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SYFY WIRE Bad Astronomy

SPHERE Takes a Look at a Forming Planetary System

By Phil Plait

I love when fancy new astronomy technology gets implemented. I like it more when it has a fancy name, too, like the Spectro-Polarimetric High-contrast Exoplanet REsearch instrument, or SPHERE.

This is a camera that has recently been mounted on the Very Large Telescope, which has a silly name, but a descriptive one. VLT is an array of four 8.2 meter telescopes in Chile that are capable of phenomenal astronomical observations. They have extraordinary resolution (the ability to see small details) as well as huge mirrors which allow faint objects to be detected.

SPHERE will be used to look at exoplanets, worlds orbiting other stars. Only a handful of exoplanets have been directly imaged (most are found indirectly, through their effects on their stars), but SPHERE may well change that.

It employs an arsenal of advanced techniques to look for alien planets. It has a coronagraph, a small disk that blocks the light from a star. Planets are very faint compared to their host stars, so blocking that light will make it easier to see the fainter world. It uses adaptive optics to counteract blurring from Earth’s turbulent atmosphere, literally deforming the shape of the telescopes’ mirrors to account for the lens-like effects of the air above them. It also examines polarized light, light where the waves have been aligned through various processes. Light reflected off an exoplanet can be polarized, enhancing it versus light from the star.

These techniques work very well for stars that are just now forming planets too. One such star is HR 4796A, part of a binary system about 270 light years from Earth. HR 4796A has a ring of dust around it, material leftover from the formation of planets. The ring is likely being sculpted by an unseen planet’s gravity, confined to an annulus in a similar way that shepherd moons herd particles in Saturn’s rings.

That’s what you’re seeing at the top of this article. The ring has been observed many times before—I was involved with a project a while back that took a peek using Hubble—but this is one of the finest observations of it I’ve seen. And this was just a test of SPHERE’s abilities!

I’m fascinated by exoplanets, and dazzled by the new techniques and technology coming out to aid in the hunt. Every day brings more discoveries, and every year better ways of making them. SPHERE is a big advance, and I wonder where we’ll be in this field in just a few more years.

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