Astr604-Ch1
... A star can be defined as a body that satisfies two conditions: (a) it is bound by self-gravity; (b) it radiates energy supplied by an internal source. From the first condition it follows that the shape of such a body must be a spherical, for gravity is a spherical symmetric force field. Or, it might ...
... A star can be defined as a body that satisfies two conditions: (a) it is bound by self-gravity; (b) it radiates energy supplied by an internal source. From the first condition it follows that the shape of such a body must be a spherical, for gravity is a spherical symmetric force field. Or, it might ...
Basics about stars
... the pull of gravity. The Chandrasekhar limit prohibits WD‘s more massive than 1.44M • Neutron stars : Stars with initially up to 25M end their life as Neutron stars. A supernova Type II is associated with the formation of a neutron star • Black hole : For more massive stars even the neutron degene ...
... the pull of gravity. The Chandrasekhar limit prohibits WD‘s more massive than 1.44M • Neutron stars : Stars with initially up to 25M end their life as Neutron stars. A supernova Type II is associated with the formation of a neutron star • Black hole : For more massive stars even the neutron degene ...
14.1 Introduction - University of Cambridge
... ure 13.11) following the ejection of the star’s outer layers in the planetary nebula stage. In either case, without an internal source of energy, white dwarfs simply cool off at an essentially constant radius as they slowly deplete their supply of thermal energy. ...
... ure 13.11) following the ejection of the star’s outer layers in the planetary nebula stage. In either case, without an internal source of energy, white dwarfs simply cool off at an essentially constant radius as they slowly deplete their supply of thermal energy. ...
Lecture Eight (Powerpoint format) - Flash
... parent gas cloud (sometimes called a “molecular cloud core”) without turbulence or magnetic fields. Initially, before the star has formed, the parent gas cloud is a state of hydrostatic balance. ...
... parent gas cloud (sometimes called a “molecular cloud core”) without turbulence or magnetic fields. Initially, before the star has formed, the parent gas cloud is a state of hydrostatic balance. ...
Lec10_ch12_deathofstars
... Novas • Consider what happens to a white dwarf in a binary system – As the larger star evolves and expands some of its outer layers fall onto the white dwarf companion – What happens when the hydrogen layer becomes dense enough? • Hydrogen flash of fusion--a Nova occurs ...
... Novas • Consider what happens to a white dwarf in a binary system – As the larger star evolves and expands some of its outer layers fall onto the white dwarf companion – What happens when the hydrogen layer becomes dense enough? • Hydrogen flash of fusion--a Nova occurs ...
May 2017 - Museums Wellington
... celestial hemisphere and the 4th brightest in the night sky. Arcturus has a similar mass to the Sun, but has already expanded to become a red giant, with 25 times the diameter and 170 times the luminosity of our own star. When close to the horizon it often appears to twinkle red and green as its lig ...
... celestial hemisphere and the 4th brightest in the night sky. Arcturus has a similar mass to the Sun, but has already expanded to become a red giant, with 25 times the diameter and 170 times the luminosity of our own star. When close to the horizon it often appears to twinkle red and green as its lig ...
Problem Sheet for Introduction to Astrophysics
... a) If you could stand on the event horizon of a one-solar-mass black hole (M=1.991030 kg), what is the tidal force acting on you? (Assume your weight is 70kg and your height is 2 m) b) If you could stand on the event horizon of a 109 solar mass black hole, what is the tidal force acting on you (the ...
... a) If you could stand on the event horizon of a one-solar-mass black hole (M=1.991030 kg), what is the tidal force acting on you? (Assume your weight is 70kg and your height is 2 m) b) If you could stand on the event horizon of a 109 solar mass black hole, what is the tidal force acting on you (the ...
here - Lund Observatory
... year. One has measured a radial velocity of 1300 km/s for the nebular gas in relation to the central pulsar. We assume a symmetrical expansion. a. How far away is the crab nebula? b. How long ago did the supernova occur according to these measurements? c. How bright was it then, if a supernova of th ...
... year. One has measured a radial velocity of 1300 km/s for the nebular gas in relation to the central pulsar. We assume a symmetrical expansion. a. How far away is the crab nebula? b. How long ago did the supernova occur according to these measurements? c. How bright was it then, if a supernova of th ...
What is a white dwarf?
... mass to its companion. This mass exchange can then change the remaining life histories of both stars. • Sun ...
... mass to its companion. This mass exchange can then change the remaining life histories of both stars. • Sun ...
The Sun Like Star : HT Vir
... The light curves and data in the V band of HT Vir variable in the ASAS catalog have been taken into account (Pojmanski, 1997). The graphics according to the time (HJD) of the magnitudes (Vmag) is given in Figure1. The light curve according to phase of the stars is given in Figure2. The light curve c ...
... The light curves and data in the V band of HT Vir variable in the ASAS catalog have been taken into account (Pojmanski, 1997). The graphics according to the time (HJD) of the magnitudes (Vmag) is given in Figure1. The light curve according to phase of the stars is given in Figure2. The light curve c ...
The HR Diagram - Faculty Web Pages
... squeeze the gas all down to a single point, and radiation pressure, which wants to blast all the gas out to infinity. These two opposite forces balance out in a process called Hydrostatic Equilibrium, and keep the gas at a stable, fairly constant size. The radiation itself is due to the fusion of pr ...
... squeeze the gas all down to a single point, and radiation pressure, which wants to blast all the gas out to infinity. These two opposite forces balance out in a process called Hydrostatic Equilibrium, and keep the gas at a stable, fairly constant size. The radiation itself is due to the fusion of pr ...
