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Estimate of density at 75 g/cm3 is a result of only a single study done in 2012 based on observed gravitational influence by 33 Polyhymnia on other Solar System
by anovikov 3y ago
Estimate of density at 75 g/cm3 is a result of only a single study done in 2012 based on observed gravitational influence by 33 Polyhymnia on other Solar System bodies. Because asteroid is small and it's gravity is weak too, such measurements are highly imprecise and that's the most likely explanation.
Discovery of actual elements with such a density would have a profound impact on design of compact, low-yield nuclear weapons and potentially even pure fusion ones! But that's just a fantasy. No one will rush to build a space probe to 33 Polyhymnia, because it's nearly safe to assume that the 2012 study is simply an error.
- changoplatanero 3y agoI can understand how you could get a good estimate of an asteroid mass by observing its orbit but how could they accurately measure the volume from far away? Maybe they check how bright it is but then how do you control for differences in reflectivity?
- anovikov 3y agoBy stellar occultations. Because angular speed of movement of asteroid on the sky is precisely known, observing a few occultations allows for precise measurement of it's diameter. That one is easy. But determining mass is not at all easy (and no you don't do it by observing it's orbit, it will be the same regardless of mass - you do it by observing orbits of all other things - especially those that happened to pass close to it). For heavy objects it's not that hard but for such a small thing, exceedingly hard.
- adrenvi 3y agoSome more info on asteroid occultations: https://britastro.org/2018/observing-asteroid-occultations-with-digital-cameras https://britastro.org/2018/observing-asteroid-occultations-w...