Posted on by Brian Koberlein

What's Inside Uranus and Neptune? A New Way to Find Out

Artist expoded view of an ice giant planet similar to Uranus and Neptune. Credit: @iammoteh/Quanta magazine

In our search for exoplanets, we’ve found that many of them fall into certain types or categories, such as Hot Jupiters, Super-Earths, and Ice Giants. While we don’t have any examples of the first two in our solar system, we do have two Ice Giants: Uranus and Neptune. They are mid-size gas planets formed in the cold outer regions of the solar system. Because of this, they are rich in water and other volatile compounds, and they are very different from large gas giants such as Jupiter. We still have a great deal to learn about these worlds, but what we’ve discovered so far has been surprising, such as the nature of their magnetic fields.

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Posted on by Mark Thompson

Webb Scans Vega for Planets

Large Belt in the Vega System

To northern sky watchers, Vega is a familiar sight in the summer sky. It’s one of the brightest stars in the sky and in 2013, astronomers detected a large ring of rocky debris surrounding the planet. The prospect of planets suddenly became a real possibility so astronomers turned the James Webb Space Telescope (JWST) on the star. The hunt achieved 10 times the sensitivity of previous ground based searches but alas no planets were discovered. 

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Posted on by Matt Williams

ALMA Detects Hallmark “Wiggle” of Gravitational Instability in Planet-Forming Disk

ALMA images reveal vast spiral arms in the AB Aurigae circumstellar disk (three rightmost panels), and counterparts observed with VLT/SPHERE (leftmost panel). Credit: ALMA (ESO/NAOJ/NSF NRAO), VLT/SPHERE (ESO), Speedie et al.

According to Nebula Theory, stars and their systems of planets form when a massive cloud of gas and dust (a nebula) undergoes gravitational collapse at the center, forming a new star. The remaining material from the nebula then forms a disk around the star from which planets, moons, and other bodies will eventually accrete (a protoplanetary disk). This is how Earth and the many bodies that make up the Solar System came together roughly 4.5 billion years ago, eventually settling into their current orbits (after a few migrations and collisions).

However, there is still debate regarding certain details of the planet formation process. On the one hand, there are those who subscribe to the traditional “bottom-up” model, where dust grains gradually collect into larger and larger conglomerations over tens of millions of years. Conversely, you have the “top-down” model, where circumstellar disk material in spiral arms fragments due to gravitational instability. Using the Atacama Large Millimeter/submillimeter Array (ALMA), an international team of astronomers found evidence of the “top-down” model when observing a protoplanetary disk over 500 light-years away.

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Posted on by Evan Gough

A New Model Explains How Gas and Ice Giant Planets Can Form Rapidly

Artist's impression of a young star surrounded by a protoplanetary disc made of gas and dust. According to new research, ring-shaped, turbulent disturbances (substructures) in the disk lead to the rapid formation of several gas and ice giants. Credit: LMU / Thomas Zankl, crushed eyes media

The most widely recognized explanation for planet formation is the accretion theory. It states that small particles in a protoplanetary disk accumulate gravitationally and, over time, form larger and larger bodies called planetesimals. Eventually, many planetesimals collide and combine to form even larger bodies. For gas giants, these become the cores that then attract massive amounts of gas over millions of years.

But the accretion theory struggles to explain gas giants that form far from their stars, or the existence of ice giants like Uranus and Neptune.

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Posted on by Evan Gough

Sulphur Makes A Surprise Appearance in this Exoplanet’s Atmosphere

This artist's illustration shows the Neptune-like exoplanet GJ 3470b, which has an atmosphere rich in sulphur. The planet's atmosphere holds clues to how it and other similar planets formed. Image Credit: Department of Astronomy, UW–Madison

At our current level of knowledge, many exoplanet findings take us by surprise. The only atmospheric chemistry we can see with clarity is Earth’s, and we still have many unanswered questions about how our planet and its atmosphere developed. With Earth as our primary reference point, many things about exoplanet atmospheres seem puzzling in comparison and generate excitement and deeper questions.

That’s what’s happened with GJ-3470 b, a Neptune-like exoplanet about 96 light-years away.

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Posted on by Mark Thompson

Webb Sees Asteroids Collide in Another Star System

Asteroid collision: CREDIT:NASA/LYNETTE COOK

The James Webb Space Telescope (JWST) continues to make amazing discoveries. This time in the constellation of Pictor where, in the Beta Pictoris system a massive collision of asteroids. The system is young and only just beginning its evolutionary journey with planets only now starting to form. Just recently, observations from JWST have shown significant energy changes emitted by dust grains in the system compared to observations made 20 years ago. Dust production was thought to be ongoing but the results showed the data captured 20 years ago may have been a one-off event that has since faded suggesting perhaps, an asteroid strike!

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Posted on by Evan Gough

JWST Uses “Interferometry Mode” to Reveal Two Protoplanets Around a Young Star

Astronomers used the JWST's interferometry mode to study the PDS 70 extrasolar system. Image Credit: Blakely et al. 2024.

The JWST is flexing its muscles with its interferometry mode. Researchers used it to study a well-known extrasolar system called PDS 70. The goal? To test the interferometry mode and see how it performs when observing a complex target.

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Posted on by Evan Gough

Where Are All These Rogue Planets Coming From?

An artist's illustration of a rogue planet, dark and mysterious. Image Credit: NASA

There’s a population of planets that drifts through space untethered to any stars. They’re called rogue planets or free-floating planets (FFPs.) Some FFPs form as loners, never having enjoyed the company of a star. But most are ejected from solar systems somehow, and there are different ways that can happen.

One researcher set out to try to understand the FFP population and how they came to be.

rogue
Posted on by Evan Gough

Webb Joins the Hunt for Protoplanets

This artist’s impression shows the formation of a gas giant planet embedded in the disk of dust and gas in the ring of dust around a young star. A University of Michigan study aimed the James Webb Space Telescope at a protoplanetary disk surrounding a protostar called SAO 206462, hoping to find a gas giant planet in the act of forming. Image credit: ESO/L. Calçada

We can’t understand what we can’t clearly see. That fact plagues scientists who study how planets form. Planet formation happens inside a thick, obscuring disk of gas and dust. But when it comes to seeing through that dust to where nascent planets begin to take shape, astronomers have a powerful new tool: the James Webb Space Telescope.

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Posted on by Evan Gough

In a Distant Solar System, the JWST Sees the End of Planet Formation

This artist's illustration shows what gas leaving a planet-forming disk might look like around the T Tauri star T. Cha. Image Credit: ESO/M. Kornmesser CC BY

Every time a star forms, it represents an explosion of possibilities. Not for the star itself; its fate is governed by its mass. The possibilities it signifies are in the planets that form around it. Will some be rocky? Will they be in the habitable zone? Will there be life on any of the planets one day?

There’s a point in every solar system’s development when it can no longer form planets. No more planets can form because there’s no more gas and dust available, and the expanding planetary possibilities are truncated. But the total mass of a solar system’s planets never adds up to the total mass of gas and dust available around the young star.

What happens to the mass, and why can’t more planets form?

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