তারার দূরত্ব নির্ণয় পদ্ধতি Method of measuring distance of stars, galaxies and space in bangla Ep45

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This video about Method of measuring the distance of stars, galaxies and space in bangla with animation and also what is light year.
Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines.Due to foreshortening, nearby objects show a larger parallax than farther objects when observed from different positions, so parallax can be used to determine distances.
To measure large distances, such as the distance of a planet or a star from Earth, astronomers use the principle of parallax. Here, the term parallax is the semi-angle of inclination between two sight-lines to the star, as observed when Earth is on opposite sides of the Sun in its orbit.[a] These distances form the lowest rung of what is called "the cosmic distance ladder", the first in a succession of methods by which astronomers determine the distances to celestial objects, serving as a basis for other distance measurements in astronomy forming the higher rungs of the ladder.

The light-year, alternatively spelled lightyear, is a unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (9.46×1012 km) or 5.88 trillion miles (5.88×1012 mi).[note 1] As defined by the International Astronomical Union (IAU), a light-year is the distance that light travels in vacuum in one Julian year (365.25 days).Because it includes the word "year", the term light-year is sometimes misinterpreted as a unit of time.

There are several types of 'standard candle' objects for which we can predict the luminosity from some other measurement. Two of the most important are Cepheid variable stars and type 1A supernovae.

1. Cepheid variables:
Cepheid variables are a special type of star with a luminosity which varies on a regular cycle. Around 1908, Henrietta Leavitt discovered that the period of the variability was closely linked to the luminosity of the star.So, if you time the variability of a Cepheid then you can predict its luminosity. And if you know its luminosity and how bright it appears from Earth, then you can calculate the distance.

2. Type 1A supernovae:
Supernovae occur when massive stars explode at the end of their lives. A white dwarf star in a binary pair with a red dwarf star steals mass from the
red dwarf until it is too massive to support itself against gravity any more.Then its core collapses, starting a runaway nuclear reaction and a brightexplosion. Because the collapse always happens at the same mass, the luminosity of the explosion is always the same. From this known
luminosity we can estimate the distance.

#TimeDilation #ParallaxMethod #StandardCandle #Astronomy #Supernova #StarDistance #Physics

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Attribution:
TED-Ed
Johnny Harris

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