astr 1102-002 2008 fall semester
DESCRIPTION
ASTR 1102-002 2008 Fall Semester. Joel E. Tohline, Alumni Professor Office: 247 Nicholson Hall [Slides from Lecture19]. Chapter 23 : Our Galaxy and Chapter 24: Galaxies. Schematic Illustration of Our (Milky Way) Galaxy. Real ‘All Sky’ Images of Our (Milky Way) Galaxy. Aside:. - PowerPoint PPT PresentationTRANSCRIPT
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ASTR 1102-0022008 Fall Semester
Joel E. Tohline, Alumni ProfessorOffice: 247 Nicholson Hall
[Slides from Lecture19]
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Chapter 23: Our Galaxyand
Chapter 24: Galaxies
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Schematic Illustration of
Our (Milky Way) Galaxy
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Real ‘All Sky’ Imagesof
Our (Milky Way) Galaxy
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Aside:
• Atomic transition that gives rise to 21-cm radiation, which is used by astronomers to map out the distribution of neutral hydrogen throughout our Galaxy (and other galaxies), is also the physical principle underlying the MRI (magnetic resonance imaging) diagnostic tool in modern medicine.
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Medical MRI
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Determining Size of MW Galaxy
• We have not always known that the diameter of our Galaxy is ~ 50 kpc (as illustrated in following slide)
• Herschel’s map of our Galaxy (1785) based on star counts– Thin disk not much more than 1 kpc across– Sun approximately at center of disk
![Page 21: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/21.jpg)
Determining Size of MW Galaxy
• We have not always known that the diameter of our Galaxy is ~ 50 kpc (as illustrated in following slide)
• Herschel’s map of our Galaxy (1785) based on star counts– Thin disk not much more than 1 kpc across– Sun approximately at center of disk
![Page 22: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/22.jpg)
![Page 23: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/23.jpg)
Determining Size of MW Galaxy
• We have not always known that the diameter of our Galaxy is ~ 50 kpc (as illustrated in following slide)
• For example, Herschel’s map of our Galaxy (1785) based on star counts …– Thin disk not much more than 1 kpc across– Sun approximately at center of disk
![Page 24: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/24.jpg)
Herschel’s Map of MW Galaxy
![Page 25: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/25.jpg)
Determining Size of MW Galaxy
• We have not always known that the diameter of our Galaxy is ~ 50 kpc (as illustrated in following slide)
• For example, Herschel’s map of our Galaxy (1785) based on star counts …– Thin disk not much more than 1 kpc across– Sun approximately at center of disk
• Herschel’s map grossly distorted by interstellar extinction
![Page 26: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/26.jpg)
Prominent and Obscured Objects
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Shapley’s View of MW Galaxy
• Look out of the plane of the MW disk to minimize obscuration due to interstellar extinction
• Distribution of Globular Clusters not symmetric about Sun’s location
• Distances to GCs obtained using RR Lyrae variable stars as “standard candles”
![Page 28: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/28.jpg)
Shapley’s View of MW Galaxy
• Look out of the plane of the MW disk to minimize obscuration due to interstellar extinction
• Distribution of Globular Clusters not symmetric about Sun’s location
• Distances to GCs obtained using RR Lyrae variable stars as “standard candles”
![Page 29: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/29.jpg)
![Page 30: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/30.jpg)
Shapley’s View of MW Galaxy
• Look out of the plane of the MW disk to minimize obscuration due to interstellar extinction
• Distribution of Globular Clusters not symmetric about Sun’s location
• Distances to GCs obtained using RR Lyrae variable stars as “standard candles”
![Page 31: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/31.jpg)
Shapley’s View of MW Galaxy
• Look out of the plane of the MW disk to minimize obscuration due to interstellar extinction
• Distribution of Globular Clusters not symmetric about Sun’s location
• Distances to GCs obtained using RR Lyrae variable stars as “standard candles”
![Page 32: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/32.jpg)
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Determining Distances in Astronomy
• Stellar parallax• Spectroscopic parallax (main-sequence
fitting): – Remember distance modulus:
(m – M) = 5 log(d) – 5– If you know “M” for a certain type of star, then
a measurement of “m” gives you “d”
• Standard candles: Identifiable stars for which you know “M”
![Page 34: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/34.jpg)
Determining Distances in Astronomy
• Stellar parallax• Spectroscopic parallax (main-sequence
fitting): – Remember distance modulus:
(m – M) = 5 log(d) – 5– If you know “M” for a certain type of star, then
a measurement of “m” gives you “d”
• Standard candles: Identifiable stars for which you know “M”
![Page 35: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/35.jpg)
Determining Distances in Astronomy
• Stellar parallax• Spectroscopic parallax (main-sequence
fitting): – Remember distance modulus:
(m – M) = 5 log(d) – 5– If you know “M” for a certain type of star, then
a measurement of “m” gives you “d”
• Standard candles: Identifiable stars for which you know “M”
![Page 36: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/36.jpg)
Determining Distances in Astronomy
• Stellar parallax• Spectroscopic parallax (main-sequence
fitting): – Remember distance modulus:
(m – M) = 5 log(d) – 5– If you know “M” for a certain type of star, then
a measurement of “m” gives you “d”
• Standard candles: Identifiable stars for which you know “M”
![Page 37: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/37.jpg)
Determining Distances in Astronomy
• Stellar parallax• Spectroscopic parallax (main-sequence
fitting): – Remember distance modulus:
(m – M) = 5 log(d) – 5– If you know “M” for a certain type of star, then
a measurement of “m” gives you “d”
• Standard candles: Identifiable stars for which you know “M”
![Page 38: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/38.jpg)
Determining Distances in Astronomy
• Stellar parallax• Spectroscopic parallax (main-sequence
fitting): – Remember distance modulus:
(m – M) = 5 log(d) – 5– If you know “M” for a certain type of star, then
a measurement of “m” gives you “d”
• Standard candles: Identifiable stars for which you know “M”
![Page 39: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/39.jpg)
Example Standard Candles
• RR Lyrae variables– Pulsation period of about ½ day– Luminosity is 100 x solar luminosity
• Sun: M = +4.8; let’s call it M = +5 for simplicity• RR Lyrae: M = 0
• “Population I” Cepheid variables– Luminosities range up to 10,000 solar (M = - 5)
– (Pulsation) period-luminosity correlation
• Type Ia supernovae– Luminosity 3 x 109 solar !
