Astronomy Picture of the Day 5-28-02

NASA ^ | 5-28-02 | Robert Nemiroff and Jerry Bonnell

[petuniasevan]

"Seeing with different eyes" has enabled us to discover a strange and wonderful universe we could never have imagined! Kudos to all who work the long hours of tedium and painstaking work to bring us the images we take for granted!

Get on the APOD PING list!

[petuniasevan]

APOD PING!

[wafflehouse]

cool! those things are very impressive up close

[petuniasevan]

And a very personal APOD PING for you, RA!

[petuniasevan]

That they are! It looks like about 4 stories just to the base of the dish!

[RadioAstronomer]

Thanks for the ping! I have been there. The VLA is an impressive place indeed! :-)

[kayak]

Hello, friend!

I was going to ping you to this but I see that petuniasevan beat me to the punch ...... :-)

[RadioAstronomer]

Hi long time no speak! :-) I have been away on a project. Thank you so much for the hello!!

[RightWhale]

Water on Mercury! Mars will be too easy to build a base, not a real challenge. Let's go to Mercury.

[altair]

Very cool.

[kayak]

I knew I hadn't seen you around in a while but thought maybe our paths just weren't crossing. Glad to know that you're ok.

[RadioAstronomer]

Thanks! :-) I am fine and am back posting! LOL!!!! How are you all doing?

[kayak]

We're hanging in there ....... :-)

[sleavelessinseattle]

WOW, Honored to meet you RA...I like to think that finding a woman who will put up with a 42 year old adolescent is a tough job, but SETI is some big piece a pie on a plate...Do you ever sit up at night with a pang of concern that we're listening on the wrong spectrum??? I keep hearing about vacuum energy and possible interferance effects observed in the Wave/Particle behavior of light with particles in "nearby" dimensions...What if Humanity just missed quantum communication science, and we're searching around while all the "smart" entities have the Celestial equivalent of ATT Broadband??? If you just read that hairball on your coffee break at work...you're under no obligation to ruin your infrequent "down time" by trying to "irradiate"(as opposed to illuminate, want to be spectrally correct, given your area of expertise!) me .;-D

[RadioAstronomer]

Do you ever sit up at night with a pang of concern that we're listening on the wrong spectrum???

Hi! thanks for the ping. Indeed the choice of frequencies is rather an interesting challenge:

There are two real sources of noise that limits the radio astronomer's ability to search for very weak signals. 1) The Galactic noise halo interferes with us below 1Ghz and noise due to earth's atmosphere interferes with us above about 10Ghz. This pretty much keeps all SETI searches (at least radio ones) between 1 and 10Ghz. Between the two, the noise is around the 2.7K background from 1.4 to 7Ghz. This is why most of the SETI searches are around the frequencies that the OH (hydroxyl) and H (hydrogen) molecules masers emit. This is the so-called water hole.

Most of the SETI searches are near the 21cm band. Since this is one of the coveted frequencies of radio astronomers, we have international treaties to not broadcast at this frequency at all. So here we are looking for signs of a narrowband signal heralding the fact that intelligent life is not wholly constrained to this little planet at this frequency. Now if any intelligent race develops radio and radio astronomy, they too will recognize the importance of this 21cm band. And they also may instigate a SETI search using this frequency. So here is the question. Would they hear us at that frequency? It is the one that we are not transmitting on at all. I could just see 500 races all looking for each other at the very frequency none of them are transmitting on due to the very nature of the importance of that frequency to the exploration of the universe

Thus our search is approximately 3 times that frequency and we are looking at over 3 million channels simultaneously.

[RadioAstronomer]

BTW, thanks for the compliments! :-) I really hope radio is the medium that will finally let us know that we are not the only tool builders in this universe.

[sleavelessinseattle]

This is why most of the SETI searches are around the frequencies that the OH (hydroxyl) and H (hydrogen) molecules masers emit. This is the so-called water hole.

I believe the 21 cm band is the "hydrogen" band...My problem is that I've never understood why that section is quiet? Does a Maser Absorb hydrogen frequency broadcasts? Filtering noise of natural origin? I am totally ignorant of what a maser is and how it "clears" the water hole...If you're ever in Seattle, I will be your Paspartu!!! Thanks in Advance....and Good Morning!

[sleavelessinseattle]

There are two real sources of noise that limits the radio astronomer's ability to search for very weak signals. 1) The Galactic noise halo interferes with us below 1Ghz and noise due to earth's atmosphere interferes with us above about 10Ghz. This pretty much keeps all

I have now entered the realm of far out ideas...We're not listening in the above 10GHZ range because Earth's atmosphere fuzzes up reception...We're blind to any "tool users" that operate outside of a gaseous "noiseball" planet. The mind reels! I can see I'm going to have to go over your answers to grok all the implications...This is so like Kennedy's moon speech..."We choose to do it because its HARD"...\:-D tip of the lid...

[RadioAstronomer]

I believe the 21 cm band is the "hydrogen" band...My problem is that I've never understood why that section is quiet? Does a Maser Absorb hydrogen frequency broadcasts?

The Neutral hydrogen (H1) in the interstellar regions (mostly contained in the plane of the galaxies) emit at the 21 centimeter band due to its microwave transition. We then are able to us radio telescopes to detect this emitted frequency and map the H1 regions. This 21 cm band fall within the quiet band from about 1 to 10Ghz.

This emission process by the Hydrogen is a Maser (Microwave Amplification by Stimulation Emission of Radiation).

[RadioAstronomer]

I have now entered the realm of far out ideas...We're not listening in the above 10GHZ range because Earth's atmosphere fuzzes up reception...We're blind to any "tool users" that operate outside of a gaseous "noiseball" planet. The mind reels! I can see I'm going to have to go over your answers to grok all the implications

This is why it would be marvelous to have a radio telescope array on the far side of the moon. Not only would there be no atmosphere to contend with, but the moon would block all earth generated interference as well.