Like looking for the proverbial needle in a haystack â€“ the search for extrasolar planets is proving to be more difficult than previously thought. For decades researchers have believed that there was a solar sweet spot within star systems that was crucial for the water to exist in a liquid form â€“ a prerequisite for life as we understand it. In the last 2-3 years however it is now understood that the definition of what could potentially make for a habitable planet is far rarer than the original simple models would have predicted.
Primary among these influencers is the concept of tidal forces between a star and its planets â€“ known as tidal locking. Tidal locking occurs when the rotation of a planetary body matches its orbital period similar to how the moon always shows the same face to the earth even though the moon is rotating as it revolves around the earth. This effect means that extrasolar planets which are tidally locked with their stars, even though they may exist in the â€œhabitableâ€ zone would not be suitable for life as the persistent heating of one face of the planet would eventually boil off any potential atmosphere â€“ thereby rendering the planet inert to the development of life (See link).
By the same token â€“ planets that revolve too fast may also be unable to support life â€“ or at the very least such rotation vs planetary shape may play a role in the ability of life to develop. While not directly argued by Donald Hamilton, the shape of a planetary body that is spinning rapidly would force more material (including water and atmosphere) towards the equator there by rendering any possibility of uniform atmosphere creation almost impossible until such time as the planet could take on a more spheroid shape.
Such atmosphere would only be protected in as much as there would be a viable magnetic field available to ensure that plasma from the solar wind does not come in contact with the planetâ€™s troposphere or stratosphere and thereby strip ions necessary for atmospheric collection to occur (See link,Â link).
The more pressing challenge however is that in all of these endeavours to try to find additional habitable planets, almost all techniques focus on two aspects that almost ensure defeat even before analysis has started. The first is the requirement to identify planets based on indirect observation requiring either solar transits or wobbles. Rare is the ability to see a planet directly such as is the case with the gas giant orbiting the star Î² Pictoris.
New Methodology Proposal
One of the more interesting notions however that I would like to put forward is that an adaptation of a technology which is used to identify magnetic fields in deep space could be used to examine candidate solar analogs which can be seen perpendicular to our point of observation similar to Î² Pictoris.
Scientist for UCLA have refined a technique for examining super massive black-holes for signs of primordial magnetic fields between galaxies. The technique involves examining images for blurriness caused by deflection of electrons and positrons that would otherwise render a more crisp image.
What I am proposing is to use a similar technique in order to examine the background radiation emanating from behind a candidate solar analog. Similar to gravitational lensing, using a known fixed point in space should render parts of the resulting image â€œblurredâ€ when taken at different points in time. Since the original study claims to be able to detect â€œfemto-Gauss” strength at just one-quadrillionth of the Earth’s magnetic field, it should be possible to use this technique to examine nearby solar analogs for confirmation of planetary systems. Â
Specifically â€“ Solar systems including 61 Vir, HD 1461, 23 Librae, and Î² PictorisÂ would be primary candidates for confirmation of the process as each of these systems are close enough to make for a reasonable test of the hypothesis and have known planets which have been verified by the international community.
While the technique would not necessarily screen for planets that do not have a magnetic field (subject to the nature of artificially created magnetic fields that may result from some chemical interaction in the same vicinity) the point of fact remains that when looking for habitable planets, at the moment the ones we are most interested in will have to have a magnetic field of some reasonable strength if they are to be able to sustain life based on our present definitions.
While this doesnâ€™t solve the problem of how to get there â€“ it certainly creates opportunities whereby we can more closely determine those solar systems of interest wherein we may, within our lifetimes, choose to send a robotic probe for investigation notwithstanding a 100-150 year mission term.
— Kevin Feenan