5th August 2022 We’ve all be stunned by the images sent back by the James Webb Space Telescope (JWST) – but what’s happening on the ground?
First of all, let’s look at why astronomers go through such enormous effort to put telescopes into space. The complexities of designing a telescope to work in space, launching it into orbit and then running it remotely are overwhelming. Why not just build a bigger telescope here on Earth.
The vast amount of matter that makes up the Universe sends shouts out to us across the entire electromagnetic spectrum. Some of this we see as “light”. Other parts arrive as radio waves. Luckily for life here on Earth, a large part of what is broadcast towards Earth is blocked by our atmosphere. Some parts of the Infrared light received from space are not just blocked, but also emitted back towards us by various processes in the atmosphere itself.
There’s a swag of reasons for observing in the infrared and other parts of the spectrum we can’t see from Earth. For example, interstellar dust is transparent in the Infrared and space telescopes let us observe the centre of our galaxy or stars that are shrouded in dust.
Another reason for space telescopes was clearer seeing in orbit above our turbulent atmosphere. The Hubble Space Telescope used a mirror smaller than many telescopes on the ground but was able to see in amazing resolution compared to ground-based telescopes. Recent technological advances such as adaptive optics help cancel out the shimmers and shakes in our atmosphere allowing telescopes on the ground to play catch up with space telescopes when observing in visible light.
Because of this future space telescopes like NASA’s Nancy Grace Roman Space Telescope will extend the spectrum they observe in a similar way to the JWST. There’s no “Hubble 2.0” on the drawing board at this stage.
What is in the pipeline are the largest optical telescopes ever created!
When completed later this decade, the Giant Magellan Telescope or GMT will be the most powerful optical telescope ever built. It has seven 8.4 metre mirrors working as one. It works as the equivalent of single mirror some 24 metres across. (The current largest optical telescope is approx 10 metres.) The resolution of images of the GMT is likely to be 10 times that of the Hubble Space Telescope.
Initial areas of study this massive new telescope include exploring the ancient past of the universe, probing the Big Bang and the formation of the first stars, galaxies, and black holes. Every time astronomers build “the largest telescope ever”, what they find are things that were totally unexpected and this likely to be the case with the GMT, especially when exploring exoplanets and the possibility of life outside the Solar System. The GMT is currently under construction in Chile and the consortium of partners running the project include the Australian National University.
Also under construction in Chile is the ESO Extremely Large Telescope or ELT . (Maybe we shouldn’t let astronomers name telescopes. We almost had OWL – Overwhelmingly Large Telescope!)
The ELT has a multisegmented mirror made up of nearly 800 segmented mirrors combining to function as a single mirror just under 40 metres across. The telescope will work in the visual and due it’s high location, the near infrared.
Similar to the GMT, the ELT will chase down some of the big current mysteries in astronomy such as the search for habitable Earth-like planets orbiting stars, studying dark matter and dark energy, and probing the earliest possible history – the so called “Dark Ages” not long after the Big Bang and before light flooded the skies from Universe from stars formed from the hydrogen gas that bound together under gravity. You can read more about the ELT Science Program here.
The Vera C. Rubin Observatory in Chile is named after pioneering astronomer Vera Rubin, who studied the rotation of galaxies and helped provide evidence for Dark Matter.
“First light” at the Rubin Observatory is expected in February 2024 with full science beginning about 6 months later.
The main telescope at the Rubin Observatory, the Simonyi Survey Telescope, has a main mirror “only” 8.4m metres in diameter. This puts it among the largest telescopes currently in operation but there’s a few of those, so what makes it so special?
Part of the answers lies with the 32,000 megapixel camera attached to the telescope which is the largest ever made. Combined with vast data storage and transfer capabilities, the main task of the telescope is to survey the night sky at a speed and regularity never achieved before.
Previous entire sky surveys with large telescopes have mapped and revealed objects that were later observed in more details. But such surveys, such as the Palomar Observatory Sky Survey, took years to complete. The Rubin Observatory plans to revisit every part of the sky every few nights with the largest telescope dedicated to full time survey observations, producing over 200,000 images per year.
Our night sky is mostly static and operates on a slow, predictable rhythm. However, those things that change or break the pattern of the Universe are of enormous interest to astronomers. Apart from general survey work, the Rubin Observatory will be able to spot any changing or “transient” events such as supernovae, gamma ray bursts that happen over a short timeframe.
It’s likely to spot small, undiscovered objects in the Solar System and possibly increase the number we know about by up to factor of 100 times, simply by spotting faint objects as they move across a background of fixed stars. A search for the elusive “Planet Nine” will be part of the research as well as keeping an eye out for visitors to the Solar System from interstellar space. In recent years, three deep-space objects lobbing into the Solar System were discovered by chance. One even seems to have hit the Earth! With a systematic survey, we might find out we have more visitors to the Solar System than we expected.
The Square Kilometre Array or SKA is a vast radio telescope spread across South Africa and the Western Australia outback. When operational in 2027, it will produce the highest resolution images in all of astronomy.
SKA will have up to a million antennas and thousands of steerable dishes to capture the Universe across an area around one million square metres in size. Part of the science mission of SKA will testing Einstein’s theory of relativity, studying early galaxy and star formation and surveying the Universe on the radio wavelengths the Earth’s atmosphere is transparent to.
Visual and infrared astronomy rely on physical processes that produce observable light. Radio astronomers are lucky to be able to observe the most abundant element in the Universe, hydrogen as it naturally emits electromagnetic radiation. Each atom of the gas undergoes a “spin-flip transition” due to a change in its energy state and this produces radio waves of around 21cm in wavelength. This only occurs every 10 million years or so for an individual molecule but seeing there’s a lot of molecules of hydrogen in even extremely sparse gas clouds, there’s still a lot of spin flips going on! This 21cm wavelength is also transparent to dust clouds – making it perfect for mapping the Universe in extreme detail.
(I left out another mega telescope on the drawing board, The Thirty Metre Telescope or TMT mainly as there’s ongoing issues with its proposed site.)
If you’d like to chat about the latest telescope technology, jump into the BINTEL Society Facebook group.
Cheers
Earl White
BINTEL