Hello Planetary Pals,
The James Webb Space Telescope has been in the works for many decades and now it may be finally ready to launch. Like most planetary scientists and astronomers, I have been anxiously and excitedly waiting for it’s launch for so long. Years of hard work, dedication and delays have built up tension around it’s launch, and within the few weeks, the scientific community will see if it will pay off. Just as I did for the Perseverance rover landing earlier this year, I wanted to make a blog post to familiarize myself with the goals of the JWST so that I can be prepared and knowledgeable during it’s launch and mission.
The planned launch date has changed so much that it has no longer come as a shock or disappointment anymore. In fact, just today it was pushed back at least another 2 days, with launch now scheduled for December 24th. In August 2019 the telescope was fully assembled for the first time and underwent rigorous testing. It arrived in French Guiana in mid-October 2021 after being shipped aboard a cargo ship. Over this past weekend, the telescope was folded and placed atop its Ariane 5 rocket.
With some luck, the rocket will successfully send the telescope to it’s target destination, one of Lagrange Points around the Earth-Sun system. It will take 30 days to reach this orbit. While travelling, it will unfold and fully deploy.
Once it arrives at it’s destination, it will need roughly 6 months to undergo initial preparations. The telescope operates best at very low temperatures, and will need to take time to fully cool down to 50 K. The mirrors and instruments will need to calibrate as well. To verify its calibrations, the telescope will image one star. This star will initially have different configurations as it is picked up by each hexagonal mirror. These 18 images can then be adjusted and aligned with precise micro-motors so that eventually all images and mirrors produce a calibrated, correct image. It will also test it’s ability to track moving objects such as comets and planets. By month 6, science operations will begin. It is slated to operate for 10 years.
JWST is mainly interested in infrared-red imaging. This range is best observed by a space-based telescope. There are four main instruments onboard including NIR and MIR cameras and imaging spectrometers.
Extremely red-shifted stellar objects (such as extremely far away objects) moving away from the telescope focal point can be observed with JWST, importantly redshifted objects that shift from the visible range into the IR range. Being able to detect these redshifted objects allows astronomers to see some of the oldest galaxies and stars. By observing these extremely old galaxies, it allows for understanding of the “Era of Recombination” in which the first elements were being produced through fusion. This process also captured free electrons into atoms, meaning that the universe was essentially opaque. The process of re-ionization can be also better understood with JWST by studying and observing these early stars. Reionization is the process in which a star’s UV radiation can detach a hydrogen atom’s electron, which allowed for the creation of the first sources of light in the universe, making the universe transparent.
By observing the earliest galaxies using JWST, astronomers can better understand the history of galaxy formation nd evolution. The oldest galaxies visible to Hubble show that they take on a completely different morphology to younger galaxies. These early galaxies are described as being “clumps” and “knots” of star formation, rather than the ordered and patterned modern spiral galaxies and elliptical galaxies. By having a more complete survey of galaxies, astronomers can better understand how galaxies form, evolve, interact, and synthesize elements.
The IR capability of JWST will be able to see through dust clouds that obscure areas in the visible range. This will allow for an understanding of how dust and gas clouds collapse into stars, groups of stars, and protoplanetary objects.
The JWST can target objects in our solar system as well. It will be used to spectrally characterize comets and planetary atmospheres. It will be able to take spectra of protoplanetary disks to understand extrasolar planet formation. As well, it can attempt to gather information about exoplanet compositions, atmospheres, evolution and habitability.
I am anxiously awaiting the launch of the telescope this month (hopefully). The entire astronomy ad planetary science community has invested so much and placed a ton of hope in the mission, and I will be sure to watch live to see the telescope depart on it’s mission.