Mechanics

# Parallax

Measurement of the distance to a star by the parallax angle method

On a clear day, without the presence of clouds, we can observe the stars more easily, so we can see those that have little brightness with the naked eye. When we look at a specific star, we wonder how far apart we are.

We also think about how the distance of stars outside the solar system is calculated, since the closest star to Earth is 150 million kilometers away. But how can this distance be measured? In astronomy, one of the methods to perform this measurement is through Parallax .

Because in astronomy the objects of study are almost always distant, astronomers have developed methods capable of obtaining information about these bodies just by analyzing the light emitted by them. In order to measure the distance to a star, they used the measure of the parallax angle.

To better understand parallax , let’s do the following experiment: first lift your index finger, stretch your arm. With one eye closed, look at your finger and see the bottom behind it. Without moving your finger, close the eye that was open and open the other. Notice that your finger has shifted in relation to the background.

the parallax stellar is performed in the same way, only instead of using a finger it uses a star and instead of using the eyes it benefits from the rotation of the Earth around the Sun. Thus, we define parallax as the difference in the apparent position of an object seen by two observers at different points.

We can measure the distance of a star based on the Sun: this measurement is called annual or heliocentric parallax.. It is most often used to measure the distance to nearby stars. According to the fact that the Earth revolves around the Sun, we can measure the direction of a star in relation to the background stars, when the Earth is on one side of the Sun; and we take the measurement again six months later, when the Earth is on the other side of the Sun. Half of the total deviation in the star’s position corresponds to the heliocentric parallax.