How to find stars using the Doppler effect

ByMatt Hendrick

"Sound of siren sounds high when it approaches, it sounds low when going away" is often expressed by the word "Doppler effectIn fact, it is also used for exploring the universe. Astronomer Rad Milla Tooparovic explains the method of space exploration in which the Doppler effect of "light" instead of "sound" is used in a demonstration movie.

VimeoAlien worlds and the Doppler effect


"The Milky Way is made up of 400 billion stars in the Greenwich astronomical observatory," says the astronomersRadomira To Paro BicDoctor. It is thought that the planet is turning further around the stars that make up the Milky Way, but it is too far from the Earth, so it is very difficult to check the existence of these stars with a camera and check it is.


So, to confirm the existence of stars, a slightly more technical way is taken.


Dr. To Parovic holds a ball that looks like a star. It shows that there is only one ball, no orbiting planet.


Spinning the ball on the floor, it spun around the spot and finally stopped.


Next I prepared a model imitating a star with a planet. Large and small balls are connected with a stick.


Spin on the floor ......


Planets spin around the stars, but unlike the previous planet we know that it is totally unsteady. This is because two balls are between each otherCenter of massBecause it is turning around.


The same thing can be said of the two balls in the relation between the star and the planet, and wobble exists. Therefore, we observe this wobble by using the Doppler effect to confirm the existence of the planet.


Subsequently, Dr. To Parovic took out the speaker. Next, I will explain the Doppler effect by assuming the speaker as a star.


A speaker that emits a high sound as "Pee".


Put this in a bag ... ...


I will turn around and head overhead.


Then, although the sound is not changing, the louder the speaker is from the camera, the lower the sound, the higher the sound comes closer to the camera. This is what is said to be the Doppler effect.


Next is the sound of the recorded speakerspectrogramI will analyze it.


The frequency of the following spectrogram is frequency and the width is time.


The original sound is 3200 hertz, if you do not rotate the speaker, it should have been drawn straight around the area shown by hand. The Doppler effect was born by rotating the speaker, and the wave was drawn.


According to Dr. To Parovic, the Doppler effect occurs not only in the sound but also in the light.


The star and the planet will turn around the mass center between the two due to the gravitational relationship, but the fluctuation occurring at this time produces Doppler effect of light.


The spectrum of the light emitted from the star arises as light is absorbed by the substanceDark lineExist.


The visible wavelength becomes shorter as the color becomes blue, and the longer it approaches the red color, the longer the wavelength becomes. Since it is decided to what color position the dark line comes out depending on which substance the light is absorbed, if it was absorbed by the same component, the dark line should always appear at the same position at all times. The fact that the position of the dark line shifts means that the star is moving away or approaching, and it is understood that the planet exists in the observing star and "fluctuation" is occurring.