Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: syhprum on 04/07/2008 09:23:03

Title: Effective radiated power
Post by: syhprum on 04/07/2008 09:23:03

A pair of eclipsing pulsars have been monitored for the last five years to confirm general relativity as regards precession.
These pulsars are a long way away I would be interested in estimates of the ERP of the radio emission's and how this compares with what SETI have available

Title: Effective radiated power
Post by: Alan McDougall on 04/07/2008 17:28:11

I don't get your point all radiation ,light and otherwise would recede at the same fundamental constant

Title: Effective radiated power
Post by: graham.d on 04/07/2008 22:25:59

Are you speaking of B1957 +20? I am unsure of how this relates to SETI. There are a handful of eclipsing pulsars and I am sure there is reported information as to their ERP. This normally correlates to their estimated distance from the dispersion of the emitted radiation but because there are so few it may not be very relevant.

As all these pulsars are within our galaxy, Hubble recession is not an issue.

Title: Effective radiated power
Post by: Soul Surfer on 04/07/2008 23:47:15

There appears to be some fundamental misunderstandings between the questions and the answers here.

Firstly the reference should be quoted or the observations described in a bit more detail.  I presume the abbreviation ERP means Effective radiated power  A term used in relation do radio transmitters.  This is valid because most pulsars are observed at radio frequencies and not optically.

What I think syhprum is asking is:- we are listening to radio signals from a great distance in some detail.  How does the power in this radio signal relate to any power we could transmit from the earth?

The truth is that any signals emitted from a star are probably many orders of magnitude greater than the best that we could do principally because even though neutron stars are quite small  The energies involved are still vastly greater that the sort of thing that we could generate with the most powerful signal sources on the earth.

Title: Effective radiated power
Post by: Pumblechook on 05/07/2008 00:08:50

Our Sun puts out nearly 400 trillion-trillion Watts.  4 x 10^26 Watts.   I don't know how the stars we can see compare and how far the Sun could be seen or detected??   

Earthly transmitters reach the low MegaWatts of ERP so the Sun is of the order of 10^20 times more powerful than our most powerful transmissions.  100,000,000,000,000,000,000  times.

Our radio broadcast transmissions are far too weak to reach much more than 100 Million Km.  TV would be far less. 

Title: Effective radiated power
Post by: syhprum on 05/07/2008 17:49:00

I believe that the Acribo radar installation has a 1 Mw transmitter and an antenna gain of 60 db giving a ERP of 1000 Gw, infinitesimal compared with that of pulsars but I have been unable to find any actual estimates of their power

Title: Effective radiated power
Post by: Alan McDougall on 05/07/2008 20:54:31

Quote

I believe that the Acribo radar installation has a 1 Mw transmitter and an antenna gain of 60 db giving a ERP of 1000 Gw, infinitesimal compared with that of pulsars but I have been unable to find any actual estimates of their power

In 1974 the Acribo telescope pulsed out on very comprehensive digital message towards somewhere in the cosmos.

Of course if any sentient being receives it humanity will long been gone by then.

I will look it up.