79 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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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12 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 ...
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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 ...
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11 votes

Photon Paradox?

And that is why you don't do the calculations in a frame that is moving at lightspeed. If you have two observers that are moving relative to each other you can use the Lorentz transformation to ...
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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 ...
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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, ...
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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 ...
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10 votes
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Is it possible to use Hubble Telescope to observe Earth in the past?

The only way you can use Hubble to view the Earth "in the past" is to swivel it and point it at the Earth now. Assuming that this didn't break the telescope (it would) you would collect images of the ...
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  • 114k
10 votes
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Are space telescopes completely out of the earth's atmosphere?

A handful of space telescopes are located in Langrange point L2, 1.5 million km from Earth. This is much farther away than the Moon, and far outside Earth's atmosphere. WMAP and Planck, which measure ...
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10 votes
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Inability of Hubble to clearly resolve nearby celestial objects

This has to do with the angular resolution of the Hubble telescope and the ratio between the distance of an object in space and its size in space. The galaxies that the Hubble telescope can see are ...
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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 ...
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  • 9,893
9 votes

Why can we still see 10 billion year old galaxies?

Those galaxies were 10 billion light years away from Earth. So light would take much more time to reach here and that light which is now 10 billion years older can be seen now. Even light from the Sun ...
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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 ...
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9 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. ...
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9 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 (...
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9 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 (...
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8 votes
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Why is there a black stripe in the Hubble images of Pluto?

That photograph is a composite of two images taken with different exposure times. To be correct we'd have to say that the exposure of the two photographs is different, i.e. the outer photo was created ...
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8 votes

Are space telescopes completely out of the earth's atmosphere?

This article contains a list of space telescopes. It's likely to be nearly complete. The extent of the Earth's atmosphere is not very well defined. The altitude at which Hubble orbits (about 550 ...
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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 ...
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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 ...
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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....
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7 votes

Successor to the Hubble Telescope

The James Webb Space Telescope (JWST) will be Hubble 2.0, and, my personal favorite, it could get a better look at planets in other solar-systems than we've ever had. Scheduled for launch in 2018. (...
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7 votes

Why is there a black stripe in the Hubble images of Pluto?

Pluto itself so bright that Charon would not be visible in the image if it were exposed in a way to show the remaining moons. Likewise, the remaining moons as so faint as to not be visible in an image ...
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7 votes
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Instrument aperture sizes on Hubble Telescope

EDIT: You can't have a very wide field, and simultaneously a very high resolving power, in an instrument with a large focal ratio (or any instrument, really), unless you use sensors with an ...
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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 ...
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7 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 ...
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