I would have assumed that the brightest radio source in the Universe is a quasar of some kind (perhaps 3C 273) given that the average pulsar has luminosity of $~10^{40} \text{Watts}$ and this is the brightest (optically) and is radio loud.

My professor seems to be of the opinion that the Arecibo message is louder, but that does not seem to pass the straight face test, given that it was only transmitted at a power of only $1\text{MW}$, and only a very small fraction of the pulsars output (a mere $1/10^{34}$th) would be sufficient to outshine the message.

Is one of these the brightest radio source in the universe (excluding the Big Bang if it matters), or is it something else entirely?

Additionally, is Watts even the right unit to be measuring this in?

Update: Here is the text of the question (it was a true/false, and the answer is true):

In 1975, Frank Drake and Carl Sagan sent a message in to the Universe, directed to extraterrestrials, from the radio telescope at Arecibo in Puerto Rico that, for a brief time, made the Earth the brightest radio object in the Universe.

  • $\begingroup$ I believe what your professor meant was that it was the brightest radio source per area size it was transmitted from (118 acres or 48 ha)? $\endgroup$
    – TildalWave
    Dec 12, 2013 at 4:15
  • $\begingroup$ @TildalWave, I think even per unit area it would fail pretty terribly (both from a laser perspective, and a pulsars are not that much bigger in surface area terms) $\endgroup$
    – soandos
    Dec 12, 2013 at 4:24
  • $\begingroup$ Good points (no pun LOL), but why not ask your professor what he meant? Are you sure he was not referring to the Wow! signal response from 2012? Or narrowband strength? $\endgroup$
    – TildalWave
    Dec 12, 2013 at 4:31

1 Answer 1


1MW of transmitted power is very modest by RADAR terms, to give one example. Thus, you probably need to establish what exactly your professor means by "brightest" (may it be a specific wavelength or point in time, or some other definition). Otherwise, there's no reason to believe that Arecibo transmission was any special or outstanding from radio engineering stand point, while there were such nice toys operating at the very same time:



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