Cutting-edge technology: Macquarie’s Huntsman Telescope observes space during the day. Credit: Macquarie University
Ah, the magic of the firmament in the night sky! Wouldn’t it be nice if you could observe the stars during the day too? Absurd and, instead, now it seems possible. Researchers at Macquarie University in Sydney, Australia, used their Huntsman telescope to precisely measure and track stars, satellites and other objects in the sky, not only at night – when all astronomers generally scan the sky – but also when the Sun is at noon.
«For centuries, people have tried to observe stars and satellites in the visible wavelengths in daylight, but it has always been very difficult to do. Our tests show that the Huntsman can achieve remarkable results even during daylight hours»explains the lead author and PhD student in astrophysics Sarah Caddywho also contributed to the design and operation of the Huntsman telescope at theSiding Springs Observatory in Coonabarabran.
Originally designed for ultrasensitive observations of the night sky, the Huntsman Telescope features a unique array of 10 camera lenses working in parallel, powering 10 ultrafast CMOS sensors that together can take thousands of short exposure images per second. The telescope combines astronomical camera and astro-mechanical focusing equipment with an array of 10 highly sensitive 400mm Canon lenses, oriented to cover the same portion of the sky. The connected camera is thus able to process images and manage very large data streams in an instant, using robotic control to follow and capture fast-moving objects and guaranteeing continuous monitoring of objects for 24 hours.
Since the Sun blocks out most of the light from other celestial objects, astronomers traditionally observe only at night – this multi-objective telescope could open up new possibilities for daytime astronomy. «Being able to make accurate observations around the clock breaks long-standing restrictions on astronomers from scanning the sky»he claims Lee Spitlerresponsible for space projects at theAustralian Astronomical Optics (Aao) by Macquarie, co-author ofitem presented in the magazine Publications of the Astronomical Society of Australia containing the results of observational tests.
Sarah Caddy with the Huntsman telescope she helped design and build. This optical telescope features a unique array of 10 camera lenses working in parallel, powering 10 ultra-fast CMOS camera sensors. Credit: Macquarie University
Caddy’s idea was to experiment with special “broadband” filters on a test version of the Huntsman – a scaled-down copy of the single-lens telescope installed at the Macquarie University observatory – to block most of the light daytime, allowing only the specific wavelengths of light emitted by celestial objects to pass through. The prototype mini-telescope allowed the research team to evaluate various settings in a controlled environment without affecting the Huntsman telescope.
What are the advantages of being able to observe the universe even during the day? There are many. First of all, the possibility of constantly monitoring some bright stars that cannot be observed at night because they are too close to the Sun. An example is the red supergiant Betelgeuse, a nearby star about 650 light-years away, in the Orion constellation of the Milky Way. Questa star is of great interest for astronomers since it is remarkably darkened between 2019 and 2020, probably due to a major expulsion of gas and dust. We also know that Betelgeuse will explode “soon” – in astronomical terms, any time between now and the next few million years – but we don’t know exactly when it will happen. But Betelgeuse is observable for about four months of the year and only during the day, when the Sun comes between Betelgeuse and Earth. It would therefore be a shame to miss his explosive moment. «Without this diurnal mode, we won’t know whether one of the brightest stars in the sky has gone supernova until a few months after its explosive light reaches Earth.»says Spitler.
Nighttime 3D rendering of Betelgeuse, the bright star in the constellation Orion with its dynamic expanding corona and eruption of gas or dust. Credit: Macquarie University
With a seven-month investigation of the brightness of the red supergiant during the day, the research team confirmed that the Huntsman Telescope’s daytime photometry data for Betelgeuse matches measurements from observatories around the world and space telescopes. So, if all goes well, the telescope will make happy astronomers who like to study stars that become supernovae and eject enormous quantities of stellar material, to understand the formation of chemical elements in the universe.
Supernova explosions in the Milky Way are relatively rare – the last one was in 1604 – so much so that astronomers, even today, stop to study the explosion of a supernova in a mini-galaxy close to ours which occurred in 1987. «This discovery paves the way for ongoing, long-term studies of stars like Betelgeuse, which undergo powerful eruptions towards the end of their lives»Spitler continues.
Being able to make daytime observations also has another major advantage in the rapidly expanding field of space situational awareness (SSA), the close-up monitoring of an ever-growing population of satellites, space debris and other man-made objects orbiting the Earth.
A daytime view of the nearby star Betelgeuse, located about 650 light-years away. Credit: Macquarie University
Daytime astronomy will be increasingly critical as we enter the next space age: More satellites will be launched in the next ten years than in the entire history of human space exploration. Satellite photometry – an astronomical technique that uses optical telescopes to study variations in the brightness of celestial objects – can reveal valuable information, including the composition, age and condition of orbiting objects.
«With around 10,000 active satellites already circling the planet and plans to launch another 50,000 satellites into low Earth orbit over the next decade, there is a clear need for networks of dedicated day and night telescopes to continuously detect and track satellites. Opening satellites to daytime observation will allow us to monitor not only their position, but also their orientation, combining the information we obtain from radar and other monitoring methods»explains Caddy who with his team has already used the mini-Huntsman for several months to refine monitoring techniques, systematically studying factors such as optimal exposure times, observation timing and precise tracking of targets even through turbulence atmospheric.
«We have perfected a methodology for daytime observation and demonstrated that it can be done with affordable, high-end equipment. Daylight astronomy is an exciting field, and thanks to advances in camera sensors, filters and other technologies, we have seen dramatic improvements in the sensitivity and accuracy achievable under bright sky conditions», concludes the researcher.
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