(Astronomy@Science_Newworld).

The unexpected low number of asteroids in near-Earth space is due to the fact that the sun constantly "grinds" asteroids approaching it, turning them into a set of small particles that subsequently form bright meteor showers in the earth's night sky, according to an article published in the journal Nature.

"The discovery that asteroids break up when they get too close to the sun was so amazing to us that we spent a very long time checking and rechecking our calculations," said Robert Jedicke from the University of Hawaii at Honolulu (USA). .

Jedicke and colleagues came to this conclusion by comparing maps of asteroids compiled from data from a catalog of near-Earth objects collected as part of the Catalina Sky Survey project with those predicted by models of the solar system.

As this comparison showed, the number of near-Earth and near-Sun asteroids known to us is extremely small - in fact, according to computer models of the inner solar system, there should be about 10 times more.

Trying to explain this mysterious disappearance of asteroids, scientists tracked the movement of several near-Earth celestial bodies orbits in this model, trying to uncover orbital mechanisms that would "catapult" extra minor planets from the vicinity of the orbits of Mercury, earth and Venus, or in some other way clear this part of the solar system from "heavenly stones".

These calculations led to unexpected results - it turned out that the main "Cleaner" of the inner regions of the solar system is the sun itself, periodically destroying asteroids that fly closer to it at a distance closer than 10-15 luminary radii.

Prior to this, scientists believed that the sun was not capable of heating asteroids approaching it to temperatures high enough to cause them to evaporate or otherwise form destruction. As Yedike and his colleagues found out, the destruction of asteroids proceeds in a different way, the essence of which has yet to be clarified.

According to the astronomers themselves, this process can occur as follows: when an asteroid approaches the sun, its surface can begin to crack and break into small segments, dust particles from which are “Knocked out” and carried away by the solar wind and photons of light.

Another option for the disintegration of these asteroids is that the evaporation of gases inside them and the pressure of light can cause them to spin up to very high speeds, as a result of which the celestial body simply disintegrates into small fragments under the action of centrifugal forces. This is supported by the existence of various meteor showers around the sun, which periodically illuminate the night sky of the earth on certain days and weeks of the year.

On the other hand, as data from the Wise telescope show, the decay process of asteroids with different surface brightness will differ, both in terms of the mechanism and the distance at which it occurs - for example, darker celestial bodies should fall apart earlier than lighter ones, which speaks in favor of the first scenario. In any case, both variants of decay show that the life of a near-Earth asteroid is short-lived - on average, it should live no more than 250 years.

Scientists believe that we will be able to see such a decay very soon - the asteroid 2006 Hy51 today flies very close to the sun, approaching at a distance of 17 luminary radii. Another victim of the sun may be a large five-kilometer near-Earth asteroid phaeton, approaching only 20 million kilometers to the sun, on the surface of which planetary scientists recently found traces of destruction. Jedicke and his colleagues plan to conduct observations of these objects in the near future, checking their calculations.

Scales

There are several scales for assessing the risk of POO.

Turin scale

• Asteroids (0 points) - consequences of the collision: they have no chance to meet the Earth.
• Asteroids (10 points) - the consequences of the collision: the number of species inhabiting our planet should be reduced by orders of magnitude.

Judging by geological data (several hundred impact craters have been explored), collisions with large celestial bodies have happened more than once in the history of our planet. The fall of one large meteorite, some scientists explain the mass extinction of living organisms (about 250 million years ago). Another meteorite, according to the hypothesis of U. Alvarez, led to the extinction of dinosaurs.

Sources

Closest to Earth was a small asteroid 2004 FU 162 (diameter about 6 meters) - about 6500 km from Earth (March 2004).

Discovery history

Historically, Eros (, Amur group) was the first of the asteroids with an orbit close to the Earth. The largest asteroid in the Amur group is Ganymede (which should not be confused with the satellite of the same name of Jupiter), its diameter is approximately 32 km (Eros has about 17 km).

