How is it confirmed that a radiation source (not in visible light) is either terrestrial or celestial?
If in-depth explanation and/or references are possible, I would be grateful.
Asked
Active
Viewed 76 times
2 Answers
3
There's a few indicators where a source is located:
Direction: Radio waves are just like light waves only with longer wavelength: you have to look into the direction of the source in order to see it. Terretrial sources usually are not high up in the sky.
Apparent movement: Another important aspect is Earth's rotation: the sky rotates with respect to Earth's surface. Thus if the source moves with the rotation speed of Earth and remains stationary in a celestial reference frame, it is very likely a source outside of Earth - and vice versa.
Location / Parallax: If you have several receivers, they will disagree on the direction a signal comes from, but will agree much better the further away a source is. Celestial sources are far away enough that the direction will be (nearly) identical. The amount of disagreement, the so-called parallax gives you a geometric indicator about the distance to the source.
planetmaker
- 19,369
- 3
- 46
- 80
-
@a_donda https://i.stack.imgur.com/M2Ygf.jpg from China Built the World’s Largest Telescope. Then Came the Tourists also see China Finds Phone-Wielding Tourists and Telescopes Don't Mesh – uhoh Aug 02 '20 at 07:26
-
Haha, see ? Public access to the Roque de los Muchachos observatory is closed from 19:00 to 07:00. A ranger watches that all have left. Cars passing on the mountain road shall not use full beam. – Aug 02 '20 at 08:38
2
To planetmaker’s excellent answer, add periodicity. This is useful if you can’t measure direction at all.
A signal whose intensity varies regularly over a 24-hour period is likely to be terrestrial.
A signal whose intensity varies regularly over a 23-hour-56-minute period is likely to be celestial.
For signals which (for whatever reason) can only be observed at a particular time of day - say, midnight - a 12-month period suggests “celestial” but you have to be careful because the weather has a 12-month period too, in most places.
Martin Kochanski
- 1,820
- 10
- 14
-
https://en.wikipedia.org/wiki/Peryton_(astronomy)#Identification and https://www.nature.com/news/microwave-oven-blamed-for-radio-telescope-signals-1.17510 – uhoh Aug 02 '20 at 07:41