Astronomy 2

geocentric

model of the solar system in which the Earth is in the center of the universe

heliocentric

model of the solar system with the Earth revolving around the Sun

Stonehenge

is the site of several henges, or ditches surrounded by banks, in England

Henges

ditches surrounded by banks

Mayan Civilization

flourished in present-day Mexico, Belize, Guatemala, El Salvador, and Honduras from about 2600 BCE, with its golden age spanning 300-900 CE

Aztec Civilization

thrived from between 1100 and 1521 CE, but descendants of the Aztecs still live and practice certain cultural traditions in Mexico

Century (Aztec)

a 52-year cycle in the Aztec calendar

Space Race

a competition between the US and USSR as to who could do what first in human space exploration

FAI

the international governing body overseeing aerospace records

re-entry

the moment when a space craft comes back into Earth’s atmosphere

Deep Space Network (DSN)

an international network of spacecraft communication services

rovers

space exploration vehicles designed to move about the surface of a planet

planetary system

a system of planets orbiting a central star

Solar System

a planetary system that includes the Sun, the planets, and many other smaller objects

solar nebula

the cloud of gas and dust from which the Sun and the rest of the Solar System was formed

planetesimals

rocky objects in space from which planets are created through the process of accretion

protoplanetary disk (proplyd)

the early stage of the development of a planet when it is growing because of collisions with planetesimals

extrasolar planets

planets located outside of our Solar System

protosun

the early, gaseous stage of the Sun’s formation

Mercury

first planet and 3.2 light minutes away from the Sun

Venus

second planet and 6 light-minutes away from the Sun; of all the terrestrial planets, has the densest atmosphere

retrograde rotation

when a celestial body spins in the opposite direction that it orbits the Sun; Uranus also does this

Terrestrial planets

highly dense and rock planets nearest to the Sun

Earth

Third planet and 8.3 light-minutes from the Sun; only planet currently known to sustain life

Prograde rotation

The counter-clockwise spin of a planet or moon as seen from above the planet’s north pole; rotation is in the same direction as the Sun’s rotation.

Earth’s atmosphere layers

troposphere, stratosphere, mesosphere, thermosphere, and exosphere

Jupiter

the largest and most massive of the planets

Juno

a spacecraft that conducts in-depth examinations of Jupiter’s chemistry, atmosphere, interior structure, and magnetosphere

Great Red Spot

A giant storm on Jupiter that has been observed since the 1800s

Little Red Spot

A spot comprised of three smaller storms on Jupiter

Gossamer ring

a third, transparent ring of Jupiter

Galilean satellites

Jupiter’s four largest moons: Io, Europa, Ganymede, and Callisto

Saturn

This planet is the sixth planet from the Sun, but it is the second largest, behind Jupiter

Titan

Saturn’s giant moon that has a thick atmosphere that is regarded by scientists as one of the most complex chemical environments in our solar system

Enceladus

Saturn’s moon that contains hydrogen in gas form and where scientists believe is the most likely home to life outside Earth

Centripetal force

a "center-seeking" net force acting perpendicular to an object's velocity, causing it to move in a curved or circular path

Uranus

The first planet discovered by a telescopic search of the universe; 7th planet in order

Neptune

The eighth farthest planet from the Sun

Turbulent convection

the chaotic transport of heat, momentum, and matter within celestial bodies, driven by buoyancy

Differential rotation

the phenomenon where different parts of a non-solid, rotating body—such as a star, gas giant, or accretion disk—move at different angular velocities

Orbital resonance

occurs when orbiting bodies (like planets or moons) exert regular, periodic gravitational influences on each other, usually because their orbital periods are related by a ratio of small integers

Volatiles

chemical elements or compounds with low boiling points that easily vaporize or sublime in planetary atmospheres and surfaces

Great Dark Spot

This storm on Neptune was as large as Earth, had winds of almost 750 mph, and rotated counter-clockwise

Triton

The largest of Neptune’s moons

Retrograde orbit

When a celestial body orbits opposite the direction of a planet’s orbit; Neptune’s Triton does this

Pluto

a dwarf planet that was classified as a planet from 1930 to 2006

Kuiper Belt

the region of space beyond Neptune which is similar to the asteroid belt between Mars and Jupiter

Eris

a dwarf planet found in the Kuiper Belt that is slightly larger than Pluto

Dwarf planets

celestial bodies that orbit the sun, have a relatively round shape, not a moon, but have not cleared out the area around their orbits

IAU

International Astronomical Union that is responsible for naming celestial bodies and defining astronomical constants.

What governing body reclassified Pluto as a dwarf planet?

