The potentially dangerous asteroid (99942) Apophis

Wlodarczyk, I.

doi:10.1093/mnras/stt1227

Cited by 14 publications

(6 citation statements)

References 12 publications

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“…2 http://neo.jpl.nasa.gov/risk http://newton.dm.unipi.it/neodys orbital evolution of this asteroid (Žižka & Vokrouhlický 2011;Farnocchia et al 2013;Wlodarczyk 2013). The lack of availability of such properties (albedo, size, shape, rotation, physical structure, thermal properties) is a major limiting factor that leads to uncertainties in the role played by non-gravitational effects on that orbit.…”

Section: Introductionmentioning

confidence: 99%

Thermal infrared observations of asteroid (99942) Apophis withHerschel

Müller

Kiss

Scheirich

et al. 2014

A&A

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The near-Earth asteroid (99942) Apophis is a potentially hazardous asteroid. We obtained far-infrared observations of this asteroid with the Herschel Space Observatory PACS instrument at 70, 100, and 160 μm. These were taken at two epochs in January and March 2013 during a close-Earth encounter. These first thermal measurements of Apophis were taken at similar phase angles before and after opposition. We performed a detailed thermophysical model analysis by using the spin and shape model recently derived from applying a two-period Fourier series method to a large sample of well-calibrated photometric observations. We found that the tumbling asteroid Apophis has an elongated shape with a mean diameter of 375 −0.06 . We found a thermal inertia in the range 250-800 Jm −2 s −0.5 K −1 (best solution at Γ = 600 Jm −2 s −0.5 K −1 ), which can be explained by a mixture of low-conductivity fine regolith with larger rocks and boulders of high thermal inertia on the surface. The thermal inertia, and other similarities with (25143) Itokawa indicate that Apophis might also have a rubble-pile structure. If we combine the new size value with the assumption of an Itokawa-like density and porosity we estimate a mass between 4.4 and 6.2 × 10 10 kg, which is more than 2-3 times larger than previous estimates. We expect that the newly derived properties will influence impact scenario studies and the long-term orbit predictions of Apophis.

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Section: Introductionmentioning

confidence: 99%

Thermal infrared observations of asteroid (99942) Apophis withHerschel

Müller

Kiss

Scheirich

et al. 2014

A&A

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“…We presented the orbital elements of asteroid 2009 FJ, its ephemerides with uncertainties for the next 100 years. This paper contin ues a long term research program on impact solutions for asteroids (Wlodarczyk, 2007;2008;2009). Finally, our method for computing impact orbits provides an easy means of computing the path of risk for asteroids approaching the Earth or any other body of the solar system.…”

Section: Discussionmentioning

confidence: 99%

Impact orbits of the asteroid 2009 FJ with the Earth

Wlodarczyk

2012

Sol Syst Res

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We show how to calculate the impact orbits of dangerous asteroids using the freely available the OrbFit software, and compare our results with impact orbits calculated using Sitarski's independent software (Sitarski, 1999;2000;2006). The new method is tested on asteroid 2009 FJ. Using the OrbFit package to inte grate alternate orbits along the line of variation (Milani et al., 2002;2005a;2005b), we identify impact orbits and can plot paths of risk for the Earth or any other body in the Solar System. We present the orbital elements of asteroid 2009 FJ and its ephemerides, along with uncertainties, for the next 100 years. This paper continues a long term research program on impact solutions for asteroids (Wlodarczyk,

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“…Previous observations of the trajectory of asteroid 99942 Apophis have shown that on April 13, 2029, it will pass within six Earth radii from our planet. Since its discovery in 2004, the probability of impact has been reduced from 2.7% to practically nil (Chesley 2005;Wlodarczyk 2013); however, Apophis still provides unique opportunities in terms of asteroid studies, which are usually limited to very distant and faint objects, relatively small ones passing close-by (in the tens of meters range), theoretical modeling, or morphology estimations with low resolution radar observations (Herique et al 2020). This time, the asteroid will come to us.…”

Section: Introductionmentioning

confidence: 99%

Conditions for visual and high-resolution bistatic radar observations of Apophis in 2029

Vallejo¹,

Zuluaga²,

Molano³

2022

Preprint

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On April 13, 2029, asteroid 99942 Apophis will pass within six Earth radii (∼31000 km above surface), in what will be the closest approach of this asteroid in recorded history. This event provides unique scientific opportunities to study the asteroid, its orbit, and surface characteristics at an exceptionally close distance. In this paper we perform a synthetic geometrical, geographical and temporal analysis of the conditions under which the asteroid can be observed from Earth, with a particular emphasis on the conditions and scientific opportunities for bistatic radar observations, the only feasible radar technique applicable in such a close approach. For this purpose, we compile a list of present and future radio observatories around the globe which could participate in bistatic radar observation campaigns during the closest approach of Apophis. We estimate power, signal-to-noise ratios, surface coverage and other observing conditions. We find that a global collaboration of observatories in Australia, Africa, Europe and America might produce high-resolution delay-radar images with unprecedented signal-to-noise ratios and potential spatial resolution down to several meters, covering ∼87% of the asteroid surface. Moreover, if properly coordinated, the extreme approach of the asteroid might allow for radio amateur detection of the signals sent by large radio observatories and citizen science projects could then be organized. We also find that for visual observations, the mountain tops of Canary Islands will offer the best observing conditions during the closest approach, both for professionals as well as for amateurs. The apparent size of 99942 Apophis will be 2-3 times larger than typical seeing, allowing for resolved images of the surface.

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The potentially dangerous asteroid (99942) Apophis

Cited by 14 publications

References 12 publications

Thermal infrared observations of asteroid (99942) Apophis withHerschel

Thermal infrared observations of asteroid (99942) Apophis withHerschel

Impact orbits of the asteroid 2009 FJ with the Earth

Conditions for visual and high-resolution bistatic radar observations of Apophis in 2029

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