Where can I find high resolution photos of distant stars?

[AnotherParadox]

Hello

I've been digging around for high resolution photos of distant stars now for awhile. The search has been pretty difficult.

If what I've been reading is correct then there appears to be a limit to viewing small objects like stars, if this is true can someone help me understand the reason for this? I (think I) understand it has to do with light diffraction and the lens diameter. Also is there a foreseeable way this will be improved in the future of astronomy? Is the new telescope that's going up next year to replace Hubble going to help with this?

Thanks for your time and interest

 

[1oldman2]

Hello

I've been digging around for high resolution photos of distant stars now for awhile. The search has been pretty difficult.

If what I've been reading is correct then there appears to be a limit to viewing small objects like stars, if this is true can someone help me understand the reason for this? I (think I) understand it has to do with light diffraction and the lens diameter. Also is there a foreseeable way this will be improved in the future of astronomy? Is the new telescope that's going up next year to replace Hubble going to help with this?

Thanks for your time and interest

I'd have to start by recommending http://hubblesite.org/

 

[AnotherParadox]

I'd have to start by recommending http://hubblesite.org/

Naturally I tried Hubble's website but most of the images are planets, galaxies, nebula, etc. I haven't really found one of just a star itself. Maybe I'm looking in the wrong spot but then I read this on https://www.spacetelescope.org/about/faq/

Here we will try to answer the related question of how close together two features can be and still be discerned as separate – this is called the angular resolution. The Rayleigh criterion gives the maximum (diffraction-limited) resolution, R, and is approximated for a telescope as
R = λ/D, where R is the angular resolution in radians and λ is the wavelength in metres. The telescope diameter, D, is also in metres.

In more convenient units we can write this as:
R (in arcseconds) = 0.21 λ/D, where λ is now the wavelength in micrometres and D is the size of the telescope in metres.

So for Hubble this is:
R = 0.21 ｘ 0.500/2.4 = 0.043 arcseconds (for optical wavelengths, 500 nm) or
R = 0.21 ｘ0.300/2.4 = 0.026 arcseconds (for ultraviolet light, 300 nm).

Note that the resolution gets better at shorter wavelengths, so we will use the second of these numbers from now on.

Hubble’s optics are now essentially perfect, and the telescope is above the Earth’s atmosphere, so this gives an accurate value for the resolution of the image produced by the telescope before it is captured by one of the telescope’s detectors. However, the detectors have pixels that are quite large relative to these values in most cases and this degrades the resolution somewhat. The pixels of Hubble’s latest UV-sensitive instrument, the UVIS channel of the Wide Field Camera 3 are 0.04 arcseconds across. This means that the final effective resolution of telescope and detector can be estimated as:
R = √(telescope optical resolution2 + pixel size2)

so for Hubble with WFC3/UVIS, and in the UV (300 nm) we get
R = √(0.0262 + 0.0402) = 0.048 arcseconds

Then, in an extreme case, such as the Moon, where there is lots of light (a high signal/noise ratio), it’s possible to do image processing (image restoration) and retrieve roughly a factor of two better resolution at the expense of some artefacts. So for Hubble, we conclude that the best resolution we are likely to manage is about 0.024 arcseconds (in the ultraviolet). On the Moon, at its closest distance to the Earth, this would give a linear resolution of:
363 000 000 ｘ R /206 000 = 43 metres

But I'm not sure if this or something similar applies to stars as well.

 

[1oldman2]

Naturally I tried Hubble's website but most of the images are planets, galaxies, nebula, etc. I haven't really found one of just a star itself. Maybe I'm looking in the wrong spot but then I read this on https://www.spacetelescope.org/about/faq/
But I'm not sure if this or something similar applies to stars as well.

