Astrobiology or Biological Universe - Astrobiology is the branch of Astronomy dedicated to the study of the origins and evolution of life in the universe. Using chemistry, biology, physics, geology and astronomy, Astrobiology investigates the cosmic environments that could potentially generate life forms, in the past or in the future. It is also known by the terms bioastronomy, exobiology or exo-paleontology.
History of Astronomy - Astronomy is the oldest of the natural sciences, dating back to antiquity, with its origins in the religious, mythological, and astrological practices of pre-history: vestiges of these are still found in astrology, a discipline long interwoven with public and governmental astronomy, and not completely disentangled from it until a few centuries ago in the Western World (see astrology and astronomy). Early astronomy involved observing the regular patterns of the motions of visible celestial objects, especially the Sun, Moon, stars and naked eye planets.
Ancient astronomers were able to differentiate between stars and planets, as stars remain relatively fixed over the centuries while planets will move an appreciable amount during a comparatively short time.
Solar system - Nearly 5 billion years old, the Solar System is made up of celestial bodies orbiting around the central Sun and bounded to it by gravity. The celestial objects consist of eight planets, a handful of so-called dwarf planets and its more than 170 Moons, gas, dust, thousands of comets and asteroids. The eight planets are divided in four Inner Planets and four Outer Planets. The Inner or terrestrial planets are Mercury, Venus, Earth and Mars and are composed mainly of rock and metal. The Outer Planets or Gas Giants are Jupiter, Saturn, Uranus and Neptune. They are composed mostly of hydrogen and helium and are considerably bigger than the terrestrials.
Stars and Planets - Stars make their own light, just like our sun (the sun is a star — the closest star to Earth). But the stars are very, very far away from our solar system so they appear to be very tiny to us, even though up close they are large. The planets are much closer, inside our solar system
Stellar Evolution - Stellar evolution is the process by which a star changes over the course of time. Depending on the mass of the star, its lifetime can range from a few million years for the most massive to trillions of years for the least massive, which is considerably longer than the age of the universe.
Interstellar medium - The interstellar medium (ISM) is the matter that exists in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstellar space and blends smoothly into the surrounding intergalactic space.
Cosmology - Theoretical and Observational - Using elements of the practical observation associated to mathematical and physical theoretical calculation, Cosmology is the area of Astronomy dedicated to the understanding of the Universe. Among the issues analyzed are the origins of the universe, the cosmic expansion and contraction, Big Bang, Kinematic and form of the universe(s).
High Energy Astrophysics - High Energy Astrophysics explores energetic events in the Universe with energies extending from the far UV through the keV X-rays and into the Y-ray band.
BigBang Universe - The Big Bang Theory is the leading explanation about how the universe began. At its simplest, it talks about the universe as we know it starting with a small singularity, then inflating over the next 13.8 billion years to the cosmos that we know today.
Parallel Universe - The multiverse is a theory in which our universe is not the only one, but states that many universes exist parallel to each other. These distinct universes within the multiverse theory are called parallel universes. A variety of different theories lend themselves to a multiverse viewpoint.
Alien life on Earth
Black holes - A black hole is a concentration of mass in a point of the universe where the gravitational force is so strong that prevents anything to escape, including light. The name comes from its complete absorption of matter and energy, with no reflection, like a perfect blackbody.
Life beyond the Solar system (Exoplanet) - The hole is 10 times the size of Earth's orbit around the Sun and probably caused by the planet clearing a space in the dust as it orbits the star. Exoplanets are planets beyond our own solar system. Thousands have been discovered in the past two decades, mostly with NASA's Kepler space telescope.
Galactic Astronomy - Galaxies are gigantic systems of stars and interstellar matter of dust and gas, dark matter, black holes, quasars and all kinds of celestial bodies. They are typically consisted of several million or trillion stars and stellar remnants, separated by millions of light years distance and gravitationally bounded. Traditionally classified according to their shape, the most common types of galaxies are the elliptical and the spiral galaxies.
Dark matter and Dark energy - More is unknown than is known. We know how much dark energy there is because we know how it affects the universe's expansion. Other than that, it is a complete mystery. But it is an important mystery. It turns out that roughly 68% of the universe is dark energy. Dark matter makes up about 27%. The rest - everything on Earth, everything ever observed with all of our instruments, all normal matter - adds up to less than 5% of the universe. Come to think of it, maybe it shouldn't be called "normal" matter at all, since it is such a small fraction of the universe.