Lecture 24: High Mass Star Formation Astro 6890/8980 Prof. Tom
... Core: thermal pressure in rough balance with gravity (may not exist for massive stars). Isothermal and optically thin to IR and radio wavelengths. ...
... Core: thermal pressure in rough balance with gravity (may not exist for massive stars). Isothermal and optically thin to IR and radio wavelengths. ...
Gravitational redshifts
... synthetic line profiles) are shorter than laboratory values due to convective blueshift. Curves before and after mid-transit (µ = 0.21, 0.59, 0.87) are not exact mirror images due to intrinsic stellar line asymmetries. This simulation from a CO5BOLD model predicts the behavior of an Fe I line ( 620 ...
... synthetic line profiles) are shorter than laboratory values due to convective blueshift. Curves before and after mid-transit (µ = 0.21, 0.59, 0.87) are not exact mirror images due to intrinsic stellar line asymmetries. This simulation from a CO5BOLD model predicts the behavior of an Fe I line ( 620 ...
Characteristics of Main Sequence Stars
... very large values of L/4πr2 in the core. This results in a large value of ∇rad , and convective instability. In this region, convective energy transport is extremely efficient, and ∇ ≈ ∇ad . • Because of the extreme temperature sensitivity of CNO burning, nuclear reactions in high mass stars are gen ...
... very large values of L/4πr2 in the core. This results in a large value of ∇rad , and convective instability. In this region, convective energy transport is extremely efficient, and ∇ ≈ ∇ad . • Because of the extreme temperature sensitivity of CNO burning, nuclear reactions in high mass stars are gen ...
- Lowell Observatory
... Is the eruptive event unique? We checked the old observations obtained between 1955 and 1962 in Radcliff Observatory, South Africa. Fig. 2 below shows the comparison between the spectra obtained in 1961 and 2005. The similarity is striking. At that time, star A was a WN6 star as it is now. We do not ...
... Is the eruptive event unique? We checked the old observations obtained between 1955 and 1962 in Radcliff Observatory, South Africa. Fig. 2 below shows the comparison between the spectra obtained in 1961 and 2005. The similarity is striking. At that time, star A was a WN6 star as it is now. We do not ...
Black Holes - University of Dayton
... Definition: An object with a gravitational field so strong that light cannot escape from it. It is believed to be created in the collapse of a very massive star. Context: Everybody has heard of black holes; no one has really seen them. galaxy Definition: A galaxy that is a powerful source of radio ...
... Definition: An object with a gravitational field so strong that light cannot escape from it. It is believed to be created in the collapse of a very massive star. Context: Everybody has heard of black holes; no one has really seen them. galaxy Definition: A galaxy that is a powerful source of radio ...
Astronomy Assignment #1
... Massive stars last for such a short time as main sequence stars because the higher central pressures in those stars drive faster fusion rates and created higher luminosities. The higher luminosities “burn” mass faster and the star will then “burn” through its core reserves of hydrogen faster. Low ma ...
... Massive stars last for such a short time as main sequence stars because the higher central pressures in those stars drive faster fusion rates and created higher luminosities. The higher luminosities “burn” mass faster and the star will then “burn” through its core reserves of hydrogen faster. Low ma ...
Slide 1
... Binary Stars More than 50 % of all stars in our Milky Way are not single stars, but belong to binaries: Pairs or multiple systems of stars which orbit their common center of mass. If we can measure and understand their orbital motion, we can estimate the stellar masses. ...
... Binary Stars More than 50 % of all stars in our Milky Way are not single stars, but belong to binaries: Pairs or multiple systems of stars which orbit their common center of mass. If we can measure and understand their orbital motion, we can estimate the stellar masses. ...
Week 10
... Thought Question: Imagine you are comparing the brightness of two stars. Star A’s luminosity is 5 times higher than star B’s, and star A is 3 times farther away from you than star B. What is the ratio of the brightness of star A to the brightness of star B? (Enter the ratio as a two digit number: i ...
... Thought Question: Imagine you are comparing the brightness of two stars. Star A’s luminosity is 5 times higher than star B’s, and star A is 3 times farther away from you than star B. What is the ratio of the brightness of star A to the brightness of star B? (Enter the ratio as a two digit number: i ...
absolute brightness: The apparent brightness a star would have if it
... electromagnetic radiation: Consists of massless packets of pure energy called photons produced by changes in the energy of charged particles, usually electrons. Photons travel through space at the speed of light. When the changes of energy are small, streams of photons can be described as waves of c ...
