'Sphere' looks past stellar glare to find exoplanets

A device known as "Sphere," attached to the Very Large Telescope in Chile, has achieved first light using three novel methods to peek into the brightness.

One of the first images from Sphere -- an infrared image of the dust ring around a star in the constellation Centaurus. ESO/J.-L. Beuzit et al./Sphere Consortium

For casual nighttime sky watchers, stars provide a glittering canopy that can capture attention for hours, what with all their twinkling, color changing and tendency to arrange themselves into the giant pictures we call constellations.

For serious astronomers looking out to the heavens to find other planets, though, stars can present a very tricky problem -- they're just too darn bright. Their fierce light makes it difficult to see other cosmic bodies that might be revolving around them.

Now a brand-new device has been attached to the European Southern Observatory's (ESO) Very Large Telescope (VLT) at the Paranal Observatory in Chile that will help astronomers see past the light from other suns to get a look at what's going on around them.

Called "Sphere," for spectro-polarimetric high-contrast exoplanet research, the device was installed in May and has now achieved what's known in the telescope world as "first light," meaning that it successfully imaged several heavenly bodies. This includes the dust ring around a nearby star known as HR 4796A (see above). Such detail would normally have been obliterated by the glare of the star itself.

To achieve its unique imaging tricks, Sphere employs three mechanisms.

"The first of three novel techniques exploited by Sphere is extreme adaptive optics to correct for the effects of the Earth's atmosphere so that images are sharper and the contrast of the exoplanet increased," said the ESO in a statement. "Secondly, a coronagraph is used to block out the light from the star and increase the contrast still further. Finally, a technique called differential imaging is applied that exploits differences between planetary and stellar light in terms of its color or polarization -- and these subtle differences can also be exploited to reveal a currently invisible exoplanet."

Sphere on its way from base camp at ESO's Paranal Observatory to the telescopes on the summit. ESO/J.-L. Lizon

While Sphere has thus far revealed the dust ring around HR 4796A and sent back an image of Saturn's moon Titan, its real work will be combing the galaxy to find exoplanets that may have been previously hidden by star glare. The creators of the instrument, an effort involving over 10 space organizations around Europe, say that Sphere will "revolutionize the detailed study of exoplanets and circumstellar discs."

"This is just the beginning," added Jean-Luc Beuzit, of the Institut de Planétologie et d'Astrophysique de Grenoble, France, and principal investigator of Sphere, in a statement. "Sphere is a uniquely powerful tool and will doubtless reveal many exciting surprises in the years to come."

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