Epoch of Reionization Archives

October 13, 2024October 13, 2024 by Matt Williams

Webb Observations Shed New Light on Cosmic Reionization

A simulation of galaxies during the era of deionization in the early Universe. Credit: M. Alvarez, R. Kaehler, and T. AbelCredit: M. Alvarez, R. Kaehler, and T. Abel

The “Epoch of Reionization” was a critical period for cosmic evolution and has always fascinated and mystified astronomers. During this epoch, the first stars and galaxies formed and reionized the clouds of neutral hydrogen that permeated the Universe. This ended the Cosmic Dark Ages and led to the Universe becoming “transparent,” what astronomers refer to as “Cosmic Dawn.” According to our current cosmological models, reionization lasted from 380,000 to 1 billion years after the Big Bang. This is based on indirect evidence since astronomers have been unable to view the Epoch of Reionization directly.

Investigating this period was one of the main reasons for developing the James Webb Space Telescope (JWST), which can pierce the veil of the “dark ages” using its powerful infrared optics. However, observations provided by Webb revealed that far more galaxies existed in the early Universe than previously expected. According to a recent study, this suggests that reionization may have happened more rapidly and ended at least 350 million years earlier than our models predict. Once again, the ability to peer into the early Universe has produced tensions with prevailing cosmological theories.

September 18, 2024September 18, 2024 by Evan Gough

The Early Universe Had a Lot of Black Holes

The Hubble Ultra Deep Field seen in ultraviolet, visible, and infrared light. Image Credit: NASA, ESA, H. Teplitz and M. Rafelski (IPAC/Caltech), A. Koekemoer (STScI), R. Windhorst (Arizona State University), and Z. Levay (STScI)

The Hubble Deep Field and its successor, the Hubble Ultra-Deep Field, showed us how vast our Universe is and how it teems with galaxies of all shapes and sizes. They focused on tiny patches of the sky that appeared to be empty and revealed the presence of countless galaxies. Now, astronomers are using the Hubble Ultra-Deep Field and follow-up images to reveal the presence of a large number of supermassive black holes in the early Universe.

This is a shocking result because, according to theory, these massive objects shouldn’t have been so plentiful billions of years ago.

June 27, 2024June 27, 2024 by Evan Gough

Webb Sees Globular Clusters Forming in the Early Universe

The Cosmic Gems arc as observed by the JWST. The clusters have the attributes of gravitationally-bound proto-Globular Clusters. Credit: ESA/Webb, NASA & CSA, L. Bradley (STScI), A. Adamo (Stockholm University) and the Cosmic Spring collaboration.

Picture the Universe’s ancient beginnings. In the vast darkness, light was emitted from a particular galaxy only 460 million years after the Big Bang. On the way, the light was shifted into the infrared and magnified by a massive gravitational lens before finally reaching the James Webb Space Telescope.

The galaxy is called the Cosmic Gems arc, and it held some surprises for astronomers.

June 19, 2024June 19, 2024 by Andy Tomaswick

The Earliest Merging Quasars Ever Seen

This illustration depicts two quasars in the process of merging. There are many unanswered questions around galaxy mergers and the quasars that can result. Image Credit: NOIRLab/NSF/AURA/M. Garlick)

Studying the history of science shows how often serendipity plays a role in some of the most important discoveries. Sometimes, the stories are apocryphal, like Newton getting hit on the head with an apple. But sometimes, there’s an element of truth to them. That was the case for a new discovery of the oldest pair of merging quasars ever discovered – and it all started with a pair of red blots on a picture.

June 5, 2024June 5, 2024 by Evan Gough

The JWST is Re-Writing Astronomy Textbooks

The first JWST Deep Field Image, showing large distant galaxies. The telescope's observations are revealing the previously unseen and are forcing a re-write of astronomy textbooks. Image Credit: NASA, ESA, CSA, STScI

When the James Webb Space Telescope was launched at the end of 2021, we expected stunning images and illuminating scientific results. So far, the powerful space telescope has lived up to our expectations. The JWST has shown us things about the early Universe we never anticipated.

Some of those results are forcing a rewrite of astronomy textbooks.

February 28, 2024February 28, 2024 by Evan Gough

Dwarf Galaxies Banished the Darkness and Lit Up the Early Universe

The JWST used gravitational lensing to search for the sources of light that triggered the Epoch of Reionization and brought darkness to an end. The white hazy blobs are galaxies in Pandora's Cluster, which acts as the gravitational lens. The red objects are the distant and ancient objects magnified by the lens, some of them warped into arcs. Many of them are early dwarf galaxies, some of them responsible for the Epoch of Reionization. Image Credit: NASA/ESA/CSA JWST

During the Universe’s Dark Ages, dense primordial gas absorbed and scattered light, prohibiting it from travelling. Only when the first stars and galaxies began to shine in energetic UV light did the Epoch of Reionization begin. The powerful UV light shone through the Universe and punched holes in the gas, allowing light to travel freely.

