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Editorial Briefing
Event Horizon Telescope captures first image of a black hole

Apr 2019

Event Horizon Telescope captures first image of a black hole

In a breakthrough for astronomy and physics, the Event Horizon Telescope (EHT) has obtained a direct image of a black hole. The first black hole captured in this manner is a supermassive one at the heart of a nearby galaxy, Messier 87. Further study of the imaged black hole should help scientists answer a host of astrophysical questions about black holes, as well as offer powerful and novel tests of Albert Einstein's general theory of relativity, the modern framework for gravity. See also: Astronomy; Black hole; Galaxy; Gravity; Physics; Relativity

Editorial Briefing
Pulsar timing discrepancies hint at low-frequency background gravitational waves

Jan 2021

Pulsar timing discrepancies hint at low-frequency background gravitational waves

The discovery of gravitational waves in 2015 revolutionized astronomy by opening up an entirely new way of studying extreme cosmic phenomena. Now researchers have reported the first evidence for a previously theorized but never-before-seen kind of low-frequency gravitational wave. The evidence comes in the form of a timing discrepancies detected in pulses of radio signals emanating from cosmic objects called pulsars. Rapidly spinning remnants of massive stars, pulsars send out beams of radiation as they rotate, similar to a lighthouse. Astrophysicists have long sought to leverage the clock-like precision of pulsars' pulse patterns to register miniscule changes in Earth's position caused by gravitational waves as the waves stretch and compress spacetime. These tiny changes in position would manifest as discrepancies in the timing of the pulses' arrival. See also: Pulsar; Radiation; Spacetime; Star

Editorial Briefing
Star's orbit of a supermassive black hole supports theory of relativity

Aug 2019

Star's orbit of a supermassive black hole supports theory of relativity

A star encircling the supermassive black hole at the core of the Milky Way Galaxy has offered a new, precise test of general relativity. Put forth by German-born U.S. theoretical physicist Albert Einstein in 1915, the theory of general relativity has held up as the most comprehensive theory of gravity, continuing to pass increasingly stringent tests. In this latest test, the star—designated S0-2—has had its 16-year orbit of the black hole mapped in three dimensions, tracing the influence of the black hole's powerful gravitational field. The star's orbit fully matches Einstein's predictions, a new study in the journal Science has found. The findings bolster Einstein's monumental theory still further and, in the process, once again reveal the limitations of English physicist Isaac Newton's paradigm of gravity, which was set forth in 1687 and subsequently prevailed for more than 200 years. See also: Black hole; Galaxy; Gravity; Milky Way Galaxy; Relativity; Star

Editorial Briefing
Star's rosette-shaped orbit around a supermassive black hole supports general relativity

Apr 2020

Star's rosette-shaped orbit around a supermassive black hole supports general relativity

The supermassive black hole at the center of the Milky Way serves as a unique laboratory for testing predictions of general relativity. In a new study, researchers report that a long-studied star—called S2 or sometimes S-02—moves in a rosette-shaped orbit around this black hole, just as general relativity mandates a star should. Nearly three decades’ worth of observations have borne out this observation that S2's orbit is not a simple ellipse. Instead, the orbit precesses, meaning that each time the star completes a loop around the black hole, the closest point of the orbit rotates away from the previous orbit's closest point, resulting in a rosette pattern. These findings are the first to measure precession by a star around a supermassive black hole. See also: Ellipse; Orbital motion; Precession; Star

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