Astronomy January 2021

The world's best-selling astronomy magazine offers you the most exciting, visually stunning, and timely coverage of the heavens above. Each monthly issue includes expert science reporting, vivid color photography, complete sky coverage, spot-on observing tips, informative telescope reviews, and much more! All this in a user-friendly style that's perfect for astronomers at any level.

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United States
Kalmbach Publishing Co. - Magazines
US$ 44,99
12 Edições

nesta edição

2 minutos
the beginning and the end

When my colleague Steve George suggested we do something really special with the January issue of Astronomy, I immediately thought of cosmology. What hadn’t been done as a cosmic theme before? Well, how about the entire chronological history of the universe, from start to finish? That was an ambitious target, but what you hold in your hands is the result, and I hope you will enjoy it very much. In this issue, we explore summaries of what is known about the history of the universe, starting with the Big Bang through to the present, and also look forward all the way to the end of the cosmos. In between, we explore what fascinates us most about the universe: the fact that we’re living beings within it. How did life arise on Earth?…

6 minutos
it began with a bang

Over the course of the past century, astronomers and physicists have produced an incredibly rich and detailed account of our universe’s history. In 13.8 billion years, our universe has expanded and transformed from the hot and dense state that we call the Big Bang into the vast cosmos that we find ourselves living in today This picture is not based on mere speculation or theorizing, but is solidly grounded in an enormous body of empirical evidence. We have directly measured how our universe has expanded and evolved over the past several billion years, as well as how galaxies and clusters of galaxies formed. Looking back even further in time, we have scrutinized the light that was released during the formation of the first atoms, only 380,000 years after the Big Bang.…

8 minutos
inflating the universe

Cosmologists are confident the Big Bang accurately describes the universe we see today. But they are less sure of what came before. Stephen Hawking considered this inquiry pointless, like asking “What’s south of the South Pole?” While often conflated, the Big Bang and the origin of time are distinct epochs. But what happened before the Big Bang may have laid the foundations for what came after. The Big Bang theory describes the era starting when the lightest elements were formed — called Big Bang nucleosynthesis (BBN; see “The emergence of matter,” page 18) — until today, where distant objects are receding at great velocities. BBN is currently the last epoch of certainty, the final stage in reverse cosmic history where the underlying forces of nature were similar to physics accessible to modern-day…

6 minutos
the emergence of matter

Nearly 2,500 years ago, the Greek philosopher Democritus first proposed that objects are made of countless indivisible building blocks called atoms (Greek: atomos). However, it wasn’t until about 200 years ago, with the work of English chemist and physicist John Dalton, that the modern idea of atoms was developed. Next came the challenge of learning to identify and distinguish between the various types of atoms. During the 19th century, advancements in spectroscopy — studying light by breaking it down into its constituent components — allowed scientists to discover that specific elements and molecules each have distinct spectral signatures. These signatures reveal themselves through unique combinations of emission and absorption lines (extra light and missing light, respectively) for each element. And by the mid-19th century, shortly after researchers first started classifying elements…

7 minutos
the cosmic dark ages

The early universe was a place of extremes. It was inconceivably small and scorching, with all the energy and matter there would ever be crammed into a tiny space a billion times hotter than the center of the Sun. In the first moments after the Big Bang, the universe cooled enough to allow fundamental particles — such as quarks and electrons — to spring into being. Quarks combined to form protons and neutrons and, not long after, the nuclei of deuterium, helium, and lithium were formed. Energy zipped around the infant universe in the form of photons, but that early light ricocheted off free electrons, which weren’t yet bound to any atom, at every turn. Fast-forward another 380,000 years, and the universe had cooled enough to allow the early nuclei to…

9 minutos
the first stars are born

For 380,000 years after the Big Bang, the cosmos was a hot, dense mixture of protons, electrons, other elementary particles, and light elements. But the expanding universe was cooling fast. And once the temperature dropped to about 4,950 degrees Fahrenheit (2,730 degrees Celsius), protons and electrons were able to form atoms. Not all atoms, mind you. No gold was floating around, or aluminum, or even elements as light as oxygen. Hydrogen and its heavy isotope deuterium accounted for about threequarters of everything. A couple of isotopes of helium accounted for most of the other quarter. And a tiny fraction (about one-billionth of everything) of lithium had also been produced. Just because brand-new hydrogen and helium were swirling about doesn’t mean stars were popping into existence. In fact, the first of those luminous…