scholarly journals THE CHEMICAL SIGNATURES OF THE FIRST STAR CLUSTERS IN THE UNIVERSE

2010 ◽  
Vol 721 (1) ◽  
pp. 582-596 ◽  
Author(s):  
Joss Bland-Hawthorn ◽  
Torgny Karlsson ◽  
Sanjib Sharma ◽  
Mark Krumholz ◽  
Joe Silk
Keyword(s):  
Star Clusters ◽  
Chemical Signatures ◽  
The Universe

scholarly journals Modeling of Integrated Spectral Energy Distributions of Stellar Populations with Various Binary Fractions

2021 ◽  
Vol 2068 (1) ◽  
pp. 012048
Author(s):  
Zhongmu Li ◽  
Chen Yan
Keyword(s):  
Binary Stars ◽  
Star Clusters ◽  
Stellar Populations ◽  
Spectral Studies ◽  
Spectral Energy ◽  
Spectral Energy Distributions ◽  
Energy Distributions ◽  
Spectral Fitting ◽  
The Universe

Abstract Binary stars are common in the universe, but binary fractions are various in different star clusters and galaxies. Studies have shown that binary fraction affects the integrated spectral energy distributions obviously, in particular in the UV band. It affects spectral fitting of many star clusters and galaxies significantly. However, previous works usually take a fixed binary fraction, i.e., 0.5, and this is far from getting accurate results. Therefore, it is important to model the integrated spectral energy distributions of stellar populations with various binary fractions. This work presents a modeling of spectral energy distributions of simple stellar populations with binary fractions of 0.3, 0.7, and 1.0. The results are useful for different kinds of spectral studies.

3. Stars

2016 ◽  
pp. 22-49
Author(s):  
James Binney
Keyword(s):  
Star Formation ◽  
20Th Century ◽  
Binary Stars ◽  
Star Clusters ◽  
Solar Neutrinos ◽  
Interstellar Gas ◽  
Stellar Seismology ◽  
Stellar Masses ◽  
Century Science ◽  
The Universe

Most of what we know about the Universe has been gleaned from the study of stars, and a major achievement of 20th-century science was to understand how stars work and their lifecycles from birth to death. ‘Stars’ describes this lifecycle beginning with star formation when a cloud of interstellar gas suffers a runaway of its central density. It then considers nuclear fusion, key stellar masses, and life after the main sequence when the star burns its core helium. The surfaces of stars are described along with stellar coronae and exploding stars—both core-collapse and deflagration supernovae. Finally, globular star clusters, solar neutrinos, stellar seismology, and binary stars are discussed.

Allan Rex Sandage. 18 June 1926 — 13 November 2010

2012 ◽  
Vol 58 ◽  
pp. 245-264 ◽  
Author(s):  
Donald Lynden-Bell ◽  
François Schweizer
Keyword(s):  
Stellar Evolution ◽  
Star Clusters ◽  
Optical Telescope ◽  
Elemental Abundances ◽  
Mount Wilson Observatory ◽  
History Of ◽  
Expansion Of The Universe ◽  
Edwin Hubble ◽  
Number Counts ◽  
The Universe

Allan Sandage was an observational astronomer who was happiest at a telescope. On the sudden death of Edwin Hubble, Sandage inherited the programmes using the world’s largest optical telescope at Palomar to determine the distances and number counts of galaxies. Over many years he greatly revised the distance scale and, on reworking Hubble’s analysis, discovered the error that had led Hubble to doubt the interpretation of the galaxies’ redshifts as an expansion of the Universe. Sandage showed that there was a consistent age of creation for the stars, the elements and the cosmos. Through work with Baade and Schwarzschild he discovered the key to the interpretation of the colour–magnitude diagrams of star clusters in terms of stellar evolution. With others he founded galactic archaeology, interpreting the motions and elemental abundances of the oldest stars in terms of a model for the Galaxy’s formation. He published several fine atlases and catalogues of galaxies and a definitive history of the Mount Wilson Observatory.

