What are the two theories about galaxy?
The two most popular theories to explain these, and other galactic phenomena, are the presence of undiscovered matter (dark matter) or the Modified Newtonian Dynamics theory, MOND (Bekenstein and Milgrom 1984), of the modification of the laws of gravity.
What are two characteristics of irregular shaped galaxies?
Irregular galaxies have no particular shape. They are among the smallest galaxies and are full of gas and dust. Having a lot of gas and dust means that these galaxies have a lot of star formation going on within them. This can make them very bright.
Why are galaxies shaped the way they are?
Astronomers believe that galaxies have spiral arms because galaxies rotate – or spin around a central axis – and because of something called “density waves.” A spiral galaxy’s rotation, or spin, bends the waves into spirals. Stars pass through the wave as they orbit the galaxy center.
What shape do galaxies have?
Galaxy classification Galaxies are classified by shape. There are three general types: elliptical, spiral, and irregular. Perhaps the most familiar kind of galaxy are spiral galaxies. They have a distinctive shape with spiral arms in a relatively flat disk and a central “bulge”.
How does galaxy look like?
Some galaxies are spiral-shaped like ours. They have curved arms that make it look like a pinwheel. Other galaxies are smooth and oval shaped. The light that we see from each of these galaxies comes from the stars inside it.
What are the 4 types of galaxies?
In 1936, Hubble debuted a way to classify galaxies, grouping them into four main types: spiral galaxies, lenticular galaxies, elliptical galaxies, and irregular galaxies.
What is the Earth’s galaxy called?
the Milky Way
What is the oldest type of galaxy?
Elliptical galaxies, such as M87, are the oldest and roundest galaxies in the universe. Astronomers think these galaxies are formed in major mergers—dramatic collisions between galaxies that result in one massive galaxy being entirely consumed by another.
What is the youngest thing in the universe?
GN-z11 is the youngest and most distant galaxy scientists have observed. This video zooms to its location, some 32 billion light-years away. GN-z11 is 13.4 billion years old and formed 400 million years after the Big Bang. Its irregular shape is typical for galaxies of that time period.
What is the rarest type of galaxy?
elliptical double-ringed galaxy
How old is a black hole?
At more than 13 billion years old, the black hole and quasar are the earliest yet seen, giving astronomers insight into the formation of massive galaxies in the early universe.
How old is our Earth?
4.543 billion years
What is the oldest planet?
At 12.7 billion years old, planet Psr B1620-26 B is almost three times the age of Earth, which formed some 4.5 billion years ago. This exoplanet, the oldest ever detected in our Milky Way galaxy, has been nicknamed “Methuselah” or the “Genesis planet” on account of its extreme old age.
Who discovered the Earth?
Eratosthenes
How did Earth get its name?
All of the planets, except for Earth, were named after Greek and Roman gods and godesses. The name Earth is an English/German name which simply means the ground. It comes from the Old English words ‘eor(th)e’ and ‘ertha’.
How was Earth created?
Formation. When the solar system settled into its current layout about 4.5 billion years ago, Earth formed when gravity pulled swirling gas and dust in to become the third planet from the Sun. Like its fellow terrestrial planets, Earth has a central core, a rocky mantle and a solid crust.