Astronomers turn "Sky movie"

Observatory Pan-STARRS begins systematic survey of the night sky

The Pan-STARRS1 observatory just before sunrise on Haleakala, Maui. © Rob Ratkowski
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The new Observatory Pan-STARRS (Panoramic Survey Telescope and Rapid Response System) in Hawaii has now begun with unique observations of much of the night sky. It is the first systematic and on a large scale looking for changing phenomena.

Using the observational data, the astronomers involved, for example, want to track down asteroids that could threaten Earth and learn more about some of the greatest cosmic mysteries, such as dark matter and dark energy. It's also about finding planets around distant stars, brown dwarfs, and distant active galaxies.

Prototype begins scientific observing operation

The telescope, which has now begun scientific observation, PanSTARRS1 (PS1), is a prototype for later extensive surveys with a total of four telescopes of the same type. "PS1 has been collecting data of scientific quality for six months, " says Nick Kaiser, scientist at the Max Planck Institute for Astronomy, responsible for the Pan-STARRS project. "From now on we can start the regular operation, where the observatory collects data from dusk to dawn." The telescope has now moved from test operation to scientific observation mode.

Unique "sky film"

The eternally same constellations of the starry sky are almost a symbol of the immutable. But on closer inspection, there is a lot going on in the night sky - from objects like changing stars to rare events that are only visible for a short time. Now a survey has begun that is dedicated to such changeable phenomena. Pan-STARRS1 is to produce 30 delayed recordings of around 75 percent of the night sky - time series of several hundred pictures are being created of particularly interesting areas. This creates a unique "heavenly film".

"Every month, Pan-STARRS1 observes one-sixth of the sky in five different wavelength ranges, " explains Roberto Saglia of the Max Planck Institute for Extraterrestrial Physics. "On the one hand, this enables us to detect brightness variations in the sky very well, but on the other hand we can take very deep shots of large sky regions." Certain regions of the sky are even observed every night. Among other things, the observations will produce a uniquely detailed three-dimensional map of our home galaxy, the Milky Way. In our neighbor galaxy Andromeda Pan-STARRS1 is supposed to create a complete inventory of mutable objects. display

Search for asteroids

On the one hand, Pan-STARRS1 is a classic survey that searches for known classes of celestial objects - from the extremely faint and reddish brown dwarfs of our Milky Way galaxy to the earliest active galaxies in more as 13 billion light years away. Another part of the search is of fundamental practical interest: Pan-STARRS1 is designed to detect asteroids large enough to cause a global cataclysm in a collision with Earth.

Since Pan-STARRS1 repeatedly focuses its attention on the same celestial regions, it can detect changes. For example, it is possible to locate exoplanet transits - planets orbiting a distant star so that they regularly move between their parent star and the observer when viewed from Earth. In doing so, a tiny fraction of the starlight is intercepted and the apparent brightness of the star decreases a tiny bit. The same observation strategy increases the chances of being able to document very rare and short-lived celestial phenomena. For example, it would be possible for the first time to show how a black hole in the center of a distant galaxy swallows a star - an event that leads to a brightness increase lasting only a few days.

Astronomers hope for surprises

The astronomers are also prepared for surprises: "Whenever astronomers observe the sky in a different way than before, they make unexpected new discoveries, " says Professor Hans-Walter Rix of the Max Planck Institute f r Astronomy: Pan-STARRS1 is looking systematically and extensively for the first time for how the night sky changes over time and with this new kind of observation, surprising new insights are virtually preprogrammed.

With a telescope mirror just 1.8 meters in diameter, PS1 is a rather small telescope for the proportions of modern professional astronomy. However, PS1 has an exceptionally wide field of view: About 30 times the size of the full moon (seven square degrees) is the sky segment that PS1 can capture with one shot. The telescope-mounted 1.4-gigapixel camera is the largest digital camera in the world and makes PS1 the currently most powerful telescope for sky surveys.

Lots of data

Now that the PSI Observatory has begun recording data, the observatory will produce several petabytes of data over the next few years, and could fill some 1, 000 DVDs each night. To cope with this flood of data, the Pan-STARRS cluster was set up at the Garching data center. With 150 TB of disk space for data reduction and initial analysis steps, further storage space on magnetic tape and 700 CPUs already in its works recorded on the first survey data.

In addition, special software has been developed that uses the color information to first classify the objects identified on the images and automatically determine certain key data such as the temperature and extinction of stars or the distance (redshift) of distant objects.

(idw - Max Planck Institute for Astronomy, 16.06.2010 - DLO)