Look into the turbulent heart of a Scorpion and you’ll find so much more than mere radiance.
Exploring a star
HAVE YOU EVER looked at stars through a telescope? Chances are you have, because it’s the most obvious thing to do with a telescope at night after you’ve taken in the Moon and planets.What you saw might, however, have disappointed.
Certainly, stars appear brighter through a telescope and, when grouped in a cluster, can be radiantly beautiful. You might even be able to detect differing colours among them.
But what you won’t see is any detail in the stars themselves. And that goes not just for backyard viewing, but for most of the world’s big telescopes.The fact is that, with the exception of the Sun, stars are simply too far away to be seen as anything other than points of light.They are ‘unresolved’, as we say in the trade.
What would be required to amplify star images into detailed discs of light is a bigger telescope.Today’s largest optical telescopes have dished mirrors of about 10m in diameter, but you would need one perhaps 20 times bigger to see features on the surface of a star. Such telescopes do not exist, yet. But there is a technique known as interferometry that allows the wave properties of starlight to be used to mimic the effect of a single big mirror by combining the light from several smaller ones.
At the European Southern Observatory’s Very Large Telescope in northern Chile, there is a facility known as VLTI (the I is for interferometer) that works in exactly this way.
VLTI has recently been used to make the first detailed image of a star other than the Sun.The target object was the red supergiant star Antares, familiar to southern stargazers as the heart of the Scorpion. Antares is known to be losing mass and, by making careful measurements of its rainbow spectrum,VLTI researchers have also been able to chart the turbulent motion of gas in Antares’ extended atmosphere.
This extraordinary achievement paves the way for a completely new branch of astronomy that will explore the surfaces of stars.
This artist’s impression of the star Antares is based on images of unprecedented detail, constructed by astronomers using the Very Large Telescope Interferometer facility.