ASTRONOMY EXAM 3
Call Kai
Learn
Practice Test
Spaced Repetition
Match
Flashcards
Knowt Play1/63
There's no tags or description
Looks like no tags are added yet.
Name | Mastery | Learn | Test | Matching | Spaced | Call with Kai |
|---|
No analytics yet
Send a link to your students to track their progress
64 Terms
Apparent magnitude is a measure of
The brightness of light from a star or other object as seen from Earth
A star of apparent magnitude +5 appears
Fainter than a star of apparent magnitude +3
A star of apparent magnitude -1 appears
Brighter than a star of apparent magnitude +3
Absolute magnitude (M) is defined as the apparent magnitude a star would have if
It were located at exactly 10 pc from Earth
Light leaving a point source spreads out according to which law?
I â 1/dÂČ
Spectral types of stars uniquely define their
Surface temperatures
The Sun's spectral classification is
G2V
What two parameters are plotted on the Hertzsprung-Russell diagram?
Luminosity and surface temperature (spectral type)
What fraction of stars near the Sun are main-sequence stars?
Over 90%
The chemical makeup of the Sun's surface can be determined by
Solar spectroscopy
Compared to a star in the middle of the H-R diagram
a star in the upper right is,Larger
The space between stars contains
Gas and dust
The luminosity class of a star is most closely related to its
Radius
What is a star's luminosity?
Total energy emitted per second into space
What shorthand notation is used for stellar luminosity?
Lâ
What is the order of stellar surface temperatures from hottest to coolest?
OBAFGKM
What is the name of the space between stars in our galaxy?
Interstellar space
How have molecules like formaldehyde been detected in interstellar clouds?
By molecular emission lines
Which molecule contains nitrogen but no oxygen?
Ammonia (NHâ)
What is the most abundant element in the universe?
Hydrogen
Which molecule is likely the most common in interstellar space?
Hâ (molecular hydrogen)
New stars are formed from
Huge cool dust and molecular gas clouds
What is the typical mass of a giant molecular cloud?
100,000 to 1 million solar masses
What process occurs inside main-sequence stars?
Hydrogen fusion into helium in the core
How is gas distributed in interstellar space?
In clumps concentrated in molecular clouds
Hydrogen fusion occurs during which phase of a star's life?
Main-sequence phase
How do massive stars normally end their lives?
They explode
A white dwarf is found where on the H-R diagram?
Below and to the left of the main sequence
What property most strongly determines a star's lifetime?
Mass
The absolute magnitude of a star is defined at what distance?
32.6 light-years (10 parsecs)
The Crab Nebula is an example of
A supernova remnant
How will the Sun end its life?
Red giant â white dwarf
Where are stars and planetary systems most likely forming?
In nebulae of gas and dust
How many years would it take to reach Proxima Centauri at 50
000 mph?,57,077 years
Accretion of matter within an interstellar cloud leads to
A protostar
How far away is the nearest star beyond the Sun?
About 4.2 light-years
Compared to a star in the middle of the H-R diagram
a star in the upper right is,Larger
Where are emission nebulae (H II regions) found?
Around hot stars
A white dwarf is
A small, very hot, low-mass stellar remnant
How fast is the speed of light?
186,000 miles per second
A typical nova brightens by a factor of
10⎠to 10â¶
When a star was a protostar it was
Larger and cooler
Enif is K2 and the Sun is G2. What can be concluded?
Enif is cooler than the Sun
One of the most recent supernova explosions in our galaxy created
Cassiopeia A
The Orion Nebula is
A large interstellar gas and dust cloud containing young stars
What marks the start of the main-sequence phase?
Nuclear fusion begins in the core
Is Earth a self-luminous object?
No
What is the minimum mass required to be a star?
0.08 solar masses
Why are protostars difficult to observe?
They are surrounded by gas and dust and emit mainly infrared radiation
The lower edge of the Main Sequence band is known as
The Zero-Age Main Sequence (ZAMS)
Which location on the H-R diagram corresponds to a T Tauri star?
Location 4
Which is NOT evidence for the interstellar medium?
Molecular absorption lines in cool stars
Interstellar clouds may collapse to form stars if they
Encounter a shock wave
How are molecular clouds commonly observed?
By radio observations of CO emission
Dust in the interstellar medium causes distant stars to appear
Fainter and cooler
The lowest mass object capable of hydrogen fusion has a mass of
0.08 solar masses
As a main-sequence star exhausts hydrogen
it becomes,Cooler and more luminous
The Crab Nebula is a
Supernova remnant
Why are star clusters important?
They test theories of stellar evolution
After exhausting hydrogen in its core
a main-sequence star becomes,A red giant star
A planetary nebula is
The expelled outer envelope of a medium-mass star
The Chandrasekhar limit states that
White dwarfs above 1.4 solar masses are unstable
A white dwarf is composed of
Carbon and oxygen nuclei with degenerate electrons
A planetary nebula produces what type of spectrum?
Emission spectrum