DSST Astronomy

# Explanation binary in 1650 the italian astronomer

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Explanation: Binary. In 1650, the Italian astronomer John Baptist Riccioli observed that the star Mizar, in the middle of the handle of the Big Dipper, appeared through his telescope as two stars. Mizar was the first double star to be discovered. In the century and a half that followed, many other closely separated pairs of stars were discovered telescopically.

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_____________ binaries consist of two stars in nearly the same line of sight, of which one is far more distant than the other. Explanation: Optical. They are not true binary stars, but appear to be because of the line of sight. Optical binaries are relatively rare. In studies of binary stars, it is found that the more _____________ stars are also the more luminous. Explanation: Massive. This relation is known as the mass-luminosity relation. This relation results from the fundamental laws that govern the internal structures of stars. About 90% of all stars obey the mass-luminosity relation (as you will learn later, the main sequence stars). The most striking thing about the brightest-appearing stars is that they are bright not because they are nearby, but because they are actually of high intrinsic _________________. Luminosity. The rate of radiation of electro-magnetic energy into space by a star, or its luminosity, determines how bright it looks. Many stars that seem so bright to the naked eye are hundreds of light years away and are actually brighter than the sun. William Herschel, an English astronomer, sampled the distribution of stars about the sky by a procedure he called star ______________. Explanation: Gauging. He observed that in some directions he could count more stars through his telescope than in other directions. In 1785 he published the results of gauges of stars that he was able to observe in 683 selected regions scattered over the sky. In some areas, there was only a single star. In others, he counted over 600.
Visible to the human eye is a luminous band of light called the ___________ ________ that completely encircles the sky. Milky Way. Galileo solved the first mystery of the Milky Way when his observations revealed that it really consists of myriads of faint stars. It is the light from many distant stars that appear lined up in projection when we look from our position on Earth. Below is a 360-degree photographic panorama of the Milky Way Galaxy: The only parts of the sun that can be observed directly are its outer layers, collectively known as the sun's ________________. Explanation: Atmosphere. The solar atmosphere does not consist of distinct layers with sharp boundaries. Rather, there are three general regions, each with different properties and each gradually transitioning into the next. The three regions are the photosphere, the chromosphere, and the corona. The solar _______________ covers the range of depths from which the solar radiation escapes and is what we see when we look at the sun.

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