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17_Testbank
17_Testbank

... 4) There is no limit to the mass with which a star can be born. Answer: FALSE 5) Stars with high masses live longer than stars with lower masses. Answer: FALSE 6) Stars of lower mass have deeper convection zones outside their cores than stars of higher mass. Answer: TRUE 7) Convection never occurs i ...
Classifying the Stars
Classifying the Stars

... Period:_______________ ...
Anna Frebel nucleosynthesis, stars + chemical evolution
Anna Frebel nucleosynthesis, stars + chemical evolution

Document
Document

... Betelgeuse has a very high luminosity (40,000 times as bright as our Sun), but its surface is cool (below 4000 K). Which of the following explains this? a. ...
Part 2 - MGNet
Part 2 - MGNet

... • Magnetic field of Super-massive black hole – produces two jets along rotation axis of disk ...
Dust Clouds at the Center of Milky Way
Dust Clouds at the Center of Milky Way

... • In our Milky Way and in external galaxies, the space between the stars is filled with an interstellar medium consisting of gas and dust ...
Newfoundland Sky in Summer
Newfoundland Sky in Summer

Properties of Stars - Indiana State University
Properties of Stars - Indiana State University

... – Superimposed on this orbital motion are small random motions of about 20 km/sec – In addition to their motion through space, stars spin on their axes and this spin can be measured using the Doppler shift technique – young stars are found to rotate faster than old stars ...
“Astronomy Picture of the Day” Leads to a Research Breakthrough
“Astronomy Picture of the Day” Leads to a Research Breakthrough

ON STARS, THEIR EVOLUTION AND THEIR STABILITY
ON STARS, THEIR EVOLUTION AND THEIR STABILITY

... I do not see how a star which has once got into this compressed state is ever going to get out of it... It would seem that the star will be in an awkward predicament when its supply of subatomic energy fails. The paradox posed by Eddington was reformulated in clearer physical terms by R. H. Fowler. ...
Quiz  # 5 – 11/15/2011
Quiz # 5 – 11/15/2011

... 9. The most important characteristic of a star for determining its lifetime is A. radius B. luminosity C. distance from the main sequence D. mass E. temperature 10. If the Sun were to suddenly become a black hole, its radius would shrink by 200,000 times. The gravitational force felt by the Earth at ...
Phase Analysis of RV Tauri and Semi-regular Variables Abstract
Phase Analysis of RV Tauri and Semi-regular Variables Abstract

... variable stars. The ultimate objective for our research is to determine whether the stars stellar properties such as temperature, radius, and luminosity correlate with their pulsation cycles. In order to determine this, we need to closely examine the light curves to determined the proper pulsation p ...
5 Understanding stars and star ClUsters
5 Understanding stars and star ClUsters

... with a negative charge that orbit the atomic nucleus. Electrons must always move in distinct orbit levels. If the electron moves to the next lower orbit it loses energy and spits out a light particle (photon) of a specific color (energy). Each different atom has different color photons, which are em ...
Supernova and Supernova Remnants lec 1-2
Supernova and Supernova Remnants lec 1-2

Globular Cluster in Canes Venatici
Globular Cluster in Canes Venatici

So, what`s the problem for high
So, what`s the problem for high

... finished accretion from its parent cloud core. Radiation pressure should stop accretion before a star can reach its final mass. High-mass stars only form in clusters, so isolating individuals is difficult: Almost no HMPOs have been unambiguously identified at specific star-like points on the sky tha ...
The Search for New “r-process-Enhanced” Metal
The Search for New “r-process-Enhanced” Metal

... stars ([Fe/H] < -2.0) which have been discovered recently that exhibit strong enhancements in their ratios of r-process elements, compared with the Sun • r-I: 0.3 < [r-process/Fe] < 1.0 (~ 10 known) • r-II: 1.0 < [r-process/Fe] < 1.7 ( 4 known) • A few have measurable U as well, allowing for the use ...
Chapter 21 Notes
Chapter 21 Notes

... fades; it is a white dwarf whose larger partner continually transfers material to it. • Stars greater than eight solar masses can have fusion in their cores going all the way up to iron, which is stable against further fusion. • The star continues to collapse after the iron core is found, implodes, ...
ASTRO-114--Lecture 40-
ASTRO-114--Lecture 40-

NAME
NAME

... ____ 20. What type of standard candle is used to determine distances to globular clusters? a. O-type main-sequence stars b. Cepheid variable stars c. T Tauri stars d. Type I supernovae e. RR Lyrae stars ____ 21. By comparing globular clusters, you find that Cluster A’s RR Lyrae stars are 100 times f ...
Constellations
Constellations

1 Epiphany 2014 Following Stars Fr. Frank Schuster In preparation
1 Epiphany 2014 Following Stars Fr. Frank Schuster In preparation

... Gospel of Matthew wants to make it clear to us: Jesus wasn’t born to save only Israel. Jesus was born to save the whole world. Of course, the three gifts the Magi bring are symbolic. Gold represents the fact that Jesus is royalty, the new King David so to speak. Frankincense represents Jesus’ divini ...
Lecture 6: Stellar Distances and Brightness
Lecture 6: Stellar Distances and Brightness

ppt format
ppt format

... must start with an excited H atom- one with an electron in the n=2 level. As the temperature of a gas increases, collisions become more energetic, and a greater fraction of the H atoms are excited, so there are more H-beta absorptions. BUT if the temperature becomes too high, an increasing fraction ...
Deep HST Imaging of M33: Reliability and Recovery of the Star
Deep HST Imaging of M33: Reliability and Recovery of the Star

< 1 ... 190 191 192 193 194 195 196 197 198 ... 410 >

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.
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