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Starts With A Bang

What James Webb’s Most Ambitious First-Year Science Mission Will Teach Us

Hubble, our greatest space-based observatory today, is just the beginning.

The Hubble Space Telescope has been astronomy’s most revolutionary observatory in history.

The stars and galaxies we see today didn’t always exist, and the farther back we go, the closer to an apparent singularity the Universe gets, as we go to hotter, denser, and more uniform states. While Hubble has provided humanity with our deepest views of the cosmos to date, even it is limited in how far back it can ‘see’ the distant Universe. (NASA, ESA, AND A. FEILD (STSCI))

For over 30 years, it’s taken us to the farthest depths of space.

Only because this distant galaxy, GN-z11, is located in a region where the intergalactic medium is mostly reionized, can Hubble reveal it to us at the present time. To see further, we require a better observatory, optimized for these kinds of detection, than Hubble: exactly what James Webb will deliver. (NASA, ESA, AND A. FEILD (STSCI))

Hubble’s deep-field views have revealed galaxies to unprecedented distances and faintnesses.

The Hubble eXtreme Deep Field (XDF) may have observed a region of sky just 1/32,000,000th of the total, but was able to uncover a whopping 5,500 galaxies within it: an estimated 10% of the total number of galaxies actually contained in this pencil-beam-style slice. The remaining 90% of galaxies are either too faint or too red or too obscured for Hubble to reveal. (HUDF09 AND HXDF12 TEAMS / E. SIEGEL (PROCESSING))

Despite these successes, its narrow field-of-view restricts its views to under 1% of the cumulative sky.

A close-up of over 550,000 science related observations made by the Hubble Space Telescope. The locations and sizes of the observations made can all be seen here. Although they are located in many different places, the total sky coverage is minimal. Many of the observations are clustered in the galactic plane or around surveys such as COSMOS, GOODS, or Frontier Fields. (NADIEH BREMER / VISUAL CINNAMON)

With larger-aperture, infrared capabilities, NASA’s James Webb Space Telescope will surpass Hubble in many ways.

The James Webb Space Telescope vs. Hubble in size (main) and vs. an array of other telescopes (inset) in terms of wavelength and sensitivity. Its power is truly unprecedented, and will reveal the Universe in ways that, even with all our other observatories combined, have never been possible before. (NASA / JWST TEAM)

Nominally scheduled for launch October 31st, many excellent alternative windows arise before 2021’s end.

One of the last tests that will be performed on NASA’s James Webb is a final check of the mirror deployment sequence in full. With all environmental stress testing now out of the way, these last checks will hopefully be routine, paving the way for a successful 2021 launch. (NASA / JAMES WEBB SPACE TELESCOPE TEAM)

Assuming Webb’s launch and deployment are successful, science operations will begin in 2022.

The planned post-launch deployment timeline of James Webb means that it can begin instrument cooling and calibrations just days after launch, and will be science-ready after only a few months. a successful launch in late 2021 means science observations will likely begin in the Spring of 2022. (NASA / JWST TEAM)

Although Webb deep fields are planned, there’s an even more ambitious project on the way: COSMOS-Webb.

This sea of galaxies is the complete, original COSMOS field from the Hubble Space Telescope’s Advanced Camera for Surveys (ACS). The full mosaic is a composite of 575 separate ACS images, where each ACS image is about one-tenth the diameter of the full Moon. The jagged edges of the outline are due to the separate images that make up the survey field. (ANTON KOEKEMOER (STSCI) AND NICK SCOVILLE (CALTECH))

Many Hubble surveys — like GOODS, COSMOS, and Frontier Fields — have focused on wide-field observations.

The GOODS-North field contains a massive galaxy cluster within it, as evidenced by the reddish galaxies, which stretch and magnify the light from the more-distant galaxies seen faintly in the background. This phenomenon of gravitational lensing serves as the Universe’s most powerful natural telescope. (NASA, ESA, P. OESCH (UNIVERSITY OF GENEVA), AND M. MONTES (UNIVERSITY OF NEW SOUTH WALES))

By observing nearby patches of sky repeatedly, we can stitch together broader views of the Universe.

