Heute ist der 22.04.2025
Datum: 22.04.2025 - Source 1 (https://t3n.de/news/nasa-sonde-lucy-asteroid-donaldjohanson-1683857/):
- Die NASA-Raumsonde Lucy steht kurz vor ihrem zweiten Asteroiden-Vorbeiflug.
- Der Vorbeiflug findet am Sonntagabend um 19:51 Uhr MESZ statt.
- Lucy wird mit etwa 48.000 km/h am Asteroiden (52246) Donaldjohanson vorbeifliegen.
- Der Vorbeiflug erfolgt in einer Distanz von 960 Kilometern und etwa 223 Millionen Kilometern von der Erde entfernt.
- Donaldjohanson ist ein rund vier Kilometer langer, kohlenstoffreicher C-Typ-Asteroid.
- Lucy wird eine komplexere Beobachtungssequenz als beim letzten Vorbeiflug verwenden.
- Die Sonde ist mit Instrumenten ausgestattet, darunter die hochauflösende Kamera L’LORRI.
- Im Jahr 2023 besuchte Lucy den Asteroiden Dinkinesh und entdeckte einen Kontakt-Binär-Mond.
- Donaldjohanson ist nach dem Paläoanthropologen benannt, der das „Lucy“-Fossil entdeckte.
- Der Namensgeber plant, den Vorbeiflug live im Kontrollzentrum von Lockheed Martin in Denver zu verfolgen.
- Donaldjohanson gehört zur Erigone-Familie, die aus einer Kollision vor etwa 150 Millionen Jahren stammt.
- Der Asteroid hat eine langsame Rotation von rund 251 Stunden pro Umdrehung.
- Forscher:innen hoffen, durch die Bilder mehr über die Form und Oberflächenbeschaffenheit von Donaldjohanson zu erfahren.
- Nach dem Vorbeiflug wird Lucy ihre Reise zu den Trojaner-Asteroiden fortsetzen, die die Sonne auf derselben Bahn wie Jupiter umkreisen.
- Der erste Trojaner-Asteroid soll 2027 erreicht werden; die gesamte Mission dauert zwölf Jahre und umfasst elf Asteroiden.
- Während des Vorbeiflugs wird die Kommunikation zur Erde temporär unterbrochen.
- Erste wissenschaftliche Daten werden etwa einen Tag nach dem Vorbeiflug erwartet; die vollständige Übertragung dauert mehrere Tage.
Source 2 (https://iopscience.iop.org/article/10.3847/PSJ/adb4f4):
- Asteroid families are clusters of asteroids on similar orbits formed by high-energy collisions in the main belt.
- The largest asteroid families, including Themis, Eos, Koronis, and Flora, were discovered over a century ago (K. Hirayama, 1918).
- Research on asteroid families advanced in the 1970s and 1980s with improved catalogs and mathematical tools for defining stable orbital elements.
- The Erigone family was discovered by J. G. Williams in 1979, initially referred to as family 166, and was found near the Mars-crossing line.
- By the 2010s, the number of asteroids with determined proper elements exceeded 100,000, complicating family identification.
- A. Milani et al. (2014) developed an automated scheme for family determination, including the Erigone family, but did not focus on it.
- F. Spoto et al. (2015) and others proposed splitting the Erigone zone into two clusters but later confirmed it as a single family.
- The Erigone family exhibits primitive surface materials with low thermal processing, classified as C-type asteroids with low albedo (pV < 0.125).
- The family is located in the inner main belt, dominated by S-type asteroids.
- Age determination methods for asteroid families include collisional evolution studies and dynamical considerations.
- For young families (<20 Myr), direct backward orbital propagation can reconstruct family structure from collision events.
- For older families, statistical methods are used, such as analyzing Yarkovsky thermal drift.
- D. Vokrouhlický et al. (2006b) identified the Erigone family as an ideal test case, estimating its age at 280 ± 100 Myr.
- Subsequent analyses yielded similar age estimates, indicating the Erigone family is relatively young (a few hundred Myr).
- F. Marzari et al. (1999) attempted to determine the family age through collisional modeling, resulting in inconclusive findings.
- An updated method by M. Brož et al. (2024a) estimated the age at 500 ± 100 Myr, which is older than previous estimates.
- The study aims to analyze the Erigone family before the Lucy mission's close encounter with DJ, using updated asteroid catalogs.
- The Hierarchical Clustering Method (HCM) was applied to identify the Erigone family, resulting in 4925 members, including DJ.
- The family members are distributed in the proper element space, with the largest member, Erigone, at the center.
- The Erigone family is affected by high-order secular resonances, including z2, which may lead to contamination by interloping objects.
- The family is located near Mars-crossing orbits, with some members potentially leaking into the terrestrial planet region.
- The size distribution of Erigone family members shows a characteristic pattern, with larger objects near the center and smaller members dispersed outward.
- The Yarkovsky and YORP effects influence the orbital evolution of family members, leading to a Gaussian-type distribution for smaller members.
- Albedo data from WISE observations indicate a predominance of dark-albedo objects in the Erigone family.
- The nominal family contains 889 members with WISE size and albedo values, showing a median albedo of 0.05 ± 0.01.
- The study aims to provide a realistic range of age solutions for the Erigone family based on Yarkovsky/YORP modeling.
- The Erigone family is hypothesized to have formed from a modestly larger than catastrophic disruption event, with an estimated parent body size of around 80 km in diameter.
- The collisional age of the Erigone family is investigated using the CoDDEM model to track collisional evolution and compare with observed size-frequency distributions.
- The results suggest that the Erigone family is less than 300 Myr old, with DJ's membership based on circumstantial evidence and orbital characteristics.
Source 3 (https://arxiv.org/pdf/1701.03761):
Weitere Informationen finden Sie auf https://arxiv.org/pdf/1701.03761