One can’t fault astronomers for not knowing everything – only for pretending to. Here are some surprises indicating they have a long way to go.
Earth and Moon
Earth’s Inner Core Shouldn’t Technically Exist (Live Science). Talk about upsets; the “conventional story” of Earth’s core is “impossible,” this report says. Supposedly, earth’s core consists of metals that crystallized in the mantle and sank to the center of the Earth. Rejection of that possibility presents two new problems:
In the paper [in Earth and Planetary Science Letters], the researchers argued that the standard model of how the Earth’s core formed is missing a crucial detail about how metals crystallize: a mandatory, massive drop in temperature that would be extremely difficult to achieve at core pressures.
Weirder still, the researchers said, once you account for this missing detail, the science seems to suggest that Earth’s inner core shouldn’t exist at all.
Why is this difficulty showing up now? “Everyone, ourselves included, seemed to be missing this big problem,” one of the authors said. Do they have a rescue device? Well, sort of. If a big chunk dropped into the mass, it might have nucleated crystal growth. But it would take an implausibly big object to do that. The authors are calling on other geophysicists to offer ways out of “Earth’s inner core nucleation paradox.” Coverage on Phys.org in layman’s terms challenges “core beliefs” asking, “Have we misunderstood how Earth’s solid center formed?” (Notice the tontology in the headline.)
New study sheds light on moon’s slow retreat from frozen Earth (Astrobiology Magazine). Students of secular geophysics are aware of two long-standing challenges: the “faint young sun paradox” and the moon’s orbital recession from the Earth. The latter implies our moon would have been catastrophically close to the Earth in only a fraction of the assumed age of the solar system. This article says the moon is currently receding at 4cm (1.56 in) per year. If that rate is extrapolated back in time, it would imply the moon would have pumped enormous energy into the earth. Modelers at the University of Colorado at Boulder are trying to tweak the Snowball Earth hypothesis and the faint young sun paradox to make things work out, but admits in the end that “direct observational evidence in the geological record is currently lacking, making it the subject of debate among scientists.”
How the planet’s poles keep trading places (Nature). This book review may be of interest for those wanting to understand how Earth’s magnetic field protects its inhabitants, or who wish to read about and evaluate modern theories of geomagnetism and how they were developed since the ancients first puzzled over magnetism.
Many stars don’t form in clusters (Science Magazine). The old textbook story said that stars form from fragmenting gas clouds, and so tend to form first in clusters then spread out. That’s apparently wrong, this short article says:
Associations of young stars (no more than a few million years old) should therefore be slowly expanding. Ward and Kruijssen use astrometric data to test this idea by looking for evidence of expansion in several nearby young associations. They do not find any; the associations show no sign of ever having been gravitationally bound. The authors suggest that this indicates that star formation is dominated by turbulent fragmentation, not monolithic collapse.
Dwarf galaxies move in unexpected ways (Science). According to textbook models, satellite galaxies (dwarf galaxies) should be randomly distributed around giant galaxies. New observations dispute the models.
They found that the satellites are distributed in a planar arrangement, and the members of the plane are orbiting in a coherent direction. This is inconsistent with more than 99% of comparable galaxies in simulations. Centaurus A, the Milky Way, and Andromeda all have highly statistically unlikely satellite systems. This observational evidence suggests that something is wrong with standard cosmological simulations.
See also the lengthier analysis in Science by Michael Boylan-Kolchin, and the associated research paper by Müller et al. in Science that says the findings “challenge cold dark matter cosmology.” An article about this on Phys.org notes that the situation at Centaurus A “contradicts common cosmological models, simulations.” New Scientist agrees, saying in tontological manner, “Dancing galaxies may shake up our ideas of galaxy formation.”
There could be entire stars and planets made out of dark matter (New Scientist). Such speculative ideas about mysterious unknown stuff like dark matter hardly deserve to be called science at all. Let the staff at New Scientist come back when they figure out what dark matter is and if it even exists.