When you go somewhere with relatively dark skies, you can pull up your smartphone and that handy planetarium app, look for the star Fomalhaut in the constellation of Pisces, and then point it to your friend and say: You see, there is a planet orbiting that star, and we have literally seen it with our telescopes! — But there is a catch: The little blob of light which was directly observed by Hubble is weird, and it doesn’t really look like a planet. In fact, some astronomers have proposed it could be a neutron star. Gasp!
(Image: ESO/J.-L. Beuzit et al./SPHERE Consortium)
This Eye of Sauron is the magnificent ringed star HR 4796A, in the southern constellation of Centaurus. It is one of the first images produced by SPHERE, the Spectro-Polarimetric High-contrast Exoplanet Research instrument, installed last month on the ESO’s Very Large Telescope atop Cerro Paranal in Chile.
To a typical optical telescope, HR 4796A’s dark centre is a blazing disk of starlight that swamps the weaker glow of the dust ring. SPHERE filters out the star’s light to acquire exceptionally sharp images like this. The instrument also corrects for the effects of Earth’s atmosphere and can differentiate between starlight and a planet’s glow, on the basis of the colour and polarisation of light. These talents will allow SPHERE to discover planets orbiting distant stars and study them with spectacular clarity.
