Update: "Will amateur radio astronomers be the first to directly detect extrasolar planets?"

This news release reported on the creation of a "virtual telescope" to
combine the radio signals from widely separated radio telescopes in
real time over the internet:

Date Released: Friday, October 08, 2004
Source: Jodrell Bank Observatory
Astronomers Demonstrate a Global Internet Telescope
http://www.spaceref.com/news/viewpr.html?pid=15251

Something like this would be required to implement the method of
detecting extrasolar planets from their radio emissions using very
many widely separated dipole arrays, as discussed below. The report
noted the data was transmitted over the high-speed internet networks
that most universities world-wide are connected to.
The idea would be for thousands of universities world-wide to set-up
dipole arrays with several thousand dipoles each. The dipoles are
quite cheap consisting simply copper wire, so there is no problem of
the cost of the arrays for each university, and any empty athletic
field would do to hold the arrays.



Bob Clark


-------------------------------------------------------------------------------
From: Robert Clark )
Subject: Will amateur radio astronomers be the first to directly
detect extrasolar planets?
Newsgroups: rec.radio.amateur.space, rec.radio.amateur.antenna,
sci.astro, sci.astro.seti, sci.space.policy
Date: 2001-05-23 11:15:07 PST


The existence of extrasolar planets has been inferred from the
wobbling seen in some stars. Their actual light still has not been
detected or distinguished from that of their parent stars.
The long wavelength radio bursts that emanate from Jupiter have led
to suggestions that extrasolar planets might be detected by searching
for such bursts in the vicinity of stars:

Opening a New Window on the Universe:
High Resolution, Long Wavelength Radio Astronomy,
2.5.2 Extrasolar Planets,
by Joseph Lazio
http://rsd-www.nrl.navy.mil/7213/laz...eb/node34.html

However, sensitive searches have so far failed to detect them. This
is undoubtedly due to distance attenuation for such planets
light-years away. The distance to Jupiter ranges up to 9 x 10^8 km. A
star 10 light-years away is at 9 x 10^13 km, a factor of 10^5 larger
than the Jupiter distance.
The Jovian radio bursts have been detected by amateurs with simple
dipole antennas:

Radio-Jupiter for Amateur Observers, By Jim Sky
[expired link: http://******.com/SAS/bulletin/Sas44....html#Jupiter]
try instead NASA Radio JOVE Project Home Page,
http://radiojove.gsfc.nasa.gov/

PROJECT P5-2. JUPITER-IO MAGNETOSPHERE RADIO NOISE
http://www.elmag5.com/jupiter-io.htm

With its Radio JOVE project NASA also distributes low-cost dipole
kits to schools:

How To Hear Radio Signals From Jupiter
http://www.spacetoday.org/SolSys/Jup...iterRadio.html

Radio JOVE
http://spacescience.com/headlines/y2...may_1.htm?list

The proposal is for amateur radio astronomers to set up arrays of
such low cost dipole antennas world-wide. The T-shaped dipoles have
the advantage of steerability, but the vertical dipoles have the
advantage of simplicity and low cost for setting up large arrays. An
example of a steerable dipole array is the one that first discovered
the Jovian decametric emissions:

The Discovery of Jupiter's Radio Emissions
How a chance discovery opened up the field of Jovian radio studies
http://radiojove.gsfc.nasa.gov/libra...discovery.html

The signals from the various arrays would be combined digitally to
form a world-wide radio telescope. The large-wavelengths being
detected simplify the task of combining the signals
interferometrically. GPS transmitters are now available that can give
locations to within inches:

NASA satellite technology goes down on the farm
http://www.spaceflightnow.com/news/n0105/11farm/

The clocks in such transmitters also provide timing at better than
nanosecond resolution.

The signal strength for Jupiter at 10 light-years would decrease as
the square of the distance, so would be smaller by a factor of 10^10.
However, the extrasolar Jovian planets detected so far have been close
in to their primaries and are expected to produce stronger radio
emissions than Jupiter, perhaps, 100 to 1000 times more intense. Using
the optimistic estimate of 1000 times greater intensity would require
100,000 separate arrays with 100 dipoles or 10,000 arrays with 1,000
dipoles to detect such emissions.



Bob Clark

-------------------------------------------------------------------------------

"RC" == Robert Clark writes:

RC This news release reported on the creation of a "virtual
RC telescope" to combine the radio signals from widely separated
RC radio telescopes in real time over the internet:

RC Date Released: Friday, October 08, 2004
RC Source: Jodrell Bank Observatory
RC Astronomers Demonstrate a Global Internet Telescope
RC http://www.spaceref.com/news/viewpr.html?pid=15251

Note that these "virtual telescopes" have been created for something
like 60 years, or if one restricts attention to global telescopes, for
40 years. What's new (and impressive) about the work reported in the
above press release is the real-time aspect.

RC Something like this would be required to implement the method of
RC detecting extrasolar planets from their radio emissions using very
RC many widely separated dipole arrays, as discussed below. The
RC report noted the data was transmitted over the high-speed internet
RC networks that most universities world-wide are connected to. The
RC idea would be for thousands of universities world-wide to set-up
RC dipole arrays with several thousand dipoles each. The dipoles are
RC quite cheap consisting simply copper wire, so there is no problem
RC of the cost of the arrays for each university, and any empty
RC athletic field would do to hold the arrays.

Since I wrote some of what is described below, allow me to comment.

RC The existence of extrasolar planets has been inferred from the
RC wobbling seen in some stars. Their actual light still has not been
RC detected or distinguished from that of their parent stars. The
RC long wavelength radio bursts that emanate from Jupiter have led to
RC suggestions that extrasolar planets might be detected by searching
RC for such bursts in the vicinity of stars:

RC Opening a New Window on the Universe: High Resolution, Long
RC Wavelength Radio Astronomy, 2.5.2 Extrasolar Planets, by Joseph
RC Lazio
RC http://rsd-www.nrl.navy.mil/7213/laz...eb/node34.html

RC However, sensitive searches have so far failed to detect
RC them. This is undoubtedly due to distance attenuation for such
RC planets light-years away. The distance to Jupiter ranges up to 9 x
RC 10^8 km. A star 10 light-years away is at 9 x 10^13 km, a factor
RC of 10^5 larger than the Jupiter distance.

That's the real problem. A real-time network of globally distributed
telescopes sounds neat, but it may be a bit of overkill for this
idea. What is needed is sheer collecting area, i.e., lots and lots of
dipoles. Resolution (which is what one obtains from a global
telescope) is nice, but for a project like this, a telescope about 100
km across would be more than enough. The objective is not to
resolve or separate (in an angular) sense the planet and the star.
The objective is to have enough collecting area or sensitivity so that
one can have a reasonable hope of detecting these planetary emissions,
given their large distances from us.

Indeed, there are some existing searches underway using both the VLA
and the GMRT. Neither of these telescopes is more than about 30 km
across. The real problem is that their collecting areas may not be
sufficient. The proposed Long Wavelength Array (LWA) might be able to
detect extrasolar planetary emissions, but it will have (we hope!)
something like 13,000 dipoles (and even that may be a bit lower than
one would like). If one wanted a rough number, I'd say 15,000 to
20,000 dipoles would be a good number.

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