Free Astronomy Magazine March-April 2016

only in relatively nearby galaxies. In addi- tion, in being enveloped by the bulges of the galaxies hosting them, the light emit- ted by the two structures mixes up, thus greatly complicating the spectroscopic anal- ysis if the goal is to separate the individual contributions and identify the properties of the stars that form the nuclear disks. For this reason, despite the various attempts made from the end of the 20 th century on- wards, until now no one has been able to determine with the necessary accuracy the age of the stars of a nuclear disk. Until now that is. In fact, in the February issue of the Monthly Notices of the Royal Astronomical Society were published the results of two studies that for the first time provide that valuable data for two distinct nuclear disks. The first study is from an international team led by Marc Sarzi (Center for Astro- physics Research, University of Hertford- shire), and has as its subject NGC 4458, an elliptical galaxy in Virgo, about 53 million light-years away (visual magnitude 11.8). In processing the galaxy’s archival data col- lected with the multi-object spectrograph VIMOS (mounted on the telescope Melipal, one of the four units of the VLT), along with images taken with the Hubble Space Telescope, Sarzi and colleagues were able to differentiate the properties of the stel- lar population of the nuclear disk from T he barred len- ticular galaxy NGC 1023. At the centre of this gal- axy there is a compact disk of stars, whose age was calculated with high preci- sion by Corsini’s team.[STScI/NASA] On the side, the famous 6-metre Bolshoi Teleskop Azimutalnyi of the Zelenchuksky Observatory, which provided part of the spec- tra of NGC 1023. [SAO RAS]