Hubble’s billion-year review
This article was originally on a blog post platform and may be missing photos, graphics or links. See About archive blog posts.
To kick off 2009, I decided to look backward -- a couple billion years backward -- by spending time with National Geographic’s ‘Hubble: Imaging Space and Time.’ The 224-page book has more than 200 photographs from the orbiting Hubble Space Telescope (with the help of a few terrestrial telescopes along the way). The pictures aren’t just of galaxies very far away; they’re from a long, long time ago too. Authors David Devorkin and Robert Smith explain:
Telescopes are time machines: They allow us to see back in time as well as out into space. Light travels at around 186,000 miles per second, and so when we look at the moon, the light we see has taken over a second to reach us. The light we see from our nearest star, the sun, left that body over eight minutes ago. On clear fall evenings, high in the sky in the constellation of Andromeda, is a faint smudge of light known as the Andromeda Nebula. This is in fact a galaxy, very close to our Milky Way in cosmic terms; even so, light from Andromeda takes around 2.5 million years to cover the distance to us. We are seeing Andromeda as it existed 2.5 million years ago.
The Hubble images go back much further than that; the Hubble Deep Field, which describes a set of 300 exposures taken in 1995, captures galaxies 2.5 to 10.5 billion light years away. 10.5 billion light years. When I hold the book in my lap, I’m looking at snapshots of light that was emitted before the Earth was formed. It’s mind-boggling.
It’s also beautiful. Some of the brilliant colors are natural, while others are the result of filters that help clarify what’s being seen. The colors often reveal the invisible, chemical elements or spectra that our eyes would not detect. Many of the images are composites made from multiple exposures. ‘Hubble images should not be compared to our visual experience,’ the authors caution. What appears on these pages is art as well as science. Like the above photo of the Carina Nebula, which was ‘imaged’ in 2007 to celebrate the 17th anniversary of Hubble.
Covering an area 50 light-years wide, this mosaic includes the slow Nova Eta Carinae at the far left. ... This huge star-forming region contains at least a dozen stars between 50 and 100 times the mass of the sun. In addition to intense ultraviolet radiation, such stars give off very active stellar winds consisting of highly charged particles. These forces push the gas and dust in the cloud complex into contorted bubbles, streamers, walls, and knots and lead to the accelerated production of new highly massive stars.
There is plenty of layperson-friendly text like this to explain the images. The book also includes information about Hubble the telescope and Hubble, Edwin, the astronomer for whom it was named.
Many of the images are available in the galleries of the Hubble website, but the book, with its oversize square format -- which matches the Hubble images -- is nevertheless spectacular.
-- Carolyn Kellogg
