(99942) Apophis

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Asteroid
(99942) Apophis
Apophis
Properties of the orbit ( animation )
Epoch:  September 30, 2012 ( JD 2,456,200.5)
Orbit type Aten type
Major semi-axis 0.9223  AU
eccentricity 0.1911
Perihelion - aphelion 0.7461 AU - 1.0985 AU
Inclination of the orbit plane 3.3320 °
Sidereal period 323 d 12 h
Mean orbital velocity 31.019 km / s
Physical Properties
Medium diameter 325 ± 15 m
Dimensions ~ 5 · 10 10Template: Infobox asteroid / maintenance / mass kg
Albedo 0.23
Rotation period 30 h 37 m
Absolute brightness 19.7 mag
history
Explorer R. Tucker , DJ Tholen ,
F. Bernardi
Date of discovery June 19, 2004
Another name 2004 MN 4
Source: Unless otherwise stated, the data comes from JPL Small-Body Database Browser . The affiliation to an asteroid family is automatically determined from the AstDyS-2 database . Please also note the note on asteroid items.

(99942) Apophis is a near-Earth asteroid of the Aten type with a diameter of more than 300 m, which Roy Tucker , David J. Tholen and Fabrizio Bernardi discovered during the University of Hawaii Asteroid Survey at the Kitt Peak National Observatory on June 19, 2004.

Observations over a few months showed that the asteroid, provisionally designated 2004 MN 4 , will come very close to Earth on April 13, 2029. For a short time, a collision probability of 2.7% was calculated and a rating of 4 on the Turin risk scale was made with corresponding media coverage. Days later it was identified in older photos, its path was assessed as much less unsafe and a collision in 2029 was ruled out. According to these new calculations, it will fly past Earth over the ring of geostationary satellites in 2029 . At this millennium event , it will reach an apparent brightness of 3.3 mag, but remain point-shaped in binoculars .

This close flyby will drastically change its orbit. However, the earth will also cross the asteroid's new orbit on April 13th each year. Already in 2036 there will be another approximation. The exact distance is not yet known as small uncertainties regarding the position will quickly increase on April 13, 2029 after the deflection.

The European Space Agency reports current data on the asteroid and other near-earth objects on its Space Situational Awareness website .

Between 2008 and 2011, Apophis was close to the sun and was therefore unobservable. At the beginning of 2012, a collision in 2036 could then be ruled out based on optical measurements. This finding was extended to the entire 21st century through much more precise radar measurements during the conjunction in early 2013.

Its discoverers named MN 4 in 2004 after the Egyptian deity Apophis , also after the antagonist of the same name in the science fiction series Stargate .

train

By 2029, Apophis will move around the Sun at a distance of 0.746 ( perihelion ) to 1.098 ( aphelion ) astronomical units in 323 days and 12 hours . The eccentricity of the path is therefore 0.191. Its orbit is only slightly inclined towards the ecliptic at 3.331 degrees and crosses the earth's orbit at a relative speed of 5.87 km / s. It rotates around its axis once every 30 hours and 37 minutes. The exact orientation of the axis is not yet known, but is important for the direction of the Jarkowski effect .

Apophis will pass the earth on Friday, April 13, 2029 at about 7.4 km / s at about 38,000 kilometers above the earth's surface. The proximity to the earth will change its orbit and its own rotation considerably, in particular its semi-major axis will increase to over 1.1 AU, so that it is then considered to be an Apollo type .

Possible consequences of an impact

Apophis would release about 900 megatons of energy  (TNT equivalent) in the event of an impact . By comparison, the largest human-made nuclear explosion (caused by the Tsar bomb ) was equivalent to 50 megatons of TNT. The energy release of an earthquake, the thickness  8.0 corresponds to about 1000 Mega tons of TNT.

The exact consequences of an impact would depend on the composition of the asteroid and the location and angle of the impact. An impact on the mainland would cause massive regional damage; however, a distance of around 250 kilometers from the point of impact could already be sufficient for a very high probability of survival. An impact in deep water would pose a large-scale risk of massive tsunamis , which could reach a height of more than 100 meters on nearby coasts and 30 meters on distant coasts.

For global destruction, the impact energy would have to be 100 times greater.

Chronicle of prognoses and observations

The original NASA report of December 23, 2004, which was circulated in the media, named an impact probability of "about 1 in 300". The actual estimate by NASA at this point in time was 1 in 233 and resulted in the classification on level 2 of the Turin scale . As the day went on, NASA's estimate (after 64 observations) was increased to 1 in 62 (corresponding to 1.6 percent). This achieved level 4 on the Turin scale. Apophis is the first object that, even if only for a short time, achieved a higher risk assessment than level 1. On the Palermo scale , the risk rating of the impact was 1.80.

