L43 THE STARFISH TWINS: TWO YOUNG
... survey of young planetary nebulae (PNs) selected on the basis of their low-excitation characteristics. The two objects show a highly aspherical morphology, characterized by multiple lobes distributed around the central star. Such a morphology has never been seen before in any astrophysical setting. ...
... survey of young planetary nebulae (PNs) selected on the basis of their low-excitation characteristics. The two objects show a highly aspherical morphology, characterized by multiple lobes distributed around the central star. Such a morphology has never been seen before in any astrophysical setting. ...
6th Grade The Theoretical Beginning of the Universe / Big Bang
... Just like with many ideas in Science, there are people who are critical of the Big Bang. The idea that there was a "Big Bang" is a theory . This means that it can not completely be assumed to be fact, but it has not yet been ...
... Just like with many ideas in Science, there are people who are critical of the Big Bang. The idea that there was a "Big Bang" is a theory . This means that it can not completely be assumed to be fact, but it has not yet been ...
lecture24
... times more massive than Milky Way) and a few Mpc (Mega parsecs) across, to dwarf ellipticals with a few million solar masses and 1 kpc across. There are about 10 times as many dwarf ellipticals as giants. Elliptical galaxies are labelled E1, E2, … E7, according to their eccentricity (departure from ...
... times more massive than Milky Way) and a few Mpc (Mega parsecs) across, to dwarf ellipticals with a few million solar masses and 1 kpc across. There are about 10 times as many dwarf ellipticals as giants. Elliptical galaxies are labelled E1, E2, … E7, according to their eccentricity (departure from ...
galaxy evolution
... within 1 billion years, these regions began to contract into protogalactic clouds. • Many galaxies form from the merger of several protogalactic clouds. ...
... within 1 billion years, these regions began to contract into protogalactic clouds. • Many galaxies form from the merger of several protogalactic clouds. ...
Spectral Fingerprints of Earth-like Planets Around FGK Stars
... For an Earth-like biosphere, the main detectable atmospheric chemical signatures that, in combination, could indicate habitability are O2/O3 with CH4/N2O, and CH3Cl. Note that one spectral feature, for example, O2, does not constitute a biosignature by itself, as the planetary context (like bulk pla ...
... For an Earth-like biosphere, the main detectable atmospheric chemical signatures that, in combination, could indicate habitability are O2/O3 with CH4/N2O, and CH3Cl. Note that one spectral feature, for example, O2, does not constitute a biosignature by itself, as the planetary context (like bulk pla ...
THREE Li-RICH K GIANTS - Indian Institute of Astrophysics
... Stellar parameters Teff , log g, and [Fe/ H] were obtained from the spectra by a standard procedure using ATLAS model atmospheres computed using the ‘‘no convective overshoot’’ option (see Robert L. Kurucz’s Web site2). The effective temperature (Teff) was obtained from the requirement that all Fe i ...
... Stellar parameters Teff , log g, and [Fe/ H] were obtained from the spectra by a standard procedure using ATLAS model atmospheres computed using the ‘‘no convective overshoot’’ option (see Robert L. Kurucz’s Web site2). The effective temperature (Teff) was obtained from the requirement that all Fe i ...
1 Cosmology: a brief refresher course
... there are still too many extremely high energy photons around, and these photodisintegrate any heavy nuclei that form. As the Universe expands and cools, however, the number density of these photons falls off exponentially, and once the temperature is kT ' 80 keV, heavier nuclei start to form in abu ...
... there are still too many extremely high energy photons around, and these photodisintegrate any heavy nuclei that form. As the Universe expands and cools, however, the number density of these photons falls off exponentially, and once the temperature is kT ' 80 keV, heavier nuclei start to form in abu ...
Formation of low-mass helium white dwarfs
... and low magnetic fields. These neutron stars are believed to be the end-product of binary evolution, in which an old neutron star accretes matter and angular momentum from a close stellar companion for an extended period of time, while being observable as an X-ray binary. During this evolutionary ph ...
... and low magnetic fields. These neutron stars are believed to be the end-product of binary evolution, in which an old neutron star accretes matter and angular momentum from a close stellar companion for an extended period of time, while being observable as an X-ray binary. During this evolutionary ph ...
An atlas of 2.4 to 4.1 mu m ISO/SWS spectra of early - UvA-DARE
... becomes too high to observe the embedded stars. The IR emission of the warm dust cocoon covering the newly formed massive stars in UCHii regions peaks typically at about 100 µm. At wavelengths longwards of 5–10 µm, the thermal emission of the dust dominates the photospheric flux, and can be as much ...
... becomes too high to observe the embedded stars. The IR emission of the warm dust cocoon covering the newly formed massive stars in UCHii regions peaks typically at about 100 µm. At wavelengths longwards of 5–10 µm, the thermal emission of the dust dominates the photospheric flux, and can be as much ...
The Central Star Candidate of the Planetary Nebula Sh2
... 68.101 ± 0.010 days, and that the lightcurve minima flatten occasionally. Mikulášek et al. (2007) also noted pronounced spectral variations between two spectra, taken at different brightness phases. A detailed model for the central star as the progenitor of the collimated bipolar nebula was sugges ...
