THE clearest views so far of dusty discs surrounding both newborn and ageing stars have been captured by an observatory in Chile. The striking results raise hopes that the same instrument might soon catch our first glimpse of giant planets orbiting close to sun-like stars.
The observations were made using the Very Large Telescope Interferometer (VLTI), a telescope array run by the European Southern Observatory atop the 2635-metre mountain Paranal in Chile鈥檚 Atacama desert. A new instrument called AMBER combines infrared light from either two or three 8.2-metre telescopes, making an instrument that effectively has the resolution of a telescope up to 90 metres in diameter (see Diagram). By analysing the interference fringes created by combining the light, astronomers can study details that occupy just 0.5 millionths of a degree in the night sky.
Fabien Malbet of the Astrophysical Laboratory of Grenoble in France and his team combined light from two telescopes to study a fledgling star called MWC 297 about 800 light years away. Some previous observations had suggested that such young stars are often surrounded by discs of dust, while others had found powerful flows of gas around them. Now AMBER鈥檚 ability to monitor different wavelengths at the same time has allowed Malbet鈥檚 team to measure the complex interplay of the disc and the wind together.
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鈥淎MBER allowed the team to measure the complex interplay of the dust disc and wind around the star together鈥�
The observations showed that the disc around MWC 297 extends from a distance roughly equivalent to the orbit of Mercury out to the orbit of Pluto. Blasts of wind were whipping out of the star鈥檚 polar regions at about 600 kilometres per second, while near the disc the winds dropped to about 70 kilometres per second.
Another team, led by Armando Domiciano de Souza of the Max Planck Institute for Radio Astronomy in Bonn, Germany, used AMBER to combine light from three telescopes and take the closest ever look at the shroud of dust around a bright supergiant about 8000 light years away. 鈥淭his star is close to the end of its life,鈥� says Domiciano de Souza. The measurements revealed that the shroud is a flattened sphere about half as wide as our solar system along its longest axis.
Both sets of results will be published in the journal Astronomy & Astrophysics. Malbet says they suggest that AMBER will soon allow astronomers to measure temperatures and 鈥渃lumpiness鈥� in protoplanetary discs around young stars, the possible sites of future planets. It could also allow them to see 鈥渉ot Jupiters鈥�, gas giants that orbit much closer to their parent stars than Jupiter does to the sun. They could do this by homing in on key wavelengths at which the planets outshine their stellar hosts.
