We have detected for the first time the scattered light from a planet orbiting a distant star. Similar to how your polaroid sunglasses filter away reflected sunlight to reduce glare, we have used tricks with polarized light in our case to enhance the faint reflected starlight "glare" from an extrasolar planet. This allowed us to trace directly the orbit of the planet and infer the size of its swollen atmosphere, in contrast to other exoplanets detected by various indirect methods.  
The exoplanet circles a red dwarf star, called HD189733, in the constellation Vulpecula which lies about 60 light years from the Earth. The planet, known as HD189733b, was discovered two years ago via Doppler spectroscopy and photometric transits. It is so close to its parent star that its atmosphere expands from the heat. Astronomers have, until now, never seen light reflected from an exoplanet although they deduce from other observations that this one probably resembles a "hot Jupiter". Unlike Jupiter, it orbits its star in a couple of days rather than the 12 years it takes Jupiter to make one orbit of the Sun.
The team, consisting of Svetlana Berdyugina (ETH Zurich & Tuorla Observatory), Andrei Berdyugin and Vilppu Piirola (Tuorla Observatory) and Dominique Fluri (ETH Zurich), used the remotely controlled 60cm KVA telescope on La Palma, Spain, to obtain polarimetry measurements of the star and its planet. These measurements demonstrate that the scattering atmosphere most probably consists of particles smaller than half a micron, such as atoms, molecules, perhaps water vapor which was recently suggested for this planet, or even tiny dust grains. Such particles effectively scatter the light in the blue - in exactly the same way as in the Earth's atmosphere. We are also able for the first time to recover the shape and orientation of the planet's orbit as seen on the sky plane, i.e. obtain an "image" of the orbit  (see figure on the right). Thus our findings open new vast opportunities for exploring physical conditions on exoplanets as well as for determining radii and true masses,  and hence densities, of non-transiting planets.

Reference: Berdyugina S.V., Berdyugin A.V., Fluri D.M., & Piirola V.: First detection of polarized scattered light from an exoplanetary atmosphere, 2008, Astrophys. J. Lett., 673, L83-L86 PDF (0.36 Mb)  

Figure: The orbit of HD189733b as projected on the sky. Solid and dashed lines indicate parts of the orbit in front of and behind the sky plane, respectively. The orange circle in the center depicts the star and the blue circle on the orbit the planet. The reconstructions are made for the orbit inclination i = 94° and the longitude of the ascending node W=16° (top) and 196° (bottom).  Positive directions of Stokes q and u and orientations on the sky are also shown.
See an animation of the planet orbiting the star and corresponding variations of polarization.

Molecules diagnose dying stars

The methine molecule (CH) has been employed as a sensitive "compass needle" in the atmosphere of a dying star to determine the strength and direction of its magnetic field. Using this new technique we find with great accuracy an enormous field strength, nearly 15 million times stronger than the natural field of the Earth (see plot). Eventually, our Sun will also turn into one of such stars called white dwarfs. These stellar remnants tell us a fascinating story on how the galaxy may have looked like a few billion years ago when the Sun and the Earth were born.

Reference: Berdyugina S.V., Berdyugin A.V., Piirola V.: Molecular dichroism in spectra of white dwarfs, 2007, Phys. Rev. Lett., 99, 091101 PDF (3.8 Mb)

During the solar 11-yr cycle, the latitude of sunspot occurrence varies with a pattern resembling a butterfly, which was first discovered by Edward Maunder in 1904 (top plot). At the beginning of a new solar cycle, sunspots tend to form at high latitudes, but near the minimum of the cycle, sunspots appear close to the equator. We analyzed long-term brightness variations on one of the very active star and, for the first time, recovered a stellar butterfly diagram (bottom plot). Cool spots on this star preferably occur at opposite longitudes. In contrast to the Sun, while on one side of the star spots occur at higher latitudes, on the opposite side they appear at lower latitudes. This may indicate a precession of the global stellar magnetic field.

Reference: Berdyugina S.V. & Henry G.W.: Butterfly diagram and activity cycles in HR 1099, 2007, Astrophys. J. Lett., 659, L157-L160, PDF (1.0 Mb)