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The Hubble Space Telescope celebrates 25 years of cosmic wows

 

NASA launched the $1.5 billion Hubble Space Telescope (HST) on April 24, 1990 and for 25 years it’s been staring deep into the depths of the universe, taking astonishing photos of nebulae and galaxies.

Fired into orbit on the back of the Space Shuttle Discovery, Hubble is the size (13.3 metres long) and weight (11 tons) of a single-decker bus. Equipped with a mirror that’s 2.4 metres in diameter, the telescope has helped astronomers estimate the age of the universe, discover Dark Matter, and find evidence of planets orbiting distant stars.

What Hubble sees from its orbital vantage point 570 kilometres above the Earth, generates over 10TB of new scientific data every year.

The Sombrero galaxy
The Sombrero galaxy, aka Messier 104 (M104) – a brilliant white core encircled by a thick dust spiral. Image: NASA.

Packed with the best that 1980’s technology had to offer, Hubble has suffered its fair share of problems. There have been five servicing missions to date, the first in 1993 to install corrective optics to fix the HST’s flawed mirror, the last in 2009 to upgrade key systems and replace its six nickel-hydrogen (NiH) batteries.

With all of its various upgrades over the years, Hubble is projected to stay in use until at least 2020 and it could keep operating for longer. But with the retirement of NASA’s Space Shuttle fleet, there’s no way to improve it further. This is why, in 2018, Hubble will be joined in space by the new and far more powerful James Webb Space Telescope (JWST).

Pillars of Creation
In 1995, Hubble photographed these stunning columns of cold gas in the Eagle Nebula (M16). They’re known as the Pillars of Creation. Image: NASA.

The biggest improvement over Hubble is that JWST will be equipped with a Near-Infrared Camera capable of detecting light from stars and galaxies in the process of formation, as well as very faint objects around a central bright object, like solar systems. A Near-Infrared Spectrograph, meanwhile, will enable astronomers to calculate the temperature, mass and the chemical composition of various stellar objects.

A Mid-Infrared Instrument will cover the wider Infrared range and a Fine Guidance Sensor/Near InfraRed Imager and Slitless Spectrograph will take care of pointing the JWST in the right direction and hunting for exoplanets respectively.

Crucially, the primary mirror on the JWST is 6.5 metres in diameter, almost three times larger than Hubble’s. It’s been constructed from 18 hexagonal panes of polished beryllium, which fit together in a honeycomb structure. This segmented approach will enable the mirror to be folded to fit inside the Ariane 5 launch vehicle and to unfold when the telescope reaches its destination – the Earth-Sun L2 Lagrange point, 1.5 million kilometres from Earth.

A scale model of the JWST mirror
This 1/6th scale model of the JWST mirror shows how the polished beryllium panes will fit together. Image: NASA.

The James Webb Space Telescope (named after a NASA administrator) will continue what Hubble started 25 years ago, deepening our understanding of the universe and our place in it.

“JWST will be the premier observatory of the next decade,” says NASA, “serving thousands of astronomers worldwide. It will study every phase in the history of our Universe, ranging from the first luminous glows after the Big Bang, to the formation of solar systems capable of supporting life on planets like Earth, to the evolution of our own Solar System.” – Dean Evans

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