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.
I 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?
By 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.
Wikipedia says no efforts to measure the mass of 33 Polyhymnia have been made since 2012. The scientist who estimated its mass at that time regarded the result as nonphysical and in error.
Couldn't this mass be much more accurately estimated by sending a small probe of known mass by the asteroid at a known distance and velocity, and measuring the trajectory perturbation?
I think this could be done with a 5kg radar reflector. No guidance, no comms, no onboard electronics at all. Terrestrial radar measurements of position and velocity are extremely accurate. The launch wouldn't have to achieve super accurate trajectory, just good enough to see gravitational perturbation.
Not much of a launcher needed for this. It might even work as a ride-along payload. Could be a relatively low-cost way of resolving this weird density result.
Wait, you want to do a gravitational perturbation mission with 5kg, for a body of > 10^18kg? You'd have to do super duper precise measurements to notice anything (much more precise than anything we can do at the moment), and the reason we don't know the density is that we haven't done precise measurements yet.
How about just doing some more precise measurements first? I'm 99.99% certain that the high density estimate stops existing afterwards
Also, how exactly do you want to get an object without guidance or comms near enough to a main-belt asteroid?
This is all just ridiculous. Some theoretical physicist does some calculation around the Island of Stability, comes up with a high density, and tries to give his paper more relevance by finding an improbably dense astronomical object, and then wildly speculates that the two are related.
What are the chances that some rando asteroid consists of 100% of an element that we
1) don't know if it actually is stable
2) don't actually know the density of, besides a single paper about it
3) don't know any natural, plausible mechanism for synthesis
> Wait, you want to do a gravitational perturbation mission with 5kg, for a body of > 10^18kg? You'd have to do super duper precise measurements to notice anything
I don't think so. We would measure the effect of 33 Polyhymnia on the probe, not the other way around. Which would work if it got just in the vicinity of the asteroid. The mass of the probe wouldn't even matter.
You're right of course about the density being a wild guess, probably not worth pursuing because the odds of finding something interesting are just about 0.
Funny, just recently I was thinking about this since I have not heard about anything new regarding this in ages. Chemists call this an Island of stability.
But claiming, with very limited data, that this asteroid consists of ultraheavy, unknown elements of the periodic table violates Occams razor. I predict he is wrong.
Of course they are wrong. I can't read the actual article, it is behind a paywall, but my guess is that they qualify heavily any statements about superheavy elements on the 33 Polyhymnia asteroid, otherwise I can't see how it could pass peer review.
From the abstract of the article, it appears that it is simply presenting some numerical calculation that show that the element 164 would have a density in a certain range (36-68 g/cm3) given some models of the nucleus and of the electron shells. The numerical methods could be innovative enough that the article is worth publishing.
But 33 Polyhymnia being rich in this element is complete nonsense. There is no plausible scenario where an asteroid would be composed exclusively out of such an element. Heavy elements are created in supernova explosions. They are relatively rare. You can find them in small proportion among more frequent elements, such as iron, nickel, lead, etc. There is no scenario where you'd find only a superheavy element in isolation. Uranium has an average concentration of 2.8 parts per million on Earth.
Much, much more likely is that the estimation of the mass of 33 Polyhymnia was erroneous. Here's why: you can't measure the mass of a celestial object by how far it moves around the Sun. All objects will move with the same speed on the same orbit. You can however determine the mass of the Sun by observing a single planet. Similarly, you can measure the mass of Jupiter by observing how fast its satellites go around it. You only need one satellite, but if you have more, it will only increase your confidence. You can estimate like this the mass of all the planets, with a very high accuracy.
But you can't estimate the mass of small celestial objects that don't have satellites. Instead you look for n-body interactions, and there are such in the asteroid belt. But for any asteroid there, the main forces are the gravitational attraction to the Sun and Jupiter. A distant third will be Mars, and occasionally asteroids feel the gravitational influence of their neighbors. But not very often, because distances between asteroids are actually astronomical.
So, the most likely explanation (virtually certain) is that whoever estimated the density of 33 Polyhymnia to be 75 g/cm3 was simply wrong. There was no subsequent confirmation. 75 g/cm3 is such an extraordinary claim, the it requires truly extraordinary evidence, and such evidence is entirely lacking.
Abstract—In this paper, we present the last results of the OLIMPIA experiment on the search forand study of traces of heavy and superheavy element nuclei of galactic cosmic rays in olivine crystalsfrom meteorites. The charge spectrum of cosmic rays in the region of heavy nuclei is obtained, threesuperheavy nuclei of natural origin with charges in the range 105 <Z<130 and lifetimes longerthan 3000 years, being a part of the so-called “stability island”,areidentified.DOI: 10.3103/S1068335615050073
This is fine, but nothing to do with the claim that 33 Polyhmnia has a very high density. The study you cite mention "traces". Traces of heavy elements can't change significantly the density of an asteroid.
I wonder what sort of instruments could get a better measurement of that object’s weight without being just a probe to it? I’m guessing we’d need to get lucky for it to be bright enough and located right to be resolvable by JWST. Or would sending something to it be the cheaper option.
Sure wish we had many more telescopes and instruments spread throughout the solar system.
This is high school task, to measure "density of infinite layer of material" by measure its gravitational attractive force.
One don't need to touch material, but need to hang close to it and measure acceleration with some conventional instrument (for asteroid distance will be about few meters and acceleration around millimeters/s^2).
Can it be made of common elements, just very compressed? Like a piece of a disrupted giant planet core? IIRC, iron-nickel alloy in Earth core has about twice the normal density, due to pressure. Can those high densities be kept in case of planetary disruption, without it explosively decompressing?
Explosive decompression comes from internal pressure overcoming its container, where the pressure within the container is greater than without. The core of a planet is pretty much the opposite, where the pressure is coming from the outside and smushing things together. I know it seems similar, but it isn't really. You know how diamonds do not "explosively decompress" (explode) after they are formed? Think of it more like that.
Popping the core out of the centre of a planet intact would be your bigger challenge, I think. A collision with enough force to crack open a planet down to its core is probably not going to leave the core crystal intact.
Not even very compressed. Just enough to it, be monolith, as usual asteroids are just like stuck together small stones of irregular form, plus cosmic dust, also not dense.
Question is, that at the moment not found any similar asteroids, so this is not common for them, to appear such way.
So, when we see something so unusual, we have two options - they could be just from more heavy elements, or their history was unusual.
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.