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SPACE ANIMALS

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Animal in space : Male Drosophila melanogaster (fruit flies )
 The first animals sent into space were fruit flies aboard a U.S.-launched V-2 rocket on February 20, 1947 from White Sands Missile Range, New Mexico.The purpose of the experiment was to explore the effects of radiation exposure at high altitudes. The rocket reached 68 miles (109 km) in 3 minutes and 10 seconds, past both the U.S. Air Force 50-mile and the international 100 km definitions of the boundary of space. The Blossom capsule was ejected and successfully deployed its parachute. The fruit flies were recovered alive. Other V2 missions carried biological samples, including moss.

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Laika (Russian ), meaning "Barker"; c. 1954 – November 3, 1957) 

 was a Soviet space dog who became one of the first animals in space, and the first animal to orbit the Earth.On November 3, 1957, the second-ever orbiting spacecraft carried the first animal into orbit, the dog Laika, launched aboard the Soviet Sputnik 2 spacecraft (nicknamed 'Muttnik' in the West). Laika died during the flight, as was intended because the technology to return from orbit had not yet been developed. At least 10 other dogs were launched into orbit

On July 22, 1951, the Soviet Union launched the R-1 IIIA-1 flight, carrying the dogs Tsygan , "Gypsy")and Dezik  into space, but not into orbit.These two dogs were the first living higher organisms successfully recovered from a spaceflight.Both space dogs survived the flight, although one would die on a subsequent flight. The U.S. launched mice aboard spacecraft later that year; however, they failed to reach the altitude for true spaceflight.



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Monkey in space ((Space monkey "Baker" rode a Jupiter IRBM into space in 1959 ):
Monkeys Able and Baker became the first monkeys to survive spaceflight after their 1959 flight. On May 28, 1959, aboard Jupiter IRBM AM-18, were a 7-pound (3.18 kg) American-born rhesus monkey, Able, and an 11 ounce (310 g) squirrel monkey from Peru, Baker. The monkeys rode in the nose cone of the missile to an altitude of 360 miles (579 km) and a distance of 1,700 miles (2,735 km) down the Atlantic Missile Range from Cape Canaveral, Florida. They withstood forces 38 times the normal pull of gravity and were weightless for about 9 minutes. A top speed of 10,000 mph (16,000 km/h) was reached during their 16-minute flight. The monkeys survived the flight in good condition. Able died four days after the flight from a reaction to anesthesia, while undergoing surgery to remove an infected medical electrode. Baker lived until November 29, 1984, at the US Space and Rocket Center in Huntsville, Alabama.

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What is Galaxy ?

 

A galaxy is, by definition, any large collection of stars that can be recognized as a distinct physical entity. In terms of the number of stars, a small 'dwarf irregular' galaxy like the Small Magellanic Cloud, has about one billion stars in it, but there are even smaller systems that are recognized as galaxies such as the Leo I and II dwarf galaxies with about 1 million stars in them, and the Draco System with a few hundred thousand stars in it. The largest star cluster, a globular cluster called Messier 15 has about 6 million stars, so we see that for small galaxies, there is a blurring together of what we mean by a galaxy and a large star cluster. In addition to their mass and numbers of stars, a galaxy is a collection of stars and gas which move through the universe independently of the Milky Way. Globular clusters are roundish swarms of stars that orbit the Milky Way, while the Leo and Draco Systems seem to be independent collections of stars. Galaxies are the places where gas turns into luminous stars, powered by nuclear reactions that also produce most of the chemical elements. But the gas and stars are only the tip of an iceberg: a galaxy consists mostly of dark matter, which we know only by the pull of its gravity. The ages, chemical composition and motions of the stars we see today, and the shapes that they make up, tell us about each galaxy’s past life. This book presents the astrophysics of galaxies since their beginnings in the early Universe. This Second Edition is extensively illustrated with the most recent observational data. It includes new sections on galaxy clusters, gamma ray bursts and supermassive black holes. Chapters on the large-scale structure and early galaxies have been thoroughly revised to take into account recent discoveries
such as dark energy.The authors begin with the basic properties of stars and explore the Milky Way before working out towards nearby galaxies and the distant Universe, where galaxies can be seen in their early stages. They then discuss the structures of galaxies and how galaxies have developed, and relate this to the evolution of the Universe. The book also examines ways of observing galaxies across the electromagnetic spectrum, and explores dark matter through its gravitational pull on matter and light.

