First Images From NASA's James Webb Space Telescope (space.com) 22
The first images from NASA's James Webb Space Telescope have been released, according to Space.com. Slashdot readers g01d4 and fahrbot-bot first shared the news. From the report: The main photo, which doesn't even hint at the power Webb will bring to the universe once it's fully operational, shows a star called HD 84406 and is only a portion of the mosaic taken over 25 hours beginning on Feb. 2, during the ongoing process to align the observatory's segmented mirror. "The entire Webb team is ecstatic at how well the first steps of taking images and aligning the telescope are proceeding," Marcia Rieke, principal investigator of the instrument that Webb relies on for the alignment procedure and an astronomer at the University of Arizona, said in a NASA statement.
JWST is now 48 days out from its Christmas Day launch and in the midst of a commissioning process expected to last about six months. The telescope spent the first month unfolding from its launch configuration and trekking out nearly 1 million miles (1.5 million kilometers) away from Earth. During the bulk of the remaining time, scientists are focusing on waking and calibrating the observatory's instruments and making the minute adjustments to the telescope's 18 golden mirror segments that are necessary for crisp, clear images of the deep universe. The process is going well, according to NASA.
Still, the telescope has a long way to go, as today's image of HD 84406 shows. [...] HD 84406 is in the constellation Ursa Major, or Big Bear, but is not visible from Earth without a telescope. But it was a perfect early target for Webb because its brightness is steady and the observatory can always spot it, so launch or deployment delays wouldn't affect the plan. Oddly, JWST won't be able to observe HD 84406 later in its tenure; once the telescope is focused, this star will be too bright to look at. Previously, JWST personnel have said that the telescope will be seeing fairly sharply by late April. In addition to the image of HD 84406, NASA also shared a "selfie" image, which Gizmodo and CNN decided to focus on in their reports.
JWST is now 48 days out from its Christmas Day launch and in the midst of a commissioning process expected to last about six months. The telescope spent the first month unfolding from its launch configuration and trekking out nearly 1 million miles (1.5 million kilometers) away from Earth. During the bulk of the remaining time, scientists are focusing on waking and calibrating the observatory's instruments and making the minute adjustments to the telescope's 18 golden mirror segments that are necessary for crisp, clear images of the deep universe. The process is going well, according to NASA.
Still, the telescope has a long way to go, as today's image of HD 84406 shows. [...] HD 84406 is in the constellation Ursa Major, or Big Bear, but is not visible from Earth without a telescope. But it was a perfect early target for Webb because its brightness is steady and the observatory can always spot it, so launch or deployment delays wouldn't affect the plan. Oddly, JWST won't be able to observe HD 84406 later in its tenure; once the telescope is focused, this star will be too bright to look at. Previously, JWST personnel have said that the telescope will be seeing fairly sharply by late April. In addition to the image of HD 84406, NASA also shared a "selfie" image, which Gizmodo and CNN decided to focus on in their reports.
Re: (Score:2)
Seeing all those "copies" of the one star is interesting all by itself.
Kind of like when you first wake up in the morning.
First lights? But are they quantum wave lights? (Score:2)
Mod parent Funny? But the Subject was so vacuous?
However the thought that struck me from this story was how complicated the notion of "first light" has become. In old days it really meant something when the telescope was finally assembled and looked through for the first time. If you had messed up the lens (ior mirror) grinding, then you were in a world of hurt at that point.
But now? Yes, we have some "first lights" as digitally seen through the latest and greatest new telescope, but the lenses are far from
Re: (Score:2)
*sigh* I should know better than to type before coffee.
s/lens xor lenses/mirror xor mirrors/
But now I'm wondering if there are any lenses anywhere in this telescope...
Re: (Score:2)
There are no lenses. There are mirrors. 18 of them in primary mirror. And each one of them can be steered and bent a little. Bending reduces blur and steering moves all 18 dots into one spot.
Re: (Score:2)
I corrected that typo already, but your reply does not address my actual question. Not even close, and I'm trying to make suitable allowances for my clumsy wording, too.
No need to click that link... (Score:4, Interesting)
My god, why does spaace.com have so many third part trackers?
To save you a click: the photo is just some white specks on a black background. They're using these stars for calibrating the mirrors. No amazing Hubble-like images yet.
Re: No need to click that link... (Score:3)
It's all one star, imaged at different locations on the imaging plane because the segments aren't aligned yet.
