Star (Table) Diamond ring constellation
SUN Nebula Black hole Alpha Centauri Back to Astronomy
luminous ball of gas generating energy in its hot core through nuclear fusion
processes. The minimum mass required to form a star is about one-twentieth the
mass of the Sun. Below
this limit, the gravitational energy released when the mass condenses is
insufficient to raise the temperature to the point at which the fusion of
hydrogen to form helium can begin. The most massive stars known are about 100
solar masses. Mass is the prime factor determining the temperature and luminosity the star will have during its existence as a
main-sequence star, when hydrogen in the core is its
Stars are predominantly hydrogen, with helium as the other major constituent. In the Sun, which is in many ways a typical star, 94 per cent of atoms are hydrogen, 5.9 per cent helium and less than 0.1 per cent other elements. By weight, 73 per cent is hydrogen, 25 per cent helium, 0.8 per cent carbon and 0.3 per cent oxygen, the remaining 0.9 per cent being all the other elements
Originally, constellations were regarded simply as
star patterns, but they gradually acquired usefulness as a way of specifying
stars and their positions. Records show that, from antiquity,
civilizations have given names to conspicuous patterns of bright stars. Each
culture had its own way of dividing the sky into pictorial elements. . there was
international agreement among astronomers to define the boundaries of
constellations along lines of right ascension and declination.
There are 88 designated areas in the sky or the pattern of stars for 88
Some of the Important Constellations
The largest of the 88 constellations is Hydra, the Water Snake. The area of sky designated as Hydra is 1302.84 square degrees, which is 3.16% of the whole sky. The next largest constellation is Virgo, at 1294.43 square degrees.
Sun our nearest star
This magnetogram taken from reveals bands of solar activity either side of the Sun's equator. Red and blue areas are regions of strong magnetic field of opposite polarity. Large sunspots often occur in pairs, one of each polarity (north and south).
All stars are hot, gaseous bodies like the Sun . Of the 50 nearest stars ,10 per cent are brighter, larger, and more massive than the Sun. The nearest star, Alpha Centauri, is about 260,000 times farther from the Earth than is the Sun. It is 4.3 light years away. The entire Milky Way Galaxy is about 100,000 light years across, but only some 1,000 light years thick.The source of the vast quantities of energy radiated by the Sun was long a mystery. The Sun emits energy at the rate of 3.8 × 1026 watts. Life had existed on Earth for billions of years, indicating that solar energy must have been expended at about its present rate for that long. The temperature at the heart of the Sun, about 15 million degrees C. Energy generation process in the sun is the conversion of hydrogen into helium. Energy generation process of the sun is the conversion of hydrogen into helium. over 4 million tonnes of mass are converted into pure energy at the heart of the Sun each second, in line with the equation, devised by Albert Einstein, E = mc2. This says that mass and energy are interchangeable, and that the energy E locked up in a mass m is equal to the mass multiplied by the square of c, the speed of light The source of the vast quantities of energy radiated by the Sun was long a mystery. The Sun emits energy at the rate of 3.8 × 1026 watts. Life had existed on Earth for billions of years, indicating that solar energy must have been expended at about its present rate for that long. The temperature at the heart of the Sun, about 15 million degrees C. Energy generation process in the sun is the conversion of hydrogen into helium. Energy generation process of the sun is the conversion of hydrogen into helium. over 4 million tonnes of mass are converted into pure energy at the heart of the Sun each second, in line with the equation, devised by Albert Einstein, E = mc2. This says that mass and energy are interchangeable, and that the energy E locked up in a mass m is equal to the mass multiplied by the square of c, the speed of ligh
|A solar eclipse in which a ring of the Sun's photosphere remains visible when the Sun, Moon and Earth are aligned. Since the orbits of the Earth around the Sun and of the Moon around the Earth are elliptical, the angular diameters of the Sun and Moon vary slightly as their distances from the Earth change. A solar eclipse that would otherwise have been total is seen as annular if the Moon's angular diameter at the time is less than the Sun's|
The so-called "diamond ring" effect captured at the end of totality during the solar eclipse of 11 July 1991.Black hole
A region of space where the gravitational
force is so strong that not even light can escape from it. Black holes are
formed when matter collapses in on itself catastrophically so that more than a
critical quantity of mass is concentrated into a particularly small region. t is
believed that stellar black holes may form when massive stars explode. To create
a black hole, several solar masses of material would have to be packed into a
diameter of just a few kilometres Black holes are believed to exist at the
centres of many galaxies. Black holes can never be observed directly: their
existence can only be inferred from their gravitational effects and the
radiation emitted by material falling into them.
The brightest star in the constellation Centaurus and the nearest bright star to the Sun, at a distance of 4.34 light years. It is a visual binary star with an orbital period of 80 years See table
Nebula A cloud of interstellar gas and dust An emission nebula glows
in presence of ultraviolet radiation; a reflection nebula shines by reflecting
starlight. An absorption nebula is dark and is usually evident only in
silhouette against the background of a luminous nebula or starfield.
Other objects consisting of luminous gas are also known as nebulae
right ascension (RA)
One of the coordinates used to define position on the celestial sphere in the equatorial coordinate system. It is the equivalent of longitude on the Earth but is measured in hours, minutes and seconds of time eastwards from the zero point, which is taken as the intersection of the celestial equator and the ecliptic, known as the First Point of Aries. One hour of right ascension is equivalent to 15 degrees of arc; it is the angle through which the celestial sphere appears to turn in one hour of sidereal time, as the Earth rotates.
declination (1) (Dec.)
Declination is the equivalent of latitude on the Earth. It is the angular distance, measured in degrees, north or south of the celestial equator. Northerly declinations are positive and southerly ones negative
Table some important Constellation
|Latin name||Area (square degrees)||Rank in size order|
|Stars of apparent visual magnitude 2.0 and brighter.|