What is the difference between the geographic poles and the magnetic poles?
The earth has a natural magnetic field and behaves as a magnet, influencing a mariner’s navigational compass. The north and south poles (magnetic) are points on the Earth’s magnetic axis. The earth spins on its geographic axis and not on its magnetic axis.
What is the speed of rotation of the Earth?
The Earth spins faster during September than during March in any year.
What are poles?
All the bodies which rotate on their axes, such as the Earth, Sun, Moon, planets, etc. are said to have two poles, called North Pole and South Pole for connivance. They are the points at which the axis of rotation intersects the surface of the body. Hence, the Earth has a north pole and a south pole, and the line passing through the centre connecting the poles is the axis of rotation of the Earth.
How are the poles identified with respect to surface features on the Earth?
The poles are imaginary points and are never identified by any natural features on the Earth’s surface.
What is the shape of the Earth?
The Earth is not a mere sphere but an oblate spheroid i.e., a sphere flattened slightly at the top and bottom (poles) and bulging at the central region. There is a little more flattening at the bottom than at the trop.
Why is the Earth an oblate spheroid rather than a sphere?
The Earth’s spinning motion causes the central region to bulge leading to flattened top and bottom.
Why is the study of the Earth significant for astronomers?
The Earth, the third planet from the Sun, is only planet that can be easily studied. A study of the Earth (as a planet) helps astronomers to understand the other planets better.
What are the “canals” of Mars?
In 1877 Italian astronomer G.V. Schiaparelli reported sighting a network of “Canali” (“Channels” in Latin) on Mars, but it was wrongly translated as “Canals” in English implying that the phenomenon is artificial. The canals of Mars are in fact only a natural phenomenon.
What are the “Rings” of Saturn?
Saturn possesses a large quantity of matter orbiting in t6he form of rings. They are classified into three major rings, A, B and C. Ring C is sometimes known by its nickname “Crepe Ring”. There is a large gap between rings A and B called the Cassini Division. The rings are made up of small blocks of matter too small to seen individually thereby creating an impression of a continuous sheet of material.
What is the true reason for the perturbations in the orbit of Mercury?
Mercury not only orbits the Sun but the orbit itself rotates.
Could the planets of the Solar System have formed differently?
It is matter of accident that the planets exist as they do. It has been postulated that the planets could have formed in a number of ways, all resulting in stable configurations.
Do the planets also twinkle?
Mercury and Venus twinkle when observed near horizon.
Is there any planet beyond Pluto?
Astronomers suspect the existence of a planet beyond Pluto (tentatively named Persephone but as yet undetected) roughly 5 times the Earth’s size, 100 a.u distant from the Sun and orbiting the Sun once in more than 1000 years.
Among the objects of one of the voyages of the famous eighteenth century British explorer Captain Cook of the South Pacific, was an astronomical. Name it.
Observation of the transit of Venus.
What are Sun Grazers and Earth Grazers?
These are small number of asteroids with highly elliptical orbits in relation to the Earth or the Sun, known as Earth Grazers and Sun Grazers, respectively.
How close to the Sun can a Sun Grazer Approach?
The notable example is the asteroid Icarus discovered in 1949 which is about 1.5 km in diameter and whose highly elliptical orbit takes it from an aphelion position beyond the orbit of Mars to a perihelion position within 28 million km of the Sun (less than half the mean distance of mercury from the Sun).
How close to the Earth Grazers approach?
Hermes, an asteroid less than 1 km in diameter, occasionally approaches the Earth within twice the Moon’s distance from Earth. Another asteroid Eros can approach the Earth within 23 million km.
What are asteroids and where are they?
Asteroids are small bodies orbiting the Sun. Almost all of them (99.8%) move in orbits between those of Mars and Jupiter, in a zone known as the Asteroid Belt.
How many asteroids exist and how many been studied so far?
About 100,000 and 2,000 respectively.
How were asteroids created?
Asteroids are supposed to represent space debris scattered by the perturbing effects of Jupiter’s gravity.
What is the estimated total mass of the asteroids?
The estimated total mass of all the asteroids is less than 0.1 per cent of the Earth’s mass.
What is the size range of the asteroids?
Asteroids generally range in diameter from less than a kilometer to about 800 km.
What are the “Morning Star” and the “Evening Star”?
Mercury and Venus, due to their inferior orbits, always appear close to the Sun and are difficult to see except in the Twilight hours. Mercury and Venus are sometimes referred to as “Morning Star” and “Evening Star”. However, they are really not stars but planets.
Why did the ancients mistake the planets Mercury and Venus for stars?
Mercury and Venus appear bright during twilight hours when the stars are usually faint. Mercury is sometimes as bright as the bright-stars Sirius. Venus appears brighter than Mercury <sometimes even ten times brighter>.
