Getting a cold is like building the chemical elements in nucleosynthesis.

The deuterium and lithium-7 in distant quasars and in the interstellar medium suggests that the Universe is open.

Elliptical galaxies contain more gas, dust, and young stars than do Sa galaxies.

A center or an edge of the Universe would be a special place, contradicting the cosmological principle.

Isotropic is the same as homogeneous.

For a galaxy to be active, the supermassive black hole needs to have matter flow into it.

Old stars are poor in heavy elements because there were very few previous generations of stars before the old stars formed.

The elements hydrogen and helium were made during the first few minutes after the big bang.

The center of our galaxy is located in the direction of the constellation of Orion.

Almost every celestial object we see in the sky on a dark, clear night is within the Milky Way galaxy.