Using simulated data, astronomers created an image of the sky as it would appear in gravitational waves, which are cosmic ripples in space-time created by orbiting objects. The image shows how space-based gravitational wave observatories, expected to become operational in the next decade, will improve our understanding of our galactic home.

Since 2015, ground-based observatories have detected nearly a hundred events representing mergers of systems that combine stellar-mass black holes, neutron stars, or both. Usually the signals last less than a minute, have relatively high frequencies, can appear at any point in the sky, and their sources lie far beyond the boundaries of our galaxy.

“Binary systems are also found in the Milky Way, and we expect many of them to contain compact objects such as white dwarfs, neutron stars and black holes in tight orbits,” said researcher Cecilia Chirenti from the University of Maryland, College Park. and NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “But we need a space observatory to ‘hear’ them, because gravitational waves hum at frequencies too low for detectors on the ground.”

Astronomers call these systems UCB (Ultra Compact Binary Systems) and expect future observatories such as LISA (Laser Interferometric Space Antenna) led by ESA (European Space Agency) in collaboration with NASA to detect tens of thousands of them. UCBs are often difficult to detect; they are generally faint in visible light, and astronomers currently know of only a few with orbital periods less than an hour. The discovery of many new UCBs is one of the main goals of LISA.

See how gravitational waves from a simulated population of compact binaries are combined into a synthetic map of the entire sky. Such systems contain white dwarfs, neutron stars or black holes in narrow orbits. Similar maps using real data will be possible as space-based gravitational wave observatories become operational in the next decade. Brighter dots indicate sources with stronger signals, and lighter colors indicate sources with higher frequencies. Larger colored dots indicate sources whose locations are less known. The inset shows the frequency and strength of the gravitational signal and the sensitivity limit of LISA (Laser Interferometric Space Antenna), an observatory currently being designed by ESA (European Space Agency) in collaboration with NASA to be launched in the 2030s. Credit: NASA Goddard Space Flight Center

Using data modeling the expected distribution of these systems and their gravitational wave signals, the team developed a way to combine the data into a panoramic UCB image of the galaxy. Published in the article Astronomy Magazine, explains this technique.

“Our image is a direct analogue of a panoramic view of the sky in a particular type of light, such as visible, infrared or X-ray,” said Goddard astrophysicist Ira Thorpe. “The promise of gravitational waves is that we can observe the universe in a completely different way, and this image really highlights that. I hope to see a version of it made from real LISA data on a poster or t-shirt one day.”