From UPSC perspective, the following things are important :
Prelims level: Telescopes
Why in the News?
Modern telescopes, both on Earth and in space, expand our understanding of the universe by gathering and focusing light from distant celestial bodies, revealing cosmic secrets.
Modern Telescopes: Everything you need to know
Primary Functions and Features |
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| Purpose | • Telescopes serve as windows into space, revealing distant celestial bodies and helping explore the universe. • Their primary function is to gather more light than the human eye can, making faint objects visible. |
| Types | 1. Reflecting Telescopes: • Use mirrors to focus light and create images. • Most common in large observatories due to the use of parabolic mirrors, which prevent light scattering and offer clear images. 2. Refracting Telescopes: • Use lenses to bend and focus light (Concave and Convex lenses used) • Limited by lens size, with a maximum of about 1 meter (e.g., Yerkes Observatory). Large lenses may sag, distorting the image. |
| Primary purpose | • Telescopes are designed to collect more light than the human eye. • The light-gathering ability is proportional to the size of the aperture (opening). • Example: A small 70mm telescope collects 118 times more light than the human eye. |
Features of Telescopes |
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| Brightness and Magnitude | • Celestial objects’ brightness is measured in apparent magnitude (lower numbers = brighter). • Examples: Sun (-26.78), Venus (-4.92), Sirius (-1.46), Andromeda Galaxy (+3.44). • Small telescopes can detect objects with magnitudes up to +11.2, which are 100 times fainter than what the human eye can see. |
| Resolution and Detail | • The resolution of a telescope determines how much detail it can show. • A small telescope can resolve details 1.47 arcseconds apart (40 times more detail than the human eye, which resolves details 60 arcseconds apart). |
Why are Telescopes set up on Mountains? |
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| Mountaintop benefits | • High-altitude observatories are set up to reduce atmospheric distortion, which affects image quality (e.g., stars twinkling). • Space telescopes, like Hubble, are entirely above the atmosphere and provide clear, undistorted images. |
| Adaptive Optics | • Ground-based telescopes use adaptive optics to correct atmospheric distortions. • Lasers create artificial stars, and the telescope adjusts its mirrors to reduce twinkling. |
About the New Segmented Mirrors |
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| Overcoming Mirror Limitations | • Large mirrors (over 8.5 meters) can sag under their own weight. • Segmented mirrors solve this by using smaller sections to create larger, effective mirrors (e.g., Extremely Large Telescope (ELT) with a 39.3-meter aperture). |
| Notable Telescopes | • Large Binocular Telescope (LBT): Two 8.4-meter mirrors, combined aperture of 11.9 meters. • Extremely Large Telescope (ELT): Under construction in Chile, it will have a 39.3-meter aperture. • Subaru Telescope (Hawaii): Captured objects with a magnitude of +27.7, 100 million times fainter than what the human eye can see. |
PYQ:[2015] In the context of modern scientific research, consider the following statements about ‘IceCube’, a particle detector located at South Pole, which was recently in the news: 1. It is the world’s largest neutrino detector, encompassing a cubic kilometre of ice. 2. It is a powerful telescope to search for dark matter 3. It is buried deep in the ice. Which of the statements given above is/are correct? (a) 1 only (b) 2 and 3 only (c) 1 and 3 only (d) 1, 2 and 3 only |
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