Here I list some unexpected scientific results in recent years, which I find very interesting. It is highly incomplete, if you have other suggestions, drop me an e-Mail.
2019.01: What are Fast Radio Bursts?
There are millisecond high-energetic bursts of radiowave light being observed for the first time in 2017. Most of the bursts happen only one time, never to be repeated. In 2012, the first unperiodically repeating FRB has been observed. In 2019, a new observational side called CHIME has started their observations, and report (using data from calibration runs!) first observation of a second repeating FRB source, in addition to 12 other FRBs. Hopefully this new instrument can help finding the source of this unexpected observations.
2018.03: Gravitational Wave Echos from Black Holes
If event horizons have special structure, one would expect echos in gravitational waves. This is not predicted by General Relativity. Indication of these echos have maybe been observed: See Quanta and PRD paper, and earlier Nature News.
2017.08: Investigation of Dark Matter via Gravitational Lensing and Planck Satellite contradict each other
See Nature News article. Gravitational waves could help, as an independent method for measureing Hubble’s constant, as shown in this Nature paper.
2017.06: Two reviews on discrepancies at LHC
Editorial in Nature, Flavour-changing neutral currents making and breaking the standard model, A challenge to lepton universality in B-meson decays
2017.06: 7sigma discrepancy at hyperfine-structure measurement of Bismuth
See Nature Communications article.
2017.06: Discrepancy of b-quark production at LHCb with measurements at 13TeV and QCD calculations
2016.10: DAMA (DArk MAtter) finds annual oscillation
2016.08: CP violation in neutrino oscillation
Apparently, oscillations are different for Neutrinos and Antineutrinos. See Quanta.
2016.02: Antineutrino Flux and Spectrum discrepancy
Locally: 4 sigma deviation from SM; globally: 2 sigma. See PRL.
2016.02: Kepler telescope finds short, nonperiodic brightness reductions of up to 22%, unclear interpretations
See Wikipedia and PRL (giving a possible interpretation due to intrinsic critical processes) for Tabby’s Star.
2015.12: ATLAS: 2.5sigma global statistic for a 2TeV decay in WZ channel
See Journal of High Energy Physics.
2015.12: Proton Size Puzzle
Apparently the proton is 4% smaller than expected, which has been observed with myonic hydrogen in 2010, with improved measurements in (which constituted to a 7 sigma deviation from CODATA values). Also myonic deuterium indicates a smaller proton radius, as shown in 2016. Very recent cryogenic electronic hydrogen measurements indicate a similar discrepancy from CODATA value and agree with the myonic value; the discrepancy seem to stem from an unnoticed systematical effect in form of quantum interferences.