 |
Optical vortex could look directly at extrasolar planets
December 01, 2005A new optical device might allow astronomers to view extrasolar planets directly without the annoying glare of the parent star. It would do this by "nulling" out the light of the parent star by exploiting its wave nature, leaving the reflected light from the nearby planet to be observed in space-based detectors. The device, called an optical vortex coronagraph, is described in the December 15, 2005 issue of Optics Letters.
About ten years ago the presence of planets around stars other than our sun was first deduced by the very tiny wobble in the star's spectrum of light imposed by the mutual tug between the star and its satellite. Since then more than 100 extrasolar planets have been detected in this way. Also, in a few cases the slight diminution in the star's radiation caused by the transit of the planet across in front of the star has been observed.
Many astronomers would, however, like to view the planet directly-a difficult thing to do. Seeing the planet next to its bright star has been compared to trying to discern, from a hundred meters away, the light of a match held up next to the glare of an automobile's headlight. The approach taken by Grover Swartzlander and his colleagues at the University of Arizona is to eliminate the star's light by sending it through a special helical-shaped mask, a sort of lens whose geometry resembles that of a spiral staircase turned on its side.
The process works in the following way: light passing through the thicker and central part of the mask is slowed down. Because of the graduated shape of the glass, an "optical vortex" is created: the light coming along the axis of the mask is, in effect, spun out of the image. It is nulled, as if an opaque mask had been place across the image of the star, but leaving the light from the nearby planet unaffected.
The idea of an optical vortex has been around for many years, but it has never been applied to astronomy before. In lab trials of the optical vortex mask, light from mock stars has been reduced by factors of 100 to 1000, while light from a nearby "planet" was unaffected (see test figures at http://www.aip.org/png/2005/241.htm). Attaching their device to a telescope on Mt. Lemon outside Tucson, Arizona, the researchers took pictures of Saturn and its nearby rings to demonstrate the ease of integrating the mask into a telescopic imaging system.
This is, according to Swartzlander (grovers@optics.arizona.edu, 520-626-3723), a more practical technique than merely attempting to cover over the star's image, as is done in coronagraphs, devices for observing our sun's corona by masking out the disk of the sun. It could fully come into its own on a project like the Terrestrial Planet Finder, or TPF, a proposed orbiting telescope to be developed over the coming decade and designed to image exoplanets.
American Institute of Physics
Related Extrasolar Planets Current Events and Extrasolar Planets News Articles
Weather on the Outer Planets Only Goes So Deep
What is the long-range weather forecast for the giant planets Uranus and Neptune? These planets are home to extreme winds blowing at speeds of over 1000 km/hour, hurricane-like storms as large around as Earth, immense weather systems that last for years and fast-flowing jet streams.
Researchers develop model for identifying habitable zones around star
Researchers searching the galaxy for planets that could pass the litmus test of sustaining water-based life must find whether those planets fall in a habitable zone, where they could be capable of having liquid water and sustaining life.
Astrophysicists identify a 'super-Jupiter' around a massive star
Astrophysicists at the University of Toronto and other institutions across the United States, Europe and Asia have discovered a 'super-Jupiter' around the massive star Kappa Andromedae.
Birth of a planet
The Earth and the planets of our solar system are not alone in the universe. Over the past few decades, the hunt for extrasolar planets has yielded incredible discoveries, and now planetary researchers have a new tool-simulated models of how planets are born.
Venus to appear in once-in-a-lifetime event
On 5 and 6 June this year, millions of people around the world will be able to see Venus pass across the face of the Sun in what will be a once-in-a-lifetime experience.
New model provides different take on planetary accretion
The prevailing model for planetary accretion, also called fractal assembly, and dating back as far as the 18th century, assumes that the Solar System's planets grew as small grains colliding chaotically, coalescing into bigger ones, colliding yet more until they formed planetesimals.
Planets Circling Around Twin Suns
In the last two decades, the study of extrasolar planets - those that lie outside our own solar system - has become one of the most important fields of astrophysics.
Planets around stars are the rule rather than the exception
There are more exoplanets further away from their parent stars than originally thought, according to new astrophysics research.
The Habitable Exoplanets Catalog, a new online database of habitable worlds
Scientists are now starting to identify potential habitable exoplanets after nearly twenty years of the detection of the first planets around other stars.
Astronomers Find Elusive Planets in Decade-Old Hubble Data
In a painstaking re-analysis of Hubble Space Telescope images from 1998, astronomers have found visual evidence for two extrasolar planets that went undetected back then.
More Extrasolar Planets Current Events and Extrasolar Planets News Articles
| © 2013 BrightSurf.com |