... Bad Astronomy . ... Bitesize Astronomy . ... The next step up are true clusters, called open clusters . Open clusters (sometimes misleadingly called "galactic clusters") are groups of stars ranging in size from a few dozen stars up to tens of thousands. ... The youngest is about 1 or 2 million years old, while the oldest is about 6 or 7 billion years, making it just older than our own solar system. ... So by looking at the stars in the cluster we can tell pretty well how old they are. ...

... Tidal circularisation of white dwarfs and formation of sources of gravitational waves in globular clusters . ... I point out that a major fraction of white dwarfs tidally captured by the black hole may be destroyed by tidal inflation and rotational break-up during ongoing tidal circularisation, and therefore the formation of tight binaries is inhibited. However, some fraction may survive tidal circularisation through being spun up to high rotation rates where tidal interactions are less effetive. ...

Results from 6m telescope observations of globular clusters in dwarf galaxies Sharina M. We consider properties of globular clusters in dwarf galaxies observed with the multi-slit unit of the SCORPIO spectrograph at the SAO 6m telescope. ... Studying GCs in dwarf galaxies at the faintest end of the galaxy luminosity function provides valuable information for a better understanding of galaxy evolution and evolutionary connection between globular clusters and nuclei of galaxies. ...

... We found that 10 metal-poor globular clusters are greately distinguished for anomalously small masses on the "destruction rate-mass" plain. As it turned out, these poor clusters, situated 15 kpc farther from the Galactic centre, are somewhat younger than the bulk of the metal-poor globulars, and have anomalously red horizontal branches. ... At the same time, deficiency of distant massive clusters is noticeable with increasing distance from the galactic centre. ...

... Future seminars . P a s t seminars . Seminar council . Stability of cold fronts in clusters of galaxies " . E. Churazov (IKI, MPA) . ... One of the insteresting results of Chandra and XMM-Newton observatories is the discovery of sharp structures in the X-ray surface brightness of galaxy clusters. These structures (a.k.a. cold fronts) are likely associated with the contacted discontinuities formed when a hot gas flows over a colder gravitationally bound gas cloud. ...

... no comet has been observed with an orbit that indicates that it came from interstellar space, . ... From this he proposed that comets reside in a vast cloud at the outer reaches of the solar system. ... Unfortunately, since the individual comets are so small and at such large distances, we have no direct evidence about the Oort Cloud. ... T he Kuiper Belt is a disk-shaped region past the orbit of Neptune roughly 30 to 100 AU from the Sun containing many small icy bodies. ... Small Bodies .. ...

... In the past used to check pn/ MOS cross calibration Example of old vs new pn/ mos Residuals in the form of ratio data / model for PN data on MOS best fitting model Example of old vs new pn/ mos Residuals in the form of ratio data / model for PN data on MOS best fitting model ACIS S3 vs EPIC pn · · Same thing, only now we compare Chandra ACIS S3 with ... Flux cross-cal · · The new HRMA calibration impacts on the ACIS/EPIC flux cross calibration. ...

... The most powerful and widely used methods to calculate the scattering matrix of a fractal cluster are based on the coupled dipoles methods (e.g. the Discrete Dipole Approximation, DDA) and the theory of light scattering by a cluster of spherical particles [2-4]. ... At present the procedure of calculation of the scattering matrix is well developed for both an oriented cluster of spherical particles and for chaotically oriented clusters of such particles [4]. ...

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... Over the first 4 years, its X-ray telescopes eROSITA and ART-XC will survey the whole sky with a record sensitivity in the 0.5-10 keV energy band. ... The goal of the second international Spectrum-RG conference is to discuss the different scientific topics addressed by the mission, synergies with surveys at other wavelengths, and requirements to follow-up observations.Contributed talks and poster presentations are invited on the topics related to the SRG science goals. ... Active galactic nuclei . ...

... The routines implemented are CLUSTER which has 8 options for hierarchical clustering and PARTITION which carries out non--hierarchical clustering. ... The former is non--hierarchical clustering or partitioning. The latter is hierarchical clustering. Brief consideration will show that a sequence of n-1 agglomerations are needed to successively merge the two closest objects and/or clusters at each stage, so that we have a set of n (singleton) clusters, n-1 clusters, ..., 2 clusters, 1 cluster. ...