Although the light year is a
commonly used unit, astronomers
prefer a different unit called the parsec (pc). A parsec, equal to 3.26
light years, is defined as the distance at which 1 Astronomical Unit subtends an
angle of 1 second of arc (1/3600 of a degree) When we use the parsec for really
large distances, we often put a prefix in front of it - like kiloparsecs (kpc),
which are equal to 1000 parsecs - or Megaparsecs (Mpc), equal to a million
parsecs.
The Milky Way is about 1,000,000,000,000,000,000 km
(about 100,000 light years or about 30 kpc) across. The Sun does not lie near
the center of our Galaxy. It lies about 8 kpc from the center on what is known
as the Sagittarius arm of the Milky Way.
The concept of Peak Oil was first developed in the 1950's by the geologist M. King Hubert.
Answer:
A. Lava flows block a river.
D. Ice sheets leave depressions that fill with water.
E. Movement of Earth's crust creates low areas that fill with water
Explanation:
The three important physical features found along the west coast of South America is the Andes Mountains, Atacama desert, and the Lake Titicaca. Andes Mountain is the highest mountain found outside of Asia and runs along the western side of South America. The Atacama desert is a plateau found west of the Andes Mountains and the driest desert in the world. The Lake Titicaca is deep lake located on the border of Bolivia and Peru.
