## Basics

Mass is the amount of matter in an object

volume. It is the space occupied by an object

density. It is calculated by dividing the mass of an object by its volume

temperature. The amount of heat an object. The coldest temperature in the universe is 273 ° C below zero (0 ° Kelvin), which is not having any energy.

## Units for measuring distances

Measuring the Universe is complicated. They often do not serve the usual units. The distances, time and forces are huge and, as is evident, can not be measured directly.

To measure the distance to nearby stars parallax technique is used. This is the angle measuring distant objects, the observed star and the Earth, at two opposite points of its orbit around the sun.

The diameter of Earth's orbit is 300 million miles. Using trigonometry we can calculate the distance to the star. This technique, however, not suitable for distant objects, perque the angle is too small and the margin of error is very high.

## The brightness of the stars

The brightness (stellar magnitude) is a system of measurement in which each quantity is 2,512 times brighter than the next. A magnitude 1 star is 100 times brighter than a magnitude 6. The brightest have negative magnitudes.

There are only 20 stars of magnitude less than or equal to 1. The faintest star that has been observed has a magnitude of 23.

## Decline

Declination is the measure, in degrees, of the angle of an object in the sky above or below the celestial Ecuador.

Each object describes an apparent "circle of decline." The distance, in hours, from there to the reference circle (passing through the poles and the position of the Earth at the beginning of spring) is the ascension of the object.

Combining the ascension, declination and distance determines position Earth on an object.

## Wavelength

Wavelength is the distance between crests of light, electromagnetic wave or the like. A shorter, more frequently. Their study provides extensive data on space.

Translated from the website: http://www.astromia.com/