scholarly journals Compact Nuclei of Galaxies and Sources of Their Energy

1999 ◽  
Vol 194 ◽  
pp. 323-323
Author(s):  
L.Sh. Grigoryan ◽  
G.S. Sahakian
Keyword(s):  
Equation Of State ◽  
Star Clusters ◽  
Galactic Nuclei ◽  
Star Cluster ◽  
Statistical Equilibrium ◽  
Spherically Symmetric ◽  
Symmetric Star ◽  
Age Of The Universe ◽  
The Universe

A model of compact nuclei of galaxies as spherically-symmetric star clusters is proposed. A concept of the equation of state for star clusters in statistical equilibrium is introduced (galactic nuclei are systems in statistical equilibrium if their age is of the order of the age of the Universe). It is shown that a statistically equilibrium star cluster is described by the equation of state of a polytrope P = aρ3, and with its help the main parameters of compact nuclei of galaxies are calculated. The formula M = 2.524GR5/a for mass M and radius R of the cluster is derived.

scholarly journals Byurakan Astrophysical Observatory: 75 years of outstanding achievements

2021 ◽  
pp. 1-11
Author(s):  
A. M. Mickaelian
Keyword(s):  
Soviet Union ◽  
Nobel Prize ◽  
Star Clusters ◽  
Byurakan Astrophysical Observatory ◽  
Outstanding Scientist ◽  
The Soviet Union ◽  
The World ◽  
House Museum ◽  
Important People ◽  
The Universe

The Byurakan Astrophysical Observatory (BAO) is one of the most famous observatories of the Soviet Union and may be of the world. It was founded in 1946 by the outstanding scientist Viktor Ambartsumian (1908-1996) and became the leader of studies on instability phenomena in the Universe. Many discoveries have been carried out at BAO related to stars, star clusters and other systems, nebulae, galaxies and systems of galaxies. BAO has two major instruments; 1m Schmidt and 2.6m classical telescopes. Together with V. Ambartsumian, outstanding scientists Beniamin Markarian, Grigor Gurzadyan, Marat Arakelian and others have worked at BAO. Many important international meetings and schools for young astronomers have been held. Many important people, including State authorities, Nobel Prize Winners and others have visited BAO. BAO has statuses of RA National Value, Regional Astronomical Centre, it has UNESCO Documentary Heritage item, its garden is recognized as Dendrarium, and there is RA National Hero Viktor Ambartsumian's house-museum.

scholarly journals Nuclear Star Clusters

2015 ◽  
Vol 12 (S316) ◽  
pp. 84-90 ◽  
Author(s):  
Nadine Neumayer
Keyword(s):  
Star Clusters ◽  
Elliptical Galaxies ◽  
Formation Mechanisms ◽  
Strong Function ◽  
Massive Black Holes ◽  
Nearby Galaxies ◽  
Dwarf Elliptical Galaxies ◽  
Galaxy Masses ◽  
The Universe

AbstractThe centers of galaxies host two distinct, compact components: massive black holes and nuclear star clusters. Nuclear star clusters are the densest stellar systems in the universe, with masses of ~ 107M⊙and sizes of ~ 5pc. They are almost ubiquitous at the centres of nearby galaxies with masses similar to, or lower than the Milky Way. Their occurrence both in spirals and dwarf elliptical galaxies appears to be a strong function of total galaxy light or mass. Nucleation fractions are up to 100% for total galaxy magnitudes of MB= −19mag or total galaxy luminosities of about LB= 1010L⊙and falling nucleation fractions for both smaller and higher galaxy masses. Although nuclear star clusters are so common, their formation mechanisms are still under debate. The two main formation scenarios proposed are the infall and subsequent merging of star clusters and the in-situ formation of stars at the center of a galaxy. Here, I review the state-of-the-art of nuclear star cluster observations concerning their structure, stellar populations and kinematics. These observations are used to constrain the proposed formation scenarios for nuclear star clusters. Constraints from observations show, that likely both cluster infall and in-situ star formation are at work. The relative importance of these two mechanisms is still subject of investigation.

scholarly journals The relation between stellar evolution and cosmology

1984 ◽  
Vol 105 ◽  
pp. 549-562
Author(s):  
R. J. Tayler
Keyword(s):  
Original Composition ◽  
Chemical Composition ◽  
Stellar Evolution ◽  
Star Clusters ◽  
A Value ◽  
Cosmological Observations ◽  
Important Interaction ◽  
Age Of The Universe ◽  
The Universe

