## Theoretical Classes

#### 1 - Cepheid Variable Star

A Cepheid variable is a type of star that beats radially, these vary in diameter and temperature. They produce changes in brightness with a stable and well-defined period and amplitude. The relationship between luminosity and pulsation period of these stars classifies them as indicators of cosmic reference points. This means that with these magnitudes distances and coordinates of bodies can be known in our galaxy and even outside. Henrietta Swan Leavitt discovered this type of star in 1908.

#### 2 - Parallax Formula

Another way to measure the distance of a body in astronomy is to observe the body to be measured from two different points, then the distance will be determined by the change in position that the body makes from the two points. This change is very precise, and the observation points are usually the extremes at which the Earth is located from the Sun. Finally, the written formula of the Parallax is as follows: d = 1 / p.

#### 3 - Exoplanet Transit Method

The transit method is a photometric method that involves detecting the presence of exoplanets in orbit around a star. In 1999, the method was used to confirm the existence of HD209458b. This discovery was made using a 10 cm diameter telescope installed in the parking lot of a building and paved the way for a new field of research on exoplanets. The first new detection was OGLE-TR-56b, discovered in 2003.

#### 4 - Spectroscopy Method

On the other hand, Doppler spectroscopy is a method for finding extrasolar planets and brown dwarfs from radial velocity measurements by observing Doppler changes in the spectrum of the planet's parent star. In February 2020, 880 extrasolar planets were discovered using this method.

#### 5 - Kepler's Third Law

Kepler's third law explains that the ratio of the square of the orbital period of an object to the cube of the major semi-axis of its orbit is the same for all objects orbiting the same primary. This captures the relationship between the distance of the planets to the Sun and their orbital periods. The Kepler's 3rd Law formula or equation is: P^2 = a^3

#### 6 - VTL's Laser

The VLT laser or Yepun laser is a terrestrial telescope that uses state-of-the-art optics, based on deformable mirrors that can be configured and adjusted to compensate for atmospheric distortions. In addition, the telescope sends a laser that creates a star in the sky, and the light that returns from that star produces very precise astronomical images.

#### 7 - Student's T

In probability and statistics, the Student's t distribution is a probability distribution that arises from the problem of estimating the mean of two groups of data and tells us if they are statistically relatively different.

#### 8 - ACIS Images

ACIS images are representations with which we can record the position, energy, and time of arrival of photons.

#### 9 - Visibility

On a clear day, not much radiation can be seen coming from bodies in space as it is dumped by the atmosphere and its distortions. With the eye of a human being one can only see between 400 and 800 nanometers, which is visible light.

#### 10 - Newton's Experiment

Newton's experiment is to make a hole in a wall, and from the ray of light that entered through this hole, it was divided by passing through a glass prism, forming the colors of the rainbow

#### 11 - Herschel's Experiment

The region or infrared light of the electromagnetic spectrum (I. R.) was discovered by William Herschel in 1800, using a prism and thermometers. In conducting this experiment, Herschel discovered that the temperature indicated by the thermometer in this area was higher than that of the environment.

#### 12 - Ritter's Experiment

Ritter did an experiment to discover grape (U. V.) rays, wetting papers with silver salts or silver chloride. To these, when the light divided in a prism like the one of the experiment of Newton arrived to him, were spots to the papers.

#### 13 - Franhoffer's Experiment

Fraunhofer, in 1814, conducted an experiment using the spectrum of the sun and instrumentation developed by himself. With these he reached a total of 570 obscure lines, now known as the 570 Fraunhofer lines. He studied these carefully, measuring their frequency accurately.

#### 14 - Kirchoff and Bunsen Experiment

Kirchhoff and Bunsen created the laws of spectra, burned chemicals, and observed their emission spectrum, through a filter.

#### 15 - Black Bodies and Energies

A black body is an ideal object similar to a black hole that absorbs all the light and all the radiant energy that falls on it, constituting an idealized physical system for the study of the emission of electromagnetic radiation. None of the incident radiation is reflected or passed through the black body. What differentiates a black body from dark matter is that the black body absorbs and emits light, while dark matter does not interact with electromagnetic radiation. In addition, this type of body must have temperatures above 100 ° K, and normally emit black body radiation, which forms a continuous spectrum. One third of the matter in the Universe is dark matter and the remaining two thirds is dark energy.

#### 16 - Exoplanet Density

The density of an exoplanet can be calculated by dividing its mass by its volume, as in any other object.

The radius of an exoplanet can be known by the method of transit or radial velocity.

#### 18 - Exoplanet Volume

The volume of an exoplanet can be known by calculating four by three multiplied by the number pi and the radius raised to three.

#### 19 - Linear Regression

Linear regression is a statistical method that models the relationship between a dependent variable (y), independent variables (x), and a random term (E).

#### 20 - Study Methods in the Atmosphere

Experiments in the atmosphere began with balloons, equipped with sensors, then began to use V2 rockets, and now we have space telescopes such as the Rosé or XMM-Newton.

#### 21 - MOOC

The Massive Open Online Course, are online courses aimed at a large number of participants via the Internet according to the principle of open and mass education. Every month more than 700 universities around the world offer hundreds of online courses, which are free.

#### 22 - CCD

A CCD is a very common device that circulates electricity when photons reach it. In this case, it can be used in astronomy to function when it detects light radiation from extrasolar bodies.

#### 23 - Cycles and Composition of the Stars

Depending on the size, stars like the Sun, are composed of some elements or others. They are mostly formed of hydrogen, these hydrogen atoms fuse, forming helium, later silicon, to explode at the end of their cycle and life.