Talk:Hubble Deep Field

Image

There is now a new Hubble ULTRA Deep Field image available (TODAY 3/9/04). I would love to see that entered into wikipedia, but I do not have the technical expertise to do the edit myself. Any volunteers? - FrankH 3/9/2004

Contradiction?

The Hubble Deep Field page says that the HDF image is the deepest image of space taken in visible wave lengths, but the Hubble Ultra Deep Field page says the HUDF page is the deepest image taken in visible wave lenghts... Wouldn't it be logical to conclude the the Hubble Ultra-Deep Field image is the deeper image of the two? --5ptcalvinist 17:18, 14 October 2006 (UTC)

It says that the HUDF is 11.2 square arcminutes and the HDF is 144 arcseconds across, which equates to a maximum of 5.76 square arc minutes. I doubt we did a tinier slice of sky in the 90's than the 2000's and some change is needed to clear it up. I'll look around for a scholarly citation of the actual arc lengths of sky each respective deep field surveyed and give some citation. --150.216.128.186 17:47, 14 November 2007 (UTC)

http://hubblesite.org/newscenter/archive/releases/2004/07/ So hubble says HUDF is 12.7 millionth of the sky. The sky contains 14851080 square arcminutes (41253 square degrees * 360 http://www.badastronomy.com/bitesize/bigsky.html) so one 12700000 of that would be 1.169 square arcminutes.

http://www.cosmiclight.com/imagegalleries/deepfield.htm this site says deep field is 15 arcminutes across, 225 square arc minutes at most... but a little less from not being a perfect square.

http://hubblesite.org/newscenter/archive/releases/1998/41/image/c/ This is hubble's site saying 15 arc minutes across as well. So I think it's safe for me to go ahead and change the data of both --150.216.128.186 18:15, 14 November 2007 (UTC)

I think this is a misunderstanding. The hubblesite.org page cited explains:

"The carefully selected HDF-S target field in the constellation Tucana, as imaged by the 4-meter Blanco telescope at the Cerro Tololo Inter-American Observatory in Chile. The field of view is 15 arc minutes, approximately half the angular diameter of the full moon. The respective fields of Hubble's three instruments are outlined."

so the Cerro Tololo image shows the targeted field, which has a FOV of 15 arc minutes, and as shown in the image the FOV of HDF-S is only a fraction of that, most probably 144 arc seconds (2.4 arc minutes) as stated in the article earlier. Please note also, that the specs of the WFPC2^[1] used for the imaging of HDF-S state a FOV of 2.7 arc minutes. Please check and consider reentering the original value for the FOV. --Sir48 (talk) 19:32, 16 December 2007 (UTC)

There has been no response to this, so let me add, that the source: [2] states the size of the field as 5.7 arcminutes² for both the HDF and the HDF-S. Please note, that this corresponds to 2.4 arcminutes across.--Sir48 (talk) 18:16, 20 January 2008 (UTC)

Some queries

'A special Institute Advisory Committee'—can 'special' be removed or qualified?

It was described as such in Williams et al (1996) - I'm guessing they mean an advisory committee which was specially convened rather than a standing committee, although I couldn't say for sure - will try to find out. Worldtraveller 11:42, 30 August 2005 (UTC)

Please check my change: 'the areas of sky towards the poles of Hubble's orbit that are not occulted by the orbit of the Earth or its Moon'—the role of 'orbit' was unclear.

Tried to clarify this in the text, and Image:Hubble Deep Field observing geometry.png in the Observations section also illustrates how the CVZs come about. Worldtraveller 11:42, 30 August 2005 (UTC)

congrats!