 

 

Facts about Galaxies:-
Galaxy Facts
•Galaxy is derived from the Greek word meaning milk.
•Our solar system is in a galaxy called the Milky Way.
•Away from light pollution a spiral arm of the Milky Way can be seen in the night sky with the naked eye.
•The Milky Way is 100,000 light years across and is thought to have formed 10 to 12 billion years ago.
•Earth is located 26,000 light years from the center of the Milky Way.
•The Milky Way rotates once every 250 million years.
•There are around 200 billion stars in our galaxy.
•There are approximately 100 billion galaxies in the visible Universe.
•The nearest spiral galaxy to the Milky Way is Andromeda, it is 2.5 million light years from Earth.
•Andromeda is the furthest object that can be seen with the naked eye.
•At the center of most galaxies there is a supermassive black hole which can be millions of times more massive than our sun.

 

 

Age of Galaxy

 

How do you know galaxies are moving apart ?Light reaching us from distant receding galaxies has its absorption lines shifted toward the red end of the spectrum. This indicates that the galaxy is moving away from the Earth.The red shift indicates that the universe is expanding

 

Andromeda Galaxy


The Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years from Earth in the Andromeda constellation. Also known as Messier 31, M31, or NGC 224, it is often referred to as the Great Andromeda Nebula in older texts.

Distance to Earth: 2,538,000 light years
Apparent mass: ~1,230 billion M?
Age: 9 billion years
Constellation: Andromeda
Stars: 1 trillion
Coordinates: RA 0h 42m 44s | Dec 41° 16.152'

 

 

The Milky Way 

 

The Milky Way is the galaxy that contains our Solar System. Its name “milky” is derived from its appearance as a dim glowing band arching across the night sky in which the naked eye cannot distinguish individual stars.
Apparent mass: ~1,250 billion M?
Age: 13.2 billion years
Stars: 300 billion
Location : The solar system is located within the Milky Way Galaxy on a branch called the Orion Spur
Distance from Earth to the galactic center :  26,000 light years in the direction of Sagittarius
Diameter : 100,000 light years across


Name of our galaxy is known as the Milky Way galaxy. The Milky Way is a barred spiral galaxy and is part of the Local Group of galaxies. Ours is merely is one of billions of galaxies in the observable universe. Our sun is 25,000 light years from the center of the Milky Way. The oldest star in the galaxy is 13.2 billion years old.The stellar disk of the Milky Way Galaxy is approximately 100,000 light years in diameter and is about 1,000 light years thick. It is estimated to contain up to 400 billion stars. The exact figure depends on the number of very low-mass stars, which is difficult to determine. The stellar disc does not have a sharp edge, a radius beyond which there are no stars; however, the number of stars drops slowly with distance from the center. Beyond a radius of roughly 40,000 light years the number of  stars drops much faster the farther you get from the center. Beyond the stellar disk is a much thicker disk of gas that is estimated to be 12,000 light years thick. twice the previously accepted value.
 In 2007, the star HE 1523-0901 was estimated to be about 13.2 billion years old. The galaxy is thought to be just slightly older. The estimate of this star’s age was determined using the UV-Visual Echelle Spectrograph of the Very Large Telescope to measure the relative strengths of spectral lines caused by the presence of thorium and other elements created by the R-process. The line strengths yield abundances of different elemental isotopes from which an estimate of the age of the star can be derived using nucleocosmochronology

Types of Galaxies


The existence of other galaxies was established only in the 1920s. Before that, they were listed in catalogues of nebulae: objects that appeared fuzzy in a telescope and were therefore not stars. Better images revealed stars within some of these ‘celestial clouds’. Using the newly opened 100 telescope on MountWilson,Edwin Hubble was able to find variable stars in the Andromeda ‘nebula’ M31.He showed that their light followed the same pattern of changing brightness as Cepheid variable stars within our Galaxy. Assuming that all these stars were of the same type, with the same luminosities, he could find the relative distances from Equation 1.1. He concluded that the stars of Andromeda were at least 300 kpc from the Milky Way, so the nebula must be a galaxy in its own right. We now know that the Andromeda galaxy is about 800 kpc away.Hubble set out his scheme for classifying the galaxies in a 1936 book, The Realm of the Nebulae. With later additions and modifications, this system is still used today; Hubble recognized three main types of galaxy: ellipticals,lenticulars, and spirals, with a fourth class, the irregulars, for galaxies that would not fit into any of the other categories.Elliptical galaxies are usually smooth, round, and almost featureless, devoid of such photogenic structures as spiral arms and conspicuous dust lanes. Ellipticals are generally lacking in cool gas and consequently have few young blue stars. Though they all appear approximately elliptical on the sky, detailed study shows that large bright ellipticals have rather different structures from their smaller and fainter counterparts.Ellipticals predominate in rich clusters of galaxies, and the largest of them, the cD galaxies, are found in the densest parts of those clusters. Around an elliptical core, the enormous diffuse envelope of a cD galaxy may stretch for hundreds of kiloparsecs; these systems can be up to 100 times more luminous than the Milky Way. Normal or giant ellipticals have luminosities a few times that of the Milky Way, with characteristic sizes of tens of kiloparsecs. The stars of these bright ellipticals show little organized motion, such as rotation; their orbits about the galaxy center are oriented in random directions.
In less luminous elliptical galaxies, the stars have more rotation and less random motion. Often there are signs of a disk embedded within the elliptical body. 

