Exam 10: Observing Properties of Distant Stars

The Henry Draper Catalog of stellar classifications was developed beginning in the late nineteenth century.It originally classified stars according to the strengths of their hydrogen lines.By the 1920s,however,the sequence had been reorganized so that the stars were classified by surface temperature.What important scientific development made possible this reinterpretation?

Sirius,in Canis Major (the large hunting dog of Orion),is the brightest star in the winter night sky.It has a parallax angle of 0.38 seconds of arc.Orion's other hunting dog,Canis Minor,has as its brightest star Procyon,with a parallax angle of 0.29 seconds of arc.Vega,in Lyra the Lyre (Harp),is the brightest star in the summer night sky.It has a parallax angle of 0.13 seconds of arc.Which of these stars is farthest away?

Compared with a star in the middle left of the diagram,a star in the lower left part of the Hertzsprung-Russell diagram is

Which of the following is one of the facts that must be known in order to determine the distance to a star by parallax?

White dwarfs are approximately the same size as Earth.

What does apparent magnitude tell us about a star?

A star with a parallax angle of 1 second of arc is defined to have a distance of 1 light-year.

Suppose that two identical stars (having the same total light output or luminosity)are located such that star A is at a distance of 5 pc and star B is at a distance of 25 pc.How will star B appear,compared to star A?

Light,leaving a point source,spreads out so that the apparent brightness,b,of light per unit area varies with distance d according to which law ( $\alpha$ means "proportional to")?

Two stars are found to have the same luminosity.However,one star has twice the surface temperature of the other.From this information,what can you determine about their radii?

What is the physical reason that astronomers can find the luminosity class (I,II,III,IV,or V)of a star using the star's spectrum?

In order to measure the parallax angle of a star,it is necessary to know the direction to the star on two different days of the year and

A yellow star and a blue star are the same distance from Earth and appear the same brightness in the sky.Which one is bigger?

A parallax of 0.5 arcseconds would be how many degrees?

How can a star's temperature be determined by its color?

How can you measure the mass of a star?

The smaller angle through which a star's apparent position changes due to the change in position of an observer,the greater the distance it is from the observer.

The Hertzsprung-Russell diagram is a plot of

As you drive along a road,trees in the middle distance seem to shift in position relative to faraway hills.What name is given to this phenomenon?

The spectral sequence of star surface temperature,as determined by relative spectral absorption line strengths,has been given which sequence of letters,in order of decreasing temperature?