Well done indeed. Tony 05:11, 4 September 2005 (UTC)

Data processing, some queries

How many pixels does the HDF contain ? The statement "final pixel sizes of 0.03985 arcseconds" and an image size of 144 arcseconds implies that it is 3613.5 pixels wide. 0.03985 arcseconds is a very odd number; there is almost certainly some rounding or uncertainty which makes this inappropriately precise, especially in contrast to the ".09 arcseconds" for the unprocessed pixels. What is the bit depth of the image ? It seems odd that an article about a digital image doesn't say how big it is. Great article though. PeterGrecian 12:57, 13 October 2005 (UTC)

The original science frames each contain four blocks of 800x800 pixels = 2.56×10⁶, but the drizzling resampling does give that very exact pixel size, smaller than the original pixel size due to the image reconstruction from sub-pixel pointing changes. Don't know about bit depth, each monochrome image has an 8 bit greyscale, but I don't know enough about the terminology to know whether that means the total bit depth is 256⁴. Will do some reading and add what I find out to the article. Worldtraveller 08:57, 14 October 2005 (UTC)

The HDFN images I have are all in FITS format, and measure in COUNTS. That is, there is no bit depth per se, but each pixel is assigned an integer corresponding to the number of photons detected. On top of that, there are considerable blank areas around the perimeter of the image, which is an artifact of the optics. The normally quoted figure for WFPC2 images is 2 megapixels, although the drizzeling probably increased this. Incidentally, should we link to the actual data files themselves, or is that something only of interest to us astronomers? Modest Genius 17:07, 18 February 2006 (UTC)

Scott Wyffels???

I find it unlikely that any one astronomer could single-handedly repair a satellite in orbit without any mention appearing online about his acheivements. Accordingly I've removed the daft reference to "Scott Wyffel" repairing the hubble optics. If this is in error, please provide a reference here. Mat-C 22:08, 13 October 2005 (UTC)

Even if that could be referenced, that information would belong in the Hubble space telescope article and not this one Majts 22:40, 13 October 2005 (UTC)

To the Stars Manifest Destiny

The United States needs the technology to get to the stars in a reasonable time. Reasonable is any star in the Milky Way galaxy (our galaxy) within an hour. The technology for space travel for life support systems is not mature enough and needs a new technology advance for deep space travel lasting years making it very difficult for any person to currently travel beyond the Earth's Moon.

The United States needs a ways and means to get to the stars. However it may be, a new and better understanding of the Universe, new and better understanding of life support systems for space travel, new and better ways of travel (airpower, by example, was a unexpected and very successful), new and better power sources including power sources for space travel, and new and better propulsion for space travel needs to be made. We need something better than chemical, nuclear, or ion rockets (all three have been examined) to get us past the light barrier problem to first take the Milky Way galaxy for humanity and the United States, and second take the Universe as it is ours. The galaxy called the Milky Way galaxy belongs to the United States and then humanity, so it is ours to take and use to our prosperity with full authority over the galaxy given to the United States and humanity. The rest of the Universe is ours for the taking for the United States and then humanity to use for our prosperity with full authority over the Universe given to the United States and humanity. Manifest destiny is there, all the people of the United States and the rest of humanity shall take advantage of any ways and means to improve technology; all of the people of the United States and the rest of humanity shall take advantage of any opportunity go out into our galaxy initially starting from our solar system the United States has called the Sol system, and then go to the rest of the Universe and take it, since it is ours and ours by authority. Every day in science fiction entertainment the capability for people to travel and prosper across the galaxy and the Universe is imagined. We have the ability to imagine it, now we must do it and go to the stars for our purposes and claim what belongs to us as the United States and rest of humanity.

Even though your ideas are intriguing, this page is just for talking about the article. Majts 23:08, 15 October 2005 (UTC)

What has the United States got to do with anything? 203.218.87.40 12:37, 16 December 2005 (UTC)

Very unclear

"galaxies, some of which are among the youngest and most distant known." If they are the most distant, they must be the oldest, not the youngest, that's very basic cosmology. If the intended meaning is "observed as they were at a very early stage of development" or "observed as the were at a very young age of the universe", please say so. Thanks. 84.141.103.132 11:34, 19 August 2007 (UTC)

External links

Should we have the following two external links in the article? (They were in it until I removed them a few minutes ago)

• ESA information page about the HDF
• The most important image ever taken (short educational film on the Hubble Deep Field)

The first links to an ESA page summarizing all of the deep fields, but they're now covered in more depth here. The second is to a video by an amateur astronomer. Personally I don't think either are needed. Mike Peel (talk) 13:39, 27 December 2008 (UTC)

It seems reasonable to remove them. Check around 1:30 into the video. — Twas Now ( talk • contribs • e-mail ) 00:43, 28 December 2008 (UTC)

emptiest section of space?

