It was in prehistoric times when humans first noted stars in the night sky, and it is where you can probably trace the roots of astronomy. In modern times Astronomy is defined as the science of the universe outside of our planet. It is also the branch of physical science dealing with heavenly bodies.
1. Cosmology: Cosmologists study the Universe as a whole, including its beginnings.2. Astrometry: Astrometrists measure great distances.3. Planetology: Planetologists study planets within our own Solar System as well as those orbiting distant stars.4. Radio Astronomy: Radio Astronomers use radio- telescopes to study the Universe.5. Mathematical Astronomy: Mathematical Astronomers who use numbers, calculations and statistics to explain the universe.
1. Optical Telescopes: Possess a much larger aperture than the human eye. This means that this can be used to collect much more of the light coming from distant object, which greatly improves resolution and clarity. The Refracting TelescopeThis was the earliest design and in usually formed using twolens. The distance between two lenses, which arecommonly placed near either end of a tube, can beadjusted to vary the resolution and magnification required.Any light passing through the forward lenses is refracted(bent) before being focused on the eyepiece lens.
2. A Radio Telescope: produces image with aid of a large concave mirror. The reflecting is also referred to as the Newtonian, after the English Astronomer Isaac Newton who first used this design to build a telescope around 1670.3. Spectroscope: a narrow slit that is illuminated by the light source under study; A collimator or tube and lens that produce a beam of parallel light rays; either glass or prism or a diffraction grating separate white light into its components and a telescope for viewing a spectrum.
4. Spectrograph: an instrument designed to photograph the spectrum instead of presenting it.5. Photometer: An instrument for measuring the intensity of light. One of the light sources will be the star whose brightness is to be determined, the other will be star of known magnitude or an artificial star of known magnitude.6. Interferometer: an instrument used to measure the angular diameter of the stars.7. Thermocouple: is an extremely sensitive instrument used to measure the heat radiated from a celestial body.
8. Comparators: comparator or a blink microscope, is used for the examination of photographic plates taken of the same region of the sky at different times.9. Chronograph: is an excellent means of recording astronomical observations accurately and permanently.10. Coronagraph: was invented by Bernard Lyot around 1930. this device enables the corona of the sun to be studied at anytime without waiting for the occurrence of a solar eclipse.
Thales and Anaximander were the first ancient Greekswho first recorded scientific theory on the nature of theuniverse. Ptolemy described a finite universe ruled by themathematicians and God in which the sun, planets, andother stars were attached to concentric spheres centeredon the Earth.
It was Nicolaus Copernicus who revived the Greek ideathat the Sun, and not the Earth, is the center of theuniverse.
1. The Big Bang Theory This theory explains that the universe sprang into existence as “singularity” around 13.7 billion years ago. This force can actually squished anything that goes on its way even light itself.
2. The Oscillating Theory The theory was credited to Richard Tolman who saw it as a possible outcome of the Big Bang theory. The theory emphasizes that the universe after expanding for years will soon grow cold and dark and die an ultimate heat death.
3. The Steady State Theory Austrian-British astronomer Hermann Bondi and the Austrian-American astronomer Thomas Gold formulated the theory in 1948. The British Astronomer Fred Hoyle soon published a different version of the theory based on his mathematical understanding of the problem. The big bang theory and the steady state theory were both based on Bondi’s “cosmological principle”.it states that the universe is on a large scale, that it looks the same at every point.
A galaxy is essential an immense collection ofstars which are held together by gravity. Theyrange on size to shape.
Elliptical Galaxies Galaxies of this class have smoothly varying brightness, with the degree of brightness steadily decreasing outward from the center. They appear elliptical in shape, with lines of equal brightness which is made up of concentric and similar ellipses. These galaxies are nearly the entire same color, they are somewhat redder than the Sun.
Spiral Galaxies These galaxies are conspicuous for their spiral-shaped arms, which emanate from or near the nucleus and gradually wind outward to the edge. The nucleus of a spiral galaxy is sharp-peaked area of smooth texture, which can be quite small or, in some cases can make up the bulk of the galaxy
Irregular Galaxies Consists of grainy, highly irregular assemblages of luminous areas. They have no noticeable symmetry nor obvious central nucleus, and they are generally bluer in colour than are the arms and disks of spiral galaxies An extremely small number of them, however, are red have a smooth, though nonsymmetrical, shape.
