74
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Why are we building larger land-based telescopes instead of launching larger ones into space?
It's cheaper.
(1) With adaptive optics you can get 0.1 arc second resolution on the ground (admittedly only on a mountain top with particularly good air flow, but still!). This eliminates one of the ...
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Why is Starlink polluting the night sky a big concern if we have space telescopes?
It's a problem because there are still lots and lots and lots of ground-based telescopes.
Ground-based telescopes are still (by far) the biggest optical telescopes, and the cost of space telescopes ...
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53
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Why don't they put more spare gyroscopes in expensive space telescopes?
It's worth noting that telescopes that have suffered from severe issues with gyroscopes or reaction wheels (e.g. Compton, Hubble, Kepler, Swift) have typically done so only after operating long past ...
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39
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Has NASA released any JWST images of Trappist-1? If not, why?
The Trappist-1 system consists of an ultracool red dwarf at a distance of 12.5 pc from the Sun, surrounded by a system of planets with orbital semi-major axes ranging from 0.01 to 0.06 au.
As seen ...
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35
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Why do satellites appear as streaks in telescope images?
Satellites are moving. They are in orbit around the Earth. Satellites in low Earth orbit are moving at about 7000 m/s relative to the ground.
You can work out the orbital speed by $$v=\sqrt{\frac{GM}{...
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35
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How does JWST position itself to see and resolve an exact target?
It's true that James Webb carries fuel, and you're right that it is not used for positioning, at least not directly (see below). Fuel is used for maintaining its orbit around L2, and was also used ...
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29
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Why do satellites appear as streaks in telescope images?
Can you explain me in simple words why the satellite in this telescope image appears as a streak? The exposure time is 1 second.
This drawing should explain it:
(Note: It could be the other way ...
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How many pixels could an image of Proxima b taken by James Webb have?
The JWST will have an angular resolution of about 0.1 arcseconds, which is similar to Hubble.
The star, Proxima, has an angular size of 0.001 arcseconds, and the planet Proxima b (a super-earth) would ...
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26
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Is there enough data in light coming from distant exoplanets for Earth-orbiting telescopes to take a high-resolution photo of it?
No, not with the current or any projected "next-generation" of telescopes.
The problem isn't dust, it is distance. To put it in context, you can consider a scale model of the universe. ...
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21
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Is the measurement of distance and position of remote celestial bodies accurate?
Large masses can bend light, but space is largely empty. The light from distant stars and galaxies rarely passes close enough to another star or galaxy to have deviated. On the few occasions when it ...
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21
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Why use a large separate starshade instead of an occulting disk?
TL;DR: The Sun is well-resolved in small telescopes so a focal plane occulter works well. Other stars are not resolved (except in a few exciting cases using interferometry) so an internal blocking ...
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21
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Worthwhile to put a telescope on the far side of the Sun?
No, there are currently no plans to put a space telescope, or any other kind of satellite, at the Sun-Earth L3 Lagrange point.
The main problem is (as you mention) that it's impossible to communicate ...
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Which (if any) space telescope would have worked longer if it hadn't simply run out of helium?
Past infrared telescopes (IRAS, Spitzer, others I can't remember) in space have generally used expendable liquid He. They either ceased operation or lost a large part of their capability when the He ...
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Is there enough data in light coming from distant exoplanets for Earth-orbiting telescopes to take a high-resolution photo of it?
There is a fundamental limit to resolution called the "diffraction limit" that depends on three things:
The angular size of the feature you're trying to resolve,
The wavelength of light you'...
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Is the James Webb telescope going to orbit around the earth?
Your first question - is JWST going to orbit Earth - is a little complicated. It will follow a mission profile that will send it to the Sun-Earth $L_2$ Lagrangian point. It will take the telescope ...
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19
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Why are we building larger land-based telescopes instead of launching larger ones into space?
In addition to Mark's great answer ...
Why are we building larger land-based telescopes instead of launching larger ones into space?
If you had money for two homes, one near work and a 'summer ...
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19
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How will space telescopes catch T Coronae Borealis going nova?
Novae get brighter very quickly compared to most other astronomical bodies, but they are not "blink and you miss it" events. A nova will initially brighten over a period of hours to days, ...
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18
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Which (if any) space telescope would have worked longer if it hadn't simply run out of helium?
The Herschel infrared telescope is another recent telescope that stopped working once it ran out of Helium for its coolant.
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Why is Starlink polluting the night sky a big concern if we have space telescopes?
To expand on the "space telescopes are expensive" aspect:
Space telescopes cannot be maintained or repaired. This applies not
just to things like optics and
instruments, but also to space-...
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15
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How many pixels could an image of Proxima b taken by James Webb have?
Any planet around Proxima Centauri (or any other exoplanet around any other star) will be unresolved. That means it is so small and far away, that it would appear as a point source of light to all ...
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15
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Is there enough data in light coming from distant exoplanets for Earth-orbiting telescopes to take a high-resolution photo of it?
The only real problem is lack of angular resolution at optical and near infrared wavelengths. Lack of photons is not an issue.
Suppose there were something the size of Jupiter orbiting Alpha Cen A. At ...
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What kind of telescope would be needed to image a 10m dim object 1 million km away?
A radar telescope.
One million km is close (in space terms that's just over a tad) and well within the range of planetary radars. As an example, the [asteroid 2021 PJ1 was detected by radar using the ...
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Why aren't there any images of Sun-orbiting bodies by Spitzer?
All "big" instruments have observation logs, so does Spitzer.
The complete logs are here but there's also a filtered log for solar system observations which shows basically all planets and ...
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14
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Did this satellite streak past the Hubble Space Telescope so close that it was out of focus? If so, how close was it?
As you note, that particular image has been identified as due an "out of focus" satellite (the other images presumably show more distant satellites in e.g. geosynchronous orbits). The Nature ...
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13
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How does the James Webb Space Telescope achieve a focal length of 131.4m?
The JWST has three mirrors(*), the main mirror (6.5m in diameter) A secondary mirror, held on three struts in front of the main mirror and a tertiary mirror that reflects the light into the various ...
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At the intersection of engineering and astronomy in its structure as a scientific discipline
Yes, there is an intersection between astronomy and engineering. In my experience, it will mostly be astronomers who have a flair for technology and instrumentation who at some point, either from the ...
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12
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Why don't they put more spare gyroscopes in expensive space telescopes?
Exoplanet astrometry mission? Do you mean the exoplanet transit photometry mission, Kepler? Kepler's problem wasn't gyros: it was reaction wheels. They look a bit like large heavy gyros, but they aren'...
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Why don't they put more spare gyroscopes in expensive space telescopes?
While not possible relevant to the current gyro issues there was in fact a design issue with the Gyros. The efforts to make flexible conductors flexible left them vulnerable to being dissolved by the ...
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Why are we building larger land-based telescopes instead of launching larger ones into space?
Answering your subquestion about building on the moon:
This is subject to the same launch costs and restrictions as a space-based 'scope, plus you have to deal with landing and with gravitational sag. ...
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What is the gravitational lensing focal distance of a white dwarf star?
The gravitational focus you are talking about is actually a minimum value, defined by parallel rays of light from a very distant star just skimming past the Sun as they are bent according to General ...
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