Related papers: The Age of the Universe
The rotation-mass-age relationship offers a promising avenue for measuring the ages of field stars, assuming the attendant uncertainties to this technique can be well characterized. We model stellar angular momentum evolution starting with…
Globular clusters are among the oldest structures in the Universe and they host today low-mass stars and no gas. However, there has been a time when they formed as gaseous objects hosting a large number of short-lived, massive stars. Many…
A significant fraction of stars in globular clusters (about 70%-85%) exhibit peculiar chemical patterns with strong abundance variations in light elements along with constant abundances in heavy elements. These abundance anomalies can be…
We performed the photometric analysis of M2 and M92 globular clusters in g and r bands of SLOAN photometric system. We transformed these g and r bands into BV bands of Johnson-Cousins photometric system and built the color magnitude diagram…
We present explicit expressions for the calculation of cosmological look back time, for zero cosmological constant and arbitrary density parameter $\Omega$, which, in the limit as redshift becomes infinite, give the age of the universe. The…
Age is one of the most fundamental parameters of stars, yet it is one of the hardest to determine as it requires modelling various aspects of stellar formation and evolution. When we compare the ages derived from isochronal and dynamical…
We present preliminary results from our on-going survey of Galactic globular clusters relative ages. The investigation is based on V,I images obtained at the ESO and La Palma telescopes, which make up the largest homogenous photometric…
This paper addresses the questions of what we have learned about how and when dense star clusters form, and what studies of star clusters have revealed about galaxy formation and evolution. One important observation is that globular…
Globular clusters are among the first objects used to establish the distance scale of the Universe. In the 1970-ies it has been recognized that the differential magnitude distribution of old globular clusters is very similar in different…
In this contribution I will discuss fundamental stellar parameters as determined from young star clusters; specifically those with ages less than or approximately equal to that of the Pleiades. I will focus primarily on the use of stellar…
Recent observations of r-nuclei, and in particular of Th, in ultra-metal poor stars revived the old idea that the Th cosmochronometry could provide an age estimate of the oldest stars in the Galaxy, and therefore a lower limit to the age of…
Their ubiquity and extreme densities make star clusters probes of prime importance of galaxy evolution. Old globular clusters keep imprints of the physical conditions of their assembly in the early Universe, and younger stellar objects,…
An overview of our current understanding of the formation and evolution of star clusters is given, with main emphasis on high-mass clusters. Clusters form deeply embedded within dense clouds of molecular gas. Left-over gas is cleared within…
Based on an almost complete sample of Galactic open star clusters within 1.8 kpc, we perform a comprehensive statistical analysis of various cluster parameters like spatial position, age, size, mass and extinction in order to understand the…
The recent Gaia Data Release 1 of stellar parallaxes provides ample opportunity to find metal-poor main-sequence stars with precise parallaxes. We select 21 such stars with parallax uncertainties better than $\sigma_\pi/\pi\leq0.10$ and…
In order to answer this question, we combine ten independent astrophysical constraints in the space of the density parameters $\Omega_m$ of gravitating matter and $\Omega_{\Lambda}$ of vacuum energy. We find that $\Omega_m=0.31\pm 0.07$,…
Many dark energy models fail to pass the cosmic age test. In this paper, we investigate the cosmic age problem associated with nine extremely old Global Clusters (GCs) and the old quasar APM $08279+5255$ in the $R_h=ct$ Universe. The age…
Globular clusters are large and dense agglomerate of stars. At variance with smaller clusters of stars, they exhibit signs of some chemical evolution. At least for this reason, they are intermediate between open clusters and massive objects…
Young, massive star clusters are the most notable and significant end products of violent star-forming episodes triggered by galaxy collisions, mergers, and close encounters. The question remains, however, whether or not at least a fraction…
Nucleocosmochronology involves the use of the abundances of radioactive nuclear species and their radiogenic decay daughters to establish the finite age of the elements and the time scale for their formation. While there exist radioactive…