Atop the Mauna Kea volcano in Hawaii, the WM Keck Observatory is home to two telescopes, Keck I and Keck II.
The scopes can either work separately or be combined into a single giant astronomical interferometer.
Keck I commenced scientific observations in March 1993, while Keck II came online in 1996; both scopes have 10m primary mirrors, each consisting of 36 hexagonal segments.
Each scope is eight storeys high and weighs 300 tonnes.
Dark energy, 1998
In 1998, astronomers using the Keck telescopes (among others) to study Type 1a supernovae were surprised when their measurements revealed that the Universe’s rate of expansion is accelerating.
They named the repulsive force responsible for this acceleration ‘dark energy’ – and in 2011, received the Nobel Prize in Physics for their efforts.
The Milky Way’s central black hole, 2002
Although it had long been suspected that the Milky Way must house a supermassive black hole at its centre, it wasn’t until 2002 that observers using the adaptive infrared optics of Keck II were able to peer through the Galactic murk and observe hundreds of young stars in very fast orbit around an unseen, incredibly massive object.
Planetary formation observed, 1998
Also in 1998, observers using Keck II published an image of an area of probable planetary formation in the region surrounding HR 4796, a young star lying just 220 lightyears from Earth in the constellation Centaurus.
This was the first direct evidence that planets formed, as had long been theorised, from proto-planetary discs of gas and dust.
Pluto’s killer, 2005
In 2005, Mike Brown and colleagues from Caltech turned to Keck II to confirm their discovery of Eris (see right), a body on the outer fringes of the Solar System that was bigger than Pluto.
This ultimately led to the downgrading of the former ninth planet to the new category of ‘dwarf planet’.
Measuring distances to large galaxies
Spectroscopic techniques pioneered at the WM Keck Observatory have enabled astronomers to calculate the distances to far-off galaxies accurately for the first time, and also to deduce their mass, radial velocity and chemical composition.
We could go on… other notable moments in Keck’s history have included imaging the collision between the remnants of Comet Shoemaker-Levy 9 and Jupiter in 1994, the discovery of ‘L’ and ‘T’ type dwarf stars and, in 2008, capturing the first direct images of an exoplanet.