The Sun is the closest star to Earth and the center of our Solar System. Its gravity organizes the shape of the Solar System and influences its evolution.

Energy is generated by nuclear reactions in the Sun's core. This energy is produced across the wide range of the electromagnetic spectrum that includes visible light, infrared and other forms of radiation.

The Universe began with the Big Bang around 13.7 billion years ago and has been expanding ever since. The Solar System formed 4.6 billion years ago from clouds of interstellar dust.

The rocky planets formed closer to the Sun from more dense material, while lighter materials dominate outer Solar System objects.

We explore the Solar System primarily by analyzing different wavelengths of electromagnetic radiation collected by space and ground-based telescopes. Spectroscopy, the analysis of this light, is the fundamental tool of astrophysics. Additional information comes from evidence collected by space probes and landers and through computer simulation.

Atmospheres—their presence, absence, and composition—play a fundamental role in determining planetary characteristics.

Through advances in instrumentation, we are rapidly discovering planets in solar systems beyond our own—including some that may harbor life.

The search for extraterrestrial life begins with a search for liquid water—on which life as we know it depends. Within our Solar System, Mars is a possibility, as is Jupiter's moon Europa.