Introduction to Astrophysics, Lecture 13
... The spiral structure is not that well understood. Stars nearer the centre orbit much more quickly, so the arms should `wind up’. It is thought that instead the spiral structure is due to a density wave propagating around the galaxy. ...
... The spiral structure is not that well understood. Stars nearer the centre orbit much more quickly, so the arms should `wind up’. It is thought that instead the spiral structure is due to a density wave propagating around the galaxy. ...
observational evidence for dark matter
... the Andromeda galaxy. Counter-intuitively, the rotational velocity of the stars in the disc did not drop at larger radii as expected, but seemed to keep more or less level. It wasn’t until the 1970’s that this ubiquity of this general behaviour was confirmed, mainly due to the systematic study of di ...
... the Andromeda galaxy. Counter-intuitively, the rotational velocity of the stars in the disc did not drop at larger radii as expected, but seemed to keep more or less level. It wasn’t until the 1970’s that this ubiquity of this general behaviour was confirmed, mainly due to the systematic study of di ...
May 2015 - Hermanus Astronomy
... of the most comprehensive multi-observatory galaxy surveys yet, astronomers find that galaxies like our Milky Way underwent a stellar ‘baby boom’, churning out stars at a prodigious rate, about 30 times faster than today. Our Sun, however, is a late ‘boomer’. The Milky Way’s star-birthing frenzy pea ...
... of the most comprehensive multi-observatory galaxy surveys yet, astronomers find that galaxies like our Milky Way underwent a stellar ‘baby boom’, churning out stars at a prodigious rate, about 30 times faster than today. Our Sun, however, is a late ‘boomer’. The Milky Way’s star-birthing frenzy pea ...
Dark and baryonic matter in the MareNostrum Universe
... The nonlinear evolution of structures has been followed by the GADGET II code of V. Springel [? ]. For the gravitational evolution we have used the TREEPM algorithm on a homogeneous Eulerian grid to compute large scale forces by the Particle-Mesh algorithm. In this simulation we employed 10243 mesh ...
... The nonlinear evolution of structures has been followed by the GADGET II code of V. Springel [? ]. For the gravitational evolution we have used the TREEPM algorithm on a homogeneous Eulerian grid to compute large scale forces by the Particle-Mesh algorithm. In this simulation we employed 10243 mesh ...
dark matter effective field theories in stars
... resulted in solid evidence, not only at astrophysical scales, but also cosmological, which leave no doubt that our universe is mainly populated by a still undetected non-interactive type of matter, the so-called dark matter, ofwhich thenature is still unknown. Among the numerous theories devised t ...
... resulted in solid evidence, not only at astrophysical scales, but also cosmological, which leave no doubt that our universe is mainly populated by a still undetected non-interactive type of matter, the so-called dark matter, ofwhich thenature is still unknown. Among the numerous theories devised t ...
Simulating Gravity: Dark Matter and Gravitational Lensing
... In conflict with this expectation, astronwhich can only be detected through its gravitational influomers observe that, outside the luminous center, the rotation ence. Astronomers know dark matter must be present in galspeed of stars is approximately constant as a function of their axies because the ...
... In conflict with this expectation, astronwhich can only be detected through its gravitational influomers observe that, outside the luminous center, the rotation ence. Astronomers know dark matter must be present in galspeed of stars is approximately constant as a function of their axies because the ...
Ch. 13 GALAXIES
... 4. 3rd: _________ Galaxy, M ___ B. _______ Cluster: ~ 2500 galaxies IV. Galaxy Collisions A. Larger galaxies may “absorb” smaller galaxies in a process called galactic ____________! B. Large spiral galaxies may collide ...
... 4. 3rd: _________ Galaxy, M ___ B. _______ Cluster: ~ 2500 galaxies IV. Galaxy Collisions A. Larger galaxies may “absorb” smaller galaxies in a process called galactic ____________! B. Large spiral galaxies may collide ...
All About MACHO
... dence comes from the speeds of stars and hydrogen gas clouds moving in spiral galaxies. These speeds, accurately measured using the Doppler effect, are much faster than can be explained if only the gravity from observed stars, gas, and dust is taken into account. Especially in the outer reaches of s ...
