Yes, I know. I know! It seems like every other day astronomers have discovered the “oldest most distant galaxy.” Although “breaking the record” alone is of little scientific value, you’re going to be hearing a lot more of these stories in the coming years. And you know what? The science involved is still really cool.
Remember the Hubble Ultra Deep Field? The deep, mind blowing, time-traveling expanse of galaxies that reminds us of how truly itty-bitty we all are? Well, it still keeps providing astronomers with new objects of study with more observations.
The new observing campaign with Wide Field Camera 3 on Hubble finished up last September. The goal was to find more galaxies in the redshift range of 8.5 to 10, a crucial but understudied time in galaxy formation. In more tangible numbers, according to my favorite cosmology calculator, that is when the Universe was about 500 million years old, a mere fraction of its current 13.75 billion years.
Just stop for a moment and process that this camera detected photons from over 13 BILLION light years away. Yes, that’s really far.
This is a time in the universe when the very first galaxies were forming. Little is known about this epoch, but our telescopes and techniques getting better and better, allowing us to probe this period of creation a little more every year. When the James Webb Space Telescope* (JWST) launches, it will further open up these proto-galaxies to our explorations with a large mirror deployed away from the distorting effects of the Earth’s atmosphere and with sensitivity to infrared light. Since these baby galaxies are so heavily redshifted by the expansion of the universe over such great distances, infrared is the best way to study them.
In this new image (top), seven such distant galaxies were identified, including one that had tentatively been announced with a redshift of 10.3 and now has a tentative redshift of 11.9, making it the new record-holder, pending confirmation. Though seven is not a large sample by any means, it at least allows us to put the first data points on a plot describing this sample. It appears as though, when you go further back in time to this epoch, that the brightness and star formation rate of these galaxies drop off a bit, as if this were just a period of “ramping up” before the fireworks really began.
These galaxies would have been emitting ultraviolet light that ionized the hydrogen gas that pervaded the Universe at this early time. That means the ultraviolet photons would cause the electron to be stripped from a hydrogen atom. Much effort has been put into detecting this neutral hydrogen and studying its ionization with low frequency radio telescopes.
Having worked on such a project for my graduate dissertation, I think we’re getting closer to that first detection as well, and astronomers can put these different pieces of the puzzle of early galaxy formation together before JWST even begins its mission.
We have an all too human obsession with things being the “-est” of something. If this is what it takes to get attention, I’m okay with that, as long as you stick around long enough to find out why this can produce some pretty amazing science about the very origins of everything in the Universe.
Image Credit: NASA, ESA, R. Ellis (Caltech), and the HUDF 2012 Team
* a.k.a. “Jim the Telescope” as it is called around my office.