The Milky Way Galaxy Is a spiral system consisting of several billion stars, one of which is the Sun. It takes its name from the Milky Way, the irregular luminous band of stars and gas clouds that stretches across the sky.
Stars is a huge burning sphere of hot gas. The Sun is thenearest to Earth and the most comprehensively studied.The sun is just an ordinary star with ordinary size andbrightness. Since the sun itself is a star, it can be used asreference for understanding all other the stars.
A star has its own brightness but does not have thesame brightness. The difference of brightness in starscan be related to1. The amount of light produced by stars2. The size of each stars3. The distance to a particular star.
1. Apparent Magnitude – refers to how bright stars appear on Earth, taking relation the effect of the Earth’s atmosphere.2. Absolute Magnitude – are expression of luminosity, or the total amount of energy radiated into space each second from the surface of the stars.
Stars have varying colors and temperature, and theseare the bases of the different natures of stars.However, since the stars are too distant thus we canonly identify their relative brightness, the brighterthey appear the larger the image.The color is a function of a star to determine itsrelative temperature.
Type Color Temperature (K) Comment O Bluish 30,000 – Spectrum with Ionized 80,000 helium and Hydrogen but little else; short-lived and rare stars B Bluish 10,000 – Spectrum with neutral 30,000 helium, none ionized A Bluish 7,500 – Spectrum with no helium; 10,000 strongest hydrogen, some magnesium and calcium F White 6,000 – Spectrum with Ionized 7,500 calcium, magnesium, neutral atoms of iron G Yellow 5,000 – The spectral type of the 6,000 sun, with 67 elements K Orange – Red 3,500 – Spectrum packed with lines 5,000 from neutral metals M Reddish 2,000 – Band spectrum of molecules 3,500
The Life of A Star A star is born in a gigantic cloud of gas and dust in interstellar space, and then spends billion of years calmly shining while it fuses hydrogen nuclei in core. According to Bill W. Tillery, the life cycle of stars are just theoretical framework based on the outcome of studies regarding nuclear reactions, which include nuclear fusion and fission.
The first stage of theoretical model of stars. As gravity pulls the gas of a protostar together, the density, pressure and temperature increase from the surface down to the center. The mass of the star can start a simple nuclear fusion in the core. The initial fusion combines four atoms of hydrogen to form helium thus releasing huge amount of energy.
Lesser hydrogen fusion reaction occurs, thus less energy is released so the star begins to collapse. The collapse heats the core, which now composed primarily of helium and the surrounding shell still have hydrogen. The increase temperature causes hydrogen in the shell to undergo fusion, and the increased release of energy causes the outer layers of the stars to expand. With an increased surface area, and the amount of radiation emitted per unit area is less, the star acquires a property of red giant.
Less massive star may cool enough that the nuclei at the surface become neutral atoms rather than plasma. The outer layer of stars begin to pulsate in and out, and a violent expansion blows off the outer layers of the stars, leaving the hot core. The nebulae will continue to move away from the core of the star, leaving a carbon core and helium fusing shell begin to contract in a small, dense white dwarf star.
A more massive star will definitely have different theoretical ending. It will also contract just like less massive star. The heat from the star will used up all its energy, and will no longer maintain its internal temperature. The star loses outward pressure of expansion from the high temperature thus, the star will collapse, then rebounds like a compressed spring into catastrophic explosion called a supermova.
Main Sequence Stars Red Giants White Dwarfs Brown Dwarfs Variable Stars Binary Stars
- is the point in astar’s evolutionduring which itmaintains a stablenuclear reaction.Our Sun is a mainsequence star.
– is a large star that isreddish or orange incolor. It represents thelate phase ofdevelopment in a star’slife.The outer surface of thestar expands and cools,giving it a reddish color.
Is the remnant of an average-sized stars that has passed through the red giant stage of its life after the star has used up its remaining fuel. The star may expel some of its matter into space, creating a planetary nebula.
Also called as failed star. During the process of star formation, some protostars never reach the critical mass required to ignite the fires of nuclear fusion.
A star that changes in brightness. These fluctuations can range from second to years depending on the type of variable star. Stars usually change their brightness when they are young and when are old and dying.
