You Want Old? WC Has Old


It’s been a long time since WC wallowed in pure science geekery. And what better excuse than the discovery of GN-z11?

What? You haven’t heard of GN-z11? It’s only the oldest thing there is. So far, at least.

(Not a Selfie)

(Not a Selfie)

Remember that light, in a vacuum, never travels faster than 186,000 miles per second. So when astronomers look at any distant star or galaxy, they are actually looking into the past. The further away something is, the further it is in the past. When astronomers look at Alpha Centauri, the nearest star at 4.37 lightyears away, by definition they are looking 4.37 years into the past. They are seeing it as it was 4.37 years ago, not as it is now. It’s Alpha Centauri in December 2012.

GN-z11is estimated to be about 13.4 billion light years away. That means it is 13.4 billion years old.1 When we look at it, we are looking 13.4 billion years in the past. The universe itself is currently estimated to be 13.8 billion years old.2 That’s 13,800,000,000 years, measured from the Big Bang. If GN-z11 is  13.4 billion years old, that means it came in to existence just 400 million years after the Big Bang. The Universe was only about three percent of its current age. When astronomers look at GN-z11, they are looking at the cosmos in virtual diapers.

Using the Spitzer infrared telescope and Hubble telescope, the astronomers were able to determine that GN-z11 is very bright and large for its age. They estimate that the average stellar age of the stars that made up galaxy GN-z11 is only 40 million years, and yet it already has about a billion times the Sun’s mass worth of stars. It also appears to have been forming stars at a rapid pace. Galaxies that big were forming – stars were forming! – that far back? Who knew?

Those results make it clear that star and galaxy formation was already very active very early in the history of the cosmos, and a relatively short time after the Big Bang. A lot of scientists thought the universe back then was just a hot soup of atomic hydrogen. GN-z11 has sent a lot of theoretical physicists back to their computer models.

We could get even more geeky, and talk about the very cool hydrogen ionization effect on light, and the complications introduced by red-shifting of distant objects, and the impressive evidence backing up the age-dating of GN-z!11. But if you want the technogeekery, read the paper.

Refining the observations more will have to wait on the launch of the James Webb Space Telescope in 2018, which is designed to image a bit deeper into the infrared. WC suspects what one of the early targets of the Webb Space Telescope will be.

 


  1. By contrast, planet earth is just 4.5 billion years old. Technically, 4.54 ± 0.05 billion years (4.54 × 109 years ± 1%). 
  2.  13.799±0.021 billion years ((13.799±0.021)×109 years. 
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