Parallax, Magnitudes,

Spectral Classes & HR

Diagrams

I. Parallax

A. Parallax is the _________________ to determine the ________ to stars. Parallax only works for _________ stars.

B. Parallax is the apparent ______ of a “nearby” star with respective to the background stars when viewed _____________________. Because of Earth’s orbit around the Sun, this happens when astronomers view a “nearby” star at ____________________________.

C. An example of this is when you hold your finger ___________________________and view it first with ________ and then the _________.

D. The term parallax is derived from the Greek word “parallaxis”, which means _________.

E. Nearby objects have a ______ parallax than more distant objects. Therefore, the further away a star is, the ________________ to measure its parallax.

I. Parallax

A. Parallax is the _only direct method_ to determine the _distance_ to stars. Parallax only works for _“nearby” _ stars.

B. Parallax is the apparent ______ of a “nearby” star with respective to the background stars when viewed _____________________. Because of Earth’s orbit around the Sun, this happens when astronomers view a “nearby” star at ____________________________.

C. An example of this is when you hold your finger ___________________________and view it first with ________ and then the _________.

D. The term parallax is derived from the Greek word “parallaxis”, which means _________.

E. Nearby objects have a ______ parallax than more distant objects. Therefore, the further away a star is, the ________________ to measure its parallax.

I. Parallax

A. Parallax is the _only direct method_ to determine the _distance_ to stars. Parallax only works for _“nearby” _ stars.

B. Parallax is the apparent _shift_ of a “nearby” star with respective to the background stars when viewed _from 2 different positions_. Because of Earth’s orbit around the Sun, this happens when astronomers view a “nearby” star at _2 different times during the year_.

C. An example of this is when you hold your finger ___________________________and view it first with ________ and then the _________.

D. The term parallax is derived from the Greek word “parallaxis”, which means _________.

E. Nearby objects have a ______ parallax than more distant objects. Therefore, the further away a star is, the ________________ to measure its parallax.

I. Parallax

A. Parallax is the _only direct method_ to determine the _distance_ to stars. Parallax only works for _“nearby” _ stars.

B. Parallax is the apparent _shift_ of a “nearby” star with respective to the background stars when viewed _from 2 different positions_. Because of Earth’s orbit around the Sun, this happens when astronomers view a “nearby” star at _2 different times during the year_.

C. An example of this is when you hold your finger ___________________________and view it first with ________ and then the _________.

D. The term parallax is derived from the Greek word “parallaxis”, which means _________.

E. Nearby objects have a ______ parallax than more distant objects. Therefore, the further away a star is, the ________________ to measure its parallax.

I. Parallax

A. Parallax is the _only direct method_ to determine the _distance_ to stars. Parallax only works for _“nearby” _ stars.

B. Parallax is the apparent _shift_ of a “nearby” star with respective to the background stars when viewed _from 2 different positions_. Because of Earth’s orbit around the Sun, this happens when astronomers view a “nearby” star at _2 different times during the year_.

C. An example of this is when you hold your finger _up in front of you at arms length_ and view it first with _one eye_ and then the _other eye_.

D. The term parallax is derived from the Greek word “parallaxis”, which means _________.

E. Nearby objects have a ______ parallax than more distant objects. Therefore, the further away a star is, the ________________ to measure its parallax.

I. Parallax

A. Parallax is the _only direct method_ to determine the _distance_ to stars. Parallax only works for _“nearby” _ stars.

B. Parallax is the apparent _shift_ of a “nearby” star with respective to the background stars when viewed _from 2 different positions_. Because of Earth’s orbit around the Sun, this happens when astronomers view a “nearby” star at _2 different times during the year_.

C. An example of this is when you hold your finger _up in front of you at arms length_ and view it first with _one eye_ and then the _other eye_.

D. The term parallax is derived from the Greek word “parallaxis”, which means _alteration_.

E. Nearby objects have a ______ parallax than more distant objects. Therefore, the further away a star is, the ________________ to measure its parallax.

I. Parallax

A. Parallax is the _only direct method_ to determine the _distance_ to stars. Parallax only works for _“nearby” _ stars.

B. Parallax is the apparent _shift_ of a “nearby” star with respective to the background stars when viewed _from 2 different positions_. Because of Earth’s orbit around the Sun, this happens when astronomers view a “nearby” star at _2 different times during the year_.

