomers used lunar occultations to find the exact positions of radio sources. This was a key step in identifying the quasar 3C 273. This discovery helped Maarten Schmidt understand the cosmological nature of quasars. Even the atmosphere of Pluto has been studied by watching it occult stars. These moments of darkness provide a window into the structure of our entire solar system.