astronomy hw #2

Constellation

A specific region of sky as defined by the International Astronomical Union (IAU) in 1928. The IAU divided the sky into 88 official constellations - every star is a member of one of these groups. Many "historical" constellations (such as the Big Dipper) are actually not a modern constellation, but rather a group of stars known as an Asterism found within a constellation.

Explain why a superior planet cannot have an inferior conjunction:

An inferior conjunction occurs when a planet is position between the Earth and the Sun. A superior planet is defined as a planet whose orbit is outside of the Earth's orbit. Since a superior planet is further from the Sun than the Earth, it cannot ever be in a position where it is between the Sun and the Earth.

why is it cold in the winter and hot in the summer

First, the Earth's axial tilt leads to us having shorter days and longer nights during the winter, thus if there is less sunlight, then we receive less energy and have colder weather. Second, is the change in the angle that the sun's rays make with respect to the surface of the Earth. During the winter in the northern hemisphere, the north pole is pointed away from the sun. As a result of this, the sun's rays strike the northern hemisphere less directly. This means less sun-light hits each square mile of Earth's surface per second, and thus less energy is striking the Earth's surface and contributing to our colder winter weather.

Asterism

Less-formal groupings of stars and are often the forms in the sky we think of when we say "constellation". For example, the Big Dipper is located in the constellation of Ursa Major. Often historical constellations that are not included in the modern catalogue of 88 constellations, are listed as asterisms within a constellation.

From what locations on the Earth is the North Celestial Pole not visible? From what locations is the South celestial pole not visible? From what locations is the celestial equator not visible?

The North Celestial Pole is not visible from any point on Earth south of the equator. Similarly, the South Celestial Pole is not visible from points north of the equator. The Celestial Equator is visible from all points on Earth, except that at the poles, in which case it would be right on the horizon.

Ecliptic

The apparent path that the sun traces out against the background stars due to the Earth's orbit around the Sun. More precisely, the ecliptic is the line formed by the intersection with the plane of the Earth's orbit and the celestial sphere.

Equinox

These are the two days of the year when the sun rises due east and sets due west. The length of day and night are both equal at 12 hours on this day.

Superior Conjunction

This is the occurrence when a planet is located directly behind the sun (from the Earth's point of view) on an extension of the line connecting the Earth and the Sun.

Inferior Conjunction

This is the occurrence when an inferior planet is located on the line connecting the Earth and the Sun, and is located between the Earth and the Sun.

Celestial Equator

a projection of the Earth's equator onto the celestial equator.

Solstices

the days when the sun is farthest north and south of the celestial equator. What this means is that the path that the sun traces in the sky during the day (from rising to setting) is furthest from due east and west.

Celestial Poles

the points on the celestial sphere where the Earth's axis would touch if it were extended out from the North and South Poles.