Advertisements
Advertisements
प्रश्न
How many astronomical units (A.U.) make 1 parsec?
Advertisements
उत्तर
1 A.U. long arc subtends the angle of 1 s or 1 arc sec at distance of 1 parsec.
Thus, angle 1 sec = `(1 A.U.)/1` parsec
Thus, 1 parsec = `(1 A.U.)/1` arc sec
Thus, 1 parsec = `(630(3600))/11`
= 206182.8
= 2 × 105 A.U.
APPEARS IN
संबंधित प्रश्न
The principle of ‘parallax’ in section 2.3.1 is used in the determination of distances of very distant stars. The baseline AB is the line joining the Earth’s two locations six months apart in its orbit around the Sun. That is, the baseline is about the diameter of the Earth’s orbit ≈ 3 × 1011m. However, even the nearest stars are so distant that with such a long baseline, they show parallax only of the order of 1” (second) of arc or so. A parsec is a convenient unit of length on the astronomical scale. It is the distance of an object that will show a parallax of 1” (second) of arc from opposite ends of a baseline equal to the distance from the Earth to the Sun. How much is a parsec in terms of meters?
Just as precise measurements are necessary in science, it is equally important to be able to make rough estimates of quantities using rudimentary ideas and common observations. Think of ways by which you can estimate the following (where an estimate is difficult to obtain, try to get an upper bound on the quantity):
the number of strands of hair on your head
What are the S.I. units of
- mass
- length
- time and
- temperature.
Write their names and symbols.
A hand span is a reliable measure of length.
Complete the analogy.
Height of a person: cm :: Length of your sharpened pencil lead:______?
Match the following.
| 1. | Length | kelvin |
| 2. | Mass | metre |
| 3. | Time | kilogram |
| 4. | Temperature | second |
Difference in size 
Do this for yourself and find the difference.
Now cut strips of equal sizes out of it. Using tape join the strips, end to end, to make a belt.
How long is your belt? _________
Can you think of how to cut a postcard so that you can pass through it?
There are two beautiful lakes near a village. People come for boating and picnics in both the lakes. The village Panchayat is worried that with the noise of the boats the birds will stop coming. The Panchayat wants motorboats in only one lake. The other lake will be saved for the birds to make their nests.
- Find the area of lake B on the drawing in square cm. What is its actual area in square km?
Give some examples of larger length measures.
SI unit of electric current is ______.
Yard was used as the unit of length.
Mars has approximately half of the earth’s diameter. When it is closest to the earth it is at about 1/2 A.U. from the earth. Calculate what size it will appear when seen through the same telescope.
In the parallax formula D = b/θ, what must be true about the angle θ for the calculation to be correct?
What is the SI unit of length?
One parsec is defined as ______.
