My Science School

Our solar system consists of the sun, planets, moons, dwarf planets, asteroids, comets, meteors, and others. Of all the planets in our solar system, the six nearest the Sun can be seen with the naked eye. So these planets – Mercury, Venus, Earth, Mars, Jupiter, and Saturn- have been observed since ancient times. The first planet to be discovered using a telescope was Uranus, in 1781. Neptune, the eighth planet was discovered only in 1846. Pluto was discovered in 1930, but it is now not classified as a planet, and so Neptune is considered to be the last planet to be discovered in our solar system

Sedna

Astronomers have detected what could be a new planet in our solar system. It was first seen by astronomers at California’s Palomar Observatory, and has been given the name ‘Sedna’. Sedna, or 2003 VB 12, as it was originally designated, is the most distant object yet found orbiting our Sun. however, there is some debate as to whether it is a true planet, or a planetoid like Pluto.

Asteroids, comets, and meteorites are the debris left over after a meteoroid has burned up in the outer atmosphere. Whenever any of these collide with the Earth, the result is devastating. The last such impact occurred in the year 1930. On February 17th, 1930, a meteorite hit Paragould, in Northeast Arkansas. At that time, it was the largest stony meteorite in the world to be seen falling and recovered.

 Another famous asteroid impact happened on Earth on 13th August of the same year, when an asteroid exploded in the sky above the River Curuca in Brazil. At about eight o’ clock, the sun became blood-res, and darkness fell over the region. Three mighty explosions were heard in rapid succession. Immediately after the explosions, the whole forest became a blazing inferno, which lasted for several months.

Asteroid Hit

 There are a number of stories of people being injured, and even killed, by meteorites. On 30th November 1954, Mrs. Hewlett Hodges of the USA was hit by an asteroid. A four kilogramme asteroid crashed through the roof of her home, and she was struck as she slept in the living room. Fortunately, her injury was not serious.

Yes, though only for a few minutes, and only if the eclipse is occurring just as the Moon is rising and the Sun is setting, or the Moon is setting and the Sun rising. A total eclipse occurs when the Earth is between the Moon and Sun, which are directly opposite to each other in the sky.

 Seeing both the Sun and eclipsed Moon at the same time would appear to be a geometrical impossibility, but because the atmosphere has a lensing effect, it raises the images of both the rising Moon and setting Sun above the horizon for a few minutes.

For the same reason, day and night are not exactly equal at the time of the fall equinox, because the day is artificially lengthened a few minutes at each end by the refractive effect of the atmosphere, for a total of seven minutes. It is not until three or four days later that the day equals the night.

It is easier to see the scallop of a partial eclipse above the horizon at sunrise or sunset than it is to see a total eclipse, because the Sun is so much brighter than the Moon.

       

The rings around Saturn were first identified by astronomer Galileo Galilei in 1610. It was, however, Dutch Physicist Christian Huygens, who in 1659, recognized them as a broad, flat, thin ring, separated from the body of the plant.

In 1675, the Italian Astronomer G.D. Cassini identified two rings around it. Until 1969, it was believed that there were just three rings around Saturn “A”, “B”, and “C” and 151; “A” being the outermost and “C”, close to the planet. In 1969, the fourth ring was discovered by Pierre Guoria and soon, another one was also identified.

Pioneer satellite Data (1971) had indicated that was one more ring (“F”). French Astronomer, Edourd Albert Roche in 1849 postulated that the rings were the remnants of satellite that strayed too close to Saturn and due to which reason, disintegrated. His theory was that, if a satellite approaches, it’s primary, closer than a certain distance (known as “Roche Limit’ & 151; 2.44 times the radius of the planet), the satellite would break up and the broken pieces would gradually get distributed around the planet in a circular path.

The distances of the rings of Saturn are within the “Roche limit”. This would suggest that the rings are the remnants of a disintegrated satellite only.

The present thinking is that the rings are made up of countless small objects (varying in size from very small grains to small chunks of rocky material, covered by ice) and that each revolves around Saturn in its own orbit like a satellite.

That the rings contain particulate matter has been confirmed by  the fact that Rings “A” and “C” exhibit certain transparency due to which, the body of Saturn could he seen through them, as also the light from the stars.

