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83 votes
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Is there a better explanation of this picture showing the very distant star "Earendel"?

I did the annotation of that figure for the press release, so let me start by apologizing for the poor explanation, and then try to dig deeper into what's going on :) (although you already seem to ...
pela's user avatar
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34 votes
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What detail can Hubble see on Mars?

Forget about magnification. People who know telescopes don't think in terms of magnification. What matters is the angular resolution, or the resolving power: the angular size of the smallest details ...
Florin Andrei's user avatar
27 votes
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Does the recent news of "ten times more galaxies" imply that there is correspondingly less dark matter?

All Conselice et al. (2016) appear to suggest is that when you look at something like the Hubble deep field, there are many faint (and presumably low mass) galaxies that are not seen. This has ...
ProfRob's user avatar
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18 votes
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Which are stars and which are noise in this comet photo?

Is that right? Yes. Is the fuzzy one an extended object? That would certainly be my guess (probably a distant galaxy). What causes so many isolated pixels to be so much brighter ...
Peter Erwin's user avatar
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14 votes

Why is Ganymede's aurora only visible in ultraviolet while Earth's is bright green and red?

Quoting from Nat.Geo. article (which has that same UV image), Then, in 2010 and 2011, Hubble took a close look at the moon. More specifically, it looked at the auroral bands ringing Ganymede’s ...
Carl Witthoft's user avatar
13 votes
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What are the large round dark "holes" in this NASA Hubble image of the Crab Nebula?

I think my deleted answer to your previous question covers this well, so I'll add it here. These two spots are known as the east and west bays of the Crab Nebula. They appear to be the result of a ...
HDE 226868's user avatar
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12 votes

How does a galaxy in Abell 2261 exist without a black hole in the center?

The Brightest Cluster Galaxy (BCG) in Abell 2261 ("Abell 2261-BCG") is a massive elliptical; these almost always seem to have supermassive black holes in their centers. In addition, the ...
Peter Erwin's user avatar
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11 votes
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How does the Hubble telescope capture long-exposure photos?

The answer to this is that such images are not taken continuously. The HST did not stare at one part of the sky for 10 continuous days, but rather it stared at one part of the sky for short periods ...
zephyr's user avatar
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11 votes
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Portion of universe visible if gathering image from inflationary epoch

tl;dr: Your field of view would cover roughly one square centimeter of the sky at that time, and you would observe roughly 50 billionths of the observable Universe. You can't really… With photons, ...
pela's user avatar
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11 votes
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How long was the HST initially supposed to work?

15 years. Hubble was designed with an anticipated 15-year lifetime based on the expected integrity of the main mirror. It was believed that over HST’s 15-year life the space environment in low Earth ...
James K's user avatar
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10 votes
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Questions about convolving/deconvolving with a PSF

Convolution is not a uniquely invertible process in the presence of random noise in your image. Deconvolving a noisy image can give misleading results, even if you have perfect knowledge of the PSF. ...
ProfRob's user avatar
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10 votes
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What is the "lost light" in this unusual Hubble Deep Sky image?

Let me see if I can explain the main aim and accomplishment of this work. First off: the picture you're puzzling over is a "luminance RGB" image, in which the bright regions are represented by color (...
Peter Erwin's user avatar
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10 votes

What detail can Hubble see on Mars?

The Hubble space telescope has a 2.4m mirror and is pretty much diffraction limited, so at near-UV wavelengths of say 240nm it has an angular resolution of about $10^{-7}$ radians. Mars' closest ...
Steve Linton's user avatar
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10 votes
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Has Hubble photographed Venus in near IR? If so how does it compare to the new and exciting Parker Solar Probe image?

This web page -- "Here is why the Hubble Space Telescope only looked a few times at Venus (and why it looked at the Moon instead)" -- seems like a pretty good answer to your main question (...
Peter Erwin's user avatar
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9 votes

What is the resolution in megapixels of the Hubble Telescope?

