Jason Momoa and Dwayne "The Rock" Johnson have been protesting against the building of a giant telescope on top of a mountain that some Hawaiians consider sacred.
Over the last few weeks both stars joined protestors at the base of the dormant volcano, Mauna Kea mountain on the Big Island of Hawaii.
Johnson, who voices Maui in the animated film Moana, lived in Hawaii as a child, while Aquaman star Momoa was born there.
Protestors have been blocking access to Mauna Kea's summit for weeks to prevent the construction of the observatory, called the Thirty Meter Telescope (TNT).
Mauna Kea is the tallest mountain in the world when measured from its underwater base.
Scientists say the conditions on its summit are perfect for viewing the skies and a powerful telescope on the summit could be used to view far off galaxies.
Supporters of the Thirty Meter TNT project say the powerful new telescope could bring in hundreds of jobs.
But The $1.4bn (£1.1bn) project is not popular with everyone in Hawaii and protesters say it will disturb sacred land and cause environmental damage.
The mountain is a temple to native Hawaiians, offering a connection between "creation and creator", said Kealoha Pisciotta, President of one of the main groups opposing the TMT.
There are already 13 telescopes on Mauna Kea, but they are a lot smaller and at the height of 18 floors, the telescope would be the tallest building on Hawaii.