How South Africa’s MeerKAT Captured The First Image Of The Oldest Stars In The Universe

South Africa’s MeerKAT peers deep into the Universe 2
Composite of radio galaxies and MeerKAT telescope: Thousands of galaxies are visible in this radio image covering a square degree of sky near the south celestial pole, made by the MeerKAT radio telescope array (foreground) in the South African Karoo semi-desert. The brightest spots are luminous radio galaxies powered by supermassive black holes. The myriad faint dots are distant galaxies like our own Milky Way, too faint to have been detected before now. Because radio waves travel at the speed of light, this image is a time machine that samples the star formation history of the universe. Credit: SARAO; NRAO/AUI/NSF

The South African Radio Astronomy Observatory’s (SARAO) 64 dish MeerKAT array, one of the world’s most powerful and modern radio telescopes which was officially launched in July last year, has just released a new image of some of the oldest galaxies ever detected. These galaxies, somewhere between eight and eleven billion light-years away, have never been seen before, and their detection closes the long-standing gap in our observations of the universe’s history. The ability of this telescope to see these elusive objects is an impressive technological achievement and hints at the future capabilities of the Square Kilometer Array telescope.

The DEEP2 image was integrated from signals collected over the course of nine months, for up to 16 hours at a time. The raw data was shipped to the Centre for High-Performance Computing in Cape Town where it was processed to produce the final image, which is the radio equivalent of a long-exposure photograph in which the shutter is kept open for 160 hours. It covers a region of the sky roughly equivalent to five full moons and shows over seventeen thousand galaxies. The brightest objects are galaxies with active supermassive black holes at their centres. The fainter, more numerous objects are more interesting to scientists, however, as these are our first view of ancient galaxies creating the universe’s first-ever stars.

Scientists have been observing distant stars and galaxies for a very long time. Because the speed of light is finite, distant objects give us a snapshot of how they looked in the past. Taken together, these observations have provided much of the evidence for our current understanding of how the Universe evolved into its current state. However, there have been regions that remained unobserved. Visible light can only show us so much, partly because it is blocked by dust clouds, but also because the expansion of the universe causes it to change frequency over time. Over a far enough distance, and given enough time, a beam of white light will gradually shift to red, then infrared, or even microwave light. These lower frequencies are not blocked by dust, however, which means they can be detected. Radio telescopes like MeerKAT are therefore essential for us to understand how the universe came to be, which in turn confirms and refines the basic science behind modern technological innovation.

The DEEP2 image serves other purposes than pure science, however. MeerKAT is a new telescope which has been officially operating for only six months. Images like these are important to measure how the instrument performs in practice. In processing this image, the operators were able to identify calibration errors and their feedback helped refine the software which controls the telescope, allowing for more precise control and better quality images. In the process, they’ve demonstrated that MeerKAT has met its design requirements, and is successfully making observations that could not be achieved by existing radio telescope arrays.

MeerKAT was built as South Africa’s precursor instrument for the Square Kilometer Array (SKA), to demonstrate the country’s ability to build and operate such a massive instrument. It is an expansion of the earlier Karoo Array Telescope (KAT), and is composed of 64 radio receiver dishes, each one 13.5 meters across, distributed across approximately 8km in the Karoo region of South Africa. It is operated by SARAO and will form part of the core detection region of the SKA, which will be the largest and most sensitive radio telescope ever built. SARAO is a facility of the National Research Foundation, which is an agency of South Africa’s Department of Science and Innovation.

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