HD189733 (Vulpecula) - A red dwarf star known as HD189733, about 60 light years from Earth in the constellation Vulpecula, is home to an orbiting planet which now bears the unique trait of being the first extra-solar planet ever to be observed in the visual spectrum from Earth. Using a special kind of polarization filtering, the researchers were able to mask out all other-sourced light and focus only on light reaching us reflected directly from the planet, called HD189733b.
The planet itself was only discovered two years ago using Doppler spectroscopy and photometric transits. It's very close to its parent star and has expanded from the intense heat. They say this planet would resemble a very hot Jupiter, though it orbits its sun every two days, versus the 12 years Jupiter takes.
Planet's atmosphere is like a big, gaseous Jupiter
The research team consisted of Svetlana Berdyugina from the ETH Zurich & Tuorla Observatories, Andrei Berdyugin and Vilppu Piirola from the Tuorla Observatory and Dominique Fluri with ETH Zurich. They used a 60cm KVA telescope in La Palma Spain to obtain the polarimetry measurements of the star and planet, indicating that the scattering atmosphere of the planet most likely consists of sub-micron particles, such as atoms, molecules, tiny dust particles, and possibly even water vapor.
The researchers have been able to determine the shape and orientation of the planet's orbit, which is tilted about 75 degrees off horizontal. Their work serves as a model basis for determining future extra-solar planetary radii, true masses, which then also reveal densities. So far, more than 200 extrasolar planets have been detected.
Bright sky unseen
Our entire Milky Way galaxy is a very powerful visible light source. However, it is so packed with tiny particles of interstellar dust that the vast majority of its brilliant illumination doese not reach the Earth, which is very close to our galaxy's outer edge. As such, "seeing" visible light from distant stars becomes an extremely difficult task because so few photons in the visible spectrum are able to make it past the dust particles between our telescopes and the source. In addition, planets are reflected bodies typically 100s of thousands to millions of times dimmer than their source star, making them even more difficult to see when the light from the star is present.
This particular planet has become the first one we've seen due to its relative proximity to Earth, its enormous size, and its close, tight orbit to its star, providing a very bright planetary source with reflected and refracted light with a different polarity that could be filtered out.
Read more ... ETH Zurich research highlights.