34

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 that you could see in an instrument. Rule of thumb: the resolving power of a telescope with a diameter of 10 cm is 1 arcsecond when using visible light. The ...


28

As @astromax observed, one of the primary factors that makes a space based telescope better than an equivalent telescope of the same size is scattering. Along with scattering, there is also refraction which can be especially problematic when combined with atmospheric turbulence. In the modern era, this problem can be remedied to a certain extent using ...


24

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 absolutely no effect on the need for dark matter. The main results are: (i) as you look back in time, the overall (co-moving) density of galaxies (more massive than a ...


17

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 than the background? Is this just the tail of a statistical distribution of shot noise, or are there other mechanisms that can produce single pixel noise many ...


14

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 poles. Hubble studied the auroras in the ultraviolet, but Saur said the shimmering lights would be visible to human eyes. “If somebody could be standing ...


12

There are a number of things which are important for a telescope. The first is the light collecting power of the telescope, which is simply a measure of how many photons the telescope can collect from an object. This, not surprisingly, is affected by the size of the primary mirror/lens of the telescope. The second issue is the telescope's angular resolution, ...


12

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 torus partially encircling a section of the nebula. The pulsar's magnetic field interacts with the gas and dust in the torus, which blocks synchrotron radiation ...


11

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 the cosmic microwave background (CMB), are located here because Earth is a hundred times brighter than the CMB in this wavelength region. Herschel observes in ...


11

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, you will never be able to see further back than to recombination, when the Universe was 380,000 yr old, because until then, the free electrons made is opaque to ...


10

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 Earth's surface that were approximately $500\times10^{3}/3\times10^{8} = 0.0017$ seconds old, since that is how long it takes light to travel from the Earth's ...


10

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 bigger in size than they are far in light years away compared to pluto from earth. Take the galaxy NGC 5584 for example: It spans 50,000 light-years and it's 72 ...


10

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 change between their frames of reference. But if one of the observers is a photon the lorentz transformation becomes singular, because $\gamma$ is infinite. Simply, ...


10

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 over a long time which, when added up, amounted to 10 total days of observations. To quote Wikipedia on the subject of how the Hubble Ultra Deep Field (HUDF) ...


10

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 distance to Earth is about 54.6 million km, so the theoretical minimal resolution is between 5 ad 6 km. So large cities might be visible if they have lots of ...


9

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 takes 8 minutes to reach to us. So if somehow sun disappears suddenly(very unlikely) we wouldn't know for 8 minutes.


9

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 resolution HRC had a square 1 Megapixel camera with a 26×29 arcsec field of view. The reason that the images of Pluto are relatively poor, is that Pluto is small! ...


9

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. In general, when you are fitting models to data, it is far better to compare the models and data in the observational space of the data, where the uncertainties ...


9

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 (a sort of pseudo-true color using near-infrared images), with the second faintest parts represented with black and the very faintest parts with white. The ...


8

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 kilometers above the surface) is above almost all of the atmosphere, but there's still enough residual air to cause some slight drag. It's not higher because it was ...


8

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 by absorbing more light. In this case we can assume that the focal ratio (derived from Hubble's lens aperture) and the luminance of the scene (how much light ...


8

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 detail is covering in the visual field. For a given wavelength of light, the smallest angular size depends on the aperture (diameter) of the telescope in a linear ...


8

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. This process is fully described in Sect. 2.4. – Creation of a catalogue of all WFC3/IR datasets that may affect our mosaics (including calibration ...


7

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 that resolves Charon. Thus, the photo that you see is a composite of two image processing techniques: one designed to showcase Charon and one designed to ...


7

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. (Footnote, as Rob Jeffries points out, it's infra-red through long-wave visible light only). Hence, no Blue/Indigo/Violet or Green, but some yellow. So, it'...


7

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 in the optical for HST (Hubble), versus a very high background for ground-based AO in the near-infrared. Most adaptive optics systems are only able to correct ...


7

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 identified as extremely faint stars. That means the remaining ~10,000 objects are galaxies. To answer your question literally then, the green objects are galaxies. ...


7

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 the surface. He goes one step further, linking to this article on Bad Astronomy that points out that Hubble frequently points at the sunlight side of Earth to ...


7

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 function. This is usually not easily observed with ground based telescopes because the seeing fluctuations due to air turbulence smears it out. These images use ...


6

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 unrealistic pixel count. Details below: The linear size of the focal plane is large - one document says it's the size of a "dinner plate". But the instrument is an f/24, ...


6

The "stair-step" pattern visible in the first image is characteristic of the the Hubble's Wide Field and Planetary Camera 2 (WFPC2). This pattern is created by the arrangement of the four CCD chips. This image shows how the three larger "wide field" chips and the smaller, single "planetary camera" chip are arranged to create the pattern. The bottom picture ...


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