June 2025 Sky Watch
Featured Maunakea Observatory Discovery
Astronomers using the W. M. Keck Observatory analyzed the vibrations of a star to learn more about its interior, almost as if listening to the star’s music. The study used the Keck Planet Finder (KPF), an extremely high-precision instrument to detect very slight oscillations rippling through the star. This new instrument has enabled astronomers to listen to vibrations of stars that were once too quiet to be detected.
Stars resonate at natural frequencies that astronomers can “hear” with the right tools. By analyzing these frequencies, astronomers can learn about a star’s interior and other properties such as size and age. It is analogous to how geologists learn about Earth’s interior from earthquakes. This field is known as asteroseismology. Most asteroseismology studies focused on stars that are hotter than our Sun because cooler stars have very subtle vibrations, which previously were too quiet to detect. The Keck Planet Finder precisely measures the motion of the stellar surface towards and away from Earth. As its name suggests, the Keck Planet Finder’s primary science case is to detect planets orbiting other stars, but it can also be used for asteroseismology studies of cool stars.
Astronomers collected 2,000 ultra-precise measurements of the star HD 219134 located just 21 light-years away to analyze its natural frequencies. They learned that the star is 10.2 billion years old, more than twice the age of our Sun. Additionally, they determined the star to be smaller than expected. These discoveries have important implications for determining how stars age over time. Additionally, HD 219134 has planets of its own. By getting a better understanding of the star's physical properties, astronomers were able to place better constraints on the density of the orbiting planets, suggesting that they have Earth-like compositions with solid, rocky surfaces. More information can be found at this Keck Observatory press release.
Special Events
June Solstice
June 21 marks the Northern Hemisphere’s Summer Solstice, when the Earth’s North Pole is at its maximum tilt towards the Sun. On this day, the Northern Hemisphere experiences its longest period of daylight. Conversely, this is the first day of winter in the Southern Hemisphere.
Evening Observing
Kaiwikuamoʻo, a significant star line used in oceanic navigation on waʻa kaulua (sailing canoes), will dominate the night sky at the zenith point as the sun sets. After sunset, as we look toward the direction of hikina (east), we can see Humu (Altair), Keoe (Vega), and Piraʻetea (Deneb) rising in the star houses of Manu Koʻolau and Lā Koʻolau, forming our “Navigator’s Triangle.” South of our celestial equator, we can observe Mānaiakalani (Scorpio) rising across the houses of ʻĀina Malanai, Noio Malanai, and Manu Malanai. The summer/fall star line spans 101.25 degrees of our eastern horizon.
Morning Observing
Just before sunrise, around 4:00 a.m., our fall/winter starline called: Kalupeakawelo (The kite of Kawelo) will be near the zenith before the sun breaks through the eastern horizon. Within this star line we can see constellations such as ʻIwakealiʻi (Cassiopeia) and Ka Mōʻī (Cephus) in our northern sky.
