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A new investigation with NASA’s James Webb Space Telescope into K2-18 b, an exoplanet 8.6 times as massive as Earth, has revealed the presence of carbon-bearing molecules including methane and carbon dioxide. Webb’s discovery adds to recent studies suggesting that K2-18 b could be a Hycean exoplanet, one which has the potential to possess a hydrogen-rich atmosphere and a water ocean-covered surface.

Scientists have been working on models of planet formation since before we knew exoplanets existed. Originally guided by the properties of the planets in our Solar System, these models turned out to be remarkably good at also accounting for exoplanets without an equivalent in our Solar System, like super Earths and hot Neptunes. Add in the ability of planets to move around thanks to gravitational interactions, and the properties of exoplanets could usually be accounted for.

Today, a large international team of researchers is announcing the discovery of something our models can't explain. It's roughly Neptune's size but four times more massive. Its density—well above that of iron—is compatible with either the entire planet being almost entirely solid or it having an ocean deep enough to drown entire planets. While the people who discovered it offer a couple of theories for its formation, neither is especially likely.

In their jiggles and shakes, red giant stars encode a record of the magnetic fields near their cores.

In their jiggles and shakes, red giant stars encode a record of the magnetic fields near their cores.

A new NASA study offers an explanation of how quakes could be the source of the mysteriously smooth terrain on moons circling Jupiter and Saturn.

Astronomers have uncovered a link between Neptune's shifting cloud abundance and the 11-year solar cycle, in which the waxing and waning of the Sun's entangled magnetic fields drives solar activity.

Giant black holes were supposed to be bit players in the early cosmic story. But recent James Webb Space Telescope observations are finding an unexpected abundance of the beasts.

Magnetars are some of the most extreme objects we know about, with magnetic fields so strong that chemistry becomes impossible in their vicinity. They're neutron stars with a superfluid interior that includes charged particles, so it's easy to understand how a magnetic dynamo is maintained to support that magnetic field. But it's a little harder to fully understand what starts the dynamo off in the first place.

The leading idea, which benefits from its simplicity, is that the magnetar inherits its magnetic field from the star that exploded in a supernova to create it. The original magnetic field, when crushed down to match the tiny size of the resulting neutron star, would provide a massive kick to start the magnetar off. There's just one problem with this idea: we haven't spotted any of the highly magnetized precursor stars that this hypothesis requires.

It turns out that we have been observing one for years. It just looked like something completely different, and it took a more careful analysis, published today in Science, to understand what we've been observing.

New observations of a faraway rocky world that might have its own magnetic field could help astronomers understand the seemingly haphazard magnetic fields swaddling our solar system’s planets.

When JAXA’s Hayabusa-1 spacecraft delivered samples from asteroid Ryugu to Earth in late 2020, anticipation was high. What could the space rock possibly be waiting to tell us?

Asteroids are time capsules of the Solar System, containing material from early in its history. As a 2021 study found, the Ryugu samples contained carbon, nitrogen, and oxygen, all necessary ingredients for life, and a 2022 study discovered evidence of water (and possibly a subsurface lake) that had long since dried up. Ryugu and its parent body were also revealed to carry some of the most ancient rocks in the Solar System. However, the pieces of this asteroid still had more to say.

It turned out that two of the Ryugu samples each had a shard of something that visually stood out. Researchers discovered they were seeing fragments, or clasts, of rock with a chemical composition that differed from the rest of Ryugu. These clasts were higher in sulfur and iron, but lower in oxygen, magnesium, and silicon. That meant they could not have possibly formed with Ryugu, so they had to have been acquired through a later impact; but the asteroid still had more to say.

By measuring the universe’s emptiest spaces, scientists can study how matter clumps together and how fast it flies apart.

Four years from now, if all goes well, a nuclear-powered rocket engine will launch into space for the first time. The rocket itself will be conventional, but the payload boosted into orbit will be a different matter.

NASA announced Wednesday that it is partnering with the US Department of Defense to launch a nuclear-powered rocket engine into space as early as 2027. The US space agency will invest about $300 million in the project to develop a next-generation propulsion system for in-space transportation.