C. An example of this is when you hold your finger _up in front of you at arms length_ and view it first with _one eye_ and then the _other eye_.

D. The term parallax is derived from the Greek word “parallaxis”, which means _alteration_.

E. Nearby objects have a _larger_ parallax than more distant objects. Therefore, the further away a star is, the _more difficult it is_ to measure its parallax.

F. ESA’s Hipparcos satellite has used parallax to determine the distance of the closest _________ stars to the Sun. It had the ability to measure stellar shifts equivalent to the width of _________________________!

G. ESA’s next parallax mission, Gaia, was launched Dec 19, 2013. It will determine the distance to the closest ________ stars. It will be able to measure a star’s position to the equivalent of the width of _________________________!!

H. The parallax method is extremely important not only because it is the only direct method for determining stellar distances, but also because it ______________ for checking the validity of the other ________ distance measuring techniques.

F. ESA’s Hipparcos satellite has used parallax to determine the distance of the closest _100,000_ stars to the Sun. It had the ability to measure stellar shifts equivalent to the width of _a human hair seen at 20 km_!

G. ESA’s next parallax mission, Gaia, was launched Dec 19, 2013. It will determine the distance to the closest ________ stars. It will be able to measure a star’s position to the equivalent of the width of _________________________!!

H. The parallax method is extremely important not only because it is the only direct method for determining stellar distances, but also because it ______________ for checking the validity of the other ________ distance measuring techniques.

F. ESA’s Hipparcos satellite has used parallax to determine the distance of the closest _100,000_ stars to the Sun. It had the ability to measure stellar shifts equivalent to the width of _a human hair seen at 20 km_!

G. ESA’s next parallax mission, Gaia, was launched Dec 19, 2013. It will determine the distance to the closest _1 billion_ stars. It will be able to measure a star’s position to the equivalent of the width of _a human hair seen at 1000 km_!!

H. The parallax method is extremely important not only because it is the _______________ for determining stellar distances, but also because it ______________ for checking the validity of the other ________ distance measuring techniques.

F. ESA’s Hipparcos satellite has used parallax to determine the distance of the closest _100,000_ stars to the Sun. It had the ability to measure stellar shifts equivalent to the width of _a human hair seen at 20 km_!

G. ESA’s next parallax mission, Gaia, was launched Dec 19, 2013. It will determine the distance to the closest _1 billion_ stars. It will be able to measure a star’s position to the equivalent of the width of _a human hair seen at 1000 km_!!

H. The parallax method is extremely important not only because it is the only direct method for determining stellar distances, but also because it _forms the basis_ for checking the validity of the other _indirect_ distance measuring techniques.

II. Stellar Magnitudes

A. The magnitude of a star is a description of how _______ a star is.

B. The scale was initially set up by Norman Pogson in 1856 with a magnitude ___ given to the brightest star in the sky and a magnitude ___ being the dimmest star that could be seen ________________.

C. The apparent magnitude of a star is a measure of its brightness _________________. The brighter an object appears, the ______ the value of its magnitude. For example, _________________ and __________________.

D. The absolute magnitude of a star is a measure of its ________________. It is a measure of a star’s brightness from a fixed distance of __________________. Note that the absolute magnitude of a star is equal to the apparent magnitude if the observer is at a distance of 10 parsecs from the star.

II. Stellar Magnitudes

A. The magnitude of a star is a description of how _bright_ a star is.

B. The scale was initially set up by Norman Pogson in 1856 with a magnitude ___ given to the brightest star in the sky and a magnitude ___ being the dimmest star that could be seen ________________.

C. The apparent magnitude of a star is a measure of its brightness _________________. The brighter an object appears, the ______ the value of its magnitude. For example, _________________ and __________________.

D. The absolute magnitude of a star is a measure of its ________________. It is a measure of a star’s brightness from a fixed distance of __________________. Note that the absolute magnitude of a star is equal to the apparent magnitude if the observer is at a distance of 10 parsecs from the star.

II. Stellar Magnitudes

A. The magnitude of a star is a description of how _bright_ a star is.

B. The scale was initially set up by Norman Pogson in 1856 with a magnitude _1_ given to the brightest star in the sky and a magnitude _6_ being the dimmest star that could be seen _with the naked eye_.

