Space Fan News #78: Hubble's eXtreme Deep Field; The Farthest Galaxy Ever Seen

Uploaded by tdarnell on 28.09.2012

Hello Space Fans and welcome to another edition of Space Fan News.
Deep News Everyone!
(Don't worry, I'm not gonna do that every time, but these last two Space Fan News have
lent themselves very nicely to some Professor Farnsworth love. I won't do that again - for
a while anyway…)
This week astronomers using the Hubble Space Telescope have released humanity's deepest
look into the universe so far.
Called the eXtreme Deep Field, this image represents the farthest we've ever seen into
the universe and builds on previous work done in 2003 and 2009, when the last farthest we've
ever seen image was released, the Ultra Deep Field.
So the chronology goes something like this.
Back in 2003, the Ultra Deep Field was taken in a very tiny section of sky located in the
Constellation Fornax. The image was taken using the Advanced Camera for Surveys (or
ACS) and this image marked the deepest we could hope to see in the visible light part
of the spectrum.
Later, back in 2008, they replaced the ACS with a camera that could see in the infrared,
called the Wide Field Camera three of WFC3, and took another image in the same spot in
the sky.
This time, they saw galaxies even further back in time, we could see galaxies that were
around less than one billion years after the Big Bang.
The eXtreme Deep Field builds on the visible light image and the subsequent IR image by
looking again at the same area of sky but this time using more data from the WFC3.
The WFC3 field of view is a bit smaller than the camera used to take the Ultra Deep Field
in 2004, but because it can see a bit farther back in time than the ACS, it added the more
galaxies to it.
Here's how they made it.
First they downloaded about 250 gigabytes of data from the Hubble archive.
Then they processed it and constructed the image.
Starting with the original Ultra Deep Field taken in 2004, which was primarily in visible
light, they added to that the data from the WFC3 taken in 2009.
Then they gather all available data taken since then from that area of the sky and constructed
the XDF from all data in the orange square you see here.
According to the press release, there are around 5,500 galaxies in the eXtreme deep
field. What's not clear to me is I understood the Ultra Deep Field from 2009 had about ten
thousand galaxies in it, so I don't know if the 5,500 galaxies in the XDF is in addition
to those or it that's a total in the smaller field of view.
Here's how much of the sky the eXtreme Deep Field covers. As you can see this is a tiny
fraction of the sky, roughly one-thirty millionths of it. If there are 5,500 galaxies in that
tiny region, imagine how many are in the entire sky.
Galaxies that that existed earlier than 800 million years after the Big Bang are only
visible to us in Infrared Light, which is why I keep harping on how important the infrared
The future of astronomy is in the infrared because it is the only way we can see our
distant past.
The eXtreme Deep Field shows us, for the first time, light from galaxies that left when the
universe was less than 800 million years old. This is the farthest we can see using the
Hubble Space Telescope, to see anything further away, we will have to wait for the James Webb
Space Telescope.
So this will be the last deep field I show you for a while Space Fans. Still, you know
a space video about this is coming, don't you?
Next, now don't get mad. I know I just told you that Hubble has maxed itself out with
the eXtreme Deep Field, that it can't see any farther back than about 800 million years
after the big Bang, but earlier this month astronomers using both the Spitzer and Hubble
Space Telescopes have detected a galaxy whose light left it when the universe was only 500
million years old.
I know, I know. So what up Mr. Space Man?
Well Hubble was only able to see this galaxy with some help from our old friend gravitational
The eXtreme deep field I just showed you went back to about 800 million years after the
Big Bang, but because the light from some distant galaxies can be magnified by the gravity
of any massive objects in between us and the distant galaxy, sometimes we can see a bit
farther back.
For example, if a giant galaxy cluster is in between us and a way far off distant galaxy
in the early universe, the gravity from all those galaxies in the cluster can act as a
lens and magnify the feeble light from distant, dim galaxies just enough that we can catch
a glimpse of it.
And that's just what happened here.
Astronomers observing the galaxy cluster known as MACS J1149+2223 detected a galaxy whose
light left when the universe was only 500 million years old.
According to Wei Zhang, a principal research scientist in the department of physics and
astronomy at Johns Hopkins University,
"This galaxy is the most distant object we have ever observed with high confidence"
This galaxy has a redshift of z=9.6 and existed in an epoch of the universe known as the Dark
Ages. This was a time when the universe was just starting to create stars and went from
a dark, starless expanse to a recognizable cosmos full of galaxies.
Unlike previous detections of galaxies in this age range, which were only observed in
a single waveband, this galaxy has been seen in five different wavelengths .
As part of the CLASH Survey, or Cluster Lensing And Supernova Survey, the Hubble Space Telescope
saw it in four visible and infrared wavelength bands.
And Spitzer measured it in a fifth, even longer-wavelength infrared band, which placed the discovery
on very firm ground.
As I said in the last segment, the XDF reached Hubble's limit to how far back it could see,
at about 800 million years after the Big Bang. But using our old friend gravitational lensing,
sometimes we get lucky and these cosmic lenses let us see just a little farther back.
Well, that's it for this week Space Fans, thank you for watching, and as always, Keep
Looking Up.