Telescopes

It is essentially on telescopes that modern astronomy is founded. In the ages before this technology was invented, all astronomy was naked-eye astronomy which means that we were vastly limited by what our eyes can see — even with the assistance of the first telescopes just over 400 years ago — and most of what exists in space is simply too dim for our eyes to see.

Telescopes both magnify and extend the power of our eyes. With the naked eye we can see about 2000 stars from the Earth’s surface, when in the Milky Way galaxy alone, there are between 200–400 billion stars. Not only can we see further than our eyes could ever be capable of because of fundamental limitations of their design and size, but we can also see over a broader spectrum in that wavelengths of light that are invisible to our eyes are visible to telescopes (depending on the type of telescope) which can be rendered visible to us when we process that information with a computer.

The Function of a Telescope

The main purpose of a telescope is to increase the magnifying power and optical range of our eyes (the range of frequencies that we can see). Telescopes do this by creating technology based on the mechanism of our eyes and enhancing the specs, so to speak.

All telescopes gather light. It doesn’t matter what kind of light either — telescopes gather Radio Waves, Visible Light, Gamma radiation, X-Rays, UV light and Infrared — different types of telescopes are designed specifically for different frequency bands of light. All telescopes collect light, gathering as much as possible and focusing it to be recorded, and observed for analysis.

Modern astronomers have to analyze all forms of electromagnetic radiation in order to “see” what is happening. Visible Light at certain frequency bands can tell us the atoms in the atmosphere of different stars. Whereas X-Rays indicate the existence of a specific type of star. Telescopes give us precise, quantitative data well beyond what we have the capacity to perceive. It is the job of the modern astronomer to analyze that data.

The Effect of the Earth’s Atmosphere on Telescopes

The atmosphere of the Earth blocks certain wavelengths of electromagnetic radiation from space, but allows others to pass through unhindered. A perfect example of this is the atoms and molecules that make up the atmosphere (nitrogen, oxygen, carbon dioxide (CO₂), water (H₂O), and so on) effect certain wavelengths of Visible Light more than others. These atoms have a higher tendency to scatter blue light, bouncing it around within the atmosphere of the Earth, which is why the sky appears to be blue.

Because the atmosphere allows certain wavelengths of light to pass through and not others, this means that from the surface of the Earth, we are essentially blind in certain wavelengths. We can see very little about certain aspects of the universe while we are within Earth’s atmosphere.

The atmosphere of the Earth mainly allows Visible Light, Radio Waves, and some Infrared light to pass through. Ground-based astronomers are primarily are primarily involved in studying the universe on these frequency bands of EMR, since they observe the cosmos largely through two atmospheric windows — the visible light window (or optical window) and the radio window — with a little bit of Infrared also. Ground-based observations are ideally performed in dark locations with thin, dry, and steady air, far from city lights and pollution. These are the criteria for the sites where Astronomical Observatories are constructed, the most ideal places on Earth for astronomy. However these criteria best apply to…

Space. Space is the best possible location, the most ideal environment, for observing the universe. We have an unhindered view of the cosmos — no pollution, no lights, no technology that radiates energy, and no atmosphere in our way — meaning that the development of space tech for space-based observation has exponentially increased our ability to study the cosmos. In order to see beyond the atmospheric windows of visible light and radio, into the realms of X-Ray, UV, Gamma Rays, and Infrared in full color (so to speak) we need to be beyond the Earth’s atmosphere. Orbiting space telescopes are the pinnacle, but we can perform these observations from any space craft, rockets, and Moon-based observing stations in the future.

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Resources

1. Astronomy. Openstax.