The celestial sphere appears to rotate around Earth once in each 24-hour period. In fact, it is actually Earth that is rotating.

*The positions of objects on the celestial sphere are described by specifying their right ascension (in time units) and declination (in angular measure).

The period of the Moon’s revolution about the Earth with respect to the stars.

This true orbital period is equal to about 27.32 days.

The period of revolution of the Moon with respect to the Sun; the length of one cycle of lunar phases. Also called the lunar month. 

the synodic month is equal to about 29.53 days

An eclipse of the Moon by the Earth; a passage of the Moon through the Earth’s shadow. (Chapter 3)

 The angle between the plane of Earth’s orbit and the plane of the Moon’s orbit is about 5°

Eclipses can occur only if the line of nodes is pointed toward the Sun and at the same time, the Moon lies on or very near the line of nodes

An eclipse of the Sun by the Moon; a passage of the Earth through the Moon’s shadow. (Chapter 3)

a solar eclipse can occur only at new moon

Eclipses can occur only if the line of nodes is pointed toward the Sun and at the same time, the Moon lies on or very near the line of nodes

The line where the plane of the Earth’s orbit intersects the plane of the Moon’s orbit. (Chapter 3)

Eclipses can occur only if the line of nodes is pointed toward the Sun and at the same time, the Moon lies on or very near the line of nodes

the period when the Moon is completely within Earth’s umbra

can last for as long as 1 hour and 42 minutes.

when the solar disk is blocked by the Moon and only the solar corona is visible

totality never lasts for more than 7½ minutes

The interval between successive passages of the Sun through the same node of the Moon’s orbit. (Chapter 3)

It takes 346.6 days to move from one alignment of the line of nodes pointing toward the Sun to the next identical alignment

An Earth-centered theory of the universe. (Chapter 4)

A Merry-Go-Round Analogy

The apparent westward motion of a planet with respect to background stars. (Chapter 4)

 the planet will seem to stop and then back up for several weeks or months

The definitive version of the geocentric cosmogony of ancient Greece. (Chapter 4)

contains epicycle and deferent

The configuration of an inferior planet at its greatest angular distance east of the Sun. (Chapter 4, Chapter 11)

 Mercury or Venus is visible after sunset (as far east of the sun as possible)

The configuration of an inferior planet at its greatest angular distance west of the Sun. (Chapter 4, Chapter 11)

Mercury or Venus is as far west of the Sun as it can possibly be.

The configuration when an inferior planet is between the Sun and Earth. (Chapter 4)

and it is moving from the evening sky into the morning sky

The configuration of a planet being behind the Sun as viewed from the Earth. (Chapter 4)

when the planet is on the opposite side of the Sun, it is moving back into the evening sky.

The configuration of a planet when it is at an elongation of 180° and thus appears opposite the Sun in the sky. (Chapter 4)

At this point the planet is in the part of the sky opposite the Sun and is highest in the sky at midnigh

This is also when the planet appears brightest, because it is closest to us

The geometric arrangement of a planet in the same part of the sky as the Sun, so that the planet is at an elongation of 0°. (Chapter 4)

it is above the horizon during the daytime and thus is not well placed for nighttime viewing.

[image]

P = inferior planet’s sidereal period

E = Earth’s sidereal period = 1 year

S = inferior planet’s synodic period

[image]

P = superior planet’s sidereal period

E = Earth’s sidereal period = 1 year

S = superior planet’s synodic period

The statement that each planet moves around the Sun in an elliptical orbit with the Sun at one focus of the ellipse. (Chapter 4)

The semimajor axis a of a planet’s orbit is the average distance between the planet and the Sun.

The point in its orbit where a planet or comet is nearest the Sun.

(Chapter 4)

 A planet moves most rapidly when it is nearest the Sun

The point in its orbit where a planet is farthest from the Sun. (Chapter 4)

a planet moves most slowly when it is farthest from the Sun

The statement that a planet sweeps out equal areas in equal times as it orbits the Sun; also called the law of equal areas. (Chapter 4)

A relationship between the period of an orbiting object and the semimajor axis of its elliptical orbit. (Chapter 4)

P² = a³

P = planet’s sidereal period, in years

a = planet’s semimajor axis, in AU

 A relationship between the acceleration of an object, the object’s mass, and the net outside force acting on the mass. (Chapter 4)

F = ma

The statement that whenever one body exerts a force on a second body, the second body exerts an equal and opposite force on the first body. (Chapter 4)

