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cooler gases with strong, compressed magnetic fields and adjacent spots have opposite polarity; are magnetic storms; appear as dark splotches on the Sun’s
Gas in the suns chromosphere and corna becomes trapped in Sunspot loops, making a giant solar prominences. Some prominences rise to heights of more than 100,000 km above the Sun’s surface. The can last for days or weeks, disappearing only when the magnetic field as weakened.
Sound waves generated by turbulence in convection zone near surface certain frequencies are amplified by constructive interference; turbulence "rings"
the sun like a bell most are non-radial oscillations
provides a three-dimensional view of the solar interior, as seismology
does for Earth's interior:
chemical composition of interior can be deteremined since speed of waves
depend on it
anchored in the sun and is spiral-shaped because of the sun’s rotation and the solar wind flows out along field lines; this is analogous to a spinning water sprinkler. Groupings of the spiral wedges are often called solar sectors depending on their magnetic polarity.
the brightness of a star as it appears to our eyes
the total amount of power that a star a emits into space. Understanding the difference” a 100 watt light bulb always puts out the same amount of light so its luminosity doesn’t vary but its apparent brightness depends on your distance.
The Intensity or Luminosity of a light source decreases as the inverse square of the distance, just like gravity.
The most direct way to measure a star’s distance is with stellar parallax, the small annual shifts in a star’s apparent position caused by Earth’s motion around the Sun. If we know a star’s distance from parallax, we can calculate its luminosity with the inverse square law for light.
m spectral lines are generally more accurate than temperatures determined from color alone. The bluest colors are called spectral type O, followed in order of declining surface temperature by spectral types B, A, F, G, K, and M (Oh, Be A Fine Guy Kiss Me!) they are subdivided into numbered subcategories (b0, b1 ect) the larger the number the cooler the star
am: Stars do not randomly fall throughout the H-R diagram but instead cluster int four major groups
Upper Main Sequence stars
Solar-like Main Sequence stars
Lower Main Sequence stars or red dwarfs
gas pressure dominates
very slow rotation
little mass loss (weak coronae)
Cooler than M:no p-p fusion
totally convective gas pressure dominates “shine” via gravitational contraction. They are failed stars that do not have/too low of a mass for gravitational contraction to ignite nuclear fusion
A star is born with a limited supply of core hydrogen and therefore can remain as hydrogen-fusing main-sequence star for only a limited time.
is the core left over from a low-mass star, supported against the crush of gravity by electron degeneracy pressure. It typically has the mass of the Sun compressed into a size no larger than that of Earth
When core hydrogen is exhausted, the core begins to shrink while the star as a whole expands, to become a a red giant, with a hydrogen shell fusion around an inert helium core. When the core becomes hot enough, a helium flash initiates helium fusion in the core which fuses helium into carbon. This phase lasts until core helium is exhausted. Low-mass stars never become hot enough for carbon fusion, so at this point their lives must come to an end.
higher metallicity than upper Main Sequence stars (indicates evolution)
Stellar pulsations have been compared with air moving in organ pipes, and the types of possible modes of oscillation have been applied to pulsating stars. Most pulsating stars oscillate in the fundamental mode, i.e., gas simply moves radially in and out (like simple “breathing” motion).
Several types of pulsating variables have multiple periods, up to dozens in β Canis Majoris stars and Dwarf Cepheids; many of these are non-radial oscillations, i.e., waves that move around the star’s surface; observed as "beat" frequencies.
Observations of star formation clearly shows stars form in clusters--not in isolation. We see the most massive protostars reach the Main Sequence first and less massive ones later. The most massive spend a relatively short time as Main Sequence stars; the less massive spend a relatively longer time.
separation between components is large compared to the size of the stars. The average period of wide binaries is ~ 180 yrs; they have a wide range of eccentricities and average e = 0.5.
Orbital mechanics indicate many wide binaries could have arisen via capture.
Periods < 3 yrs, with a wide range of eccentricities and average e = 0.3; for P <11 days, most orbits are near circular.
Depending on the relative distances of members from each other, these systems can be stable or unstable. Stable systems are all arranged in hierarchical systems as follows:
farther away, orbiting the center of mass of the pair
high mass star that dies in a cataclysmic explosion scattering newly produced elements into space and leaving a neutron star or a black hole behind.
scape velocity exceeds c and nothing can escape
globular clusters = have only old stars formed at the same time, 9-13 billion years ago = can determine age by looking at what mass stars are peeling off main sequence
open cluster = hundreds of stars in irregular grouping, have young (blue) stars as well as old;clusters are all young because they disperse within a couple billion years
Brighter galaxies have larger amount of heavier elements (more metal rich) than fainter galaxies Centers of galaxies are more metal rich than outskirts, on average. Decreases the further the galaxy is expected according to the evolution of stars they contain: the earliest generation of stars (i.e., in very distant galaxies) are less metal rich than nearer galaxies (only H and He.)
~ 50% brighter, ~ 50% larger in both optical and H I extent, and has ~ 50% more globular clusters. explained by the fact that the Milky Way Galaxy has a higher star formation rate than Andromeda, so Andromeda experienced most of its star formation in the past, MW still forming.
What do large-scale structures of the universe look like? Explain why we think these structures reflect the density patterns of the early universe .
Large-scale structure traces out long chains and sheets surrounded by big voids with few galaxies. The large structures were regions with enhanced density and the voids started at low-density regions. Ex: 600 million light-years from Earth, large structures and voids are visible.
A sudden and dramatic expansion of the universe (called inflation) was thought to have occurred at the end of the GUT era.
The mass of a SMBH is related to other fundamental galaxy properties
1. more luminous galaxies -- which are also more massive galaxies -- contain more
massive SMBHs, with each being ~ 0.2 % of the mass of the galaxy, and
2. bigger SMBHs live in galaxies whose stars move faster (rotation velocities in spiral disks, and random velocities in ellipticals and spiral bulges).
Come in two main varieties: loose (most abundant) and compact (less abundant). Some groups with few members, or just a single large E galaxy, have lots of X-ray emission, and are called fossil groups; their central galaxies are thought to have cannibalized most former member galaxies. Most galaxies appear to be located in groups; truly isolated galaxies are rare.
come in two main varieties: irregular (most abundant) and regular (less abundant). Member galaxies can have any morphology with a large range in brightness, with an ever-increasing number of fainter members.
Which of the following can be learned about a star from its spectrum ?
Cepheids pulsate (slower, faster) than RR Lyrae stars, they are (cooler, hotter) than RR Lyraes, and their periods (increase, remain constant) with their luminosity.
A bipolar nebula is a distinctive nebular formation characterized by an axially symmetric bi-lobed appearance. Many, but not all, planetary nebulae exhibit an observed bipolar structure. It may be that the two types of nebulae are directly related, one preceding or superseding the other in the evolution of the nebula.
A coronal mass ejection (CME) is a massive burst of solar wind and magnetic fields rising above the solar corona or being released into space.[
Coronal mass ejections are often associated with other forms of solar activity, most notably solar flares, but a causal relationship has not been established. Most ejections originate from active regions on the Sun's surface, such as groupings of sunspots associated with frequent flares. more prominent during solar maxima, then minima
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