98
votes
Does it make any scientific sense that a comet coming to crush Earth would appear "sideways" from a telescope and on the sky (from Earth)?
The comet's tail always points away from the Sun. Yes, even when the comet is heading back into the outer solar system.
This is because the tail isn't a 'trail' of where the comet has been, like a ...
- 6,418
40
votes
Accepted
Can James Webb take pictures of our solar system? In what ways will they differ from/compliment those from Hubble?
JWST must forever be oriented to remain in the shadow of its own sun shield, so that it remains cool and sensitive to the low temperatures of deep space, limiting what can be observed. Notably, it ...
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31
votes
Accepted
Why do some space telescopes require cooling (sometimes down to 3K)?
Space telescopes like Spitzer, Herschel, Planck, WISE, and in few years Webb, need to observe in the mid and far infrared wavelengths. The infrared radiation of normal spacecraft temperatures, even ...
- 58.5k
29
votes
Can James Webb take pictures of our solar system? In what ways will they differ from/compliment those from Hubble?
Here's NASA's site with an overview of already approved Solar System science missions for JWST:
https://www.stsci.edu/jwst/science-execution/approved-programs/cycle-1-go
If you click on the red number ...
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28
votes
Accepted
Would a lunar telescope provide a significant improvement over terrestrial based equipment?
As stated, the answer to the question has to be yes, a telescope on the Moon can have significant advantages over a telescope on Earth, because of Earth's atmosphere. That's why we have space ...
- 58.5k
22
votes
Can James Webb take pictures of our solar system? In what ways will they differ from/compliment those from Hubble?
https://jwst.nasa.gov/content/forScientists/faqScientists.html
10. Can Webb observe objects in our Solar System?
Yes. Webb is designed to be able to observe solar system objects having an apparent ...
- 1,270
20
votes
Accepted
If we used Hubble, or the James Webb Space Telescope, how good image could we get of the Starman?
The angular resolution of the Hubble and James Webb telescopes are about the same - both are around $0.05$ to $0.1$ arc seconds or about $4 \times 10^{-7}$ radians.
If we express the angle $\theta$ in ...
- 376
18
votes
What's the largest aperture telescope sent beyond the Earth-Moon system?
After looking through various mission articles on Wikipedia, the Mars Reconnaissance Orbiter's HiRISE camera has an aperture of 19.7 inches (50 cm), which Wikipedia claims is "the largest so far of ...
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17
votes
If we used Hubble, or the James Webb Space Telescope, how good image could we get of the Starman?
Hubble is one of the few telescopes that could possibly image Starman, as a dot. James Webb will have far more sensitivity. It's a really small space rock in a really big space. You can take a look at ...
- 121k
15
votes
Picture of equipment left on the Moon?
From Earth, you can't. This is actually quite a common question, and was answered by Telescopes.com. To see the Lunar Rover, for instance, would require a 75m telescope, far larger than anything ever ...
- 121k
15
votes
Accepted
Is it feasible to paint SpaceX Starlink satellites black so as not to frequently saturate the CCDs of the Large Synoptic Survey Telescope?
In general satellites are not "painted". They are covered in a variety of Multi-Layer Insulation (MLI) blankets with varying optical qualities. I have seen MLI in silver, black, and gold - sometimes ...
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15
votes
Does it make any scientific sense that a comet coming to crush Earth would appear "sideways" from a telescope and on the sky (from Earth)?
While those movies probably do it because that's how comets are commonly depicted, it might not be that inaccurate. Remember that the Earth itself is moving around the Sun, so if a comet is heading ...
- 1,196
15
votes
Does it make any scientific sense that a comet coming to crush Earth would appear "sideways" from a telescope and on the sky (from Earth)?
If you're the comet, the way to hit Earth is not to head directly for it. That's because Earth is orbiting the sun: you need to aim at where Earth will be, not where it is right now.
For example:
By ...
- 1,023
13
votes
Has any ground-based telescope taken a picture of a geostationary broadcast satellite?
"Resolved images of a geostationary satellite were obtained on October 30,
2009, with the adaptive optics on the largest telescope on the planet, the 10 m
Keck-II on the 14000 foot summit of Mauna Kea....
