RedOrGreen

7 ms·

1.
by RedOrGreen 2y ago
Yes, in a way. Think of a single dish radio telescope as a one-pixel camera, where measuring the emission intensity at each point in the sky lets you build up a map. Typically, this is done with high resolution on the frequency axis, which
2.
by RedOrGreen 3y ago
Very nice, even with no planes overhead. But it looks like the map orientation is reversed (off by 180 degrees)? Real bug, or just me?
3.
by RedOrGreen 3y ago
Oof, yes, I didn't even mention corporate compliance.
4.
by RedOrGreen 3y ago
Paraphrasing: "If you don't want to, don't sideload apps, no one is forcing you to" - do people really not see the problem? It's not that technically unsophisticated users will want to sideload apps. They don&#x27
5.
by RedOrGreen 5y ago
I came to this thread a bit too late, but if you're interested in the actual signal that Stella found, take a look at the spectrum vs time on the NASA release [1] - third plot on the page, with a convenient slider that lets you flip ba
6.
by RedOrGreen 6y ago
Allow me to gently contradict the previous responders. The community of radio astronomers is feeling the loss of Arecibo very keenly. I've mentioned this in a previous comment [1] so I won't rehash it again, but here [2] is a stat
7.
by RedOrGreen 6y ago
I'm too sad today to engage with the discussion here, but I'll just mention, for those of you who think that Arecibo has either "outlived its usefulness" or been supplanted by FAST in China: Here's Arecibo on the co
8.
by RedOrGreen 6y ago
I'm too sad today to engage with this, but you're simply wrong about Arecibo "having done all the useful things it could do ages ago, and not finding anything new". Here, for example, is Arecibo on the cover of Nature, i
9.
by RedOrGreen 6y ago
> If the full hundred hours was such a huge risk, why not take, like, 5-10 photos first to see if you get much of anything? Seems like they would have been able to know pretty early on whether it was going to be worth it. This has been
10.
by RedOrGreen 6y ago
HST is in a 96-minute orbit, up to half of which is blocked by the Earth, depending on where in the sky you point it. Getting time on it is an extremely competitive process - the recent cycle had over a thousand proposals, requesting over
11.
by RedOrGreen 7y ago
This is a comparison of images, not just catalogs of sources in images. If you look at the image in the linked article, you can easily spot one of the stars that has "gone missing". Looking at the brightness of the source that wen
12.
by RedOrGreen 7y ago
Sure, that's an excellent point. In case you read late replies: we recognize this, and parameterize the burst energy [1] by a beaming scale factor, \Delta\Omega/4\pi. (It still drops off as the inverse square, though, as long as y
13.
by RedOrGreen 7y ago
We measure the energy of signals received at our radio telescopes - our units are Janskys, which correspond to 10^-26 watts per square metre per hertz of bandwidth, and we can calibrate our telescopes using noise diodes or known sources in
14.
by RedOrGreen 7y ago
Yes, we're not going to do optical VLBI soon, but the reason is deeper... I just wrote out a long comment [1]. [1] https://news.ycombinator.com/item?id=19674563
15.
by RedOrGreen 7y ago
Calling it a "really fast camera" elides much of the actual difficulty. We're trying to tag individual wavefronts of light at different telescopes, record them, and then play them back at a central "correlator" with
16.
by RedOrGreen 7y ago
(I haven't watched the video, but I do have professional expertise on this topic.) With interferometry, you're getting an incomplete sampling of the Fourier transform of the sky image, and if you just invert the samples, you get w
17.
by RedOrGreen 8y ago
For pulses or bursts of emission, we like compact objects, just from light-travel-time arguments. I would say that the leading models involve very young, highly magnetic neutron stars ("magnetars"), either embedded in their birth
18.
by RedOrGreen 8y ago
It's a full interferometer, although for the pulsar and FRB modes, they are tiling the field of view with many, many phased array beams. (Yes, the computation requirements are horrendous.)
19.
by RedOrGreen 8y ago
Would you care to elaborate on what you find objectionable about Face ID? Just like the fingerprint reader, all data is stored on the device secure enclave, and does not leave the phone. And it's been pretty much fast enough for me sin
20.
by RedOrGreen 8y ago
Yes, the authors discuss the implications for scalar-tensor theories, and it doesn't look great for many of them. The Nature News and Views article by Clifford Will [1] offers a decent overview. [1] https://www.nature.com&#x
21.
by RedOrGreen 8y ago
We can do even better some of the time - for example, we can get to ~few nanosecond timing precision for pulsars like J1909-3744 [1], which is equivalent to measuring (changes in) the path length to that pulsar to a few meters or better. [1
22.
by RedOrGreen 9y ago
I'm too close to this topic for a chatty comment, but I'll just point to this IAU meeting: "Pulsar Astrophysics: The Next 50 years"[1]. It was held this September at Jodrell Bank, which has always had deep involvement wi
23.
by RedOrGreen 9y ago
> I hold out hope the NS-NS rumor is true, that paper is just taking a bit longer to prepare. Mark October 16th on your calendar.
24.
by RedOrGreen 9y ago
I guess this is cool, but not really that novel a result (and yeah, it's an ATel, not a paper yet, although that's just a matter of time). We've seen similar burst storms from this FRB source before, which is what allowed us
25.
by RedOrGreen 11y ago
And they haven't even tracked down the location of the source as well as it sounds. They detected a burst, and found a fading radio source in that field of view, but there's a decent chance (<6% or <0.1%, depending on which