Answer:
Ptolemy: 48 constellations described in his great work, The Almagest, in the 2nd century AD.
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The 88 Constellations recognized by the International Astronomical Union.
Greetings!
The answer would be A. True.
Dissolved Oxygen is vital for most under water species. There has to be some flow of Oxygen throughout the water for the fish.
That is why most fish that are kept in tanks need filters. The purpose of the filter is to get that oxygen flow throughout the water, and of course keep it clean. Some fish, however will come to the top of the tank to breathe (Beta's for instance). But most fish will need that Oxygen throughout the water.
Hope this helps!
Explanation:
The Chandra X-ray observatory or CXC for its acronym in English, is an artificial satellite launched by NASA on July 23, 1999. It was named in honor of Indian physicist Subrahmanyan Chandrasekhar, one of the founders of astrophysics, who determined the boundary mass at which white dwarfs become a neutron star. In addition, Chandra means "moon" in Sanskrit.
The Chandra Observatory is the third of the Great Observatories of NASA. The first was the Hubble Space Telescope, the second was the Gamma Compton Ray Observatory, launched in 1991 and already disintegrated, and the last was the Spitzer Space Telescope. Before launching the Chandra Observatory was known as AXAF by the acronym in English of Advanced X-ray Astronomical Facility.
As the Earth's atmosphere absorbs most X-rays, conventional telescopes cannot detect them and a space telescope is necessary for their study.
In 1976 Riccardo Giacconi and Harvey Tananbaum proposed to NASA the idea of the Chandra Observatory, beginning preliminary work at the Marshall Space Flight Center. Meanwhile, in 1978, NASA launched the first X-ray space telescope, the Einstein (HEAO-2).
Despite this, work on the Chandra project continued during the 1980s and 1990s, but in 1992 the ship was redesigned to reduce costs. Four of the twenty mirrors that the observatory was going to dispose of were removed, and an elliptical orbit with which it would reach a third of the distance to the moon was calculated. This eliminated the possibility of being repaired by the space shuttle, but placed the observatory outside the influence of the earth's radiation belts most of its orbit.
DNA is the basic unit of inheritance
A gene is the basic physical and functional unit of heredity. Genes are made up of DNA. Some genes act as instructions to make molecules called proteins.