... electromagnetic radiation: Consists of massless packets of pure energy called photons produced by changes in the energy of charged particles, usually electrons. Photons travel through space at the speed of light. When the changes of energy are small, streams of photons can be described as waves of c ...
absolute brightness: The apparent brightness a star would have if it
... electromagnetic radiation: Consists of massless packets of pure energy called photons produced by changes in the energy of charged particles, usually electrons. Photons travel through space at the speed of light. When the changes of energy are small, streams of photons can be described as waves of c ...
... electromagnetic radiation: Consists of massless packets of pure energy called photons produced by changes in the energy of charged particles, usually electrons. Photons travel through space at the speed of light. When the changes of energy are small, streams of photons can be described as waves of c ...
R and FUV Observations of Star Formation in
... Heating reduces the amount of cooling gas, but some gas does still manage to cool and form stars. Depending on assumptions, this could provide a few percent of the BCG stellar mass. So heating does not dominate everywhere all the time, though on average heating needs to dominate to keep the star for ...
... Heating reduces the amount of cooling gas, but some gas does still manage to cool and form stars. Depending on assumptions, this could provide a few percent of the BCG stellar mass. So heating does not dominate everywhere all the time, though on average heating needs to dominate to keep the star for ...
ppt 3.8 Mb - Bogoliubov Laboratory of Theoretical Physics
... lower than the luminosities of all but one anomalous Xray pulsar. The properties of this pulsar prove that inferred dipolar magnetic field strength and period cannot alone be responsible for the unusual high-energy properties of the magnetars and create new challenges for understanding the possible ...
... lower than the luminosities of all but one anomalous Xray pulsar. The properties of this pulsar prove that inferred dipolar magnetic field strength and period cannot alone be responsible for the unusual high-energy properties of the magnetars and create new challenges for understanding the possible ...
Answer
... Luminosity remains constant at about 1 Lsun until about 10,000 Myr when it suddenly (and briefly) increases to over 4500 Lsun. 2. Describe how the radius of this star changes with time. Radius remains constant at about 1 Rsun until about 10,000 Myr when it suddenly (and briefly) increases to over 20 ...
... Luminosity remains constant at about 1 Lsun until about 10,000 Myr when it suddenly (and briefly) increases to over 4500 Lsun. 2. Describe how the radius of this star changes with time. Radius remains constant at about 1 Rsun until about 10,000 Myr when it suddenly (and briefly) increases to over 20 ...
Solutions to Homework #4, AST 203, Spring 2009
... General grading rules: One point off per question (e.g., 3a or 3b) for egregiously ignoring the admonition to set the context of your solution. Thus take the point off if relevant symbols aren’t defined, if important steps of explanation are missing, etc. If the answer is written down without *any* ...
... General grading rules: One point off per question (e.g., 3a or 3b) for egregiously ignoring the admonition to set the context of your solution. Thus take the point off if relevant symbols aren’t defined, if important steps of explanation are missing, etc. If the answer is written down without *any* ...
Luminosity - UCF Physics
... measure its distance and apparent brightness: Luminosity = 4π (distance)2 x (Brightness) Note that there is a huge range in stellar ...
... measure its distance and apparent brightness: Luminosity = 4π (distance)2 x (Brightness) Note that there is a huge range in stellar ...
Chapter 17 Measuring the Stars
... Measuring Stellar Masses in Binary Stars In order to measure stellar masses in a binary star, the period and semimajor axis of the orbit must be measured. Once this is done, Kepler’s third law gives the sum of the masses of the two stars. Then the relative speeds of the two stars can be measured usi ...
... Measuring Stellar Masses in Binary Stars In order to measure stellar masses in a binary star, the period and semimajor axis of the orbit must be measured. Once this is done, Kepler’s third law gives the sum of the masses of the two stars. Then the relative speeds of the two stars can be measured usi ...
Slide 1
... End of H He burning in the core of MS star Red Giant phase with inert He-core and outer H-burning shell; star expands and cools, but is brighter Climbs up the RG branch until He-flash in the core Core expands and cools; H-burning decreases; outer layers contract; luminosity decreases but temperatu ...
... End of H He burning in the core of MS star Red Giant phase with inert He-core and outer H-burning shell; star expands and cools, but is brighter Climbs up the RG branch until He-flash in the core Core expands and cools; H-burning decreases; outer layers contract; luminosity decreases but temperatu ...
7.4 Evolution on the Main-Sequence Main-sequence (m
... phase. For the Sun, the contraction time to the m-s τK−H ∼ 30 × 106 yr and τm−s ∼ 1010 yr. For a 9 M star, the corresponding times are much shorter with τK−H ∼ 105 yr and τm−s ∼ 20 × 106 yr. As shown in Sect. 7.3, the m-s can be split into two parts depending on the energy generation process for H- ...
