Quasars, ESO VLT, UKIDSS, and more

4 07 2011
Paranal Platform, home of the ESO's VLT

Paranal Platform, home of the ESO's VLT. Photo credit: ESO/H. H. Heyer

The FORS2 instrument on ESO’s Very Large Telescope (VLT). Gemini North. UKIDSS. Astronomers in Germany. Astronomers in the United Kingdom. Astronomers in Hawaii. A quasar with a mass two million times that of our Sun. That’s the short version of the story. The slightly longer version runs something like this:

The European Southern Observatory is home to the VLT and its array of (mostly) optical instruments. Among those instruments is FORS2 (FOcal Reducer and Spectrograph), a visible-spectrum imager and low-resolution spectrograph.* For the past five years, German astronomers working through the ESO have been searching for a quasar with a redshift higher than 6.5. The higher the redshift, the more distant the object; the more distant the object, the closer the object to the originary moment of the universe. Until recently, the most distant quasars we’ve observed have had redshifts of approximately 6.4.** This means we’re seeing these objects as they were about 870 million years after the Big Bang. We know there are more distant objects out there, but they can’t be viewed with instruments tuned to the visible spectrum. They’re simply too far away; by the time the radiation from these objects reaches us, it’s been so stretched by the expansion of the universe, it can only be detected in the infrared.

Enter the United Kingdom Infrared Telescope (UKIRT) Infrared Deep Sky Survey (UKIDSS). As its name implies, UKIDSS is a consortium of astronomers working together to conduct infrared surveys of the sky using the Wide Field Infrared Camera (WFCAM) on the UKIRT on Mauna Kea. Imagine the celebration when the team discovered a quasar with a redshift of 7 (actually, 7.085±0.003). Now known as ULAS J1120+0641, this new quasar shows us the universe only 770 million years after the Big Bang—100 million years earlier than previously measured quasars. If those numbers aren’t big enough to give you pause, here’s another one to consider:  it took 12.9 billion years for the light from ULAS J1120+0641 to reach us. That definitely qualifies as far, far away.

But the story’s not quite over yet. Before announcing the quasar’s discovery in the journal Nature last week, the research team conducted some follow-up observations at the VLT and Gemini North to confirm the object’s distance from us. I could type for ten more minutes, but that still wouldn’t give me enough time to list all the groups and countries contributing to the VLT and Gemini Telescopes (and my typing speed is quick). I know I’m supposed to be in a state of sadness over the end of the U.S. space shuttle program, and I am, but I’m also heartened daily by the incredible successes of these multi-national, multi-agency, multi-interest projects.

The ESO has made the letter describing the discovery available in .pdf form in its public archives.

* The design of FORS2 and its now-retired twin, FORS1, happened by joint effort of ESO, Landessternwarte HeidelbergUniversity Observatory Göttingen and University Observatory Munich.

**The quasar CFHQS J0210045613 has a redshift of 6.44; SDSS 1148+52513, a redshift of 6.42; and CFHQS J2329+030114, a redshift of 6:42.



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