... dence comes from the speeds of stars and hydrogen gas clouds moving in spiral galaxies. These speeds, accurately measured using the Doppler effect, are much faster than can be explained if only the gravity from observed stars, gas, and dust is taken into account. Especially in the outer reaches of s ...
the physical vacuum and gravity.
... gravity occurs. Thus Newton's formula would be fair for those bodies whose density is less than the specified number, and will not at high densities of cosmic bodies they represent an impenetrable screen for physical vacuum and no gravity. This means that in the center of spiral galaxies, including ...
... gravity occurs. Thus Newton's formula would be fair for those bodies whose density is less than the specified number, and will not at high densities of cosmic bodies they represent an impenetrable screen for physical vacuum and no gravity. This means that in the center of spiral galaxies, including ...
Cardassian Expansion - University of Michigan
... Light elements are made: Helium, Deterium, Lithium are made three minutes after the Big Bang Getting the right abundances of these elements implies a universe that is made of only 4% ordinary atoms! Heavy elements are made much later, in stars ...
... Light elements are made: Helium, Deterium, Lithium are made three minutes after the Big Bang Getting the right abundances of these elements implies a universe that is made of only 4% ordinary atoms! Heavy elements are made much later, in stars ...
1 Dark matter and dark energy comprise over 90% of the Universe
... necessary to keep the objects together. This missing mass is therefore referred to as dark matter (Martin). The search for dark matter using gravitational lensing provides the backdrop to explanations to what dark matter is and why it is important. The nature of dark matter has intrigued astronomers ...
... necessary to keep the objects together. This missing mass is therefore referred to as dark matter (Martin). The search for dark matter using gravitational lensing provides the backdrop to explanations to what dark matter is and why it is important. The nature of dark matter has intrigued astronomers ...
Dark matter
Dark matter is a hypothetical kind of matter that cannot be seen with telescopes but would account for most of the matter in the universe. The existence and properties of dark matter are inferred from its gravitational effects on visible matter, on radiation, and on the large-scale structure of the universe. Dark matter has not been detected directly, making it one of the greatest mysteries in modern astrophysics.Dark matter neither emits nor absorbs light or any other electromagnetic radiation at any significant level. According to the Planck mission team, and based on the standard model of cosmology, the total mass–energy of the known universe contains 4.9% ordinary matter, 26.8% dark matter and 68.3% dark energy. Thus, dark matter is estimated to constitute 84.5% of the total matter in the universe, while dark energy plus dark matter constitute 95.1% of the total mass–energy content of the universe.Astrophysicists hypothesized the existence of dark matter to account for discrepancies between the mass of large astronomical objects determined from their gravitational effects, and their mass as calculated from the observable matter (stars, gas, and dust) that they can be seen to contain. Their gravitational effects suggest that their masses are much greater than the observable matter survey suggests. Dark matter was postulated by Jan Oort in 1932, albeit based upon insufficient evidence, to account for the orbital velocities of stars in the Milky Way. In 1933, Fritz Zwicky was the first to use the virial theorem to infer the existence of unseen matter, which he referred to as dunkle Materie 'dark matter'. More robust evidence from galaxy rotation curves was discovered by Horace W. Babcock in 1939, but was not attributed to dark matter. The first hypothesis to postulate ""dark matter"" based upon robust evidence was formulated by Vera Rubin and Kent Ford in the 1960s–1970s, using galaxy rotation curves. Subsequently, many other observations have indicated the presence of dark matter in the universe, including gravitational lensing of background objects by galaxy clusters such as the Bullet Cluster, the temperature distribution of hot gas in galaxies and clusters of galaxies and, more recently, the pattern of anisotropies in the cosmic microwave background. According to consensus among cosmologists, dark matter is composed primarily of a not yet characterized type of subatomic particle.The search for this particle, by a variety of means, is one of the major efforts in particle physics today.Although the existence of dark matter is generally accepted by the mainstream scientific community, some alternative theories of gravity have been proposed, such as MOND and TeVeS, which try to account for the anomalous observations without requiring additional matter. However, these theories cannot account for the properties of galaxy clusters.