Agreed Re: space.com
Re:No need to click that link... (Score:5, Informative)
Also, NASA has an explanatory video [youtube.com] that breaks down what the telescope is seeing and what it means.
Shutter speed? (Score:2)
...once the telescope is focused, this star will be too bright to look at.
Why? I keep reading that objects which aren't particularly bright (after all, the star in question is too faint to see with the naked eye so there are plenty of brighter ones) are still too bright for this telescope but I can't find any explanation of why. To my photographic mind, if an object is too bright you reduce either aperture of exposure. I can see that you can't reduce the aperture in this case, but why can't Webb just take a shorter exposure?
Two more questions then come to mind:
* Does it mat
Re:Shutter speed? (Score:4, Interesting)
I was also curious about this, so I looked up the star on SIMBAD [u-strasbg.fr]. Well, it's not that faint, it is a magnitude 6.4 star, which means that you don't really need a telescope to see it - should be a dim naked eye object at really dark skies. Another way to look at it is tha it's around the 8000th brightest star, which, given how many stars are observable is quite bright.
But, that's not all, the JWST does not observe in visible light, it's more like orange/red to mid-infrared. At those wavelengths we should be looking at bands J/H/K on SIMBAD the star is much brighter (4.698 in mid-infrared, which is almost 5x brightness). Not sure where to find an IR brightness ranking but let's say that the star is probably easily in the top-5000 brightest stars.
I am not a professional astronomer, but AFAIK the biggest problem with bright stars is in relation to imaging sensors. When you try to image something dark, so use a long exposure, and something bright is in your frame, the pixels around the bright object quickly become saturated and cause expanding artefacts (it depends on the technology of the sensor, it is blooming & smear in CMOS - no idea what kind of exotic IR sensors JWST uses). I know that some observatories use physical absorbing masks in front of the sensor to "hide" the bright objects to get any detail around them.
I would suppose the JWST is not expected to take exposures fast enough that would not saturate such a bright star. Not sure if there's a hardware limitation because it was not a design requirement, or just that it is useless to do so. If they need to capture something close to such a bright star, they'll have to figure something out.
Re: (Score:2)
To make the point a little more succinctly - the entire optics system is optimized for observing very faint objects, its primary objective are the most distant, earliest, and thus faintest classes of objects in the Universe.
Bright objects will always cause image saturation problems, but this instrument is not designed to look at those. The dim objects that it is designed to observe require observing in regions where there is little in the way - little dust, and few stars.
Go to the source (Score:5, Informative)
instead of third parties:
The NASA JWST blog [nasa.gov]
and video [nasa.gov]
It's all the same star (Score:5, Informative)
The image is cool, but I don't think the article makes this crystal clear: its not a picture of a constellation. It's all the same star. Each mirror segment is imaging the same star onto a different location at the imaging plane, because the mirrors aren't aligned yet. There are 18 segment and 18 images of that star (annotated in the picture). The whole point of this image is to tell NASA what direction to tilt each mirror segment to make all the images overlap perfectly. I suspect that they'll move the mirrors (one at a time or multiple at once?), then re-image the same star again, see how it looks, and so on.
General question (Score:2)
Once the mirrors are aligned, if they wanted to slightly shift the area of the sky JWST is imaging, could NASA tell all the mirrors to tilt the same amount towards the new area? Or is the idea that whole spacecraft will turn, even if only a tiny bit. Tilting the mirrors a tiny amount would mean they really trust the mirror adjustments have no hysteresis (or it is well characterized).
Re: (Score:3)
Re:General question (Score:4, Informative)
There is also a flat mirror in the optical path , called the Fine Steering Mirror [google.com], that's just after the tertiary mirror and before the instrument package, that allows for continual optical image stabilization.
Re: (Score:3, Interesting)
The adjustments to the mirrors occur at roughly the same speed that grass grows.
But not if the grass is some types of bamboo, up to 10 cm an hour. [guaduabamboo.com] The fast growing bamboo is a bit of cheat though, somewhat like the speed of mushrooms popping up. The bamboo does not and cannot grow that fast all the time but instead does it in bursts, storing energy underground in its root system then converting that energy rapidly into above ground growth. Still grows quite quickly to its full height though (but this still a bit of a cheat, as it more like erecting the framework for the mature plant,
sort of offtopic but interesting (Score:2)
parent's link is sort of offtopic but interesting nonetheless. Bamboo and it's potential for reforestation and CO2 capturing.
Voyager 1 (Score:2)
I was hoping to see a 'test pattern' from Voyager 1