This web page is created within BALTICS project funded from the European Union’s Horizon2020 Research and Innovation Programme under grant agreement No.692257.
The near-Earth objects
The near-Earth objects are asteroids and comets, whose orbits are closing in on the Earth’s orbit. The perihelium of these objects is 1,3 astronomical units away from the Sun. An object is considered a potential threat if it is larger than 140 meters in diameter and is distanced less than 0,05 astronomical units, in other words – 7,5 million kilometers, away from Earth. The majority of objects close to Earth are asteroids.
Asteroids, that are closing in on Earth, are divided into four main groups – Atiras, Atens, Apollos and Amors type of asteroids.
The Atiras type of asteroids, that were named after the Asteroid 163693 Atira, travels in the inner part of Earth’s orbit. It means, that the asteroid’s Apsis is closer to the Sun than Earth’s perihelium, which is 0,983 astronomical units. The asteroids of this group do not pose threat to the Earth, but, taking into account that orbits can change due to the gravitational forces of Venus, Mercury or Sun, they still need to be monitored and researched. As of now, 18 of such objects are known.
The Atens type asteroids cross the Earth’s orbit. Their bigger axis of their orbits are smaller than 1 astronomical unit and the Apsis is located further than Earth’s perihelium. The “representative” of asteroids in whose name the group was named is the asteroid 2062 Atens, which was discovered in 1976. As of now, more than 1300 Atens are known, of which the majority are dangerous objects.
The Apollos type asteroids also cross the Earth’s orbit, but the large axis of their orbits are larger than 1 astronomical unit. The perihelium of the Apollos is located closer to the Sun than Earth’s Apsis (1,017 AU). A typical “representative” is the asteroid 1862 Apollo, which was discovered in 1930. The asteroid that exploded over Chelyabinsk (Russia) in February 15th, 2013 also was a part of this group. As of now, more than 8000 Apollos type asteroids are known, of which 1500 potential threats to Earth.
In turn, Amors group of asteroids orbit without crossing Earth’s orbit. Their perihelia are located further away than Earth’s Apsis (1,017 AV), but closer than 1,3 AU. Some of Amors’ orbits cross the Mars’s orbit. It is possible that once both of Mars’s moons – the Phobos and Deimos – were Amors that were caught by the Mars’s gravity. The Amors got their name from the asteroid 1221 Amor, that was discovered in 1932. One of the most famous “representatives” of this group is the asteroid 433 Eros. There are more than 6000 known asteroids in the Amors group. The majority of Amors are not a threat to Earth, but approximately 1/5 of these asteroids are closing in on Earth by 0,05 astronomical units and are considered as potential threats.
The systematic search, accounting and research is being carried out since March 11th, 1998, when the Minor Planet Center, that is located in the University of Cambridge, published information which stated that the asteroid 1997 XF11 could collide with Earth in 2028. Further analysis of the asteroid’s orbit revealed that a collision would not be possible nor in the aforementioned year, nor in the next 200 years. Still, this event proved that accounting, research and provision of correct information to the media of such objects is necessary.
The threat level of near-Earth objects is described using the Torino scale. Objects are classified, taking into account their size, possibility of collision and kinetic energy. The Torino scale is applied to to the objects that could collide with Earth over the next 100 years.
In the summer of 1998, NASA began a program for monitoring near-Earth objects, which was renamed as the Center for Near-Earth Object Studies (CNEOS). Nowadays these objects are searched for by automated observatories, where the obtained data is analyzed by a special software and astronomers. Within the framework of this program 90% of the 18500 known near-Earth objects have been discovered. On average 40 new objects are added to this list every week.
The near-Earth objects are not only a threat to Earth, but also a usable resource for the future. These asteroids contain water and valuable raw materials that humans could use to learn about and colonize the more distant regions of the Solar System successfully.
NO HAZARD
0
Collision is not possible. Small objects that are completely disintegrated in the atmosphere, as well as small meteorites that do no kind of damage are put in this category.
NORMAL (green)
1
A category for the basic newly discovered objects, if calculations suggest that a collision is not possible. Further observations of the object reduce its threat level to the 0 category.
MERITING ATTENTION (yellow)
2
A newly discovered object, the initial orbit of which indicates that it will pass close to Earth. Most likely, further observations will put it into the 0 category.
3
Object will approach Earth. Initial calculations point at a 1% or larger possibility of collision, causing a local catastrophe. Further observations will, most likely, reduce threat level to the 0 category. The society and officials will need to be informed if the event is expected to take place in less than 10 years.
4
Object will approach Earth. Initial calculations point to a 1% or larger possibility of collision, causing a regional catastrophe. Further observations will, most likely, reduce threat level to the 0 category. The society and officials will need to be informed if the event is expected to take place in less than 10 years.
THREATENING (orange)
5
The approach of the object creates serious, but currently unknown threats of collision with a potential regional catastrophe. Increased attention is required in order to determine the possibility of the collision. If the collision is expected in less than 10 years, national representatives are to be informed and an action plan is to be created.
6
The approach of the object creates serious, but currently unknown threats of collision with a potential regional catastrophe. Increased attention is required in order to determine the possibility of the collision. If the collision is expected in less than 30 years, national representatives are to be informed and an action plan is to be created.
7
Approach of a large object in over the next 100 years that creates substantial, but currently unknown threats of a collision with a possible global catastrophe. In this case an international action plan is to be created.
CERTAIN COLLISION (red)
8
Collision with an object that will cause a local catastrophe, if it hits dry land, or tsunami, if it hits somewhere near the coastline. Statistics suggest that these types of collisions can happen once in 50 to 10000 years.
9
Collision with an object that will cause a regional catastrophe, if it hits dry land, or a large tsunami, if it hits somewhere near the coastline. Statistics suggest that these types of collisions can happen once in 10000 to 100000 years.
10
Collision with an object that will cause a global catastrophe and following change, resulting in a possibility of the extinction of mankind. Such collisions, statistically, can happen once every 100000 years or less often.
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