Final Exam

Front 1

Photosphere

Back 1

The visible surface of the Sun, lying just above the uppermost layer of the Sun's interior, and just below the chromosphere.

Front 2

Convection Zone

Back 2

Region of the Sun's interior, lying just below the surface, where the material of the Sun is in constant convection motion. This region extends into the solar interior to a depth of about 20,000 km.

Front 3

Granulation

Back 3

Molted appearance of of the solar surface, caused by rising (hot) and falling (cool) material in convective cells just below the photosphere.

Front 4

Corona

Back 4

1) The tenuous outer atmosphere of the Sun, which lies just above the chromosphere and, at great distances, turns into solar wind.

2) One of the numerous large, roughly circular regions on the surface of Venus,thought to have been caused by material causing the planet's crust to bulge outward.

Front 5

Sunspot Cycle

Back 5

The fairly regular pattern that the number and distribution of sunspots follows, in which the average number of spots reaches a maximum every 11 years or so, then fall off to almost zero.

Front 6

Flares

Back 6

Explosive event occurring in or near an active region on the Sun.

Front 7

Law of Conservation of Mass and Energy

Back 7

A fundamental law of modern physics that states that the sum of mass and energy must always remain constant in any physical process. In fusion reactions, the lost mass is converted into energy, primarily in the form of electromagnetic radiation (photons of light).

Front 8

Core

Back 8

1) The central region of Earth, surrounded by the mantle.

2) the central region of any planet or star.

Front 9

Luminosity

Back 9

One of the basic properties used to characterize stars, luminosity is defined as the total energy radiated by a star each second, at all wavelengths.

Front 10

Chromosphere

Back 10

The Sun's lower atmosphere, lying just above the visible atmosphere (Photosphere).

Front 11

Solar Wind

Back 11

An outward flow of fast-moving charges particles from the Sun.

Front 12

Solar Cycle

Back 12

The 22 year period that is needed for both the average number of Sunspots and the Sun's magnetic polarity to repeat themselves. The Sun's polarity reverses on each new 11-year Sunspot cycle.

Front 13

Coronal Mass Ejections

Back 13

Giant magnetic "bubble" of ionized gas that separates from the rest of the solar atmosphere and escapes into interplanetary space.

Front 14

Radiation Zone

Back 14

Region of the Sun's interior where extremely high temperatures guarantee that the gas is completely ionized. Photons only occasionally interact with electrons, and travel through the region with relative ease.

Front 15

Helioseismology

Back 15

The study of conditions far below the Sun's surface through the analysis of internal "sound" waves that repeatedly cross the solar interior.

Front 16

Transition Zone

Back 16

The region of rapid temperature increases that separates the Sun's chromosphere from the corona.

Front 17

Sunspots

Back 17

An Earth-sized dark blemish found on the surface of the Sun. The dark color of the sunspot indicates that it is a region of lower temperature than its surroundings.

Front 18

Prominences

Back 18

Loop or sheet of glowing gas ejected from an active region on the solar surface, which then moves through the inner parts of the corona under the influence of the Sun's magnetic field.

Front 19

Coronal Holes

Back 19

Vast region of the Sun's atmosphere where the density of matter is about 10 times lower than average. The gas there streams freely into space at high speeds , escaping the Sun completely.

Front 20

Parsec

Back 20

The distance at which a star must lie in order for its measured parallax to be exactly 1 arc second. Equivalent to 206,000 AU.

Front 21

White Dwarfs

Back 21

A dwarf with sufficiently high surface temperature that it glows white.

Front 22

Spectroscopic Parallax

Back 22

Method of determining the distance to a star by measuring the star's temperature and then determining its absolute brightness by comparing it with a standard Hertzsprung-Russel diagram. The absolute and apparent brightness of the star give the star's distance from Earth.

Front 23

Spectroscopic Binary

Back 23

A binary-star system that appears as a single star from Earth, but whose spectral lines show back-and-forth Doppler shifts as two stars orbit one another.

Front 24

21-centimeter-radiation

Back 24

Radio emission emitted when an electron in the ground state of a hydrogen atom flips its spin to become anti-parallel to the spin of the proton in the nucleus.

Front 25

Zero-Age Main Sequence

Back 25

The region on the Hertzsprung Russel diagram, as predicted by theoretical models, where the stars are located at the onset of nuclear burning in their cores.

