Two Wide Eyes on the Sky

These days it's not unusual for professional observatories to become operational months, if not years, before their formal "first light" ceremony. That's the situation with two new and very different facilities situated half a world apart.

LOFAR station
Each LOFAR starion is a cluster of 96 omnidirectional antennas.
ASTRON
For several years a team at ASTRON, the Netherlands Institute for Radio Astronomy, has been building the Low Frequency Array (LOFAR), a widespread network of receivers to probe the radio sky at very long wavelengths. The first LOFAR station (with 96 antennas) came online in 2006, and since then the system has grown to include stations spread across 36 fields in the north of the Netherlands and also in Germany, Sweden, France and the United Kingdom — 25,000 antennas in all!

At a June 12th ceremony, the Netherlands' Queen Beatrix pushed a button to mark the official start of LOFAR's scientific observations. (I'm sure it was a nice ceremony, but LOFAR's first high-resolution image had already been released two weeks earlier).

LOFAR will map the radio sky at wavelengths of 1.3 to 30 meters — a spectral range that's been explored before but not very well, owing to the large collecting area needed to detect sources at all and to the expansive antenna spacing required to resolve individual details. LOFAR uses simple omnidirectional V-shaped dipoles (no moving parts!) and connects them all electronically to a supercomputer at the University of Groningen.

LOFAR view of quasar 3C 196
Left: A radio images of the quasar 3C 196 using just the LOFAR stations in the Netherlands. The resolution isn't good enough to identify any detail. Right: By adding data from the German LOFAR stations, the resolution improves about tenfold.
Olaf Wucknitz / Bonn Univ.
The result is a virtual telescope 60 to 600 miles (100 to 1,000 km) across, depending on the stations used. Some stations remain to be built in northern Germany, but LOFAR already ranks as the world's largest radio telescope.

Armed with this powerful new receiver, astronomers hope to explore highly redshifted radio emissions from what's called the epoch of reionization, when the first stars formed and lit up the very early universe. They'll also use LOFAR to carry out large-area surveys — the antennas' signals can be combined to look in multiple directions at once — and to track violent cosmic explosions and other transient phenomena that were observed poorly by previous long-wavelength radio surveys.

Meanwhile, astronomers who work in visible light are celebrating the scientific debut of what promises to be the most powerful survey telescope ever built. It's called Pan-STARRS, short for Panchromatic Survey Telescope And Rapid Response System. A June 16th press release announced that PS1, the first of four telescopes planned, is now fully operational. With an aperture of 6 feet (1.8 m), PS1 is perched at the summit of Haleakala on the Hawaiian island of Maui, 10,000 feet (3,050 m) above sea level.

Pan-STARRS in dawn's light
Dawn's light envelops the first Pan-STARRS telescope atop Haleakala on Maui. In the distance is Mauna Kea.
Rob Ratkowski / Pan-STARRS
As with LOFAR, there's a backstory to be told. For starters, astronomers started test observations with PS1 back in 2006. It's been making science-quality observations for the past six months, and dusk-to-dawn observing began in May. That said, the project has suffered technical setbacks that have put the project years behind schedule, and some glitches remain to be worked out before construction of the second telescope begins.

But Pan-STARRS is not just an observatory — it's intended to be an automated discovery pipeline. The telescope feeds a 3°-wide field to the largest digital camera ever built, an assembly of 60 large CCDs that together record 1.4 billion pixels per image. Exposures of 30 to 60 seconds is all that's needed to record the sky to 24th magnitude. Eventually all four telescopes will be imaging the same field simultaneously, to reduce noise and yield the light-gathering power of a single mirror nearly 12 feet (3.6 m) across.

The combination of wide field and short exposures means that Pan-STARRS can cover 6,000 square degrees — about a fifth of the entire sky visible fom Hawaii — each night!

So what will astronomers do with that kind of telescopic horsepower? Lots. A dozen key projects are planned, to tackle everything from determining distances to nearby galaxies (by monitoring the pulsations of Cepheid variable stars) to tallying the occurrence of novas and supernovas. In fact, PS1 has already found about a dozen supernovas.

Closer to home, planetary scientists expect to discover 20,000 objects in the Kuiper Belt (likely some bigger than Pluto or Eris) and more than 100,000 Trojan asteroids sharing the giant planets' orbits.

But Pan-STARRS's most immediate and important goal will be to defend our planet against near-Earth objects (NEOs), by finding thousands of asteroids and comets in the 100-m range. Although relatively small, these could do significant damage should they collide with us. Because Pan-STARRS's images go so deep, astronomers elsewhere will be scrambling to follow up all the NEO candidates it discovers.

Interestingly, both LOFAR and Pan-STARRS cost about $100 million — the former by various Dutch agencies and project partners, the latter by the U.S. Defense Department.

2 thoughts on “Two Wide Eyes on the Sky

  1. Kenneth Barshney

    I love this!!!!!!! Although I still refuse to do nuptials with the telescopes!!!!!

    What a great combination of these earth based telescopes’ . We will have the ability too scan the heavens with this great array !!!! WOW!!!!, I am awe struck at how far astronomy has come since I was a 9 year old boy back in the early “60”‘s !!!!! We all have the chance to live in the moment of this remarkable assembly of telescopes!!!!! I say “Let’s Go” !!!!!

  2. Conrad

    Nice article. However, I did see one small mistake. You made a mistake in translating the acronym for Pan-STARRS.

    Just to be clear, Pan-STARRS stands for Panoramic Survey Telescope And Rapid Response System.

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