C. The apparent magnitude of a star is a measure of its brightness _________________. The brighter an object appears, the ______ the value of its magnitude. For example, _________________ and __________________.

D. The absolute magnitude of a star is a measure of its ________________. It is a measure of a star’s brightness from a fixed distance of __________________. Note that the absolute magnitude of a star is equal to the apparent magnitude if the observer is at a distance of 10 parsecs from the star.

II. Stellar Magnitudes

A. The magnitude of a star is a description of how _bright_ a star is.

B. The scale was initially set up by Norman Pogson in 1856 with a magnitude _1_ given to the brightest star in the sky and a magnitude _6_ being the dimmest star that could be seen _with the naked eye_.

C. The apparent magnitude of a star is a measure of its brightness _as seen from Earth_. The brighter an object appears, the _lower_ the value of its magnitude. For example, _1 is brighter than 3_ and _-1 is brighter than 1_.

D. The absolute magnitude of a star is a measure of its ________________. It is a measure of a star’s brightness from a fixed distance of __________________. Note that the absolute magnitude of a star is equal to the apparent magnitude if the observer is at a distance of 10 parsecs from the star.

II. Stellar Magnitudes

A. The magnitude of a star is a description of how _bright_ a star is.

B. The scale was initially set up by Norman Pogson in 1856 with a magnitude _1_ given to the brightest star in the sky and a magnitude _6_ being the dimmest star that could be seen _with the naked eye_.

C. The apparent magnitude of a star is a measure of its brightness _as seen from Earth_. The brighter an object appears, the _lower_ the value of its magnitude. For example, _1 is brighter than 3_ and _-1 is brighter than 1_.

D. The absolute magnitude of a star is a measure of its _intrinsic brightness_. It is a measure of a star’s brightness from a fixed distance of _10 parsecs (32.6 ly)_. Note that the absolute magnitude of a star is equal to the apparent magnitude if the observer is at a distance of 10 parsecs from the star.

Table Comparing Apparent versus Absolute MagnitudesStar Apparent Magnitude Absolute MagnitudeSun -26.7 +4.83

Full Moon -12.6Venus -4.6Mars -2.9

Jupiter -2.9Sirius A -1.44 +1.45Arcturus -0.05 -0.31

Vega +0.03 +0.58Betelguese +0.45 -5.14

Antares +1.06 -5.28Deneb +1.25 -8.73

E. The Hubble Space Telescope has observed stars with magnitudes down to ____ at visible wavelengths and the Keck telescopes have located similarly faint stars in the infrared with _________________.

F. There is a _________ difference in brightness for stars that differ by a _____________. For example, a star of magnitude 1 is 100 times as bright as a star with magnitude 6.

Hubble Space Telescope

Keck Telescopes

E. The Hubble Space Telescope has observed stars with magnitudes down to _30_ at visible wavelengths and the Keck telescopes have located similarly faint stars in the infrared with _very long exposures_.

F. There is a _________ difference in brightness for stars that differ by a _____________. For example, a star of magnitude 1 is 100 times as bright as a star with magnitude 6.

Hubble Space Telescope

Keck Telescopes

E. The Hubble Space Telescope has observed stars with magnitudes down to _30_ at visible wavelengths and the Keck telescopes have located similarly faint stars in the infrared with _very long exposures_.

F. There is a _100 times_ difference in brightness for stars that differ by a _magnitude of 5_. For example, a star of magnitude 1 is 100 times as bright as a star with magnitude 6.

Hubble Space Telescope

Keck Telescopes

III. Spectral Classes

A. Stars are classified largely by their ___________________. This is precisely measured by observing their _______________________.

B. A star’s color and temperature is determined _____________________. The more massive a star is, the _________________ it is.

C. Most stars are currently classified using the letters O, B, A, F, G, K and M, where O stars are the ________ and M stars are the _______.

D. The order of these letters can be remembered by this pneumonic:

___________________________________________________________________________________________

III. Spectral Classes

A. Stars are classified largely by their _color and temperature_. This is precisely measured by observing their _spectra with a spectrograph_.

B. A star’s color and temperature is determined _____________________. The more massive a star is, the _________________ it is.

C. Most stars are currently classified using the letters O, B, A, F, G, K and M, where O stars are the ________ and M stars are the _______.

