The Planet, the Galaxy and the Laser

On the night of 21 July, ESO astronomer Yuri Beletsky took images of the night sky above Paranal, the 2600m high mountain in the Chilean Atacama Desert home to ESO's Very Large Telescope. The amazing images bear witness to the unique quality of the sky, revealing not only the Milky Way in all its splendour but also the planet Jupiter and the laser beam used at Yepun, one of the 8.2-m telescopes that make up this extraordinary facility.

"The images are not composite", emphasises Yuri Beletsky. "The camera was being tracked on the stars, which can be easily noticed if you look at the telescope domes on the image (they look a little fuzzy). The colour of the laser beam on the first image actually looks pretty close to what one can see on the sky with the unaided eye."

Most striking in the images is the wide band of stars called the Milky Way. Spanning more than 100 degrees in the first of these images, it shows the dust and stars that are part of our own Galaxy, a spiral galaxy containing about 100 billion stars.

In the middle of this image, two bright objects are also seen. The brighter of the two is the planet Jupiter. The other is the bright star Antares. Another bright star, Alpha Centauri, one of the closest stellar neighbours to the Sun, is visible at the middle-left edge of the image.

Three of the four domes that shelter the 8.2-m VLT's Unit Telescopes are visible on the first image. Streaming out of Yepun, Unit Telescope number 4, is the laser beam used to create an artificial star above Paranal, aiming directly at the centre of our own Galaxy.

At the time the pictures were taken, astronomers were indeed using the SINFONI instrument to study the Galactic Centre, having a close look at the supermassive black hole that lurks in there.

With so many stars visible from the exceptional site of Paranal, one may wonder why it is necessary to create another, artificial, star" The answer lies in the very sophisticated instruments that are used on ESO's VLT. Some of them, such as NACO and SINFONI, make use of adaptive optics, a technique that allows astronomers to overcome the blurring effect of the atmosphere. This means that astronomers obtain images almost as good as if the whole telescope was placed in space, above Earth's atmosphere.

Adaptive optics, however, requires a nearby reference star that has to be relatively bright, thereby limiting the area of the sky that can be surveyed. To surmount this limitation, astronomers now use at Paranal a powerful laser that creates an artificial star, where and when they need it.

Launching such a powerful laser from a telescope is state-of-the-art technology, whose set-up and operation is a continuous challenge. As seen from the images, this is, however, a technology that is now well mastered on Paranal.

The images were obtained with a digital camera and 10-mm optics, mounted on a small equatorial mount, and are each the result of a single 5 minute exposure.

Source: European Southern Observatory

Related stories:

All-in-one printer evolves: Does more, does better
Used to be that I'd avoid all-in-one consumer electronic products simply because they just weren't as good as the separate, standalone models. But that's changed, especially when it comes to computer peripherals. Take the printer for example. Or more specifically, let's take a look at Epson's latest offering in their all-in-one printers category, the Artisan 800.
Astronomers weigh the coldest brown dwarfs with astronomy's sharpest eyes
Astronomers have used ultrasharp images obtained with the Keck Telescope and Hubble Space Telescope to determine for the first time the masses of the coldest class of "failed stars," a.k.a. brown dwarfs. With masses as light as 3 percent the mass of the sun, these are the lowest mass free-floating objects ever weighed outside the solar system. The observations are a major step in testing the theoretical predictions of objects that cannot generate their own internal energy, both brown dwarfs and gas-giant planets. The new findings, which are being presented in a press conference today at the American Astronomical Society meeting in St. Louis, show that the predictions may have some problems.
Scientists 'weigh' tiny galaxy halfway across universe
A tiny galaxy, nearly halfway across the universe, the smallest in size and mass known to exist at that distance, has been identified by an international team of scientists led by two from the University of California, Santa Barbara.
Free from the Atmosphere
An artificial, laser-fed star now shines regularly over the sky of Paranal, home of ESO's Very Large Telescope, one of the world's most advanced large ground-based telescopes. This system provides assistance for the adaptive optics instruments on the VLT and so allows astronomers to obtain images free from the blurring effect of the atmosphere, regardless of the brightness and the location on the sky of the observed target. Now that it is routinely offered by the observatory, the skies seem much sharper to astronomers.
Adaptive optics pinpoints 2 supermassive black holes in colliding galaxies
Astronomers have discovered the exact location and makeup of a pair of supermassive black holes at the center of a collision of two galaxies more than 300 million light years away.
Unique observations of Comet McNaught reveal sprinkling nucleus
Comet McNaught, the Great Comet of 2007, has been delighting those who have seen it with the unaided eye as a spectacular display in the evening sky. Pushing ESO's New Technology Telescope to its limits, a team of European astronomers have obtained the first, and possibly unique, detailed observations of this object. Their images show spectacular jets of gas from the comet spiralling several thousands of kilometres into space, while the spectra reveal the presence of sodium in its atmosphere, something seen very rarely.
NASA's Mars Global Surveyor May Be at Mission's End
NASA's Mars Global Surveyor has likely finished its operating career. The orbiter has not communicated with Earth since Nov. 2. Preliminary indications are that a solar panel became difficult to pivot, raising the possibility that the spacecraft may no longer be able to generate enough power to communicate.
Wide Awake on the Sea of Tranquillity
Neil Armstrong was supposed to be asleep. The moonwalking was done. The moon rocks were stowed away. His ship was ready for departure. In just a few hours, the Eagle's ascent module would blast off the Moon, something no ship had ever done before, and Neil needed his wits about him. He curled up on the Eagle's engine cover and closed his eyes. But he could not sleep.

News discussion:

Space & Earth science news