Imagine trying to look at outer space using a massive device made up of satellites millions of kilometers apart trailing the Earth on its orbit around the sun.
But instead of light like a camera or telescope relies on, this device is based on ripples in gravity, measuring gravitational waves.
“We’re used to thinking about the universe in terms of pictures,” said Shane Larson, an astrophysicist at Northwestern University. “LISA’s going to sense the universe in gravity itself.”
LISA is the acronym for Laser Interferometer Space Antenna, and Larson has been thinking about if for a long time. He first got involved in the project in 1998 as a graduate student.
And now, more than a quarter of a century later, the physics and astronomy professor at Northwestern gets to see the culmination of a career-long aspiration come to life — and help make it happen.
The European Space Agency (ESA) announced last week its formal adoption of LISA.
Technically, LISA is a “space-based gravitational-wave observatory,” according to a Northwestern news release. And it’s set to launch in about 10 years.
Larson is the associate director of the Center for Interdisciplinary Exploration and Research in Astrophysics at Northwestern. He will be part of the team to build this new gravitational wave detector.
“This is really a milestone for LISA. We’ve crossed this threshold now where we’re confident that we can do it,” Larson said. “There’s like no doubt in any of our minds now.”
What is LISA?
Gravitational waves are “ripples or vibrations in space-time (the fabled ‘fabric’ of the universe) caused by massive objects moving with extreme accelerations,” according to Caltech.
LISA will actually consist of three spacecraft exactly 2.5 million kilometers apart, with laser beams connecting the three to form a giant equilateral triangle. As LISA trails the Earth on its orbit around the sun, gravitational waves will produce tiny changes in the lengths of the laser beams — smaller than the diameter of an atom.
Artist’s impression of three spacecrafts in a triangular configuration to form the Laser Interferometer Space Antenna (LISA). The satellites are separated by a distance of 2.5 million kilometers, connected by laser beams forming the arms of a high-precision laser interferometer.
Max Planck Institute for Gravitational Physics (Albert Einstein Institute) / Milde Marketing Science Communication / Exozet Effects
Larson said a device that measures gravitational waves rather than light, as telescopes do, allows for different study than light-based measurements. This includes the study of black holes, which don’t emit light and are therefore difficult to study with traditional methods.
“We’re going to see giant black holes falling into each other. We’re going to see all the dead binary stars in the Milky Way. We’re going to see small objects falling into giant black holes at the center of the galaxies,” Larson said.
Larson has studied gravitational dynamics for the majority of his scientific career. He was part of the team that first detected gravitational waves back in 2016 using the Laser Interferometer Gravitational-Wave Observatory (LIGO), LISA’s much smaller, on-Earth precursor.
Shane Larson, associate director of the Center for Interdisciplinary Exploration and Research in Astrophysics at Northwestern University, sits at his desk in Evanston. Larson has been working with the European Space Agency on their Laser Interferometer Space Antenna project for over two decades now.
Tyler Pasciak LaRiviere/Sun-Times
“I’m just so overwhelmed by the fact that it’s all going to happen during my professional career before I retire while I’m still here to work on it and see what kind of science we could do. And that’s just really, really exciting,” Larson said.
10 or 11 years to launch
LISA will allow scientists to observe a great number of things and their gravitational impacts, more than any other gravitational wave observatory.
The variety of things LISA can be used to study, from black holes to dead binary stars to white dwarfs, means it has the unique ability to connect much of the astrophysics community.
“It has the power in the context of our profession, to really help bring a whole bunch of different areas together, help people who don’t normally work together work together and help solve some puzzles that really we don’t have any other way of answering,” Larson said.
This project has a ways to go before launching anything into orbit. The European Space Agency has begun working with aerospace companies to develop building plans, and it will choose one of those companies and draw up final blueprints in the next year.
Larson said they’re also looking for scientists to apply to the LISA Science Team, whose 22 members will act as advisors for the 10-year project. By year 8 or 9, spacecrafts and lasers will be ready. By year 10 or 11, we should see LISA launch.
“In the next year or two, everything is really going to be set in motion,” Larson said. “We’re all very excited. We’ve been waiting decades.”
