Astronomers have achieved first light with a powerful instrument that will allow scientists to probe the environments surrounding black holes. The GRAVITY instrument is in the process of being installed in the tunnels below the ESO's Very Large Telescope (VLT) located at the Paranal Observatory, Chile.

The newest addition to the VLT uses a technique known as interferometry to harness the power of the observatory, combining the collected light from numerous instruments to form a single virtual telescope roughly 200 m (656 ft) across.

GRAVITY's first light test focused on a series of bright young stars known as the Trapezium Cluster located in the heart of the well known Orion Nebula. Not only was the instrument able to successfully combine light harvested from the VLT's four 1.8 m (5.9 ft) auxiliary telescopes into a single unified image, it also made a discovery in the region of a previously unknown component in the cluster – a double star known as Theta Orionis F.

The first light test for GRAVITY represented the first time that four telescopes had been stabilized simultaneously, allowing the instrument to take exposures hundreds of times longer than previous attempts, with the most prolonged exposure lasting several minutes in length.

Image of the GRAVITY instrument located at the Paranal Observatory, Chile(Credit: ESO/GRAVITY consortium)

Successful completion of the first light tests represents a major milestone on the journey to the commissioning of the instrument. Once fully operational, the GRAVITY instrument will allow astronomers to examine very faint objects that would ordinarily be extremely difficult to observe with conventional methods.

GRAVITY will in effect serve as a sort of swiss army instrument for the VLT, capable of fulfilling a wide range of applications. A primary task to be undertaken by GRAVITY in the early stages of its operational life will be to probe the environment prevailing around the event horizon of a black hole.

Our understanding of these regions is governed by Einstein's Theory of General Relativity, meaning that GRAVITY will be putting one of the scientific worlds most venerable doctrines to the test.

That is the long term goal, but in the near future the team will continue its work in integrating GRAVITY with the VLT's four 8.2 m (26.9 ft) telescopes, readying the instrument for another test that is set to take place later this year.

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