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Giant, all-seeing telescope is set to revolutionize astronomy
- gnabgib 1y agoDiscussion a year ago (75 points, 22 comments) https://news.ycombinator.com/item?id=39927682 https://news.ycombinator.com/item?id=39927682
- taylorportman 1y agoThe mirror coating timelapse video is pretty awesome https://www.youtube.com/watch?v=Gg9UPS7ndRA https://www.youtube.com/watch?v=Gg9UPS7ndRA
- fastball 1y agoWhy is the substrate glass? Lack of reactivity? Ability to remove imperfections? As a layman with almost zero knowledge of telescope construction, I feel like a heavy amorphous solid would not be my first choice for the base layer underneath the reflective/mirror coating.
- minetest2048 1y agoIts not your normal soda-lime glass, its more of a glass-ceramic material that have very low coefficient of thermal expansion, something like zerodur: https://en.m.wikipedia.org/wiki/Zerodur https://en.m.wikipedia.org/wiki/Zerodur , which means it can keep its shape and focus even under varying temperature Interesting demo by Huygens Optics: https://youtu.be/qi8jmEbWsxU?si=rj0I3k-l74Xhg7vC https://youtu.be/qi8jmEbWsxU?si=rj0I3k-l74Xhg7vC
- perihelions 1y agoI think while the smaller mirror here is Zerodur, the larger one is just borosilicate, https://astro.arizona.edu/news/rubin-observatory-achieves-another-major-milestone-reflective-coating-84-meter-primarytertiary https://astro.arizona.edu/news/rubin-observatory-achieves-an...
- IAmBroom 1y agoThat would be an odd choice. A large glass mirror once cracked because they "only" allowed one year for it to cool. The second one was allotted three years.
- idontwantthis 1y agoHas this not been affected by USA science cuts?
- viraptor 1y agoIt's been over 10 years since they started. I don't know what the funding details are, but overall this is not really working on a scale that 5 months would change.
- hermitcrab 1y agoIt looks like the current administration may kill other projects mid-mission: "Among the other programs set to lose funding are a craft already on its way to rendezvous with an asteroid that's expected to pass close to Earth in 2029, and multiple efforts to map and explore the acidic clouds of Venus. Researchers worry that abandoning missions would mean investments made by earlier generations might be lost or forgotten." https://phys.org/news/2025-06-trump-dozens-nasa-missions-threatens.html https://phys.org/news/2025-06-trump-dozens-nasa-missions-thr... So I'm not sure any US government-funded science project is safe.
- IAmBroom 1y agoThe time the tree has spent growing is only loosely correlated with the time it takes to fell it.
- perihelions 1y agoNo, but its space-based counterpart was cancelled (the 2.4 meter wide-field survey telescope). https://en.wikipedia.org/wiki/Nancy_Grace_Roman_Space_Telescope#Funding_history_and_status https://en.wikipedia.org/wiki/Nancy_Grace_Roman_Space_Telesc...
- oldpersonintx2 1y ago[dead]
- zanecodes 1y ago
- walrus01 1y agoIs there a figure somewhere on how many TB of images this will produce per day when running in automated sky survey mode?
- Jgrubb 1y ago> The vast archive, growing by 20 terabytes each night, will after 1 year contain more optical astronomy data than that produced by all previous telescopes combined.
- 9dev 1y ago73 PB over the full runtime of the survey. That’s a nice new datacenter filled to the brim with images.
- jl6 1y agoProbably about 10 racks if using dense HDDs.
- jankeymeulen 1y agoStorage densities these days are kinda amazing, it's not that much of a datacenter. Assuming you chunk it with triple redundancy, that's 220k TB raw. 10k 22 TB disks, you put them in one of those 4U 50 disk storage pods. 200 pods, 10 of those in a rack with some space left for a switch and power, so that's only 20 racks.
- LiamPowell 1y agoOnly 50 disks? WD sells a 102 disk 4u box and Seagate sells a 106 disk one.
- ethan_smith 1y agoThe Rubin Observatory will generate approximately 20TB of raw image data per night, with an annual data production of about 15PB for the 10-year survey.
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- viraptor 1y agoQ for astronomy people: This is tracking the sky movement as it takes the pictures right? Also, with the atmosphere moving, is there a limit of how large the telescope can be and take photos from earth, before it can't get more quality?