IAU

Sidereal vs solar day

A sidereal day is a planet's true rotation period relative to distant stars, while a solar day is the time for the Sun to return to the same meridian

Sun

the center star of our Solar System, consisting of plasma and magnetic fields

Thermal columns

convective plumes in the Sun's interior that transport energy from deeper layers to the surface

Solar winds

streams of charged particles that blow out matter and energy

Core

the interior or center part of the Sun

Radiative zone

Located about one-third of the way from the surface of the Sun to the core; the plasma here is relatively calm compared to the surface of the Sun, but the visible light is much greater

Convective zone

The outer layer of the Sun before the atmosphere starts; it extends down from the surface to about 200,000 kilometers.

Photosphere

The Sun’s visible surface, or the lowest layer of the Sun’s atmosphere

Chromosphere

The middle layer of the Sun’s atmosphere; this layer is typically invisible from Earth, but its reddish color can be seen during a total solar eclipse

Corona

The outermost layer of the Sun’s atmosphere; larger than the Sun itself in volume

Nuclear fusion

occurs when two atomic nuclei combine, or "fuse," to form one heavier nucleus

Nuclear fission

process where the nucleus of an atom splits into smaller parts

Gravitational equilibrium

the balance of gravity pulling inward at the same time that pressure is pushing out

Proton-proton chain reaction

energy is created through this process of nuclear fusion

Deuterium nucleus

has one proton and one neutron

Neutrinos

subatomic particles with very little mass and no charge. Most common particles and can be found in radioactive decay and nuclear fusion reactions.

Positron

antimatter counterpart of an electron, featuring the same mass but a positive charge

Gamma ray

the highest-energy, shortest-wavelength, and most penetrating electromagnetic radiation

Newton’s law of universal gravitation

objects in space are attracted to each other with a force equal to the product of their masses, divided by the square of the distance between their centers

Kepler’s first law of planetary motion

Planets and moons orbit in elliptical, rather than circular, paths

Kepler’s second law of planetary motion

Explains why planets move faster when closer to the Sun

Kepler’s third law of planetary motion

The time a planet/satellite takes to make one orbit is proportional to its orbit size

Angular momentum

a measure of the "amount of rotation" an object has, taking into account its mass, shape, and speed of spinning; it is the tendency of a spinning object to keep spinning

Newton’s first law of motion

An object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced external force (Law of Inertia)

Newton’s third law of motion

For every action force, there is an equal and opposite reaction force

Newton’s second law of motion

force equals mass times acceleration; the more force applied to an object, the more it accelerates, but the more mass an object has, the harder it is to accelerate

Solar weather (solar activity)

disturbances on the Sun’s surface as energy from the core moves outward

Sunspots

cooler than the other areas of the Sun's surface, making the sunspots appear less bright or even dark; but have stronger magnetic fields

Solar prominences (filaments)

loops of trapped gas on the Sun’s surface

Sunspot cycle

a pattern of solar activity where the average number of sunspots gradually increases and decreases

Solar maximum and solar minimum

the times in the sunspot cycle when there are the most and fewest sunspots on average, respectively

Two main parts of a sunspot

umbra and penumbra

Solar granules

convection cells covering the Sun's photosphere, acting as the surface manifestation of heat rising from the interior

Coronal mass ejection

a large "bubble" of charged particles and gas from the corona that travels out from the Sun

Solar flares

magnetic storms on the surface of the Sun that create sudden and intense eruptions of charged particles and X-rays into space

Halo event

occurs when a coronal mass ejection is directed straight towards or away from the Earth; the CME looks like it forms a halo around the Sun

Solar eclipse

happens when the Moon passes between the Sun and Earth and blocks the Sun

Permian-Triassic extinction

Called the “Great Dying” and “the mother of all mass extinctions,” it was the most catastrophic of all the extinction events, with over 90 percent of the ocean’s species lost and up to 70 percent of the land mammal, insect, reptile, and plant species going extinct.

Comets

mixtures of frozen gases, rocks, and dust, and they can be the size of a small town

Halley’s Comet

Unique comet because it is visible to the naked eye each time it passes within the inner solar system. It can next be seen from Earth in 2061.

Oort Cloud

an area where there is a collection of comets; it is thought to be a spherical region that is located 100,000 AU from the Sun

Plasma tail (aka ion tail; gas tail)

gas escaping from the coma of a comet

Dust tail

dust escaping from the coma of a comet

Near Earth Objects (NEOs)

Asteroids or comets that intersect with Earth's orbit

Asteroid belt

area between Mars and Jupiter where thousands of asteroids orbit

Asteroids

small, rocky fragments mostly composed of rocks and metals, but some also contain a dark, carbon material. These fragments were left over from when the Solar System was created and most of them orbit between the Sun and Mars and Jupiter.

Trojan asteroids

Asteroids that share an orbit with Jupiter

Two planetary regions of the solar system

Inner solar system; outer solar system

Meteoroids

pieces of rock and other materials present in the solar system