The size of the cameras that took the Pluto pictures is easy enough to find: the ACS Wide Field Camera has two 2K by 4K (hence 8 Mega pixel) CCDs, with a field of view of 202×202 arcsec. The high ...
ProfRob's user avatar
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8 votes
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Green objects in Hubble Ultra Deep Field

what are the green objects that you see scattered in the Hubble Ultra Deep Field image The Hubble Ultra Deep Field (HUDF) has approximately 10,000 objects in it. Between 25 and 50 of them are ...
zephyr's user avatar
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8 votes
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What is the cause of all of these sharp, concentric rings around bright stars in this HST image?

The diffraction pattern at the focal plane created by a circular aperture is called an Airy Disk or Airy Pattern. Both the outer opening and the inner hole plus secondary contribute to the exact ...
eshaya's user avatar
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8 votes
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If we had the right technology could we see a distant star in detail?

The only limitations would be related to building an instrument large enough. There's a limit to the size of the finest detail a telescope can see. "Size" here is angular size, the angle that the ...
Florin Andrei's user avatar
8 votes

What is the "lost light" in this unusual Hubble Deep Sky image?

When you plug the lead researcher's name into Arxiv, the first search result is The missing light of the Hubble Ultra Deep Field. 3 main steps: Creation of sky flat fields for the four filters....
Hobbes's user avatar
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7 votes

Why was the (small) Hubble better able to find KBO targets for New Horizons than large adaptive optics ground telescopes?

I suspect it's a combination of two things: Stable, guaranteed high-resolution imaging across the entire field of view, something not possible with ground-based adaptive optics; Very low background ...
Peter Erwin's user avatar
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7 votes
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Has the Hubble ever been pointed at earth?

xkcd already did the math on this one! Like Gauti's answer, xkcd also links to this question on Hubble's website. Hubble moves too fast for its minimum exposure time to be able to focus on anything on ...
Cody's user avatar
  • 1,180
7 votes

How do we know the radius of the universe is 47 billion light years?

The observable universe's edge, by definition, is the farthest part of the Universe that light could have reached us from. Let's say light from the observable universe's edge has just reached us. The ...
Sir Cumference's user avatar
7 votes

How are "parallel fields" implemented on the Hubble Space Telescope?

As the question Instrument aperture sizes on Hubble Telescope shows, the focal plane area is large enough to focus on several instruments at the same time (but with each capturing a different area). ...
amI's user avatar
  • 200
7 votes

How does a galaxy in Abell 2261 exist without a black hole in the center?

Physics doesn't require a black hole at the centre of a galaxy, it just indicates that it is likely. All you need is mass. If the mass is not dense enough to form a black hole, it can still be high ...
Rory Alsop's user avatar
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7 votes
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What is this curve, captured both in the Webb and Hubble images?

It is a strongly lensed, and triply mirrored, galaxy. Close to (but not at) the so-called critical curves of the lens, which is where you in principle will have infinite magnification, on either side ...
pela's user avatar
  • 38.9k
6 votes

What would the night sky have looked like 12.9 billion years ago when galaxies first started to form?

As @Gerald stated in his excellent answer, the Hubble XDF photo might describe the night sky - many irregular, blue galaxies. As the redshift at 12.9 billion light years is about $z=6.5$, the universe ...
WarpPrime's user avatar
  • 6,684
6 votes
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who invented the Hubble telescope

There was no single designer of the Hubble telescope. It was designed and build by NASA, with contributions from the European Space Agency (ESA). The advantages of a telescope in space have been ...
James K's user avatar
  • 126k
6 votes

How good is the HST compared to ground telescopes?

Adaptive optics techniques have only been successfully applied in the far red and near infrared. HST produces images with spatial resolution equivalent to ground based adaptive optics images, but it ...
ProfRob's user avatar
  • 156k
6 votes

Can a telescope image be amplified to see more by adding distant lenses or mirrors?

Speaking in general, telescopes are designed as complete systems from the beginning. It's not generally feasible to improve performance by just adding yet another lens or mirror to the assembly. The ...
Florin Andrei's user avatar
6 votes
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How does V838 Monocerotis look today? Any subsequent light echo images, or is the party over?

I'm not an observational expert, but here's what I found. I found this object (V838 Monocerotis) on the HST data archive. https://archive.stsci.edu/hst/search.php I input the 'Target Name' as "...
Study Astrophysics's user avatar

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