A formula deduced by Isaac Newton that expresses the strength of the force of gravity that two masses exert on each other. (Chapter 4)

[image]

F = gravitational force between two objects

m₁ = mass of first object

m₂ = mass of second object

r = distance between objects

G = universal constant of gravitation

[image]

P = sidereal period of orbit, in seconds

a = semimajor axis of orbit, in meters

m₁ = mass of first object, in kilograms

m₂ = mass of second object, in kilograms

G = universal constant of gravitation = 6.67 × 10⁻¹¹

A gravitational force whose strength and/or direction varies over a body and thus tends to deform the body. (Chapter 4, Chapter 12)

Fig 4.25

Frequency and wavelength of an

electromagnetic wave

[image]

ν = frequency of an electromagnetic wave (in Hz)

c = speed of light = 3 × 10⁸ m/s

λ = wavelength of the wave (in meters)

A relationship between the temperature of a blackbody and the wavelength at which it emits the greatest intensity of radiation. (Chapter 5)

[image]

λ_max = wavelength of maximum emission of the object (in meters)

T = temperature of the object (in kelvins)

The rate of energy flow, usually measured in joules per square meter per second. (Chapter 5)

A relationship between the temperature of a blackbody and the rate at which it radiates energy. (Chapter 5)

[image]

F = energy flux, in joules per square meter of surface per second

σ = a constant = 5.67 × 10⁻⁸ W m⁻² K⁻⁴

T = object’s temperature, in kelvins

The phenomenon whereby certain metals emit electrons when exposed to short-wavelength light. (Chapter 5)

Energy of a photon 

(in terms of wavelength)

[image]

E = energy of a photon

h = Planck’s constant

c = speed of light

λ = wavelength of light

E = hν

E = energy of a photon

Law 1 A hot opaque body, such as a perfect blackbody, or a hot, dense gas produces a continuous spectrum—a complete rainbow of colors without any spectral lines.

Law 2 A hot, transparent gas produces an emission line spectrum—a series of bright spectral lines against a dark background.

Law 3 A cool, transparent gas in front of a source of a continuous spectrum produces an absorption line spectrum—a series of dark spectral lines among the colors of the continuous spectrum. Furthermore, the dark lines in the absorption spectrum of a particular gas occur at exactly the same wavelengths as the bright lines in the emission spectrum of that same gas.

[image]

N = number of inner orbit

n = number of outer orbit

R = Rydberg constant = 1.097 × 10⁷ m⁻¹

λ = wavelength (in meters) of emitted or absorbed photon

[image]

Δλ = wavelength shift

λ₀ = wavelength if source is not moving

v = velocity of the source measured along the line of sight

c = speed of light = 3.0 × 10⁵ km/s

[image]

T_F = temperature in degrees Fahrenheit

T_C = temperature in degrees Celsius

A telescope in which the principal optical component is a concave mirror. (Chapter 6)

fig 6.9

The distortion of an image formed by a telescope due to differing focal lengths of the optical system. (Chapter 6)

angular resolution

Diffraction-limited angular resolution

The angular size of the smallest feature that can be distinguished with a telescope. (Chapter 6)

[image]

θ = diffraction-limited angular resolution of a telescope, in arcseconds

A technique for improving a telescopic image by altering the telescope’s optics to compensate for variations in air temperature or flexing of the telescope mount. (Chapter 6)

Such a system adjusts the mirror shape every few seconds to help keep the telescope in optimum focus and properly aimed at its target.

A technique for improving a telescopic image by altering the telescope’s optics in a way that compensates for distortion caused by the Earth’s atmosphere. (Chapter 6)

The goal of this technique is to compensate for atmospheric turbulence, so that the angular resolution can be smaller than the size of the seeing disk and can even approach the theoretical limit set by diffraction.

An optical device, consisting of thousands of closely spaced lines etched in glass or metal, that disperses light into a spectrum. (Chapter 6)

fig 6.20

 High-density worlds with solid surfaces, including Mercury, Venus, Earth, and Mars. (Chapter 7)

They all have hard,rocky surfaces with mountains, craters, valleys, and volcanoes

Low-density planets composed primarily of hydrogen and helium, including Jupiter, Saturn, Uranus, and Neptune. (Chapter 7)

the materials of which these planets are made are mostly gaseous or liquid

Kinetic Energy of gas atom 

or a molecule

Average speed of a gas atom

or a molecule

The speed needed by an object (such as a spaceship) to leave a second object (such as a planet or star) permanently and to escape into interplanetary space. (Chapter 7)

