4 ms·
We're looking at a system of stars and talking about accelerations below one nanometer per second squared? Really...?
by bjornsing 3y ago
We're looking at a system of stars and talking about accelerations below one nanometer per second squared? Really...?
- ta8645 3y agoIt says "unbelievable", right in the title.
- taneq 3y agoOver millions of years and distances of light years it all adds up.
- Someone 3y agoThat is irrelevant for discussing how amazing it is that we (think we) can measure such quantities. They didn’t observe over millions of years.
- EspressoGPT 3y agoYou just end up with very small numbers (acceleration) when you divide trivial numbers (distance) by very large numbers (orbital period).
- mr_mitm 3y agoYou even divide it by a large number squared.
- Someone 3y agoThat makes me think “could easily be a numerical issue with precision or accuracy of the software used”. I couldn’t find the software, so I couldn’t check a bit deeper.
- topspin 3y agoBoth the data and the code (Python) is here: https://zenodo.org/record/8065875 https://zenodo.org/record/8065875 That link came from the paper. Zenodo.org is a open science site curated by NASA. The analysis is interesting. He is using Gaia space observatory data to identify "nearby" binary systems, filtering out those with a high likelihood of being compromised by additional bodies in the system, and those for which the bodies have poor mass estimates, then measuring the orbits of the remaining 26k systems that can be confidently projected to three dimensions and aren't too eccentric, etc. His results are that below some small level of gravitational acceleration (the stars are far apart with long orbital periods,) the orbits predictably deviate from Newtonian gravity, and that due to the small size of binary systems Dark Matter cannot be a factor. It's a Nobel prize winner if correct. Good old fashioned falsifiable Science: future data sets and peer review of the work will tell us. Too bad Gaia runs out of fuel in two years. The longer the data set the more confidence can be achieved in this sort of work. It's interesting that only the most recent of the so far three data sets from Gaia provides the data necessary (tangential and radial velocity,) to do this.
- lou1306 3y ago> curated by NASA. Er, it's actually maintained by CERN and funded by the European Union. NASA does somehow participate in it as part of its "Transform to Open Science" initiative.
- V1ndaar 3y ago> Zenodo.org is a open science site curated by NASA. No offense, but Zenodo is a CERN project. [0] [0]: https://about.zenodo.org/ https://about.zenodo.org/
- topspin 3y agoOk. I was mislead by this, which appears as the first element of a carousel every time you load the Zenodo landing page: "Transform to OPen Science (TOPS) is a $40 million, 5-year mission, led by NASA's Science Mission Directorate's Open-Source Science initiative. Within the TOPS mission, NASA is designating 2023 as the Year Of Open Science, a community initiative to spark change and inspire open science... Curated by: nasatransformtoopen"
- sebzim4500 3y agoDo you know if Euclid will be able to collect this data after Gaia dies?
- topspin 3y agoGood question. I think perhaps not. This work is based on the data Gaia delivered in its most recent data release; the third so far. Only that release has provided both tangential and radial velocity of stars, which are crucial figures to compute the orbits of the binaries. This was done by correlating data collected simultaneously from the three instruments onboard Gaia. Does Euclid have the same three instruments or their moral equivalent? Will they operate Euclid such that they'll be producing similar data? I don't know. Even if there are equivalent capabilities, it's a different instrument, so the data will not simply slot in as the next tranche of observations.
- philsnow 3y ago
- Tuna-Fish 3y agoReally. The study is looking at wide binaries, where stars are in very far orbits around each other, moving very slowly, but still gravitationally bound. For example, the closest (non-sun) star to Earth, Proxima Centauri, orbits Alpha Centauri A and B with a semi-major axis of ~8700AU, or ~0.14 light years. It's orbital period is more than half a million years, it's orbital speed is ~500m/s, and the gravitational acceleration that keeps it in orbit is just 0.17nm/s². That 0.17nm/s² is tiny, but it really adds up over half a million years.
- bjornsing 3y ago> That 0.17nm/s² is tiny, but it really adds up over half a million years. True. But we don’t have half a million years to make an observation. 0.17nm/s² over a year only adds up to a displacement of 85 km, and now we’re looking for a relatively small discrepancy in this expected movement? The radius of the sun is about 696000 km, for comparison.
- JPLeRouzic 3y agoI know nothing about physics, but just finding that an orbit isn't that if a body has an elliptic orbit means it is accelerating and decelerating constantly depending where it is in the orbit? I guess it's quite easy to measure periapsis and apoapsis even for stars or planets that have a nearly circular orbit.
- rightbyte 3y agoI got this feeling alot of physicists are trying to get grant money from massaging noise.
- cdelsolar 3y agoThat’s a pretty cynical way to look at it. If you look at LIGO, that thing is detecting changes in length of 1/1000th the width of a proton. The actual data looks like noise. But it’s not noise. GPS data looks like noise in raw form and yet it gets millions of people to their destinations daily.