Ah! unfortunately I'm not the guy to discuss optical physics with, however you are in luck as this site has plenty of talent that should answer your questions. I did notice that today's Hubble image is a white dwarf, if its downloaded at full resolution and you zoom in it doesn't look too shabby, still not what your looking for but it is rather cool to look at.
http://hubblesite.org/image/4043/gallery

 

[AnotherParadox]

Heh yea it is. I was hoping for one as nice as these (all generated.. I think)

https://qph.ec.quoracdn.net/main-qimg-cf7e30b25bfdde5dee9c42470fced981
https://i.ytimg.com/vi/cMWMtLGGg6o/maxresdefault.jpg
http://scienceblogs.com/startswithabang/files/2010/07/Star_types_T_through_O.png

 

[Drakkith]

Heh yea it is. I was hoping for one as nice as these (all generated.. I think)

Yes, all of those are artists conceptions, not real images.
On page 5 of this link, you can see an image of the star Betelgeuse by the HST (Panels A and G). These images are diffraction limited and represent the maximum resolving power of the HST in UV light.

 

[AnotherParadox]

Yes, all of those are artists conceptions, not real images.
On page 5 of this link, you can see an image of the star Betelgeuse by the HST (Panels A and G). These images are diffraction limited and represent the maximum resolving power of the HST in UV light.

Nice. Just what I was looking for (in a sense)

I'll try to find out more about the resolving power of the HST or of future equipment. If anyone knows any good articles regarding this it would be appreciated.

 

[davenn]

I've been digging around for high resolution photos of distant stars now for awhile. The search has been pretty difficult.

surprised no-one has mentioned the obvious yet ... you won't find cause basically they don't exist ...
there may be a few random intergalactic stars but I think you will find 99% of stars are within galaxies

so your two choices are ...either all the individual stars in the sky you see visually or through telescope are ones in our galaxy ( the Milky Way). Or you can look at images of other galaxies for which stars are resolved Say M 31, Andromeda GalaxyDave

 

[OmCheeto]

Nice. Just what I was looking for (in a sense)

I'll try to find out more about the resolving power of the HST or of future equipment. If anyone knows any good articles regarding this it would be appreciated.

I just read that the JWST has the same resolution as the HST, and given the following from Drakkith's reference;

"The bright supergiant Betelgeuse (5a Orionis 5 HD 39801) has long been a favorite candidate for interferometric studies, speckle imaging, and aperture-masking techniques because it possesses the largest apparent diameter of any star beyond the Sun."​

I doubt you will find any better images of stars in the near future(20 years).

Though, a couple of hours of googling indicate that, as always, science is on the move:

Current Hubble CCD pixel physical size: 21 µm
Sensor size: 1024 x 1024
[ref]
Pixels: ≈1 million [maths]

Purported recently{2015} achieved sensor pixel size: 50 nm [ref]
Theoretical sensor size: 430,000 x 430,000 [my maths]
Pixels: ≈185,000 million​

Whether or not this will work on Hubble? I have not a clue.

My 2 hours of googling indicated to me that once again, I will be long dead before I understand all of this stuff. But the maths is fun.

ps. If it did work, the resolution would be about the same as Hubble imaging Mars, when it's ≈80,000,000 km from Earth. [ref] [and my always suspicious maths]

 

[rootone]

Even the very closest stars can't be resolved to more than a few pixels by Hubble.
https://www.nasa.gov/image-feature/goddard/2016/hubbles-best-image-of-alpha-centauri-a-and-b
However prior to that, all stars were only observable as a single point source, the reason being that they are so far away.
When JWST goes into service it will provide somewhat better resolution, though not radically better.
It will also be much more sensitive in Infrared.
Nevertheless, more distant stars are still only going to be resolvable as a few pixels.
It may well discover plenty of small red dwarfs that previously were unknown, despite seeing only a pixel or two though.

 

[Drakkith]

ps. If it did work, the resolution would be about the same as Hubble imaging Mars, when it's ≈80,000,000 km from Earth. [ref] [and my always suspicious maths]

If I understand things correctly, the resolving power of the HST is limited by diffraction, not the size of the pixels on the sensor. From the link I gave above:

Because the point-spread function (PSF) of the Faint Object Camera (FOC) has an FWHM of ~38 mas at 2550 Å, the UV disk can be resolved easily. The superb resolution of the FOC yields ~10 resolution elements over the stellar disk in the ultraviolet.

The pixels of the FOC already have a resolution of about 14.35 mas in the near-uv, which is less than the PSF of 38 mas. In other words, the FOC can distinguish between objects/details separated by 38 mas but the pixels already capture information at half this angle. Decreasing the pixel size would have little effect on resolving power. You're image would just be less blocky and more blurry.

