Interference from a Star

We all know that it is imposibble to see a planet from other solar system
nomatter how powerfull a telescope might be.
Because the light from the Star is so bright that it cover-up the dim light
from the planet.

We also know that a Star emit radio wave.
Won't that radio wave from the Star cover-up the radio wave from the planet
where ET live?

cfs717 wrote:
We all know that it is imposibble to see a planet from other solar system
nomatter how powerfull a telescope might be.
Because the light from the Star is so bright that it cover-up the dim light
from the planet.

We also know that a Star emit radio wave.
Won't that radio wave from the Star cover-up the radio wave from the planet
where ET live?


With two or more telescopes (optical or radio), and good interferometry
between them, the light (or radio waves) from the star can be cancelled
to then reveal the weaker light from nearby planets.

This is already being done.


The better question is how much noise a star generates at the
frequencies that s@h are searching?

Good luck,
Martin


--
---------- Give a man a fish and you have fed him for today.
- Martin - Teach him how to fish and he won't bother you for weeks!
- 53N 1W - - Anon
----------

"c" == cfs717 writes:

c We all know that it is imposibble to see a planet from other solar
c system nomatter how powerfull a telescope might be. Because the
c light from the Star is so bright that it cover-up the dim light
c from the planet.

That's not quite accurate. Planets are dim in the optical and
near-infrared so one needs a fairly large telescope just to try to
detect them in the first place. The issue is how to prevent the light
from the star from "scattering" within the telescope and washing out
the star. If you have ever looked at an picture of a star, you've
probably seen spikes coming out of it. Those result from the optics
within the telescope, and they can easily obscure any nearby planet.
The effort in observing planets directly in the optical or
near-infrared focuses on how to reduce this "scattering" so that the
planet can be seen.

c We also know that a Star emit radio wave. Won't that radio wave
c from the Star cover-up the radio wave from the planet where ET
c live?

We hope not. The issue here is how are the ETs broadcasting their
radio waves. The Sun and other stars do produce radio waves, and, by
terrestrial standards, they are quite powerful. However, they
broadcast their power over many different frequencies. If an ET (or
us for that matter!) chooses a sufficiently narrow range of
frequencies on which to broadcast, outshining the star requires only
late-20th century technology.

By the same token, one can ask what would it take to outshine a star
in the optical or near-infrared? Again a star is fairly powerful, but
it shines continuously. If one emits pulses of light, it is possible
with late-20th century or early-21st century technology to outshine a
star for brief instants. This is the premise behind SETI at optical
wavelengths.

--
Lt. Lazio, HTML police | e-mail:
No means no, stop rape. | http://patriot.net/%7Ejlazio/
sci.astro FAQ at http://sciastro.astronomy.net/sci.astro.html

cfs717,
Stars do emit radio noise, but not uniformly, all across the radio
spectrum. We are listening in a "quiet part" of the radio spectrum,
thinking that aliens would choose to send a signal where it has a better
chance of being detected.
Listen to *these* stars; click the gray arrow buttons on this web site.
It takes a minute to load each one, but it's worth the wait.
http://www.jb.man.ac.uk/~pulsar/Educ...ds/sounds.html
Not even a strong, regularly pulsed radio signal from outer space is proof
of ETI. We continue the search here...
Cheers,
Red
--
*************************
Replies to me will bounce, unless you remove
the letter A from my email address.


cfs717 wrote:

We all know that it is imposibble to see a planet from other solar system
nomatter how powerfull a telescope might be.
Because the light from the Star is so bright that it cover-up the dim light
from the planet.

We also know that a Star emit radio wave.
Won't that radio wave from the Star cover-up the radio wave from the planet
where ET live?

These are pulsars. Dont you have a normal star in your basket? I'd
love to hear it.
Regards, mv
On Fri, 05 Dec 2003 07:27:29 -0700, red wrote:

cfs717,
Stars do emit radio noise, but not uniformly, all across the radio
spectrum. We are listening in a "quiet part" of the radio spectrum,
thinking that aliens would choose to send a signal where it has a better
chance of being detected.
Listen to *these* stars; click the gray arrow buttons on this web site.
It takes a minute to load each one, but it's worth the wait.
http://www.jb.man.ac.uk/~pulsar/Educ...ds/sounds.html
Not even a strong, regularly pulsed radio signal from outer space is proof
of ETI. We continue the search here...
Cheers,
Red
--
*************************
Replies to me will bounce, unless you remove
the letter A from my email address.


cfs717 wrote:

We all know that it is imposibble to see a planet from other solar system
nomatter how powerfull a telescope might be.
Because the light from the Star is so bright that it cover-up the dim light
from the planet.

We also know that a Star emit radio wave.
Won't that radio wave from the Star cover-up the radio wave from the planet
where ET live?