I heard several astronomer types say that the Hubble Deep Field was a result of scientists pointing it to the emptiest part of the sky. Nothing in this article tells that story. Has anyone else heard this?69.76.132.166 (talk) 03:17, 12 June 2009 (UTC)

This is mentioned in the article: "The field selected for the observations needed to fulfill several criteria. [...] The target field had to avoid known bright sources of visible light (such as foreground stars), and infrared, ultraviolet and X-ray emissions, to facilitate later studies at many wavelengths of the objects in the deep field" — Twas Now ( talk • contribs • e-mail ) 22:10, 12 June 2009 (UTC)

yawn69.76.132.166 (talk) 03:37, 13 June 2009 (UTC)

I have to laugh at the reaction "yawn" by the IP editor. Sorry the HDF is boring you!

But seriously about this issue, the information in the article and clarified above does seem to imply that the selected field is an emptier part of space, without actually stating it. What is really the case? What's the relationship between the density of near and far parts of space? Is it really that an absence of near space obstructions correlates with far space spareness? Or our near space obstacles just obstructing even emptier space? +|||||||||||||||||||||||||+ (talk) 11:23, 29 June 2012 (UTC)

Youngest galaxies?

in the article, the opening paragraph includes: "...almost all of the 3,000 objects in the image are galaxies, some of which are among the youngest and most distant known. By revealing such large numbers of very young galaxies, the HDF has become a landmark image in the study of the early universe,..." "...youngest and most distant.." is by itself a contradiction, surely the contributor meant oldest..? If nobody objects, I'll change these two occurrences. If similar errors are also present elsewhere in the article they should also be changed, although I haven't noticed any. SBORK 04:22, 29 July 2009 (UTC)

There is no error. Those galaxies are the youngest—they are observed in the process of formation. Ruslik_Zero 06:01, 29 July 2009 (UTC)

Ok, but since those galaxies are the 'most distant known' that also means that are the oldest known because the light has taken 12 billion years (or however far away they are) to get here. It reads as a contradiction to me. Also, with regard to the 'study of the early universe', I would've thought that the HDF image was important because it contained many galaxies that were so distant - rather than galaxies that were so young. Just some thoughts. SBORK 07:31, 1 August 2009 (UTC)

There's two different aspects: the age of the galaxies that we're seeing (which are some of the youngest seen), and the light travel time (the photons that are travelling towards us are old). Astronomers tend to define young and old the same way as you'd define it for people - whether you're seeing them earlier or later in their life. You wouldn't call a baby old just because you're seeing it from a long distance away. ;-) Mike Peel (talk) 08:52, 1 August 2009 (UTC)

Fair enough, I guess the connection between how far away the galaxies are and therefore what the minimum age of the universe must be belongs elsewhere. The section 'Scientific Results' basically describes what I was referring to anyway. Also, I just noticed another user had queried the older/younger description some time ago - guess I'll read the discussion page next time before commenting ;-) In any case, it's a nicely written and informative article. SBORK 04:29, 4 August 2009 (UTC)

Redshift and Distance

The article says that there are many galaxies with a redshift of around 6, corresponding to a distance of 12 billion light years. Is this distance estimated by the luminosity of the galaxy? (JDoolin (talk) 15:11, 6 August 2010 (UTC))

Black corner?

Why does the HDF have a black corner - did one of the sensors not work right? --84.119.68.66 (talk) 21:16, 16 December 2011 (UTC)

It's part of the design of the camera. That corner is half the size, but twice as detailed. See Wide Field and Planetary Camera 2 and File:Jfader hubble.jpg. Modest Genius ^talk 15:10, 6 March 2014 (UTC)

HDF and big bang theory

I just read that very interresting article, and one very basic question came to my mind: If the HDF image shows galaxies ~12 billion lightyears far away, that means that the light took 12billion years to reach the hubble telescope. How did the objects came to the place from where they sent the photons to us 12 billion years ago ? If the big bang happend 13,7 billion years ago, these objects had to travel the 12 billion lightyears in just 1,7 billion years, which would mean an avarage speed of sol7 ?!? Most propably there is a major mistake in my thinking. Is there anyone who can explain this to me ? 86.56.255.10 (talk) 09:33, 19 February 2012 (UTC)

http://en.wikipedia.org/wiki/Metric_expansion_of_space Viciouspiggy (talk) 08:39, 20 November 2012 (UTC)

How many arcminutes?