When JWST goes into service it will provide somewhat better resolution, though not radically better.

And that increased resolution is mostly in the IR band. Since the JWST can't see UV, the best resolving power it can get is less than you'd expect.
For comparison:

Theoretical Resolving Power of HST: $27 mas$ at $λ=255 nm$
Theoretical Resolving Power of JWST: $23 mas$ at $λ=600nm$
Theoretical Resolving Power of HST in near-IR: $63 mas$ at $λ=600 nm$

Real-world values will be less (higher value). Note that this doesn't take into account special techniques often used to increase the resolving power, especially various image processing techniques developed in the last few decades.

 

[stefan r]

Naturally I tried Hubble's website but most of the images are planets, galaxies, nebula, etc. I haven't really found one of just a star itself. Maybe I'm looking in the wrong spot but then I read this on https://www.spacetelescope.org/about/faq/
But I'm not sure if this or something similar applies to stars as well.

Should be R = √(telescope optical resolution² + pixel size²)
R = √(0.0262² + 0.0402²) = 0.048 arcseconds

 

[JohnM]

There are plenty of high resolution images of a star available on the web - it's called the Sun ! SDO and other sattelites show the surface in detail and ground based observatories do quite a good job as well.

 

[rootone]

There are plenty of high resolution images of a star available on the web - it's called the Sun !

The OP was interested specifically in distant stars, though observations of the Sun probably do assist our understanding of stars in general.

 

[AnotherParadox]

There are plenty of high resolution images of a star available on the web - it's called the Sun ! SDO and other sattelites show the surface in detail and ground based observatories do quite a good job as well.

Heh, I should specify what I mean by distant stars. Distant stars as in stars not in our own solar system. 8 light-minutes is significant but hardly anything compared to 4.22-46.6 *10⁹ light-years

It should be interesting looking at those photos as well though.

Thanks for the replies everyone. Any future updates will be appreciated.

 

[1oldman2]

http://www.eso.org/public/images/po...al&utm_source=twitter.com&utm_campaign=buffer

 

[Solon]

"Where can I find high resolution photos of distant stars?"
Photographs are taken by cameras, but there are no cameras used from outside of Earths atmosphere by any of the instruments examining stars. What you are looking for is images, created by using information from instruments that gather spectral data that has been processed by computers utilising various software. Hubble is not a camera.

 

[russ_watters]

"Where can I find high resolution photos of distant stars?"
Photographs are taken by cameras, but there are no cameras used from outside of Earths atmosphere by any of the instruments examining stars... Hubble is not a camera.

This is confusing -- Hubble is a telescope and to collect data, it has cameras.

 

[Solon]

This is confusing -- Hubble is a telescope and to collect data, it has cameras.

Hubble is not so simple. These are perhaps what you imagine Hubble to be, but no telescope with camera attached has ever been tried from orbit. If it were so simple then China, Japan, Russia or India would have their own space telescopes by now.

Testbed Paves Way for Amateur Space Telescope
http://www.skyandtelescope.com/astronomy-news/testbed-paves-way-for-amateur-space-telescope/

An Amateur Space Telescope
http://adsabs.harvard.edu/abs/1982S&T...64..127S

http://www.drewexmachina.com/2014/04/16/vintage-micro-the-amateur-space-telescope/

 

[russ_watters]

Hubble is not so simple. These are perhaps what you imagine Hubble to be, but no telescope with camera attached has ever been tried from orbit.

This is confusingly put: Please say exactly what you are meaning to say it is instead of saying what you think it is not. Because the way I see it, Hubble is a pretty simple instrument - a Cassegrain type telescope with a camera at the end (actually, several cameras at the end), very similar to the one in my avatar photo.

If it were so simple then China, Japan, Russia or India would have their own space telescopes by now.

Simple doesn't mean cheap. They don't do it, because it is expensive.

 

[Drakkith]

Hubble is not so simple. These are perhaps what you imagine Hubble to be, but no telescope with camera attached has ever been tried from orbit.

What do you call the imaging sensors and their supporting equipment that are integrated into the Hubble Space Telescope (and other space telescopes)?

I call them cameras.

If it were so simple then China, Japan, Russia or India would have their own space telescopes by now.

