Slashdot Aug-Sept 21

Slashdot Submissions – Aug 2021

It has been a while since I posted anything, and the potential submissions have been piling up. 

Arxiv Ref	Title	Comments
2108.09868	The Orbit of Planet Nine	Probably the most interesting to the general reader.
2108.07207	(216) Kleopatra, a low density critically rotating M-type asteroid	Partly the “M-class” (no, not Star Trek), but in itself interesting because quite large asteroids can get spun up to the point of shedding matter from their extremities.
2108.03343	On the Need for a Classification System for Consistent Characterization of the Composition of Planetary Bodies	An actual planet classification.
2108.03323	Warm terrestrial planet with half the mass of Venus transiting a nearby star	New competitor for lightest planet known – check on Exoplanets.org
2108.05321	Ross 19B: An Extremely Cold Companion Discovered via the Backyard Worlds: Planet 9 Citizen Science Project	Its the citizen science that is most interesting.
2108.01422	The interior of hairy black holes in standard model physics	Funny phrase – save it for next time someone is whinging about Uranus.
2108.01471	What’s inside a hairy black hole in massive gravity	ditto
2108.01783	Comment on “Observation of a Neutrino Burst from the Supernova SN1987A”	There was a 7.3 second gap during the records of neutrinos from SN1987A at Kamiokande. This is suggested to be a hardware eror, when the tape staging recorder experiences a write error and performs a rewind-reset, which takes about this period of time.

1 - Planet Nine

Ever since the demotion of Jupiter, any mention of "Planet Nine" invariably attracts a swarm of comments about how, for some people, "Planet Nine will always be 134340 Pluto. Well, that battle has been fought and lost, and @plutokiller (Professor Mike Brown of Caltech, USA) himself has moved on to trying to find a new Planet Nine. In 2016 an analysis of the orbits of the largest, most distant "minor bodies" of the Solar system suggested that there may be a large planet "out there", controlling the distribution of these (relatively) large, distant bodies orbits, and from that inferring where they think their suggested planet would be seen on the sky.

Such efforts have a patchy history. Certainly LeVerrier is famous for predicting the position of Neptune from irregularities in the orbit of Uranus (cue whooping from the peanut gallery), but equally certainly he was working with an inaccurate data for the masses of solar system bodies (Uranus, particularly), and his result was correct by luck, not judgement. Similarly, the calculations which led to the discovery of 134340 Pluto were also based on inaccurate mass data leaving the mass of 134340 Pluto uncertain between the mass of Earth and "very small". The fly-by of a spacecraft - Voyager 2 - greatly improved the measurement of Uranus's mass, which is crucial to understanding the motions of the rest of the Solar system.

Since Brown (and others) started discovering multiple bodies of mass comparable to that of 134340 Pluto, orbiting in the same region of space, the identity of 134340 Pluto as a planet has been challenged, resulting in it's demotion to a "dwarf planet" in 2006. But since then, the discovery of more, and more distant, dwarf planets (including by Brown) has led to suggestions that they may hint at the presence of something big, "out there". Which Brown and colleagues have been looking for for several years, securing observing time on very large telescopes to carry out this work.

Their current best estimate of properties for Planet Nine is mass 6.2 (average: spread 8.4 - 4.9) Earth masses ; semi-major axis 380 (520- 300) AU ;  inclination 16 (21 - 11) degrees and an argument of perihelion of 300 (440 - 240) degrees (centred on Capricorn, but with a wide spread).

Hopefully they'll find it soon, because not finding it would only prove that they were looking in the wrong place at the wrong times, not that it doesn't exist.

This one posted 2021-09-02

2 - Kleopatra and planet classification.

3 – Ross 19b – a relatively nearby planet discovered by a Citizen Science project.