Astronomers have carried out mapping of a million previously unknown galaxies beyond the Milky Way, making the most detailed survey of the southern sky using radio waves.
The Rapid ASKAP Continuum Survey (or RACS) has placed CSIRO’s Australian SKA Pathfinder Radio Telescope (ASKAP) firmly on the international astronomy map.
While previous surveys have taken years to complete, ASKAP’s RACS survey was conducted in less than two weeks – breaking the previous record for speed. The data collected has produced images as detailed as five times more sensitive and twice as previous ones.
What is radio astronomy?
Modern astronomy is a multi-wavelength enterprise. What do we mean by this?
Well, most objects (including humans) in the universe emit radiation over a broad spectrum, called the electromagnetic spectrum. It includes both visible and invisible light such as X-rays, ultraviolet light, infrared light and radio waves.
To understand the universe, we need to observe the entire electromagnetic spectrum because each wavelength carries different information.
Radio waves have the longest wavelength of all forms of light. They allow us to study some of the most extreme environments of the universe, from cold clouds of gas to supermassive black holes.
Long wavelengths pass easily through clouds, dust and atmosphere, but need to be obtained with larger antennas. Australia’s wide open (but relatively low altitude locations) are the perfect place to build large radio telescopes.
We have the most spectacular views of the center of the Milky Way from its position in the Southern Hemisphere. This benefit has been appreciated by indigenous astronomers for millennia.
A stellar success
Radio astronomy is a relatively new field of research, dating back to the 1930s.
The first detailed 30 cm radio map of the southern sky – which includes everything a telescope can see from its location in the Southern Hemisphere – was the Molonglo Sky Survey of the University of Sydney. Completed in 2006, the survey took nearly a decade to observe 25 percent of the entire sky and produce final data products.
Our team in CSIRO’s Astronomy and Space Science Division broke this record by surveying 83 percent of the sky in just ten days.
With the RACS survey we produced 903 images, each requiring an exposure time of 15 minutes. We then combined them into a map covering the entire region.
The resulting panorama of the radio sky will be surprisingly familiar to anyone who has seen the night sky themselves. In our photos, however, almost all of the bright points are entire galaxies rather than individual stars.
Take our virtual tour down (it works better on the big screen).
Astronomers working on the catalog have identified about three million galaxies – more than the 260,000 galaxies identified during the Molonglo Sky Survey.
Why do we need to map the universe?
We know how important maps are on Earth. They provide significant naval assistance and provide information about the area which is useful for land management.
Similarly, sky maps provide astronomers with important references for research and statistical power. They can tell us how some galaxies behave, as if they exist in groups of peers or flow from space on their own.
Being able to do an all-sky survey in less than two weeks opens up many research opportunities.
For example, little is known about how often the radio sky changes in months of days. We can now regularly revisit any of the three million galaxies identified in the RACS catalog to track differences.
In addition, some of the biggest unanswered questions in astronomy relate to how galaxies became elliptical, spiral, or irregularly shaped. One popular theory suggests large galaxies evolve through the merger of many smaller ones.
But the details of this process are elusive and difficult to reconcile with simulation. To understand the 13 billion or so years of the history of our universe, a telescope is needed to see the vast distances and accurately map what it finds.
High technology is putting new targets within reach
CSIRO’s RACS survey is an amazing advance made possible by a massive leap in space technology. The ASKAP radio telescope, which was fully operational in February last year, was designed for speed.
CSIRO engineers developed innovative radio receivers called “phased array feed” and high-speed digital signal processors specifically for ASKAP. It is these technologies that provide a wide scope of ASKAP and the ability to conduct rapid surveys.
In the next few years, ASKAP is expected to conduct even more sensitive surveys in different wavelength bands.
Meanwhile, the RACS survey list is greatly improving our knowledge of Radio Akash. It will remain an important resource for researchers around the world.
Full resolution images can be downloaded from the ASKAP data collection.
Aidan Hotan, Chief Scientist of ASKAP, CSIRO.
This article is republished from Conversation under a Creative Commons license. Read the original article.