A Skyscraper-Sized Asteroid Here To Make Your Halloween Even Spookier

Asteroid PHA 2022 RM4 will make its closest approach to Earth tomorrow or the day after, depending on your time zone. As asteroid encounters, it’s not particularly close, passing us at 2.3 million kilometers (1.43 million miles), or six times the distance to the Moon. There are, however, aspects of this event that make it stand out besides its timing.

The first is that PHA 2022 RM4’s orbit crosses ours, so one day it could actually touch Earth, hence the designation PHA (Potentially Hazardous Asteroid). Plus, he’s big enough to do some serious damage if he hits Earth, though he’s definitely not a dinosaur killer. At somewhere between 330 and 740 meters (1,080 to 2,430 feet) in diameter, it is not an object to be measured in the size of African wildlife. Once we get a more accurate estimate of its height, everyone can check to see if it’s longer than the tallest building in their hometown. Right now, only a handful of cities have buildings so tall they can be sure to top it.

However, perhaps the most alarming thing about PHA 2022 RM4 lies in the middle part of its name. We only discovered this object in September of this year. All hopes that we had discovered any short-period asteroids with Earth-crossing orbits greater than or so 300 meters (980 feet) have now been dashed. Instead, we have to accept that the possibility of a large space rock bumping into our planet unexpectedly overnight remains a distinct possibility.

Projects like DART to deflect objects capable of triggering huge tsunamis or darkening the sky for months are all great if we have plenty of warning, but little use with less than two months notice.

With a 1,400-day (3.8-year) orbit, PHA 2022 RM4 spends most of its time farther from the Sun than Mars, but its closest approach is just inside Earth’s orbit. It is unusual to see how far from the planetary plane its orbit is.

No closer approach to Earth has been calculated, so PAH 2022 RM4 is not a threat for the foreseeable future. However, with an orbit like this, it’s likely that it will eventually become a problem that will need to be dealt with.

Gianluca Masi of the Virtual Telescope Project managed to capture the image below of PHA 2022 RM4 as a small dot two days before its closest approach. The telescope tracked the asteroid as it moved across the sky, making background stars appear as lines. At the time, the object was almost exactly twice its closest distance from Earth.

PHA 2022 RM4 as imaged by the Virtual Telescope Project two days before its closest approach. Image credit: Gianluca Masi, Ceccano (FR), Italy – MPC: 470 – The virtual telescope project

The Virtual Telescope Project will be back in action tracking the asteroid on its closest approach on November 1, starting at 17:00 UTC.

Under dark skies, experienced observers may be able to detect it on their own using medium-sized telescopes, although it is too far south for many Europeans and North Americans.

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