Astronomers have a new way to see planets around other stars, one that could provide information seldom available through existing methods. It may even allow us to observe Earth-like planets in the habitable zone around their stars.
Telescopes are now so powerful, many could show us planets light-years away, were they not lost in the glare of the stars they orbit. After all, it's hard to see a firefly next to a searchlight. Astronomers call this the candle and lighthouse problem, but one team think they have a solution.
The technique involves a charge injection device (CID). Sadly, it is only expected to work on space telescopes, but even that could be enough to provide a treasure trove of information about planets in our patch of the galaxy.
CIDs have existed for more than 40 years, but they have been outshone by a relative: charge-coupled devices (CCD) are the industry standard. Both use incoming photons to trigger the release of electric charges that determine the brightness of pixels, but CIDs can provide a clearer image where one part of the field of view is very bright. They do this by restricting the charge associated with the signal to an image site, rather than collecting the charge and transferring it sequentially to an amplifier.
In Publications of the Astronomical Society of the Pacific, Dr. Daniel Batheldor of the Florida Institute of Technology reported on his results when he attached a CID to the 0.8-meter (32-inch) Ortega telescope and turned it on Sirius, the brightest star in the sky besides the Sun.
(A) Sirius with coordinates in green and known background objects as red dots. (B) Faint objects detected near Sirius using the CID. Florida Institute of Technology
The CID's pixels collecting the light from the brighter object saturated quickly, but the pixels dedicated to the area nearby kept on gathering light until there was enough to show objects 70 million times fainter than Sirius itself. These were probably background stars, but the authors argue that “The atmospheric conditions present during the collection of this data prevented less modest results.”
If similar work was done in space, with no atmosphere to smear the dog star's light, we should be able to see planets faintly reflecting the light of their parental star.
“The CID is able to look at a very bright source next to a very faint source and not experience much of the image degradation you would normally experience with a typical camera," Batcheldor said in a statement.
Direct imaging of planets has been done before, but only where the worlds we seek are gas giants still young enough to be very hot from gravitational condensation. Batcheldor's work raises hopes of imaging planets whose light comes from reflecting their star.
And planets are not the only thing CIDs in space might let us see. The authors note that we know little about the formation of galaxies that surround quasars because the extraordinary brightness of material falling into a black hole blinds us to everything nearby.