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- ddahlen 1y agoThe atmosphere is always an issue, we can correct for many of the effects using adaptive optics, but there are always limits. The advantage you get from going bigger on the ground is that you are making a bigger "bucket" to put photons in. More photons = fainter objects are visible, this is the motivation for projects like: https://en.wikipedia.org/wiki/Extremely_Large_Telescope https://en.wikipedia.org/wiki/Extremely_Large_Telescope Typically for non-adaptive optics telescope the atmosphere will limit you to the scale of about an arcsecond. Meaning objects which take up less than an arcsecond of the sky will appear as points. Adaptive optics telescopes however have much better resolving power.
- joshvm 1y agoAt some point you'll be diffraction limited even at the scale of Earth. The larger your effective aperture, the better you can resolve. Adaptive optics helps get big telescopes closer to diffraction limited performance. That's the best you can do with a given optical system, barring some funky microscope setups. Trying to beat the diffraction limit has occupied a lot of very smart minds. https://en.m.wikipedia.org/wiki/Diffraction-limited_system https://en.m.wikipedia.org/wiki/Diffraction-limited_system Practically to go really big you need to use interferometry. There are radio experiments that can do this at Earth scale - the Event Horizon Telescope can image very small objects (black holes) by making simultaneous observations from all over the world. The telescopes point at the same place and use very very good timestamping. At the South Pole we have a hydrogen maser for that. Then all the data gets sent somewhere for correlation and a lot of processing. The analogy I like most is imagining you have a big mirror (Earth) but you've blacked out almost the entire surface except a few points where the telescopes are. Radio is particularly amenable to this because you can build big dishes more easily than for visible light, and the diffraction limit is lower because it's proportional to wavelength/aperture. So in addition to big dishes, you're observation wavelength is much much longer (mm vs nm). There's a log-log plot on that wiki page which is quite difficult to read, but the important point is that radio is all the way at the top and the best we have is the VLBA. Visible interferometry is much harder...!
- abound 1y agoIf you're just here looking at the HN comments: check out the article. It's really well-written and has a bunch of nice visualizations if you like astronomy things.
- vincnetas 1y agoThe last picture made a bit sad and feel pity for astronomers : "Satellite swarms mar Rubin’s pristine view" I imagine these are like mosquitos in photoshoot where you try to capture a super hot model.
- BotJunkie 1y agoI visited there a few months ago, and satellites are not a big concern for Rubin in particular. It will visit every part of the sky over 800 times and add all those images together, and since the satellite trails won't cover the same things every time the overall impact on data is minimal. They estimate less than 1%, so the plan is to just run the survey for 1% longer.
- soco 1y agoI guess Rubin will be the last telescope built on the Earth surface right? Little use to have stronger eyes only to have them blinded...
- perilunar 1y agoBuilding telescopes in high-earth or solar orbit has other advantages too: you can make them much bigger, and don't have to account for atmospheric distortions, etc. The downside is cost of launching them, but the same SpaceX that's 'ruining' the images is also making it much cheaper to launch them into space.
- ddahlen 1y agoI have been working in astronomy for a few years now and I recently have gone back to school for a PhD in orbital dynamics. Rubin is going to make a big difference in our knowledge of the asteroid belt, it will likely more than triple the size of our known catalog of asteroids. Its actually somewhat difficult to know exactly how much it will increase our knowledge. The bigger the telescope we build, the fainter the asteroids we see. The difficulty is that while we can make a pretty educated guess as to how many smaller ones there are, this is such a jump that the error bars on that guess is quite large. I am quite excited to see how the catalog of asteroids changes, I expect we will be finding a LOT of smaller rocks near the Earth. Asteroids have a broad range of albedo, basically the brightness of the surface can vary from the blackest coal (like 3-5% of the light reflecting) to concrete (up to about 50%). All visible range telescopes will be susceptible to a bias in their observations, since a big black rock will be as bright as a smaller paler rock. We know that the asteroid belt favors the dark material. In a couple of years, the Near Earth Object Surveyor (NEOS) space telescope will launch. NEOS is an IR telescope and will not have the same albedo bias. The trade off is that it will measure the black body radiation, meaning asteroids have to be nearer the sun. Broadly these are very complementary surveys, Rubin will be fantastic for filling out the main belt, and NEO Surveyor will do a great job on our neighborhood. Source: I worked at Caltech on NEOS, I wrote the code they use to predict known asteroid orbits: https://github.com/dahlend/kete https://github.com/dahlend/kete Edit: I failed to mention that Rubin is a big deal for a lot of time-domain astronomy, I'm just being selfish talking about asteroids only.
