The currently available distance scale in the World of Galaxies is unreliable, because it is built on approximate data on the distance to the stars closest to us, on hypothetical estimates of the parameters of these stars, on the meaningless Newtonian formula.
Determinations of the distances to several nearby stars are based on measurements of the annual displacement of a star in the celestial sphere, caused by the orbital motion of the Earth around the Sun, or parallax. By photographic methods, parallax is determined with an average accuracy of the order of 0.02 «- 0.05» (arc seconds). From the Earth, only for the nearest stars within 20-30 parsecs by this method, distances can be measured with no more than 50% accuracy.
For orientation within the Galaxy, an accuracy of at least 5-10% is required.
Transfer of estimates of distances to the nearest stars to galactic scales allows information on the luminosities of stars. The difference in luminosity and apparent brightness of a star, correlated with the magnitude of light absorption (A), makes it possible to calculate the distance to the star using the formula m — M = 5lgR — 5 + A.
The absolute magnitude for some types of stars is determined from the known parallaxes of similar stars available in the vicinity of the Sun, and to determine the luminosities of bright stars, open star clusters are used, the distances to the stars of which are almost the same.
One of the benchmarks for determining the distances between space objects are Cepheids, pulsating with a strict cyclicity and having a clear relationship between the pulsation period and the average absolute value, variable supergiant stars of spectral classes FG. The average luminosity of Cepheids corresponds to the formula: M (average) is approximately equal to -1.0m — 2.9m logP, where P is the period of brightness change in days.
More than 1000 Cepheids are known in the Galaxy, their brightness changes from 2 to 68 days , amplitude up to 1.5m.
Cepheids, like other young objects, allow you to recognize the structure of the spiral pattern of the Galaxy.
Using Cepheids, you can estimate photometric distances to other galaxies where they are found.
Other reference points for determining distances are also pulsating variable stars like RR Lyrae, which have approximately the same average luminosity, but change their brightness with periods from 0.4 to 1 day.
With the help of reference stars, we have repeatedly determined the distance to the center of the Galaxy R0. But there is no agreement about this distance. Estimates of R0 range from 6.5 for stars similar to RR Lyrae to 10 kpc for Cepheids. The Cepheids were used to construct the intergalactic scale.
The Cepheids were used to determine the distances to some spiral galaxies located at distances of about 10 megaparsecs, where the systemic «redshift» is already noticeable and, having calculated the Hubble constant (H), at 68 km in second per megaparsec, «determined the expansion time of the universe at 13.8 billion years.» The real value is about 72 km per second per megaparsec .
The HIPPARCOS project (High Precision PARallax Collecting Satellite), in which the parallaxes of 118,000 stars were determined in a sphere around the Sun with a radius of about 500 parsecs, made it clear about the question of which stars were used to determine the distances more correctly. The Cepheids also found themselves in this sphere, and the distances to the control Cepheids turned out to be much smaller, sometimes not less than a quarter less than it was previously thought. That is, the distance to the center of our Galaxy is no more than 6 kiloparsecs, that is, about 20 thousand light years. And the distances to the nearest galaxies with a systemic «redshift» are clearly 40% less than the accepted ones.
At the 221st meeting of the American Astronomical Society, Alis Deason, an astronomer at the University of California at Santa Cruz, announced that our Galaxy is smaller than previously thought. However, now the gas component that was not previously attributed to it began to be attributed to our Galaxy, and even the galaxies are satellites, that is, we can say that the Galaxy more than considered earlier, but its mass would not be affected by such a wow ..
Alice Deeson and her colleagues were guided by the most distant stars in the Milky halo Paths. The spread in the velocities of these stars allowed us to calculate the mass of the Milky Way at 500-1000 billion solar, which is half the estimated mass.
The period of revolution of the solar system around the center of the galaxy can be determined by geological methods. This was done by physicists at the University of California at Berkeley and Lawrence National Laboratory, about which they wrote an article in the journal.