Are stars “nocturnal” and disappear in the daytime? Of course not, they radiate light during the day as intensely as they do in the night
By Rachna Arora
Gazing into the night sky is undoubtedly one of the most ethereal experiences. Cloaked in a dark canvas studded with tiny glittering stars, the heavens remind us of the wonders and the mysteries of the majestic universe. It is very challenging to ascertain the total number of stars in the cosmos; the milky way galaxy alone is estimated to have nearly a 100 billion stars. However, about 2500 stars are visible on a clear night on earth.
Stars have some important features in common; they are gigantic, ferocious balls of gas, basically hydrogen and helium, spewing out heat and light due to nuclear fusion. There is nothing tranquil about their world despite what the nursery rhymes and songs entail.
Stars are the same, yet diverse. They can be of different colours like white, yellow, red or blue. They can be as small as a planet or so big that the sun is merely a speck in contrast but are very, very far from us.
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Sky-gazing is primarily a night time adventure. However, since centuries man has been enthralled by the notion of viewing the stars in the daytime too. Not many know that the Moon, Venus and Jupiter, which are very close to us on the cosmic scale, can be spotted with the naked eye during daylight hours, the only hurdle being one should be sure of which part of the sky to explore.
Are stars “nocturnal” and disappear in the daytime? Of course not, they radiate light during the day as intensely as they do in the night. Although our sun is an average star, neither too big nor too small, not very hot nor cold, its proximity to us makes it shine 550,000 times brighter than the full moon and makes other stars too dull (about a trillion times dimmer) in comparison. It is the bright light from the sun that prevents us from discerning the light emanating from other stars in the daytime.
Just as we cannot see the glow of a candle in a brightly lit room, similarly the dim star light can be seen in the dark background at night and is submerged in the brilliant glare of the sun and the bright blue sky during the day. If one was on the moon, which does not have an atmosphere, there would be no scattering, the sky would be dark and the stars would be visible at all times. So, basically, the visibility of the stars is all about the contrast with the surroundings.
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Man’s quest to see the stars in the day dates back to ancient times and is even documented by Aristotle. It was believed that if one gazed over a small section of sky from the bottom of a deep well, a coal pit or shaft of a tall chimney, one could see stars in the daylight. The notion was based on the fact that such a vantage point would reduce the amount of light entering the eye, make the pupil bigger allowing more light from the star to enter thus making it visible. The theory has been tested by many including the noted German scientist and naturalist Alexander von Humboldt, and it has failed every time.
So the question still remains, is the sun the only star visible in the day? No. Armed with a telescope of a large aperture, we can see bright stars in the daylight. If the star is located further from the sun in the sky, it is cloudy and if the observation is made from a high spot, daytime star-gazing becomes feasible.
The most opportune time to see stars in the day without a telescope is during a total solar eclipse. With the sun’s disc covered by the moon, the twinkling stars in the sky offer a truly exhilarating experience.
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The death of a star, when it becomes a supernova with brightness increasing a million-fold, offers a rare window of opportunity to see a star in the daytime but yet to be established.
Betelgeuse, a red supergiant, and part of the constellation Orion shall become a supernova anytime during the next 100,000 years. This will be a spectacular show with clear visibility of the star even in the daytime for about three months before it fades into a nighttime object visible for many centuries.
The possibility of seeing stars other than the sun in the daytime is surely an exotic and enchanting experience requiring precision and focus as we gaze into the infinite blue sky. It is surely an acute test of patience, perseverance, and right timing.
(The writer is PGT- Physics at Shiv Nadar School, Noida.)
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