Nats Exam

Front 1

Solstices

Back 1

an astronomical event that happens twice each year. the Sun's apparent posistion in the sky reaches its northern most or southern most extremes.

Front 2

Equninoxes

Back 2

An equinox occues twice a year, when the tilt of the earth's axis is inclined neither away from nor towards the sun, the center of the Sun being in the same plan as the Earth's equator

Front 3

Precession

Back 3

is a change in the orentation of the roatation axis of a rotating body. Occurs on earth every 25,800 years.

Front 4

F= m x a

Back 4

N = kg x m/s^2

Front 5

Kepler's Laws (1)

Back 5

The plants travel in elliptical paths with the sun at one foci.

Front 6

Kepler's Laws (2)

Back 6

A planet sweeps out qual areas in equal times

Front 7

Kepler's Laws (3)

Back 7

The square of the period is proportional to the cube of the distance.

Front 8

Newton's Laws

Back 8

Because gravity is inversely proportional to the square of the distance, three types of orbits are possible: Ellipses (planets), parabolas (comets, Hyperbolas (escape)

This occurs because the gravity is a central force.

This is a consequence of the fact that gravity is an inverse square law

Front 9

When are Keplers Laws exact?

Back 9

Only if 2 bodies are involved

Front 10

Velocity

Back 10

the rate of change over a distance., meters/seconds

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Acceleration

Back 11

the rate of change of velocity, meters/seconds squared

Front 12

Diffraction

Back 12

occurs when a wave encounters an obstacle. It is the bending of wave around small obstacles and the spredding out of waves past small openings

Front 13

F=GMm/r^2

Back 13

Newton= G x kg x kg/m^2

Front 14

Solar Constant

Back 14

he total radiation energy received from the Sun per unit of time per unit of area on a theoretical surface perpendicular to the Sun’s rays and at Earth’s mean distance from the Sun

Front 15

Black Body radiation

Back 15

a black body emits a temperature-dependent spectrum of light. This thermal radiation from a black body is termed black-body radiation

Front 16

Entropy

Back 16

microscopic disorder within the system. It is defined by the second law of thermodynamics.

Front 17

Stephan's Law

Back 17

the total power P radiated from one square meter of black surface at temperature T goes as the fourth power of the absolute temperature:

Front 18

E= Mc squared

Back 18

Units- Joules = kilograms mutiplied by the speed of light
(meters/seconds squared)

Front 19

Main Sequence

Back 19

is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. All main sequence stars are in hydrostatic equilibrium, where outward thermal pressure from the hot core is balanced by the inward gravitational pressure from the overlying layers

Front 20

Stellar Magnitudes

Back 20

Stellar magnitude is measure of the brightness of a star or other celestial body. The brighter the object, the lower the number assigned as a magnitude

Front 21

Absolute Magnitude

Back 21

the apparent magnitude that a star would have if it were (in our imagination) placed at a distance of 10 parsecs (which is 32.6 light years) from the Earth.

Front 22

Diffraction Gratings

Back 22

an optical component with a periodic structure, which splits and diffracts light into several beams travelling in different directions. The directions of these beams depend on the spacing of the grating and the wavelength of the light so that the grating acts as the dispersive element

Front 23

Electronmagnetic Radiation

Back 23

s a phenomenon that takes the form of self-propagating waves in a vacuum or in matter. It comprises electric and magnetic field components, which oscillate in phase perpendicular to each other and perpendicular to the direction of energy propagation.

Examples: X-Rays, UV rays

Front 24

Main Sequence

Back 24

is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. All main sequence stars are in hydrostatic equilibrium, where outward thermal pressure from the hot core is balanced by the inward gravitational pressure from the overlying layers

Front 25

Stellar Magnitudes

Back 25

Stellar magnitude is measure of the brightness of a star or other celestial body. The brighter the object, the lower the number assigned as a magnitude

Front 26

Absolute Magnitude

Back 26

the apparent magnitude that a star would have if it were (in our imagination) placed at a distance of 10 parsecs (which is 32.6 light years) from the Earth.

Front 27

Diffraction Gratings

Back 27

an optical component with a periodic structure, which splits and diffracts light into several beams travelling in different directions. The directions of these beams depend on the spacing of the grating and the wavelength of the light so that the grating acts as the dispersive element

Front 28

Electronmagnetic Radiation

Back 28

s a phenomenon that takes the form of self-propagating waves in a vacuum or in matter. It comprises electric and magnetic field components, which oscillate in phase perpendicular to each other and perpendicular to the direction of energy propagation.

Examples: X-Rays, UV rays

Front 29

Absorption Lines

Back 29

A dark line in a continuous spectrum that corresponds to the absorption of light, or some other form of electromagnetic radiation, at a well-defined wavelength.

Front 30

Stellar Spectral Types

Back 30

he category to which a star is assigned according to the characteristics of its spectrum.

Each class is characterized by the appearance of certain types of spectral lines and is further subdivided into 10 sub-classes numbered from 0 to 9. The Sun, for example, is assigned the spectral class G2 in the modern Harvard classification, corresponding to a surface temperature of about 5,700°C. Other spectral characteristics, such as the presence of emission lines, are indicated by an additional small letter placed after the spectral type

Front 31

Hertzsprung-Russell Diagram

Back 31

s a scatter graph of stars showing the relationship between the stars' absolute magnitudes or luminosity versus their spectral types or classifications and effective temperatures. Hertzprung-Russell diagrams are not pictures or maps of the locations of the stars. Rather, they plot each star on a graph measuring the star's absolute magnitude or brightness against its temperature and color.

Front 32

Parallax

Back 32

s an apparent displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines

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Binary Stars

Back 33

s a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star.