Every single one of those countries have their own space telescopes. See here: https://en.wikipedia.org/wiki/List_of_space_telescopes

 

[rootone]

China, Japan, Russia or India would have their own space telescopes by now.

All of the countries you mentioned have produced working Earth satellites and also deeper space probes, (you can add ESA to that).
Most of these spacecraft projects involve some kind of camera.
Hubble has certainly been a marvel of engineering though what happens when it is retired?
Bits and pieces falling in the Sahara could sell for a good amount.

 

[davenn]

Hubble has certainly been a marvel of engineering though what happens when it is retired?

the James Webb Space Telescope is the planned replacement for Hubble

https://www.jwst.nasa.gov/

planned launch in 2018

 

[mfb]

What you are looking for is images, created by using information from instruments that gather spectral data that has been processed by computers utilising various software.

That is exactly what a digital camera does.
The Apollo missions had a few analog cameras, but they fell out of use because digital cameras are better.

E-ELT's EPICS camera will mainly look for exoplanets, but with its 5 milliarcseconds angular resolution Betelgeuse can be imaged with 10 (useful) pixels diameter.

the James Webb Space Telescope is the planned replacement for Hubble

WFIRST will also take over some parts of the Hubble science program.

 

[newjerseyrunner]

E-ELT's EPICS camera will mainly look for exoplanets, but with its 5 milliarcseconds angular resolution Betelgeuse can be imaged with 10 (useful) pixels diameter.

Here is an article about a picture of Betelgeuse.

 

[berkeman]

no telescope with camera attached has ever been tried from orbit.

They also sometimes look down instead of up...

https://www.google.com/earth/

 

[newjerseyrunner]

What types of images are you looking for anyway? You should be aware that in visible light, stars are pretty boring. Viewed with visible light, the sun is a nearly featureless white orb. All of those really interesting pictures are non-visible spectrum.

 

[Drakkith]

What types of images are you looking for anyway? You should be aware that in visible light, stars are pretty boring. Viewed with visible light, the sun is a nearly featureless white orb. All of those really interesting pictures are non-visible spectrum.

I think most of those interesting images use narrowband filters to see specific wavelengths in the visible spectrum to bring out different details.

 

[mfb]

Big starspots could be visible in 10x10 images.

I took http://www.skyandtelescope.com/astronomy-news/star-spins-show-ages-010820143/ and compressed it to 10x10 pixels, then enlarged it again to make an image of reasonable size. This is the result:

The actual images will probably look a bit better in the center and worse at the edges, as angular resolution and pixel size are not the same thing.
With multiple images of that quality you can learn a lot about starspots.

 

[AnotherParadox]

"Where can I find high resolution photos of distant stars?"
Photographs are taken by cameras, but there are no cameras used from outside of Earths atmosphere by any of the instruments examining stars. What you are looking for is images, created by using information from instruments that gather spectral data that has been processed by computers utilising various software. Hubble is not a camera.

Photographs are taken by cameras. "Definition: Camera - a device for recording visual images."

"images, created by using information from instruments that gather spectral data that has been processed by computers [utilizing] various software"

All digital cameras work in this manner in some way or another. We are all well aware that Hubble is not using film. It is digitally recording images therefore it is a digital camera combined with a high powered telescope.

As far as semantics are concerned I consider anything that is a directly or filtered recording of the real world to be a photograph (or image) whereas something such as a painting, gif, meme etc. to be an image (and not a photograph).

An argument can be made that the distinction between reality and fantasy is a better distinction with semantics than analog vs digital.

However this distinction would be considered arbitrary, especially because neither is defined to this extent. An attempt to define them would probably be arbitrary as well. Langauge doesn't have the same luxury as math.

I agree with the other posts that were in response to this comment.

What types of images are you looking for anyway? You should be aware that in visible light, stars are pretty boring. Viewed with visible light, the sun is a nearly featureless white orb. All of those really interesting pictures are non-visible spectrum.

Any type of images really so long as they are photos and not CGI etc. and are from an actual telescope. Ideally the ones like we have of our own sun but such a thing is a fantasy currently it seems. Even if they are in the non-visible spectrum instruments could be used to represent them in the visible spectrum such as how heat vision etc. does.