Comparison of various stellar characteristics obtained earlier (namely: temperature, absolute brightness, speed of movement, and others) allowed Rössel to establish the division of stars into two large branches: absolutely very bright stars and faint stars, the so-called giants and dwarfs.
This difference in brightness is very large in red stars, but almost not observed in whites. This fact served to substantiate the theory of stellar evolution, which is that each star begins its existence in the form of a rarefied red giant, gradually passes as a result of energetic compression into the category of yellow, and then white stars. Further, when it cools, it again becomes a yellow, then a red star with incomparably higher density (dwarf) and, finally, ends up with complete cooling.
The theory of stellar evolution, which is associated with questions about the position of our Sun in the universe, about the maintenance of solar heat and many others, has not yet been completely established and continues to develop continuously. For their part, these ideas led to theoretical studies on the structure of the entire stellar mass, which have already yielded many extremely interesting conclusions.
All these works, the results of which are of great importance for our worldview, are based on modern data obtained by astrophysical research methods. Another characteristic example of results obtained by purely astrophysical methods is the modern understanding of the size and distance of spiral nebulae, consisting of a huge number of stars.
Direct determination of distances, adopted in astrometry, is possible only for the nearest stars. Already for more distant stars, it was necessary to turn, as we see, to the spectrographic method. For spiral nebulae located far beyond the limits of our stellar universe, this method is not applicable either. For these formations, it turned out to be possible to establish several indirect methods for determining the distances, all of which give results of the same order of magnitude. Apparently, it should be considered as certain that spiral nebulae are completely equivalent in size and mass to our Milky Way, which, as it was assumed before, also constitutes one of the spiral nebulae.
The collection of such spirals, each of which consists of billions of stars, forms a stellar system of the highest order.
Strange as it may seem, very little was known about our own solar system at the time. What is the physical state of the planets? What is the composition of their atmospheres? What is the origin of our system?
Until recently, all these questions have not yet been fully resolved.
Diffuse reflection laws
The planets shine with reflected light borrowed from the Sun. The laws of diffuse reflection were very poorly studied in photometry at that time. The proposed formulas, such as those of Lommel, Seeeliger and others, were either very crude in nature, or could be applied only in certain special cases. Further, the spectra of the planets mainly reproduce the spectrum of the Sun. For the upper planets (Jupiter, Saturn, Uranus, Neptune), they are characterized by the presence of many broad dark absorption bands, caused by some kind of compounds unknown to us.
Thus, both branches of astrophysics do not have much to offer here. Distant stars are much easier to explore than planets in our immediate vicinity. Apparently, the use of a thermoelement opens a new era in the study of the planetary system. This sensitive device, in conjunction with large mirror telescopes, makes it possible not only to determine the amount of heat coming from the planets, but through the use of appropriate filters, it allows to extract from the total planetary radiation that part of it that is caused by the planet’s own radiation as a heated body.
Knowing this last, it is possible to determine the temperature of the planet on the basis of the laws of radiation. During the opposition of Mars in 1924, it was finally stated that the temperature of this planet at the equator significantly exceeds 0 ° C. On the other hand, it was finally possible to separate the oxygen lines in the spectrum of Mars from the same lines of the Earth’s atmosphere overlapping them. All this, in connection with telescopic observations over this planet, which established the presence of clouds on it, the presence of a permanent snow cover at its poles and its periodic melting, makes it possible to assume the existence of organic life on Mars.