For three decades, astronomers have been waging war with the air around them, and slowly winning. A succession of increasingly advanced technologies--under the name active optics, and more recently adaptive optics--compensated for the continuous blowing, flowing, shimmering, and general blurring of Earth's atmosphere. These devices are not perfect, but they do a credible job sharpening the view. Essentially all of the world's major observatories now use some system along those lines.
Laser beams shoot up from the Gemini South telescope, creating artificial reference "stars" that make it possible to zero out the effects of atmospheric blurring. (Credit: Gemini Observatory/AURA) Now the engineers at the Gemini Observatory have taken blur-elimination technology a step beyond. They have just equipped the 8.1-meter Gemini South telescope, located atop Cerro Pachon in Chile, with a system called GeMS. The full name is a mouthful (Gemini Multi-Conjugate Adaptive Optics System) but its effect is straightforward: It compensates for atmospheric motions as they happen, allowing Gemini South to match the sharpness of the Hubble Space Telescope. In essence, astronomers flick a switch and the air disappears, making the view from a Chilean mountaintop almost exactly match the view from space. There are still many things Hubble can do that Earthbound telescopes cannot. Most notably, Hubble can look at wavelengths that do not effectively penetrate the atmosphere. On the other hand, ground-based observatories are much cheaper to build; despite its considerably lower cost, Gemini South is much bigger than Hubble, allowing it to gather more than 10 times as much light. Systems similar to GeMS will be built into the next generation of even larger ground-based telescopes, such as the upcoming Thirty Meter Telescope, Giant Magellan Telescope, and the Extremely Large Telescope. GeMS uses lasers to illuminate sodium atoms high in the atmosphere, creating a constellation of artificial stars. Those fake stars provide reference points for creating a detailed 3D model of air turbulence, which is updated up to 1,000 times per second. That information is then fed into three deformable mirrors, which bend and deform to precisely cancel out whatever the atmosphere is doing. The following images--part of an inaugural set released to celebrate the inauguration of GeMS--gives a sense of just how glorious the cosmos looks when you take the blur out. (All Gemini images courtesy Gemini/AURA.) The Orion Nebula is a huge star-forming cloud located 1,300 light years from Earth. It has been well studied for centuries, but the GeMS image shows revelatory details. The red arrowheads at upper right are created by "bullets" of supersonic gas that race through the hydrogen cloud, creating jagged wakes. The gas is probably propelled by the explosions of young, massive stars. The nature of the bullets themselves is unclear. John Bally of the University of Colorado at Boulder speculates they could be blobs of as-yet unformed stars, or perhaps infant planets that were cruelly cast out into the wilds of interstellar space. Future Gemini studies will help provide the answer.
A Hubble Space Telescope imageof the Orion Nebula shows more expanse but lacks the fine detail of the Gemini images.
Credit: HST/ESA The Antennae are two giant spiral galaxies seen in the middle of a slow-motion collision. The pair began to plow into each other about 250 million years ago--around the time the first dinosaurs appeared on Earth. Individual stars are so far apart that they are in no danger of destruction, but gas clouds in the two galaxies smash together and become violently compressed. Those clouds then collapse and break up, creating rich clusters of new stars. Gemini South staff astronomer Rodrigo Carrasco is using this image to learn more about how that cluster-formation process works. His results hit close to home: In about five billion years, our own Milky Way galaxy will experience a similar process when it collides with the Andromeda Galaxy.
A Hubble Space Telescope imageof the Antennae gives context to the Gemini image. The Gemini view provides a detailed closeup of the upper right member of the Antennae, uncovering details that are seriously overexposed in the Hubble version.
Credit: HST/ESA The Large Magellanic Cloud, one of the Milky Way's satellite galaxies, is home to a starforming region called R136. Because it is nearby, R136 is a great place to study details that are hard to see in more distant settings like the Antennae. Stars are crowded together tightly in these clusters, making them demanding tests of a telescope's vision. The National Optical Astronomy Observatory’s deputy director, Robert Blum, is sifting through the GeMS imagery to conduct a survey of the numbers and types of new stars being born in R136. That information will clarify the more general process of how gas clouds turn into stars, keeping the universe lit up. Just think: every dot here is a new sun, probably with new planets and a possible future abode for life.
The Hubble Space Telescope version of R136 again provides a broader view but lacks some of Gemini's crucial detail. The Gemini view zeroes in on the region at center right in the Hubble image.
Credit: HST/ESA Globular Cluster NGC 1851 is the opposite of R136: an ancient grouping of stars, about 10 billion years old, making in 1,000 times the age of R136. It is even closer, just 40,000 light years from Earth. Whereas studying R136 shows how stars are born, NGC 1851 reveals how they die. Massive stars burn out more quickly than lightweight ones. Touring a globular cluster is something like doing a medical survey in a nursing home; it shows what kind of lifestyles allow some individuals to reach old age while others perished much sooner. This beautiful beehive of stars is also a prime location for studying the gravitational dynamics of large groups of stars as they swarm around each other. If we lived in a globular cluster the night sky would blaze with thousands of bright stars, dozens of them so intense that they would be visible by day.
Planetary nebulae NGC 2346 shows where the life story of a typical star ends. After billions of years of stability, a middle-weight star expands into a red giant, then puffs off its outer layers. A delicate planetary nebula (not a planet at all, but an expanding cloud of gas) is the result. All that is left behind is a white dwarf, a dying stellar cinder. Our sun will experience this fate in about 7 billion years. Stunning images such as this one illustrate that death also contains the seeds of new life. The wispy tendrils seen in this exquisite GeMS image are carrying heavy elements into deep space, where they will eventually find their way into the next generation of stars and planets. Letizia Stanghellini of the National Optical Astronomy Observatory is studying NGC 2346 as a showcase of the galaxy's chemical recycling process. The eerie blood-red color here is somewhat misleading; this is an infrared image, color coded to bring out the detail. But the sense of foreboding is entirely appropriate.
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