DAWN participates in more than a third of the new James Webb Space Telescope’s initial observations

When the James Webb Space Telescope, despite repeated delays, finally launches in October, and after some initial calibrations begins its first cycle of observations, these will include an impressive Danish participation. The primary focus will be on learning more about the Universe’s earliest galaxies.

NASA's James Webb Space Telescope Early Science Observations Revealed
Artist's impression of the scientific capabilities of the James Webb Space Telescope. The large mirror, the infrared sensitivity, and the high resolution in imaging and spectroscopy enable astronomers to find the first galaxies, explore the formation of stars, and measure the physical and chemical properties of planetary systems, including our own Solar system.
Credits: NASA, ESA, and A. Feild (STScI)

Hubble’s successor

With a diameter almost three times that of the Hubble Space Telescope, the James Webb Space Telescope will be the largest ever launched into space. Indeed, it has been hailed as "Hubble’s successor". James Webb is built primarily to observe infrared light and will therefore revolutionise our knowledge of the very early Universe in particular.

"Early Universe" means redder light

The longer light has traveled through the Universe, the longer its wavelength becomes, and thus also the more (infra)red it becomes.
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"Early Universe" also means far away

The farther away a galaxy is, the longer time its light has had to travel to reach us. Hence, to find the earliest galaxies, we must try to detect the most distant ones.

At the Niels Bohr Institute and DTU Space's basic research centre "Cosmic Dawn Center" (or DAWN), which conducts research into galaxies, they are particularly excited about the launch of James Webb: the Danish researchers will participate in 2133 hours of the first cycle’s 6000 assigned hours of observation time, or over ⅓ of the total time available.

The DAWN centre has a special stake in James Webb, having contributed to the construction of two of the telescope’s instruments. As a reward, they have been assigned a number of ”extra” observation hours. However, the other over 2000 hours have been achieved in equal competition with researchers from 40 other countries.

Comparison between the mirrors of Hubble and James Webb.
Credit: NASA/JWST.

The earliest galaxies

The overall goal of DAWN’s programme is to study the earliest, and therefore most distant, galaxies in the Universe.

The most ambitious observational program has been dubbed "COSMOS-Webb". This programme intends to survey a large part of the already well-visited region of the sky that Hubble has long held in its spotlight. And the expected results will be magnificent: half a million galaxies, many from the period when the Universe was at a mere 5% of its current age.

The telescope’s giant mirror allows it to gather large amounts of light; crucial for observing the extremely faint objects in question. But just as a camera deploys a longer shutter speed to capture pictures at twilight, James Webb will also take very long exposures: an impressive 208 hours will be spent creating the deepest panoramic image to date of an unsurpassed population of the earliest galaxies.

“It’s unique that such a large and ambitious program is being implemented from the very beginning of James Webb’s guaranteed life span, which is just 5 years. This gives us, and all other users of the space telescope, the chance to identify thousands of galaxies of all types and at all evolutionary stages in the earliest Universe, including the rarest ones, which can be studied in detail through James Webb in the coming years," explains Georgios Magdis, associate professor in astronomy at the Cosmic Dawn Center.

Sune Toft, professor and DAWN's Center Director, who like Georgios Magdis is participating in the COSMOS-Webb collaboration, elaborates: "In addition to the galaxies we expect to find, we’re convinced that the most exciting discoveries that a large survey like this will uncover, are ones we aren’t even yet able to imagine. That’s what the history of astronomy has constantly demonstrated".

…and the largest

While COSMOS-Webb is the largest programme, DAWN is also involved in several other programmes, some led by early career researchers at the center. Instead of looking "broadly" at thousands of galaxies, one of these programmes has chosen to focus on five already well-known galaxies; not just random ones, but five galaxies so large and evolved that they challenge our understanding of galaxy formation.

We will peer back in time to capture the light of these mysterious galaxies, tracing out their stars, gas, and dust inside and out", explains John Weaver, PhD student at DAWN and leader of this project.

James Webb sees double

For yet another one of the selected programmes, James Webb is simply not enough. DAWN's postdoc Seiji Fujimoto, who is leading this third programme, will employ a marvellous technique, where gravity itself can deflect and enlarge the image of a galaxy, 28 billion light-years away.

Not only is the light amplified some 100 times; the magnification also allows him to study the galaxy’s inner structure to an unprecedented degree. Moreover, because light can take different paths through space, the galaxy can be observed in several multiple places in the sky at the same time.

These observations are not only interesting in themselves, but also increase expectations for future research.  "When next-generation telescopes in the 30-metre class are ready, we will be able to study star clusters, and perhaps even individual stars, in the most distant galaxies", affirms Seiji Fujimoto.

In addition to the programs described above, DAWN's affiliated scientists Pascal Oesch and Desika Narayanan lead three and one program, respectively. Moreover, our researchers are involved in several other programs. The complete list can be found below.

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