Zvezdnaya noch

12/10/2023

A beautiful creation by AI🌺🌼
Amazing Birds of the World, Bird's Galaxy(��)

12/10/2023

variable stars
Main article: Variable star

Light curve of δ Cephei
Animation of an eclipsing binary star and its light curve
Variables are those stars whose brightness changes enough for it to be detected with the current state of the art. If the variability is caused by physical changes in the star, then it is called physical, and if the illumination created by the star changes only due to its rotation or coverage by other objects, it is called geometric. Physical and geometric variability can be combined. The star magnitude in this case can change both periodically and in the wrong way[58][59][60]. At the same time, variability is not a constant characteristic of a star, but arises and disappears at different stages of its evolution (see below[⇨]) and can take on a different character for the same star.

12/10/2023

Additional designations
If the spectrum of a star has some features that distinguish it from other spectra, an additional letter is added to the spectral class. For example, the letter e means that there are emission lines in the spectrum; m means that metal lines are strong in the spectrum. The letters n and s mean that the absorption lines are wide or narrow, respectively. The designation neb is used if the type of the spectrum indicates the presence of a nebula around the star, p - for peculiar spectra .

12/08/2023

The most low-mass stars are fully convective.

Atmospheres of stars

The solar corona during the 1999 eclipse
The stellar atmosphere is the region in which directly observable radiation is formed.

12/08/2023

In different stars, the radiative transfer zone and the convective zone are located differently. For example, in main-sequence stars larger than 1.5 M⊙, the core is surrounded by a convective zone, while the radiative transport zone is outside. In the mass range from 1.15 to 1.5 M⊙, stars have two convective zones in the center and on the boundary, which are separated by a radiative transport zone. In stars with a lower mass, there is a convective zone outside, and a radiative transfer zone inside - the Sun also belongs to such stars, the boundary of these regions is located at a distance of 0.7 R⊙ from its center .

12/06/2023

In order for the movement of stars to be noticed without precise measurements, it is necessary to compare the appearance of the starry sky with an interval of thousands of years. In this regard, since ancient times, stars have been united into constellations, and at the beginning of the 20th century, the International Astronomical Union approved the division of the sky into 88 constellations and the boundaries of each of them.

12/06/2023

Spectrum of a star of spectral type A0V. The dotted lines indicate the spectra of absolutely black bodies with temperatures of 9500 and 15000 K
Almost all stars are observed from the Earth as point objects even when using telescopes with high magnification - the exception is only a small part of the stars, the angular dimensions of which exceed the resolution of the largest instruments, as well as the Sun [4]. In total, there are about 6,000 stars in the sky that can be seen with the naked eye in good conditions, and up to 3,000 stars located above the horizon can be observed simultaneously. The mutual position of the stars (except the Sun), unlike the Moon and other objects of the solar system, changes very slowly: the largest proper motion of a star, which is recorded in Barnard's star, is about 10 "per year, and for most stars it does not exceed 0, 05′′ per year.

12/04/2023

Today is . Did you know more than 41,000 species are thought to be at risk of extinction? But, there's hope in conservation success stories. While only about 1,000 mountain exist in the wild, this number represents a 60% increase over the past 30 years! 💚🌍

📷: Martin Harvey

12/04/2023

12/04/2023

Stars often form gravitationally bound systems: binary or multiple systems, star clusters and galaxies. Over time, stars change their characteristics, as thermonuclear fusion takes place in their depths, as a result of which the chemical composition and mass change - this phenomenon is called the evolution of stars, and depending on the initial mass of the star, it can take place in completely different ways.