What is a star?
... • Astronomers used telescopes see many stars that are too dim to see with the unaided eye. They added to the magnitude system. • Today, the brightest stars have a magnitude of about –2, and the faintest stars that we can see with a telescope have a magnitude of +30. • Dim stars have positive (larger ...
... • Astronomers used telescopes see many stars that are too dim to see with the unaided eye. They added to the magnitude system. • Today, the brightest stars have a magnitude of about –2, and the faintest stars that we can see with a telescope have a magnitude of +30. • Dim stars have positive (larger ...
part iv: stars i
... upper limit to the mass of stable stars. (In practice, instabilities cause a super-Eddington atmosphere to become clumpy, or `porous', and radiation is able to escape through paths of lowered optical depth between the clumps. Nevertheless, the Eddington limit represents a good approximation to the u ...
... upper limit to the mass of stable stars. (In practice, instabilities cause a super-Eddington atmosphere to become clumpy, or `porous', and radiation is able to escape through paths of lowered optical depth between the clumps. Nevertheless, the Eddington limit represents a good approximation to the u ...
L12 - QUB Astrophysics Research Centre
... We will see in next lectures what the implications of this are for other phenomena in the Universe. It actually led to the discovery of dark energy! The collapse of massive stars produces two types of remnants - neutron stars and black holes. Their masses have been measured in X-ray emitting binary ...
... We will see in next lectures what the implications of this are for other phenomena in the Universe. It actually led to the discovery of dark energy! The collapse of massive stars produces two types of remnants - neutron stars and black holes. Their masses have been measured in X-ray emitting binary ...
Source: https://www
... inside of this revised HZ near its inner edge, and Mars is just outside of the outer edge. When we studied stellar evolution, you saw the evolutionary tracks for stars in the HR diagram: stars do not maintain the same color and luminosity over their entire lifetimes. When the star begins stable hydr ...
... inside of this revised HZ near its inner edge, and Mars is just outside of the outer edge. When we studied stellar evolution, you saw the evolutionary tracks for stars in the HR diagram: stars do not maintain the same color and luminosity over their entire lifetimes. When the star begins stable hydr ...
H R Diagram Online Activity
... 2. “The position of each dot on the diagram tells us two things about each star: its _____________________ (or absolute magnitude) and its _____________________________” 3. “The vertical axis represents the star’s ________________________ or absolute magnitude. Luminosity is technically the amount o ...
... 2. “The position of each dot on the diagram tells us two things about each star: its _____________________ (or absolute magnitude) and its _____________________________” 3. “The vertical axis represents the star’s ________________________ or absolute magnitude. Luminosity is technically the amount o ...
H-RDiagramSE
... diagram and become giants or supergiants. Giants and supergiants form when the center of a star collapses and its outer parts expand outwards. What are the characteristics of giants and supergiants? _____________________________ ...
... diagram and become giants or supergiants. Giants and supergiants form when the center of a star collapses and its outer parts expand outwards. What are the characteristics of giants and supergiants? _____________________________ ...
The Physics of Neutron Stars
... One particularly good piece of evidence for starquakes is the outburst observed from the object SGR 1806-20 on December 27, 2004. The details of this observation are given in [3]. The equation of state of neutron star matter is not well-understood, but it is thought that the core consists of a fluid ...
... One particularly good piece of evidence for starquakes is the outburst observed from the object SGR 1806-20 on December 27, 2004. The details of this observation are given in [3]. The equation of state of neutron star matter is not well-understood, but it is thought that the core consists of a fluid ...
Light, spectra, Doppler shifts
... If you take an evacuated glass tube, fill it with hydrogen gas, and apply a voltage (i.e., “light it up like a neon sign”), it will produce light at very specific wavelengths. If viewed with a diffraction grating or spectrograph, the bright lines produced will have wavelengths of: ...
... If you take an evacuated glass tube, fill it with hydrogen gas, and apply a voltage (i.e., “light it up like a neon sign”), it will produce light at very specific wavelengths. If viewed with a diffraction grating or spectrograph, the bright lines produced will have wavelengths of: ...
Light, spectra, Doppler shifts
... If you take an evacuated glass tube, fill it with hydrogen gas, and apply a voltage (i.e., “light it up like a neon sign”), it will produce light at very specific wavelengths. If viewed with a diffraction grating or spectrograph, the bright lines produced will have wavelengths of: ...
... If you take an evacuated glass tube, fill it with hydrogen gas, and apply a voltage (i.e., “light it up like a neon sign”), it will produce light at very specific wavelengths. If viewed with a diffraction grating or spectrograph, the bright lines produced will have wavelengths of: ...
Extra-Solar Life: Habitable Zones
... for life, then there is a limited volume of any stellar system where that might exist – the Habitable Zone • If we assume temperature is dominated by sun/starlight, then the HZ can be calculated for any given star • Likely star types for life are F, G, and K stars (bigger stars die fast; M stars hav ...
... for life, then there is a limited volume of any stellar system where that might exist – the Habitable Zone • If we assume temperature is dominated by sun/starlight, then the HZ can be calculated for any given star • Likely star types for life are F, G, and K stars (bigger stars die fast; M stars hav ...
inaugural091112
... • Dissipates immediately in shock waves • Simulations: demonstrated this …even MHD waves interact and dissipate on a ** sound crossing time **. ...
... • Dissipates immediately in shock waves • Simulations: demonstrated this …even MHD waves interact and dissipate on a ** sound crossing time **. ...
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.