Observations of star clusters combined with the theory of stellar evolution enable us to estimate the ages of stars while cosmological observations and theories give us a value for the age of the Universe. This is the most important interaction between cosmology and stellar evolution because it is clearly necessary that stars are younger than the Universe. Stellar evolution also plays an important rôle in relating the present chemical composition of the Universe to its original composition.

scholarly journals The limits of cosmology: role of the Moon

2020 ◽  
Vol 379 (2188) ◽  
pp. 20190561 ◽  
Author(s):  
Joseph Silk
Keyword(s):  
Galaxy Formation ◽  
Star Clusters ◽  
Far Infrared ◽  
Big Bang ◽  
Habitable Zone ◽  
The Moon ◽  
The Big Bang ◽  
The Universe ◽  
Infrared Telescopes

The lunar surface allows a unique way forward in cosmology, to go beyond current limits. The far side provides an unexcelled radio-quiet environment for probing the dark ages via 21 cm interferometry to seek elusive clues on the nature of the infinitesimal fluctuations that seeded galaxy formation. Far-infrared telescopes in cold and dark lunar polar craters will probe back to the first months of the Big Bang and study associated spectral distortions in the CMB. Optical and IR megatelescopes will image the first star clusters in the Universe and seek biosignatures in the atmospheres of unprecedented numbers of nearby habitable zone exoplanets. The goals are compelling and a stable lunar platform will enable construction of telescopes that can access trillions of modes in the sky, providing the key to exploration of our cosmic origins. This article is part of a discussion meeting issue ‘Astronomy from the Moon: the next decades’.

scholarly journals The effects of a background potential in star cluster evolution

2020 ◽  
Vol 639 ◽  
pp. A92 ◽  
Author(s):  
B. Reinoso ◽  
D. R. G. Schleicher ◽  
M. Fellhauer ◽  
N. W. C. Leigh ◽  
R. S. Klessen
Keyword(s):  
Binary Stars ◽  
Gravitational Force ◽  
Massive Star ◽  
Star Clusters ◽  
Star Cluster ◽  
Early Evolution ◽  
Relaxation Processes ◽  
Blue Stragglers ◽  
Stellar Collisions ◽  
The Universe

Runaway stellar collisions in dense star clusters are invoked to explain the presence of very massive stars or blue stragglers in the center of those systems. This process has also been explored for the first star clusters in the Universe and shown to yield stars that may collapse at some points into an intermediate mass black hole. Although the early evolution of star clusters requires the explicit modeling of the gas out of which the stars form, these calculations would be extremely time-consuming and often the effects of the gas can be accurately treated by including a background potential to account for the extra gravitational force. We apply this approximation to model the early evolution of the first dense star clusters formed in the Universe by performing N-body simulations, our goal is to understand how the additional gravitational force affects the growth of a very massive star through stellar mergers in the central parts of the star cluster. Our results show that the background potential increases the velocities of the stars, causing an overall delay in the evolution of the clusters and in the runaway growth of a massive star at the center. The population of binary stars is lower due to the increased kinetic energy of the stars, initially reducing the number of stellar collisions, and we show that relaxation processes are also affected. Despite these effects, the external potential enhances the mass of the merger product by a factor ∼2 if the collisions are maintained for long times.

scholarly journals Contribution of globular clusters to halos

2015 ◽  
Vol 12 (S316) ◽  
pp. 287-293
Author(s):  
Angela Bragaglia
Keyword(s):  
Star Formation ◽  
Formation Mechanism ◽  
Globular Clusters ◽  
Massive Star ◽  
Milky Way ◽  
Star Clusters ◽  
Early Evolution ◽  
Light Elements ◽  
Halo Stars ◽  
Chemical Signatures

AbstractThe contribution of massive star clusters to their hosting halo dramatically depends on their formation mechanism and their early evolution. Massive globular clusters in the Milky Way (and in other galaxies) have been shown to display peculiar chemical patterns (light-elements correlations and anti-correlations) indicative of a complex star formation, confirmed by photometric evidence (spread or split sequences). I use these chemical signatures to try to understand what is the fraction of halo stars originally born in globular clusters.

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