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617 Patroclus and MenoetiusA Binary Minor Planet
Outline
1. Introduction
2. Patroclus and Menoetius1. Detection and parameters
2. Composition
3. Orbital angular momentum
3. Conclusion and Outlook
Patroclus a Trojan Asteroid
• The Trojans are in the astronomieasteroids around the Lagrangianpoints L4 and L5 of Jupiter
• They are named after the warriors ofthe trojan war and sperated in thetwo camps
• Two exceptions: Patroclus and Hector who were discovered before theconfession and are therefore in theoposite Lagrangian point
Discovery of Patroclus
• Patroclus was discovered on the 17th of October in 1906 by Kopff, A. at Heidelberg
• It was the secound trojan asteroid discovered after Hector
• It has a diameter of 122±3 km and the mass of the total system is 1.36 ± 0.11 × 1018 kg and therefore a density of 0.88 ± 0.17
𝑔𝑐𝑚3
• It has a absolute magnitude of 8.19 mag
Discovery of Menoetius
• Menoetius was discovered on 22nd of September in 2001 from: William J. Merline, Laird M. Close, N. Siegler, D. Potter, Clark R. Chapman, Christophe Dumas, François Menard und David C. Slater
• It was discovered with the 8.1 meter-Gemini-North-Telescope in Hawaii
• With a diameter of 112.6 ± 3.2 km it is about 7% smaller than Patroclus
The binary system parameters
Period (days) 4.283 ± 0.004
Semi-major axis (km) 680 ± 20
Eccentricity, e 0.02 ± 0.02
Orbit pole solution ECJ2000 (λ and β in degrees)
λ = 236 ± 5, β = -61 ± 1
Pericentre argument (degrees) 139
Time of passage (Julian days, JD) 2453171.1 ± 0.1
Total mass (kg) (1.36 × 1018) ± 0.11
Bulk density of the system* (g 𝑐𝑚−3) 0.8± 0.17 𝑔 𝑐𝑚3
The orbital angular momentum
• The origin of this tightly bound, small-eccentricity and large angular-momentum binary system remains unclear
• Could be the reuslt of a capture, with subsequent circularization ofthe orbit by tidal effects
• Other explination could be a low velocity impact of large projectile(less probable)
• Could also be formed by tidal effects after low-velocity encounterwith large planet
• Spin periods of components unknown
• Probable a unsynchronized system
Composition of the Asteroids
• Similiar distant to Sun like Galileansatallites → mixture of ice and androck (≜ 50% porosity )
• With the low density of 0.88 ± 0.17
𝑔𝑐𝑚3 it is quite probable that they
consist of water/ice (≜ 15%porosity).
• Referring to Dynimical simulations itis possible that they were formed in the outer solars system
Conclusion and Outlook
• Formation unclear
• Simulations show that several distant planetesimals have a close approach with Jupiter before their final capture at the Lagrange points
• a special programme of photometric observations should be undertaken to attempt to derive the spin poles and rates.
Thank you for your attention!
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