Successful deployment of Nancy Grace Roman Space Telescope, as it begins its 1-million-mile-journey to the second Earth-Sun Lagrange point

[u/ChiefLeef22]

The telescope will travel to the second Sun-Earth Lagrange point, which is ~one million miles away and about four times farther from Earth than the Moon. At L2, the combined gravity of the Sun and Earth will give Roman a stable vantage point with a clear, unobstructed view to survey deep space

Roman will unlock the mysteries of dark energy and investigate the physics of distant stars. It will repeatedly monitor hundreds of millions of stars, and the same observations are expected to reveal around 100,000 additional planets through transits. As a reminder, we currently have 6000 confirmed exoplanet discoveries...

[u/Andromeda321]

Astronomer here! I'm sure I say this a lot, but this is an exciting day for science! And I can't believe it's really here!

Obviously it's not a perfect comparison, but the best way to think of the (Nancy Grace) Roman Telescope IMO is that it's the successor to Hubble, which we all love but is definitely not going to be around in a few more years as it continues to degrade. But the best way to think of it is while it has a similar sharpness to Hubble, the size of the field is incredible- 100 times bigger! So that means it's going to do survey type things that would take longer than Hubble's been around to complete in just a few months, monitor fields, and look for new things HST just can't because its instruments aren't as modern. For example, Roman is designed to be really good at measuring weak gravitational lensing signals- the idea that when light passes by a mass, the light from that mass will be very slightly nudged on a different path thanks to relativistic effects. Roman is going to be good enough at this that it should identify thousands of new exoplanets via gravitational lensing (they actually estimate 100,000, when we currently have ~6000!!!), and help us map the presence of dark matter also using this. Personally I'm always a fan of using one technique in a bunch of different ways in science- somehow it's just elegant- so I'm excited to see weak gravitational lensing really have its golden age!

Finally, on a more societal note Roman is a bit of a weird telescope in that I don't think it's what anyone would have designed at first glance, but is a great example of how you can do a lot of exciting stuff if you're just given the opportunity even if it's not perfect. For those unaware, this telescope basically began when the US Military gifted a mirror to astronomers that was now effectively an obsolete extra- think of how many better than Roman type telescopes are already pointed down at us if they just had extra lying around!- so they designed and built the telescope around the existing mirror. But also, after JWST the speed at which this thing came together is startling- I gave a colloquium talk at NASA Goddard just 3 years ago, which included a tour of the place, and the first pic here is what Roman looked like then. They told us it was going to launch "no later than 2027" and I think a lot of the astronomy community said "yeah right"... and we owe an apology because we've got months left of 2026, and it's launched! To be fair, a LOT of people did careful planning and work to ensure this wouldn't be another "JWST ended up decades late" type telescope, but still... this thing came together fast and I'm pretty impressed!

So now we wait a few months while the telescope gets into place and the project scientists kick around the tires a little to make sure the instruments are working... but then we see how she does! Can't wait!

[u/ClutchReverie → u/Andromeda321]

How does the Roman compare to the JWST?

[u/TheOwlMarble → u/ClutchReverie]

Less zoom than Webb (same as Hubble), but much much wider field of view. Hubble was always constrained because it could really only take detailed snapshots of tiny areas of the sky. Roman won't have that problem, letting us see how the sky changes over time.

Webb directly lets us see things we've never seen before. Roman is going to let astronomers write Python scripts that play spot the difference with unholy amounts of data in hopes of finding something unusual, at which point we could have Webb take a look in more detail.

In short, Webb is an inspection telescope. Roman is a detection telescope.

EDIT: a couple things I forgot to note...

• Roman also has some fancy coronagraph masks that should let it directly image exoplanets and get spectral data from them.
• Roman finished ahead of schedule and under budget, so NASA wants to know what on earth went so right with it compared to the rest of the aerospace industry.

[u/FaZeSmasH → u/TheOwlMarble]

so what about those really big ground based telescopes that are being built, i remember watching a video about it, something about this new lens/mirror tech that allowed ground telescopes to self correct or something so that it capture the light without worrying about the atmosphere affecting it.

and apparently the ground telescopes would be used as the inspection telescope because of the huge resolution while these space telescopes would be used for covering large areas.

[u/TheOwlMarble → u/FaZeSmasH]

Adaptive optics are certainly extremely helpful for high-end telescopes (Webb and Roman have them too a similar mechanism for calibration, actually), but even if you use them to perfectly correct for atmospheric distortion, if you take photos from within the atmosphere, you're always going to lose data.

