This month, we'll take a closer look at the cosmic microwave background. Sometimes called 'the afterglow of creation', this extremely faint microwave glow is considered one of the most convincing pieces of evidence for the Big Bang theory. But how is it that we are still observing this ancient light?
As we've seen in earlier parts of this series, space is expanding. Since the amount of matter in the Universe remains fairly constant, the increasing volume means that the average density of cosmic matter is decreasing over time. That means the density of the Universe must have been much higher in the distant past.
Right after the Big Bang, before there were any galaxies, stars or planets, elementary particles were packed almost shoulder to shoulder, and the corresponding temperature was unimaginably high. This hot, dense plasma produced energetic radiation. However, individual light particles - photons - have trouble traversing such plasma-filled environments, as they are continuously absorbed (and re-emitted) by charged particles like electrons. In other words: the hot, early Universe was opaque.
Cosmic treasure trove
Leftover radiation from the explosion is key to unlocking the Universe around us
Esta historia es de la edición May 2023 de BBC Sky at Night Magazine.
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Esta historia es de la edición May 2023 de BBC Sky at Night Magazine.
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Could We Find Aliens by Looking for Their Solar Panels?- Designed to reflect ultraviolet and infrared, the panels have a unique fingerprint
Researchers searching for life beyond Earth spend a lot of time thinking about what telltale signs might be detectable astronomically. Forms of unambiguous evidence for the presence of life on another world are known as biosignatures. By extension, techno signatures are indicators of activity by intelligent, civilisation-building life.
Antimatter- In our continuing series, Govert Schilling looks at antimatter, the strange counterpart to most of the matter filling our Universe
Particles and corresponding antiparticles are very much alike, except they have opposite electrical charges. For instance, the antiparticle of the electron - known as the positron - has the same tiny mass, but while electrons carry a negative electrical charge, positrons are positively charged.
Where Have All The Milky Way's Early Stars Gone?- Our Galaxy has a curious lack of pristine stars
The Big Bang produced a Universe filled almost exclusively with hydrogen and helium; all other elements - what astronomers call metals - were produced by stars, supernovae and everything that happens later. So if you can pick out a pristine star with no metals polluting it from among the billions in the Milky Way, then you are likely to have a star dating from our Galaxy's earliest days.
Inside The Sky At Night - Two years ago, exoplanet scientist Hannah Wakeford received some of the first data from the JWST
Two years ago, exoplanet scientist Hannah Wakeford received some of the first data from the JWST. In July's Sky at Night, we discovered what she's learned since then.
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Easily combine multiple frames to boost detailin your astro photos
Lunar occultation of Saturn
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How to plot a variable star light curve
A rewarding project to chart stars that change brightness
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Once-a-century solar storm is overdue
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The new era of human spaceflight
There's been a step-change in crewed space missions since the dawn of the 21st century. Ben Evans charts its course and looks ahead to future horizons
