A Brief History of the Discovery of Cosmic Voids

An artist's impression of the cosmic web, the filamentary structure that fills the entire Universe. Credit: M. Weiss/CfA

At first the sum total of large, orderly structure in the Universe appeared to arrive in two categories. There were the clusters of galaxies – an unoriginal but descriptive name – each a dense ball with anywhere from a few dozen to a few hundred galaxies, all bound together by their mutual gravitational embrace. And then there were the field galaxies, lonely wanderers set apart and adrift from the clusters, not bound to anyone but themselves. That was it: the clusters of galaxies, the field galaxies, and the megaparsecs of emptiness that enveloped them all.

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Astronomers Prepare for the Next Thousand Years of Hazardous Asteroid Impacts

This diagram shows the orbits of 2,200 potentially hazardous objects as calculated by JPL’s Center for Near Earth Object Studies (CNEOS). Highlighted is the orbit of the double asteroid Didymos, the target of NASA’s Double Asteroid Redirect Test (DART) mission. Credit: NASA/JPL-Caltech

It is as inevitable as the rising of the Sun and the turning of the tides. Someday another large rock from space will crash into the Earth. It has happened for billions of years in the past and will continue to happen for billions of years into the future. So far humanity has been lucky, as we have not had to face such a catastrophic threat. But if we are to survive on this planet for the long term, we will have to come to terms with the reality of hazardous asteroids and prepare ourselves.

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Astronomers Find a “Red Nova”: A Main-Sequence Star Just Eating its Planet

Artist's impression of a Jupiter-sized exoplanet orbiting an M-dwarf star

Back in 2020 astronomers observed a Red Nova, which while enormously powerful, is on the low side of energetic events in the universe. Now an astronomer has studied the event in close detail and has come to the conclusion that we have just witnessed a star destroying its own planet.

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What Cassini’s “Grand Finale” Taught Us About Saturn’s Interior

Six years ago the Cassini spacecraft, which had spent nearly two decades in orbit around Saturn, finished its mission with a grand finale, plunging itself into the depths of Saturn’s atmosphere. Those last few orbits and the final plunge revealed a wealth of information about Saturn’s interior. A team of astronomers have collected all of the available data and are now painting a portrait of the interior of the solar system’s second largest planet.

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Black Holes Might be Defects in Spacetime

Artist view of a binary black hole system. Credit: LIGO/Caltech/MIT/Sonoma State (Aurore Simonnet)

A team of theoretical physicists have discovered a strange structure in space-time that to an outside observer would look exactly like a black hole, but upon closer inspection would be anything but: they would be defects in the very fabric of the universe.

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This Star Might be Orbiting a Strange “Boson Star”

Illustration of a merger of two boson stars. Credit: Nicolás Sanchis-Gual and Rocío García Souto

A team of astronomers has claimed that observations of a sun-like star orbiting a small black hole might actually be the indication of something far more exotic – the existence of a boson star, a star composed entirely of dark matter.

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We Might be able to Find Evidence for Modified Gravity…in the Earth

Artist's impression of Earth's interior structure. Credit: Argonne National Labs

Testing the possibility of models of gravity different from general relativity may be closer to home than we think. A team of researchers has proposed that we might be able to use seismic motions in the Earth itself to test for modified gravity.

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Primordial Black Holes May Have “Frozen” the Early Universe

Artist's logarithmic scale conception of the observable universe with the Solar System at the center, inner and outer planets, Kuiper belt, Oort cloud, Alpha Centauri, Perseus Arm, Milky Way galaxy, Andromeda galaxy, nearby galaxies, Cosmic Web, Cosmic microwave radiation and the Big Bang's invisible plasma on the edge. Credit: Wikipedia Commons/Pablo Carlos Budassi

Primordial holes formed in the exotic conditions of the big bang may have become their own source of matter and radiation.

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