GRAVITY tagged posts

Scientists have long known that Earth and Mercury have metallic cores. Like Earth, Mercury’s outer core is composed of liquid metal, but there have only been hints that Mercury’s innermost core is solid. Now, in a new study, scientists report evidence that Mercury’s inner core is indeed solid and that it is very nearly the same size as Earth’s solid inner core.

Some scientists compare Mercury to a cannonball because its metal core fills nearly 85% of the volume of the planet. This large core – huge compared to the other rocky planets in our solar system – has long been one of the most intriguing mysteries about Mercury...

Observations made with ESO’s Very Large Telescope have for the first time revealed the effects predicted by Einstein’s general relativity on the motion of a star passing through the extreme gravitational field near the supermassive black hole in the center of the Milky Way. This long-sought result represents the climax of a 26-year-long observation campaign using ESO’s telescopes in Chile.

Observations made with ESO’s Very Large Telescope have for the first time clearly revealed the effects of Einstein’s general relativity on the motion of a star passing through the extreme gravitational field very close to the supermassive black hole in the center of the Milky Way. This long-sought result represents the climax of a 26-year-long observation campaign using ESO’s telescopes in Chile.

Obscure...

This is an artist impression of the triple star system PSR J0337+1715, which is located about 4,200 light-years from Earth. This system provides a natural laboratory to test fundamental theories of gravity. Credit: NRAO/AUI/NSF; S. Dagnello

Einstein’s understanding of gravity, as outlined in his general theory of relativity, predicts that all objects fall at the same rate, regardless of their mass or composition. This theory has passed test after test here on Earth, but does it still hold true for some of the most massive and dense objects in the known universe, an aspect of nature known as the Strong Equivalence Principle? An international team of astronomers has given this lingering question its most stringent test ever...

The subject of this NASA/ESA Hubble Space Telescope image, IC 1727, is currently interacting with its near neighbor, NGC 672 (which is just out of frame). Credit: NASA/Hubble/ESA

Gravity governs the movements of the cosmos. It draws flocks of galaxies together to form small groups and more massive galaxy clusters, and brings duos so close that they begin to tug at one another. This latter scenario can have extreme consequences, with members of interacting pairs of galaxies often being dramatically distorted, torn apart, or driven to smash into one another, abandoning their former identities and merging to form a single accumulation of gas, dust and stars.

The subject of this Hubble Space Telescope image, IC 1727, is currently interacting with its near neighbor, NGC 672 (which is just out o...