What units do astronomers use to measure distances in the Solar System?
Since distances are appreciably large, astronomers use a unit of distance called ‘astronomical unit’. One a.u. is equal to 149,600,000 km which is the average distance between the Earth and the Sun. The Earth is at a distance of 1 a.u. from the Sun. Mercury and Venus is less than 1 a.u. from the Sun since they are nearer to the Sun than Earth. The other planets are more than one a.u. from the Sun since they are farther from the Sun than the Earth.
How precise were ancient Indian astronomers?
According to the 4000 years old Rigveda, the solar year was 364.24675 days, the Sun was 108 Sun diameters from the Earth and the Moon was 108 Moon diameters from the Earth.
Name the five important observatories in India?
Kodaikanal, Hyderabad, Ooty, Nainital and Kavalur.
What is a “Jantar Mantar”?
A Jantar Mantar is an ancient observatory used for observing the heavens before telescopes were invented. They are found in India, Arabia and North Africa. The Jantar Mantars in Jaipur and Delhi are well known.
How do astronomers measure large distances in space?
Distances in space are measured by the method of trigonometrically parallax based on the displacement in the apparent position of an object viewed from two different positions. In principle, two observations are possible for a star, separated by a time interval of six months during which the observer on Earth moves through a distance equal to half the orbit of the Earth around the Sun. Due to parallax, the star then appears to trace out a small ellipse while the Earth’s orbit repeats another ellipse in space. Knowing the magnitude of the parallax, the Sun-star-Earth triangle can be mathematically solved to arrive at the distance of the star.
What is a parsec?
One parsec is that distance from Earth at which a star would have an annual parallax of one second of arc. 1 pc = 206265 a.u. = 3.09* 1013 km.
What units do astronomers use to measure larger distances in space?
The common units, in addition to the astronomical unit, are “Parsec” and “light year”.
What is a light year?
A light is the distance travelled by a ray of light in vacuum in a period of one year.
How can we visualize the light year in simpler terms?
The nearest star Alpha Centauri is 4.3 light years away i.e., it would take 4.3 years to reach it travelling at the speed of light. From Earth the Sun is only 8 light minutes away and Moon is just 1.3 light seconds away. New York is a mere 1/50 light second from London.
What is the relationship between parsecs and light years?
1 pc = 3.62 1.y.
1 1.y. = 0.30675 pc.
Are there any larger units for measuring distances in space?
Yes. Kilo parsecs and mega parsecs.
1 Kilo parsec = 1,000 parsecs
1Mega parsec= 1,00,000 parsecs = 106 parsecs.