Posted on July 19th, 2012

Out of this World – GALEX

I’m sure you’ve lent someone a pencil or your car at some point in your life, hoping you’d get it back in decent shape. You might have even let someone use your house on occasion, that’s quite the responsibility, but imagine lending somebody a satellite. That’s exactly what NASA has done with the Galaxy Evolution Explorer (GALEX). NASA has handed over GALEX to the California Institute of Technology (Caltech) in Pasadena. A Space Act Agreement was signed on May 14, 2012 that allows the university to resume spacecraft operations using private funds. This agreement is the first of its kind, lending a federally funded space telescope to a privately funded program in order continue the mission.

Andromeda (1)

Above is a color composite of our nearest galactic neighbor, the Andromeda Galaxy. The blue represents the far-ultraviolet light and the orange is near-ultraviolet light. The central region of the galaxy harbors cooler, old stars while the smoky rings cocoon new, hotter stars. These rings lead astronomers to believe that it had previously collided with another neighboring galaxy. (Image Credit: NASA/JPL-Caltech)


When one thinks of evolution, invariably Darwin comes to mind, but what about galactic evolution? How are stars and galaxies formed? Where do they begin and where do they end? This is the mission of the GALEX telescope. It was launched on April 28th, 2003 and has peered into the cosmos ever since. GALEX is an orbiting space telescope that collects data in the far and near ultraviolet portions of the electromagnetic spectrum. The most significant discovery made by GALEX is the missing link in galaxy evolution. Observations from the telescope found the link between spiral and elliptical galaxies. Before GALEX was operational, there were very few examples of transitional galaxies moving from a younger spiral that still makes stars and gives off more ultraviolet light, to an elliptical galaxy that no longer forms stars and now emits red light. GALEX was able to find galaxies that emitted lower levels of ultraviolet light, formed fewer stars and were transitioning to what is called a ‘red and dead’ galaxy.


Galaxies are believed to transition from spirals to ellipses, above are examples of galaxies from each stage of life. (Image Credit: NASA)

Observations from GALEX have also aided scientists in understanding the basic structures of the Universe and how they change over time. The telescope tracks star formation from their origins and performs an all-sky survey, giving scientists a map of galaxies that are still forming. GALEX has probably raised more questions than it has answered, such as: Can an aged galaxy with giant ultraviolet rings be rejuvenated and start forming stars again?


Above is an image of galaxy M83, the blue and green areas are observations from GALEX showing the stars at the outskirts of the galaxy. The red extended arms show radio emissions from its gaseous hydrogen atoms. (Image Credit: NASA/JPL-Caltech/VLA/MPIA)


GALEX is also shattering long-held celestial theories – for instance, that for every large, visible star in a galaxy, there are only a hand-full of smaller stars that are not readily visible. The GALEX ultraviolet detector can sense these smaller stars more accurately then with optical images; and it was discovered that what was once believed to be a few large stars and some smaller stars, was actually fewer large stars and many more smaller stars. GALEX has spotted stars that haven’t been seen before, along with the formation of new stars 140,000 light years from the center of galaxies, once believed to be a dead zone for star formation. It has also detected an ultraviolet flash as a dying star erupts in a supernova explosion, giving scientists a glimpse into the death throes of a star.

GALEX has long outlived its original mission timeframe of 29 months and NASA continued the mission until now. By handing over the operation to Caltech, the telescope can maintain its mission objectives while NASA focuses its energy and funding elsewhere.

Katie Nelson

Geospatial Ninja

(303) 718-7163

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