Keeping an eye on space for any potentially hazardous space rocks is a paramount mission for astronomers, which is why systems have been put in place for automatic detection of any suspicious objects.
A NASA-operated telescope located in Chile detected a suspicious object last year on Christmas Day, which resulted in the space agency's Asteroid Terrestrial Last Alert System (ATLAS) being triggered and manual follow-up observations being conducted by human researchers. Researchers then discovered the object was an asteroid, which has now been named 2024 YR4. The team found the asteroid's orbit around the Sun is elongated, and it's currently traveling directly away from Earth, almost in a straight line.
However, its almost straight-line trajectory has made it difficult for researchers to get accurate measurements of its speed, size, and characteristics. Preliminary estimations put 2024 YR4 at anywhere between 130 and 300 feet in diameter, it's speed at 38,700 mph, and a composition of silicate minerals, which are rock-forming minerals. Researchers will be able to see the asteroid until April this year, as it will disappear around the Sun and won't be visible again until 2028. That's when things could begin to get hairy, though.

Based on the information already gathered, 2024 YR4 has already been moved to the top of the Torino Impact Hazard Scale, which is a scale that measures from 1 - 10 and categorizes potential Earth impact events. Currently, 2024 YR4 is ranked at level 3, which has put it at the top of the list of most dangerous near-Earth objects (NEO) astronomers have on the books.
Estimations on the likelihood of impact and when are as follows: In 2032, there's a 1-in-100 chance for impact or a 1.3% chance. If the impact does occur, it will likely cause a tsunami if it hits an ocean, and if it impacts land, the blast radius is estimated to be around 31 miles.
2024 YR4 isn't the only asteroid on the Torino scale, as initial estimates pegged asteroid 99942 Apophis as a category 4. 99942 Apophis makes 2024 YR4 look like a weakling as Apophis measures a mile wide, and initial estimations put its impact somewhere in the Pacific between 2029 and 2036. Luckily, follow-up observations quelled fears of an impactor as it was discovered Earth is safe from 99942 Apophis for at least another century.
For those wondering, if 2024 YR4 did impact Earth it would release the same amount of energy as a eight-mega-ton TNT bomb, which is an explosion approximately 500 times larger than the nuclear bomb dropped on Hiroshima in World War 2.