Expert: Tom Whiting - 2/22/2008

Question
Hi, I have a few questions:

1. How can using different portions of the electromagnetic help us with
astronomical observations?

2. How does the atmosphere affect the image viewed through a telescope?

I have been searching and searching for some type of explanation but I can't find anything. If you can assist me it would be greatly appretiated.  

Answer
Hi Betty,
Thanks for the excellent question.  Hundreds of years ago, Galileo
didn't know that "light" came in with differents forms....different
wavelengths of photons. They thought that visible light was all there
was, because stuff like radio, Ultraviolet, X-Ray, Gamma Rays, hadn't
been discovered as yet.  But in the 20th century, we discovered
radio, Infrared (below the visible) and the others above the visible
light range....we just can't see those wavelengths with our eyes.
It was quickly learned that all these photons are just the SAME photon of light at different (higher or lower) wavelengths,
and that's all, otherwise, it's all the same.
So now we have radio telescopes, Infrared (read that heat) telescopes, UV telescopes, X-ray telescopes, and gamma ray telescopes. The last 3 have to be in space, in orbit, because most
of the UV, and all the X-ray and gamma rays, don't make it down
through the atmosphere. The air blocks them. (Some small amount
of Ultraviolet makes it down to give us sunburn, but it's really
a very small amount, the ozone blocks most of the UV radiation.)
So all those types of scopes HAVE to be up in orbit, because they just wouldn't work on the surface of the Earth due to our atmosphere interfering...stopping that light from reaching the surface.



Ok, how does it help us?  Well, different bodies give off different
amounts of these "different" high energy photons, and by gathering them and analyzing them, we learn far more about those objects than if we didn't collect it.  Some objects, in fact, only radiate (give off)infrared energy (brown dwarf stars, for instance)...others only
give off high energy photons (X-ray and gamma ray) like 2 merging
neutron stars, for instance, so with those high energy telescopes,
we can "see" those objects and events, and study them.  Otherwise,
we couldn't. The most distant galaxies, out there beyond 10 billion lightyears, many are receding so fast from us, that even their visible light is red-shifted far down into the infrared and even radio wavelengths, so we can "see" them at those wavelengths where they are now, as opposed to visible light.  The ones we see in visible light now...is actually the Ultraviolet and X-ray radiation red-shifted down into the visible light spectrum!!  (This is called...visible light dropout)! As we go out even further, we'll
soon experience "Infrared dropout". So see, we need those...other
wavelength telescopes! Even the remnant visible light radiation from
the Big Bang can be "seen" redshifted clear down at 1.1 mm microwave radio wavelength, as discovered by Arno Pensias and Robert Wilson of Bell Labs back in 1965, proving the Big Bang event with some HARD evidence that can be taken into a...Court of Law!!
So we can learn much more about our Universe by collecting and analyzing these....other photons of light.

2.  It's all resolution...We on the surface live at the bottom of a 'swimming pool' our atmosphere.  If someone is swimming at the top, like high altitude winds or the Jet Stream, OR there is dust and water vapor blocking our view, then our view of the night sky is not the best. Things like that interfere with our views.  By placing telescopes in orbit, in space above our atmosphere, then they avoid all those problems.
It's called 'resolution'...or sharpness of the object being viewed.
All Earthbound telescopes are limited in resolution by our atmosphere, but an orbiting telescope in space, is not limited in
resolution. (sharpness).  So that's the big advantage there. And,
obviously, it's well worth it...that's why we put them there.

Hope all this helps,
Clear Skies,
Tom Whiting
Erie, PA