New Delhi, March 17: Ultraviolet light, commonly known as UV rays, is a specific type of electromagnetic wave. Its wavelength is shorter than that of visible light, making it invisible to the human eye. However, some creatures in nature, such as bees and butterflies, possess the remarkable ability to see it.
The science of UV light is not only linked to skin protection but also aids in understanding the depths of the universe. These invisible rays present in sunlight are essential for life but can also cause harm with excessive exposure. Scientists are continuously studying them to gain a better understanding of both the universe and Earth.
The sun is the largest natural source of UV light. Scientists categorize the UV rays emitted by the sun into three main types: UVA, UVB, and UVC. Among these, UVC is the most dangerous, but the Earth’s atmosphere absorbs it almost entirely. UVB rays can cause sunburn and damage the DNA of living organisms. Fortunately, the ozone layer blocks about 95% of UVB rays. UVA rays have the longest wavelengths and can penetrate the skin deeply, leading to aging.
Astronomers further divide UV light into finer categories, such as Near UV (NUV), Middle UV (MUV), Far UV (FUV), and Extreme UV (EUV). NASA’s Solar Dynamics Observatory (SDO) spacecraft has captured extreme UV images of the sun. In these false-color images, different colors represent the temperatures of the sun’s hot plasma gases. Red indicates around 60,000 degrees Celsius, while blue and green represent much hotter areas, exceeding one million degrees Celsius.
German scientist Johann Ritter discovered UV light in 1801. He observed that photographic paper darkened quickly under blue light. When he placed the paper beyond violet light, it darkened even faster, proving that energy exists beyond violet, which was later termed ultraviolet. The Earth’s atmosphere mostly blocks high-energy UV rays, prompting scientists to use satellites to study UV light from the sun and other stars and galaxies.
Newly formed stars predominantly shine in UV light. NASA’s Galaxy mission captured UV images of the M81 galaxy, clearly showing areas where new stars are forming. During the Astro-2 mission, NASA’s Ultraviolet Imaging Telescope took pictures of three galaxies. In UV light, new, massive, and hot stars are visible, while older, cooler stars are more apparent in visible light. This provides scientists with vital information about galaxy evolution and the birth and death of stars.
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