Astronomers around the world are designing and building very large optical telescopes to meet the needs of their future research projects.
These telescopes are very expensive to design, build and operate and consequently each instrument involves funding from international partners. An individual country cannot justify the full expenditure alone, in the order of $1 billion to $1.5 billion.
Three telescopes are expected to commence operation, called "first light" by astronomers, by 2028.
The Australian Government's science budget is contributing funds for a share of access to one of these telescopes.
This access will allow Australian astronomers time on the Giant Magellan Telescope (GMT). The international partners involved with this telescope include the US, Brazil, South Korea and Australia, contributing an estimated final construction cost of US$1.05 billion with an expected completion date of 2024.
The reason astronomers require very large telescopes is that distant astronomical objects are so far away from Earth (millions to billions of light years distant) that their light is exceedingly faint.
To form an image of these extremely distant objects, a large telescope is needed to focus the tiny amount of light onto a highly sensitive detector. The more light collected at the telescope's detector, the more detailed information can be gained about the object.
Astronomers like to observe really distant objects as they are looking back in time, even close to the beginning of the known Universe. The light from these objects left the stars within these distant galaxies billions of years ago. It has taken the light all this time to reach Earth.
Astronomers like to observe really distant objects as they are looking back in time, even close to the beginning of the known Universe.
The GMT will have seven 8.4 metre primary mirrors, forming the equivalent of a single mirror 24.5 metres in diameter, called the aperture of the telescope. Compare this to Australia's largest telescope, the Anglo-Australian Telescope (AAT) at Siding Spring Observatory which has a single primary mirror 3.9 metres in diameter.
The GMT will have a light collecting area 40 times that of the AAT. Forty times more light energy will fall on the detector of the GMT compared to that of the AAT. Far fainter objects can be resolved by the GMT.
The construction of these massive telescopes, which in the case of the GMT has a moving weight of some 1,500 tonnes, requires advanced mechanical, electronic and optical engineering and science.
The GMT's seven 8.4 metre mirror sections must be aligned to a very high degree of accuracy to enable all of the mirrors to operate as a 24.5 metre mirror. To obtain a clear image and overcome the "twinkle effect" of the atmosphere, engineers use laser technology and highly sensitive servo motors to continuously and quickly adjust the alignment of the primary mirror sections.
This rapid mirror adjustment is called adaptive optics, and provides images close to those given by telescopes in space, such as the Hubble Space Telescope. Land based telescopes can now overcome most of the limitations of observing through the Earth's atmosphere.
Further, land-based telescopes, which are much bigger than those in space, can be modified and serviced with comparative ease and are likely to remain in active service for a greater period.
The location of these large telescopes is very important. The GMT is being built at high altitude in the very dry Atacama Desert of northern Chile, at Cerro Las Campanas, 2,520 metres above sea level.
This location provides very clear, dry skies free of haze and cloud producing water vapour, no light pollution as nobody lives in such an inhospitable place and an atmosphere that has very little "twinkle" as the prevailing air flow is laminar coming from the west off the Pacific Ocean. The ocean is relatively flat compared to the land surface and does not impose significant hot air turbulence in the air at higher altitudes, resulting in a reduced "twinkle effect".
Astronomers push the boundaries of technology in the pursuit of a better knowledge of the Universe. Such a pursuit requires ever continuing improvements in optics, electronic detectors and computers.
In the recent past, such astronomical-demanded improvements have given the world community high quality digital cameras and WI-FI communication, both used in our smart phones as well as numerous other devices. Australian CSIRO astrophysicist Dr John O'Sullivan and others invented WI-FI. Investment in astronomy does yield very real and valuable practical returns apart from a greater understanding of the marvellous Universe that we live in.
It has been said, "the sky above is a significant part of our environment to admire and understand".