Astronomers observing a seemingly ordinary middle-aged star noticed something unexpected unfolding.

For nearly nine months, the star faded to just a fraction of its normal brightness as a giant cloud drifted over its surface. The cloud was tangled with vaporized metal moving at high speed.

The long-lasting solar eclipse provided an unusual view into the interior of a mature planetary system that would have been quiet by now.

Rather, the observations point to violent activity occurring long after planet formation is thought to be complete, suggesting that destructive collisions and hidden companions can still reshape old star systems.

The event began in September 2024, when the star J0705+0612 suddenly became about 40 times fainter and remained dimmer until May 2025.

As the eclipse drags on, astronomers Johns Hopkins University They realized that what they were witnessing was not a fluctuation in the stars.

Instead, they saw massive, metal-rich structures connected to invisible companions, and perhaps the aftermath of a massive collision between planets.

clouds darken the stars

The dimming is occultation: There was no sudden change within the star itself, but a passing disk or cloud that blocked the star for several months.

By comparing new measurements with older records, the researchers tracked how the clouds moved and how thick the dust remained.

Estimates are that the cloud is about 1.2 billion miles from the star and about 120 million miles wide.

The cloud appears to be associated with a hidden companion star with at least several times the mass of Jupiter, making the candidates planet-to-planet-sized. brown dwarf.

Tracking debris around a star

In March 2025, the Gemini South Telescope in Chile will open the Gemini High-Resolution Optical Spectrometer (ghost) Capture the dim light of stars in detail.

By spreading the light across thousands of wavelengths, the instrument converted the faint signal into a detailed chemical map.

Small changes in these spectral lines reveal Doppler motion, subtle shifts in wavelength caused by gas moving toward or away from Earth, allowing researchers to measure speed and direction within the cloud.

Since the observation period was just over two hours, the researchers used other telescopes to track how the lunar eclipse evolved.

The spectrum contained clear traces of metals, heavier elements. heliumit was embedded in a gas that was far from static. GHOST showed how metal-rich gas flows through clouds instead of staying in place.

“The sensitivity of GHOST allowed us to not only detect the gas in this cloud, but actually measure how it was moving,” said study co-author Nadia Zakamska, a professor of physics and astronomy at Johns Hopkins University.

The gas moves differently than the star, strengthening the theory that this material belongs to the disk around the invisible companion star.

dust that shouldn’t remain

The system appears ancient in many ways, with the stars estimated to be more than 2 billion years old.

However, in previous observations, infrared excessThis means that the system was emitting more heat-like infrared radiation than could be explained by the star alone.

Classical studies suggest that most young stars lose their disks within about 6 million years, much earlier than the estimated age of this system.

This discrepancy suggests that the dust surrounding J0705+0612 was replenished late rather than remaining from its birth.

Repeating star shadow

Older images showed the same star fading in 1937 and 1981, so the 2024 dimming did not occur in isolation.

These records, preserved on photographic plates at Harvard University, showed an approximately 44-year cycle that applied to all three dimming events.

This long period suggests that the obscure object travels through the star’s outer system, where orbital periods span decades. There are only three events so far, but we still need time and monitoring to see patterns and refine them.

Fragments tied to something invisible

The researchers argued that the cloud behaved like a disk orbiting a companion star, rather than a drifting, free-floating mass.

Such a circumferential disk is a piece of debris that surrounds a small companion star and can remain bound even at great distances from the host star. Only a few similar phenomena are known because seeing it cross in front of the star requires a rare alignment.

That rarity makes each well-measured case valuable, but it also means the sample is too small to establish broad trends.

when planets collide violently

One explanation linked these parts together. The cloud may have formed when two planets collided in the outer reaches of a star system. Violent planetary collisions can evaporate material on the surface. hot gas It then spreads the dust over a wider orbit.

“This event shows that even in mature planetary systems, dramatic large-scale collisions are still possible,” Zakamska said.

If that explanation is correct, the cloud is younger than the star, and the companion star could be a survivor.

Testing the collision theory

Some important details remain unclear, particularly the true mass of the companion star and whether the metallic absorption lines are caused by stellar winds or rapid rotation.

High-resolution spectra taken after the star returns to normal brightness could help answer that question by showing which lines remain and which disappear with the clouds.

Observations at submillimeter wavelengths – longer than infrared light but shorter than most light radio waves – It could also expose cold gas and dust that the star’s glow currently hides.

Until testing is complete, the cloud remains a rare clue rather than a clear explanation of the system’s evolution.

Taken together, the dim, metal-rich gas and repeated cycles point to a long-lived disk formed by a violent past.

Future spectra and cold wavelength maps may test the idea of ​​a collision and ultimately reveal whether the invisible companion star is planet-mass or something larger.

This study astronomical journal.

Image credit: International Gemini Observatory/NOIRLab/NSF/AURA/P. Mullenfeldt & M. Zamani

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