I know, I know, I switched back to writing these on Mondays again without telling anyone. It turns out, Wednesdays were a terrible choice of day for me. I swear I asked someone to fill in for me last week…
Astrophysics and Gravitation:
Taking a Swim in the Lagoon Nebula
NASA and the ESA Hubble Space Telescope, via the Advanced Camera for Surveys, have provided us with a gorgeous picture of the Lagoon Nebula. This nebula is of particular interest to amateur astronomers because it is one of only a few of its kind actually visible with the naked eye from Earth. While it may be a blurry oval to the unassisted human viewer, to Hubble, this gas cloud is a giant, dynamic, home to new stars. Okay, so there isn’t any new physics here, but they did get a great image.
For more, see Breaking Waves in the Stellar Lagoon.
AGILE on Gamma Rays
Marisaldi, M., et al. (2010). Gamma-Ray Localization of Terrestrial Gamma-Ray Flashes Physical Review Letters, 105 (12) DOI: 10.1103/PhysRevLett.105.128501
A team using satellite data to watch thunderstorms has figured out to to locate gamma rays (sometimes produced in said thunderstorms) with exceptional accuracy. These models are helping physicists understand gamma rays and how they relate to electrical storms (which most theories wouldn’t actually anticipate).
For more, see Pinpointing Earthly Gamma Rays.
ANITA on Cosmic Rays
S. Hoover, & et al. (2010). Observation of Ultra-high-energy Cosmic Rays with the ANITA Balloon-borne Radio Interferometer Physical Review Letters arXiv: 1005.0035v2
A team using airborne radio detectors has noticed a characteristic radio wave signal produced by ultrahigh energy cosmic rays as they hit the ice in the Antarctic. Since we still don’t know where these ultrahigh energy particles come from, being able to track them once they hit the earth will be a useful tool in figuring out where they originated from.
For more, see Tuning In to Highest Energy Cosmic Rays.
So Long S-Process
A. J. Gallagher, S. G. Ryan, A. E. García Pérez, & W. Aoki (2010). The barium isotopic mixture for the metal-poor subgiant star HD140283 Astronomy and Astrophysics arXiv: 1008.3541v1
Snipet from the abstract:
Current theory regarding heavy element nucleosynthesis in metal-poor environments states that the r-process would be dominant. The star HD140283 has been the subject of debate after it appeared in some studies to be dominated by the s-process. We provide an independent measure… that observations and analysis do not validate currently accepted theory.
It’s another one of these fun astrophysics mysteries. We have a reasonable idea how stars work, but every now and then an observation comes along and tells us that our theoretical mechanisms can not be the end all be all of star dynamics and formation. Star HD140283 is another fun piece to contradictory puzzle. Because of the suspected age of HD140283 (ie. that it’s very, very old), it should have formed in its galaxy before the first red giants/barium producing stars formed, meaning that it shouldn’t (and according to current theory, couldn’t) have inherited any barium from its neighbours (and thus undergo r-process nucleosynthesis). However, Gallagher et al.’s team’s observations say otherwise (that instead, we see s-process nucleosynthesis). Is the current model of star formation incorrect, ie. do we need to rethink this late production of s-process isotope issue? Could there have been barium somehow to kick off this stars life? Could it be something else? Could that star have somehow been pulled in from an older galaxy? At this point, it seems pretty open.
For more, see Ancient star poses galactic puzzle.
High Energy Physics and Particles:
Good news, everyone! We might have been way off about quarks and gluons!
CMS Collaboration (2010). Observation of Long-Range Near-Side Angular Correlations in Proton-Proton Collisions at the LHC JHEP arXiv: 1009.4122v1
So I’m late to the party here, but last week the CMS had some really exciting news: the LHC may have observed some new physics! Since I missed posting on this last week, I’ll defer to Jon Butterworth (an actual high energy physicist) on the results, here. Luboš Motl has some exciting speculation on what these observations might mean, but expect much more along these lines over the next few months.
For more, see A surprise from the LHC already!, LHC: CMS probably sees quark-gluon plasma or dual QCD string or something better, New two-particle correlations observed in the CMS detector at the LHC.
MiniBooNE Confirms LSND?
Richard Van de Water, A Decade Later: Are We Any Closer to Resolving the LSND Puzzle? GeneFest Symposium, September 25, 2010. PDF of the talk.
Remember those strange Liquid Scintillator Neutrino Detector results from 1997 that suggested some unusual neutrino oscillations inconsistent with the standard model (remember sterile neutrinos?)? Well, MiniBooNE says the LSND results might have been right after all. The results are still very preliminary and will probably start appearing more and more over the next month, but we may have to give up on three flavours of neutrinos… maybe.
For more, see MiniBooNE at GeneFest 2010.
General Relativity, Quantum Gravity, et al.:
Lehner, L., & Pretorius, F. (2010). Black Strings, Low Viscosity Fluids, and Violation of Cosmic Censorship Physical Review Letters, 105 (10) DOI: 10.1103/PhysRevLett.105.101102
Sure, I mentioned this paper last week, but I’m mentioning it again this week because a) it’s still really cool and possibly very important, and b) the APS did one of their great synopses on it this week. Check out Cosmic nudity.
Relativity on the Everyday Scale
Chou, C., Hume, D., Rosenband, T., & Wineland, D. (2010). Optical Clocks and Relativity Science, 329 (5999), 1630-1633 DOI: 10.1126/science.1192720
I’m late to the party on this one too, so it’s probably old news by now, but scientists at NIST have done some great “everyday” scale confirmations of relativity: that time passes faster at higher elevations and time passes slowler at higher velocities. We’ve had experimental confirmation of both of these facts for quite some time, but we’ve never had precise enough clocks to observe their subtle effects at everyday scales (ie. not just from orbit or in a particle accelerator). The NIST clocks were actually able to see the effect of gravitational time dilation between two surfaces, one just a foot above the other (so yes, time does pass faster if you’re standing on a table versus standing on the floor – Oh no, I live in a high rise apartment! My life is slipping by!). On top of that, so to speak, they also preformed an experiment showing measurable relativistic time dilation when their was only a 20 miles/hour difference between relative moving clocks. That is mind blowing, because these effects are incredibly subtle and we’d need to live billions of years to actually notice them. The fact that we can make clocks precise enough to notice them now, is incredible!
For more, see Everything really is relative, Time Dilation in Your Living Room, Revealing, Reveling In Einstein’s Relativity, NIST Pair of Aluminum Atomic Clocks Reveal Einstein’s Relativity at a Personal Scale (press release).
This (Long) Week in the Universe: September 16th – September 27th by PLOS Blogs Network, unless otherwise expressly stated, is licensed under a Creative Commons Attribution 4.0 International License.