Category Astronomy

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.