Movement

Doppler Effect

• the apparent change in wavelength of light that occurs when the object is moving toward or away from the Earth.

• Using the spectroscope, astronomers can determine whether a particular object is moving toward Earth or away from Earth

Ex) Ambulance Siren:Approach observer: High pitch ;

Move away from observer: low pitch

BLUE SHIFT RED SHIFT

Object approaching earth

Object moving away from earth

Light waves are compressed (pushed together)

Light waves are expanded

Wavelengths appear shorter (blue end of spectrum)

Wavelengths appear longer (red end of spectrum)

Larger Doppler shifts indicate higher speeds and smaller Doppler shifts indicate slower speeds.

Big Bang• A theory that explains the origin of the universe• Began as a singularity that started to expand

and continues to expand today• Evidence

– Red shifts of galaxies– Cosmic Background Radiation (CBR)

• Is there an end to the Big Bang?– Big Crunch– Ever-expanding universe

Hubble’s Law

• States that galaxies are moving away from each other at a speed proportional to their distance from each other– The farther away, the faster they move

• each raisin will see all other raisins moving away from it as the loaf expands

Earth’s Orbit and Seasons

Precession

• gradual shift in the orientation of Earth's axis of rotation• Cause: the gravitational forces of the Sun and the Moon,

and to a lesser extent other bodies– is similar to the precession of a spinning top

• Effects: – the positions of the south and north celestial poles

appear to move in circles against the space-fixed backdrop of stars

– the position of the Earth in its orbit around the Sun at the solstices, equinoxes, or other time defined relative to the seasons, slowly changes

http://earthobservatory.nasa.gov/Features/Milankovitch/Images/milankovitch_precess_high.mov

Precession

Nutation

• is a rocking, swaying, or nodding motion in the axis of rotation of a largely axially symmetric object

• happens because of tidal forces that cause the precession of the equinoxes to vary over time so that the speed of precession is not constant

• principal sources of tidal force are the Sun and Moon, which continuously change location relative to each other and thus cause nutation in Earth's axis

Barycenter

• refers to the point about which two celestial bodies revolve around– Not usual at the center of an object– Can be outside of the object (sun and Jupiter)

(a.) Two bodies of similar mass orbiting around a common center of mass, or barycenter.

(b.) Two bodies with a difference in mass orbiting around a common barycenter, like the Charon-Pluto system

(c.) Two bodies with a major difference in mass orbiting around a common barycenter (similar to the Earth-Moon system)

(d.) Two bodies with an extreme difference in mass orbiting around a common barycenter (similar to the Sun-Earth system)

Binary Star Systems

• There are four ways by which a binary star system can be detected: – visually, and are hence known as visual

binaries; – spectroscopically, hence are known as

spectroscopic binaries; – photometrically, these are known as eclipsing

binaries; and – Astrometrically (wobbly stars), hence are called

astrometric binaries