What are “Inferior” and “Superior” Planetary orbits?
Mercury and Venus are said to have inferior orbits due to their greater nearness to the Sun than Earth. The other planets which are farther from the Sun than Earth are said to have superior orbits.
What is an Astronomical Unit?
An Astronomical unit (usually abbreviated as “a.u.”) is a unit of measurement of measuring distances in the Solar System one a.u is equal to 149,597,870 km which is the mean or average distance between the earth and Sun during the elliptical orbit on the earth around the Sun.
Do the planets orbit the Sun in the same plane?
Except Pluto, the entire planet orbit the Sun nearly in the same plane. The plane of the orbit of Pluto is titled by about 170 to the mean plane of orbit of then other planets.
What is meant by “Inner” and “Outer” Solar System?
The Inner Solar System refers to the region between the Sun and Mars where the planets are relativity close together. Beyond this is the Outer Solar System, where the planets are spaced relatively wider apart.
What are the main constituents of the Solar System?
The solar System consists of the Sun and all the heavenly bodies that orbit it, such as the planets, moons, asteroids, comets, etc.
The term Solar System is also synonymously used to refer to the region of space occupied by the Sun and the other bodies of the Solar System.
Name the planets and their symbols.
The nine planets orbiting the Sun are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. Sometimes specific symbols are used to denote the planets.
Can a Heavenly body be a temporary member of the Solar System?
Yes. For example, a comet following a hyperbolic trajectory can enter the Solar System, go around the Sun Partially and leave the Solar System never to return.
Are the names of the planets usually mentioned in ascending order of their distance from the Sun?
Yes, up to Uranus. Pluto has a highly eccentric orbit which partially overlaps the orbit of Neptune. Sometimes Pluto is the outermost planet and at other times Neptune is the outermost one.
So all the planets orbit the Sun in the same direction?
Yes.
Do all the planets rotate about their own axes white orbiting the Sun?
Yes.
Newton’s Laws of Motion are:
In astrology (dating back to ancient times), only heavenly phenomena and movements visible to the naked eye are considered. Hence the planets beyond Saturn that can only be seen with telescopes do not figure in astrology. Astrology also places great importance on the visual pattern (constellations) of the heavenly objects in the night sky, whereas they are of least significance to astronomers. The heavenly objects recognized by astrologers also include objects like “Rahu” and “Ketu” considered non-existent by astronomers. The movements of the heavenly objects are believed by astrologer’s manner, whereas according to astronomers such a contention has no scientific basis and any astrological correlations are considered purely coincidental.
What is meant by “Apogee” and “Pergiee”?
Apogee (Aphelion with reference to solar orbits) is the point in the elliptical orbit at which the orbiting body is at its farthest distance from the body around which it orbits.
Perigee (Perhelion with reference to solar orbits) refers to that point where the orbiting body is closest to the body around which it orbits. For example, in the case of an artificial satellite moving in an elliptical orbit around the Earth, its distance from the Earth would fluctuate during each orbit from a maximum at apogee to a minimum at perigee.
What is a nebula?
A nebula (Plural: nebulae or nebulas) is a vast cloud of gas and dust floating in space. Nebulae are usually detected in the night sky as bright or dark patches against the background of stars.
What are galaxies?
Galaxies are clusters of stars. The Sun and the Solar System are part of a star cluster called the Milky Way galaxy visible as a cloudy white area in the night sky and commonly called “Akash Ganga” in India.
How many galaxies are there in the Universe?
It has been estimated that there are about a hundred billion galaxies in the Universe.
What are spiral, twin spiral, and multiple spiral patterns of galactic discs?
The spiral, twin and multiple spiral patterns refer to the number of ‘arms’ of the spiral.
How are galaxies classified?
Galaxies are classified as elliptical, spiral and irregular depending on the nature of distribution of stars on the galactic disc.
The more common types have a regular structure. Elliptical galaxies arre denoted by the letter E followed by a numeral having values from 0 to 7 depending on the degree of flattening of the ellipse. Spiral galaxies arre denoted by Sa, Sb, Sc, Sba, SBb or SBc according to the pattern of the spiral arms. Barred spiral galaxies are denoted by Sba, SBb and SBc. SO denotes a class intermediate between elliptical and spiral. Irregular galaxies arre denoted by Irr.
What is Gravity?
“Gravity” or “Gravitational Force” or “Gravitation” refers to the natural force of attraction between objects in space. For example, we fall down when we jump up, because our bodies are attracted by the Earth’s gravity. The Moon orbits the Earth because the Earth’s gravity holds it in place in its orbit. The Earth, the planets and the other objects in the Solar System orbit the Sun due to the gravitational force exerted on them by the Sun. It plays a vital role in the behavior of the Universe.