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A Comparison of the Nearest and Brightest Stars The nearest stars to the Sun are thought to represent the true distribution of stars in the disk of the.

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Presentation on theme: "A Comparison of the Nearest and Brightest Stars The nearest stars to the Sun are thought to represent the true distribution of stars in the disk of the."— Presentation transcript:

1 A Comparison of the Nearest and Brightest Stars The nearest stars to the Sun are thought to represent the true distribution of stars in the disk of the Milky Way Galaxy. To truly understand the Galaxy, these stars must be studied. The bright stars that are easily visible in the night sky are extraordinary stars that are very different from the true common stars in the Milky Way Galaxy.

2 Distance to the 100 Nearest Stars Excluding white dwarfs, there are 100 stars within 24 light years of the Sun. The closest star is 4.3 light years away. The average distance to the nearest stars is 17 light years.

3 Distances to the 269 Brightest Stars The 269 brightest stars in the sky range in distance from 4.3 light years to 3,400 light years. The average bright star is 381 light years away.

4 Absolute Magnitude vs Distance of the 100 Nearest Stars The nearest stars are generally much less luminous than the Sun. Their absolute magnitudes range from 0 to 20. The Sun’s absolute magnitude is 4.8.

5 Absolute Magnitude vs Distance of the 269 Brightest Stars The brightest stars are generally much more luminous than the Sun. Their absolute magnitudes range from -8 to 5. The Sun’s absolute magnitude is 4.8.

6 Absolute Magnitudes of 100 Nearby Stars 95% of the nearest 100 stars are less luminous than the Sun. The average nearby star has absolute magnitude 11.5, equivalent to.002 solar luminosities.

7 Absolute Magnitudes of 269 Bright Stars 95% of the brightest stars are more luminous than the Sun. The average absolute magnitude of a bright star is –1.2, equivalent to 300 solar luminosities.

8 Hertzsprung Russell Diagram for 100 Nearby Stars The nearby stars occupy the lower luminosity long-lived portion of the HR diagram. This survey does NOT include the numerous white dwarf stars in the solar neighborhood.

9 Hertzsprung Russell Diagram of 269 Bright Stars The bright stars occupy the upper high luminosity giant region of the HR diagram. They are either –Hot main sequence stars, or –Cool giant stars

10 Spectral Types of 100 Nearby Stars There are no O or B stars near the Sun. The Sun’s spectral type represents only 6% of the nearby stars. 88% of nearby stars are K & M spectral types.

11 Spectral Types of 269 Bright Stars All spectral types are represented in the bright stars. Over 1/3 of the bright stars are O & B types. Only 13% are solar-type G stars. 26% of the bright stars are K & M type.

12 Luminosity Class of 100 Nearby Stars There are no true giant stars with in the 25 light years around the Sun. 97 % of nearby stars are Main Sequence dwarf stars.

13 Luminosity Class of 269 Bright Stars All luminosity classes are represented in the bright stars. 73% are late-stage giant stars or peculiar stars. Only 27% of the bright stars are main sequence dwarf stars.

14 The Average Nearby Star The 100 nearest stars are: –17 light years away on average Min distance = 4.3 light years –Average apparent magnitude = 10 –Invisible to naked eye –88% are cool main sequence K or M Stars. –Average absolute magnitude = 11.5 –Luminosity = solar luminosities. –Very long lived stars

15 The Average Bright Star The 269 Brightest stars are: –381 light years away on average Max Distance = 3400 light years –75% are late stage giant stars –25% are young hot (most probably B) stars. –Average absolute magnitude = -1.2 –Average luminosity = 300 solar luminosities. –Short lived stars or stars near the of their evolution.

16 The 269 Brightest stars –381 light years away on average Max Distance = 3400 light years –75% are late stage giant stars –25% are hot (most probably B) stars. –Average absolute magnitude = -1.2 –Average luminosity = 640 solar luminosities. –Short lived stars or giant stars near the of their evolution. The 100 nearest stars –17 light years away on average Min distance = 4.3 light years –Average apparent magnitude = 10 –Invisible to naked eye –88% are cool main sequence K or M Stars. –Average absolute magnitude = 11.5 –Luminosity = solar luminosities. –Very long lived stars


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