The ground-based LIGO Detector last year detected gravitational waves emitted by two black holes colliding to form a single massive object. It was followed by the testing of LISA Pathfinder, a space-based observatory built to detect low-frequency gravitational waves. European scientists led by Professor Karsten Danzmann of the Max Planck Institute said Tuesday that LISA Pathfinder has exceeded all expectations.
A space observatory to detect gravitational waves
Findings of their study were published in the Physical Review Letters. The testing of LISA Pathfinder’s technology was done at an operational orbit of 1.5 million kilometers from Earth. Gravitational waves were predicted by Albert Einstein in his theory of relativity in 1915. They are tiny oscillations in the fabric of spacetime caused by some of the most powerful cosmic events like supernovae, merger of black holes and the like.
Danzmann said LISA Pathfinder performed five times better than originally required. While LIGO could detect gravitational waves only at high frequencies, LISA Pathfinder will “take space science into a whole new era” because it focuses on low frequencies. Most of the big events in the Universe radiate at low frequencies. The test demonstration involved placing “two test masses in a near-perfect gravitational free-fall to control and measure their motion,” says Deutsche Welle.
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LISA Pathfinder’s test masses are still with respect to each other
There is a pair of identical 2kg gold cubes separated by 38 centimeters on the spacecraft. LISA Pathfinder shields the cubes from external forces like solar winds to ensure that the two test masses act under gravity alone. They are almost motionless with respect to each other while falling freely through space under the influence of gravity. Researchers found that the relative acceleration of the two masses was lower than one part in ten millionth of a billionth of Earth’s gravity.
Alvaro Giménez, the European Space Agency’s Director of Science, said that LISA Pathfinder’s test masses are “still with respect to each other to an astonishing degree.” Its precision was more than five times better than researchers were expecting. This level of control will enable the observatory to monitor and investigate low-frequency gravitational waves.