Terrestrial-based telescopes served as the foundations of astronomical discoveries for centuries. However, with the dawn of the space age, a new chapter in astronomical observation has unfolded, ushering in space-based telescopes. Unhindered by the Earth’s atmosphere, these instruments offer substantial advantages over their ground-based counterparts and have contributed to groundbreaking discoveries about the universe.
Bypassing Atmospheric Disturbances
The most significant advantage of space-based telescopes lies in their ability to overcome the blurring effects of Earth’s atmosphere. On Earth, atmospheric turbulence scatters incoming light, causing ‘twinkling’ of stars – a phenomenon known as astronomical seeing. This distortion curbs the clarity and resolution of images captured by ground-based telescopes.
In contrast, the Hubble Space Telescope, launched in 1990 and orbiting beyond Earth’s atmosphere, has provided astronomers with stunningly detailed and clear images of the universe. For example, it captured the famous “Pillars of Creation” image in the Eagle Nebula and tracked distant supernovae to provide evidence for the accelerating universe theory, leading to the discovery of dark energy.
Telescopic observations on Earth are frequently interrupted by weather conditions and day-night cycles. In contrast, the Kepler Space Telescope, positioned in an Earth-trailing heliocentric orbit, monitored over 150,000 stars in its field of view for slight brightness dips, indicating possible planetary transits. Its continuous, long-duration monitoring led to the confirmation of over 2,600 exoplanets during its mission.
Unrestricted Access to the Electromagnetic Spectrum
Certain portions of the electromagnetic spectrum, such as gamma rays, X-rays, and ultraviolet light, are absorbed by Earth’s atmosphere and thus inaccessible to ground-based telescopes. Space telescopes can observe these wavelengths, providing invaluable insights into the high-energy universe. The Chandra X-ray Observatory and the Fermi Gamma-ray Space Telescope have revolutionized our understanding of phenomena like supernovae, neutron stars, and black holes, by providing detailed images and data in the X-ray and gamma-ray wavelengths.
Comprehensive Sky Coverage
Unlike their ground-based counterparts, space telescopes are not limited by geographical boundaries or atmospheric conditions, enabling them to potentially provide full-sky coverage. The Planck Space Observatory, launched by the European Space Agency, mapped the entire sky to study the cosmic microwave background—the oldest light in the universe—leading to a refined estimate of the universe’s age, composition, and evolution.
Eliminating Light Pollution
Space telescopes are immune to terrestrial light pollution, which poses a significant challenge for ground-based telescopes. For instance, the Transiting Exoplanet Survey Satellite (TESS), launched by NASA, is dedicated to searching for exoplanets around the brightest stars in the sky. Unhindered by light pollution, TESS can make highly sensitive measurements and has discovered dozens of exoplanets to date.
Planetary Defense and Early Warning Systems
Space-based observatories also play a critical role in planetary defense. For example, NASA’s Near-Earth Object Observations (NEOO) Program utilizes both ground and space-based telescopes to detect and track potentially hazardous objects. The Near-Earth Object Surveyor mission, plan for launch in 2028, is a space-based infrared telescope, which is intended to accelerate the rate of such detections.
Despite the logistical and financial challenges inherent in deploying and maintaining space-based telescopes, their advantages are manifold. By circumventing the limitations of terrestrial observation, space telescopes have unveiled a clearer, broader, and deeper view of the cosmos. This expanded perspective continues to drive astronomical discovery, deepening our understanding of the universe’s many mysteries.