D. The order of these letters can be remembered by this pneumonic:

___________________________________________________________________________________________

III. Spectral Classes

A. Stars are classified largely by their _color and temperature_. This is precisely measured by observing their _spectra with a spectrograph_.

B. A star’s color and temperature is determined _almost entirely by its mass_. The more massive a star is, the _hotter and brighter_ it is.

C. Most stars are currently classified using the letters O, B, A, F, G, K and M, where O stars are the ________ and M stars are the _______.

D. The order of these letters can be remembered by this pneumonic:

___________________________________________________________________________________________

III. Spectral Classes

A. Stars are classified largely by their _color and temperature_. This is precisely measured by observing their _spectra with a spectrograph_.

B. A star’s color and temperature is determined _almost entirely by its mass_. The more massive a star is, the _hotter and brighter_ it is.

C. Most stars are currently classified using the letters O, B, A, F, G, K and M, where O stars are the _hottest_ and M stars are the _coolest_.

D. The order of these letters can be remembered by this pneumonic:

___________________________________________________________________________________________

III. Spectral Classes

A. Stars are classified largely by their _color and temperature_. This is precisely measured by observing their _spectra with a spectrograph_.

B. A star’s color and temperature is determined _almost entirely by its mass_. The more massive a star is, the _hotter and brighter_ it is.

C. Most stars are currently classified using the letters O, B, A, F, G, K and M, where O stars are the _hottest_ and M stars are the _coolest_.

D. The order of these letters can be remembered by this pneumonic:

_Oh,__________Be___________A____________Fine__________Girl/Guy_______Kiss__________Me__________

E. General Trends:

O B A F G K M

F G K MB A

E. General Trends:

O B A F G K M

Highest Mass Lowest Mass

F G K MB A

E. General Trends:

O B A F G K M

Highest Mass

Hottest

Lowest Mass

Coolest

F G K MB A

E. General Trends:

O B A F G K M

Highest Mass

Hottest

Brightest

Lowest Mass

Coolest

Dimmest

F G K MB A

E. General Trends:

O B A F G K M

Highest Mass

Hottest

Brightest

Shortest Lifetime

Lowest Mass

Coolest

Dimmest

Longest Lifetime

F G K MB A

IV. HR Diagrams

A. HR Diagrams are to __________ as the ________________________.

B. The HR diagrams where developed by ________________

and __________________.

C. The Hertzsprung–Russell diagram is a scatter graph of stars showing the relationship between the stars' __________________________ versus their _______________________________.

D. The HR diagrams represented a major step towards an understanding the _______________.

IV. HR Diagrams

A. HR Diagrams are to _astronomy_ as the _Periodic Table is to chemistry_.

B. The HR diagrams where developed by ________________

and __________________.

C. The Hertzsprung–Russell diagram is a scatter graph of stars showing the relationship between the stars' __________________________ versus their _______________________________.

D. The HR diagrams represented a major step towards an understanding the _______________.

IV. HR Diagrams

A. HR Diagrams are to _astronomy_ as the _Periodic Table is to chemistry_.

B. The HR diagrams where developed by _Ejnar

Hertzsprung_ and _Henry Norris Russel_.

C. The Hertzsprung–Russell diagram is a scatter graph of stars showing the relationship between the stars' __________________________ versus their _______________________________.

D. The HR diagrams represented a major step towards an understanding the _______________.

IV. HR Diagrams

A. HR Diagrams are to _astronomy_ as the _Periodic Table is to chemistry_.

B. The HR diagrams where developed by _Ejnar

Hertzsprung_ and _Henry Norris Russel_.

C. The Hertzsprung–Russell diagram is a scatter graph of stars showing the relationship between the stars' _abolute magnitude (or luminosity)_ versus their _spectral type (or surface temperature)_.

D. The HR diagrams represented a major step towards an understanding the _______________.

IV. HR Diagrams

A. HR Diagrams are to _astronomy_ as the _Periodic Table is to chemistry_.

B. The HR diagrams where developed by _Ejnar

Hertzsprung_ and _Henry Norris Russel_.

C. The Hertzsprung–Russell diagram is a scatter graph of stars showing the relationship between the stars' _abolute magnitude (or luminosity)_ versus their _spectral type (or surface temperature)_.

D. The HR diagrams represented a major step towards an understanding the _evolution of stars_.

Parallax, Magnitudes,

Spectral Classes & HR

Diagrams