Astronomy 2014 Study Guide

The Big Bang 13.7 BYA Singularity: all matter/energy/time/space in a single point Modern matter/energy/time/space did not exist as separate things Inflation made space In the first second, incredibly hot, no modern matter

Inflation A process where the distance between points in the universe increases. A process where space increases Happened quickly after the big bang Happens slowly now Caused the universe to cool As the universe cooled, allowed modern matter to form

Early Universe Composition 75% Hydrogen (1 proton) 24% Helium (2 Protons) 1% everything else No heavy elements such as Carbon, Oxygen and Iron

Nebulas Clouds of gas, or gas and dust (heavier elements) Pulled together by gravity Early versions were globular, and did not spin much Later more recent versions are spinning as they condense, and have a disc or spiral form. More recent/younger versions contain heavier elements/dust These can condense to form stars and/or solar systems

Basic Physics Time and Space are linked: At higher velocities, time slows for objects. Matter and energy are interconvertible by E=MC2. Mass and space are linked: At higher velocities, objects gain mass. Light takes time to travel. Light from further away is older. Distant objects in the universe have traveled further, and therefore what we see is older.

Basic Forces The strong atomic force can hold particles like protons and neutrons together, but only if they are very close together. The electromagnetic force can hold different charges together, and push similar charges apart, and can work over large distances. The Electromagnetic force is stronger than the Strong Atomic force over long distances, but weaker over short distances.

Atomic Structure The nucleus contains protons (positive charge) and neutrons (no charge) Electrons (negative charge) are found outside the nucleus They are held together by the attraction of opposite charges in protons and electrons. Protons and neutrons in the nucleus are held together by the strong atomic force, even if their similar charges push them apart.

Nuclear Fusion To build heavy elements, protons must be forced close together for the strong nuclear force to take hold and pull them together. Electromagnetism pushes protons apart. A very strong force must be present to force protons together. If there is enough mass, gravity can be strong enough to force protons together. This process builds heavier elements from lighter, and produces heat and light.

Stars Nebulas that are pulled together by gravity can become dense enough that gravity at the core is strong enough to start fusion. Fusion reactions at the core release energy and push matter apart. Gravity pulls matter together. The balance between fusion and gravity maintains the size. Blue is hottest, red is coolest. Larger more massive accumulations run out of hydrogen to fuse more quickly.

Main Sequence Stars These are stable stars that are converting hydrogen to helium in their cores.

Brown Dwarves These are small main sequence stars that have converted all their hydrogen into helium. They are not massive enough to have enough gravity to fuse heavier elements like helium. Gravity causes them to grow smaller, and they start to cool, becoming darker. Some of these are only somewhat larger than Jupiter.

Red Giants These form when a large main sequence star uses up its hydrogen, but there is enough gravity for fuse heavier elements. Once the easier fusion reactions have occurred, the star begins to collapse under its own gravity, until gravity is strong enough to fuse very heavy elements to form things like iron. The resulting energy released is enough to superheat the outside of the star, causing it to expand. This will happen to our sun.

Supernova In extremely large stars, once all possible fusion reactions have occurred, the star begins to collapse. If gravity is strong enough, even the heaviest elements can still fuse, all in a brief few seconds. The resulting release of energy is enough to blow the star apart. All the heaviest elements are manufactured in this way.

Black Hole These occur in the most massive stars. After fusion reactions have stopped, it begins to collapse. Although gravity may be strong enough to start new fusion reactions, gravity is enough to hold most of the star together. Once the star collapses completely, near the center the force of gravity is so strong nothing can escape, including light. There is a giant black hole at the center of our galaxy. It is what our solar system orbits.

Solar Systems Are young Form from dusty, “heavy” elements Form from rotating nebulas Take on a flat disc shape as they spin Heavy elements move to the edges of the disc Light elements (hydrogen) stay at the center The center forms a star once gravity is enough to start fusion. The edges form planets, asteroids, etc.

Planets These are large objects that orbit the sun They have enough mass that their gravity has pulled them into a spherical shape They have enough mass that they’ve attracted most nearby mass to them, clearing their orbit.

Dwarf Planets These are large objects that orbit the sun They have enough mass that their gravity has pulled them into a spherical shape They are not massive enough to have cleared their orbit.

Asteroids These are objects that orbit the sun. They are small enough that gravity has not pulled them into a spherical shape. They are mainly found in a belt between the inner and outer planets.

Meteoroids These are very small versions of asteroids.

Moons These are large, roughly spherical objects that orbit planets.

Satellites These are objects that orbit a planet of any size or shape.

Inner Planets These have dense, rocky cores and surfaces. These have thin or no atmospheres. These are relatively hot. They include (in order from the sun) Mercury Venus Earth Mars

Mercury Short year, long day. Almost no atmosphere Closest to the sun Very hot

Venus Active volcanoes Thick atmosphere Greenhouse conditions Very hot Day is longer than its year

Earth Active volcanoes Magnetic field Liquid water

Mars Thin atmosphere, used to be thicker, have liquid water No liquid water Used to have active volcanoes Relatively cold. Longer year than Earth

Outer planets Gas giants All have shorter day/spin faster All colder All have very long years.

Year Duration for Planets The closer to the sun, the shorter the year The further, the longer the year

Daily Duration for Planets Gas giants spin faster Venus has a day longer than its year.

Planetary Temperature Closer to the sun is generally hotter, further is colder. A thick atmosphere can make a planet warmer than it would otherwise be. Volcanic activity can make an atmosphere thicker. A magnetic field can protect an atmosphere.

Planetary Atmospheres Radioactive materials in a planet’s core can generate heat. Hot cores can melt rock. Melted rock can come to the surface, releasing gases to build an atmosphere. The suns heat can boil/blow off a planet’s atmosphere, reducing it over time. Spinning metals like iron at a planet’s core can produce a protective magnetic field.