 Furthermore, the satellites of Saturn are not completely eclipsed too, when they pass into the shadow of the rings. Very little information is available as to the precise composition of the matter in the rings. As per the observations of C.P. Kupier (1952), the Infra Red Spectrum is similar to the reflection spectrum of hoar-frost.

It is quite likely that these particles must have been of much bigger size earlier (even some metres in diameter), but these might have been a continuous reduction in their sizes due to their abrasion with objects like the meteoroids. Scientists are of the view that the continuous erosion may ultimately (at a far distant future) result in the rings slowly vanishing forever!

 

 

 

 

 

 

 

 

 

 

The overall appearance of the Moon is bright ash grey caused by the dark and bright barren rocky land, where there is no atmosphere. When viewed in a naked eye or through a telescope, there are vast basins called seas, which were filled with molten lava millions of years ago. These are the low land plains appearing dark or dusky for the naked eyes. During the final ending phase of volcanism on the Moon, numerous crators had liberated enormous quantity of glowing gases and mineral vapours through their vents, which had blown in all directions over the surface, depositing the mineral condensates in the form of micron-size glassy spherules, tear drops and other powdery forms.

The Lunar surface is full of these bright rays like deposits, which scatter-reflect the sunlight quite effectively giving it a bright appearance on surface. The combined effect of rocks and soil along with the crators and minerals like calcium, aluminum and titanium therefore give a silvery appearance to the naked eye.

 

 

 

 

 

 

 

 

 

The Moon revolves around the Earth in a period of about 27 days; it also rotates once on its axis in the same time and so it always keeps the same face towards the Earth. This phenomenon is known as captured rotation.

Inspite of the fact that the Moon’s axial rotation is equal to its period of revolution round the Earth, we can actually examine more than the half of the total surface. The reason is that Moon travels round the Earth in an ellipse, not in a circle since it takes elliptical path, the rate of axial spin remains constant, whereas orbital velocity changes and moves fastest when closest to us.

We can thus see a little round alternate edges of the Moon. Also, the lunar orbit is tilted with reference to ours, so that the Moon is sometimes north and sometimes south of the mean plane, enabling us see some way beyond alternate poles. These minor shifts, known as Librations, allow us to examine four-sevenths of the total surface. The remaining three-sevenths of the Moon is permanently hidden from our inquiring eyes.

The time taken for the moon to turn on its axis once and the time taken for it to revolve once around the earth are the same. Hence the moon shows us the same face every night. This is called synchronisis rotation or captured rotation. 

 

 

 

 

 

The angular diameter of the sun and moon is about half a degree each. The celestial objects are seen with two eyes (binocular vision). When we observe the horizon, the terrestrial surface with all its objects, such as tree, houses, roads or ground give us a perspective view (geometrical phenomenon), i.e., farther the objects smaller they appear, as they subtend smaller and smaller angles at the retina.  Through this long distance perspective, which some time extends to several kilometres, our vision is able to realize a long perceptual distance. At the end of this perspective we locate the celestial objects and realize a particular size.

On the other hand, when we view these objects in the sky, the most important perspective is absent and consequently the two eyes are left with their own power to discern a distance. This binocular distance limit in the absence of the perspective has been found to be about 500 feet, which vary slightly from person to person. This can be checked by the absence of parallax shifts of objects beyond the distance when we view with alternate eyes. Therefore the sun and moon are located at short distance. Naturally a half degree object located at a distance of about 500 feet must appear much smaller  than  a similar half degree object at a considerably long, perceptual distance realized by the sense of vision with the help of perspective.

 In order to illustrate this phenomenon, we place a large ball at a distance from the eye and a much smaller ball closer to the eye in order that the smaller one just covers the angular dimension of the larger ball. Now both the balls subtend the same angle at the eye, but to our binocular vision the larger ball at that distance appears decidedly larger and it is physically larger. Through a telescope or a camera, the sun and moon appear of the same sizes either at the horizon or over the high sky. This view also applies to star constellations at the horizon and at the high sky. Monocular vision by one-eyed people has no illusion of this nature, because they have no perceptual depth. 

 

 

 

 

 

 

 

One should not see the Sun during eclipse because the sudden change in light intensity may damage the eye.

The human eye, as a protective measure, can adjust automatically to varying light conditions - under bright illumination, as during the day, it closes partially and under dark conditions, as in the night, it opens fully. However this process of adjustment takes some time, a few minutes.

 As it is dark during a total solar eclipse, the eye is fully open to let in more light.

