Are there stars in Bluesky? A comparative exploratory analysis of altmetric mentions between X and Bluesky

• Bluesky mentions of scientific papers surged notably after the U.S. 2024 presidential election, especially for top multidisciplinary journals. • Bluesky overtook X in user engagement for some U.S.-based LIS journals, signaling a platform shift in certain scholarly communities. • Altmetric’s inclusion of Bluesky marks a turning point in altmetrics tracking, contrasting with its previous inaction on Mastodon. • The study developed and shared an open, DOI-based method to track Bluesky mentions, complementing Altmetric data. • Findings suggest altmetric indicators now reflect a fragmented and politically influenced landscape of scholarly communication. This study examines the shift in the scientific community from X (formerly Twitter) to Bluesky, its impact on scientific communication, and consequently on social metrics (altmetrics). We analysed 14,497 publications from multidisciplinary and Library and Information Science (LIS) journals between January 2024 and March 2025. The results reveal a notable increase in Bluesky activity for multidisciplinary journals in November 2024, likely influenced by political and platform changes, with mentions multiplying for journals like Nature and Science. In LIS, the adoption of Bluesky is different and shows marked variation between European and United States journals. Although Bluesky remains a minority platform compared to X over the whole period, when focusing on user engagement after the United States elections, we see a much more even distribution between the two platforms. In two LIS journals, Bluesky even surpasses X, while in most others, the difference in user engagement was no longer as pronounced, marking a significant change from previous patterns in altmetrics.