This image from the NASA/ESA Hubble Space Telescope shows the galaxy cluster MACSJ0717.5+3745. This is one of six being studied by the Hubble Frontier Fields programme, which together have produced the deepest images of gravitational lensing ever made. Due to the huge mass of the cluster it is bending the light of background objects, acting as a magnifying lens. It is one of the most massive galaxy clusters known, and it is also the largest known gravitational lens. Of all of the galaxy clusters known and measured, MACS J0717 lenses the largest area of the sky. (NASA, ESA AND THE HST FRONTIER FIELDS TEAM (STSCI))

Multi-wavelength additions have already revealed copious cosmic features, including:

These two galaxy clusters are part of the “Frontier Fields” project, which uses some of the world’s most powerful telescopes to study these giant structures with long observations. Galaxy clusters are enormous collections of hundreds or thousands of galaxies and vast reservoirs of hot gas embedded in massive clouds of dark matter. These images contain X-ray data from Chandra (blue), optical light from Hubble (red, green, and blue), and radio data from the Very Large Array (pink). (X-RAY: NASA/CXC/SAO/G.OGREAN ET AL.)
  • galaxy growth,
Galaxies identified in the eXtreme Deep Field image can be broken up into nearby, distant, and ultra-distant components, with Hubble only revealing the galaxies it’s capable of seeing in its wavelength ranges and at its optical limits. The dropoff in the number of galaxies seen at very great distances may indicate the limitations of our observatories, rather than the non-existence of faint, small, low-brightness galaxies at great distances. (NASA, ESA, AND Z. LEVAY, F. SUMMERS (STSCI))
  • large-scale clustering,
Two massive galaxy clusters — Abell S1063 (left) and MACS J0416.1–2403 (right) — display a soft blue haze, called intracluster light, embedded among innumerable galaxies. The intracluster light is produced by orphan stars that no longer belong to any single galaxy, having been thrown loose during a violent galaxy interaction, and now drift freely throughout the cluster of galaxies. This intracluster light closely matches with a map of mass distribution in the cluster’s overall gravitational field. This makes the blue ‘ghost light’ a good indicator of how invisible dark matter is distributed in the cluster. (NASA, ESA, AND M. MONTES (UNIVERSITY OF NEW SOUTH WALES))
  • gravitational lensing,
Clumps and clusters of galaxies exhibit gravitational effects on the light-and-matter behind them due to the effects of weak gravitational lensing. This enables us to reconstruct their mass distributions, which should line up with the observed matter. (ESA, NASA, K. SHARON (TEL AVIV UNIVERSITY) AND E. OFEK (CALTECH))
  • and evolving star-formation rates.
The Fermi-LAT collaboration’s reconstructed star-formation history of the Universe, compared with other data points from alternative methods elsewhere in the literature. We are arriving at a consistent set of results across many different methods of measurement, and the Fermi contribution represents the most accurate, comprehensive result of this history thus far. (MARCO AJELLO AND THE FERMI-LAT COLLABORATION)

With Webb’s infrared views added in, we’ll probe reionization and dark matter growth as well.

More than 13 billion years ago, during the Era of Reionization, the universe was a very different place. The gas between galaxies was largely opaque to energetic light, making it difficult to observe young galaxies. The James Webb Space Telescope will peer deep into space to gather more information about objects that existed during the Era of Reionization to help us understand this major transition in the history of the universe. (NASA, ESA, JOYCE KANG (STSCI))

How did galaxies grow, evolve, and turn on so early in time?

A portion of the Hubble Ultra-Deep Field, featuring a region of sky that’s been imaged for a total of 23 days as part of the eXtreme Deep Field program. Although this data is magnificent, we know there are galaxies and details we’re missing, and that NASA’s upcoming James Webb Space Telescope will reveal details never seen before in the Universe. (NASA/ESA AND HUBBLE AND THE HUDF TEAM)

With ~500,000 galaxies from COSMOS-Webb, we’ll finally find out.

This simulated image represents what the James Webb Space Telescope ought to see, as compared with the previous (earlier, actual) Hubble image. With the COSMOS-Webb field expected to come in at 0.6 square degrees, it should reveal approximately 500,000 galaxies in the near-infrared, uncovering details that no observatory to date has been able to see. (JADES COLLABORATION FOR THE NIRCAM SIMULATION)

Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. Talk less; smile more.

Starts With A Bang is written by Ethan Siegel, Ph.D., author of Beyond The Galaxy, and Treknology: The Science of Star Trek from Tricorders to Warp Drive.


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