Camera that takes images in seven colours developed in German observatory

London : A camera that can simultaneously take images in seven colours has been developed at the European Southern Observatory (ESO) in Garching, Germany.

The 2.2-m telescope called "GROND" will be mostly used to determine distances of gamma-ray bursts.
GROND stands for Gamma-Ray burst Optical/Near-Infrared Detector.

According to Jochen Greiner, who led the development of the GROND instrument, taking images in different filters simultaneously is important for the study of many astrophysical sources, and in particular of
variable sources, such as close binaries or active galactic nuclei.

But it is most crucial in the follow-up of gamma-ray bursts. Gamma-ray bursts (GRBs) are short flashes of energetic gamma-rays lasting from less than a second to several minutes. They release a tremendous
quantity of energy in this short time making them the most powerful events since the Big Bang.

Gamma-ray bursts, which are invisible to our eyes, are discovered by telescopes in space. After releasing their intense burst of high-energy radiation, they become detectable for a fleeting moment in the
optical and in the near-infrared.

This 'afterglow' fades very rapidly, making detailed analysis possible for only a few hours after the gamma-ray detection. This analysis is important in particular in order to determine the GRB's distance and, hence, intrinsic brightness.

A first determination of the distance can be done by taking images through different filters, using the so-called photometric redshift. Because a typical GRB afterglow becomes 15 times fainter after just 10 minutes, and over 200 times fainter after an hour, it is important to observe the object in as many filters as possible simultaneously.

"To make the determination of distance of far-away objects as accurate as possible, we decided to use four different filters in the optical and three different filters in the near-infrared," said Greiner.

GROND takes images of the same region of the sky in seven different filters. The field of view in the near-infrared is 10 times 10 arcminutes, or 1/7th the area of the Full Moon. It is smaller in the visible, slightly above 5 x 5 arcmin.

GROND is presently in its commissioning phase and its first science demonstration has been achieved, showing that all technical systems work properly.

In particular, GROND observed a quasar (an extremely bright and distant active nucleus of a young galaxy) located more than 12 billion light-years away.

The GROND can also be activated with a Rapid Response Mode (RRM): GRB alerts will be automatically fed into the system, thus minimising the delay between the gamma-ray burst detection by a satellite and its observation by GROND. (ANI)