[image]

g: gravitational constant; m: mass; R: radius

 Any small body of rock and ice that orbits the Sun within the solar system, but beyond the orbit of Neptune. (Chapter 7, Chapter 14)

Ex. Pluto

Kuiper belt

The mechanism whereby electric currents within an astronomical body generate a magnetic field. (Chapter 7)

A planet or satellite with a global magnetic field has liquid material in its interior that conducts electricity and is in motion, generating the magnetic field.

fig 7.13

The process whereby certain atomic nuclei spontaneously transform into other nuclei. (Chapter 8)

 A technique for determining the age of a rock sample by measuring the radioactive elements and their decay products in the sample. (Chapter 8)

Experiment shows that each type of radioactive nucleus decays at its own characteristic rate

The idea that the Sun and the rest of the solar system formed from a cloud of interstellar material. (Chapter 8)

fig 8.6

The part of the solar nebula that eventually developed into the Sun. (Chapter 8)

The contraction of a gaseous body, such as a star or nebula, during which gravitational energy is transformed into thermal energy. (Chapter 8)

(proplyd) A disk of material encircling a protostar or a newborn star. (Chapter 8, Chapter 18)

fig 8.8

The hypothesis that each of the Jovian planets formed by accretion of gas onto a rocky core. (Chapter 8)

The hypothesis that gases in the solar nebula coalesced rapidly to form the Jovian planets. (Chapter 8)

fig 8.13

The point between a star and a planet, or between two stars, around which both objects orbit. (Chapter 8, Chapter 10, Chapter 17)

fig 8.16

 A technique for detecting extrasolar planets by looking for stars that “wobble” periodically. (Chapter 8)

fig 8.16

 A method for detecting extrasolar planets that come between us and their parent star, dimming the star’s light. (Chapter 8)

fig 8.18

transit: An event in which an astronomical body moves in front of another. See also meridian transit and solar transit. (Chapter 8)

A phenomenon in which a compact object such as a MACHO acts as a gravitational lens, focusing the light from a distant star. (Chapter 23)

fig 8.19

The transfer of energy by moving currents of fluid or gas containing that energy. (Chapter 9, Chapter 16)

 Hot air is less dense than cool air and so tends to rise

the rising air cools and becomes denser

The pattern of motion in a gas or liquid in which convection is taking place. (Chapter 9)

fig 9.5 (kitchen example)

The fraction of sunlight that a planet, asteroid, or satellite reflects.

(Chapter 9)

The trapping of infrared radiation near a planet’s surface by the planet’s atmosphere. (Chapter 9)

fig 9.6

 Earthquakes produce two kinds of waves that travel through the body of our planet.

One kind, called P waves, are longitudinal waves. They are analogous to those produced by pushing a spring in and out.

The other kind, S waves, are transverse waves analogous to the waves produced by shaking a rope up and down.

A crack in the ocean floor that exudes lava. (Chapter 9)

-where plates are separating

-convection causes plate movement

fig 9.16

 A location where colliding tectonic plates cause the Earth’s crust to be pulled down into the mantle. (Chapter 9)

cool crustal material from one of the plates sinks back down into the mantle 

The region around a planet occupied by its magnetic field. (Chapter 9)

solar wind is a flow of mostly protons and electrons that streams constantly outward from the Sun’s upper atmosphere, but our magnetic field has forces that this field can exert on charged particles are strong enough to deflect them away from us

fig 9.20

 Light radiated by atoms and ions in the Earth’s upper atmosphere, mostly in the polar regions. (Chapter 9)

fig 9.21

ozone

ozone layer

A type of oxygen whose molecules contain three oxygen atoms.

(Chapter 9)

A layer in the Earth’s upper atmosphere where the concentration of ozone is high enough to prevent much ultraviolet light from reaching the surface. (Chapter 9)

A region of the Earth’s atmosphere over Antarctica where the concentration of ozone is abnormally low. (Chapter 9)

fig 10.11

  Like Earth, the Moon has a crust, a mantle, and a core. The lunar crust has an average thickness of about 60 km on Earth-facing side but about 100 km on the far side. The crust and solid upper mantle form a lithosphere about 800 km thick. The plastic (nonrigid) asthenosphere extends all the way to the base of the mantle. The iron-rich core is roughly 700 km in diameter.