New observations with the James Webb Space Telescope reveal how it happened. The telescope shows that faint dwarf galaxies brought an end to the darkness.

January 18, 2024January 18, 2024 by Evan Gough

The JWST Solves the Mystery of Ancient Light

This image shows the galaxy EGSY8p7, a bright galaxy in the early Universe where light emission is seen from, among other things, excited hydrogen atoms — Lyman-alpha emission. The galaxy was identified in a field of young galaxies studied by Webb in the CEERS survey. In the bottom two panels, Webb’s high sensitivity picks out this distant galaxy along with its two companion galaxies, where previous observations saw only one larger galaxy in its place. This discovery of a cluster of interacting galaxies sheds light on the mystery of why the hydrogen emission from EGSY8p7, shrouded in neutral gas formed after the Big Bang, should be visible at all. Image Credit: ESA/Webb, NASA & CSA, S. Finkelstein (UT Austin), M. Bagley (UT Austin), R. Larson (UT Austin), A. Pagan (STScI), C. Witten, M. Zamani (ESA/Webb)

The very early Universe was a dark place. It was packed with light-blocking hydrogen and not much else. Only when the first stars switched on and began illuminating their surroundings with UV radiation did light begin its reign. That occurred during the Epoch of Reionization.

But before the Universe became well-lit, a specific and mysterious type of light pierced the darkness: Lyman-alpha emissions.

July 4, 2023July 4, 2023 by Matt Williams

James Webb is a GO for Cycle 2 Observations!

Artist conception of the James Webb Space Telescope. Credit: NASA GSFC/CIL/Adriana Manrique Gutierrez

The James Webb Space Telescope (JWST) has accomplished some amazing things during its first year of operations! In addition to taking the most detailed and breathtaking images ever of iconic celestial objects, Webb completed its first deep field campaign, turned its infrared optics on Mars and Jupiter, obtained spectra directly from an exoplanet’s atmosphere, blocked out the light of a star to reveal the debris disk orbiting it, detected its first exoplanet, and spotted some of the earliest galaxies in the Universe – those that existed at Cosmic Dawn.

Well, buckle up! The Space Telescope Science Institute (STScI) has just announced what Webb will be studying during its second year of operations – aka. Cycle 2! According to a recent STScI statement, approximately 5,000 hours of prime time and 1,215 hours of parallel time were awarded to General Observer (GO) programs. The programs allotted observation time range from studies of the Solar System and exoplanets to the interstellar and intergalactic medium, from supermassive black holes and quasars to the large-scale structure of the Universe.

June 20, 2023June 20, 2023 by Matt Williams

JWST Glimpses the Cosmic Dawn of the Universe

This still image shows the timeline running from the Big Bang on the right, towards the present on the left. In the middle is the Reionization Period where the initial bubbles caused the cosmic dawn. Credit: NASA SVS

The James Webb Space Telescope (JWST) continues to push the boundaries of astronomy and cosmology, the very job it was created for. First conceived during the 1990s, and with development commencing about a decade later, the purpose of this next-generation telescope is to pick up where Spitzer and the venerable Hubble Space Telescope (HST) left off – examining the infrared Universe and looking farther back in time than ever before. One of the chief objectives of Webb is to observe high-redshift (high-Z) galaxies that formed during Cosmic Dawn.

This period refers to the Epoch of Reionization, where the first galaxies emitted large amounts of ultraviolet (UV) photons that ionized the neutral hydrogen that made up the intergalactic medium (IGM), causing the Universe to become transparent. The best way to measure the level of star formation is the H-alpha emission line, which is visible in the mid-infrared spectrum for galaxies with high redshifts. Using data from the Mid-Infrared Instrument (MIRI), an international team of researchers was able to resolve the H-alpha line and observe galaxies with redshift values higher than seven (z>7) for the first time.

June 7, 2023June 7, 2023 by Evan Gough

JWST Shows How the Early Universe Was Furiously Forming Stars

This infrared image from NASA’s James Webb Space Telescope (JWST) was taken for the JWST Advanced Deep Extragalactic Survey, or JADES, program. It shows a portion of an area of the sky known as GOODS-South, which has been well studied by the Hubble Space Telescope and other observatories. More than 45,000 galaxies are visible here. Credits: NASA, ESA, CSA, Brant Robertson (UC Santa Cruz), Ben Johnson (CfA), Sandro Tacchella (Cambridge), Marcia Rieke (University of Arizona), Daniel Eisenstein (CfA). Image processing: Alyssa Pagan (STScI)

We can gaze out into regions in our neighbourhood of the Milky Way and find orgies of star birth. The closest region is in the Orion nebula, where astronomers have identified more than 700 young stars. They range from only 100,000 years—mere infancy for a star—to over a million years.

But we’re more than 13 billion years after the Big Bang now. What was star formation like way back when, when conditions in the Universe were so different?