Flashcard Set Preview
Side ASide B
Of the three ways in which energy is transferred in nature (radiation, conduction, and convection) which two are important to the sun?
Radiation and Convection
Parallax is the
Apparent shift in the position of a nearby object as we move.
What process provides the power for the sun?
Fusion of hydrogen into helium.
Granulation on the surface of the Sun in caused by
Convective currents carrying heat from beneath the surface.
The nuetrino is
An elusive, subatomic particle having little or no mass and very difficult to detect.
What is the characteristic color of an emission nebula?
Astronomers measure the masses of stars by
Observing the motion of two stars in a binary star system.
A brown dwarf is
An object intermediate between a planet and a star, with not enough mass to begin nuclear reaction in its core.
The evolution of a star is controlled mostly by its
The spectral sequence of star surface temperature as determined by relative spectral line strengths has been given which sequence of letters, in order of decreasing temperature?
If stellar parallax can be measured to a precision of about 0.01 arcsec using a telescope on Earth to observe stars, to what distance does this correspond in space?
What is a positron?
A positive electron.
The phrase "hydrostatic equilibrium" in the sun refers to:
the balance of gravity inward and gas pressure outward.
The Hertzsprung-Russell diagram is a statistical plot of which stellar parameters?
Luminosity and Surface temperature
An arching column of gas suspended over a sunspot group is called
The star Hadar has a spectral classification of B1 III. This tells us that Hadar is a
Cooler, darker regions on the suns surface
Stars that have ejected a planetary nebula go on to become
The temperature of the center of the sun where thermonuclear processes take place is approximately
1.5 x 107 K
The spectral class of the sun in G2 and the star Enif in K2. From this information, we know that Enif is
Cooler than the sun.
Where do we find the most massive stars on the main sequence in a HR diagram?
What fraction of the stars in the night sky are main sequence stars?
Almost all, 90%
The temperature of the sun's photosphere is
How can we characterize the rotation of the Sun?
Differential rotation with the equator rotating faster than the poles
What occurance defines the end of the protostar phase of a star's life and the start of the main sequence phase?
Nuclear reactions begin in its core
What name is given to the visible "surface" of the Sun?
There is a mass limit for a star in the white dwarf phase, the Chandrasekhar limit, beyond which the star can no longer support it's own weight. This mass limit, in terms of solar...
The Zeeman effect refers to
the splitting of spectral lines when magnetic fields are applied to atoms
What is a red giant?
A star burning hydrogen into helium in a shell around the core
What is the last nuclear burning stage in the life of a low mass star like the sun?
Fusion of helium nuclei to form carbon and oxygen
Degeneracy occurs when
electrons inside a star resist being pushed closer together than a certain limit.
What proportion of visible stars in the night sky are multiple star systems?
About 50% or __
A corona hole shows up most prominently in photographs taken at what wavelength?
The majority of the elements heavier than hydrogen and helium in the universe are believed to have originated in
The central cores of stars
The effect of interstellar dust on starlight is
to dim and redden distant stars by preferentially scattering their blue light
The corona of the Sun has a temperature of
1-2 million K
Apparent Magnitude is a measure of the
Brightness of a star as seen from Earth
From the center outwards, the order of the layers or parts of the Sun is
Radiative, convective, photosphere, chromosphere, corona
The extremely high gas temperatures in the solar corona mean that this region is best observed at a wavelength of
The termperature at which thermonuclear reactions begin to convert helium into carbon (helium burning) is
100 million K
Sunspots are caused by
Differential rotation and its effect on weak magnetic fields
A planetary nebula is
An expanding gas shell surrounding a hot, white dwarf
What is the most abundant element in the universe?
The total time that the Sun will spend as a main sequence star is
About 10 billion years (1010 years)
At what distance are stars assumed to be from the Earth when they are represented by their absolute magnitude?
What happens to the helium rich core of a star after the core runs out of hydrogen?
It contracts and heats
On the HR diagram, in which direction does the position occupied by a star move after hydrogen burning ends in the star's core?
Towards the upper right
The age of a cluster can be found by
Determining the turnoff point on the main sequence of its HR diagram
The Orion Nebula is
A large interstellar gas and dust cloud containing many young stars
The spectral type of a star is most directly related to (and determines uniquely) its