- 178k
12
votes
Accepted
Is it possible to control the operation of the Hubble Space Telescope from ground stations?
Yes, Hubble is actively controlled from the ground.
See this NASA page on Hubble Mission Operations
Examples include monitoring and adjusting the spacecraft’s subsystems (e.g., power, thermal, ...
- 6,906
11
votes
Accepted
What's the largest aperture telescope sent beyond the Earth-Moon system?
Voyager's Infrared Interferometer Spectrometer (IRIS) has an aperture of 0.5 m (19.685").
This is not an imaging instrument though (resolution=1 pixel). The large aperture was needed to provide ...
- 126k
10
votes
Was Hubble really related to spy satellites?
This answer addresses the headline question, rather than the detailed content that suggests a connection between HST and a KH9.
There may be a connection between the Hubble and a KH11. Refer here ...
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10
votes
Are space camera sensors usually round, or square?
Silicon wafers are sliced from a giant single crystal of silicon called a boule, which is grown from a seed crystal dipped in and then slowly pulled from molten silicon.
Circuits such as CCDs (and ...
- 149k
9
votes
Accepted
How did Skylab's electrographic ultraviolet camera work?
Similarly to night vision devices, the light sensitive part is the photocathode, which releases electrons when hit by photons. The electrons at the photocathode are accelerated by the -25 kilovolt ...
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8
votes
What is the current state of affairs concerning space telescopes?
To answer your original question regarding the state of affairs of space telescopes, from the US (NASA), besides JWST, there are two large space telescope projects. Work has started on the WFIRST (...
- 2,611
8
votes
Could a 21 meter space telescope detect the nearest exoplanets?
As of 2017, 22 exoplanets have been imaged directly. The most distant of those is 1200 ly away.
This shows 4 of them orbiting HR 8799, which is 128 ly away:
These observations are good enough to ...
- 126k
8
votes
Is there any Scientific Benefit to the Lower Albedo levels on the Darkside of the Moon?
The short answer: for optical astronomy (IR through gamma wavelengths), no, there isn't any huge advantage. But for radio astronomy there are distinct advantages to being on the lunar far side, they'...
- 18.2k
8
votes
How does the James Webb Space Telescope take images with individual mirror segments?
Starting with this quote,
After launch and deployment, the primary mirror segments, secondary,
and science instruments will be misaligned relative to each other by
up to several millimeters. An ...
- 2,117
8
votes
Interesting diffraction pattern on JWST composite false-color image released today (July 11) at Biden preview - how does this arise?
The James Webb Space Telescope website has a very detailed info graphic with explanations that explain the diffraction patterns.
As far as I understand, the large blueish spikes in the image in the ...
- 12.5k
7
votes
Accepted
Is there a telescope on board the ISS?
The Celestron telescope is not stationary. It can be moved around inside the space station to look through any window.
It is however just used to observe the Earth, and the reason for that is the ...
7
votes
What savings allowed James Webb telescope to be lighter than Hubble?
As far as the primary mirrors are concerned, HST's mirror was made out of silica glass, and had a mass of 826 kg.
The primary mirror of the Hubble telescope measures 2.4 m (8 ft) in diameter and ...
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7
votes
Accepted
Does the Hubble telescope use a "simple" PID-controller for its pointing control system?
Yes.
According to the NASA paper "Hubble Space Telescope Pointing Control System Design Improvement Study Results", in the first full paragraph on page 2, the author states
The nominal control ...
- 1,125
7
votes
How come we can see nearby galaxies but are unable to see TRAPPIST-1?
How do we have telescopes that are powerful enough to see nearby galaxies, such as Andromeda (M31), but are unable to see TRAPPIST-1 or the other exoplanets in its solar system in detail when TRAPPIST-...
- 73.2k
7
votes
What is the process to produce a chemical composition spectrum of a celestial body?
The spectrum you show from Titan was taken using the IRIS spectrometer aboard Voyager 1. Of course Voyager 2 had one as well. A huge amount of work went into developing and optimizing the design in ...
- 149k
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