• Asteroid 2008 TC 3 - discovered 20 hours before it burned up in the atmosphere over Sudan on October 7, 2008.
• Asteroid 2009 DD 45 - discovered on February 28, 2009 (three days before it approached the Earth at a minimum distance) by astronomer Robert McNaught, who studied photographs taken using the Schmidt telescope from the Siding Springs Observatory in Australia. The asteroid made its closest approach to the Earth on March 2, 2009 (16:44 Moscow time, according to representatives of the Planetary Society - 13:44 GMT). It could be seen with the naked eye in the skies over the South Pacific. Dimensions - 20-50 (27-40) meters. The distance to the Earth is 66 (72) thousand km. The spread of numbers is due to the fact that the diameter of asteroids is calculated on the basis of their albedo - reflectivity. Since astronomers don't know exactly how much light the surface of 2009 DD45 reflects, they start from averages. Movement speed - (at the moment of being at a minimum distance from the Earth - 20 km / s. In a collision, the explosion energy would be equal to 1 megaton (one high-power nuclear bomb) in TNT equivalent. For comparison: by the impact of the Tunguska meteorite (exploded in the atmosphere over Siberia 30 June 1908) 80 million trees were felled over an area of ​​about 2,000 square kilometers, which corresponds to an explosion of 3-4 megatons of TNT.

Problematic detection

Financial

Scientists note that even small objects pose a threat to the Earth, since their explosions near the planet as a result of heating can lead to significant destruction. However, NASA currently tracks mainly the largest space objects, which are more than a kilometer in diameter (as of 2007, 769 known asteroids and comets, whose diameter does not exceed 140 meters, are not observed so closely).

Technical

Current state

In total, about 6,100 objects have been registered that pass at a distance of up to 1.3 astronomical units from the Earth.

As of April 2009, not a single PEO was observed in the solar system (a list of a little more than a thousand positions, where 90% are asteroids, 10% are comets, the distance from them to the Earth is less than 0.05 astronomical units), which could overcome the milestone in zero points.

The danger that asteroids pose to the planet is not regarded as serious. According to modern estimates, collisions with such bodies (according to the most pessimistic forecasts) are unlikely to occur more often than once every hundred thousand years. If a celestial body large enough to cause serious damage is directed towards the Earth, astronomers will be able to detect it.

see also

Notes

Links

• Zheleznov N. B. Asteroid-comet hazard: the current state of the problem.
• Finkelstein A., corresponding member RAN. Asteroids threaten the Earth. Science and Life, No. 10, 2007, pp. 70-73.
• Earth Impact Crater Database.
• Near-Earth Asteroid Database.

Wikimedia Foundation. 2010 .

Also from the NEOCP page, confirmatory observations of the near-Earth asteroid 2012 PW were made, the observations were published in MPEC 2012-P19. And astrometry was obtained for several asteroids discovered in July at the ISON-Kislovodsk observatory as part of a new asteroid survey.

06/18/12 * On the night of June 16-17, an attempt was made to observe the occultation of the star 12.7m by transneptune (5145) Pholus , the band uncertainty was rather large, and the occultation could not be registered. were also carried out successful observations two new near-Earth asteroids 2012 LE11 and 2012 LF11, the results of observations are published in MPEC 2012-M06 and MPEC 2012-M07 .

06/13/12 * Last night observed the recently discovered comets C/2012 K5 (LINEAR) and C/2012 L3 (LINEAR) .

05/27/12 * This night I specially got out to the observatory to observe the near-Earth asteroid 2012KP24. An asteroid with a diameter of 20m should approach our planet on May 28 at a distance of 50,000 km, while having a magnitude of about 12m and moving almost a degree across the sky in an hour. Astrometry and photometry were also obtained for the new comet C/2012 K1 (PANSTARRS), which in 2014 may be available for observations with the naked eye.

05/11/12 * Short bright nights begin. Only 4 comets were observed last night.

04/29/12 * On April 26 and 27, CCD observations were obtained for another 6 comets, comet C/2011 UF305 (LINEAR) was also observed visually. In addition, a confirmatory observation was made for the supernova 2012by discovered on April 25 in the interacting galaxy UGC 8335 CBET 3096. Complicated astrometry was performed for the near-Earth asteroid 2012HM at the time of approach to the Earth up to 1.4LD, while observing angular velocity asteroid was 105"/min, brightness 15.5m, astrometry had to be done along a strongly elongated track.

04/25/12 * Only observations of comets were made that night. Astrometry and photometry were obtained for 7 comets, comet C/2009 P1 (Garradd) was observed only visually.

04/14/12 * We successfully tested the new focuser, traditionally made by ourselves.

04/13/12 * Observational material received on several comets last night. In particular, it was possible to visually observe comets C/2009 P1 (Garradd) and C/2011 F1 (LINEAR), comet Garada begins to gradually weaken. Observed comet 49P/Arend-Rigaux , this is my second observed return of this comet! In addition, confirmatory astrometry was obtained for 2 new near-Earth asteroids discovered by the automatic Catalina survey: 2012 GC2 and 2012 GD2 . Observations have been published in MPEC 2012-G37 and MPEC 2012-G38.