... 68.101 ± 0.010 days, and that the lightcurve minima flatten occasionally. Mikulášek et al. (2007) also noted pronounced spectral variations between two spectra, taken at different brightness phases. A detailed model for the central star as the progenitor of the collimated bipolar nebula was sugges ...
McDonald I....Tisserand, P. et al ExELS an
... approach, based on version 1106 of the Besanc¸on population synthesis Galaxy model (Robin et al. 2003), which incorporates a three-dimensional dust model to compute extinction and reddening (Marshall et al. 2005). The populations included in the model are such that stars are limited to between 0.08 ...
... approach, based on version 1106 of the Besanc¸on population synthesis Galaxy model (Robin et al. 2003), which incorporates a three-dimensional dust model to compute extinction and reddening (Marshall et al. 2005). The populations included in the model are such that stars are limited to between 0.08 ...
IOSR Journal of Mathematics (IOSR-JM)
... of dynamical gravitational collapse. In the mean time, many authors have studied mainly spherical gravitational collapse of a massive matter cloud within the framework of general relativity. As the nuclear fuel of a massive star exhausts, it loses its equilibrium and gravity becomes the central domi ...
... of dynamical gravitational collapse. In the mean time, many authors have studied mainly spherical gravitational collapse of a massive matter cloud within the framework of general relativity. As the nuclear fuel of a massive star exhausts, it loses its equilibrium and gravity becomes the central domi ...
Feedback from winds and supernovae in massive stellar clusters – I
... That stellar winds play a significant role in stellar cluster feedback is apparent from the fact that many young (pre-SN) massive star-forming regions contain diffuse X-ray emission – the hot gas responsible can only have been created by winds. Observations reveal that the surrounding cold molecular ...
... That stellar winds play a significant role in stellar cluster feedback is apparent from the fact that many young (pre-SN) massive star-forming regions contain diffuse X-ray emission – the hot gas responsible can only have been created by winds. Observations reveal that the surrounding cold molecular ...
The secular evolution of the Kuiper belt after a close stellar encounter
... We show the effects of the perturbation caused by a passing by star on the Kuiper belt objects (KBOs) of our Solar System. The Kuiper belt is sampled using up to 131,072 bodies on nearly circular orbits distributed in a ring of surface density Σ ∼ r−2 . The dynamics of the KB is followed by direct N ...
... We show the effects of the perturbation caused by a passing by star on the Kuiper belt objects (KBOs) of our Solar System. The Kuiper belt is sampled using up to 131,072 bodies on nearly circular orbits distributed in a ring of surface density Σ ∼ r−2 . The dynamics of the KB is followed by direct N ...
Determination of the distance to the Andromeda Galaxy using variable stars U
... magnitude (known as period-luminosity relationship, Leavitt & Pickering, 1912). The Cepheid period-luminosity (P-L) relationship has made of these variable stars one of the main cornerstones in deriving extragalactic distances (see Freedman et al., 2001, for a review). The pulsation mechanism is rel ...
... magnitude (known as period-luminosity relationship, Leavitt & Pickering, 1912). The Cepheid period-luminosity (P-L) relationship has made of these variable stars one of the main cornerstones in deriving extragalactic distances (see Freedman et al., 2001, for a review). The pulsation mechanism is rel ...
The importance of radiative feedback for the stellar initial mass
... Whereas star formation in the barotropic simulations continued unabated until the simulations stopped, we find that radiative feedback, even from low-mass stars, were essentially terminates the production of new objects within low-mass dense molecular cloud cores after roughly one local dynamical ti ...
... Whereas star formation in the barotropic simulations continued unabated until the simulations stopped, we find that radiative feedback, even from low-mass stars, were essentially terminates the production of new objects within low-mass dense molecular cloud cores after roughly one local dynamical ti ...
The Formation and Evolution of Massive Black Holes - Ira-Inaf
... alternative view, the galaxy-regulated hypothesis, the galaxy sets the MBH mass by regulating the amount of gas that trickles to the MBH. One of the most interesting results that has recently emerged on black hole and galaxy growth is the strong link between the global black hole growth rate and the ...
... alternative view, the galaxy-regulated hypothesis, the galaxy sets the MBH mass by regulating the amount of gas that trickles to the MBH. One of the most interesting results that has recently emerged on black hole and galaxy growth is the strong link between the global black hole growth rate and the ...
The Lagoon Nebula and its Vicinity
... use M 8 to refer to the whole complex of stars, H II regions and molecular gas, and ‘Lagoon Nebula’ to be synonymous. The NE of the region is dominated by the open cluster, so NGC 6530 is now always used to refer to the cluster rather than any surrounding nebulosity. We take NGC 6533 to refer to the ...
... use M 8 to refer to the whole complex of stars, H II regions and molecular gas, and ‘Lagoon Nebula’ to be synonymous. The NE of the region is dominated by the open cluster, so NGC 6530 is now always used to refer to the cluster rather than any surrounding nebulosity. We take NGC 6533 to refer to the ...
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.