"Who's Looking at You, Kid?": SETI Advantages near the Ecliptic Plane

Steven Kilston, Seth Shostak, Richard Conn Henry

Session 19. Future SETI: Technologies, Techniques and Strategies

Astrobiology Science Conference 2008

2008 April 14 - 17, Santa Clara, California


Recent knowledge about real extrasolar planets, and about telescopes
needed to see more of them, can affect our approaches to SETI. This
knowledge implies that ETI following technology paths like ours for
observing planets may find us more easily if they are located in
particular directions. Our SETI efforts should perhaps concentrate on
those directions where ETI will most likely have an idea we're here and
can then send us efficiently focused communications signals we can

We expect to first observe terrestrial exoplanets by seeing them
transiting their host stars. The COROT and Kepler missions may soon
find these planets out to 1 kpc. The advantage in distance over other
methods, more than 30 times, puts nearly 20,000 times as many stars in
range of our earliest (transit) instruments for detecting Earths. We
must reside in a stripe of sky 0.5 degree wide centered on the ecliptic
of another Earth to see it transiting its sun. That stripe occupies just
1/230 of the whole sky, but for observers like us the transit method
could still find 20,000/230 = 90 times as many Earths as any other
method yet proposed.

Therefore, distant ETIs first finding our planet are 90 times more
likely to be in the narrow stripe straddling our own ecliptic than in
all the rest of the sky. SETI searches over that stripe could be 90
times more efficient in detecting signals than are whole-sky searches.
Similarly, active SETI transmissions toward that stripe may reach
suitable targets best.