... phase. For the Sun, the contraction time to the m-s τK−H ∼ 30 × 106 yr and τm−s ∼ 1010 yr. For a 9 M star, the corresponding times are much shorter with τK−H ∼ 105 yr and τm−s ∼ 20 × 106 yr. As shown in Sect. 7.3, the m-s can be split into two parts depending on the energy generation process for H- ...
Lecture5
... When one star of a binary gets behind the other star, eclipse happens. The intensity (brightness) of the binary vs time curve is called `light curve’. Then the shape of the light curve can often determine various useful parameters, e.g., the inclination angle , nature of the stellar atmosphere, and ...
... When one star of a binary gets behind the other star, eclipse happens. The intensity (brightness) of the binary vs time curve is called `light curve’. Then the shape of the light curve can often determine various useful parameters, e.g., the inclination angle , nature of the stellar atmosphere, and ...
R 2
... components are similar to those of CVs, so the first idea is that they evolve similarly, through loss or orbital angular momentum, from long to short periods. Actually this is probably not true! ...
... components are similar to those of CVs, so the first idea is that they evolve similarly, through loss or orbital angular momentum, from long to short periods. Actually this is probably not true! ...
Part 1: If a 10000 K blackbody has a wavelength of peak emission at
... Most students didn’t come close to providing this kind of answer even though it was the basis for the Homework 3 assignment of determining spectral types! A typical answer was something like this: “Astronomers measure the color and luminosity of a star to determine its spectral ...
... Most students didn’t come close to providing this kind of answer even though it was the basis for the Homework 3 assignment of determining spectral types! A typical answer was something like this: “Astronomers measure the color and luminosity of a star to determine its spectral ...
The Rigel Star - Emmi
... shows the relationship between the temperature and the absolute brightness of a star. Supergiant: an extremely bright star whose diameter is more than 100 times that of the sun. Protostar: a contracting cloud of gas and dust with enough mass to become a star. Supernova: the really bright explosion o ...
... shows the relationship between the temperature and the absolute brightness of a star. Supergiant: an extremely bright star whose diameter is more than 100 times that of the sun. Protostar: a contracting cloud of gas and dust with enough mass to become a star. Supernova: the really bright explosion o ...
What you need to know
... If you get stuck or are not sure of your answer ask another group If you get really stuck or don’t understand what the Lecture Tutorial is asking as one of us for help ...
... If you get stuck or are not sure of your answer ask another group If you get really stuck or don’t understand what the Lecture Tutorial is asking as one of us for help ...
Cygnus X-1
Cygnus X-1 (abbreviated Cyg X-1) is a well-known galactic X-ray source, thought to be a black hole, in the constellation Cygnus. It was discovered in 1964 during a rocket flight and is one of the strongest X-ray sources seen from Earth, producing a peak X-ray flux density of 6977229999999999999♠2.3×10−23 Wm−2 Hz−1 (7003230000000000000♠2.3×103 Jansky). Cygnus X-1 was the first X-ray source widely accepted to be a black hole and it remains among the most studied astronomical objects in its class. The compact object is now estimated to have a mass about 14.8 times the mass of the Sun and has been shown to be too small to be any known kind of normal star, or other likely object besides a black hole. If so, the radius of its event horizon is about 7004440000000000000♠44 km.Cygnus X-1 belongs to a high-mass X-ray binary system about 7019574266339685654♠6070 ly from the Sun that includes a blue supergiant variable star designated HDE 226868 which it orbits at about 0.2 AU, or 20% of the distance from the Earth to the Sun. A stellar wind from the star provides material for an accretion disk around the X-ray source. Matter in the inner disk is heated to millions of degrees, generating the observed X-rays. A pair of jets, arranged perpendicular to the disk, are carrying part of the energy of the infalling material away into interstellar space.This system may belong to a stellar association called Cygnus OB3, which would mean that Cygnus X-1 is about five million years old and formed from a progenitor star that had more than 7001400000000000000♠40 solar masses. The majority of the star's mass was shed, most likely as a stellar wind. If this star had then exploded as a supernova, the resulting force would most likely have ejected the remnant from the system. Hence the star may have instead collapsed directly into a black hole.Cygnus X-1 was the subject of a friendly scientific wager between physicists Stephen Hawking and Kip Thorne in 1975, with Hawking betting that it was not a black hole. He conceded the bet in 1990 after observational data had strengthened the case that there was indeed a black hole in the system. This hypothesis has not been confirmed due to a lack of direct observation but has generally been accepted from indirect evidence.