Is a system of two stars that are gravitationally bound to each other. They orbit around a common point, called the center of mass. It is estimated that about half of all stars in our galaxy are part of a binary system.
1. NEBULAR HYPOTHESIS – for many yearsthe nebular hypothesis was a leading theory.According to it, the sun and its planetssupposedly condensed out of swirling eddies ofcold, dark, interstellar clouds of gas and dust.
2. FISSION THEORY – the “fission theory saysthat our sun burst one day, and all our planets camefrom it. Then the moons shot out from each planet,stopped, turned sideways and began circling theplanets they came out of.3. CAPTURE THEORY – the “capture theory”says that our planet and moons were wanderingaround in space and the planets were captured bythe gravity of our sun, and the moons were capturedby the planets.
4. ACCRETION THEORY – the “accretiontheory” says that our planets and moons werewandering around in space and the planets werecaptured by the gravity of our sun, and the moonswere captured by the planets.5. PLANETARY COLLISION THEORY – the“collision theory” of the origin our moon theorizesthat our world is said to have collided with a smallplanet. The resulting explosion threw off rocks whichformed our orbiting moon.
6. STELLAR COLLISION THEORY - the“collision theory” of the origin of the entire solarsystem suggests that our planets, moons, and sun allspun off from a collision between stars.7. GAS CLOUD THEORY – the “gas cloudtheory” of our planets and moons teaches that gasclouds were captured by our sun, which thenmysteriously formed themselves at a distance intoplanets and moons.
The Laws of Planetary MotionFirst Law:The orbits of the planets are ellipse with the Sun at onefocus of the ellipse.The sun is not at the center of the ellipse, but is insteadat one focus (generally there is nothing at the other focusof the ellipse). The planet then follows the ellipse in itsorbit, which means that the Earth-sun distance isconstantly changing as the planet goes around its orbit.For purpose of illustration we have shown the orbit asrather eccentric; remember that the actual orbits aremuch less eccentric than this.
The line joining the planet to the Sun and planetsweeps out equal areas in equal times, so the planetmoves faster when it is nearer the Sun. Thus, aplanet executes elliptical motion with constantlychanging angular speed as it moves about its orbit.The point of nearest approach of the planet to theSun is termed aphelion. Hence, by Kepler’s secondlaw, the planet moves fastest when it is nearperihelion and slowest when it is near aphelion.
Kepler’s Third Law implies that the period for aplanet to orbit the Sun increase rapidly with theradius of its orbit. Thus, we find that Mercury, theinnermost planet, (Pluto) requires 248 years to dothe same.
The Sun is at the center of our solar system. Sun’sstructure consists of from inner to outer elements –core (nuclear fusion), radiative zone, convectionzone, photosphere, chromosphere, and corona.Some of the Sun’s features are sunspots(photosphere), solar flares, coronal loops, andprominences (chromosphere and corona).
The Photosphere The deepest layer of the sun you can see is the photosphere. The word “photosphere” means “light sphere”. It is called the “surface” of the Sun because at the top of it, the photons are finally able to scape to space.
The photosphere is about 500 kilometers thick. By analysing light from the photosphere with a spectrograph, astronomers can tell that the Sun is consist of hydrogen and helium.
Sunspots are cooler regions on the photosphere.Since they are 1000-1500 K cooler than the rest ofthe photosphere, they do not emit as much light andappear darker . They can last a few days to a fewmonths.
During solar eclipse a thick layer can be seen at theedge of the dark Moon. This colorful layer is calledthe chromosphere (it means “color sphere”). Thechromosphere is only2000 to 3000 kilometersthick.
Solar prominence refers to a phenomenonastronomically which involves dense ionized clouds ofgas, otherwise known as plasma, which comes ourfrom the sun and are detained in place by itsmagnetic field. They are sculpted into vast loops ofarches by magnetic fields over sunspot group.The gas may splatter downinto the photosphere ascoronal rain or erupt intospace.
Solar flares are violent explosions in the chomosphere above sunspot groups; are caused by a release of magnetic energy. They send out bursts of high-energy particles and radiation that can interface with radio communications on Earth when they strike the ionosphere – the electrically charged layer of Earth’s atmosphere. Flares can endanger astronauts in space.
