– Current Events/Space Telescopes Part 1

Though most any telescope can be used to look at the night sky, a telescope up in space can see stars more clearly than one down on Earth.

This week we will learn how a space telescope is different from an Earth telescope.

Next week we will take a closer look at two famous orbiting telescopes: the Hubble Space Telescope and the recently launched James Webb Space Telescope.

Space telescopes allow us to see things more clearly for three reasons: they are above the Earth’s atmosphere, they use mirrors instead of lenses, and some of them can see not just visible light, but invisible light as well.

The idea that some light is invisible may seem strange. We will find out more about that next week, along with the Hubble and James Webb space telescopes. For now, let’s consider how Earth’s atmosphere effects what we can see and how mirrors are better than lenses.

Earth’s atmosphere effects light that passes through it, and thus effects what we see in a telescope.

You can experience this without even using a telescope. On a clear night when you look up, the stars seem to twinkle. There’s even a song about this: twinkle, twinkle little star, how I wonder what you are.

Stars don’t really twinkle. It’s movement of air and dust particles in Earth’s atmosphere that make them seem to quickly flash bright and dim. They can also appear a little bit blurry. It is hard to get a good, clear, in-focus look at something that is shimmering and twinkling.

A telescope in space isn’t effected by Earth’s winds and dust, so can see heavenly bodies such as planets and stars without the twinkle and blur.

The next thing to consider is the use of mirrors instead of lenses.

All telescopes used to be made with glass lenses,  similar to those in eyeglasses. When light hits a lens it is bent and focused down onto an eyepiece and can make small things look closer and bigger.

The name for this type of telescope is a refractor or refracting telescope. Refraction means to bend or change direction. When light passes through a glass lens, it is refracted or made to change direction.

The problem with glass lenses is that they are difficult to make. Also, the bigger a lens is, the heavier it is. And the heavier it is, the more difficult it is to hold completely still.

Though there are some large and very good telescopes that use glass lenses, mirrors can also bend light and are cheaper and easier to make.

If a mirror is curved in just the right shape, all the light that hits it can be reflected to a small area, such as an eyepiece. Mirrors are much lighter and thinner and it’s easier to get a clear look at something using a curved mirror than it is using a heavy, glass lens.

The name for a telescope that uses a mirror is reflector, because that’s what mirrors do: reflect light.

Putting a telescope into space solves problems caused by atmosphere. Using mirrors in them instead of lenses solves problems of weight and cost to manufacture.

Next week we will learn about invisible light and about two famous space telescopes.

Fun Facts.

•  A glass lens is held in place by its edge. Gravity will cause the thick middle of a large lens to sag slightly. You can’t see the sag, but it’s enough to distort images that the lens produces. Around 40 inches is the largest that a glass lens can be and still work properly.

•  The largest refractor telescope ever built is at Yerkes Observatory in Wisconsin. Its lens is 40 inches in diameter.

•  The largest reflector telescope is at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, Spain. It’s mirror is 410 inches in diameter.

•  There is a type of telescope that uses both a lens and a mirror. It’s called a compound telescope. It’s also called a catadioptric telescope. Catadioptric (cat-a-di-OP-tric) means using both the refraction and the reflection of light.