This evening I have been working to clarify the relative sizes (in arcminutes) of the HDF, the HUDF, and the HXDF. I had success with the latter two articles, but I am struggling on the HDF. Can anyone find a reliable source on this?

Currently this article (HDF) says, "2.5 arcminutes across." However, it does not provide a source, and also it does not clarify whether this refers to the edge or diagonally. (You laugh, but the prior text of HUDF also used "across," and only after research did I learn that this was meant diagonally.)

Further down, the article states that the area is "5.3 square arcminutes." This corresponds to an edge of 2.38 arcminutes (assuming the area refers to a rectangular area -- but since the HDF is not a complete rectangle, this conveys the idea of a longer edge if taken literally.)

My own researches have turned a handful of reliable-looking, but non-academic, claims that the dimensions are 2.7 arcminutes square. [3] , [4] , [5].

Finally, in a discussion on this page from 2007, it was observed that the "Wide Field and Planetary Camera 2" has a field of view of 2.7 arcminutes. However, I am not a specialist and I don't know how to evaluate this information. (Isn't it possible that the image was cropped?)

Thanks,

Andrew Gradman ^talk/_WP:Hornbook 09:22, 26 February 2014 (UTC)

The HDF is basically the same dimensions as the WFPC2 camera (modulo a few arcsecond dither pattern). WFPC2 is images a 150"x150" area, minus the cutout due to the Planetary Camera.1. It's probably worth mentioning the dimensions on on the WFPC2 wiki page, too. - Parejkoj (talk) 17:15, 28 February 2014 (UTC)

I updated the width of the HDF to 2.6 arcmin following two sources that have been already cited in the article: [6] and [7] MaruchoV. (talk) 00:52, 27 April 2016 (UTC)

Portion of the night sky?

Currently the article says that the HDF is one 24-millionth of the whole sky. This fraction seems too small. The Hubble website says "The whole sky contains 12.7 million times more area than the Ultra Deep Field." (The Ultra Deep Field is about the same size as the first Deep Field.)

http://hubblesite.org/newscenter/archive/releases/2009/31/fastfacts/

But even this fraction seems too small. There are about 41253 square degrees in the night sky or 41253 * 360 = 14851010 square arcminutes. If the HDF is about 2.6^2 = 6.76 square arcminutes, then shouldn't the HDF be 6.76/1485101 = 1/2196905.325 or one 2-millionth of the whole sky?

https://en.wikipedia.org/wiki/Square_degree — Preceding unsigned comment added by TrainRobberGZ (talk • contribs) 10:49, 31 October 2016 (UTC)

I think you are calculating the surface area of the sphere of observation as being the square of the radius. If you use the correct area which is four PI times the radius squared you arrive at the number the author used - one 24 millionth of the sky. — Preceding unsigned comment added by 2600:1700:8e00:db00:2d21:1473:e9e3:4853 (talk • contribs) 03:44, 12 July 2022 (UTC)

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Can't find what I'm looking for in this article.

People are coming to this article from search results on Google or other search engines wanting to know, specifically, how far from Earth the Hubble Deep Field is located. That information should be in the first sentence or two of the article. I couldn't find the answer reading the first couple of paragraphs and I gave up and will look to a different source for the answer. If it's there near the top of the article and I missed seeing it, I'm sorry for complaining. 2600:8801:B011:300:DCC5:2BA5:8F5B:EB91 (talk) 20:23, 26 April 2021 (UTC) James.

"How far from Earth" is unfortunately not a well-formed question. It is just a patch of sky; it isn't any particular distance from Earth. The objects in it are a variety of distances away: see the "Scientific results" for some more details, but there is no one distance you could ascribe to the whole field. We could see if there is a plot of the redshift distribution of objects, to show the range of distances? - Parejkoj (talk) 16:00, 27 April 2021 (UTC)

Reference links

I just noticed that most of the paper references here don't have links to the actual publications, just "author, year". We should start chipping away at turning those into proper references. - Parejkoj (talk) 12:48, 28 July 2022 (UTC)