When the new Moon covers up the photosphere during a total solar eclipse, a pearly-white corona around the dark Moon is seen. This is the complex upper atmosphere of the Sun. It has a very high temperature, of one to two million Kelvin. Despite its high temperature, it has a low amount of heat because it is so fragile. The corona is known to be very hot because it has ions with many electrons removed from the atoms. At high temperatures, the atoms collide with each other with such energy to eject electrons. This process is called ionization.
The convective zone of the Sun is plasma-made part. Plasma is a “gas” that conductselectrical currents. The plasma in theconvective zone is mainly made up ofhydrogen (70℅ by mass), helium (27.7℅ bymass) plus small quantities of carbon,nitrogen and oxygen.
A non luminous celestial body bigger than an asteroid or comet, light up by luminosity from star, such as the sun, is called a planet. Planets are classified into two, these are terrestrial and gas planets.
Terrestrial is derived from Latin word terra, meaning ground or soil. Are described as the four planets in the solar system that are closest to the sun, Mercury, Venus, Earth, Mars. These four planets are composed primarily of rock and solid surfaces.
GAS PLANETS Jupiter, Saturn, Neptune, Uranus are referred to as Jovian or gas planets. It is much larger than terrestrial planets and composed mainly of gas and liquid.
The closest planet to the sun. It is a little and infertile planet. It has thousand of impact craters. It has no atmosphere that greatly affects its surface temperature. It revolves around the sun at an average distance of about 36 million miles (58 million kilometers), compared with about 93 million miles (150 million kilometers) for earth. Mercury moves around the sun faster than any other planet. The density of mercury is slightly a smaller amount than the Earth’s density. It has less mass than earth.
It is the Earth’s “twin” because the two planets are so alike in size. The diameter of Venus is about 7,520 miles (12,100 kilometers), approximately 400 miles (644 kilometers) smaller than that of the Earth. It takes about 225 Earth days, or about 71/2 months, to go around the sun once, compared of 365 days, or one year The mass of Venus is about 4/5 that of the Earth. Venus has smaller amount of density than the Earth. A fraction of Venus would weigh a little than an equal- sized part of the Earth.
Earth ranks fifth in size among the nine planets. Its diameter is 8,000 miles (13,000 kilometers). Earth takes 24 hours to turn completely around on its axis so that the sun is the same place in the sky. Earth takes 365 days 6 hours 9 minutes 9.54 seconds to round the sun.
Is the fourth planet from the sun. Named for the ancient Roman god of war Is one of Earth’s “next-doors neighbors” in space. 4.6 billion years old Mars is about 128,390,000 miles (206,620,000 kilometers) or as much as about 154,860,000 miles (249,230,000 kilometers) from the sun. It revolves around the sun once every 687 Earth days; this is what they call Martian year. Martian day is 24 hours 39 minutes 35 seconds long.
The chief of the gaseous giants and second of the greater planets, is the biggest planet in solar system, Jupiter. Over 11 times the diameter of the Earth and has a mass 2.5 times that all of the planets combined. It revolves around the sun in a slightly elliptical (oval- shaped) orbit. It takes 9 hours 56 minutes to spin around once on its axis, compared within 24 hours for Earth. The density of Jupiter is about ¼ that of Earth.
The second largest planet and the second gaseous planet is Saturn. It rotates faster than any other planet except Jupiter. Rolls around once only in 10 hours 39 minutes, compared to about 24 hours, or one day, for the Earth. It takes about 10,759 days, or 29 ½ Earth years, to go around the sun, compared with 365 days, or one year, for Earth. Has a lower density than any other planet.
Is the seventh planet from the sun. The farthest planet that can be seen without a telescope. It revolves around the sun in an elliptical (oval-shaped) orbit in 30,685, or 84 Earth years. Rotates on its axis and it takes 17 hours 14 minutes to spin around once in its axis. Uranus mass is only about 1/20 as big as that of the largest planet, Jupiter
One of the two planets that cannot be seen without telescope. 30 times as far from the sun as in Earth. It goes around the sun once in about every 165 Earth years. Spins around once in about 16 hours and 7 minutes.