MV,
How about our own Sun? I'm not a radio addict, so I can't name the exact
frequencies now, but any short-wave radio or ham-radio operator can let you
listen to the radio noises of our nearest star. You do not need a dish
antenna for these nearby signals; any antenna (that can accommodate these
frequencies) will do.
Radio astronomers have "mapped" the sky at various radio frequencies, and
the radio star charts look rather different from the visible light star
charts.
Cheers,
Red
--
*************************
Replies will bounce, unless you remove
the letter A from my email address.

wrote:

These are pulsars. Dont you have a normal star in your basket? I'd
love to hear it.
Regards, mv

On Fri, 05 Dec 2003 07:27:29 -0700, red wrote:

cfs717,
Stars do emit radio noise, but not uniformly, all across the radio
spectrum. We are listening in a "quiet part" of the radio spectrum,
thinking that aliens would choose to send a signal where it has a better
chance of being detected.
Listen to *these* stars; click the gray arrow buttons on this web site.
It takes a minute to load each one, but it's worth the wait.
http://www.jb.man.ac.uk/~pulsar/Educ...ds/sounds.html
Not even a strong, regularly pulsed radio signal from outer space is proof
of ETI. We continue the search here...
Cheers,
Red
--
*************************
Replies to me will bounce, unless you remove
the letter A from my email address.


cfs717 wrote:

We all know that it is imposibble to see a planet from other solar system
nomatter how powerfull a telescope might be.
Because the light from the Star is so bright that it cover-up the dim light
from the planet.

We also know that a Star emit radio wave.
Won't that radio wave from the Star cover-up the radio wave from the planet
where ET live?

MV,
How about our own Sun? I'm not a radio addict, so I can't name the exact
frequencies now, but any short-wave radio or ham-radio operator can let you
listen to the radio noises of our nearest star. You do not need a dish
antenna for these nearby signals; any antenna (that can accommodate these
frequencies) will do.
Radio astronomers have "mapped" the sky at various radio frequencies, and
the radio star charts look rather different from the visible light star
charts.
Cheers,
Red
--
*************************
Replies will bounce, unless you remove
the letter A from my email address.

wrote:

These are pulsars. Dont you have a normal star in your basket? I'd
love to hear it.
Regards, mv

On Fri, 05 Dec 2003 07:27:29 -0700, red wrote:

cfs717,
Stars do emit radio noise, but not uniformly, all across the radio
spectrum. We are listening in a "quiet part" of the radio spectrum,
thinking that aliens would choose to send a signal where it has a better
chance of being detected.
Listen to *these* stars; click the gray arrow buttons on this web site.
It takes a minute to load each one, but it's worth the wait.
http://www.jb.man.ac.uk/~pulsar/Educ...ds/sounds.html
Not even a strong, regularly pulsed radio signal from outer space is proof
of ETI. We continue the search here...
Cheers,
Red
--
*************************
Replies to me will bounce, unless you remove
the letter A from my email address.


cfs717 wrote:

We all know that it is imposibble to see a planet from other solar system
nomatter how powerfull a telescope might be.
Because the light from the Star is so bright that it cover-up the dim light
from the planet.

We also know that a Star emit radio wave.
Won't that radio wave from the Star cover-up the radio wave from the planet
where ET live?

These are pulsars. Dont you have a normal star in your basket? I'd
love to hear it.
Regards, mv
On Fri, 05 Dec 2003 07:27:29 -0700, red wrote:

cfs717,
Stars do emit radio noise, but not uniformly, all across the radio
spectrum. We are listening in a "quiet part" of the radio spectrum,
thinking that aliens would choose to send a signal where it has a better
chance of being detected.
Listen to *these* stars; click the gray arrow buttons on this web site.
It takes a minute to load each one, but it's worth the wait.
http://www.jb.man.ac.uk/~pulsar/Educ...ds/sounds.html
Not even a strong, regularly pulsed radio signal from outer space is proof
of ETI. We continue the search here...
Cheers,
Red
--
*************************
Replies to me will bounce, unless you remove
the letter A from my email address.


cfs717 wrote:

We all know that it is imposibble to see a planet from other solar system
nomatter how powerfull a telescope might be.
Because the light from the Star is so bright that it cover-up the dim light
from the planet.

We also know that a Star emit radio wave.
Won't that radio wave from the Star cover-up the radio wave from the planet
where ET live?

Wasn't it cfs717 who wrote:
We all know that it is imposibble to see a planet from other solar system
nomatter how powerfull a telescope might be.
Because the light from the Star is so bright that it cover-up the dim light
from the planet.

We also know that a Star emit radio wave.
Won't that radio wave from the Star cover-up the radio wave from the planet
where ET live?

The radio output from a star has an extremely wide bandwidth so although
the total power output is extremely high, the output at any one
individual frequency is quite moderate.

An artificial signal intended to be used as an interstellar signal would
be designed to have a very narrow bandwidth. So although the total
amount of power is a small fraction of the total power output of the
star, the power at that particular frequency can be much higher.

For example, the FAQ mentions that Arecibo can be used to transmit with
a band width of 0.01 Hertz, whereas the emissions from a star would be
typically spread over many GigaHertz, so only a few quadrilionths of the
star's output is likely to fall in the particular 0.01Hz band chosen by
ET for their signal.

--
Mike Williams
Gentleman of Leisure

cfs717 wrote:
We all know that it is imposibble to see a planet from other solar system
nomatter how powerfull a telescope might be.
Because the light from the Star is so bright that it cover-up the dim light
from the planet.

We also know that a Star emit radio wave.
Won't that radio wave from the Star cover-up the radio wave from the planet
where ET live?


With two or more telescopes (optical or radio), and good interferometry
between them, the light (or radio waves) from the star can be cancelled
to then reveal the weaker light from nearby planets.

This is already being done.


The better question is how much noise a star generates at the
frequencies that s@h are searching?

Good luck,
Martin


--
---------- Give a man a fish and you have fed him for today.
- Martin - Teach him how to fish and he won't bother you for weeks!
- 53N 1W - - Anon
----------