Three million euro for astronomy

University of Groningen astronomers were awarded a EUR 1 million grant from research funding agency NWO, to develop and build a new instrument for the William Herschel telescope on La Palma. Earlier, they were awarded another EUR 2 million for the personnel costs this project involves.

‘We are going to build a spectrometer which is much more sensitive and works much faster than currently available instruments’, Scott Trager explains. As ‘Project Scientist’, he is responsible for the Dutch contribution to the project which also includes colleagues from Britain, France and Spain.

‘This new piece of equipment, called WEAVE , will allow us to inspect in one go a piece of the sky the size of sixteen full moons, observing up to one thousand objects in one go.’ The spectrometer will be able to measure both the composition of a star and its redshift (a measure of its distance).This will be done in a new, very sensitive way: a combination of one thousand individual glass fibers leading the light to the spectrometer using a technique called Volume Phase Holographic (VPH) Gratings .

So how does that work? To put it (very) simply: the light of the telescope is caught on a plate, on which two robots have positioned up to one thousand glass fibers, at locations which contain interesting astronomical objects. The fibers are positioned using an existing stellar catalogue. The light inside the glass fibers reflects off the VPH Grating, creating an interference pattern, which splits the light into its different colors. The spectrometer collects this light to analyze these different colors.

The EUR 3 million total grant money pays for the Dutch component of this European project. Trager: ‘We build the spectrometer, the British are responsible for the robots, the French will make the fiber system and the Spaniards provide the (existing) telescope and systems for data reduction.’ WEAVE will perform measurements that will in part complement the work of other instruments. ‘The Dutch radio telescope LOFAR, for example, can perform amazing measurements, but it cannot determine the distance to the objects it studies.’ WEAVE can. And WEAVE will also provide complementary measurements for the Westerbork radio telescope and the new European Gaia satellite which is scheduled for launch later this year.

‘Ultimately, WEAVE will work about ten times faster than similar instruments, with double the sensitivity’, says Trager. Around a dozen staff members of the Kapteyn Institute for Astronomy at the University of Groningen and the NOVA Optical-Infrared Research Group, based at Astron in Dwingeloo, will work on the project.