When main-sequence stars expand into red giants, they are expected to engulf close-in planets. Until now, the absence of planets with short orbital periods around post-expansion, core-helium-burning ...red giants has been interpreted as evidence that short-period planets around Sun-like stars do not survive the giant expansion phase of their host stars. Here we present the discovery that the giant planet 8 Ursae Minoris b orbits a core-helium-burning red giant. At a distance of only 0.5 au from its host star, the planet would have been engulfed by its host star, which is predicted by standard single-star evolution to have previously expanded to a radius of 0.7 au. Given the brief lifetime of helium-burning giants, the nearly circular orbit of the planet is challenging to reconcile with scenarios in which the planet survives by having a distant orbit initially. Instead, the planet may have avoided engulfment through a stellar merger that either altered the evolution of the host star or produced 8 Ursae Minoris b as a second-generation planet. This system shows that core-helium-burning red giants can harbour close planets and provides evidence for the role of non-canonical stellar evolution in the extended survival of late-stage exoplanetary systems.
This paper documents H2O loss from vapour-absent melting (dehydration-melting) experiments with durations of 5-31 days in a piston cylinder apparatus at 7, 10 and 15 kbar and 925-1000°C.
As relevant technologies become smaller and less expensive, micro air vehicles (MAVs) are transitioning from predominantly military and hobbyist applications to mainstream use. Exciting new ...applications include the delivery of medical supplies to remote areas, infrastructure inspection, environmental change detection, precision agriculture, survelliance of visible satellites. These issues are particularly prevalent when flying near the ground, where safety and reliability are especially important.
Minerals of the Hutter Mine Beard, James S.; Tracy, Robert J.; Henika, William S.
Rocks & minerals,
10/1/2002, 2002-10-00, Letnik:
77, Številka:
5
Journal Article
Scientific ocean drilling started in the early 1960s with the goal of understanding the nature of the crust-mantle boundary (the Mohorovicic discontinuity, or the Moho). This project, known as ...Mohole, was succeeded by the Deep Sea Drilling Project, the International Phase of Ocean Drilling, the Ocean Drilling Program, and the current Integrated Ocean Drilling Program. The major scientific goal common to all these efforts has been to recover a complete section of normal ocean crust and uppermost mantle, with the ultimate objective of understanding solid Earth cycles. This decades-old goal has not yet been fulfilled, but as geological and geophysical studies and scientific drilling have progressed over the years, we have learned a lot more about the oceanic crust. One striking discovery was that portions of slow-spreading ridges are volcanic-poor areas, classically interpreted as magma-starved regions, made of outcropping lower crust or upper mantle rocks (e.g., Cannat and Casey, 1995; Lagabrielle et al., 1998). Locally, lower crustal sections may be exposed on the seafloor by long-lived detachment faults that potentially provide a means of accessing the crust-mantle boundary. These detachment faults are exposed at the seafloor in shallow, dome-shaped features, with prominent surface corrugations trending parallel to the direction of plate spreading (e.g., Cann et al., 1997; Tucholke et al., 1998). Rocks recovered from or within a few tens of meters of the corrugated surfaces include highly deformed fault gouges and mylonites (Blackman et al., 1998; MacLeod et al., 2002; Escartin et al., 2003; Schroeder and John, 2004). The detachment faults and the corresponding series of offset tectonic blocks are referred to as oceanic core complexes (OCC), by analogy with metamorphic core complexes (e.g., Wernicke, 1981) in extensional continental terranes. The rolling hinge model (Fig. 1) of core complex formation predicts that large rotations would characterize the tectonic blocks within an OCC; as deep lithospheric rocks are exhumed along the fault, the footwall of the detachment fault (i.e., core) rolls over, laying out the geological cross section across the seafloor (Wernicke and Axen, 1988; Buck, 1988; Lavier et al., 1999).
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