My Science School

What is the solar wind?

The solar wind is solar radiation in the form of a steady stream of electrically charged particles mostly protons and electrons which pours out of the Sun at the speed of upto 150,000 km/sec. The particles are however smaller than atoms.

What happens when the solar wind hits the Earth?

The solar wind is deflected by the Earth’s magnetic field and does not touch the Earth. The deflected solar wind streams behind the Earth similar to a cometary tail.

Does the Solar wind have any effect on the Earth?

Since the particles of the solar wind are electrically charged, they tend to move towards the Earth’s magnetic poles, making the sky in the Polar Regions glow in vivid patterns called aurorae.

 

 

 

What is the solar limb?

The solar limb is the edge of the Sun’s disc.

 

 

 

 

 

 

 

 

 

What is the solar atmosphere?

The portion of the Sun lying in the region outside the limb is called the solar atmosphere.

Is the solar atmosphere normally visible from the Earth?

No. The intense brightness of the Sun’s disc prevents us from seeing anything else in the vicinity. The solar atmosphere can however be seen during a total solar eclipse when the Sun’s disc is totally covered by the Moon.

What is the nature of radiation from the Sun?

Radiation from the Sun travels in waves of energy. There are different types of waves depending on wavelength, such as light, X-rays, gamma rays, radio waves etc.

Can all types of radiation from the Sun be detected on the Earth?

We can see light rays and feel heat rays. Ultra violet rays tan our skin.

Radio waves can be detected by instruments. But almost all the other rays from the Sun are absorbed by the earth’s atmosphere before they reach the Earth’s surface and are detectable only by instruments placed on artificial satellites outside the Earth’s atmosphere.

 

 

 

 

 

How much matter is converted to energy to produce the Sun’s radiation?

About four million tons of hydrogen is consumed per second to produce the Sun’s radiation which proliferates steadily in every direction.

 

 

 

 

 

 

 

What proportion of the Sun’s radiation reaches the Earth?

About one billionth of the Sun’s radiation reaches the Earth and the rest streams off into space in all directions.

 

 

 

 

 

 

 

What is the significance of the absorption of the Sun’s rays by the Earth’s atmosphere?

Some of the Sun’s radiation is harmful to life on the Earth. Hence the Earth’s atmosphere acts as a protective shield by absorbing harmful radiation of the Sun.

What happens in a hydrogen bomb explosion?

In a hydrogen bomb explosion, hydrogen atoms are subjected to collision under tremendous pressure, resulting in their being merged or fused to from element helium. In the process, also called fusion reaction, large quantities of energy area released in the form of heat, light, X-rays, microwaves, gamma rays etc.

At what rate is the hydrogen being consumed in the nuclear reactions taking place in the Sun?

About six hundred million tons of hydrogen is consumed per second.

Has the hydrogen fusion reaction started in Jupiter, the largest planet in the Solar System?

Some astronomers believe that the hydrogen fusion reaction occurs within Jupiter’s core because Jupiter radiates more heat than can be accounted for by conventional explanations. However, Jupiter does not have enough mass to glow and needs to be over a hundred times larger than it is now become a star.

 

How is the tremendous pressure created in the Sun for sustaining the fusion reaction continuously?

 Hydrogen will convert to helium only under tremendous pressure. Such pressures can be sustained in laboratories on the earth only for a brief instant during which a hydrogen bomb explosion takes place for as fraction of a second.

However, the Sun sustains this pressure continuously and so the explosion is continuous. Due to the enormous gravity of the Sun, the pressure inside the Sun is about 100 billion times the pressure of the earth’s atmosphere and is sufficient to sustain a continuous fusion reaction.

Why the diameter of the Sun relativity is steady and why is its mass not scattered as in a normal explosion?

The large mass of the Sun creates tremendous gravity which forces all the mass towards the centre of the Sun. The centre of the Sun is subject to tremendous heat and pressure, enough to sustain a continuous hydrogen bomb explosion. The explosion acts as an outward force throwing the mass away from the centre of the Sun while the gravity of the Sun acts as an inward force pushing back the mass towards the centre of the Sun. If the two forces are in equilibrium, the Sun would neither expand nor contract. This is what is actually happening. Hence, the Sun’s size does not change appreciably.

 

What is the Sun made up of?

Hydrogen, the most abundant element in the Universe, is also the main constituent of the Sun, with most of its mass concentrated towards its centre.

Is the Sun a ball of fire?

In an ordinary fire, oxygen combines with various fuels, releasing heat and light. However, the fire in the Sun is not an ordinary fire but is similar to a continuous hydrogen bomb explosion, wherein a small quantity of matter is converted into an enormous quantity of energy in a conversion process that is ten million times more effective than ordinary combustion.

 

How long does the Sun take to complete one revolution around the centre of the Milky Way galaxy?

About 225 million years. This is also called the cosmic year or cosmological year.

What was the stage of evolution of the Earth one cosmic year ago?

One cosmic year ago ‘Coal Forests’ still existed on the Earth, which was later transformed into coal deposits. Human beings had not yet appeared on the Earth.