The very faintest ellipticals, with less than ~1/10 of the Milky Way’s luminosity, split into two groups. The first comprises the rare compact ellipticals,like the nearby system M32. The other group consists of the faint diffuse dwarf elliptical (dE) galaxies, and their even less luminous cousins the dwarf spheroidal (dSph) galaxies, which are so diffuse as to be scarcely visible on sky photographs. The dE and dSph galaxies show almost no ordered rotation.Lenticular galaxies show a rotating disk in addition to the central elliptical bulge, but the disk lacks any spiral arms or extensive dust lanes. These galaxies are labelled S0 (pronounced ‘ess-zero’), and they form a transition class between llipticals and spirals. They resemble ellipticals in lacking extensive gas and dust,and in preferring regions of space that are fairly densely populated with galaxies; but they share with spirals the thin and fast-rotating stellar disk. The left panel of Spiral galaxies are named for their bright spiral arms, which are especially conspicuous in the blue light that was most easily recorded by early photographic plates. The arms are outlined by clumps of bright hot O and B stars, and the compressed dusty gas out of which these stars form. About half of all spiral and lenticular galaxies show a central linear bar: the barred systems SB0, SBa ,SBd form a sequence parallel to that of the unbarred galaxies. Along the sequence from Sa spirals to Sc and Sd, the central bulge becomes less important relative to the rapidly rotating disk, while the spiral arms become more open and the fraction of gas and young stars in the disk increases. Our Milky Way is probably an Sc galaxy, or perhaps an intermediate Sbc type; M31 is an Sb. On average, Sc and Sd galaxies are less luminous than the Sa and Sb systems, but some Sc galaxies are still brighter than a typical Sa spiral. At the end of the spiral sequence, in the Sd galaxies, the spiral arms become more ragged and less well ordered. The Sm and SBm classes are Magellanic spirals, named after their prototype, which is our Large Magellanic Cloud; . In these, the spiral is often reduced to a single stubby arm. As the galaxy luminosity decreases, so does the speed at which the disk rotates; dimmer galaxies are less massive. The Large Magellanic Cloud rotates at only 80 km s-1,
a third as fast as the Milky Way. Random stellar motions are also diminished in the smaller galaxies, but even so, ordered rotational motion forms a less important part of their total energy.We indicate this that by placing these galaxies to the left of the Sd systems.The terms ‘early type’ and ‘late type’ are often used to describe the position of galaxies along the sequence from elliptical galaxies through S0s to Sa, Sb, and Sc spirals. Some astronomers once believed that this progression might describe the life cycle of galaxies, with ellipticals turning into S0s and then spirals. Although this hypothesis has now been discarded, the terms live on. Confusingly, ‘earlytype’ galaxies are full of ‘late-type’ stars, and vice versa.Hubble placed all galaxies that did not fit into his other categories in the irregular class. Today, we use that name only for small blue galaxies which lack any organized spiral or other structure . The smallest of the irregular galaxies are called dwarf irregulars; they differ from the dwarf spheroidals by having gas and young blue stars. It is possible that dwarf spheroidal galaxies are just small dwarf irregulars which have lost or used up all of their gas. Locally, about 70% of moderately bright galaxies are spirals, 30% are elliptical or S0 galaxies, and 3% are irregulars.Other galaxies that Hubble would have called irregulars include the starburst galaxies. These systems have formed many stars in the recent past, and their disturbed appearance results in part from gas thrown out by supernova explosions.