Front 26

Star Cluster

Back 26

A grouping of anywhere from a dozen to a million stars that formed at the same time from the same clouds of interstellar gas. Are important because they aid our understanding of stellar evolution because, within one of these, stars are all roughly around the same age and chemical composition and lie at roughly the same distance from Earth.

Front 27

Photometry

Back 27

Branch of observational astronomy in which the brightness of a source is measured through each of a set of standard filters.

Front 28

H-R Diagram

Back 28

A plot of luminosity against temperature (or spectral class) for a group of stars.

Front 29

Binary Star Systems

Back 29

An system that consists of two stars in orbit around their common center of mass, held together by their mutual gravitational attraction. Most stars reside in one of these systems.

Front 30

Eclipsing Binary

Back 30

Rare binary-star system that is aligned in such a way that from Earth we observe one star passing in front of the other, eclipsing the other star.

Front 31

Evolutionary Track

Back 31

A graphical representation of a star's life as a path on the Hertzsprung-Russel diagram.

Front 32

Brown Dwarfs

Back 32

Fragments of collapsing gas and dust that did not contain enough mass to initiate core nuclear fusion. Such an object is then frozen somewhere along its pre-main-sequence contraction phase, continually cooling into a compact dark object. Because of their small size and low temperature, these are extremely hard to detect observationally.

Front 33

Open Clusters

Back 33

Loosely bound collection of tens to hundreds of stars, a few parsecs across, generally found in the plane of the Milky Way.

Front 34

Spectral Classes

Back 34

Classification scheme, based on the strength of stellar spectral lines, which is an indication of the temperature of a star.

Front 35

Main Sequence

Back 35

Well defined band on the Hertzsprung-Russell diagram on which most stars are found, running from the top-left of the diagram to the bottom-right.

Front 36

Visual Binary

Back 36

A binary-star system in which both members are resolvable from Earth.

Front 37

Emission Nebulae

Back 37

A glowing cloud of hot interstellar gas. The gas glows as a result of one or two nearby young stars which ionize the gas. Since the gas is mostly hydrogen, the emitted radiation radiation falls predominately in the red region of the spectrum, because of the hydrogen-alpha emission line.

Front 38

Protostar

Back 38

Stage in star formation when the interior of a collapsing fragment of gas is sufficiently hot and dense that it becomes opaque to its own radiation. This is at the center of this fragment.

Front 39

Bipolar Flows

Back 39

Jet of material propelled from a protostar perpendicular to the surrounding protostellar disk.

Front 40

Globular Clusters

Back 40

Tightly bound, roughly spherical collection of hundreds of thousands, and sometimes millions, of stars spanning about 50 parsecs.Are distributed in the halos around the Milky way and other galaxies.

Front 41

Subgiant Branch

Back 41

The section of the evolutionary track of a star corresponding to changes that occur just after hydrogen depleted in the core, and core hydrogen burning ceases. Shell hydrogen burning heats the outer layers of the star, which causes a general expansion of the stellar envelope.

Front 42

Helium Flash

Back 42

An explosive event in the post-main-sequence evolution of a low mass star. When this begins in a dense stellar core, the burning is explosive in nature. It continues until the energy released is enough to expand the core, at which point the star achieves stable equilibrium again.

Front 43

Planetary Nebula

Back 43

The ejected envelope of a red-giant star, spread over a volume roughly the size of our solar system.

Front 44

Nova

Back 44

A star that suddenly increases in brightness, often by a factor as much as 10,000, then slowly fades back to its original luminosity. The result of an explosion on the surface of a white-dwarf star, caused by matter falling onto its surface from the atmosphere of a binary companion.

Front 45

Carbon-Detonation Supernova

Back 45

One possible death of a star. A white dwarf of a binary-star system can accrete enough mass that it cannot support its own weight. The star collapses and temperatures become high enough for carbon fusion to occur. Fusion begins throughout the white dwarf almost simultaneously and an explosion results. Also called a Type I supernova.

Front 46

Pulsar

Back 46

Object that emits radiation in the form of rapid pulses with a characteristic pulse period and duration. Charged particles, accelerated by the magnetic field of a rapidly rotating neutron star ,flow along the magnetic field lines , producing radiation that beams outward as the star spins on its axis.

Front 47

Schwarzschild Radius

Back 47

The distance from the center of an object such that, if all the mass were compressed within that region, the escape speed would equal the speed of light. Once a stellar remnant collapses within this radius, light cannot escape and the object is no longer visible.