 

 

 

 

How large is the Sun compared to the earth?

The Sun’s mass is 333,000 times that of the Earth. However, average density of solar matter is only one fourth that of Earth. Hence more than a million Earths would fit inside the Sun. Also, 1098 Earths would have to be placed side by side to equal the diameter of the Sun which is 1,392,000 km.

 

 

 

 

 

 

What is the period of spinning of the Sun about its axis?

Since the Earth’s surface is solid, all parts on its surface rotate in unison. However, since the Sun is appreciably gaseous, it rotates faster in its equatorial region than in its polar regions.

Is the Sun’s axis titled to the plane of the Earth’s orbit?

Yes, by about 70.

Does the Sun have a magnetic field?

Yes.

What is the temperature of the Sun?

The temperature of the Sun is about 60000C near the surface and about 14 million degrees Celsius at the core.

What is the distance between the Earth and the Sun?

The distance between the Earth and Sun varies from a maximum of 152*106  km at aphelion to a minimum of 147*106 km at perihelion. The average or mean distance is therefore about 149.6*106 km.

If we could ‘fly’, in our imagination, how long would it take to reach the Sun?

At the speed of the Concorde, the fastest passenger plane, it would take less than three hours to fly from New York to London, but to fly a distance equal to that between the earth and the Sun, it would take nearly eight years.

What percentage of the total mass of the Solar System is contributed by the Mass of the Sun?

Over ninety-nine per cent.

Can the Sun ever be seen steadily with the naked eye?

Seeing the Sun steadily with the naked eye will cause permanent damage to the eye except during a total solar eclipse. It can, however, be viewed through special filters which make the Sun appear darker.

At what speed is the Sun moving as it orbits the Milky Way galaxy?

About 275 km/sec.

How long it take the light from the Sun to reach the Earth?

Just under eight and half minutes.

 

What is albedo?

Albedo refers to the proportion of incident light reflected back in all directions from the surface of a body. A perfect reflector has an albedo of 1, and a perfect non-reflector has an albedo of 0. The term usually applied to celestial objects within the solar system. A planet with clouds and atmosphere will have a higher albedo. The Moon has an albedo of 0.07 as it absorbs 93% of the sunlight falling on it and reflects the Balance 7%. The albedo of atmosphere less Mercury is 0.06, while Earth and Venus have albedos of 0.39 and 0.76 respectively.

 

 

What is the effect of albedo on the reflecting body?

The body heats up on absorbing the incident radiation. Hence a planet with a low albedo would warm up more, when sunlight falls on it.

What are the objects near zero albedos?

Some of the asteroids have up more, when sunlight falls on it.

 

What is the empty focus?

An ellipse has not focus but two foci, one at each end. Kepler’s laws specify the Sun focus of the planet’s elliptical orbit.

The other focus of the elliptical orbit is referred to as the empty focus. The distance between the empty focus and the aphelion point is equal to the distance between the sun and the perihelion point.

 

 

 

 

Which planet has a red spot?

Jupiter has a large red spot which keeps shifting and changing. The spot is believed to be an area of permanent turbulence.

What are Kepler’s Laws of Planetary Motion?

Kepler’s Laws of Planetary Motion state:

1. The orbit of a planet is an ellipse with the Sun as one focus of the ellipse.


2. The planet moves in its orbit at such a velocity that its radius vector sweeps out equal areas in an equal interval of time.


3. The orbital period squared is proportional to the mean distance from the Sun cubed.

These laws apply to all the planets including Uranus, Neptune and Pluto,

Planets discovered long after Kepler’s death.

Do Kepler’s laws equally apply to comets and asteroids also?

Yes. According to Kepler’s law comet spends most of its time moving very slowly and bursts into high speed only during its perihelion passage.

 

How far away are the moons Phobos and Deimos from Mars.

The moons are very close to Mars. Deimos is about 20,000 km away and Phobos is less than 6,000 km away.

Name the English satirical writer who predicted the existence of the moons of Mars?

Johnathan Swift predicted the existence and the characteristics of the moons of Mars in his book Gullivers Travels, 142 years before the moons were discovered.

What is unusual about the period of revolution of the two moons of Mars?

Phobos orbits once in 7 hours and 40 minutes and Deimos once in 30 hours. The inner moon Phobos orbits the planet faster than the spinning motion of the planet. The outer moon Deimos remains above a given landscape for nearly three days passing through all its phases twice.

Phobos not only rises in the sets and in the east but it rises and sets twice each day. It is thought to be an asteroid captured by Mar’s gravity.

What is the synodic orbital period of a planetary moon?

The synodic period of a planetary moon is the period from one new moon to the next. For the moons of Mars it is 7 hours 39 minutes and 21 minutes for Deimos.

 

 

Continue reading "The Planets"

 

 

What is the problem in observing features on the surface of Venus?

Venus is permanently covered with a cloak of dense clouds of sulfuric acid drops and carbon dioxide. Hence no features on the surface are visible on visual observation. However, such features can be observed by instruments.

