On Wednesday, January 26th, NASA will hold a press conference to announce a new discovery by researchers using the Hubble Space Telescope. What might that announcement contain?
There are a few clues. NASA has said that “Astronomers have pushed the Hubble Space Telescope to its limits and have seen further back in time than ever before.” They have also given the names of the participants in the conference. I don’t think I’ll be going too far out on a limb to speculate about the nature of their discovery.
Garth Illingworth and Rychard Bouwens investigate galaxies that are as far out as we can see. One of the most fundamental tenets of modern astronomy is that objects distant from us in space are equally distant from us in time. When we see objects that are billions of light years distant, we are seeing them as they were billions of years ago. A telescope is essentially a time machine, and very powerful ones like the Hubble can reach back to the very earliest epochs of the universe’s 13.75 billion-year history. Dr. Bouwens has a very nice web site here talking about his work with these first galaxies.
A very quick summary of some of those early epochs:
• After the Big Bang, the expanding universe is so hot that its matter is ionized. Electrons are too energetic to settle down and combine with atomic nuclei, and these free electrons scatter light willy-nilly in all directions. As a result, the universe is opaque.
• About 380,000 years after the Big Bang, the universe has cooled enough for electrons to recombine with nuclei to form neutral atoms (mostly hydrogen). Light is now free to move through space unimpeded, and the universe is now transparent. The light from this era of recombination is what we see as the cosmic microwave background radiation.
• There follows a period known as the “dark ages,” because there is no source of light other than the fading cosmic background radiation. Over time, clumps of slightly denser matter grow and eventually become dense enough to ignite nuclear reactions at their cores—the first stars are born. The time for this era of reionization is thought to be around 500 million years after the Big Bang, or to put it another way, when the universe was less than 4% of its current age.
So what am I betting on? It is that Drs. Illingworth and Bouwens have reached all the way back to this early era to see one of the very first galaxies, containing some of the very first stars. This would be a remarkable achievement, and would be possible only because of the newly refurbished Hubble instruments installed by Space Shuttle astronauts in 2009.
And of course I could be wrong! In any case, we shall soon know.