The composition and nature of the dust shell surrounding the binary
... Low- and intermediate-mass stars (up to 8 M ) will lose a significant amount of their initial mass on the Asymptotic Giant Branch (AGB). More massive stars will lose their hydrogen-rich envelopes during a red supergiant (RSG) phase. The mass-loss rates can be as high as 10−4 M /yr for the low-mass ...
... Low- and intermediate-mass stars (up to 8 M ) will lose a significant amount of their initial mass on the Asymptotic Giant Branch (AGB). More massive stars will lose their hydrogen-rich envelopes during a red supergiant (RSG) phase. The mass-loss rates can be as high as 10−4 M /yr for the low-mass ...
Stellarium User Guide - Skolekonsulenterne.dk
... Stellarium may be used as an educational tool for teaching about the night sky, as an observational aide for amateur astronomers wishing to plan a night’s observing, or simply as a curiosity (it’s fun!). Because of the high quality of the graphics that Stellarium produces, it is used in some real pl ...
... Stellarium may be used as an educational tool for teaching about the night sky, as an observational aide for amateur astronomers wishing to plan a night’s observing, or simply as a curiosity (it’s fun!). Because of the high quality of the graphics that Stellarium produces, it is used in some real pl ...
Insights into thermonuclear supernovae from the incomplete Si
... An alternative way to gain knowledge about the chemical structure of the ejecta is through studying young supernova remnants (Badenes 2010). Badenes et al. (2008) studied the relationship between X-ray spectral features due to Mn and Cr in young SNIa remnants and the metallicity of the WD progenitor ...
... An alternative way to gain knowledge about the chemical structure of the ejecta is through studying young supernova remnants (Badenes 2010). Badenes et al. (2008) studied the relationship between X-ray spectral features due to Mn and Cr in young SNIa remnants and the metallicity of the WD progenitor ...
Magnetars: properties, origin and evolution
... powerful short bursts which often reach super-Eddington luminosities. More rarely, they also emit intermediate and giant flares, the latter involving the release of up to about 1046 erg in less than half a second. Magnetars also show pulsed X-ray emission with typical luminosity of ∼ 1035 erg s−1 in ...
... powerful short bursts which often reach super-Eddington luminosities. More rarely, they also emit intermediate and giant flares, the latter involving the release of up to about 1046 erg in less than half a second. Magnetars also show pulsed X-ray emission with typical luminosity of ∼ 1035 erg s−1 in ...
The Formation of a Realistic Disk Galaxy in Lambda Dominated
... feedback and a redshift-dependent UV background. We compare results from a cold dark matter (CDM) simulation to a warm dark matter (WDM) (2 keV) simulation that forms significantly less small-scale structure. We show how high mass and force resolution in both the gas and dark-matter components ...
... feedback and a redshift-dependent UV background. We compare results from a cold dark matter (CDM) simulation to a warm dark matter (WDM) (2 keV) simulation that forms significantly less small-scale structure. We show how high mass and force resolution in both the gas and dark-matter components ...
ULTRA-COMPACT HII REGIONS AND MASSIVE STAR FORMATION
... when resolved. This observationally based definition of HCs is broad enough to apply to any hot, dust/molecular gas–enshrouded object such as UC HII regions, evolved hot stars that have moved into a dense molecular cloud, or massive protostars still undergoing rapid accretion. In this section, I con ...
... when resolved. This observationally based definition of HCs is broad enough to apply to any hot, dust/molecular gas–enshrouded object such as UC HII regions, evolved hot stars that have moved into a dense molecular cloud, or massive protostars still undergoing rapid accretion. In this section, I con ...
A Legacy Study of Stellar Life Cycles in the Galactic Center
... • Unusual for an XRB to be in outburst for so long (Chen et al. 1997). • Microquasars and some pulsars might have required luminosity and hard spectrum in high state • Fluorescent line seen in Sgr B2, Sgr C, and central parsecs of Galaxy, so would need multiple microquasars, such as GRS 1915+10, but ...
... • Unusual for an XRB to be in outburst for so long (Chen et al. 1997). • Microquasars and some pulsars might have required luminosity and hard spectrum in high state • Fluorescent line seen in Sgr B2, Sgr C, and central parsecs of Galaxy, so would need multiple microquasars, such as GRS 1915+10, but ...
A New Science Strategy for Space Astronomy and Astrophysics
... next decade,1 prepared by a committee under the leadership of John Bahcall. Like previous decadal studies in this field, the report identified in priority order the most important scientific programs and projects for both groundand space-based research. It recommended a single large initiative for s ...