Dwarf planet that orbits the sun. It lies on region known as the Kuiper belt. 39 times as far from the sun as Earth is. It come closer to the sun than Neptune’s orbit for about 20 years. Pluto entered Neptune’s orbit on Jan. 23,1979, and remained there until Feb. 11, 1999
The Moon is Earth natural satellite and the fifth largest satellite in the Solar System. The Moon makes a complete orbit around the Earth every 23.7 days, and the periodic variations in the geometry of the Earth-Moon-Sun system are responsible for the lunar phases that repeat every 29.5 days.
NEW MOON The Moon’sunilluminatedside is facingthe Earth.The Moon is notVisible (exceptduring solar eclipse).
The Moon appears to bepartly but less than one-halfilluminated by direct sunlight. The fraction of the Moon’sdisk that is illuminated Iincreasing.
One-half of the Moon appears to be illuminated by direct sunlight. The fraction of the Moon’s disk that is illuminated is increasing.
The Moon appears to be more than one-half but not fully illuminated by direct sunlight. The fraction of theMoon’s disk that isilluminated is increasing.
The Moon’s illuminated side is facing the Earth. The Moonappears to be completely by direct sunlight.
The Moon appears to be more than one-half butnot fully illuminated by direct sunlight.The fraction of the Moon’s disk that isilluminated is decreasing.
One-half of the Moon appears to be illuminated by direct sunlight. The fraction of he Moon’s disk that is illuminated is decreasing.
eclipse occur when the Earth, Sun and Moon are in a line.If the Moon is in-between the Earth and the Sun, it blocksthe view of the Sun from some parts of the Earth, and itsproduce a solar eclipse. If the Earth is between the Sunand Moon, the Earth block the light from the Sun before ifcan get to the Moon. Since moonlight is just the light theMoon reflects from the Sun, this will darken the Moon, andwe get lunar eclipse. An eclipse is consist of a darkershadow, or umbra and a lighter region, the penumbra orthe lighter shadow.
Whether it is the Moon between the Earth and Sun, orthe other way around, the phenomenon is basically thesame: the body in the middle casts a cone shadow, and ifthe outer body happens to move into this cone, we havean eclipse.It actually consists of a darker cone, or umbra, where nosunlight reaches, and a lighter region, the penumbra,where only some of the sunlight is blocked.
A solar eclipse occurs when the Moon is directly betweenthe Earth and Sun. this is the most spectacular kind,where the day changes into darkness and one can see thestars in plain day surrounding the dark disk of the Moon.
1. Total Solar Eclipse occur when the umbra of the Moon’s shadow touches a region on the surface of the Earth.2. Partial Solar Eclipse occur when the penumbra of the Moon’s shadow passes over a region on the Earth’s surface.3. Annular Solar Eclipse occur when a region on the Earth’s surface is in line with the umbra, but the distances are such that the tip of the umbra does not reach the Earth’s surface.
A lunar eclipse is a celestial that occurs when the Earth blocks all or part of the sun’s rays, preventing them from reaching the moon and thus creating a shadow across the moon. A lunar eclipse can happen between two and four times per year.
1. Penumbral Lunar Eclipse The Moon passes through Earth’s penumbral shadow. These events are of only academic interest because they are subtle and hard to observe.
2. Partial Lunar Eclipse A portion of the Moon passes through Earth’s umbral shadow. These events are easy to see, even with the unaided eye.
The entire Moon passes through Earth’s umbral shadow. These events are quite striking due to the Moon’s vibrant red color during the total phase (totality).
The word “tides” is a generic term used to define thealternating rise and fall in sea level with respect to theland, produce by a gravitational attraction of the moonand the sun.To a much smaller extent, tides also occur in largelakes, the atmosphere, and within the gravitationalforces of the moon and sun.
Tides are created because the Earth and the moon are attracted to each other, just like magnets are attracted to each other. The moon tries to pull at anything on the Earth to bring it closer. The Earth is able to hold onto everything except the water.
SPRING TIDES Spring tides are especially strong tides. They occur when the Earth, the Sun and the Moon are in a line. The gravitational forces of the Moon and the Sun both contribute to the tides. Spring tides occur during the full moon and the new moon
Neap tides are especially weak tides. They occur when the gravitational forces of the Moon and the Sun are perpendicular to one another. Neap tides occur during quarter moons.