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.
One of the most significant constraints on the size of objects placed into orbit is the size of the fairing used to put them there. Large telescopes must be stuffed into a relatively small fairing housing and deployed to their full size, sometimes using complicated processes. But even with those processes, there is still an upper limit to how giant a telescope can be. That might be changing soon, with the advent of smart materials – particularly on a project funded by NASA’s Institute for Advanced Concepts (NIAC) that would allow for a kilometer-scale radio telescope in space.
In the coming decade, multiple space agencies and commercial space providers are determined to return astronauts to the Moon and build the necessary infrastructure for long-duration stays there. This includes the Lunar Gateway and the Artemis Base Camp, a collaborative effort led by NASA with support from the ESA, CSA, and JAXA, and the Russo-Chinese International Lunar Research Station (ILRS). In addition, several agencies are exploring the possibility of building a radio observatory on the far side of the Moon, where it could operate entirely free of radio interference.
For years, researchers have advocated for such an observatory because of the research that such an observatory would enable. This includes the ability to study the Universe during the early “Cosmic Dark Ages,” even before the first stars and galaxies formed (about 50 million years after the Big Bang). While there have been many predictions about what kind of science a lunar-based radio observatory could perform, a new research study from Tel Aviv University has predicted (for the first time) what groundbreaking results this observatory could actually obtain.
The Moon will be a popular destination for space programs worldwide in the coming years. By 2025, NASA’s Artemis III mission will land the first astronauts (“the first woman and first person of color”) onto the lunar surface for the first time since the end of the Apollo Era, over fifty years ago. They will be joined by multiple space agencies, as per the Artemis Accords, that will send European, Canadian, Japanese, and astronauts of other nationalities to the lunar surface. These will be followed in short order by taikonauts (China), cosmonauts (Russia), and vyomanauts (India), who will conduct similarly lucrative research and exploration.
Having facilities in orbit of the Moon, like the Artemis Base Camp, the International Lunar Research Station, and others, will enable all manner of scientific research that is not possible on Earth or in Earth orbit. This includes radio astronomy, which would be free of terrestrial interference on the far side of the Moon and sensitive enough to detect light from previously unexplored cosmological periods. This is the purpose of a pathfinder project known as the Lunar Surface Electromagnetics Experiment-Night (LuSEE-Night) that will leave for the Moon next year and spend the next 18 months listening to the cosmos!
One of the main objectives of the James Webb Space Telescope (JWST) is to use its powerful optics and advanced instruments to observe the earliest galaxies in the Universe. These galaxies formed about 1 billion years after the Big Bang, coinciding with the end of what is known as the “Cosmic Dark Ages.” This epoch is inaccessible for conventional optical telescopes because the only sources of photons were largely associated with the relic radiation of the Big Bang – visible today as the Cosmic Microwave Background (CMB) – or were the result of the reionization of neutral hydrogen (visible today the 21 cm line).
Thanks to its advanced optics and infrared imaging capabilities, Webb has pushed the boundaries of how far astronomers and cosmologists can see. One of the most interesting finds was Maisie’s galaxy, which appeared to have existed roughly 390 million years after the Big Bang. According to a new study by the Cosmic Evolution Early Release Science Survey (CEERS) that recently appeared in Nature, these results have since been confirmed. This makes Maisie’s galaxy one of the farthest (and earliest) confirmed galaxies ever observed by human eyes.
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?
According to the most widely-accepted cosmological theories, the Universe began roughly 13.8 billion years ago in a massive explosion known as the Big Bang. Ever since then, the Universe has been in a constant state of expansion, what astrophysicists know as the Hubble Constant. For decades, astronomers have attempted to measure the rate of expansion, which has traditionally been done in two ways. One consists of measuring expansion locally using variable stars and supernovae, while the other involves cosmological models and redshift measurements of the Cosmic Microwave Background (CMB).
Unfortunately, these two methods have produced different values over the past decade, giving rise to what is known as the Hubble Tension. To resolve this discrepancy, astronomers believe that some additional force (like “Early Dark Energy“) may have been present during the early Universe that we haven’t accounted for yet. According to a team of particle physicists, the Hubble Tension could be resolved by a “New Early Dark Energy” (NEDE) in the early Universe. This energy, they argue, would have experienced a phase transition as the Universe began to expand, then disappeared.
The frontiers of astronomy are being pushed regularly these days thanks to next-generation telescopes and scientific collaborations. Even so, astronomers are still waiting to peel back the veil of the cosmic “Dark Ages,” which lasted from roughly 370,000 to 1 billion years after the Big Bang, where the Universe was shrouded with light-obscuring neutral hydrogen. The first stars and galaxies formed during this same period (ca. 100 to 500 million years), slowly dispelling the “darkness.” This period is known as the Epoch of Reionization, or as many astronomers call it: Cosmic Dawn.
By probing this period with advanced radio telescopes, astronomers will gain valuable insights into how the first galaxies formed and evolved. This is the purpose of the Hydrogen Epoch of Reionization Array (HERA), a radio telescope dedicated to observing the large-scale structure of the cosmos during and before the Epoch of Reionization located in the Karoo desert in South Africa. In a recent paper, the HERA Collaboration reports how it doubled the array’s sensitivity and how their observations will lead to the first 3D map of Cosmic Dawn.
The scientific and astronomical community are eagerly waiting for Tuesday, July 12th, to come around. On this day, the first images taken by NASA’s James Webb Space Telescope (JWST) will be released! According to a previous statement by the agency, these images will include the deepest views of the Universe ever taken and spectra obtained from an exoplanet atmosphere. In another statement issued yesterday, the images were so beautiful that they almost brought Thomas Zarbuchen – Associate Administrator for NASA’s Science Mission Directorate (SMD) – to tears!
The fields of astronomy and astrophysics are poised for a revolution in the coming years. Thanks to next-generation observatories like the James Webb Space Telescope (JWST), scientists will finally be able to witness the formation of the first stars and galaxies in the Universe. In effect, they will be able to pierce the veil of the Cosmic Dark Ages, which lasted from roughly 370,000 years to 1 billion years after the Big Bang.