 

 

 

 

 

 

 

Which planet is known as the ‘Red planet’?

Mars. The colour is caused by large deposits of red iron oxide on the surface of the planet.

How hot is it on the surface of Mars?

The temperature on the surface of Mars can vary from 250 C at night.

 

 

What is the obvious snag in locating features on the gas giants Jupiter, Saturn, Uranus and Neptune?

Being gaseous planets, the rotation of the equatorial zone is faster than at the higher latitudes. Also there are no fixed reference points in the constantly shifting clouds of gas.

Is the size of a planet related to its rotation?

No. For example, Jupiter’s day is only 9 hours 50 minutes even though it is by far the largest planet.

How big is Jupiter, in general terms, as compared to the other planets of the Solar System?

If Jupiter was hollow, all the other planets of the Solar System could be accommodated within it. It is the largest in the Solar system. Its equatorial diameter is 142,800 km and it has a mass more than twice that all the other planets combined.

Why was the astronomer Galileo persecuted by the Catholic Church?

 Viewing Jupiter through his telescope, Galileo discovered it had four moons revolving around it. This went against the Church doctrine of that time that all heavenly bodies revolved around the Earth which was held to be the centre of the Universe.

Which planet has a permanent large red spot on its surface which keeps changing and shifting?

Jupiter. The spot is believed to be an area of permanent turbulence.

What are the Galilean Moons?

The four moons of Jupiter discovered by Galileo are called the Galilean moons.

How powerful a telescope is required to observe the Galilean moons of Jupiter?

The Galilean moons of Jupiter can be seen with a good pair of modern binoculars.

 

Why does the Sun rise in the east and set in the west on the Earth? Does the concept hold equally good for all the planets in the Solar System?

The Earth spins on its axis from west to east. Hence the sky appears to move from east to west. In the case of the other planets, the Sun will rise in the east to west. In the case of the other planets, the Sun will rise in the east and set in the west, when viewed from the surface of that particular planet, only if that planet is spinning in the same direction as Earth, with respect to the Sun. In all the planets the Sun rises in the east and sets in the west. In the case of Venus, Uranus and Pluto, the Sun rises in the west and sets in the east, since the planets spin in the west and sets in the east, since the planets spin in the opposite direction.

 

 

 

 

 

 

Are all planets oblate spheroids?

All the planets exhibit oblate spheroidness to some degree, the extent of which increases with increasing speed of spinning and decreases with increasing density. Consequently, a gaseous planet with a rapid axial rotation like Saturn exhibits a very high degree of oblate spheroidness. For example, Jupiter whose day is less than 10 hours has its diameter over 140,000 km at the Equator and less than 133,000 km at the poles.

 

Do all planets have satellites?

Mercury and Venus have no satellites. Earth has one satellite (the Moon), Mars and Neptune have two satellites each. Uranus has five satellites. Jupiter and Saturn have a large number of satellites. Pluto has one satellite.

 

 

 

 

 

 

Can a satellite be larger than a planet?

A satellite is much smaller than the planet around which it revolves. However, a large planet is capable of having a large satellite. Titan, one of the satellites of Satum, and Triton, a satellite of Neptune, are larger than the planets Mercury or Pluto.

 

 

 

 

 

 

 

 

Does the period of spinning remain the same for all the planets?

The day of each planet is different. For example, the period of one day for Mercury is 59 Earth days; for Venus, it is 243 Earth days and for Mars, it is about 24-1/2 Earth hours. Thus a large variation in the period of spinning is due to random collisions with comets and asteroids over very long periods.

Can all the planets be seen from Earth with the naked eye?

Neptune and Pluto can be seen only with telescopes. The other planets, including a faint Uranus, can be seen with the Naked eye.

Astronomers in ancient times were hence unaware of the planes beyond Saturn since they did not have telescopes.

When the planets beyond Saturn were first discovered?

In 1781, Sir William Herschel discovered the Existence of the planet Uranus. It is twice as far out as the sixth planet Saturn.

Which planet is farthest from the Earth?

The eccentric orbit of Pluto regularly brings it closer to the Sun than Neptune. Hence Neptune and Pluto will take turns to be the farthest planet from time to time.

Do all the planets have an atmosphere similar to that of the Earth?

Mercury and Pluto have no atmosphere. The other planets have atmospheres containing different gases. Earth’s atmosphere, containing mainly nitrogen and oxygen, is unique. Venus has a carbon dioxide atmosphere. The atmosphere of Mars is mainly argon and carbon dioxide. Jupiter, Saturn, Uranus and Neptune have thin atmospheres containing hydrogen, helium and methane.

Why are Mercury, Venus, Earth and Mars Called “Terrestrial” planets?

“Terrestrial” means Earth-like. All the terrestrial planets have large, solid, metallic cores surround by a rocky outer layer. All of them have atmospheres.

Why Jupiter, Saturn, Uranus and Neptune are called “Gas Giants”?

The gas giants or Jovian planets do not have any significant solid cores and are almost entirely composed of gases or liquefied gases. They are also enormous in size compared to the other planets.