02/15/12 * Observations on several more comets were received last night, as a result, 11 comets have already been observed in this lunation. It was possible to obtain visual data on the comet 78P/Gehrels , it still maintains a brightness of 11.8m. An attempt was also made to find the comet 238P/Read, unsuccessfully, the comet is fainter than 20.5m. The first two search sites were received this year, but unfortunately, at 2 am the sky was hazy.

02/13/12 * 2 good nights were spent at the observatory on February 10 and 12, although the Moon still strongly interfered. Observations of comets were mainly carried out, observational material was obtained on 8 comets. A confirming observation of the new comet C/2012 C2 (Bruenjes) was also made, the comet is available for visual observation and has a magnitude of 11.5m. The results of the observations were published in MPEC 2012-C44 and CBET 3019.

12/28/11 * Perhaps December 26 was our last good night in the outgoing year. Several comets have been observed, one near-Earth asteroid has been observed from the NEO confirmation page, the observations have been published in MPEC 2011-Y40.

11/21/11 * Last night, as usual, observations of several comets were made, several search sites were also received, the data is still being processed. In general, the night was ideal in all respects, an example of this is the image of the M1 nebula in Taurus, the siing on individual frames was a record for the entire history of CCD observations at the observatory, the values ​​reached 1.4".

11/01/11 * On October 21, 25, 27 and 30, observations of comets were made at the observatory, as well as confirming observations of outbursts of possible supernovae in the galaxies PGC 2692384 and UGC 12410 were made, the results of the observations were published in CBET 2891 and CBET 2887. Several search sites for asteroids and supernovae have been obtained, but to no avail, except for a few discovered asteroids that have not been observed for 2 or more years. In general, the last ten days of October pleased with the weather, there were very good nights, the seaing at times was 1.7-2", and the faintest of the observed asteroids 2008 FE1 had a magnitude of 21.2V!

10/19/11 * Last night before moonrise was a couple of hours of time. Several comets have been observed, as well as a confirmatory observation of a possible supernova explosion in the galaxy NGC7485, the results of the observations were published in CBET 2866. From the NEO confirmation page, one bright asteroid was observed, but in the end it fell slightly short of the near-Earth asteroid in terms of orbital elements.

10/03/11 * The coming autumn does not indulge in the weather, yesterday we managed to catch a gap for a few hours. Visually observed comets C/2009 P1 (Garradd) and 78P/Gehrels, also observed comets 213P/Van Ness and 131P/Mueller on the CCD. Several search sites were received, but this time to no avail.

09/06/11 * On September 3 and 5, visual and CCD observations of comets were carried out at the observatory. Information about the discovery of 2 new asteroids has been confirmed, which received preliminary designations 2011 QN51 and 2011 QM51. Both are classical objects of the main belt.

09/01/11 * Observations of several comets were received last night. I spent a couple of hours searching for new objects, 2 new asteroids were previously found.

08/27/11 * Over the two nights of August 24 and 26, observational material was obtained from several comets. Fragmentation of comet 213P/Van Ness is preserved even managed to make astrometry of the second fragment. Visual estimates of comets C/2009 P1 (Garradd), 213P/Van Ness, and 78P/Gehrels were also obtained. A supernova has been observed in the bright galaxy M101.

08/06/11 * Two wonderful nights were spent at the observatory, sometimes with a very good atmosphere. On the night of August 5-6, flashes of the northern lights could be observed in the northern sector of the sky, which sometimes became brighter Milky Way, while the colors were even perfectly distinguishable. Unfortunately, I didn't have my camera with me. For me, this is not the first observation of this phenomenon in our latitudes. Observational material was also received on several comets, including several visual estimates and several comets were observed on the CCD. Worth noting is the fragmentation of Comet 213P/Van Ness, and the observation of Comet 78P/Gehrels - I'm already seeing this comet on my 3rd perihelion return!

08/02/11 * The last two so far short nights were partly spent on technical adjustments of the telescope for the upcoming observational season. Nevertheless, I visually observed the relatively bright comet C/2009 P1 (Garradd), the comet now has a magnitude of 7.6m, and CCD images of it and several other comets were also obtained.

The threat to the Earth can be carried by objects approaching it at a distance of at least 8 million kilometers and large enough not to collapse when entering the planet's atmosphere. They are a danger to our planet.

