Finding something unexpected adds immeasurably to the pleasure of doing science. Yesterday we looked at an anomalous transient in Boötes, one that has already spawned a number of theories to explain it. Today let’s look at some of the radio noise that pervades the cosmos, and an intriguing experiment that discovered more of it than expected. The story makes this writer marvel again at how the universe continues to change the game. I like how Philip M. Lubin (UCSB) puts it:
“It seems as though we live in a darkened room and every time we turn the lights on and explore, we find something new. The universe continues to amaze us and provide us with new mysteries. It is like a large puzzle that we are slowly given pieces to so that we can eventually see through the fog of our confusion.”
Indeed. Lubin is on the team behind the NASA balloon-borne experiment called ARCADE (Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission), which discovered this particular static back in 2006. Like all but one of the stories we’ve considered this week, this one grows out of material presented at the AAS meeting in Long Beach, a conclave that has been unusually productive this time around. Productive, that is, if publicizing unusual results inspires scientists to renewed efforts to explain them and focuses further research on the question.
You could combine the radio emissions from all the radio galaxies in the universe and it would not be enough to equal the noise found by ARCADE. Known radio sources of all kinds simply don’t explain it, nor does an origin in primordial stars. Indeed, the potential signature of the very first stars is more or less masked by the unexpectedly loud noise, complicating our plans to study it. What astronomers now hope is that the cosmic static may offer clues to the development of galaxies in a later epoch, information that would help us understand early radio sources.
All told, four papers have been offered to the Astrophysical Journal on these findings in addition to the AAS presentation, and according to this New York Times story, the discovery team has not ruled out the idea that the signal comes from black holes produced by the earliest stars. But that’s a longshot, as Alan Kogut (NASA GSFC) is quick to note: “I emphasize that this interpretation is just speculation at present — no one has yet done any real calculations to see if this holds up under closer scrutiny or not.”
That’s a valuable reminder of scientific method at work, as results are presented through meetings and journals and widely discussed and critiqued. Findings this odd may take quite a while to sort out, but they’re a spur toward putting more brain power onto the question. We get such surprises because of new instrumentation — in this case, the wavelength in question has simply not been well studied until ARCADE, falling as it does between the range examined by Earth-based radio telescopes and the shorter wavelengths that are the domain of satellites like COBE, the Cosmic Background Explorer.
We have a long way to go here, but it’s remarkable that we’re pushing back the frontiers of study past so-called Population II stars, which are older than our Sun and poorly endowed with metals, into the hypothetical Population III, the earliest stars, formed from pure hydrogen and helium. Studying the latter has been rendered considerably more tricky by these results, but a new phenomenon may be emerging whose uses have yet to be determined. As I’ve opined before, what a time to be studying cosmology!
Among the papers submitted to the Astrophysical Journal, you might want to begin with Kogut et al., “ARCADE 2 Observations of Galactic Radio Emission” (available online). You can run a search on the arXiv site for the accompanying work, including a description of the ARCADE instrument. NASA GSFC offers a news release.