800,000 million light years?

I was surprised to hear and see "The Sky at Night" referring to the
galaxies in the Hubble Ultra Deep Field as being 800,000 million light
years away.
Where do they get that figure?
--
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I'm not sure if the number is right or not (have not seen the program
yet - the idea of the UDF was to identify galaxies at ages of 400 -
800 millions years after the big bang), but the instruments used
included a spectroscope to measure the redshift from which the
distance (and age) is inferred.

read more at:

http://hubblesite.org/newscenter/new.../2004/07/text/

Cheers, Callum
I was surprised to hear and see "The Sky at Night" referring to the
galaxies in the Hubble Ultra Deep Field as being 800,000 million light
years away.
Where do they get that figure?

Jonathan Silverlight wrote in message ...
I was surprised to hear and see "The Sky at Night" referring to the
galaxies in the Hubble Ultra Deep Field as being 800,000 million light
years away.
Where do they get that figure?
Hi,
I may be completely wrong here....but if the age of the known universe
is currently considered to be about 13-15 billion years, then I would
think that the distance to the most distant galaxies could not be more
than 13-15 billion light years. Therefore the quoted figure from
"TSAN" of 800 billion light years is surely wrong ? [No critism of
either the poster or the program, just my observation]
Regards
Andrew

"callum" wrote in message
om...
I'm not sure if the number is right or not (have not seen the program
yet - the idea of the UDF was to identify galaxies at ages of 400 -
800 millions years after the big bang), but the instruments used
included a spectroscope to measure the redshift from which the
distance (and age) is inferred.

read more at:

http://hubblesite.org/newscenter/new.../2004/07/text/

Cheers, Callum
I was surprised to hear and see "The Sky at Night" referring to the
galaxies in the Hubble Ultra Deep Field as being 800,000 million light
years away.
Where do they get that figure?

The "distance" sounds wrong to me.

Just to note that they did not actually obtain spectra, but used the
infrared capability of the NICMOS to get one of the images in the near-IR.
Any galaxy that showed up only in the reddest image will be at a redshift of
7-12. The reason is that hydrogen absorbs all the emitted UV light up to
about 95 nm (950A), and at redshift 10 the only light getting to us is in
the longest wavelength of the image.

--
Mike Dworetsky

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JRS: In article , seen in
news:uk.sci.astronomy, Jonathan Silverlight
snet.co.uk.invalid posted at Mon, 5 Apr 2004 20:59:55 :
I was surprised to hear and see "The Sky at Night" referring to the
galaxies in the Hubble Ultra Deep Field as being 800,000 million light
years away.
Where do they get that figure?

Simple incompetence, ignorance, or carelessness is enough to explain it.
Either you heard/saw it wrong, which seems implausible, or at some stage
in the production of the program someone made a mistake (forgiveable)
which no-one noticed (inexcusable).

Google or news archives should give the proper figure for the HUDF
distance; my own memory is unconvincing, but could agree with 8,000
million LY (the Hubble Constant is AIUI about 14,000 million years).

Perhaps some incompletely numerate member of the production staff
dictated "Eight hundred err thousand million", and never checked the
result.

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Web URL:http://www.merlyn.demon.co.uk/ - FAQqish topics, acronyms & links;
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"Dr John Stockton" wrote in message
...
JRS: In article , seen in
news:uk.sci.astronomy, Jonathan Silverlight
snet.co.uk.invalid posted at Mon, 5 Apr 2004 20:59:55 :
I was surprised to hear and see "The Sky at Night" referring to the
galaxies in the Hubble Ultra Deep Field as being 800,000 million light
years away.
Where do they get that figure?

Simple incompetence, ignorance, or carelessness is enough to explain it.
Either you heard/saw it wrong, which seems implausible, or at some stage
in the production of the program someone made a mistake (forgiveable)
which no-one noticed (inexcusable).

Google or news archives should give the proper figure for the HUDF
distance; my own memory is unconvincing, but could agree with 8,000
million LY (the Hubble Constant is AIUI about 14,000 million years).

Perhaps some incompletely numerate member of the production staff
dictated "Eight hundred err thousand million", and never checked the
result.


Just multiplying the Hubble linear formula v = Hr for redshift of z = 10
gives v = 3,000,000 km/s and with H = 72 km/s/Mpc I get something like
135,000 MLY. So maybe the number given is of the right order of magnitude
for the "linear" distance "now". The linear formula does not really apply.
Distance and time are somewhat slippery notions when discussing cosmology.
The co-moving distance (where it would be "now") is about 32,000 MLY for z =
10.

--
Mike Dworetsky

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