I dont under stand please exsplain more
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.
Answer:
mountain systems and fresh water
Explanation:
mountain systems are a group of mountain ranges with similarity in form, structure, and alignment that have arisen from the same cause, usually an orogeny. Take the Himalayan mountains for example.
Fresh waters are natural occurring waters except seawater and brackish water. for example they have lake Baikal,the Yangtze river etc.
Slabs of ocean floor return to the mantle in subduction zones.Description<span>
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