- sdoering 1y agoI love your selfishness. Learned a lot, while sipping my second coffee and eating my breakfast before diving into work. Thanks kind stranger. I loved astronomy as a kid and the town I grew up in has a "solar system way", basically a long street where a kind fellow (who in his freetime taught astronomy to nerds like myself and had built his own oberservatory in his backyard) had - with the blessing of the city - built a scale model of the solar system on a length of about 1.5 kilometers (a bit less than a mile). I always found it fascinating when walking "through our solar system" with about 13 times the speed of light (normal walking translated into the distance at that scale) how veeeeeeeeeeery far apart things get in the solar system. Sadly only in German: https://www.muenchberg.de/erleben/tourismus/tourismus-und-freizeit/tourismus-und-freizeit/planeten-wanderweg/ https://www.muenchberg.de/erleben/tourismus/tourismus-und-fr... Edit: And yes - Pluto is still in there. It was built before the demotion - and they kept him in when doing the renovation last year (I was not in my home town since then - I so need to see it, when I visit the next time).
- jl6 1y agoThe starlink streak issue is real, but isn’t this type of survey uniquely well suited to compensate for it, because it takes repeated exposures in relatively quick succession, meaning the odds of a given pixel being obscured by a streak in successive images get very low? Still not ideal but seems manageable compared to other telescopes running non-automated surveys.
- BurningFrog 1y agoAs I understand it, the orbit for each satellite is very precisely known. Which I think/hope means you can remove/identify known satellites in the images mechanically.
- Kye 1y agoThat doesn't help if the distant light you're interested in was blocked. It's not an aesthetic concern. You can't remove the satellite and put the interesting light back. It's just gone. That could be a supernova or some as yet unidentified phenomena that only exists for a moment.
- BurningFrog 1y agoIt's gone for the very brief moment the satellite blocks it. The article says Rubin pictures are 30 seconds exposure, which should leave at least 29* seconds of data. Of course, there will unavoidably be some degradation. * This number is backed solely by my personal intuition
- prpl 1y agoThat’s not how it works, especially for Rubin. In practice what it means is much lower statistics on streaky data over time. The streaks are not point sources either, so they have a disproportionate impact. You can deal with this through survey strategy to some extent. You can almost think of this as something similar to vignetting in the final data products. Certain areas will have lower statistics and especially lower temporal resolution based on the season depending on where they are relative to the horizon near twilight. So, a single image could be lost, but there is supposed to be 1000 or so good images of that area over the survey, about 100 a year. With the satellites, potentially you’ve now lost 3–8 images a year for any given section of the sky (probably more near the equatorial plane), lowering your statistics of the entire survey 1-10%, depending on the declination. I’m spitballing numbers, there are actual papers you could read though. Rubin is “wider, deeper, faster”. This reduces all of those dimensions to some extent, but especially the deeper.
- Kye 1y agoThis sounds so cool. I sure hope this isn't one of the projects threatened by impending cuts to science funding.
- aragilar 1y agoI suspect the better question is "how badly affected are project science goals by the funding uncertainty". I'm not US-based, but from what I've heard no astro projects are unaffected.
- IAmBroom 1y agoHoly shazbot! I thought the author was being a bit hyperbolic about the "built for speed" part... "The test drive shows off just 20% of Rubin’s maximum speed. At full tilt, a runner wouldn’t be able to keep up. Presumably measured at the edge of the platform, but still... WOW!
- inasio 1y agoI see some parallels with magnetic resonance imaging. I worked on a project optimizing MRI scans a few years back. I remember the PI in the project essentially acknowledging that analyzing single MRI images is absolutely more art than science, but there's a ton of value in getting periodic MRIs (say yearly) and looking at the diffs. I imagine a lot of the value coming from Rubin will be due to this, as well as the reason it was built for speed.
- vivzkestrel 1y agofictional question: how much detail would we see if we could somehow make a telescope with a 1 million km diameter
- me_again 1y agoNot exactly the same, but https://en.wikipedia.org/wiki/Very-long-baseline_interferometry https://en.wikipedia.org/wiki/Very-long-baseline_interferome... is a technique used in radio astronomy which uses two receivers a long way apart and a very accurate clock to approximate having a radio telescope the size of the distance between them. By putting one receiver on a satellite, measurements have been made with a separation of 300,000km.
- asinno 1y agoI visited the cleanroom where they manufactured and assembled the lens and processing unit before shipping to Chile. world’s largest digital camera at 3200-megapixel image in a few seconds.
- kristianp 1y ago> alerts for each new “transient”—as many as 10 million every night How are astronomers going to deal with that many alerts?
- BotJunkie 1y agoThere are automated "alert brokers" that will filter these alerts to make them manageable- you can subscribe to phenomena that you're interested in and get only those alerts.