White Dwarfs Might Be Less Dead Than We Thought

Artist illustration of crystals forming within a white dwarf. Credit: University of Warwick/Mark Garlick

At the end of their lives, most stars including the Sun will become white dwarfs. After a red dwarf or sun-like star consumes all the hydrogen and helium it can, the remains of the star will collapse under its own weight, shrinking ever more until the quantum pressure of electrons becomes strong enough to counter gravity. White dwarfs begin their days as brilliantly hot embers of degenerate matter and grow ever cooler and dimmer as they age.

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Webb Sees a System That Just Finished Forming its Planets

An artistic impression adapted to highlight gas dispersing from a planet-forming disk. Credit: ESO/M. Kornmesser

Nearly 5 billion years ago a region of gas gravitationally collapsed within a vast molecular cloud. At the center of the region, the Sun began to form, while around it formed a protoplanetary disk of gas and dust out of which Earth and the other planets of the solar system would form. We know this is how the solar system began because we have observed this process in systems throughout the galaxy. But there are details of the process we still don’t understand, such as why gas planets are relatively rare in our system.

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Astronomers Can See the Impact Site Where an Asteroid Crashed Into a White Dwarf

This artist’s impression shows the magnetic white dwarf WD 0816-310. Credit: ESO/L. Calçada

Nothing is immortal. Everything has a finite existence, including the stars themselves. How a star dies depends on several factors, most importantly their mass. For the Sun, this means that in several billion years it will swell to a red giant as it churns through the last of its nuclear fuel. The core that remains will then collapse to become a white dwarf. Of course, the Sun is home to several planets, including Earth. What of their fate? What of ours? According to a recent study, the Sun’s death might consume Earth in the end.

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Cosmic Dust Could Have Helped Get Life Going on Earth

This artist’s impression shows dust forming in the environment around a supernova explosion. Credit: ESO/M. Kornmesser

Life on our planet appeared early in Earth’s history. Surprisingly early, since in its early youth our planet didn’t have much of the chemical ingredients necessary for life to evolve. Since prebiotic chemicals such as sugars and amino acids are known to appear in asteroids and comets, one idea is that Earth was seeded with the building blocks of life by early cometary and asteroid impacts. While this likely played a role, a new study shows that cosmic dust also seeded young Earth, and it may have made all the difference.

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We Could Snoop on Extraterrestrial Communications Networks

The Atacama Large Millimeter/submillimeter Array (ALMA). Credit: C. Padilla, NRAO/AUI/NSF

The conditions for life throughout the Universe are so plentiful that it seems reasonable to presume there must be extra-terrestrial civilizations in the galaxy. But if that’s true, where are they? The Search for Extra-terrestrial Intelligence (SETI) program and others have long sought to find signals from these civilizations, but so far there has been nothing conclusive. Part of the challenge is that we don’t know what the nature of an alien signal might be. It’s a bit like finding a needle in a haystack when you don’t know what the needle looks like. Fortunately, any alien civilization would still be bound by the same physical laws we are, and we can use that to consider what might be possible. One way to better our odds of finding something would be to focus not on a direct signal from a single world, but the broader echos of an interstellar network of signals.

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Gravastars are an Alternative Theory to Black Holes. Here's What They'd Look Like

Artist view of a black hole in the middle of solar system. Credit: Petr Kratochvil/PublicDomainPictures CC0

One of the central predictions of general relativity is that in the end, gravity wins. Stars will fuse hydrogen into new elements to fight gravity and can oppose it for a time. Electrons and neutrons exert pressure to counter gravity, but their stability against that constant pull limits the amount of mass a white dwarf or neutron star can have. All of this can be countered by gathering more mass together. Beyond about 3 solar masses, give or take, gravity will overpower all other forces and collapse the mass into a black hole.

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Even Eris and Makemake Could Have Geothermal Activity

Illustration of the icy dwarf planets Eris and Makemake. Credit: Southwest Research Institute

Whether or not you agree that Pluto isn’t a planet, in many ways, Pluto is quite different from the classical planets. It’s smaller than the Moon, has an elliptical orbit that brings it closer to the Sun than Neptune at times, and is part of a collection of icy bodies on the edge of our solar system. It was also thought to be a cold dead world until the flyby of New Horizons proved otherwise. The plucky little spacecraft showed us that Pluto was geologically active, with a thin atmosphere and mountains that rise above icy plains. Geologically, Pluto is more similar to Earth than the Moon, a fact that has led some to reconsider Pluto’s designation as a dwarf planet.

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Euclid Begins its 6-Year Survey of the Dark Universe

The areas that the space telescope Euclid will observe. Credit: ESA/Euclid/Euclid Consortium

On July 1, 2023, the Euclid Spacecraft launched with a clear mission: to map the dark and distant Universe. To achieve that goal, over the next 6 years, Euclid will make 40,000 observations of the sky beyond the Milky Way. From this data astronomers will be able to map the positions of billions of galaxies, allowing astronomers to observe the effects of dark matter.

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Another Clue Into the True Nature of Fast Radio Bursts

Artist's concept of a magnetar. Credit: NASA/JPL-Caltech

Fast radio bursts (FRBs) are strange events. They can last only milliseconds, but during that time can outshine a galaxy. Some FRBs are repeaters, meaning that they can occur more than once from the same location, while others seem to occur just once. We still aren’t entirely sure what causes them, or even if the two types have the same cause. But thanks to a collaboration of observations from ground-based radio telescopes and space-based X-ray observatories, we are starting to figure FRBs out.

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Passing Stars Changed the Orbits of Planets in the Solar System

Scholz’s Star seen from Earth 70,000 years ago. Credit: José A. Peñas/SINC

The orbit of Earth around the Sun is always changing. It doesn’t change significantly from year to year, but over time the gravitational tugs of the Moon and other planets cause Earth’s orbit to vary. This migration affects Earth’s climate. For example, the gradual shift of Earth’s orbit and the changing tilt of Earth’s axis leads to the Milankovitch climate cycles. So if you want to understand paleoclimate or the shift of Earth’s climate across geologic time, it helps to know what Earth’s orbit was in the distant past.

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