Space is beautiful, fascinating, a treasure of information and infinite imaginations. Recall your childhood. As a young kid, looking at the sky, counting the stars and occasionally, if you are lucky to get to witness the falling star (meteor falling), gaze at the stars and get drowned in infinite imaginations. The fascination sows a thought in mind and starts wondering how much of it we understand? Space is home to millions of galaxies inhabited by countless celestial objects, with only a few of these have been discovered. How the universe is formed, how did Earth and other planets have their origin are many questions. Researchers believe that celestial objects like asteroids, meteoroids, and comets have hidden secrets that can help solve the universe’s mysteries. Asteroids are small, rocky objects and leftover from the formation of our solar system and orbit the sun like any other planet. Most asteroids are made of different rocks, but some have clays or metals, such as nickel and iron.
Some of these objects come close to Earth’s orbit, which makes them prone to collision. Such objects are called Near-Earth Objects. Realising the need for raising public awareness about the Asteroid and its impacts, the UN adopted a resolution to observe 30 June as International Asteroid Day. On this day, the Earth’s most significant asteroid incident, known as the “Tunguska asteroid event in Siberia”, happened. On that day, an asteroid came close to impacting Earth and luckily, it did not quite make it to the ground but exploded in the air a few kilometres up. It resulted in damaging large areas, vegetation, and animals. The damage could have been much more. More recently, on 15 February 2013, a large (~18-meter diameter and 11,000 tons in weight) fireball travelling at an estimated velocity of ~ 8.6 kilometres per second entered the atmosphere and disintegrated in the skies over Chelyabinsk, Russia. NASA puts the estimate of energy at 440 kilotons. The observation of Asteroid Day is to focus and employ all available technologies to detect and track as many as possible Near-Earth Asteroids that threaten human populations.
Astronomer Giuseppe Piazzi accidentally discovered the first and most giant Asteroid, Ceres, orbiting between Mars and Jupiter in 1801. With a diameter of 940 kilometres, Ceres is believed to be the largest object in the central asteroid belt. Asteroids orbited together and referred to as the asteroid belt. It is a torus-shaped region in the Solar System, located roughly between the orbits of the planets Jupiter and Mars. The powerful gravity of Jupiter makes minor asteroids move out from orbit. They move towards other planets in which some of the asteroids collide with each other or with other planets and make the new form of a celestial object. Because asteroids formed in different locations at different distances from the sun, no two asteroids are alike. There are several asteroids closer to Earth referred to as near-Earth objects (NEOs). Astronomers are discovering new NEOs at a rate of about 30 each week.
Most asteroids usually are at least 1.8 million miles away from Earth when they pass. In a rare instance, in 2019, two asteroids (asteroid2019 QS, 2019 OU1) passed by Earth at unusually close distances and only hours apart. Astronomers keep an eye on anything that comes within 4.6 million miles of Earth and could be “potentially hazardous.” In April 2020, Asteroid (52768) 1998 OR2 passed relatively close to Earth though at a safe distance of 6 million kilometres.
Japan Aerospace Exploration Agency (JAXA) has landed two hopping robots onto asteroid Ryugu, making Japan the first country in the world to land rovers on an asteroid. Japan’s space agency also conducted experiments by successfully dropped an explosive to create a crater on the Asteroid. Several NASA Space missions have flown by and observed asteroids. Bennu discovered in 1999 is a small near-earth asteroid that passes close to the Earth about every six years. OSIRIS-REx spacecraft studied Bennu and collected a sample of the Asteroid. It aims to gather the samples to bring back to Earth. What makes 2021 unique is the launch of the first mission dedicated to the deflection of an asteroid. NASA’s Double Asteroid Redirection Test (DART) is a test mission to begin the process of understanding how we will do this for real if it becomes necessary. DART is designed to strike an asteroid called Dimorphos and subtly shift its orbit around a giant asteroid Didymos.
Research work of scientists from India pointed out the possibility of southern peninsular India hit by an asteroid larger than the one that wiped out dinosaurs (some 65 million years ago) some 800-550 million years ago. SPACE group is providing an opportunity to astronomy enthusiasts (including school children) from across India. A team of Indian space enthusiasts recently discovered four new near-Earth asteroids during a search training programme overseen by Vigyan Prasar and NASA. A six-member team of watchdog citizens turned scientists, led by Rekha, a science teacher, used communicators and teachers to detect the rocks, setting an industry precedent. The training provided by SPACE to Indian students led to the discovery of two Asteroids, many Provisional Discoveries of Asteroids and Near-Earth Object Observations.
Space fascinates. The depths of the skies and glittering stars and far off planets enthuse the researchers. There is a thirst for understanding what lies at a distance beyond what you can physically measure, and the challenge is to find ways to quest the thirst. Let us celebrate “World Asteroid Day” and continue research and observations to unravel the mysteries of the universe.
*A Toonlog on the topic was posted in 2020: International Asteroid Day