Tidal Forces

F_tidal = F_near − F_far

fig 10.17

Earth’s rapid rotation drags the tidal bulge of the oceans about 10° ahead of a direct alignment with the Moon. The bulge on the side nearest the Moon exerts more gravitational force than the other, more distant bulge. The net effect is a small forward force on the Moon that makes it spiral slowly away from Earth.

figure 11.1

Mercury moves around the Sun every 88 days in a rather eccentric orbit. As seen from Earth, the angle between Mercury and the Sun at greatest eastern or western elongation can be as large as 28° (when Mercury is near aphelion) or as small as 18° (near perihelion). By contrast, Venus follows a larger, nearly circular orbit with a 224.7-day period. The angle between Venus and the Sun at eastern or western elongation is 47°.

fig 11.3

The best times to observe Mars are at opposition, when Mars is on the side of Earth opposite the Sun. The red and blue dots connected by dashed lines show the positions of Mars and Earth at various oppositions. The months shown around the Sun refer to the time of year when Earth is at each position around its orbit.

A model of a planetary interior, particularly Venus, in which a thin crust remains stationary but wrinkles and flakes in response to interior convection currents. (Chapter 11)

fig 11.22

This illustration shows the difference between plate tectonics on Earth and the model of flake tectonics on Venus

Figure 11.28

Solar heating causes convection in the atmospheres of both Venus and Earth, with warm air rising at the equator and cold air descending at the poles. (a) Because Venus rotates very slowly, it has little effect on the circulation. (b)Earth’s rapid rotation distorts the atmospheric circulation into a more complex pattern (compareFigure 9-24).

Fast-moving subatomic particles that enter our solar system from interstellar space. (Chapter 11)

The rate at which electromagnetic radiation is emitted from a star or other object. (Chapter 5, Chapter 16, Chapter 17)

E = mc²

m = quantity of mass, in kg

c = speed of light = 3 × 10⁸ m/s

E = amount of energy into which the mass can be converted, in joules

Cosmic Connections Chapter 16

4 ¹H → ⁴He + neutrinos + gamma-ray photons

a small fraction (0.7%) of the mass of the hydrogen going into the nuclear reaction does not show up in the mass of the helium.

this mass is converted to energy  E = mc²

A balance between the weight of a layer in a star and the pressure that supports it. (Chapter 16)

1. The downward pressure of the layers of solar material above the slab.

2. The upward pressure of the hot gases beneath the slab.

3. The slab’s weight—that is, the downward gravitational pull it feels from the rest of the Sun.

The phenomenon whereby the Sun looks darker near its apparent edge, or limb, than near the center of its disk. (Chapter 16)

fig 16.8

Light from the Sun’s limb and light from the center of its disk both travel about the same straight-line distance through the photosphere to reach us. Because of the Sun’s curved shape, light from the limb comes from a greater height within the photosphere, where the temperature is lower and the gases glow less brightly. Hence, the limb appears darker and more orange

fig 16.9

High-resolution photographs of the Sun’s surface reveal a blotchy pattern called granulation. Granules are convection cells about 1000 km (600 mi) wide in the Sun’s photosphere. Inset: Rising hot gas produces bright granules. Cooler gas sinks downward along the boundaries between granules; this gas glows less brightly, giving the boundaries their dark appearance. This convective motion transports heat from the Sun’s interior outward to the solar atmosphere. 

fig 16.11

During a total solar eclipse, the Sun’s glowing chromosphere can be seen around the edge of the Moon. It appears pinkish because its hot gases emit light at only certain discrete wavelengths, principally the H_[image] emission of hydrogen at a red wavelength of 656.3 nm. The expanded area above shows spicules, jets of chromospheric gas that surge upward into the Sun’s outer atmosphere

The rotation of a nonrigid object in which parts adjacent to each other at a given time do not always stay close together. (Chapter 12, Chapter 16)

A splitting or broadening of spectral lines due to a magnetic field.

(Chapter 16)

a spectral line splits when the atoms are subjected to an intense magnetic field. 

The more intense the magnetic field, the wider the separation of the split lines.

The semiregular 22-year interval between successive appearances of sunspots at the same latitude and with the same magnetic polarity. (Chapter 16)

[image]

d = distance to a star, in parsecs

p = parallax angle of that star, in arcseconds

Tangential Velocity

Radial Velocity

Space Velocity

[image]

µ: proper motion

[image]

[image]

[image]

b = apparent brightness of a star’s light, in W/m²

L = star’s luminosity, in watts

d = distance to star, in meters