On December 24, 2004, the probability was initially given as 1 in 42 (2.4 percent) and later (after 101 observations) with 1 in 45 (2.2 percent). (The tsunami that took place shortly afterwards in the Indian Ocean , however, pushed the reports about Apophis somewhat out of the public eye.)

On December 27, 2004, the impact probability (after 176 observations) was increased to 1 in 37 (2.7 percent). In the course of that day, the accuracy of the orbit data was significantly improved by additionally evaluating older recordings. This ruled out a collision, but not yet a passage within the Roche border . This followed on February 3, 2005 with the announcement of the results of a Doppler radar survey carried out over several days by the Arecibo Observatory .

The rating on the Turin scale was lowered to 0 for 2029, but left at 1 for 2036. This meant that the distribution for the possible positions on April 13, 2036 was still so extensive that it included the earth. The orbits that would hit the earth were only a few 100 m apart for the encounter in 2029. It was not yet ruled out that this gravitational keyhole would be hit. In addition, the exact location of the keyhole itself was still uncertain: Although recent work has led to a better understanding of the possible path disruptions, due to the lack of new data, it has not yet led to more precise predictions - a situation similar to that of 1950 DA . On December 14, 2006, the Planetary Society donated a prize of $ 50,000 for elaborated proposals on how a mission to Apophis could determine its orbit within a decade so precisely that a decision on countermeasures could be made dependent on the result.

The winners were announced on February 26, 2008. The missions were all about probes that were only supposed to accompany the asteroid - after all, the focus was on its focus, not an arbitrary impact point.

None of these proposals was implemented, because a re-evaluation of previous observations was sufficient to safely rule out a meeting of the keyhole : On October 7, 2009, NASA reduced the probability of a collision in 2036 from 1 in 45,000 to 1 in 250,000. The rating on the Turin scale was lowered to 0 and the value on the Palermo scale became negative. The latter means that Apophis' impact probability was now lower than that of any other object of comparable size hitting the earth.

In January 2013 the Herschel space telescope was used to measure the thermal radiation of Apophis and, by comparing it with the reflected light, estimated its diameter to be 325 ± 15 m. The shape and axis of rotation are still unknown.

Others

In February 2016, a researcher at the Makejew missile center in Russia suggested the use of optimized ICBMs for possible asteroid defense; the test target could be (99942) Apophis .

Web links

Commons : (99942) Apophis  - collection of images, videos and audio files

Individual evidence

  1. ↑ chs: Asteroid Apophis: Cosmic troublemaker bigger than assumed. In: Spiegel Online . January 10, 2013, accessed December 29, 2019 .
  2. ↑ astronews.com: Possible hit on April 13, 2029 , one of the more serious news reports on April 27/28. December 2004.
  3. ↑ a b J.D. Giorgini et al .: Predicting the Earth encounters of (99942) Apophis. Icarus 193, 2008, pp. 1-19, ( online ).
  4. ↑ daserste.de: Asteroids - Danger from the depths of space
  5. ↑ Near Earth Object Asteroid: 99942 Apophis. European Space Agency, accessed January 10, 2020 .
  6. ^ ESA Near Earth Object Risk List. European Space Agency, accessed January 10, 2020 .
  7. ↑ a b NASA / JPL: Nasa Refines Asteroid Apophis' Path Toward Earth. October 7, 2009.
  8. ↑ a b D. Bancelin ua: Asteroid (99942) Apophis: new predictions of Earth encounters for this potentially hazardous asteroid. A&A 544, 2012, doi: 10.1051 / 0004-6361 / 201117981 , (online) (PDF; 376 kB)
  9. ^ Bill Cooke: Asteroid Apophis set for a makeover . astronomy.com, August 18, 2005, archived from the original on July 23, 2014 ; accessed on September 7, 2014 (English).
  10. ↑ Calculate the day of the week. Retrieved February 3, 2018 .
  11. ↑ NASA / JPL: Near-Earth Asteroid 2004 MN4 Reaches Highest Score To Date On Hazard Scale. December 23, 2004 with update the following day.
  12. ↑ Possibility of an Earth Impact in 2029 Ruled Out for Asteroid 2004 MN4. December 27, 2004.
  13. ↑ NASA / JPL: Radar Observations Refine the Future Motion of Asteroid 2004 MN4. February 3, 2005.
  14. ^ Apophis Mission Design Competition
  15. ↑ Herschel intercepts asteroid Apophis. January 9, 2013, accessed January 25, 2013 .
  16. ↑ Christoph Seidler: With ICBMs: Russian engineer wants to shoot down asteroids. In: Spiegel Online . February 14, 2016, accessed December 29, 2019 .
  17. ^ Albert Khoury: Russia aims to point its ICBMs at the asteroid Apophis in 2036. In: yahoo.com. February 14, 2016, accessed December 29, 2019 .