After totality, as the Sun emerges the increase in light intensity is so sudden that it catches the eye unawares. Being very bright it can damage the retina even in a few seconds. 

The Earth is speeding like a top and like a merry-go-round horse on a carousel that is itself riding on a larger carousel, and the whole amusement park is moving through Space.

The Earth rotates on its axis at about 460 metres per second at the equator. The speed of a trip around the Sun is about 30 km per second. Meanwhile, the solar system is in a more-or-less circular orbit around the centre of the galaxy at an average velocity of about 220 kilometres a second,  according to Facts on File Dictionary of Astronomy, and the galaxy is moving at about 19.4 kilometres a second, toward a point in the constellation Hercules called the solar apex Some authorities believe that there is also a general drift by the Milky Way and some neighbouring upper-clusters towards the Southern Cross at a speed of more than a million miles an hour. 

The eclipses of the Sun and the Moon occur during new moon and full moon respectively. A solar eclipse does not occur at every new moon, because the Moon orbits in a plane which is inclined to the ecliptic, the plane of orbit of the Earth around the Sun.

The angle between the planes is about five degrees and hence the Moon can pass well above or below the Sun. The line of intersection of the planes is called the line of nodes.

There are only two points where the Moon’s orbit intersects the ecliptic plane. The nodes move along the orbit from west to east, going completely around the ecliptic in about 19years.

For an eclipse to occur, the Moon has to be near one of the nodes. This does not happen on all new moon and full moon days.

 

 

 

 

 

 

            Once in a Blue Moon… is a common way of saying not very often, but what exactly is a Blue Moon? It is the second Full Moon to occur in a single calendar month. The moon goes through one complete cycle every 29.5 days, but the solar calendar months are longer – usually 30 or 31 days. This makes it very unlikely that any given month will contain two Full Moons, though it does sometimes happen: If you have a full moon on the first or second day of the month, a second full moon will occur at the end of the month.

The well-known Metonic cycle of lunar phases is 19 years long. During this time, there are 235 lunar months, and hence 236 Full Moons. There are also 228 calendar months, so at least 8 of those months must have seen two Full Moons. So, we can define Once in a Blue Moon as a probability: 8 chances in 228, or about 3.5 per cent!

Thus every 19 years or so a single year will offer two Blue Moons. In 1999, when the next double-Blue-Moon bonanza rolls around, February will have no full moon, but January and March will both boast a full moon and a bona fide Blue Moon. There are several other meanings ascribed to the term “blue moon” (the most common being “an uncommon event”) According to  reports, when the Indonesian volcano Krakatoa exploded in 1883, its dust turned sunsets green and the moon blue all around the world for the best part of two years. In 1927, a late monsoon in our country set up conditions for a blue moon.

Even by the 19th century, it was clear that although visually blue moons were rare, they did happen from time to time. So the phrase “once in a blue moon” came about. It meant then exactly what it means today: that an event was fairly infrequent, but not quite regular enough to pinpoint.” Some of the recent/upcoming blue moons: January 31, 1999; March 31, 1999; December 30, 2001; July 31, 2004; June 30, 2007 and December 31, 2009.

 

 

 

 

 

 

 

            The stars seem to twinkle, because we see the stars through the ocean of air, the atmosphere. The twinkling is caused by differences in temperature in the air. Some layers of air hotter than others, and one layer is always swirling and moving through another. These different layers of air bend the star light in different ways, and at different angles. It is this passing through layers of air of different temperature that makes the light of the stars unsteady.

The stars near the horizon seem to twinkle much more than those high in the sky. This is because the light of these stars has to travel a longer path through a thicker layer of atmosphere, and thus has more chance to become disturb. Sometimes the stars twinkle much more than they do at other times. This is true because at sometimes the atmosphere is not so still as it is at other times, or because there is not such a variation of temperature within its different layers.

Planets do not twinkle, ordinarily, but seem to shine with a steady, unwavering light. Even through telescopes, the biggest stars appear simply as tiny points of light, while the planets show very definite discs and surfaces. Hence, more rays come to us from the surface of a planet than from the surface of a star. The light from the planets does not waver as much as that from the stars the wavering of one light is counteracted by the wavering of another ray in another direction. If one could climb up above the atmosphere surrounding the earth and then look at the stars, he would see them shining with a clear and steady light, with no suspicion of twinkling.

