“Stars like the Sun don’t just stop shining,” but this one does

In September 2024, a star about 3,000 light-years from Earth suddenly dimmed to just one-fortieth of its normal brightness. This dramatic decline continued until May 2025. The star, known as J0705+0612, closely resembles our Sun, making the event particularly remarkable for astronomers.

“Stars like the Sun don’t just stop shining for no reason,” says Nadia Zakamska, a professor of astrophysics at Johns Hopkins University. “So dramatic dimming events like this are very rare.”

Observation Months Capture a rare event

Realizing that this unusual dimming might reveal something important, Zakamska and her colleagues began an extended observing campaign. They used the Gemini South telescope on Cerro Pachón in Chile, along with the 3.5-meter Apache Point Observatory and the 6.5-meter Magellan telescope. Their results are described in an article published in The Astronomical Journal.

By combining new observations with archival data on J0705+0612,^[1] the researchers concluded that the star was briefly hidden behind a huge, slowly drifting cloud of gas and dust. The team estimates that the cloud is located about two billion kilometers (1.2 billion miles) from the star and spans roughly 200 million kilometers (120 million miles) across.

A massive companion holds the cloud together

The data suggests that the cloud is not free-floating. Instead, it appears to be gravitationally bound to a second object orbiting the star far from its center. Although the exact nature of this companion remains uncertain, it must be massive enough to keep the cloud intact.

Observations suggest that the object has at least several times the mass of Jupiter, and possibly much more. It could be a giant planet, a brown dwarf, or an extremely low-mass star.

If the object turns out to be a star, the cloud would be considered a circumsecondary disk, meaning a debris disk orbiting a smaller member of a binary system. If it is a planet, the structure would be classified as a circumplanetary disk. In either scenario, observing a star temporarily blocked by a disk surrounding a secondary object is extremely rare, with only a few known cases.

Explore the cloud with a powerful new tool

To find out what the cloud is made of, the team turned to Gemini South’s newest instrument, the Gemini High-resolution Optical Spectrograph (GHOST). In March 2025, GHOST observed the eclipse for just over two hours, splitting the starlight into a detailed spectrum that reveals features in the cloud.

“When I started observing the eclipse using spectroscopy, I hoped to reveal something about the chemical composition of the cloud, because no such measurements had been made before. However, the result exceeded all my expectations,” says Zakamska.

The spectra revealed several metals – elements heavier than helium – mixed into the gas. More remarkably, the precision of the data allowed the team to see how the gas moved in three dimensions. It was the first time scientists had directly measured the internal motions of gas in a disk orbiting a secondary object, such as a planet or a low-mass star.

The measurements show an active and turbulent environment with winds of gaseous metals including iron and calcium flowing through the cloud.

“The sensitivity of GHOST allowed us not only to detect the gas in this cloud, but also to actually measure how it is moving,” says Zakamska. “That’s something we’ve never been able to do before in a system like this.”

“This study illustrates the considerable power of Gemini’s newest facility, GHOST,” notes Chris Davis, NSF’s program director for NOIRLab, “and further highlights one of Gemini’s great strengths — responding quickly to transient events like this eclipse.”

The evidence points to a disk on an external system

Detailed wind measurements show that the cloud moves independently of the star itself. Combined with the long duration of the dimming, this confirms that the object blocking the star is the disk surrounding a secondary companion that orbits in the outer regions of the system.

The star also shows an excess of infrared radiation, which is often associated with disks of material around young stars. However, J0705+0612 is more than two billion years old, so it is unlikely that the disk is leftover material from the system’s original formation.

A possible planetary collision

Do I know where the disc came from? Zakamska suggests that it may have formed after a large collision between two planets in the outer part of the system. Such an impact could have ejected huge amounts of dust, rock and gas, creating the massive cloud we now see drifting in front of the star.

Why this discovery matters

The findings show how the new instruments open new avenues for studying hidden and short-lived phenomena in distant planetary systems. In particular, GHOST allows astronomers to examine structures that previously could not be examined in detail.

“This event shows us that even in advanced planetary systems, large-scale dramatic collisions can still occur,” says Zakamska. “It’s a living reminder that the universe is far from static – it’s an ongoing story of creation, destruction and transformation.”

Comment

1. A study using archival data from Harvard found that J0705+0612 underwent two other similar dimming events in 1937 and 1981, establishing a period of 44 years.

The team consists of Nadia L. Zakamska (Johns Hopkins University, Institute for Advanced Study), Gautham A. Pallathadka (Johns Hopkins University), Dmitrij Bizyaev (New Mexico State University, Moscow State University), Jaroslav Merc (Charles University, Institute of Astrophysics of the Canary Islands), James E. Owen (ImperialG Henrie College London), James E. Observatory/NSH HenrieFmini College NOIRLab), Kevin C. Schlaufman (Johns Hopkins University), Karolina Bąkowska (Michael Copernicus University in Toruń), Sławomir Bednarz (Silesian University of Technology), Krzysztof Bernacki (Silesian University of Technology), Agnieszka Gurgul (Michael Copernicus University in Toruń), Kirsten A Torustrophysics University | Harvard & Smithsonian), Franz-Josef Hambsch (Association for Astronomy, Meteorology, Geophysics and Allied Sciences, German Association for Variable Stars), Barbara Joachimczyk (Nicolas Copernicus University in Toruń), Krzysztof Kotysz (University of Warsaw), Alexgios Sebastian University in Wrocanowski (National Observatory in Athens), Przemysław J. Mikołajczyk (University of Warsaw, National Center for Nuclear Research, Univ. in Wroclaw), Erika Pakštienė (University of Vilnius), Grzegorz Pojmański (University of Warsaw), Adam Popowicz (Silesian Technical University), Daniel E. Republika Chapelart University of North Carolina Wyrzykowski (University of Warsaw, National Center for Nuclear Research), Justas Zdanavičius (University of Vilnius), Michał Żejmo (University of Zielona Gora), Paweł Zieliński (University of Mikulášeník Koper in Toruń) and Staszek Zola (Jagiellonian University).

NSF NOIRLab, the US National Science Foundation’s center for ground-based optical infrared astronomy, operates the Gemini International Observatory (facilities of NSF, NRC-Canada, ANID-Chile, MCTIC-Brazil, MINCyT-Argentina, and KASI-Republic of Korea), NSF Kitt Peak National Observatory (CerSFlo-AKPLO To N observatory ToroAKPNO) Community Science and Data Center (CSDC), and NSF-DOE Vera C. Rubin Observatory (in collaboration with DOE’s SLAC National Accelerator Laboratory). It is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with NSF and is located in Tucson, Arizona.

The scientific community is honored to have the opportunity to conduct astronomical research I’oligam Du’ag (Kitt Peak) in Arizona, Hon Maunakea in Hawaii and on Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the very important cultural role and respect I’oligam Du’ag Tohono O’odham Nation, a Maunakea to Kanaka Maoli community (of native Hawaiians).