New Map of the Night Sky Reveals 300,000 'Hidden' Galaxies

This image, produced by the LOFAR radio telescope network, contains nearly 300,000 previously unknown galaxies. (Photo: LOFAR)

The known universe just got a lot bigger.

An international team of more than 200 astronomers from 18 countries has published the first data from what promises to be an exciting new chapter in our exploration and understanding of the cosmos. Using the Low-Frequency Array (LOFAR), a large radio telescope network located mainly in the Netherlands, the group was able to discover more than 300,000 previously unknown galaxies. Even more incredible, this discovery came from observing only 2 percent of the Northern Hemisphere's night sky.

"This is a new window on the universe," Cyril Tasse, an astronomer at the Paris Observatory who was involved in the project, told AFP. "When we saw the first images we were like: 'What is this?!' It didn't look anything at all like what we are used to seeing."

Almost every object in this LOFAR image, created using radio astronomy, is a single galaxy. (Photo: LOFAR)

The image above looks different from other deep observations of the cosmos because of the way LOFAR detects objects. Unlike optical telescopes, which rely on light, the LOFAR array observes the night sky at extremely sensitive, low radio frequencies. Because merging galaxies generate radio emissions millions to billions of light-years away, LOFAR allows astronomers to plot objects that would otherwise be too faint to be seen with other space telescopes.

"What we are beginning to see with LOFAR is that, in some cases, clusters of galaxies that are not merging can also show this emission, albeit at a very low level that was previously undetectable," Annalisa Bonafede of the University of Bolognaand INAF said in a release. "This discovery tells us that, besides merger events, there are other phenomena that can trigger particle acceleration over huge scales."

The LOFAR 'superterp'. This is part of the core of the extended telescope located near Exloo, Netherlands. (Photo: LOFAR/Wikimedia)

LOFAR also picks up black holes, which emit radiation as they consume stars, planets, gas and other objects. This new form of observation will allow astronomers to study black holes as they grow and expand over time.

"With LOFAR we hope to answer the fascinating question: where do those black holes come from?" Huub Röttgering of Leiden University said in a release. "What we do know is that black holes are pretty messy eaters. When gas falls onto them, they emit jets of material that can be seen at radio wavelengths."

As shown in the video below, researchers were also able to determine the distance of some 50 percent of the new radio sources, allowing them to effectively create a 3D version of the new galaxy map.

For scale, it's worth pointing out that our own Milky Way galaxy has a diameter of 150,000 to 200,000 light-years and is estimated to contain 100 billion to 400 billion stars. In January, a new sky map (shown below) was created cataloging the positions, distances, motions, brightness and colors of more than 1.3 billion stars — an unprecedented feat.

This image of our Milky Way, the most detailed ever captured, features some 1.7 billion stars. (Photo: European Space Agency)

The researchers will build on their early success with LOFAR by conducting sensitive high-resolution captures of the entire northern sky. They estimate that when all the data is processed, they'll likely have discovered more than 15 million new radio sources.

"This sky map will be a wonderful scientific legacy for the future," Carole Jackson, director general of the Netherlands Institute for Radio Astronomy (ASTRON), said. "It is a testimony to the designers of LOFAR that this telescope performs so well."