ESA : ESA to present the latest Venus Express results to the media

Artist's view of Venus Express at Venus

20 November 2007
ESA PR 33-2007. How has our knowledge of Venus evolved since ESA’s Venus Express spacecraft has been observing Earth’s twin? To answer this question and to present fresh new results concerning our cryptic neighbour, the European Space Agency is inviting the media to attend a press conference to be held at ESA Headquarters in Paris on 28 November.

The launch of Venus Express back in November 2005 represented a major milestone in the exploration of Venus — a planet unvisited by any dedicated spacecraft since the early 1990s.

One of the fundamental questions being addressed by the Venus Express mission is why a world so similar to Earth in mass and size has evolved so differently, to become the noxious and inhospitable planet it is today.

Since it started its scientific observations in July 2006, Venus Express has been making the most detailed study of the planet’s thick and complex atmosphere to date.

The latest findings not only highlight the features that make Venus unique in the solar system but also provide fresh clues as to how the planet is — despite everything — a more Earth-like planetary neighbour than one could have imagined.

The results will appear in a special section of the 29 November issue of the journal Nature containing nine individual papers devoted to Venus Express science activities.

Media organisations interested in attending the press conference are invited to register via the attached form. Media that cannot attend will have the opportunity to follow the press conference via the following phone line: +33 1 58 99 57 42 (listening-mode only).

The results presented at the press conference are embargoed until 28 November 19:00 CET.

Space.com : Nature vs. Nurture in the Cosmos

By Jeanna Bryner Staff Writer posted: 19 November 2007 06:17 am ET

The discovery of "teenage" galaxies is giving scientists a better handle on how galaxies transform from sexy, spiral star factories to shapeless retirement homes for old stars.

In the early 1900s Edwin Hubble discovered that the Milky Way galaxy is not alone. Our galaxy is just one of many "island universes," as Hubble dubbed them, swimming in the vast sea of space.

Now that astronomers can measure the age of each galaxy, its star-making activity and other related data, they are piecing together an understanding that galaxies grow gradually like children, gliding through their visibly different teen years before reaching adulthood.

Results being published in a December issue of the Astrophysical Journal provide the strongest evidence yet for this thinking, called nurture theory, in which the elegant spirals (young galaxies) and blob-like ellipticals (old galaxies) are evolutionarily linked.

Color-coded

Scientists have long thought that young galaxies grow up into old ones, referred to as blue and red galaxies, respectively. The color indicates how actively the galaxy is churning out new stars. Younger stars shine in ultraviolet or blue light, and so galaxies bustling with star-making activity appear blue. Older stars emit infrared or red light. In aging galaxies, their "stellar reproductive" capacity has begun to shut down and so the remaining stars are just hanging out for the remainder of their lives.

About half of all galaxies are blue and half are red. It had been postulated that the two are linked, with the blue young'uns running out of star-making material and maturing into passive red galaxies.

If this theory holds true, you'd expect to see a population of "teenage" galaxies in the process of transitioning from young to old. Finding these teens is tricky though, because the cosmic change occurs over billions of years.

"The nurture theory of galaxy evolution predicted that there would be galaxies in transition," said lead author Christopher Martin, principal investigator for NASA's Galaxy Evolution Explorer (GALEX) mission at Caltech in Pasadena, Calif. "Finding these galaxies required ultraviolet light, because they really stand out at this wavelength."

Cosmic history

Data from GALEX, launched in 2003, allowed Martin and his colleagues to observe galaxies in ultraviolet light across 10 billion years of cosmic history. The researchers' analysis of tens of thousands of images taken by GALEX has revealed that young, spiral galaxies do in fact first mature into "teens" before winding down into their elderly ellipses.

The details of the picture now emerging suggest that a spiral galaxy might merge with another spiral or perhaps an irregularly shaped galaxy before churning out a few bursts of newly minted stars. Eventually, the galaxy begins to exhaust its star production and settles into later life as an elliptical.

"Our data confirm that all galaxies begin life forming stars," Martin said. "Then through a combination of mergers, fuel exhaustion and perhaps suppression by black holes, the galaxies eventually stop producing stars."

The findings also suggest that some young galaxies waltz into old age quickly, while others leisurely stroll into their golden years.