HONOLULU—The mood is different this year at the General Assembly of the International Astronomical Union (IAU), the largest gathering of astronomers, which meets every three years. Amid the usual scientific posters and talks on the history of the solar system and galaxy formation here at the Hawaii Convention Center are alert sentries at every entrance diligently screening for protesters. The normally benign field of astronomy finds itself embroiled in controversy around the planned construction of one of the world’s most powerful telescopes on the peak of Mauna Kea, a dormant volcano with ideal conditions for observation that is also a sacred place to Native Hawaiians.

The intended facility, called the Thirty Meter Telescope (TMT) after its gargantuan primary mirror’s size, would be the 13th observatory on Mauna Kea and by far the largest. Protesters see construction on the mountain as the desecration of a holy place that has long held meaning for Hawaiians. They object to the presence of any telescopes there, and especially to the prospect of building a new observatory with a larger footprint than the rest. Protesters have so far succeeded in preventing the start of construction on the 4,200-meter peak by camping and blocking the access road to the summit. They are planning peaceful demonstrations during the IAU meeting, including a press conference held outside the convention center Tuesday morning and a scheduled march through Waikiki on Sunday.

“We are not here to protest astronomy,” movement leader Lanakila Mangauil said during the press conference. “The mountain is simply a poor choice of location … Before we look into space, we need to take care of this place, this land.” Some Hawaiians find themselves torn between loyalty to their culture and interest in scientific development. “Because of TMT I’ve gotten the opportunity to come up here [to Mauna Kea],” says Alexis Acohido, an intern working with the Gemini North telescope, also on Mauna Kea, who has Native Hawaiian ancestry and has written in support of the TMT. “I’ve been called a bad Hawaiian.” The governor of Hawaii, David Ige, spoke at the conference’s opening ceremony Monday, asking people on both sides to work toward compromise. “We do not seem to be talking with each other, but rather at each other,” he said. “I believe there can be a resolution. We need to begin by listening to each other—truly listening—and trying to understand perspectives entirely different than our own. I am committed to that path and ask you to join me on it.”

The IAU, the largest professional astronomy organization, is officially neutral in the debate over the $1.5 billion TMT, which is being planned by scientists from the University of California and the California Institute of Technology with support from China, Japan, Canada and India. “What the union can do in this case is only to foster and encourage people to dialogue and to try to find together a reasonable solution to the problem,” Piero Benvenuti, general secretary-elect of the IAU, said Monday at a press conference. “We don’t want to ignore the protest. We just hope that it doesn’t interfere with the normal [operations] of the assembly.”

The conference has drawn nearly 3,000 astronomers from around the world for scientific presentations and poster sessions on astronomy, astrophysics, planetary science and cosmology. IAU members will also vote on resolutions to standardize measurements of stellar brightness and other technical issues as well as plans for fostering astronomy in the developing world and protecting radio astronomy from car radar interference. And because the IAU controls the official names of astronomical bodies, the convention will announce the nominees for monikers to be given to many of the exoplanets that have been discovered beyond the solar system over the past two decades. The IAU will open voting on candidate names to the public next week.

Organizers have also planned two evenings of stargazing open to the public, as well as visits by local students to the conference and several public lectures, such as one on Tuesday night by a practitioner of Native Hawaiian celestial navigation. “We are trying to progress in the knowledge of the universe because we believe this is a value for mankind,” Benvenuti said. “Our goal is progressing in knowledge, but the knowledge has to be shared with everybody.”