1. The Milky Way Galaxy
Comprehend the Milky Way Galaxy and the Sun’s Place In It
Comprehend the Four Components of the Galaxy
Comprehend Other Planetary Systems
Comprehend Black Holes
Comprehend the center of the Milky Way Galaxy

2. Lesson Overview The Milky Way Galaxy and the Sun’s Place In It
The Four Components of the Galaxy
Other Planetary Systems
Black Holes
The Center of the Milky Way Galaxy

3. The Milky Way and our Sun
The Sun is one of about 200 billion stars that make up the Milky Way Galaxy
Diameter ranges from about 100,000 to about 160,000 light-years

4. The Shape of the Galaxy
Stars are arranged in a wheel-shaped disk that circles around a bulging center
Sun is about one-third to one-half of the way out from the galaxy’s center

5. Andromeda, a Galaxy Similar to the Milky Way
Almost everything you can see in the sky is in the Milky Way Galaxy
Andromeda is visible in the autumn sky as a fuzzy patch

6. The Four Components of a Galaxy
The Galaxy Disk
A galaxy disk is the large, flat part of a spiral galaxy, rotating around its center
Contains individual stars, clusters of stars, and almost all the gas and dust found in the galaxy

7. The Four Components of a Galaxy
The Central Region of the Galaxy
The nuclear bulge is a spiral galaxy’s central region
Milky Way Galaxy’s nuclear bulge is about 2,000 parsecs, or 6,500 light-years, in diameter
Packed more densely with stars, dust, and gas than any other part of the galaxy

8. The Four Components of a Galaxy
The Halo
Galaxy’s halo is the outermost part of a spiral galaxy, nearly spherical and lying beyond the spiral
A globular cluster is a spherical group of up to hundreds of thousands of stars, found primarily in a galaxy’s halo

9. The Four Components of a Galaxy
The Galactic Corona
Beyond the galaxy’s halo lies the galactic corona, or outer halo
Scientists don’t know what the corona consists of, but think it may include small black holes, cool dwarf stars, large numbers of neutrinos, and other exotic particles

10. Other Planetary Systems
The Obstacles to Discovering Exoplanets:
It’s hard to see planets around other stars by direct observation
In the infrared, the brightness of a planet peaks, while that of a star declines. This makes it easier to spot

11. Black Holes
A black hole is an object whose escape velocity exceeds the speed of light
Escape velocity is the speed at which an object must travel to “escape” a star’s gravity

12. Black Holes How Scientists Detect Black Holes:
Because the gravitational field near a black hole would be so strong, any matter nearby would orbit very fast
This hot material would radiate energy
It would appear as an X-ray source

13. The Center of the Milky Way Galaxy
To observe the galactic nucleus, scientists use wavelengths in the infrared/radio part of the spectrum or in X-rays and gamma rays
The massive-black-hole hypothesis seems to be the best explanation for the energy source in the Milky Way Galaxy and other similar galaxies

14. The Milky Way Galaxy
Comprehend the Milky Way Galaxy and the Sun’s Place In It
Comprehend the Four Components of the Galaxy
Comprehend Other Planetary Systems
Comprehend Black Holes
Comprehend the center of the Milky Way Galaxy