Until recently, the asteroid Apophis, discovered in 2004, was called the object with the highest probability of a collision with the Earth. Such a collision was considered possible in 2036. However, after Apophis passed by our planet in January 2013 at a distance of about 14 million km. NASA experts have reduced the likelihood of a collision to a minimum. The chances, according to Don Yeomans, head of the near-Earth object laboratory, are less than one in a million.
Nevertheless, experts have calculated the approximate consequences of the fall of Apophis, whose diameter is about 300 meters and weighs about 27 million tons. Thus, the energy released during the collision of the body with the Earth's surface will be 1717 megatons. The strength of an earthquake within a radius of 10 kilometers from the place of impact can reach 6.5 on the Richter scale, and the wind speed will be at least 790 m/s. In this case, even fortified objects will be destroyed.

Asteroid 2007 TU24 was discovered on October 11, 2007, and already on January 29, 2008, it flew near our planet at a distance of about 550 thousand km. Due to its extraordinary brightness - the 12th magnitude - it could be seen even in medium-power telescopes. Such a close passage of a large celestial body from the Earth - a rare thing. The next time an asteroid of the same size will approach our planet will be in 2027.
TU24 is a massive celestial body comparable to the size of the University building on Sparrow Hills. According to astronomers, the asteroid is potentially dangerous because it crosses the Earth's orbit approximately once every three years. But, at least until 2170, according to experts, it does not threaten the Earth.

The space object 2012 DA14 or Duende belongs to the near-Earth asteroids. Its dimensions are relatively modest - a diameter of about 30 meters, a weight of about 40,000 tons. According to scientists, it looks like a giant potato. Immediately after the discovery on February 23, 2012, it was found that science was dealing with an unusual celestial body. The fact is that the orbit of the asteroid is in 1:1 resonance with the Earth. This means that the period of its revolution around the Sun approximately corresponds to the Earth's year.
For a long time, Duende may be near the Earth, but astronomers are not yet ready to predict the behavior of a celestial body in the future. Although, according to current calculations, the probability of Duende colliding with the Earth before February 16, 2020 will not exceed one chance in 14,000.

Immediately after the discovery on December 28, 2005, the asteroid YU55 was classified as potentially hazardous. In diameter, the space object reaches 400 meters. He possesses elliptical orbit, which indicates the instability of its trajectory and unpredictability of behavior.
In November 2011, the asteroid has already aroused scientific world, flying up to a dangerous distance to the Earth of 325 thousand kilometers - that is, it turned out to be closer than the Moon. Interestingly, the object is completely black and almost invisible in the night sky, for which astronomers nicknamed it "Invisible". Scientists then seriously feared that a space alien would enter the earth's atmosphere.

An asteroid with such an intriguing name is an old acquaintance of earthlings. It was discovered by the German astronomer Karl Witt back in 1898 and was the first near-Earth asteroid discovered. Eros also became the first asteroid to acquire artificial satellite. It's about about spacecraft NEAR Shoemaker, which landed on a celestial body in 2001.
Eros - largest asteroid internal solar system. Its dimensions are amazing -33 x 13 x 13 km. average speed giant 24.36 km/s. The shape of the asteroid is similar to a peanut, which affects the uneven distribution of gravity on it. The impact potential of Eros in the event of a collision with the Earth is simply enormous. According to scientists, the consequences after an asteroid hit our planet will be more catastrophic than after the fall of Chicxulub, which allegedly caused the extinction of dinosaurs. The only consolation is that the chances of this happening in the foreseeable future are scanty.

Asteroid 2001 WN5 was discovered on November 20, 2001 and later fell into the category of potentially hazardous objects. First of all, one should be afraid that neither the asteroid itself nor its trajectory have been sufficiently studied. According to preliminary data, it can reach 1.5 kilometers in diameter.
On June 26, 2028, the next approach of the asteroid to the Earth will take place, and the cosmic body will approach the minimum distance for itself - 250 thousand km. According to scientists, it can be seen through binoculars. This distance is enough to cause satellites to malfunction.

This asteroid was discovered by Russian astronomer Gennady Borisov on September 16, 2013 using a homemade 20 cm telescope. The object was immediately called perhaps the most dangerous threat among celestial bodies for the Earth. The diameter of the object is about 400 meters.
The approach of the asteroid to our planet is expected on August 26, 2032. According to some assumptions, the block will sweep only 4 thousand kilometers from the Earth at a speed of 15 km / s. Scientists have calculated that in the event of a collision with the Earth, the energy of the explosion will be 2.5 thousand megatons of TNT. For example, the power of the largest thermonuclear bomb detonated in the USSR is 50 megatons.
To date, the probability of an asteroid colliding with the Earth is estimated at about 1/63,000. However, with further refinement of the orbit, the indicator can either increase or decrease.