The newest generation of radio telescopes—including the Australian Square Kilometre Array Pathfinder (ASKAP) and MeerKAT, a telescope in South Africa—is revealing incredibly faint cosmic objects, never before seen.

In astronomy, surface brightness is a measure that tells us how easily visible an object is. The extraordinary sensitivity of MeerKAT and ASKAP is now revealing a new "low surface brightness universe" to radio astronomers. It's comprised of radio sources so faint they have never been seen before, each with their own unique physical properties.

Many of the ASKAP results presented here were obtained with one of its major observing programs called EMU (Evolutionary Map of the Universe). EMU is mapping the entire southern sky with an unprecedented sensitivity and will deliver the most detailed map of the southern hemisphere sky to date—a spectacular new radio atlas that will be used for decades to come.

EMU's all-hemisphere coverage paired with ASKAP's exceptional sensitivity, especially within the Milky Way, is what's yielded so many recent discoveries.

Here's what they're teaching us.