Planet-killing asteroids discovered in inner solar system
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Scientists studying objects in the inner solar system have discovered three nearby asteroids previously shrouded in glare from the Sun. Two of them are more than a kilometer, which earns them the label “planet killer“- and one is the largest potentially hazardous asteroid (PHA) discovered in at least the past eight years.
Astronomers studying asteroids in the inner solar system have the odds against them. Since these objects cluster near the Sun, they can only be observed at dusk when the glare is not too strong. Due to the position of asteroids in space between us and the Sun, they are low in the sky at this time, so astronomers should aim for the horizon. Not an ideal configuration: the sky is still relatively clear, the Earth’s atmosphere can have a notoriously distorting effect from this angle, and observation times are limited to around ten minutes.
“Only about 25 asteroids with orbits completely inside Earth’s orbit have been discovered so far due to the difficulty of observing near the Sun’s glare,” said Scott Sheppard, the astronomer at the Carnegie Institution for Science which conducted the research.
State-of-the-art technology such as the Chilean Blanco Telescope dark energy camera (DECam) provide the sensitivity and wide field to overcome these obstacles. Originally built for the Dark Energy Investigation conducted in the 2010s, the camera has now embarked on a new task: monitoring the inner solar system.
The discovery of these three asteroids is part of a larger DECam-focused study of objects in the orbits of Earth and Venus, as described in a recently published paper. paper.
Asteroid 2022 AP7 is certainly the most relevant to us, with a diameter of around 1.5 km and an orbit that crosses paths with Earth (but at a time when we are on the other side of the Sun, the less so far). For context, the asteroid deflected by NASA Asteroid double redirect test in September was just over a tenth the size, so we have some way to go if 2022 AP7 becomes more of a threat.
The other “planet killer” is not considered a PHA for Earth, but rather for Venus. 2021 PH27’s entire trajectory is locked into Earth’s orbit; in fact, it has the shortest period of any known asteroid around the Sun. However, this orbit is rather unstable, resulting in a 0.7% chance of collision with Venus over the next million years. It’s also possible that the asteroid could become active, meaning it ejects material into space, like a comet does, which could result in a nice meteor shower for any observer based on Venus.
Beyond the detection of objects that may be dangerous to us (or any other planet), a more precise study of objects in the inner solar system can facilitate studies of the evolution of asteroid distribution and the interactions of asteroids with the Sun.
“DECam can cover large areas of sky at depths impossible to reach with smaller telescopes, allowing us to reach further, cover more sky, and probe the inner solar system in ways never before possible. “, Sheppard said.