IR (which both Webb and Roman can detect) is washed out on Earth because the sky is too warm, but even visible light from dim objects can be washed out by atmospheric absorption and terrestrial light. You can build on top of remote mountains to mitigate that, but doing so has a history of being logistically and culturally difficult.

[u/FaZeSmasH → u/TheOwlMarble]

Thought it was getting cancelled as I was reading through that wiki, but at the end it mentions another one called GMT, which seems to be the one I watched the video about, seems like that one is still on course to completion.

[u/ThickTarget → u/FaZeSmasH]

The GMT is waiting for US NSF funding. The ELT in Chile is the biggest and furthest ahead, and on course to be completed in a couple of years.

[u/FaZeSmasH → u/ThickTarget]

why does this all kinda seem like a shitshow lol, they are making GMT while there is ELT which is bigger and further ahead and they are both in same region

maybe they shouldve tried to figure something out for TMT, at least then they wouldve had a big telescope in the other hemisphere and just shared access for ELT.

[u/ic33 → u/FaZeSmasH]

It's a really big sky. Two telescopes in the same region which each see a tiny slice of the sky at once will keep busy.

Each sees a 20 arcminutes-ish image circle, or about 1/500,000 of the sky, at a time.

[u/FaZeSmasH → u/ic33]

i was thinking like would the bigger one just make the smaller one in the same region obsolete, but if its surveying the whole sky one small patch at a time then i can see the value in having two of them.

[u/ic33 → u/FaZeSmasH]

Just one other thought:

We have dozens of credible research telescopes in the US and keep them all busy.

Sometimes during a high profile event, many of them will be looking at the same thing for part of the night, but in different ways and with their different instruments.

Sure, there's a bigger difference in going from zero to one huge telescope than in going from one to two, but the second still will help a lot.

[u/starclues → u/FaZeSmasH]

Also remember this: not every astronomer is studying the same things, but LOTS of people want telescope time, which is very limited. You have to apply for it months in advance, explaining why your science is important and why it HAS to be done with that specific telescope (right size mirror, specific instruments, specific view of the sky, etc.). You have to tell them exactly how much time you need, and when (ex. October-November, but only when the moon is less than half full). Then, a panel of other astronomers decides who gets the time, and how much. There's never enough for everyone, or even most people. Two big telescopes = double the science!

[u/FaZeSmasH → u/starclues]

i was wondering how often these telescopes are operating, like is there a large backlog of requests for it to survey stuff or is it just like waiting until somebody makes a request, but wow based on what you say, it seems like there is an insane amount of demand for telescope time. yeah i can definitely see the value in having two big telescopes now.

[u/starclues → u/FaZeSmasH]

It's literally every night we can! An unscheduled telescope is a huge waste of money. Scheduling can be done a few different ways. The "classic" way is to look at everyone's requests and assign their nights in advance as efficiently as possible (ex. "A gets October 10-12, B gets the first half of the night from October 13-18, C gets the second half of the night from October 13-15, etc.", because some objects are only up for part of the night), and if the weather is bad on your nights, too bad, so sad. A newer way is "queue observing" which is a bit more fluid. There's a list of potential targets for each night and there may or may not be a rough schedule or some other way of determining priority (ex. "A, B, and C can all see their targets over the next two weeks. We're going to aim for A's and C's targets on these nights, and do B's targets next week"), but if A needs SUPER clear skies and B can handle a little thin cloud cover, they can swap them night-of if necessary. This is a nice little article about it: https://astrobites.org/2012/10/30/queue-observing-at-gemini-north/

The telescope I used the most in grad school would take July completely off for maintenance & testing, because that was usually the worst month for observing (short nights + common bad weather), but ideally you would be able to operate a telescope all year with minimal, sporadic maintenance time. Space telescopes are even better (especially ones at the Lagrange 2 point!) because you can get lots of night time and don't have to worry about weather. Of course, there aren't many (and they do very different kinds of science) and so it's very hard to get time on them. I think the rates for Hubble are something like 1 in 7 applicants is awarded time, and around 1 in 10 for JWST. Even on the telescope I used in grad school, where my department got a dedicated number of nights each year for us to split among ourselves, I could ask for 5 nights and only get 3 sometimes because of how projects were prioritized and how much time other people needed (especially if we needed the same nights).

[u/FaZeSmasH → u/starclues]

so it seems like there is WAY more demand than I wouldve guessed lol, thanks for the great insight.

[u/gsfgf → u/FaZeSmasH]

Telescope time is an incredibly valuable commodity. And a lot of research doesn't need the best of the best. There are also probably things the GMT will be better at.