In a very detailed survey of the southern sky using radio waves, astronomers have mapped millions of previously unknown galaxies outside the galaxy.
The Rapid ASKAP Continuous Survey (or RACS) has firmly placed CSIRO’s Australian SKA Pathfinder Radio Telescope (ASKAP) on the international astronomy map.
While past surveys have taken years to complete, ASKAP’s RACS survey was conducted in less than two weeks – breaking previous records for speed. The data collected has produced images that are five times more sensitive and twice as detailed than the previous ones.
What is radio astronomy?
Modern astronomy is a multi-wavelength adventure. What do we mean by this?
Well, most of the universe (including humans) emits radiation over a broad spectrum known as the Broadcut Magnetic Spectrum, which includes visible and invisible light such as X-rays, ultraviolet light, infrared light and radio waves.
To understand the universe, we need to observe the whole electromagnetic spectrum because each wavelength carries different information.
Radio waves have the longest wavelengths of all forms of light. They allow us to study some of the most extreme atmospheres in the universe, from cold gas clouds to supermassive black holes.
Long wavelengths pass easily through clouds, dust and atmosphere, but need to be achieved with a large antenna. Radio Australia’s wide open (but relatively low alt altitude) spaces are the perfect place to build a large radio telescope.
From our position in the Southern Hemisphere we have some of the most spectacular views of the center of the galaxy. Indigenous astronomers have praised this benefit for millennia.
A stellar success
Radio astronomy is a relatively new field of research dating back to the 1930s.
The first detail of the southern sky is 30 cm. The radio map – which includes everything the telescope can see from its location in the Southern Hemisphere – was the Molonglow Sky Survey of the University of Sydney. Completed in 2006, the survey took almost a decade to produce 25 percent of the sky’s observations and final data products.
Our team from CSIRO’s Department of Astronomy and Space Science has surpassed this record by surveying 83 percent of the sky in just ten days.
We produced 903 images through the RACS survey, each requiring a contact time of 15 minutes. We then combined this into a map covering the entire area.
The resulting panorama of the radio sky will look surprisingly familiar to anyone who has seen it for themselves in the night sky. In our photos, however, almost all of the bright points are full galaxies rather than individual stars.
Take our virtual tour below (it works better on the big screens).
Astronomers working on the catalog have identified about three million galaxies – significantly more than the 260,000 galaxies identified during the Molonglow Sky Survey.
Why do we need to map the universe?
We know how many important maps there are on Earth. They provide critical navigational assistance and provide information about terrain that is useful for land management.
Similarly, sky maps provide astronomers with important references to research and statistical power. They can tell us how certain galaxies behave, such as whether they are in clusters of peers or not.
Being able to conduct an all-sky survey in less than two weeks opens up numerous opportunities for research.
For example, little is known about how the radio sky changes over a period of months to months. We can now regularly revisit each of the three million galaxies known in the RACS catalog to track any differences.
Also, some of the biggest unanswered questions in astronomy are related to how galaxies have become elliptical, spiral, or irregular in shape. A popular theory suggests that large galaxies grow through the merger of many smaller findings.
But the details of this process are elusive and difficult to reconcile with simulations. Understanding 13 billion years or more of the global history of our universe requires binoculars that can see at great distances and accurately map everything it finds.
High technology setting new goals within reach
CSIRO’s RACS Survey is a spectacular advance made possible by huge jumps in space tech. The ASKAP radio telescope, fully operational in February last year, was built for motion.
CSIRO’s engineers developed innovative radio receivers specifically for ASKAP called “phased array feeds” and high speed digital signal processors. It is these technologies that provide ASKAP’s wide view and fast survey capabilities.
Over the next few years, ASKAP is expected to conduct more sensitive surveys across different wavelength bands.
Meanwhile, the RACS survey list is greatly improving our knowledge of radio skies. It will continue to be a major tool for researchers around the world.
Full resolution images can be downloaded from the ASKAP data archive.
Aiden Hotan, ASKAP Leading Scientist, CSIRO.
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