Category Archives: European Southern Observatory (ESO)

Using GCs to test gravity in the weak acceleration regime

Globular clusters :: new preprint

Using globular clusters to test gravity in the weak acceleration regime:

Authors: Riccardo Scarpa, Gianni Marconi, Roberto Gilmozzi, Giovanni Carraro

Abstract: We report on the results from an ongoing program aimed at testing Newton’s law of gravity in the low acceleration regime using globular clusters. It is shown that all clusters studied so far do behave like galaxies, that is, their velocity dispersion profile flattens out at large radii where the acceleration of gravity goes below 1e-8 cm/s/s, instead of following the expected Keplerian fall off. In galaxies this behavior is ascribed to the existence of a dark matter halo. Globular clusters, however, do not contain dark matter, hence this result might indicate that our present understanding of gravity in the weak regime of accelerations is incomplete and somehow incorrect.

(As published on the European Southern Observatory “the Messenger”, Num. 128, June 2007. Seven pages, 4 figures, 2 tables)


New Globular Cluster Found in Milky Way

ESO Press Release:

“Star Family Seen Through Dusty Fog”

Images made with ESO’s New Technology Telescope at La Silla by a team of German astronomers reveal a rich circular cluster of stars in the inner parts of our Galaxy. Located 30,000 light-years away, this previously unknown closely-packed group of about 100,000 stars is most likely a new globular cluster.

ESO Press release: “Stars Too Old to be Trusted?”

NGC 6397 :: ESO Press Release

Stars Too Old to be Trusted?

A possible Stellar Solution to the Cosmological Lithium Problem

Analysing a set of stars in a globular cluster with ESO’s Very Large Telescope, astronomers may have found the solution to a critical cosmological and stellar riddle. Until now, an embarrassing question was why the abundance of lithium produced in the Big Bang is a factor 2 to 3 times higher than the value measured in the atmospheres of old stars. The answer, the researchers say, lies in the fact that the abundances of elements measured in a star’s atmosphere decrease with time…

VLT Image of a Unique Swarm of Stars, 47 Tuc

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[link :: 47 Tuc]

The Southern constellation Tucana (the Toucan) is probably best known as the home of the Small Magellanic Cloud, one of the satellite galaxies of the Milky Way. But Tucana also hosts another famous object that shines thousands of lights, like a magnificent, oversized diamond in the sky: the globular cluster 47 Tucanae. More popularly known as 47 Tuc, it is surpassed in size and brightness by only one other globular cluster, Omega Centauri….