On the feasibility of extra-solar planetary detection at very low ratio frequencies

Abstract

The search for extra-solar planetary systems remains an important, continuing, astrophysical problem as well as a primary step in the quest for knowledge of the existence of life in the universe.

In addition to the methods currently in use for detecting planets, there is the possibility of revealing the existence of planets in other stellar systems by observing their natural, non-thermal low-frequency radiation; this was suggested a few decades ago, but has not been attained so far.

Five planets in the solar system, including the Earth, are now known to produce low-frequency radiations in the kilometer to decameter wavelength range. These radiations are mainly due to processes occurring in the auroral regions of the planetary magnetospheres. Thus they might be encountered every time that a planetary magnetized body interacts with a stellar wind. Similar radiation, probably due to the same processes, is observed to come from the Sun and a number of stars smaller and cooler than the Sun, those that are known to have a magnetic field.

The intensity of the planetary radiation is high enough to be detectable, in a reasonable range of distance, with a large but feasible low-frequency radio telescope, operated on the ground, on the Moon or in space.

Taking into account the observed properties of the planetary radio emissions in the solar system, and the scaling rules which can be inferred from the plasma physics, we discuss the feasibility of such a detection.