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semaphoreP

294 karma · joined August 21, 2014

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semaphoreP··on To my surprise and elation, the Webb Space Telescope is going to work
Probably pretty difficult to find too many compelling cases. The bands starlink transmits in are designated communication bands, so interference from other satellites is going to be so high that it will drown out any signals. There are astronomers working on removing this foreground, but it's really difficult! It's actually becoming quite a problem in radio astronomy with the amount of the electromagnetic spectrum that is quiet enough for science.
semaphoreP··on To my surprise and elation, the Webb Space Telescope is going to work
Astronomer here, we are thinking about doing interferometers in space[1,2], but it won't be a catch-all for everything. One reason is that the instrumentation is equally as important as the telescope optics itself, and it's non-trivial to have your swarm of satellites both collect light, but also do science experiments with the light. One thing we are thinking of is to fly more proto-typing missions to get the technology readiness of various components to mature stages before assembling it all together for the real thing (I would say we did not do this as well for JWST).

[1]: https://www.life-space-mission.com/ [2]: https://lisa.nasa.gov/

semaphoreP··on First Ever Image of a Multi-Planet System Around a Sun-Like Star (2020)
Note that in these images, the planets are unresolved. They are point sources. Point sources span multiple pixels due to the sampling theorem.
semaphoreP··on First Ever Image of a Multi-Planet System Around a Sun-Like Star (2020)
And this is the program that will study this system: https://www.stsci.edu/jwst/science-execution/program-informa...
semaphoreP··on Supersharp Images from New VLT Adaptive Optics
Ah my bad, I mean that in the visible, you can't reach the diffraction limit with AO like you can in the near infrared. Certainly impressive matching HST from the ground.

I don't think past 5 microns there's been a lot of science done from the ground (not counting SOFIA). Practically, I think everyone is waiting for JWST. A lot of the interesting molecular lines also get absorbed by the Earth's atmosphere.

semaphoreP··on Supersharp Images from New VLT Adaptive Optics
Adaptive optics is really only effective in the infrared. And really only in the near-infrared, as past 5 microns, we can't really see through the atmosphere. In the visible, ground-based can't match space observatories (in the visible, the atmospheric turbulence is way harder to correct for).
semaphoreP··on NASA finds a large amount of water in an exoplanet's atmosphere
It's not the absolute value of the signal. What they're measuring the amount of water compared to hydrogen.
semaphoreP··on NASA finds a large amount of water in an exoplanet's atmosphere
It's hard to measure absolute water abundances (it requires a lot of assumptions and extrapolating). This is a relative comparison of atmospheric water. We don't have relative water abundances for a lot of planets, so it's on the higher end, but we don't really know (maybe some other planets' water are hidden behind clouds).
semaphoreP··on NASA finds a large amount of water in an exoplanet's atmosphere
It will be very tough with JWST. Many of the biosignatures are small features, and not so easily detected. There's only a handful of planets for which this might be close to possible.
semaphoreP··on ESO Telescopes Observe First Light from Gravitational Wave Source
We've also been observing the universe using neutrinos (generated by the weak force). In fact, there have even been one neutrino event linked to a possible astrophysical source[1], but with less certainty than this gravitational wave/EM detection.

[1]: https://www.nasa.gov/feature/goddard/2016/nasas-fermi-telesc...

semaphoreP··on ESO Telescopes Observe First Light from Gravitational Wave Source
Quite possibly I think. This is both confirmation that neutron star mergers do indeed exist and create kilonova, and the first detection of an astronomical event with both gravitational waves and light. Nobel prize is only limited to three people though, so it's unclear who they would give it to, given there are thousands of people that contributed to this.
semaphoreP··on ESO Telescopes Observe First Light from Gravitational Wave Source
Not involved in this, I'm guessing this is how it goes: there are algorithms that automatically register the image that was just taken, diff it with a reference image of the sky from before, and if there's a significant difference that passes some false positive tests, then there's some notification for human intervention.

Indeed there could be events we are missing right now. Astronomers are building instruments that have larger fields of view (e.g., LSST), so that they can scan the sky ever few days.

semaphoreP··on Four Earth-sized planets detected orbiting the nearest sun-like star
Actually this star is not in the Kepler Field, and it is also too bright for Kepler. Even most ground based telescopes looking for transits probably haven't bothered looking at it, due to its brightness.
semaphoreP··on Four Earth-sized planets detected orbiting the nearest sun-like star
Measuring the star wobble (i.e. doppler shift) doesn't give inclinations.
semaphoreP··on Four Earth-sized planets detected orbiting the nearest sun-like star
I guess you're right. I know there aren't any observed transits, but I also don't know what the current constraints from monitoring the star's brightness for transit is (the star is actually so bright that it becomes hard to monitor for planet transits).

