Astronomers have used simulated data to map glimpses of gravitational waves in the sky, which are ripples in cosmic space-time produced by orbiting objects. This image shows how space-based gravitational wave observatories expected to be launched in the next decade will enhance our understanding of our Milky Way home.
Astronomers used simulated data to map the sky with gravitational waves, revealing the need for space observatories to detect binary star systems. Future projects like LISA aim to discover thousands of these hard-to-detect systems, signaling a paradigm shift in space observation. (Artist's illustration - see simulation video below).
Since 2015, ground-based observatories have detected about a hundred events that represent the merger of systems of stellar-mass black holes, neutron stars, or pairs of the two. These signals typically last less than a minute, are relatively high-frequency, can appear anywhere in the sky, and originate from sources well beyond our galaxy.
Watch as gravitational waves from a simulated population of compact binary star systems combine to create a composite image of the entire sky. These systems contain white dwarfs, neutron stars, or black holes in tight orbits. Once space-based gravitational wave observatories begin operations in the next decade, it will be possible to create such maps using real data. Highlights indicate sources with stronger signals, lighter colors indicate sources with higher frequencies. Larger patches of color indicate sources that are less clearly located. The inset shows the frequency and strength of the gravitational signal, as well as the sensitivity limits of LISA (Laser Interferometer Space Antenna), an observatory designed by the European Space Agency (ESA) in collaboration with NASA and due to be launched in the 2030s. Source: NASA Goddard Space Flight Center
Cecilia Cilenti, a researcher at the University of Maryland, College Park and NASA's Goddard Space Flight Center in Greenbelt, Maryland "Binary star systems also populate the Milky Way, and we expect many of them to contain compact objects in tight orbits such as white dwarfs, neutron stars, and black holes," said Cecilia Chirenti. "But we need a space observatory to 'hear' them because the frequency of their gravitational wave buzz is too low for ground-based detectors to detect."
Astronomers call these systems UCBs (ultra-small binaries), and they expect that future observatories such as LISA (Laser Interferometer Space Antenna), a collaboration between the European Space Agency (ESA) and NASA, will detect tens of thousands of UCBs. UCBs are often hard to spot -- they are often faint in visible light, and astronomers currently know of only a handful of UCBs with orbital periods shorter than an hour. Discovering many new UCBs is one of LISA's main goals.
Artistic impression of LISA Pathfinder, ESA's mission to test technology for future space-based gravitational wave observatories. LISA is a space-based gravitational wave observatory developed based on the success of LISA Pathfinder and LIGO. Source: ESA-C. Carreau
Using data that simulated the expected distribution and gravitational wave signals of these systems, the team developed a method to combine the data into an all-sky view of the Milky Way UCB. The technique is described in a paper published in Acta Astronomica.
"Our image is directly analogous to observing a panoramic view of the sky with specific types of light, such as visible light, infrared, or X-rays," said Goddard astrophysicist Ira Thorpe. "The hope that gravitational waves bring is that we can observe the universe in a completely different way, and this image really drives home that. I hope one day I can see a version made with real LISA data on a poster or T-shirt."