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.
One hundred years ago, we didn’t know there was anything outside of our own galaxy, the Milky Way. Now we know that our puny planet Earth, and everything else, is part of a vast structure called the Cosmic Web. Its scale is difficult to comprehend in any concrete way, and the system’s complexity and magnitude brings our most powerful supercomputers to their knees.
Astronomers have known about the Cosmic Web for some time, as they’ve caught glimpses of it. But a new instrument has given us our most complete view of it yet.
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.
Like Gravitational Waves (GWs) and Gamma-Ray Bursts (GRBs), Fast Radio Bursts (FRBs) are one of the most powerful and mysterious astronomical phenomena today. These transient events consist of bursts that put out more energy in a millisecond than the Sun does in three days. While most bursts last mere milliseconds, there have been rare cases where FRBs were found repeating. While astronomers are still unsure what causes them and opinions vary, dedicated observatories and international collaborations have dramatically increased the number of events available for study.
The Small Magellanic Cloud (SMC) is over 200,000 light-years away, yet it’s still one of our galaxy’s closest neighbours in space. Ancient astronomers knew of it, and modern astronomers have studied it intensely. But the SMC still holds secrets.
By studying it and revealing its structure in more detail, astronomers at The Australian National University hope to grow our understanding of the SMC and galaxies in general.
A team of researchers has discovered a complex network of filamentary structures in the Milky Way. The structures are made of atomic hydrogen gas. And we all know that stars are made mostly of hydrogen gas.
Not only is all that hydrogen potential future star-stuff, the team found that its filamentary structure is also a historical imprint of some of the goings-on in the Milky Way.
A team of scientists working with the Murchison Widefield Array (WMA) radio telescope are trying to find the signal from the Universe’s first stars. Those first stars formed after the Universe’s Dark Ages. To find their first light, the researchers are looking for the signal from neutral hydrogen, the gas that dominated the Universe after the Dark Ages.
The universe wasn’t always such a well-lit place. It had its own Dark Ages, back in the days before stars and galaxies formed. One of the big questions in astronomy concerns how stars and galaxies shaped the very early days of the Universe. The problem is, there’s no visible light travelling through the Universe from this time period.