Not too soon to announce possible earliest galaxies known

WASHINGTON — Ecstatic astronomers are waxing poetic about a new infrared portrait of the universe recorded by the refurbished Hubble Space Telescope. And they have good reason. The image, combined with a similarly deep portrait of the same patch of sky recorded by Hubble in visible light five years earlier, reveals galaxies that are extraordinarily distant.

Because light from remote galaxies must travel for billions of years to reach Earth, the light emitted by the bodies reveals how they appeared more than 13 billion years ago, or less than a billion years after the Big Bang.

During a January 5 press briefing at the winter meeting of the American Astronomical Society, one reporter asked exactly how far back in time the Hubble images were able to see. Astronomers at the briefing said the images enabled them to see galaxies about 600 million years after the Big Bang, which is also what these researchers reported online last October (SN: 10/10/09, p. 8).

However, according to two independent online reports by the same researchers who spoke at the press briefing, a further analysis of the same images has revealed galaxies that may date back even earlier, to within 450 million years of the birth of the universe. One of the teams, led by Rychard Bouwens and Garth Illingworth of the University of California, Santa Cruz, has even submitted its paper to Nature.

Despite having posted these preliminary findings online already (Science News reported the work January 3 (SN Online: 1/3/10), both Illingworth and the leader of other team, Rogier  Windhorst  of Arizona State University in Tempe, scrupulously avoided mentioning anything during the briefing about these more remote galaxies. The candidate early galaxies could reside 150 million years closer in time to the Big Bang than the galaxies the researchers reported during the Jan. 5 briefing.

That’s not because 150 million years earlier in time isn’t significant. Like an archaeological dig looking for signs of the earliest civilization, peering farther back in time to galaxies that may hail from a slightly earlier era gets that much closer to cosmic dawn, the time when the first galaxies and stars switched on.

What’s more, finding galaxies hailing from 450 million years after the Big Bang is the very best Hubble or any other telescope now in existence can do. As a lyric from Rodgers & Hammerstein’s Oklahoma proclaims, “They’ve gone about as far as they can go.”

After years of astronomers announcing findings of the most distant galaxies known — statements frequently revised several months later — scientists truly can’t find anything more remote until the launch of Hubble’s successor, the infrared James Webb Space Telescope, in 2014.

So why not mention the new findings? It’s because the researchers from each team, while believing they have likely found galaxies that distant and far back in time, don’t agree on which galaxies fit the bill. It’s not easy finding such faint, distant bodies and the 20 or so candidates found by Windhorst’s team don’t even overlap with any of the three candidates found by Illingworth, Bouwens and their colleagues. And in its online paper, the Illingworth-Bouwens team criticize Windhorst and his colleagues

“We didn’t want to pick a fight in front of the press,” said Windhorst, who told Science News that additional analysis suggests that of his team’s 20 candidate early galaxies, perhaps 10 may turn out be truly distant.

“We don’t quite agree on the details,” Windhorst added, saying also that it’s too early to announce the work to the public. However, the teams’ online posting of their work and one team’s intent to publish those studies in a professional journal appear to tell a different story.