Space Exploration and Astronomy

Astronomy is the broader study of celestial objects, space, and the physical universe as a whole. Astrophysics is a branch of astronomy that specifically applies the principles of physics and chemistry to understand the nature of celestial bodies and phenomena.

A light-year is the distance that light travels in one Earth year, approximately 9.46 trillion kilometers (5.88 trillion miles). It is used because distances in space are so vast that kilometers or miles become unwieldy.

Stars like our Sun are primarily composed of hydrogen (about 75%) and helium (about 24%), with trace amounts of heavier elements.

Stars are born in nebulae (gas and dust clouds), then enter the main sequence phase (like our Sun). Their subsequent evolution depends on mass: smaller stars become red giants and then white dwarfs, while massive stars become red supergiants, explode as supernovae, and end as neutron stars or black holes.

A black hole is a region of spacetime where gravity is so strong that nothing, not even light, can escape. They typically form from the gravitational collapse of very massive stars at the end of their life cycle, after a supernova explosion.

The Hubble Space Telescope has revolutionized astronomy by providing unprecedentedly clear images of the universe from above Earth's atmosphere, allowing for groundbreaking discoveries about galaxies, nebulae, exoplanets, and the expansion of the universe.