This cartoon depicts the Double Pulsar, a pair of stellar corpses bound by gravity (although it is not shown to scale). The corpses spin rapidly, beaming radiation into space. When such a beam sweeps across Earth, we see a brief "pulse" of energy. The Double Pulsar is the only pair of these objects yet discovered. By monitoring changes in their pulses, scientists can learn about the stars themselves and about General Relativity, Albert Einstein's theory of gravity. The system is about 2,400 light-years from Earth. [Michael Kramer (Jodrell Bank Observatory, Univ. Manchester)]
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Passing the Test
The more scientists try to break down Albert Einstein’s theory of gravity, the stronger it looks. An experiment that kept an eye on a pair of extreme dead stars, for example, confirmed several of its predictions.
The theory is General Relativity. Einstein presented it in 1915, and it’s withstood every test since then. Yet scientists know that it must break down at the tiniest scales, or inside objects like black holes. They’re pushing to find its limits.
The new experiment spent 16 years watching the Double Pulsar — two dead stars in a tight orbit around each other. A pulsar is the crushed core of a once giant star. It spins rapidly, beaming energy into space like a lighthouse. Telescopes on Earth record each “pulse” of energy.
The Double Pulsar is about 2400 light-years away. Each of its stars is heavier than the Sun, but only the size of a city. One of them spins about three times per second, the other about 45 times per second.
Astronomers used radio telescopes all across Earth to watch the stars. The results showed that the pulsars are moving closer together. That confirms that they’re producing gravitational waves — ripples in space-time — just as relativity predicts.
The study also measured how the pulsars’ gravity affects the way light waves move, how the pulsars affect the flow of time, and more. The results all matched relativity’s predictions — more confirmation of Einstein’s theory of gravity.
Script by Damond Benningfield