Twilight observations with the US Department of Energy’s Dark Energy Camera at the Cerro Tololo Inter-American Observatory in Chile, a program of NSF’s NOIRLab, allowed astronomers to spot three near-Earth asteroids (NEA) hiding in the glow of sun. These NEAs are part of an elusive population lurking within the orbits of Earth and Venus. One of the asteroids is the largest object potentially dangerous to Earth discovered in the last eight years. An international team using the Dark Energy Camera (DECam) mounted on the Víctor M. Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory in Chile, a program of NSF’s NOIRLab, has discovered three new near-Earth asteroids (NEA) lurking in solar system, the region inside the orbits of Earth and Venus. This is a notoriously challenging region for observations because asteroid hunters must contend with the sun’s glare. However, taking advantage of the brief but favorable observing conditions during twilight, astronomers found an elusive trio of NEAs. One is a 1.5-kilometer-wide asteroid called 2022 AP7, which has an orbit that may someday place it in Earth’s path. The other asteroids, called 2021 LJ4 and 2021 PH27, have orbits that stay safely completely inside Earth’s orbit. Also of particular interest to astronomers and astrophysicists, 2021 PH27 is the closest known asteroid to the sun. As such, it has the largest effects of general relativity of any object in our solar system, and during its orbit its surface heats up enough to melt lead. “Our twilight survey scans the region within the orbits of Earth and Venus for asteroids,” said Scott S. Sheppard, an astronomer at the Carnegie Institution for Science’s Earth and Planets Laboratory and lead author of the paper describing this work. “So far we have found two large near-Earth asteroids that are about 1 kilometer in diameter, a size we call planet killers.” “There are probably only a few NEAs of similar sizes to be found, and these undiscovered large asteroids probably have orbits that keep them inside the orbits of Earth and Venus most of the time,” Sheppard said. “Only about 25 asteroids with orbits completely inside the Earth’s orbit have been discovered to date because of the difficulty of observing near the sun’s glare.” Finding asteroids in the inner solar system is a daunting observational challenge. Astronomers have only two brief 10-minute windows each night to survey this region, and must contend with a bright background sky resulting from the sun’s glare. Furthermore, such observations are very close to the horizon, meaning that astronomers must observe through a thick layer of Earth’s atmosphere, which can cloud and distort their observations. The discovery of these three new asteroids despite these challenges was possible thanks to DECam’s unique observing capabilities. The state-of-the-art instrument is one of the highest-performance wide-field CCD imagers in the world, enabling astronomers to image large areas of the sky with high sensitivity. Astronomers refer to observations as “deep” if they pick up faint objects. When hunting for asteroids within Earth orbit, the ability to take both deep and wide field observations is essential. “Large areas of sky are required because inner asteroids are rare, and deep images are required because asteroids are faint, and you’re fighting the bright twilight sky near the sun as well as the distorting effect of Earth’s atmosphere,” Sheppard said. “DeCam can cover large areas of the sky at depths unattainable with smaller telescopes, allowing us to go deeper, cover more sky, and probe the inner solar system in ways never before done.” In addition to detecting asteroids that could potentially pose a threat to Earth, this research is an important step toward understanding the distribution of small bodies in our solar system. Asteroids that are farther from the sun than Earth are easier to spot. Because of this, these more distant asteroids tend to dominate current theoretical models of the asteroid population. Detecting these objects also allows astronomers to understand how asteroids are transported throughout the inner solar system and how gravitational interactions and the sun’s heat can contribute to their fragmentation. “Our DECam survey is one of the largest and most sensitive searches ever conducted for objects within Earth’s orbit and near the orbit of Venus,” said Sheppard. “This is a unique opportunity to understand what kinds of objects are hidden in the inner solar system.” “After ten years of remarkable service, DECam continues to produce important scientific discoveries while contributing to planetary defense, a critical service that benefits all of humanity,” said Chris Davis, NSF Program Director for NOIRLab. The findings are published in The Astronomical Journal. More information: Scott S. Sheppard et al, A Deep and Wide Twilight Survey for Asteroids Interior to Earth and Venus, The Astronomical Journal (2022). DOI: 10.3847/1538-3881/ac8cff Provided by the Association of Universities for Research in Astronomy (AURA) Report: Astronomers Spot Largest Potentially Hazardous Asteroid Spotted in Eight Years (2022 October 31) Retrieved October 31, 2022 by This document is subject to copyright. Except for any fair dealing for purposes of private study or research, no part may be reproduced without written permission. Content is provided for informational purposes only.
