Hubble's New Miracle Camera

  / sciencereason   ... Hubblecast Episode 40: Wide Field Camera 3 (WFC3) - Hubble's New Miracle Camera

In early 2009, a team of astronauts visited Hubble to repair the wear and tear of twenty years of operating in a hostile environment - and to install two new instruments, the Cosmic Origins Spectrograph, and Wide Field Camera 3 - better known as WFC3.

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Wide Field Camera 3 (WFC3) is a combined ultraviolet, visible and infrared camera that dramatically extends Hubble's ability to image astronomical objects. With these new capabilities, Hubble is still pushing the boundaries of science after two decades in orbit.

In episode 30 of the Hubblecast, we saw some of the very first pictures to come back from Wide Field Camera 3, Hubble's newest and most advanced instrument. Today we're going to look at some of the science behind these pictures. We'll find out how this remarkable new camera is helping Hubble to see the invisible, look far back in time and spot objects further away from us than ever before.

WFC3 was installed on Hubble in place of WFPC2, the Wide Field and Planetary Camera 2, which for many years had been the main workhorse instrument on Hubble. Not only do the two instruments have very similar names, and look virtually identical, the capabilities of WFC3 are also in some respects just a tweaked version of those of its predecessor — although with sharper pictures and more sensitive light detectors. But on top of these incremental improvements, WFC3 also brings a whole battery of new functions to Hubble that are getting us astronomers really excited.

WFC3 is actually two instruments in one: the ultraviolet and visible-light channel is WFPC2's replacement, cramming six times as many pixels into a similar field of view. As well as providing scientists with higher resolution observations than ever before, the pictures from this part of WFC3 are also Hubble's prettiest yet, revealing details never seen before through any telescope. But it is WFC3's infrared channel that is the real breakthrough.

Infrared astronomy is getting a lot of attention right now. It's not just Hubble's new functions — ESA's Herschel Space Observatory, NASA's Spitzer Space Telescope and the forthcoming NASA/ESA/CSA James Webb Space Telescope were all designed to work in this part of the spectrum too. One of the reasons for this is that studying the sky in the infrared allows astronomers to look at relatively cool objects that emit little or no visible light. An example of these are so-called protoplanetary nebulae — a cool gas envelope that gets thrown off by a certain type of star as its nuclear fuel supply runs low.

Looking at these nebulae through an optical telescope is hard, as they barely emit any visible light, forcing astronomers to rely instead on faint reflected starlight to see anything at all. But protoplanetary nebulae shine far more brightly in the infrared part of the spectrum.

Infrared imaging is also extremely useful for peering through interstellar dust clouds, which are impenetrable to visible light. The reason for this is similar to why sunsets are red. Just as particles in the atmosphere scatter blue light more than red, interstellar dust clouds block visible light more than infrared.

Hubble has become famous for its striking visible-light pictures of huge clouds of interstellar dust and gas. But sometimes scientists want to know what's happening behind, or inside, the cloud of dust. Making infrared observations pulls away the veil and reveals the hidden stars.

Until now, infrared imaging was challenging with Hubble. The Near Infrared Camera and Multi-object Spectrometer, or NICMOS, did allow astronomers to study objects in infrared light in ways not possible from the ground, but it forced them to make a difficult choice. Because its images were small — only about 65 000 pixels in total, similar to a mobile phone screen — NICMOS could produce the sharpest images only if it concentrated on a very narrow field of view. Taking in a wider view came at the cost of losing much of the detail.

Along with a much wider field of view and better sensitivity, WFC3's infrared channel has a million pixels, 15 times better than NICMOS, and similar to what you get on a computer screen. This means astronomers no longer have to compromise between how much of the sky they can observe, and how much detail they can study it in.

These improvements mean Hubble is now far better at observing large areas of sky as well as very faint and very distant objects These are key for the science of cosmology, the study of the origins and development of the Universe.

http://www.spacetelescope.org/
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