mount olympus mons-On Mars

This article is about the volcano on Mars. For other uses, see Olympus (disambiguation).

Olympus Mons
Wide view of the Olympus Mons aureole,escarpment and caldera
Coordinates	18.4°N 226°ECoordinates: 18.4°N 226°E
Peak	21 km above datum
Discoverer	Mariner 9
Eponym	Latin - Mount Olympus
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Olympus Mons (Latin for Mount Olympus) is a volcanic mountain on the planet Mars. It is a little under three times as tall as Mount Everest and is the tallest known volcano in the Solar System. Olympus Mons is the youngest of the large volcanoes on Mars, having formed during Mars' Amazonian Period. Olympus Mons had been known to astronomers since the late 19th century as the albedo feature Nix Olympica (Latin for "Snows of Olympus"). Its mountainous nature was suspected well before space probes confirmed its identity as a mountain.

The volcano is located in Mars' western hemisphere at approximately 18.4°N 226°E, just off the northwestern edge of the Tharsis bulge. The western portion of the volcano lies in theAmazonis quadrangle (MC-8) and the central and eastern portions in the adjoining Tharsis quadrangle (MC-9). Two impact craters on Olympus Mons have been assigned provisional names by the IAU. They are the 15.6 km (10 mi)-diameter Karzok crater (18°25′N 131°55′W) and the 10.4 km (6 mi)-diameter Pangboche crater (17°10′N 133°35′W).

The Great Barrier Reef "Australia"

The Great Barrier Reef is the world's largest coral reef system composed of over 2,900 individual reefs and 900 islands stretching for over 2,600 kilometres (1,600 mi) over an area of approximately 344,400 square kilometres (133,000 sq mi). The reef is located in the Coral Sea, off the coast of Queensland in north-east Australia.The Great Barrier Reef can be seen from outer space and is the world's biggest single structure made by living organisms. This reef structure is composed of and built by billions of tiny organisms, known as coral polyps. It supports a wide diversity of life and was selected as a World Heritage Site in 1981. CNN labeled it one of the seven natural wonders of the world. The Queensland National Trust named it a state icon of Queensland.A large part of the reef is protected by the Great Barrier Reef Marine Park, which helps to limit the impact of human use, such as fishing and tourism. Other environmental pressures on the reef and its ecosystem include runoff, climate change accompanied by mass coral bleaching, and cyclic population outbreaks of the crown-of-thorns starfish.The Great Barrier Reef has long been known to and used by the Aboriginal Australian and Torres Strait Islander peoples, and is an important part of local groups' cultures and spirituality. The reef is a very popular destination for tourists, especially in the Whitsunday Islands and Cairns regions. Tourism is an important economic activity for the region, generating $1 billion per year.

Alpha centauri -the nearest star to the sun

Alpha Centauri (α Centauri, α Cen; also known as Rigil Kentaurus, Rigil Kent, orToliman) is the brightest star in the southern constellation of Centaurus. To the unaided eye it appears as a single star, whose total visual magnitude of -0.27 would identify it as the thirdbrightest star in the night sky behind -0.72 magnitude Canopus. Alpha Centauri is a binary star system, designated Alpha Centauri AB (α Cen AB), whose individual components are named Alpha Centauri A (α Cen A) and Alpha Centauri B (α Cen B). Both stars lie 1.34parsecs or 4.37 light years away from our Sun.^[9]

A third star, known as Proxima Centauri, Proxima or Alpha Centauri C (α Cen C), is likely gravitationally associated with the closer binary, Alpha Centauri AB. Proxima is now placed at the slightly closer distance of 1.29 parsecs or 4.24 light years from the Sun, making it the closest star to the Sun, even though it is not visible to the naked-eye. True separation of Proxima from Alpha Centauri AB is about 0.06 parsecs, 0.2 light years or 13,000Astronomical Units (AU), equivalent to 400 times the size of Neptune's orbit.

Galaxy Andromeda

The Andromeda Galaxy (pronounced /ænˈdrɒmədə/) is a spiral galaxy approximately 2.5 million light-years away^[4] in the constellation Andromeda. It is also known as Messier31, M31, or NGC 224, and is often referred to as the Great Andromeda Nebula in older texts. Andromeda is the nearest spiral galaxy to the Milky Way, but not the closest galaxy overall. It is visible with the naked eye from Earth as a faint smudge on a moonless night, and can be seen even from urban areas with binoculars. It gets its name from the area of the sky in which it appears, the Andromeda constellation, which was named after the mythological princess Andromeda. Andromeda is the largest galaxy of the Local Group, which consists of the Andromeda Galaxy, the Milky Way Galaxy, the Triangulum Galaxy, and about 30 other smaller galaxies. Although the largest, Andromeda may not be the most massive, as recent findings suggest that the Milky Way contains more dark matter and may be the most massive in the grouping.^[10] The 2006 observations by the Spitzer Space Telescope revealed that M31 contains one trillion (10¹²) stars,^[7] more than the number of stars in our own galaxy, which is estimated to be c. 200-400 billion.^[11]

While the 2006 estimates put the mass of the Milky Way to be ~80% of the mass of Andromeda, which is estimated to be 7.1×10¹¹ solar masses,^[2] a 2009 study concluded that Andromeda and the Milky Way are about equal in mass.^[12] The Andromeda Galaxy and the Milky Way are expected to collide in perhaps 4.5 billion years.

At an apparent magnitude of 3.4, the Andromeda Galaxy is notable for being one of the brightest Messier objects,^[13] making it easily visible to the naked eye even when viewed from areas with moderate light pollution. Although it appears more than six times as wide as the full Moon when photographed through a larger telescope, only the brighter central region is visible to the naked eye or when viewed using a binoculars or a small telescope.