Differences

This shows you the differences between two versions of the page.

--- un:ra [2024/05/29 00:57] – created asad
+++ un:ra [2025/08/05 07:39] (current) – removed asad
@@ Line 1: / Line 1: @@
-====== Radio astronomy ======
-Human eye can detect [[electromagnetic radiation]] within a narrow range from 400 nm to 700 nm, but astronomical objects emit light of all wavelengths from picometer-length gamma rays to a meter-length radio waves. Radio astronomy deals with celestial electromagnetic radiation at radio wavelengths, from 0.3 mm ($\nu=c/\lambda=1$ THz) to 30 m (10 MHz).
-{{https://www.cv.nrao.edu/~sransom/web/x374.jpg?nolink&800}}
-Atmospheric opacity and quantum noise determine the boundary between far-infrared and radio astronomy at 1 THz and the ionosphere reflect back all waves longer than 30 m. Below 2 MHz even our Galaxy becomes an absorber, its ionized gas prevents radio radiation from propagating.
-If we had radio eyes and looked at the sky, the [[Sun]] would still be very bright, but different. Its non-thermal emissions would dominate over the thermal [[blackbody]] radiation, the corona would be visible as a hazy envelope. The [[planets]] would be seen not in reflected light, but in their own invisible light. The [[Milky Way]] would shine not because of its [[stars]], but mainly because of the innumerable high-speed electrons in its interstellar medium. Instead of stars, the night-sky would be filled with compact active galaxies.
-Only radio and optical astronomy can be done from the ground efficiently.