Fast-tracking the sky with the TAIPAN instrument

Over the years, the technology that drives astronomical discovery has rapidly accelerated as computers have become more powerful, engineering has become more efficient, and machines have started to do a lot of the heavy lifting in data processing. 

Soon, a new instrument that has been developed in Australia by scientists at Macquarie University, will revolutionise how researchers from all around the world gather the ‘rainbow fingerprints’ (spectra) from hundreds to thousands of stars per night - facilitating a more powerful set of data to analyse and understand the objects in our galaxy and beyond. 

It’s not your regular looking type of telescope hardware - it’s made up of lots of little robots, standing only a few centimetres high, which move around a glass plate to chase starlight coming through the telescope’s optical systems. 

Currently, the 1.2 meter UK Schmidt Telescope (UKST) at the Siding Spring Observatory - which was commissioned in 1973 - has been operating this new technology and ironing out any small software or hardware issues. Over the years, this small telescope has done amazing science such as the 6dF Galaxy and the RAVE surveys. 

However, this UKST was out of action from 2014-2016, whilst the telescope was being refurbished, and in 2018 it started back remote operations with the Australian Astronomical Optics (AAO). It was during this time that AAO’s new spectrograph and fibre positioning system called the “TAIPAN” instrument was installed.

The TAIPAN instrument comes with a novel technology called the Starbugs - which are self-mobile optical fibres that can move around the glass field plate in the focal plane of the telescope. 

The idea first started in 2004 to design miniature independently positionable robots on a glass plate to achieve a fast sky field configuration time. The need was found to fill the technology gap where manual target configuration, pick-and-place robots, and static fibres were mostly working in astronomy at the time. This new technology could maximise the efficient use of dark time and provide swift configuration of targets from one location of the sky to another.

The TAIPAN instrument is a self-contained spectrograph housing over a hundred of these Starbug robots that attach to the glass field plate by suction. From the glass field plate, these Starbugs feed to the spectrograph through a tube, called umbilical. As light from the Universe comes through the telescope, it is acquired by the Starbugs, then passed through the umbilical to the spectrograph which allows the object’s spectra to be analysed.

Spectrums that are analysed from astrophysical objects tell scientists about the interactions between matter (like atoms and molecules) and electromagnetic radiation (like photons of light) of the object being observed. 

This technique has distinctly changed our understanding of the Universe, as astrophysicists have been able to determine a large number of factors about astrophysical light sources, such as the chemical composition, density, mass, temperature and motion of objects. 

This is achieved through relative comparison of spectral signatures of elements observed in the laboratories on Earth, and then measuring any variation and anomalies to the spectral signature of the astrophysical source. This tells us not only what elements might be present in-situ, but also what conditions those elements are experiencing. 

The optical spectrograph wavelength of the TAIPAN instrument ranges from 370-870 nm and sits in a separate temperature-controlled room while the Starbugs are electronically controlled to position these fibres accurately. TAIPAN makes full use of the six-degree field-of-view of the telescope, which is 12 times larger than the Full Moon’s diameter when seen from Earth.

Starbugs are small three centimetres high piezo-ceramic cylinders, miniaturised robots that each hold their own optical fibre. They adhere to the glass field plate through vacuum and by applying variable pressure, an electric charge is generated to move them. 

This phenomenon is known as the piezo-electric effect. Starbugs use clever software to move dozens – even hundreds – of fibres simultaneously. The field plate X-Y positions of Starbugs are converted into sky positions and the instrument is slewed to the sky position by talking to the telescope. 

The UKST/TAIPAN has been operating since 2018. A good amount of time is spent on working out the nitty-gritty details of the software to maneuver the Starbugs to avoid tangling, collision, and reach to the positioning accuracy on the sky.

TAIPAN is also designed to perform remote observations of the sky. The instrument and telescope are operated remotely during the nighttime and very little human intervention is required for any hardware maintenance (if required) during the day. 

Starbugs are remotely configured to sky positions and the telescope is moved to that sky position. The light of stars and galaxies pass through the Starbugs, collimator, dichroic beam splitter (splitting light into two parts), gratings, and is collected at the end by two detectors. TAIPAN features a low-resolution spectrograph with an average resolution of R~2300.

TAIPAN is designed to be a survey telescope and the TAIPAN galaxy survey will measure the details of the expanding Universe. TAIPAN is currently in the commissioning phase and data for stars are being captured to calibrate the instrument. 

Additional data of nearby galaxies have also been captured to detect molecular lines from the gas in these galaxies. Data for the selected targets from the GAIA survey is also taken to find some extra-galactic targets known to be quasars. 

Quasars are extremely luminous sources of electromagnetic radiation, often found at great distances. The production of this high value of luminosity is the result of supermassive black holes in the centre of distant galaxies churning through nearby materials like stars and gas, which in turn fuels the raging production of radiation.

These quasars look like stars because of their optical colours and their appearance in the sky (they appear as point-like objects in the optical range, but also can be detected across other frequencies, like radio). The wavelength range of the spectrograph allows detection of the targets up to larger distances and is suitable for such extra-galactic, galactic, metal, and molecular searches. 

This makes TAIPAN a valuable tool to have as part of Australia’s suite of instrumentation and infrastructure, as our scientists can use it to not only determine the spectral composition of stars in our galaxy, but also tell which observed objects are quasars, and then analyse their light, to help us learn more about the Universe in general.

Video credit: Australian Astronomical Optics - Macquarie.