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ਇੱਕ ਪ੍ਰਕਾਸ਼ ਸਾਲ (ਚਿੰਨ੍ਹ: ly) ਲੰਬਾਈ ਮਿਣਨ ਦਾ ਇੱਕ ਸਾਧਨ ਹੈ। ਇੱਕ ਪ੍ਰਕਾਸ਼-ਸਾਲ ਲੱਗ-ਭੱਗ 10 ਅਰਬ ਕਿਲੋਮੀਟਰ ਦੇ ਬਰਾਬਰ ਹੂੰਦਾ ਹੈ। ਇੰਟਰਨੈਸ਼ਨਲ ਐਸਟਰੋਨੋਮੀਕਲ ਯੂਨੀਅਨ ਦੇ ਮੁਤਾਬਕ ਰੋਸ਼ਨੀ ਇੱਕ ਸਾਲ ਵਿੱਚ ਜਿੰਨਾ ਸਫਰ ਤਹਿ ਕਰਦੀ ਹੈ, ਉਸ ਲੰਬਾਈ ਨੂੰ ਇੱਕ ਪ੍ਰਕਾਸ਼-ਸਾਲ ਕਹਿੰਦੇ ਹਨ।[1] ਪ੍ਰਕਾਸ਼-ਸਾਲ ਨੂੰ ਤਾਰਿਆਂ ਦੀ ਦੂਰੀ ਦਾ ਪਤਾ ਕਰਨ ਲਈ ਵਰਤਿਆ ਜਾਂਦਾ ਹੈ।
ਇੱਕ ਪ੍ਰਕਾਸ਼-ਸਾਲ:
ਉੱਪਰ ਲਿਖੇ ਅੰਕੜੇ ਜੂਲੀਅਨ ਸਾਲ ਦੇ ਹਿਸਾਬ ਨਾਲ ਹਨ, ਜਿਸ ਵਿੱਚ 365.25 ਦਿਨ ਹੁੰਦੇ ਹਨ।[2] ਅਤੇ ਪਹਿਲਾਂ ਹੀ ਤਹਿ ਕੀਤੀ ਰੋਸ਼ਨੀ ਦੀ ਗਤੀ, ਜੋ 299,792,458 ਮੀਲ ਇੱਕ ਸੇਕੰਡ ਵਿੱਚ ਹੈ, ਇਨ੍ਹਾਂ ਦੀ ਵਰਤੋਂ 1984 ਤੋਂ ਹੋ ਰਹੀ ਹੈ।[3]
Factor (ly) | Value | Item |
---|---|---|
10−9 | 40.4×10-9 ly | Reflected sunlight from the Moon's surface takes 1.2-1.3 seconds to travel the distance to the Earth's surface. (The surface of the moon is roughly 376300 kilometers from the surface of the Earth, on average. 376300 km ÷ 300000 km/s (roughly the speed of light) ≈ 1.25 seconds) |
10−6 | 15.8×10-6 ly | One astronomical unit (the distance from the Sun to the Earth). It takes approximately 499 seconds (8.32 minutes) for light to travel this distance.[4] |
10−3 | 3.2×10-3 ly | The most distant space probe, Voyager 1, was about 14 light-hours away from Earth 9 ਮਾਰਚ 2007 ਤੱਕ [update]. It took that space probe 30 years to cover that distance.[5] |
100 | 1.6×100 ly | The Oort cloud is approximately two light-years in diameter. Its inner boundary is speculated to be at 50,000 AU, with its outer edge at 100,000 AU |
2.0×100 ly | Maximum extent of the Sun's gravitational pull (hill sphere/roche sphere, 125,000 AU). Beyond this is true interstellar space | |
4.22×100 ly | The nearest known star (other than the Sun), Proxima Centauri, is about 4.22 light-years away.[6][7] | |
103 | 26×103 ly | The center of our galaxy, the Milky Way, is about 8 kiloparsecs away.[8][9] |
100×103 ly | The Milky Way is about 100,000 light-years across. | |
106 | 2.5×106 ly | The Andromeda Galaxy is approximately 2.5 megalight-years away. |
3.14×106 ly | The Triangulum Galaxy (M33), at 3.14 megalight-years away, is the most distant object visible to the naked eye. | |
59×106 ly | The nearest large galaxy cluster, the Virgo Cluster, is about 59 megalight-years away. | |
150×106 - 250×106 ly | The Great Attractor lies at a distance of somewhere between 150 and 250 megalight-years (the latter being the most recent estimate). | |
109 | 1.2×109 ly | The Sloan Great Wall (not to be confused with the Great Wall) has been measured to be approximately one gigalight-year distant. |
46.5×109 ly | The comoving distance from the Earth to the edge of the visible universe is about 46.5 gigalight-years in any direction; this is the comoving radius of the observable universe. This is larger than the age of the universe dictated by the cosmic background radiation; see size of the universe: misconceptions for why this is possible. |
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