While we were standing on planet Earth, it’s easy to forget that we were sitting on a rock hurtling through the Solar System on a path that might collide with other (smaller) space rocks, mainly because we don’t feel the motion.
If you ever feel the urge to feel completely at the mercy of random space rocks, we highly recommend heading over to NASA’s Eyes on Asteroids website and choosing their closest approach.
NASA and other observatories track the orbits of objects discovered in the Solar System, with a special eye for “near-Earth objects” (NEOs) 140 meters (460 feet) in size and larger that could wreak havoc if they hit Earth. By observing their orbits, astrophysicists are able to estimate the future orbits of objects and predict whether they will potentially enter our part of the Solar System.
These objects are rated on the Palmero scale.
“The scale compares the probability of a potential impact being detected to the average risk posed by objects of the same size or larger over the years up to the date of the potential impact,” explains the study by NASA’s Center for Near-Earth Objects. “This average risk from random impacts is known as the background risk. For convenience, the scale is logarithmic, so for example a Palermo scale value of -2 means that a detected potential impact event is only 1 percent more likely than the random background.” an event that occurred in the interim, a value of zero means that the single event is as threatening as the background hazard, and a value of +2 means an event that is 100 times more likely than the impact of a background object at least as large before the date of the potential impact in question .”
Objects are also given a friendlier “Torino” score of 0–10, with a score of 0 meaning the probability of an impact is zero or so and 10 meaning “a collision is certain, could cause a global climate catastrophe that could threaten the future of civilization as we know it , whether impacting land or ocean.” These are helpfully color-coded in green, yellow and red to clarify the situation for the public.
Over the years of observing space objects, astronomers have discovered objects that have moved away from the green zone. However, there are a couple that have made it to level 4; the highest level of the yellow zone.
“A close encounter that deserves the attention of astronomers,” explains the NASA level. “Current calculations give a 1 percent or better chance of a collision capable of regional devastation. New telescope observations will most likely lead to a reclassification to level 0. Attention from the public and public officials is warranted if the encounter is less than a decade away.” away.”
One of these objects was 99942 Apophis. After it was first discovered in 2004, observations placed it at level 2 on the Turin scale. However, further observations in December of that year moved it up to level 4 due to a 1.6 percent chance of the asteroid hitting us in 2029. Further observations ruled out a collision in 2029, as well as in 2036 and 2068, although there will still be close encounters.
There are currently no known objects with a Torino score greater than 0. However, there are objects that require further observation, with scores of -0.93 and -1.59 on the Palmero scale, which have not been assigned a Torino score because possible collisions are further along. than 100 years in the future.
(29075) 1950 DA, an object 1.3 kilometers (0.81 mi) in diameter, has a score of -0.93 due to its “potentially very close” approach to Earth on March 16, 2880. This is likely to change in the coming years as add more observations. made.
101955 Bennu (1999 RQ36) – more simply known as “Bennu” – currently sits at -1.59 on the Palmero scale. As far as we can tell, it will make several close approaches to the Moon and Earth. In September 2135, it is expected to fly by at a distance of 0.00143 astronomical units (AU) from Earth, where 1 AU is the distance between Earth and the Sun. That’s 213,925 kilometers (132,927 miles)which is quite close in cosmic terms.
As these asteroids orbit, more observations are made and trajectories are refined, meaning these scores can go up or down. The further out in time, the more likely it is that objects’ orbits can be perturbed by close encounters with other objects (such as Earth).
Until now, astronomers have been able to predict the orbits of known objects up to about 100 years into the future. The good news is that “no known asteroid larger than 140 meters has a significant chance of hitting Earth in the next 100 years,” says Dr Kelly Fast, manager of NASA’s NEO Observations program at NASA HQ in 2018.
In better news, a team led by Oscar Fuentes-Muñoz at the University of Colorado Boulder was able to go even further and predict the orbits of larger asteroids 1,000 years into the future.
“Assessing the impact risk over longer timescales is a challenge as orbital uncertainties grow. To overcome this limitation, we analyze the evolution of the minimum orbital intersection distance (MOID), which bounds the closest possible encounters between an asteroid and Earth,” the team explains in their article. “The development of MOID highlights NEOs that are near Earth for extended periods of time, and we propose a method to estimate the probability of deep Earth encounters during these periods.”
Using this method, the team was able to rule out that most NEOs will hit our planet within the next thousand years, and could estimate the probability that the rest will hit us like a bunch of dinosaurs. The likelihood of being hit before the year 3000 looks pretty low, according to the team, with the most likely object to hit us – 7482 (1994 PC1) – only having a 0.00151 percent chance of a close encounter that comes closer to Earth than the Moon’s orbit .