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.
Earthquakes produce three types of seismic waves: primary waves, secondary waves, and surface waves. Each type moves through materials differently. In addition, the waves can reflect, or bounce, off boundaries between different layers.
Answer:
When the magma, a molten rock flows as lava at the planet's surface, the surface gets cooled after a long, this whole process cause formation of some kinds of minerals on that surface.
Explanation:
Magma and Lava both are types of molten rock. The underground molten rock is called magma while the exploded molten rock on surface is known as lava. When these rocks cools down they get solidified and form crystal rock structure. Cooled magma is called plutonic igneous rock and cooled lava is called volcanic igneous rock. These rock crystals are of different sizes and consist several minerals such as Silicon(Si), Sodium (Na), Potassium (K), Aluminium (Al), Iron(Fe), Magnesium(Mg), Calcium(Ca). Some rocks that forms minerals consist high amount of iron. The amount of minerals and elements in every rock can very depending on shape and size.
