The Planet, the Galaxy and the Laser

August 3, 2007
The Planet, the Galaxy and the Laser
Image of the night sky above Paranal on July 21, taken by ESO astronomer Yuri Beletsky. A wide band of stars and dust clouds, spanning more than 100 degrees on the sky, is seen. This is the Milky Way, the galaxy we belong to. At the center of the image, two bright objects are visible. The brightest is the planet Jupiter, while the other is the star Antares. Three of the four 8.2-meter telescopes forming ESO's VLT are seen, with a laser beaming out from Yepun, Unit Telescope number 4. The laser points directly at the Galactic Center. Also visible are three of the 1.8-meter Auxiliary Telescopes used for interferometry. They show small light beams which are diodes located on the domes. The exposure time is 5 minutes and because the tracking was made on the stars, the telescopes are slightly blurred. (c) Y. Beletsky/ESO

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

Explore further: 'Chemical laptop' could search for signs of life outside earth

Related Stories

'Chemical laptop' could search for signs of life outside earth

November 17, 2015

If you were looking for the signatures of life on another world, you would want to take something small and portable with you. That's the philosophy behind the "Chemical Laptop" being developed at NASA's Jet Propulsion Laboratory ...

Facebook gives sneak peek into sci-fi future

November 17, 2015

Mike Schroepfer is sitting in a conference room inside Facebook's Frank Gehry-designed headquarters. His ultra-modern surroundings—22-foot ceilings, raw steel beams, polished concrete pathways that flow through acres of ...

Robotic laser astronomy on the rise

October 13, 2015

The world's first robotic laser adaptive optics system, developed by a team led by University of Hawaiʻi at Mānoa astronomer Christoph Baranec, will soon find a new home at the venerable 2.1-meter (83-inch) telescope at ...

SETI reborn—the new search for intelligent life

September 10, 2015

A new influx of money has saved the Search for Extraterrestrial Intelligence (SETI) from collapse, but what does the future hold for our quest to discover intelligent life in the Universe?

Five myths about gravitational waves

September 7, 2015

The scientists behind the BICEP2 (Background Imaging of Cosmic Extragalactic Polarization) telescope, last year made an extraordinary claim that they had detected gravitational waves, which are ripples in space-time. Initially ...

Recommended for you

Earth might have hairy dark matter

November 23, 2015

The solar system might be a lot hairier than we thought. A new study publishing this week in the Astrophysical Journal by Gary Prézeau of NASA's Jet Propulsion Laboratory, Pasadena, California, proposes the existence of ...

Scientists detect stellar streams around Magellanic Clouds

November 23, 2015

(—Astronomers from the University of Cambridge, U.K., have detected a number of narrow streams and diffuse debris clouds around two nearby irregular dwarf galaxies called the Magellanic Clouds. The research also ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.