Saturday, June 07, 2014

Hubble captures the first full-color, high-res photo of the very early universe

The early one. Earliest pictures. Cool.

NASA’s Hubble Space Telescope has captured the most colorful and detailed image of the early universe — officially dubbed the Ultra Deep Field 2014 — with galaxies that date back to just a few hundred million years after the Big Bang. While many of the blobs in the photo might look like stars, every single point of light is an entire galaxy — around 10,000 of them, in case you were wondering — each containing millions or billions of stars. The photo is the culmination of over 10 years of observations, totaling around 600 hours of exposure time, made during 841 orbits of the Earth.

If the Ultra Deep Field (UDF) looks familiar, it’s because you’ve seen its predecessor, the Hubble Extreme Deep Field (XDF). Both images are of the exact same (tiny) piece of night sky in the southern hemisphere’s Fornax constellation. The UDF is actually very similar, and uses much of the same imagery that was composited to create the XDF, but with one very interesting addition: Ultraviolet light.

Basically, Hubble has a number of imaging devices (cameras) that are specifically tailored towards a specific task or spectrum of light. The previous image, the XDF, only used visible and infrared imagery captured by Hubble’s ACS Wide Field Channel and newer Wide Field Camera 3′s IR sensor. The new UDF photo, however, also includes imagery from the WFC3′s 16-megapixel ultraviolet CCD. In scientific terms, light spectrum captured by the original XDF ranges from 350nm to 1700nm, while the UDF is from 200nm to 1700nm.

The Hubble XDF from 2012 (left) vs. the Hubble UDF (right). As you can see, the UDF is more colorful and detailed. Full-size images of the UDF are available from the Hubble website.

What does that extra 150nm of ultraviolet light get you? Quite a lot, according to Hubble’s crack team of astronomers. Ultraviolet light is primarily produced by the hottest, largest, and youngest stars. Without UV, the astronomers were unable to accurately work out which galaxies were forming the most stars — which, when you’re looking at a photo that chronicles a period just a few million years after the Big Bang, is pretty vital information. “The lack of information from ultraviolet light made studying galaxies [in the XDF] like trying to understand the history of families without knowing about the grade-school children,” says principal investigator Harry Teplitz of Caltech in Pasadena, California. “The addition of the ultraviolet fills in this missing range.”

Hubble’s new-found ability to capture UV light (it was only enabled by the 2009 delivery of the WFC3 by Space Shuttle Atlantis) is unique, as far as space telescopes go. Even when Hubble’s successor, the James Web Space Telescope (JWST) is launched, astronomers will still rely on Hubble’s UV imaging chops (JWST will only capture infrared light, with the hope of capturing a glimmer of light from the universe’s first stars).

The Hubble UDF covers just a tiny patch of the night sky. (The XDF and UDF are of the same patch of sky.)

As an addendum — just to make you appreciate just how vast the universe is — check out the photo above. The entire UDF is captured from that tiny little box in the sky. If you hold your hand out at arm’s length, that box is about the width of half a finger. To the naked eye, that patch of sky would look completely empty — the faintest galaxies in the UDF just one ten-billionth of the brightness that your eyes can perceive. That patch of sky isn’t unique or anything: If you take any “empty” patch of sky, there are actually thousands of galaxies hiding there. Multiply that by the massive expanse of the night sky, and the fact that an average galaxy contains 500 billion stars, and you begin to comprehend just how insanely vast the universe is.

Source: ExtremeTech

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