... next decade,1 prepared by a committee under the leadership of John Bahcall. Like previous decadal studies in this field, the report identified in priority order the most important scientific programs and projects for both groundand space-based research. It recommended a single large initiative for s ...
Magnetic collapse of a neutron gas: Can magnetars
... approach. These authors present several physical mechanisms for its origin in both extremely low and very high density systems, which may include astrophysical compact objects. In the case of highly dense systems, it was pointed out that “exotic” phase transitions could occur during gravitational co ...
... approach. These authors present several physical mechanisms for its origin in both extremely low and very high density systems, which may include astrophysical compact objects. In the case of highly dense systems, it was pointed out that “exotic” phase transitions could occur during gravitational co ...
I Introduction to the Interstellar Medium
... The first observational evidence that there was a general ISM that pervaded the space between the stars came from photographic spectroscopy of spectroscopic binary stars early in the 20th century. It was noticed that in addition to the relatively broad absorption lines associated with the atmosphere ...
... The first observational evidence that there was a general ISM that pervaded the space between the stars came from photographic spectroscopy of spectroscopic binary stars early in the 20th century. It was noticed that in addition to the relatively broad absorption lines associated with the atmosphere ...
The Kuiper Belt Explored by Serendipitous Stellar Occultations
... The characteristic scale of the Fresnel diffraction effect (i.e., roughly speaking, the broadening of the object shadow) is the so-called Fresnel scale Fs = (λD/2) (Warner, 1988). [Note that some authors give different definitions for the Fresnel scale: (λD/2π) , (λD) , or (λD)/2 .] The Fresnel scal ...
... The characteristic scale of the Fresnel diffraction effect (i.e., roughly speaking, the broadening of the object shadow) is the so-called Fresnel scale Fs = (λD/2) (Warner, 1988). [Note that some authors give different definitions for the Fresnel scale: (λD/2π) , (λD) , or (λD)/2 .] The Fresnel scal ...
The Ionized Nebula surrounding the Red Supergiant W26 in
... line spectrum (Levesque et al. 2009). This is all consistent with W26 being a very evolved RSG with a greater level of instability and higher mass-loss rate than typical RSGs. Ionized nebulae have never previously been resolved around RSGs as their photospheres are too cool to produce ionizing photo ...
... line spectrum (Levesque et al. 2009). This is all consistent with W26 being a very evolved RSG with a greater level of instability and higher mass-loss rate than typical RSGs. Ionized nebulae have never previously been resolved around RSGs as their photospheres are too cool to produce ionizing photo ...
Stellar evolution
Stellar evolution is the process by which a star changes during its lifetime. Depending on the mass of the star, this lifetime ranges from a few million years for the most massive to trillions of years for the least massive, which is considerably longer than the age of the universe. The table shows the lifetimes of stars as a function of their masses. All stars are born from collapsing clouds of gas and dust, often called nebulae or molecular clouds. Over the course of millions of years, these protostars settle down into a state of equilibrium, becoming what is known as a main-sequence star.Nuclear fusion powers a star for most of its life. Initially the energy is generated by the fusion of hydrogen atoms at the core of the main-sequence star. Later, as the preponderance of atoms at the core becomes helium, stars like the Sun begin to fuse hydrogen along a spherical shell surrounding the core. This process causes the star to gradually grow in size, passing through the subgiant stage until it reaches the red giant phase. Stars with at least half the mass of the Sun can also begin to generate energy through the fusion of helium at their core, whereas more-massive stars can fuse heavier elements along a series of concentric shells. Once a star like the Sun has exhausted its nuclear fuel, its core collapses into a dense white dwarf and the outer layers are expelled as a planetary nebula. Stars with around ten or more times the mass of the Sun can explode in a supernova as their inert iron cores collapse into an extremely dense neutron star or black hole. Although the universe is not old enough for any of the smallest red dwarfs to have reached the end of their lives, stellar models suggest they will slowly become brighter and hotter before running out of hydrogen fuel and becoming low-mass white dwarfs.Stellar evolution is not studied by observing the life of a single star, as most stellar changes occur too slowly to be detected, even over many centuries. Instead, astrophysicists come to understand how stars evolve by observing numerous stars at various points in their lifetime, and by simulating stellar structure using computer models.In June 2015, astronomers reported evidence for Population III stars in the Cosmos Redshift 7 galaxy at z = 6.60. Such stars are likely to have existed in the very early universe (i.e., at high redshift), and may have started the production of chemical elements heavier than hydrogen that are needed for the later formation of planets and life as we know it.