semaphoreP (u/semaphoreP)

semaphoreP commented on To my surprise and elation, the Webb Space Telescope is going to work arstechnica.com/science/2... · Posted by u/wglb

ajuc · 4 years ago

Is there any sense in using internet providing sattelites for astronomy? Like if starlink published it's noise data from all sattelites in realtime could it be used as one huge radiotelescope?

semaphoreP · 4 years ago

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 commented on To my surprise and elation, the Webb Space Telescope is going to work arstechnica.com/science/2... · Posted by u/wglb

adhesive_wombat · 4 years ago

Since the JWST design started, there's been a revolution in the "easiness" of launches.

I wonder if a future evolution of space telescopes will be some kind of interferometric (obviously extremely hard for IR or visible light, but easier for radio and microwaves) swarm of cheap semi-disposible telescopes than one enormous one.

Then you can add to the swarm, upgrade elements, and retire failed elements without having to eat a multi-billion helping of humble pie.

And rather than have a fearsomely complex integrated sunshield, you could have a similar swarm of simpler satellites that provide a large cool area at L2, and then the observers just need to handle their own heat.

I suppose this could be described as microservices...in spaaaaace. Draw what parallels you will from that!

semaphoreP · 4 years ago

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 commented on First Ever Image of a Multi-Planet System Around a Sun-Like Star (2020) eso.org/public/news/eso20... · Posted by u/echelon

GPerson · 4 years ago

Naive question here, but how much more resolution can we ever expect to get out of pictures like these? If it gets 100 times better will we be able see what the planets look like?

semaphoreP · 4 years ago

Note that in these images, the planets are unresolved. They are point sources. Point sources span multiple pixels due to the sampling theorem.

semaphoreP commented on First Ever Image of a Multi-Planet System Around a Sun-Like Star (2020) eso.org/public/news/eso20... · Posted by u/echelon

sam-2727 · 4 years ago

First round has already been awarded: https://www.stsci.edu/jwst/science-execution/approved-progra...

semaphoreP · 4 years ago

And this is the program that will study this system: https://www.stsci.edu/jwst/science-execution/program-informa...

semaphoreP commented on Supersharp Images from New VLT Adaptive Optics eso.org/public/news/eso18... · Posted by u/sohkamyung

welterde · 7 years ago

> In the visible, ground-based can't match space observatories (in the visible, the atmospheric turbulence is way harder to correct for).

The image this article is about is mostly in the optical (MUSE only goes from 465nm to 930nm; and the synthetic filters used in the MUSE image [4] seem to be quite close to the used HST filters).

> And really only in the near-infrared, as past 5 microns, we can't really see through the atmosphere.

Not quite true [1] (at least if only considering absorption), it's just that the background becomes more and more of a problem (both continuum and narrow emission lines), and one has less nicely defined windows of transmission and lots of strongly variable absorption lines (picking dry places for the telescopes and selecting nights with low water vapour column densities helps). At the VLT for example there is VISIR [2], which does mid-IR imaging and spectroscopy.

Of course the sensitivty from the ground is much lower than from space or somewhere in between (for example there is SOFIA [3] which is a 2.5m telescope on an airplance) and some bands of interest are indeed absorbed. But there are indeed projects that involve mid-IR observations that can be done from the ground.

[1] https://www.gemini.edu/sciops/telescopes-and-sites/observing... [2] http://www.eso.org/sci/facilities/paranal/instruments/visir/... [3] https://en.wikipedia.org/wiki/Stratospheric_Observatory_for_... [4] https://www.eso.org/public/unitedkingdom/images/eso1824c/

semaphoreP · 7 years ago

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 commented on Supersharp Images from New VLT Adaptive Optics eso.org/public/news/eso18... · Posted by u/sohkamyung

appleflaxen · 7 years ago

the article makes it sound like the approach is so effective that it makes space-based telescopes unnecessary.

is that true? does this mean that we should simply use ground-based 'scopes with adaptive optics?

semaphoreP · 7 years ago

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 commented on NASA finds a large amount of water in an exoplanet's atmosphere nasa.gov/feature/goddard/... · Posted by u/dnetesn

ianai · 8 years ago

That makes me think it’s a pretty substantive amount of water. If we’re getting 3x the spike we see for a planet in our own solar system in a planet lys away then actual content should be much more (due to signal/noise? Just guessing though)

semaphoreP · 8 years ago

It's not the absolute value of the signal. What they're measuring the amount of water compared to hydrogen.

semaphoreP commented on NASA finds a large amount of water in an exoplanet's atmosphere nasa.gov/feature/goddard/... · Posted by u/dnetesn

elihu · 8 years ago

> In fact, the planet, known as WASP-39b, has three times as much water as Saturn does.

Is that a lot?

semaphoreP · 8 years ago

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 commented on NASA finds a large amount of water in an exoplanet's atmosphere nasa.gov/feature/goddard/... · Posted by u/dnetesn

aphextron · 8 years ago

Incredibly exciting that these techniques for exoplanet spectroscopy have come so far so quickly. I have full faith that we will discover indirect chemical evidence of extraterrestrial life within the next 10 years. Once JWST [0] comes online it's going to be just a matter of time.

https://en.wikipedia.org/wiki/James_Webb_Space_Telescope [0]

semaphoreP · 8 years ago

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 commented on ESO Telescopes Observe First Light from Gravitational Wave Source eso.org/public/news/eso17... · Posted by u/acqq

hliyan · 8 years ago

To put this in perspective:

Since the first hominids looked up at the stars, till literally yesterday, mankind had only one fundamental force to observe the universe with: electromagnetic waves, be it light, radio waves or infrared. From today, we have two. The other two remaining fundamental forces do not operate at astronomical scales.

Of course, we had LIGO before yesterday, but for me, the confirmation through electromagnetic wave observations is key. This is an historic day!

semaphoreP · 8 years ago

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...