However, we have a good prior on the inclination of these planets, because we know the inclination of the dust disk around the star (https://www.scientificamerican.com/article/tau-ceti-s-dust-b...), and it is likely the planets are at a similar inclination. Because the disk isn't edge on, the planets also likely aren't, and won't transit.

semaphoreP··on Four Earth-sized planets detected orbiting the nearest sun-like star
This title is a bit imprecise. They detected four planets with lower bound on their masses to be down to 1.7 Earth masses. Because these planets don't transit, there are no direct measurements from their radius. They can use mass-radius relations to infer the radius of these planets, but the key finding is their masses (actually lower bounds on their masses).
semaphoreP··on Windows Subsystem for Linux is out of beta
I recall there were issues if you tried to modify those files in Windows. Maybe they've fixed that in recent updates, but my impression was that while I could see the files, I shouldn't be touching them.
semaphoreP··on Windows Subsystem for Linux is out of beta
It works great for me. Like others have mentioned, it's not an emulator, so I don't feel sandboxed using it. The main downside is one of the caveats they mention: "Linux files are NOT accessible from Windows." Hopefully they can fix this in the future.
semaphoreP··on Thanks to Venmo, We Now All Know How Cheap Our Friends Are
Yeah, I only use Venmo when I'm on the coasts. None of my friends in the Midwest have it, and maybe I'm just used to it, but it just felt inefficient to split the bill and wait for each person to pay with their own credit card rather than having one person pay and Venmo them back.
semaphoreP··on Betelgeuse captured by ALMA
Optical interferometers have resolved Betelgeuse down to 9 milliarcseconds (4 x 10^-8 radians), so this isn't even the highest resolution image yet of this star[1].

[1] http://blogs.discovermagazine.com/badastronomy/2010/01/12/sp...

semaphoreP··on Betelgeuse captured by ALMA
JWST, like ground-based telescopes now, will be able to separate the light from massive Jupiter-like exoplanets from the light of their host stars. But it won't be able to see things at a resolution like this image of Betelguse (so no surfaces of planets... that's quite a long time away).
semaphoreP··on Betelgeuse captured by ALMA
The colors are only there to represent brightness, so the white spot is a brighter patch on the star (brighter because it's hotter).
semaphoreP··on How many floating-point numbers are in the interval [0,1]?
Or you can think of it as precision in the number of significant digits for a number. Each floating point number can only store a certain amount of significant digits. The fractional precision on each float is the same, but the absolute magnitude of the error in the float value increases as the value increases.
semaphoreP··on Seven earth-sized planets discovered circling a star 39 light years from Earth
It will depend on the size of the telescope, but for all practical purposes, these planets are too close to their star to see directly. A starshade will be good for Earth-like planets at Earth-like separations around Sun-like stars though.
semaphoreP··on Seven earth-sized planets discovered circling a star 39 light years from Earth
Don't know the number off the top of my head, but it should be considerably less. It should also be highly varying as some galaxies live in pretty densely packed environments (galaxy clusters), which some live in very open environments like our own galaxy.
semaphoreP··on Seven earth-sized planets discovered circling a star 39 light years from Earth
A Russian billionaire is trying: https://breakthroughinitiatives.org/Initiative/3
semaphoreP··on Seven earth-sized planets discovered circling a star 39 light years from Earth
It's almost all Hydrogen/Helium gas. Other larger atoms and molecules are known to exist in the interstellar medium, but it's primary gas.

Also, a good way to remember the density is ~1 Hydrogen atom per cm^3.

semaphoreP··on Seven earth-sized planets discovered circling a star 39 light years from Earth
Like others have pointed out, the combination of the planets being tidally locked so only one side gets sunlight and the strong X-ray radiation and flaring from the host star make it considerably un-Earth-like, and harder for life as we know it to develop.
semaphoreP··on Seven earth-sized planets discovered circling a star 39 light years from Earth
I don't think we know for sure, but it'd be hard to place another star in the system and have it a) not disrupt the planets and b) go unnoticed as the primary star is so faint.
semaphoreP··on Seven earth-sized planets discovered circling a star 39 light years from Earth
It'll be in the near-infrared, but the light won't be separated from the star. How they observe the atmosphere is that when the exoplanets transit, they block out different amounts of light at different wavelengths. From that, one can deduce an atmospheric spectrum.
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