Mapping the early universe - eagerly awaiting JWST

April 19, 2021

Scientists around the globe are eagerly awaiting the launch of the James Webb Space Telescope (JWST), the successor to the famous Hubble telescope, scheduled for October. Preparations of various observing programs for the use of the new flagship are also in full swing at the Max Planck Institute for Astronomy (MPIA). One example is the COSMOS-Webb program – the largest observing program in the first year of operation of JWST

The COSMOS-Webb survey will map 0.6 square degrees of the sky—about the area of three full moons—using JWST’s Near Infrared Camera NIRCam. Simultaneously, a smaller 0.2 square degrees area will be explored with the Mid Infrared Instrument MIRI.

COSMOS-Webb is designed to map the earliest structures of the universe.  In an elaborate survey, about 500,000 galaxies will be observed with high-resolution imaging in different spectral regions of the near-infrared and another 32,000 galaxies in the mid-infrared during more than 200 observing hours.

The program is led by scientists at the Rochester Institute of Technology and the University of Texas at Austin, which reported it in a press release today (press release)

MPIA, through Knud Jahnke and his group, is also a prominent member of the total 50-member international team from more than 30 institutes.  COSMOS-Webb is one of several important scientific programs related to JWST in which MPIA is involved and which will be reported on in the run-up to the launch –  as well as about MPIA's contributions to the construction of the space telescope's instrumentation.

"As a so-called "treasury" program, the data will be quickly made publicly available to other researchers through the consortium," says Knud Jahnke . "This will make COSMOS-Webb a virtually inexhaustible source for follow-up studies and follow-up observations for many, many years.

COSMOS-Webb is one of only 286 general programs for the first year of JWST research, selected from about 1000 proposals. It aims to survey a 0.6-square-degree field (3 times larger area than the full Moon) with the near-infrared NIRCam camera and a 0.2-square-degree field with the mid-infrared MIRI instrument. One goal is to study the first stars and the predecessors of galaxies that provided the reionization of the young cosmos due to their high-energy radiation.

But, surprisingly, there were also evolved galaxies already in this early period just a few 100 million years after the Big Bang, which will also be observed. Finally, the distribution of dark matter and its role in the formation of cosmological structures will be further explored using "weak lensing" – continuing the dark matter discoveries of the original Hubble-based COSMOS survey. By "weak lensing," astronomers mean the slightly distorted images of galaxies due to light which is "bent" by the invisible mass of dark matter in the line of sight. This allows the mapping of the distributions of this still-mysterious substance.

This artist’s illustration displays the scientific capabilities of  JWST. The large mirror, near- to mid-infrared sensitivity, and high-resolution imaging and spectroscopic capabilities will allow astronomers to search for the first galaxies, explore the formation of stars, and measure physical and chemical properties of planetary systems, including our own solar system.

If all goes well, JWST will launch into space from French Guiana on October 31, 2021, on an ESA Ariane 5 rocket. The telescope, with a primary mirror 6.5 meters in diameter (Hubble: 2.4 meters), is a joint project of the space agencies of the United States, Europe and Canada (NASA, ESA and CSA). JWST will be "stationed" about 1.5 million kilometers from Earth and will observe mainly in the infrared range between 0.6 and 28 µm wavelength for at least 5 years.

Almost all fields of astrophysics will benefit from the vastly increased sensitivity and resolution compared to Hubble. JWST will study the most distant galaxies and thus the early phases of the universe. Furthermore, it will  provide detailed views of young solar systems and exoplanets in our home galaxy, the Milky Way.

MPIA is involved both in building the instruments for JWST as well as  leading or participating in several important observing projects that will be reported on in advance of the launch in the fall.

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