Hello Space Fans and welcome to another edition of Space Fan News.
Well folks, it appears we have a new record for the most distant galaxy every seen.
This week, astronomers using the Hubble Space Telescope announced that they have found seven
primitive galaxies that formed more than 13 billion years ago, when the universe was less
than 3 percent of its present age
And it looks like one of them has a redshift of z=11.9, breaking the previous record announced
a few weeks ago by the CLASH team of 10.9.
Sorry CLASH, at least you had the record for a while there.
Check out SFN 83 and our Space Fan Hangout from November 19th for more on that discovery.
The team was trying to get a handle on this thing called Cosmic Dawn, a period in our
history where galaxies began to form and strip the hydrogen gas permeating everything of
their electrons, re-ionizing them.
Astronomers have long debated whether hot stars in these early galaxies could have provided
enough radiation to warm the cold hydrogen that formed soon after the big bang.
This process, called "reionization," is thought to have occurred 200 million to a billion
years after the birth of the universe.
This process made the universe transparent to light, allowing astronomers to look far
back into time.
The galaxies in this new study are seen in this early epoch.
What's really cool about these early galaxies is they are full of the first stars to ever
form, and these stars are amazing.
They are huge, hundreds of time larger than the sun, very hot, and they live only a few
million years.
Because they're so hot, they emit a lot of ultraviolet energy so these galaxies are very
bright in the ultraviolet.
Except for one thing.
Since this light was emitted 13 billion years ago, the expansion of the universe stretched
out the wavelengths of the light from these galaxies so much that you need to look in
the infrared to see them.
One way they know how far away something is is by looking at how much the light has stretched
because it's proportional to the age of the universe.
Using filters no one's used before for this purpose, they were able to zero in on these
oldest, farthest galaxies ever and found the precise wavelength that would have caused
the hydrogen to ionize.
Boo yeah.
So how did they do all this?
They took really long exposures of the most famous area of the sky: the Ultra Deep Field
using a lot of different filters.
For over 100 hours during August and September of 2012, they took images and added them to
the previous deep field signal taken over the past decade.
These exposures were twice as long as the ones taken in 2009 and added a completely
new dimension to the Hubble Ultra Deep Field.
Did they find what they were looking for?
Well, they discovered that cosmic dawn was not a sudden event, there wasn't a sudden
explosion of star and galaxy formation rates, the process appears to be much slower, happening
over the course of hundreds of millions to a billion years.
Also, because they found seven of these galaxies, they were able to estimate a density of galaxies
during this period in the history of the universe.
Something no one has been able to do until now.
No onsies and twosies.
What they want to do next is point the Hubble at different parts of the sky and do the same
thing, to try and get even better statistics of galaxy distribution during this important
time.
I know I keep saying this, but this work really does push it for Hubble.
Finding more most distant things is coming to an end for the Hubble Space Telescope.
Unless we find a really huge galaxy cluster magnifying the crap out of some distant z=12
galaxy, we will need to wait for the James Webb Space Telescope to look at anything more
distant.
I'm holding a hangout on Tuesday at 1pm EST to discuss this result with the previous record
holder, Dr. Dan Coe along with Alberto Conti, so please join us if you can.
The link to the event is in the description box below.
Next, our Milky Way Galaxy may be more massive than we thought.
You've often heard me say that the Milky Way has hundreds of billions of stars in it and
that on average, the best way to think of the number of stars in the universe is to
say that there are about 100 billion galaxies in the universe each with about a hundred
billion stars.
Our galaxy has been around a long time, it is almost as old as the universe, and it contains
around 500 to 600 billion stars, more than the average.
Well, it looks like that is a gross underestimate.
Astronomers using the Hubble Space Telescope measured a small dwarf galaxy called Leo I,
located about 850,000 light years away and moving away from us at a very high speed,
and used its motion to deduce the mass of the Milky Way, including its dark matter halo.
Leo I is a dwarf spheroidal galaxy and the farthest of the many galaxies that are thought
to orbit ours.
Most of the Milky Way's dark matter halo should fit inside Leo I's orbit—that is, if the
dwarf galaxy is actually in orbit and not just passing by.
But the big question is, Is it in orbit?
Is Leo I gravitationally bound to our galaxy?
Well that depends on the mass of our galaxy, if the Milky Way is massive enough, then Leo
I will be in orbit, if not, it will fly away into intergalactic space.
In order to find this out, astronomers had to measure the proper motion of Leo I.
So, astronomers at the Space Telescope Science Institute used the Hubble Space Telescope
to compare Leo I's position in 2006 and 2011 with more than a hundred background galaxies.
They found that combined with the Doppler shift, the proper motion reveals that Leo
I orbits the Milky Way at 200 kilometers per second.
That's nearly as fast as the sun orbits the Milky Way's center, even though the dwarf
galaxy is much farther away.
To sustain a similar velocity at that far a distance requires a lot of extra mass.
These measurements confirm that Leo I is a proper satellite of the Milky Way - it is
bound to it gravitationally - and for that to happen, the Milky Way galaxy must weigh
as much as 1.6 Trillion Suns.
No wonder I feel so bloated lately.
Anyway, that's it for this week Space Fans, thank you for watching and, as always, Keep
Looking Up!