* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Bright versus Nearby Stars
Formation and evolution of the Solar System wikipedia , lookup
Rare Earth hypothesis wikipedia , lookup
Astronomical unit wikipedia , lookup
Orion (constellation) wikipedia , lookup
Corona Borealis wikipedia , lookup
International Ultraviolet Explorer wikipedia , lookup
Constellation wikipedia , lookup
Canis Minor wikipedia , lookup
Aries (constellation) wikipedia , lookup
Auriga (constellation) wikipedia , lookup
Observational astronomy wikipedia , lookup
Cygnus (constellation) wikipedia , lookup
Cassiopeia (constellation) wikipedia , lookup
Perseus (constellation) wikipedia , lookup
Corona Australis wikipedia , lookup
Canis Major wikipedia , lookup
Timeline of astronomy wikipedia , lookup
Star catalogue wikipedia , lookup
Aquarius (constellation) wikipedia , lookup
H II region wikipedia , lookup
Stellar evolution wikipedia , lookup
Corvus (constellation) wikipedia , lookup
Stellar classification wikipedia , lookup
Star formation wikipedia , lookup
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. 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. 35 30 25 20 15 10 5 22 18 14 10 6 2 0 Distance, Light Years Distances to the 269 Brightest Stars 0 3, 00 0 50 0 2, 00 0 2, 50 0 1, 00 1, 0 • 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. 50 0 100 90 80 70 60 50 40 30 20 10 0 Distance, Light Years Absolute Magnitude vs Distance of the 100 Nearest Stars -10 -5 0 5 10 15 20 1 10 100 1,000 • 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. 10,000 Distance, Light Years Absolute Magnitude vs Distance of the 269 Brightest Stars -10 -5 0 5 10 15 20 1 10 100 1,000 10,000 Distance, Light Years • 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. Absolute Magnitudes of 100 Nearby Stars 25 20 15 10 5 0 • 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. 0 -1 -6 -2 2 6 10 14 18 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. 60 50 40 30 20 10 -1 0 -7 -4 -1 2 5 8 0 Hertzsprung Russell Diagram for 100 Nearby Stars -10 • 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. -5 M 0 5 10 15 20 1 2 3 4 5 6 Spectral Type 7 8 Hertzsprung Russell Diagram of 269 Bright Stars -10 • The bright stars occupy the upper high luminosity giant region of the HR diagram. • They are either -5 M 0 5 10 15 20 0 2 4 Spectral Type 6 8 – Hot main sequence stars, or – Cool giant stars Spectral Types of 100 Nearby Stars 80% • 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. Number 60% 40% 20% 0% O B A F G K M D Spectral Types of 269 Bright Stars 100 80 60 40 20 0 O B A F G K M • 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. Luminosity Class of 100 Nearby Stars 100% • There are no true giant stars with in the 25 light years around the Sun. • 97 % of nearby stars are Main Sequence dwarf stars. 75% 50% 25% 0% I II III IV IV-V V Luminosity Class of 269 Bright Stars 120 100 80 60 40 20 0 I II III IV V p • 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. 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 = 0.002 solar luminosities. Very long lived stars 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. • The 269 Brightest stars • The 100 nearest stars – 381 light years away on average – 17 light years away on average • Max Distance = 3400 light years • Min distance = 4.3 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. – Average apparent magnitude = 10 – Invisible to naked eye – 88% are cool main sequence K or M Stars. – Average absolute magnitude = 11.5 – Luminosity = 0.002 solar luminosities. – Very long lived stars