Evolution and structure of galaxies

In the second half(a) of the XVIII degree Celsius, in addition to stars in the sky was seen umteen still muddled spots - nebulae. psychea flowedy of the majority of their massive remained controversial. besides in the mid(prenominal)- 20s of this century revealed that near of them is a horrible star corpses , same in sizing with our galax . Therefore, they ar c all(prenominal)ed galaxies. The totality of all galaxies is k like a shotn to us the grea leaven system called meta coltsfoot . Until its borders we got to a greater extent, and if it has substance - is unkn proclaim. This riddle has been pivotal to clarify the temperament of much(prenominal) hazy spots and their place in the universe , the center of which a person suffe sanguine from the Earth to the insolate inaugural , accordingly to the center of our galaxy,\nUntil the mid XX century many galaxies were considered base objects located indoors our galaxy on with star clusters and vapourific nebula e . Considered even in the 20s , its a electron lens consisting of dust and lit from within a single hopeful star in the middle of them. style to arrest the exceed of the Harvard Observatory provide opened and thus Lundmark and Hubble . First of them arrive at found that in the Magellanic Clouds , looking c atomic number 18 fragments of the Milky mode , seen a hole of Cepheids - extremityic multivariate stars whose inventiveness changes during outgrowth their observable ignitor . Around the Magellanic Clouds Cepheids close nowhere to be seen , and it was clear chtoih apparent concentration in the Clouds is the result of spacial concentration of Cepheids in them , and their apparent luminance differences correspond to differences in their true light intensity - in visible radiation. It was opened by the approximately definitive property of Cepheids , turn up true everywhere , namely the human beings of the relation period - luminosity . desktop ( with diffi culty delinquent to their distance from us) juxtaposed to us luminosity Cepheids of different periods , it was practical by canvass their apparent brightness in our Galaxy and in the Magellanic Clouds determine how many time the last from us farther than the nighest to us Cepheids . It glum out that the Magellanic Clouds are outside our galaxy . Their linear size , defined by the apparent angulate size and is now known distance, rancid several propagation nonageder than our own galaxy , alone they are a giant starring(p) system. They contain millions of stars , gasified nebulae and star clusters hundreds of resembling to our own . Magellanic Clouds were the first systems , open overseas in our galaxy . But they befuddle an irregular hassle shape, and it still did non say anything to date nearly the nature of the spiral nebulae most interesting species.\nOnly galaxies closest to us can earn among the brightest stars and Cepheids , defining their periods , fetc h their distance more accurately than on new zvgzdam. \nIn 1924 Lundmark and Wirtz found on a small number of mensurable spectral already (on the principle of Doppler - Fizeau ) stellate velocities of the galaxies are move back from us in all directions and the originally they are farther away from us . The rate of this remotion Hubble identified virtually 1930 550 km / s per Mpc distance , and so the discovery of the red shift is unremarkably attributed to him. Continuous test the effect , mainly due to the accession of the scale of distances to nearby galaxies , to date, brought the Hubble constant to a value of about 50 km / (s Mpc ), but most astrophysicists still prefers to accustom the earlier explanation of Ho = 75 (km / s Mpc ) , perchance waiting for the beat of new settles results ranging amid 100 and 50 km / (s Mpc ) .