Summary
By the end of this article, you will understand how a distant giant planet uses its magnetic field to ‘eat’ gas, and how scientists watch it happen in real-time.
Quick Facts
Surprise: Delorme 1 (AB)b is up to 45 million years old, an age when most planets have long finished growing!
Salient Idea: The planet is 13 times heavier than Jupiter, blurring the line between giant planet and brown dwarf.
Surprise: Gas crashes into the planet so fast it creates a massive burst of ultraviolet light.
Salient Idea: Scientists can track the 'weather' of this accretion changing over just a few hours.
The Discovery: Catching a Planet Eating
For a long time, scientists thought planets finished growing quickly. But when astronomers pointed the Very Large Telescope at Delorme 1 (AB)b, they found a Surprise: it is still actively eating gas at 30 to 45 million years old! They used a technique called spectroscopy to split the light from the planet and look at specific glowing signatures of hydrogen. They discovered a sudden burst of ultraviolet light and changing hydrogen line profiles over a few days. The Salient Idea here is that the light isn’t just glowing randomly—it changes shape and brightness based on how the gas is falling. This wasn’t just a static picture; they were watching the live action of a planet pulling in its surrounding material.
Original Paper: ‘ENTROPY II. Time series of Balmer line profiles of Delorme 1(AB)b’
This is typical of ongoing accretion on the target, confirming the accreting nature of Delorme 1 (AB)b despite its estimated old age.
— ENTROPY Survey Team
The Science Explained Simply
This is NOT just gas falling straight down like a rock dropped from a building. In space, falling gas gets caught by a planet’s magnetic field. This process is called magnetospheric accretion. The magnetic field lines act like giant, invisible slides. Gas from a surrounding disk is pulled onto these lines and gets funneled at extreme speeds toward the planet’s poles. When this gas hits the planet’s surface, it creates a massive shockwave that emits the ultraviolet light we see. By looking at the light, the scientists split the signal into two parts: the ‘wings’ (fast-moving gas on the slide) and the ‘core’ (the bright splash where it hits). This allows us to map a process we cannot physically see.
The properties of the broad component of the lines strongly support magnetospheric accretion.
— Dorian Demars
The Aurora Connection
While we love the Northern Lights on Earth, what is happening on Delorme 1 (AB)b is an aurora scaled up to extreme, violent levels. On Earth, our magnetic field catches a tiny bit of solar wind, funneling it to our poles to create beautiful, glowing lights. On this giant planet, the magnetic field is catching massive amounts of heavy, raw gas and slamming it into the planet. The physics are remarkably similar: magnetic field lines directing charged particles to the poles. Understanding how Delorme 1 (AB)b’s magnetic field controls this massive gas flow helps us understand the fundamental magnetic rules that protect our own atmosphere from being blown away.
Magnetic fields don’t just protect planets; sometimes they help build them.
— NorthernLightsIceland.com Team
A Peek Inside the Research
How do you see a magnetic field from 150 light-years away? The team used a powerful instrument called UVES to break the light into thousands of tiny slices, looking specifically at the ‘Balmer series’—the exact colors of light emitted by excited hydrogen. They built a custom algorithm to separate the light into two shapes: a ‘wings’ component and a ‘core’ component. They then matched these shapes against computer models of magnetic funnels and shockwaves. This is the Salient Idea of modern astronomy: we don’t look through telescopes with our eyes; we use code and math to decode the hidden physics inside a single beam of light.
We developed a novel method to decompose the lines into multiple components, making no assumption as to what shape they should have.
— ENTROPY Research Team
Key Takeaways
Planets can continue to grow for tens of millions of years if they hold onto a disk of material.
Magnetic fields act like funnels, directing falling gas straight into a planet's poles.
By breaking light into its colors (spectroscopy), scientists map the speed and location of invisible falling gas.
The UV light from this planet proves it is still actively feeding and creating massive shockwaves.
Sources & Further Reading
Frequently Asked Questions
Q: Why is it weird that this planet is still growing?
A: Most planets clear out their surrounding gas and dust within 3 to 10 million years. Delorme 1 (AB)b is up to 45 million years old, meaning it somehow kept a ‘Peter Pan’ disk of material that refused to grow up and disappear!
