Physics of the James Webb Space Telescope


In fact, JWST uses infrared light for another good reason: It is difficult to observe distant celestial bodies without obstacles due to the debris gas and dust of old stars. They scatter visible light more easily than infrared wavelengths. Essentially, infrared sensors can see through these clouds better than visible light telescopes.

Since JWST is observed in the infrared spectrum, scientists need everything around the telescope to be as dark as possible. This means that the telescope itself needs to be very cold to avoid emitting its own infrared radiation. This is one of the reasons it has sun visors. It will block the sunlight from the main instruments and keep them cold.It also helps to block excess light so that the telescope can Receive relatively dim light from exoplanets When they orbit a brighter host star. (Otherwise, it’s like someone shinning your face with a flashlight trying to see something in the dark.)

How does JWST look back on the past?

Light is a wave that travels very, very fast. In just one second, light can circle the earth seven more times.

When observing celestial bodies, we must consider the time it takes for light to travel from the celestial body to our telescope or eye. For example, light from the nearby Alpha Centauri system takes 4.37 years to reach the earth. So if you see it in the sky, you are actually looking at the past 4.37 years.

(Actually, everything you see is the past. You see the moon about 1.3 seconds in the past. When the closest to the earth, Mars is in the past 3 minutes.)

The idea is to allow JWST to see more than 13 billion years in the past until the point of evolution of the universe when the first stars formed. If you think about it, that’s great.

What is a Lagrangian point?

Hubble Space Telescope in Low earth orbit, Which is good, because astronauts can provide services when needed. But JWST will be farther away, at the L2 Lagrangian point. But what exactly is Lagrange point?

Let us consider Hubble orbiting the earth. For any object that moves on a circle, there needs to be a centripetal force, or a force that pulls it toward the center of the circle. If you swing the ball on the rope around your head, the force that pulls the ball toward the center is the tension of the rope. For Hubble, this centripetal force is the gravitational force generated by its interaction with the earth.

As the object moves away from the earth, the strength of this gravitational force will weaken. Therefore, if the telescope moves into a higher orbit (larger circle radius), the centripetal force will decrease. In order to stay on a circular orbit, Hubble must take longer to get into orbit. (We would say that its angular velocity is lower.)



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