Not only can distances, mass, volume, density, temperature be measured. In the Universe, the brightness of the stars, the declination, the wavelength and many other magnitudes are also measured.
Let’s see what can be measured in the Universe and how it is measured.
Measurements of the Universe, basic concepts
Mass: is the amount of matter in an object.
Volume: is the space occupied by an object.
Density: calculated by dividing the mass of an object by its volume.
Temperature: the amount of heat from an object. The lowest possible temperature in the Universe is 273 ºC below zero (0º Kelvin), which is not having any type of energy.
Units for measuring distances
Measuring the Universe is complicated. The usual units often do not work. Distances, time, and forces are enormous, and obviously cannot be measured directly.
To measure the distance to nearby stars, the parallax technique is used . It involves measuring the angle formed by distant objects, the star being observed, and the Earth, at the two opposite points of its orbit around the Sun, for example, in January and July.
The diameter of the Earth’s orbit is 300 million kilometers. Using trigonometry, the distance to the star can be calculated. This technique, however, does not work for distant objects, because the angle is too small and the margin of error too great.
| Unit | Concept | equivalence |
| Astronomical unit (ua) | Average distance between the Earth and the Sun. It is not used outside the Solar System. |
149,600,000 km |
| Light-year | Distance that light travels in a year. If a star is 10 light years away, we see it as it was 10 years ago. It is the most practical. |
9.46 billion km 63,235.3 UA |
| Parsec (parallax-second) |
Distance of a body that has a parallax of 2 arc segments . The most “scientific”. |
30.86 trillion km 3.26 light years 206,265 ua |
To measure astronomical distances
The brightness of the stars
Brightness (stellar magnitude) is a system of measurement in which each magnitude is 2.512 times brighter than the next. A magnitude 1 star is 100 times brighter than a magnitude 6. The brightest ones have negative magnitudes.
There are only 20 stars of magnitude equal to or less than 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 equator.
Each object describes an apparent “circle of decline.” The distance, in hours, from this to the reference circle (which passes through the poles and the position of the Earth at the beginning of spring) is the ascension of the object.
By combining ascension, declination, and distance, an object’s position relative to Earth is determined.
Wavelength
Wavelength is the distance between two crests of light, electromagnetic or similar waves. The shorter the length, the higher the frequency. His study provides a lot of data about space.
