Let us take a look at some of the astronomical instruments and understand how they aid in optical astronomy.
“ If I had a time machine, I’d visit Marilyn Monroe in her prime or drop in on Galileo as he turned his telescope to the heavens”
What do you see as you embrace the heaven’s above?
Sure thing, we are all just so amused by the splendid night show that our dear cosmos brings for us.
Stars participating in their little constellation drama, galaxies spiraling art, oh and there comes the spotlight, the moon, planets, clusters, nebulae, the sparkling fireworks, the meteorites and just so much more we don’t even know.
But you know what, here is the sad part. Our eyes are sensitive to only a part of the entire electromagnetic spectrum. And that is why we have to make use of some astronomical instruments
Also called the visible spectrum, the light of the wavelength of 400nm (violet)-700nm (red) is the only part of the electromagnetic spectrum that is visible to us.
How does it affect us? Well, it doesn’t affect normal people in any manner but if you are in the field of optical astronomy, it matters a lot (I mean lots and lots).
Optical astronomy is a part of astronomy that uses optical astronomical instruments like mirrors, lenses and solid state detectors to observe light from near-infrared to near-UV wavelength.
Most of the celestial objects, members of our dear cosmos radiate at wavelengths that our eyes cannot perceive. This is where we use telescopes equipped with sophisticated devices that help to detect these types of wavelengths of light.
How does it help us?
If you want to know better about any object in the universe you have to go there and dug a little right?
Well, not at all practical!
We can completely discard this limitation by using telescopes and instruments that detect different wavelengths.
By measuring the wavelength or the frequency of light emitted by a celestial body, we can study just so much about its nature. And of course, going to a star and getting data, much of a fantasy!
This is how it all works…
The astronomical instruments come as add on to the telescopes. They sense the light they are sensitive to and send the collected data to a computer which then decodes it into arbitrary colors that we can see.
Take the Hubble space telescope for instance. It can detect wavelengths from about 0.1150 to 2 micrometers.
Astronomers then use the collected data to determine the various parameters of the body like its age, temperature, distance, velocity, and composition.
Different wavelengths and who emits them…
Gamma rays –
It has the shortest wavelength in the electromagnetic spectrum and the highest frequency. The wavelength is shorter then 0.01nm.
Gamma rays originate from nuclear reactions and processes taking place in pulsars, quasars, and black holes. In simple words, gamma rays participate in ultra-high energy matters. So yes they like to party hard.
0.01 nm-10 nm. Where they party? Superheated gas from exploding stars and quasars, where temperatures are near a million to 10 million degrees.
UV radiation –
10nm – 310nm
found in hot stars.
Visible light –
400nm – 700nm
Source – heat. For example, our sun emits most of its radiations in the visible spectrum.
710nm – 1 mm.
Even here the source is “heat” but the intensity is quite low. Our bodies give IR(infrared) at a temperature of 37deggre Celsius, reaching a peak intensity of 900 nm.
With a wavelength longer than 1mm, it has one of the longest wavelengths in the entire electromagnetic spectrum.
But as the rules go, if you want to have enough of something, you have to let go of other things. So as result radio waves have the least energy and the lowest temperature.
We can find them everywhere. It is like the background radiation of the universe. Originate from the remnants of supernovae and we also make its use to send radio waves signals which then get converted into sound.
Types of observational astronomy…
Now depending upon the wavelength you want to observe, there are different types of observational astronomy.
Oh and by the way did I mention? Observational astronomy is a division of astronomy that is concerned with recording data about the observable universe. Studying celestial objects with the help of telescopes and other astronomical instruments.
Radio emissions can be seen in various celestial objects like stars and phenomena like quasars and pulsars.
Here is a little fun fact, the discovery of cosmic microwave background radiation, which was regarded as the evidence for the big bang was made through Radio Astronomy.
Firstly, when it comes to a radio signal and visible light it gets relatively easier to make observations. This is because the atmosphere is almost transparent for the wavelengths that it requires to detect.
Therefore mostly we can see that optical and radio astronomy can be performed with ground-based observatories. Otherwise, the observatories are located at very high altitudes to minimize the effects of absorption and distortion caused by the earth’s atmosphere.
You will always see infrared observatories located in dry places and at high altitudes, and if that still doesn’t work, you guessed it, space!
This is because wavelengths like infrared are highly absorbed by water vapors which consequently makes it practically impossible to make observations.
But what if the atmosphere acts like a wall, which it does for wavelengths like those of x-rays, gamma-rays, ultraviolet rays and far-infrared. In such cases, we are compelled to launch the observatories in orbit. Their observations are carried out from balloons or in space.
Astronomical instruments have made it easier to understand the working of the cosmos.
There are different types of observational astronomy based on what you want to observe.
If observing the night sky fascinates you, and you want to learn about telescopes for the same, you can check out this video.
Sahil Asolkarwriter and co-founder
Sahil Asolkar is a writer, poet, and shows a good interest in astronomy. His work can be seen in the articles he writes for Astronomiac.
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