![Page 40: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/40.jpg)
Example Standard Candles
• RR Lyrae variables– Pulsation period of about ½ day– Luminosity is 100 x solar luminosity
• Sun: M = +4.8; let’s call it M = +5 for simplicity• RR Lyrae: M = 0
• “Population I” Cepheid variables– Luminosities range up to 10,000 solar (M = - 5)
– (Pulsation) period-luminosity correlation
• Type Ia supernovae– Luminosity 3 x 109 solar !
![Page 41: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/41.jpg)
Example Standard Candles
• RR Lyrae variables– Pulsation period of about ½ day– Luminosity is 100 x solar luminosity
• Sun: M = +4.8; let’s call it M = +5 for simplicity• RR Lyrae: M = 0
• “Population I” Cepheid variables– Luminosities range up to 10,000 solar (M = - 5)
– (Pulsation) period-luminosity correlation
• Type Ia supernovae– Luminosity 3 x 109 solar !
![Page 42: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/42.jpg)
![Page 43: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/43.jpg)
Example Standard Candles
• RR Lyrae variables– Pulsation period of about ½ day– Luminosity is 100 x solar luminosity
• Sun: M = +4.8; let’s call it M = +5 for simplicity• RR Lyrae: M = 0
• “Population I” Cepheid variables– Luminosities range up to 10,000 solar (M = - 5)
– (Pulsation) period-luminosity correlation
• Type Ia supernovae– Luminosity 3 x 109 solar !
![Page 44: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/44.jpg)
Example Standard Candles
• RR Lyrae variables– Pulsation period of about ½ day– Luminosity is 100 x solar luminosity
• Sun: M = +4.8; let’s call it M = +5 for simplicity• RR Lyrae: M = 0
• “Population I” Cepheid variables– Luminosities range up to 10,000 solar (M = - 5)
– (Pulsation) period-luminosity correlation
• Type Ia supernovae– Luminosity 3 x 109 solar !
![Page 45: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/45.jpg)
Example Standard Candles
• RR Lyrae variables– Pulsation period of about ½ day– Luminosity is 100 x solar luminosity
• Sun: M = +4.8; let’s call it M = +5 for simplicity• RR Lyrae: M = 0
• “Population I” Cepheid variables– Luminosities range up to 10,000 solar (M = - 5)
– (Pulsation) period-luminosity correlation
• Type Ia supernovae– Luminosity 3 x 109 solar !
![Page 46: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/46.jpg)
Example Standard Candles
• RR Lyrae variables– Pulsation period of about ½ day– Luminosity is 100 x solar luminosity
• Sun: M = +4.8; let’s call it M = +5 for simplicity• RR Lyrae: M = 0
• “Population I” Cepheid variables– Luminosities range up to 10,000 solar (M = - 5)
– (Pulsation) period-luminosity correlation
• Type Ia supernovae– Luminosity 3 x 109 solar !
![Page 47: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/47.jpg)
![Page 48: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/48.jpg)
Example Standard Candles
• RR Lyrae variables– Pulsation period of about ½ day– Luminosity is 100 x solar luminosity
• Sun: M = +4.8; let’s call it M = +5 for simplicity• RR Lyrae: M = 0
• “Population I” Cepheid variables– Luminosities range up to 10,000 solar (M = - 5)
– (Pulsation) period-luminosity correlation
• Type Ia supernovae– Luminosity 3 x 109 solar !
![Page 49: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/49.jpg)
NOTE: Transient Events (in time) also occur
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NOTE: Transient Events (in time) also occur
![Page 51: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/51.jpg)
NOTE: Transient Events (in time) also occur
![Page 52: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/52.jpg)
Example Standard Candles
• RR Lyrae variables– Pulsation period of about ½ day– Luminosity is 100 x solar luminosity
• Sun: M = +4.8; let’s call it M = +5 for simplicity• RR Lyrae: M = 0
• “Population I” Cepheid variables– Luminosities range up to 10,000 solar (M = - 5)
– (Pulsation) period-luminosity correlation
• Type Ia supernovae– Luminosity 3 x 109 solar !
![Page 53: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/53.jpg)
Distance Ladder
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Shapley’s View of MW Galaxy
• Look out of the plane of the MW disk to minimize obscuration due to interstellar extinction
• Distribution of Globular Clusters not symmetric about Sun’s location
• Distances to GCs obtained using RR Lyrae variable stars as “standard candles”
![Page 55: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/55.jpg)
![Page 56: ASTR 1102-002 2008 Fall Semester](https://reader035.vdocument.in/reader035/viewer/2022062802/5681458c550346895db274ab/html5/thumbnails/56.jpg)
Stellar Populations
• Pop I
• Pop II
• Pop III
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Prominent and Obscured Objects