Two venerable space telescopes, the Hubble and the Spitzer, have teamed up to study the very early universe, and here’s what they see at the cosmic dawn – a wild and woolly party, with brilliant blue stars that aren’t ready to settle down into anything so structured as a conventional spiral galaxy.
Instead, the early years of the universe featured a profusion of small, irregular, blobby galaxies that were popping with big, hot, super-luminous stars forming at a furious rate. Galaxies were colliding all over the place.
Ray Villard, a spokesman for the Space Telescope Science Institute, which conducts Hubble research for Nasa, said it’s like seeing the finale of a fireworks show, just that it’s close to the beginning of time.
The new results and images of the early cosmos were released on Tuesday at the annual meeting of the American Astronomical Society at National Harbor, Maryland.
This is not the first time that the Hubble, in its third decade of operation, has taken a “deep-field” look at the universe, training its gaze on a tiny spot and holding it there to collect the ancient light. But a new observation campaign, dubbed the Frontier Fields, supplements Hubble time with data from the Spitzer, which observes in infrared, and another space telescope, the Chandra X-ray Observatory.
The new campaign exploits a phenomenon known as gravitational lensing. This is an opportunistic manoeuvre that draws inspiration from Albert Einstein’s general theory of relativity, which describes how gravity curves the fabric of space and time.
In the foreground of one new image is a galaxy cluster named Abell 2744, containing hundreds of galaxies. “Foreground” is perhaps an imperfect term given that these galaxies are 3.5 billion light-years away – it has taken 3.5 billion years for the light to reach the Hubble. The gravity of the clustered galaxies creates a lensing effect that magnifies thousands of galaxies that are far in the background – some of them 12 billion light-years away, having emitted that light in the very earliest era of galaxy formation.
“Light following a path around those clusters is bent,” says Jennifer Lotz, an astronomer at the Space Telescope Science Institute.
The initial expansion of the universe, known as the Big Bang, happened about 13.7 billion years ago, a measurement that has become more precise in the past few years with new data from space telescopes. Theorists believe it took about 400 million years for the first stars to ignite and the first galaxies to form. The Hubble can’t see quite that deeply in time and space, but the earliest galaxy-forming epoch is a target for Nasa’s James Webb Space Telescope, scheduled for launch in 2018.
The universe in its youth was going through a blue period, because the stars were blue, just like the young, hot stars we see in the constellation Orion, said Garth Illingworth, professor of astronomy at the University of California at Santa Cruz and one of the scientists involved in the research.
In telescopes, these young galaxies look red, because their light has been stretched out – red-shifted – over billions of years. “In reality, if you go there, it’s all blue,” Illingworth said.
If you could have parked yourself in that young universe, you would have seen those blue galaxies all around, many as big as our moon, Illingworth said. But you couldn’t go for a star-gazing stroll, because there were no planets then. The matter in the cosmos was mostly hydrogen, with a smidgen of helium and hardly any atoms larger than that.
“It was much, much wilder than what we see today,” said Anahita Alavi, an astronomy student at the University of California at Riverside. “Everything was closer together. The possibility of these galaxies colliding with each other, and merging with each other, was higher.”
Star formation picked up speed for several billion years. But then, about 9 billion years ago, the situation calmed down markedly and became more organised. Stars formed at a slower rate. The expanding universe became home to billions of majestic spiral and elliptical galaxies – and, on one rock at least, to astronomers staring into the night sky.
The Washington Post