What are Near-Earth Objects? 5 asteroids set to zip past the planet on January 6 and two of them are massive
Five asteroids are set to make a close approach to Earth on January 6, according to the Center for Near-Earth Object Studies (CNEOS). Two of them that are set to fly past Earth — 332446 (2008 AF4 and (2016 CO247) — are massive. The bigger of the two, 2008 AF4, is estimated to be 310 meters to 680 meters in diameter. It is speeding through space at the astronomical speed of 10.98 kilometers per second. The second one has an estimated diameter of 210 meters to 470 meters.
What do we know about such objects?
Near-Earth Objects (NEOs) are asteroids or comets that orbit the Sun. As they orbit the Sun, NEOs occasionally approach close to Earth, which may pose a danger of collision. “A near-Earth object (NEO) is an asteroid or comet whose orbit brings it into or through a zone between approximately 91 million and 121 million miles (195 million kilometers) from the Sun, meaning that it can pass within about 30 million miles (50 million kilometers) of Earth’s orbit,” describes NASA.
According to experts, they have been “nudged by the gravitational attraction of nearby planets” into orbits that allow them to enter the Earth’s neighborhood. “Composed mostly of water ice with embedded dust particles, comets originally formed in the cold outer planetary system while most of the rocky asteroids formed in the warmer inner Solar System between the orbits of Mars and Jupiter. The scientific interest in comets and asteroids is due largely to their status as the relatively unchanged remnant debris from the Solar System formation process some 4.6 billion years ago,” explains the NASA blog.
The giant outer planets (Jupiter, Saturn, Uranus, and Neptune) formed from an "agglomeration" of billions of comets and the leftover bits from this formation process are the comets seen today. Similarly, today’s asteroids are the bits and pieces leftover from the initial agglomeration of the inner planets that include Mercury, Venus, Earth and Mars.
“As the primitive, leftover building blocks of the Solar System formation process, comets and asteroids offer clues to the chemical mixture from which the planets formed. If we wish to know the composition of the primordial mixture from which the planets formed, then we must determine the chemical constituents of the leftover debris from this formation process, the comets and asteroids,” explain researchers.
While the vast majority of NEOs that enter Earth’s atmosphere disintegrate before reaching the surface, those NEOs that are larger than around 98 to 164 feet (30 to 50 meters) in size may cause widespread damage in and around their impact sites. A Potentially Hazardous Object (PHO) is a Near-Earth Object whose orbit brings it within 4.7 million miles (7.5 million km) of Earth’s orbit and is greater than 500 feet (140 meters) in size.
“NEOs could potentially hit our planet and, depending on their size, produce considerable damage. While the chance of a large object hitting Earth is very small, it would produce a great deal of destruction. NEOs thus merit active detection and tracking efforts,” states ESA.
In the summer of 1998, NASA established the Near-Earth Object Observations Program and JPL became the home for the agency’s research data and analysis on NEOs, the “Near-Earth Object Program Office”.
Its original objective was to locate at least 90% of all NEOs that are larger than about 1 kilometer (roughly two-thirds of a mile) within 10 years. In 2016, the office was renamed the Center for Near-Earth Object Studies (CNEOS) in conjunction with the establishment of the Planetary Defense Coordination Office (PDCO) at NASA headquarters in Washington. There are now over 18,000 known NEOs and the discovery rate averages about 40 per week.
In 2005, Congress established a new, much more ambitious goal for the NEO observations program — to discover 90% of the NEOs down to the much smaller size of 450 feet (140 meters). According to scientists, these smaller asteroids may not present a threat of global catastrophe if they impact Earth, but they could still cause massive regional devastation and loss of life, especially if they occur near a metropolitan area.
“While no known asteroid larger than 140 meters in size has a significant chance to hit Earth for the next 100 years, less than half of the estimated 25,000 NEOs that are 140 meters and larger in size have been found to date,” notes NASA.