In the most detailed survey of the southern sky using radio waves, astronomers have mapped about a million previously undiscovered galaxies outside the Milky Way.
The fast ASKAP continuum (or RACS) has firmly placed CSIRO’s Australian SKA Pathfinder Radio Telescope (ASKAP) on the international astronomical map.
Although the past surveys took several years, ASKAP’s RACS survey was conducted in less than two weeks-breaking the previous speed record. The image generated by the collected data is five times more sensitive than previous images, while its level of detail is twice as high.
What is radio astronomy?
Modern astronomy is a multi-wavelength enterprise. What does it mean?
Well, most objects in the universe (including humans) emit radiation in a broad spectrum (called the electromagnetic spectrum). This includes visible and invisible light, such as X-rays, ultraviolet rays, infrared rays 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 in the universe, from cold clouds of gas to supermassive black holes.
Long wavelengths easily pass through clouds, dust and atmosphere, but require a large antenna to receive. Australia̵
From our position in the southern hemisphere, we can enjoy the most spectacular view of the center of the Milky Way. For thousands of years, indigenous astronomers have realized this benefit.
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Radio astronomy is a relatively new field of research, with a history dating back to the 1930s.
The Molonger Sky Survey at the University of Sydney is the first detailed 30cm southern sky radio map, which includes everything a telescope can see from its location in the southern hemisphere. The survey was completed in 2006, and it took nearly a decade to observe 25% of the entire sky and produce the final data product.
The team of CSIRO’s Astronomy and Space Science Department observed 83% of the sky in just 10 days, breaking this record.
Through the RACS survey, we have generated 903 images, each of which requires 15 minutes of exposure time. Then, we combined them into a map covering the entire area.
To those who look up at the night sky themselves, the panorama of the radio sky looks surprisingly familiar. However, in our photos, almost all the bright spots are entire galaxies, not individual stars.
Please take a virtual tour below.
Astronomers who are studying the catalog have discovered about 3 million galaxies, much more than the 260,000 galaxies found in the Molonge Sky Survey.
Why do we need to map the universe?
We know how important the map on the earth is. They provide critical navigation assistance and provide information about the terrain, which is very useful for land management.
Similarly, the sky map provides important research and statistical evidence for astronomers. They can tell us the behavior of certain galaxies, such as whether they exist in a companion cluster or drift by themselves.
Read more: When you look up, how far in time will you see?
Being able to conduct round-the-clock surveys in less than two weeks provides many opportunities for research.
For example, little is known about how the radio sky changes over a time frame of days to months. Now, we can periodically revisit the 3 million galaxies identified in the RACS catalog to track any differences.
Similarly, some of the biggest unsolved problems in astronomy have to do with how the galaxies we see become ellipses, spirals, or irregular shapes. A popular theory is that large galaxies grow through the merger of many smaller galaxies.
However, the details of the process are elusive and difficult to coordinate with simulation. To understand the 13 billion years of cosmic history of our universe, we need a telescope, which can see and accurately map everything discovered from a long distance.
High technology makes new goals within reach
CSIRO’s RACS survey is an amazing progress, which is achieved due to the leap in space technology. The ASKAP radio telescope was put into use in February last year to increase speed.
CSIRO engineers have developed an innovative radio receiver called “phased array feed” and a high-speed digital signal processor dedicated to ASKAP. It is these technologies that provide ASKAP’s broad field of view and rapid measurement capabilities.
In the next few years, ASKAP is expected to conduct more sensitive investigations in different wavebands.
At the same time, the RACS survey catalog is greatly improving our understanding of the radio sky. It will continue to be an important resource for researchers around the world.
You can download full-resolution images from the ASKAP data file.