Astro Bob blog: Panning for galactic goldEuropean astronomers dig deeper to uncover more galaxies than you can imagine. See the Envisat satellite near the Big Dipper tonight. A fast-growing sunspot group worth watching.
By: Bob King, Duluth News Tribune
Panning for galactic gold
This photo of a field of distant galaxies is a small portion of a much larger composite image taken by two of the four telescopes comprising the European Southern Observatory's VLT(Very Large Telescope). Each scope has a light-gathering mirror 323 inches across. Almost every single spot in the picture is a galaxy. Credit:ESO/M.Hayes
The European Southern Observatory based in Chile has been busy lately panning for galactic gold in the far reaches of the universe. To uncover the most distant galaxies astronomers use filters and special cameras that concentrate the light from newly formed stars and star clusters in the universe's youngest and therefore most distant galaxies. Astronomers have suspected for some time that despite its usefulness in ferreting out faraway galaxies, much of the specific type of light sought after gets trapped by the gas and dust clouds within the galaxies. Because of this, astronomers estimate that 90 percent of remote galaxies (around 10 billion light years distant) haven't even been touched in deep surveys of the sky.
Would a different "flavor" of light penetrate the dust better? Using a newly-developed camera, a team of astronomers are now taking deep photos with the VLT in the red light emitted by hydrogen gas called H-alpha and yes, finding oodles more distant galaxies. Two cameras were used to make the photo above: one that photographed the galaxies in the original flavor of light called Lyman-alpha and another the new way in H-alpha. Combined, they show the thousands of galaxies that saturate every niche of sky.
Above is a video pan of the entire VLT photo.
Both Lyman-alpha and H-alpha, despite their obscure sounding names, are two of hydrogen's characteristic fingerprints. When a hydrogen atom returns to its rest or ground state after getting energized by an outside source it can shoot off a photon of ultraviolet light. This is the Lyman-alpha light "fingerprint" and the traditional light astronomers look for when doing surveys of distant galaxies. Hydrogen can also emit a photon of deep red light called H-alpha after settling back to its rest state. Scientists build filters and cameras that isolate each of these wavelengths of light and then take very long exposures that uncover the incredible number of galaxies out there. In tomorrow's blog we'll look at how the fingerprints of atoms reveal what was once thought impossible to know -- the composition of the most distant stars and nebulas.
The path of Envisat tonight as seen from the Duluth, Minn. region tonight (Thursday). The satellite will first become visible when it leaves the Earth's shadow at 10:21 p.m. Central time just below the Bowl of the Big Dipper. From there it heads down toward the northwestern horizon. Created with Stellarium
I have to admit that I miss the space station when it finishes up a round of passes in the evening sky as happened recently. Of course there are other satellites that criss cross the night sky all the time even if they lack the showiness of the ISS. One of them is Europe's Envisat (Environmental Satellite) which orbits at around 495 miles high, more than twice the altitude of the space station. Envisat has a suite of instruments that are focused on Earth's atmosphere, water and surface measuring the amounts of ozone and water vapor in the atmosphere, the surface temperatures of the seas and oceans and the amount of sunlight absorbed and reflected by our planet.
Envisat is making an fairly bright pass this evening and will be easy to locate using the Big Dipper. It will swell to magnitude 3.2 during its approximately three minutes of good visibility. This is just one level of brightness fainter than the Dipper stars and should be a fairly easy catch. You can use the map above to help guide you to this ever-watchful eye on the environment.
The new sunspot group 1057 is a big one and growing rapidly. This photo was taken this morning through a small telescope equipped with a solar filter. Details: f/14 at 1/6400", ISO 100. Photo: Bob King
When I looked at the sun this morning through my filtered telescope I was taken aback by the size of new sunspot group coming around the sun's east side. This is a whopper! It's named Sunspot region 1057 and its two main spots are each already bigger than the Earth. I'll keep you updated on any fireworks this group might provide over the coming two weeks as it's carried by the sun's rotation from eastern edge of the disk to the west.