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Spiral and S0 galaxies


The main feature of a spiral or S0 galaxy is its conspicuous extended stellar disk. Stars in the disk of a large spiral galaxy, like our MilkyWay, follow nearly circular orbits with very little random motion. Ordered rotation accounts for almost all the energy of motion, with random speeds contributing less than ~5%: the disk is dynamically ‘cold’. In smaller galaxies, random motions are proportionally larger,but most of the disk’s kinetic energy is still in rotation. Because the stars have little vertical motion perpendicular to the disk plane, the disk can be quite thin.Spiral galaxies are distinguished from S0 systems by the multi-armed spiral pattern in the disk. The disks of spiral galaxies still retain some gas, whereas S0 systems have lost their disk gas, or converted it into stars. Both S0 and spiral galaxies can show a central linear bar , the sequence of barred galaxies SB0, SBa, . . . , SBm runs parallel to the ‘unbarred’ sequence S0, Sa, . . .Apart from the bar and spiral arms, the stellar disks of large galaxies are usually fairly round; but many smaller systems are quite asymmetric.
Most giant disk galaxies – those with MB ~<-19 or LB ~>6 × 109L – are composite systems. Many of them probably have a metal-poor stellar halo
like that of the Milky Way . But the halo accounts for only a few percent of the galaxy’s light, and is spread over an enormous volume; so the surface brightness is low, making it difficult to study. The dense inner bulge is prominent in the Sa and S0 systems, less important in Sb and Sc galaxies, and absent in the Sd and Sm classes. Bulge stars have considerable random motions, and they are much more tightly packed than in the disk: near the Sun, the density of stars is n ~ 0.1 pc-3, whereas in bulges it is often 10 000 times higher. Bulges are generally rounder than the very flattened disks. They tend to be gas-poor, except for their innermost regions; in some respects, they are small elliptical galaxies placed inside a disk. The central hundred parsecs of the bulge may accumulate enough gas to fuel violent bursts of star formation. As in our Milky Way, the centers of many bulges host nuclear star clusters, the densest stellar systems. In some nuclei, we find massive compact central objects, which are probably black holes . Spirals are the most common of the giant galaxies, and produce most of the visible light in the local Universe. In the opening section we investigate the stellar content of the disks of spiral and S0 galaxies; Section 5.2 considers the gaseous component, and its relationship to the stars. In Section 5.3 we discuss the rotation curves of spiral galaxies, and what these reveal about the gravitational forces. In most spirals, the force required to maintain the outermost disk material in its orbit cannot be accounted for by the visible portion of the galaxy, its stars and gas. The difference is attributed to ‘dark’ material, which we detect only by its gravity. We then pause, in Section 5.4, to consider how much the scheme of Figure 1.11, classifying galaxies according to their appearance in visible light, can tell us about their other properties. Spiral arms and galactic bars form the topic of Section 5.5; these common and prominent features prove surprisingly difficult to understand. In Section 5.6 we discuss bulges and nuclei, and speculate on how they are related to the rest of the galaxy.

 

 

Elliptical Galaxy


Elliptical galaxies look like simple objects; but they are not. As their name implies, they appear round on the sky; the light is smoothly distributed, and they lack the bright clumps of young blue stars and patches of obscuring dust which are such obvious features of spiral galaxies. Ellipticals are almost devoid of cool gas, except at the very center; in contrast to S0 systems, they have no prominent disk. Their smooth appearance suggests that, like the molecules of air in a room, their stars have had time to reach a well-mixed equilibrium state. As with stars on the main sequence, we would expect the properties of elliptical galaxies to reflect the most probable state of a fairly simple system, with ‘no surprises’.Instead, detailed studies reveal a bewildering complexity. Elliptical galaxies cover a huge range of luminosity and of light concentration. Some ellipticals rotate fast, others hardly at all. Some appear to be oblate (grapefruit shaped), while othershave a triaxial shape with three unequal axes, like a squashed (American or rugby)
football. These properties are interlinked: luminous ellipticals are more likely to be triaxial, slowly rotating, and also strong X-ray sources, while the less luminoussystems are oblate and relatively rapidly rotating, and have dense stellar cusps at their centers.Itwas a mistake to think that elliptical galaxies might be close to an equilibrium state, because stellar systems have a very long memory. Most of a galaxy’s stars have made fewer than 100 orbits about the center; we saw in Section 3.2 that the relaxation time required to randomize their motions is far greater than the age of the Universe. If a galaxy was assembled in a triaxial shape, or with a dense central cusp, these characteristics would not yet have been erased. The variety
among elliptical galaxies suggests that they originated by a number of different pathways. Present-day elliptical galaxies are ‘fossils’ of the earlier Universe; our task is to reconstruct their birth and youthful star-forming lives from the old lowmass stars that remain. We begin this chapter with a section on photometry: how the images of elliptical galaxies appear in visible light, and what this tells us about the distribution of stars within them.  discusses stellar motions, and how the rotation of an elliptical galaxy is linked to its other properties. We consider what stellar orbits would be possible in a triaxial galaxy, with three unequal axes. In we look at the stellar populations of elliptical galaxies and at their gaseous content. Elliptical galaxies are quite rich in interstellar gas, but that gas is much hotter than the gas in disk systems; it can be studied only in X-rays. the dark matter in elliptical galaxies and the black holes at their centers. 

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