When a ray of light travels from one optical medium to another, there is a deviation from its original path. This phenomenon is called refraction. If a light ray travels from an optically rarer medium to an optically denser medium, the light ray always bends towards the normal. The normal is nothing, but an imaginary line drawn at the point of incidence.

 The atmosphere of earth consists of a number of parallel layers of air with varying densities. Such that, the densest layer of air is near the surface of the earth. Layers with decreasing order of densities occupy the successive layers, and the top most layers are the least dense layer.

Light rays originating from a star (say x), pass through the atmosphere, before reaching the observer. In doing so, the light bends towards the normal, thereby deviating from its path slightly. This deviation takes place each time the light ray travels from a less dense layer to a denser layer. Finally when the refracted rays reach the observer, it traces a straight line path. To the observer, it appears to come from a pointy, which is higher in horizon. The pointy only gives an apparent position of the star.

The parallel layers of air are not stationery, but constantly intermingle with one another, thereby rapidly changing their densities. These changes give rise to the change in the apparent position of the star. As long as the star is within the line of sight of the observer, it is visible, but when the image falls outside the line of sight it is no longer visible. These changes in the apparent position of the star give rise to the “blinking” or “twinkling” effect.

Planets on the other hand are close to the earth, as compared to the stars. Their apparent position also changes with the changes in the densities of the air layers. But, the size of their apparent image being fairly large, seldom falls outside the line of sight of the observer. Hence they do not blink.

 

 

 

 

 

 

            The time of rising and setting of any celestial body is a function of its position in the sky defined by right ascension and declination in the celestial coordinate system, position of the observer on the Earth and the zenith distance of the body adopted to define the phenomena. Due to Earth’s motion in its orbit around the Sun, the geocentric right ascension of the Sun increases at the rate of 1 degree per day with slight variation during the course of the year.

            However, the declination of the Sun varies from about 23.5 degree south in winters to 23.5 degree north in summer during the course of the year. The rate at which the declination varies changes very much from about 0.4 degree on vernal equinox to 0 degree on summer and winter solstices. The longest day occurs in the Northern hemisphere when the declination of the sun is maximum north on summer solstice.

Around the time the daily rate of change in declination goes through zero value. Therefore, around this time the rising and setting times are affected mainly due to change in right ascension which can be about 1/2 degree from sunrise to sunset. It is for this reason that earliest sunrise does not coincide with latest sunset for a given place.

The difference is more pronounced for places in lower latitudes on earth over which the diurnal path of Sun is at a greater inclination to the horizon and its motion in right ascension takes it more to the East, away from the horizon. 

Yes, the sun too rotates about its axis. But unlike the earth, which has rotation period of one day, the sun has a ‘differential rotation’.

 That is, all parts of the sun do not have the same period of rotation. The period of rotation near its equator is 26.9 days, at sun spot zone (16 degrees north) it is 27.3 days and at the ole it is 31.1 days (syndical).

The sun’s enormous core temperature of 15 million degree Kelvin and a surface temperature of 6,000 degree Kelvin leave all its constituents in a high pressure, gaseous state called plasma. For the purpose of certain calculations, the top and the bottom ends of the visible sphere of the sun are designated as north and south poles respectively.

Photographs are taken daily and the movements of the spots, filaments and plages are observed for various latitudes and longitudes, for a long period of time. From this, the sidereal rotation period is calculated. The reason behind this phenomenon is still a puzzle to solar physicists.

            The planets are believed by many authorities to have coalesced from a disk-shaped cloud of gas early in the evolution of our solar system, beginning roughly 5 billion years ago, said Joe Rao, Lecturer at the Hayden Planetarium of the American Museum of Natural History in New York.

            “We believe that the sun and planets evolved from a huge, swirling cloud of gas and dust that  condensed over a time span of hundreds of millions of years”, Rao said. “This gas cloud was very likely in the shape of a disk, and when the planets came to be within this cloud, they pretty much all formed basically along the same plane.”

There is a notable exception the tiny planet Pluto, which has an orbit that is tipped as much as 17 degrees to the plane of the solar system, Rao pointed out. It has been hypothesized that Pluto might be everything from an escaped moon of Neptune to a special type of minor planet or asteroid. The anomalous orbit of Pluto was one of the reasons for the great debate earlier this year concerning Pluto’s exact status as a member of the solar system, Rao said.