GeminiFocus July, 2015 | Page 25

provide astronomers with this unprecedented view of its stars. This has been made possible thanks to the combination of two specific characteristics of GeMS: First, the capability of operating at near-infrared wavelengths (especially in the K pass-band); second, an innovative and revolutionary way to remove the distortions (blurriness) that the Earth’s turbulent atmosphere inflicts on astronomical images. To compensate for the degrading effects of the Earth’s atmosphere, the GeMS system uses three natural guide stars, a constellation of five laser guide stars, and multiple deformable mirrors. The correction is so fine that astronomers are provided with images of unparalleled sharpness. In the best K-band exposures of Liller 1, stellar images have an angular resolution of only 75 milliarcseconds, just slightly larger than the theoretical limit (known as the diffraction limit) of Gemini’s 8-meter mirror. This means that GeMS almost perfectly corrected Earth’s atmospheric distortions. The international research team published the results in the June 15 issue of The Astrophysical Journal (volume 806, page 152). The astro-ph version of the article can be found here. The results achieved on Liller 1 have been so important that the research team is currently expanding their work to other globular clusters, which promise to deliver even more exciting science. for instance, are old stars that mysteriously appear younger than they should be; these exotic stars may be formed by nearly headon collisions that cause the stars to merge, mixing their nuclear fuel and restoking the fire of the nuclear fusion. But collisions can also involve binary systems, with the effect of shrinking the initial size of the system, promoting the two components to interact and producing a variety of objects like lowmass X-ray binaries, millisecond pulsars, etc. In particular, millisecond pulsars are old neutron stars in a binary system whose rotation periods have been reaccelerated to milliseconds by matter accreting onto them from a companion star. Astronomers suspect that Liller 1 harbors a large population of these exotic objects. Although no millisecond pulsar has been directly observed up to now, the detection of intense gamma-ray emission (the most intense detected so far from a globular cluster) suggests a large hidden population. The Gemini observations confirm that this is possible. “Indeed, our observations confirm Liller 1 as one of the best ‘laboratories’ where the impact of star cluster dynamics on stellar evolution can be studied: It opens the window to a sort of stellar sociology study, aimed at measuring the impact of the reciprocal influence of stars when they are forced to live in conditions of extreme crowding and stress,” concluded Ferraro. Additional information can be found at http://www.cosmic-lab.eu/Cosmic-Lab/ Liller1.html Background: Stellar Collisions Stellar collisions are important because they can provide the key to understanding how certain exotic objects, which cannot be explained by the passive evolution of single stars, originate. “Blue Stragglers,“ July 2015 GeminiFocus 23