Astronomers spot ‘planet killer asteroid’: Is it a threat to Earth?

Subject :Science and Technology

Context-

A team of astronomers has discovered three massive near-Earth asteroids hiding in the glare of the Sun. Of these, one called 2022 AP7 is believed to be the largest planet killer-sized asteroid to be spotted in nearly a decade and is “potentially hazardous” to Earth.

What do we know about these asteroids?

Scientists have so far discovered only around 25 asteroids with their orbits within Earth’s orbit.
The three asteroids are from a group that is found within the orbits of Earth and Venus.
The three discovered asteroids are- 2021 LJ4, 2021 PH27, and 2022 AP7 asteroids.
Two of the three discovered asteroids — 2021 LJ4 and 2021 PH27 — have orbits that are safely constrained inside the limits of Earth’s orbit.
At less than a kilometre in diameter, 2021 LJ4 is the smallest in size.
The asteroid, 2021 PH27, is the closest known asteroid to the Sun.
Due to this, its surface gets hot enough to melt lead.
The 1.5-kilometre-wide 2022 AP7 asteroid has an orbit that may someday put it on a collision course with our planet.
An asteroid like 2022 AP7 could have “a devastating impact on life” and could potentially lead to a “mass extinction event”.

Why are they tough to spot?

They are tough to spot as the brightness of the Sun shields them from telescope observations.
Another major issue is that, since the asteroids are close to the horizon, they are blurred and distorted by the Earth’s atmosphere.
Asteroids that are further away from the Sun are easier to detect.

How did they spot the asteroids?

Since they were concealed by the Sun’s glare, the astronomers conducted their observation during twilight hours — a brief but favourable 10-minute window every night.
They used a Dark Energy Camera at the Cerro Tololo Inter-American Observatory in Chile.
With the high-tech camera, a programme of the US National Science Foundation’s (NSF’s) NOIRLAB, they were able to capture large swathes of the sky with immense sensitivity.
The camera was originally built to carry out a Dark Energy Survey, conducted by the US Department of Energy and the NSF between 2013 and 2019.

Is there an immediate threat to Earth?

At present, the asteroid only crosses the Earth’s orbit while it is on the opposite side of the Sun i.e. when the Sun comes between the Earth and the asteroid.
This will continue for several centuries as it takes the asteroid about five years to orbit the sun.
Over time, its orbital movement will slowly evolve to be more in sync with Earth’s.

Asteroids

Asteroids are small, airless rocky objects revolving around the sun that are too small to be called planets. They are also known as planetoids or minor planets.
In total, the mass of all the asteroids is less than that of Earth’s moon. But despite their size, asteroids can be dangerous. Many have hit Earth in the past, and more will crash into our planet in the future.

Asteroids are divided into three classes:

First Group:
- Those found in the main asteroid belt between Mars and Jupiter, which is estimated to contain somewhere between 1-1.9 million asteroids.
Second Group:
- It is that of trojans, which are asteroids that share an orbit with a larger planet.
- NASA reports the presence of Jupiter, Neptune and Mars trojans.
- In 2011, they reported an Earth trojan as well.
Third Group:
- It is Near-Earth Asteroids (NEA), which have orbits that pass close to the Earth.
- Those that cross the Earth’s orbit are called Earth-crossers.
- More than 10,000 such asteroids are known, out of which over 1,400 are classified as Potentially Hazardous Asteroids (PHAs).
- NASA’s Center for Near-Earth Object Study (CNEOS) determines the times and distances of these objects, when their approach to the Earth is close, through the Asteroid Watch Widget.

Potentially Hazardous Asteroids (PHAs)

It means that an asteroid has the potential to make threatening close approaches to the Earth.
Specifically, all asteroids with a Minimum Orbit Intersection Distance (MOID) of 0.05 AU (which is about 7,480,000 Km) or less and an Absolute Magnitude (H) of 22.0 (about 150 mt in diameter) or less are considered PHAs.

What Are The Differences Between An Asteroid, Comet, Meteoroid, Meteor and Meteorite?

Asteroid: A relatively small, inactive, rocky body orbiting the Sun.
Comet: Comets are cosmic snowballs of frozen gases, rock, and dust that orbit the Sun.
- Its ice can vaporize in sunlight forming an atmosphere (coma) of dust and gas and, sometimes, a tail of dust and/or gas.
Meteoroid: A small particle from a comet or asteroid orbiting the Sun.
Meteor: The light phenomena which result when a meteoroid enters the Earth’s atmosphere and vaporizes; a shooting star.
Meteorite: A meteoroid that survives its passage through the Earth’s atmosphere and lands upon the Earth’s surface.