May 2025 Sky Watch
Featured Maunakea Observatory Discovery
Astronomers using the Gemini North telescope have discovered four planets orbiting Barnard’s star, the nearest single star to Earth. These four planets are only about 20-30% of the mass of Earth and orbit around Barnard’s star in a few days' time. Astronomers monitored Barnard’s star over the course of three years using the radial velocity technique, meaning they detected the subtle wobble of the star as the exoplanets gravitationally tugged on it, causing the star’s emitted light to shift subtly in wavelength. One of the planets is the least massive exoplanet ever discovered using this radial velocity technique.
These newly discovered planets most likely have a rocky composition like our Earth, rather than a gaseous composition like Jupiter. Most rocky planets discovered outside our solar system tend to be more massive than Earth, so the high likelihood that these planets are both rocky and less massive than Earth is an interesting result. The precision of the Gemini North telescope instrument for this experiment, called MAROOON-X, may lead to further discoveries of smaller, rocky planets around other stars.
Barnard’s star is classified as a red dwarf and is only around 16% of the mass of our Sun. Red dwarfs are extremely numerous in the universe and are more common than sun-like stars. Red dwarfs often host multiple, closely-packed rocky planets. The ubiquity of red dwarfs and high occurrence of rocky planetary systems make searching for exoplanets around red dwarfs a critical component for understanding how planets form. These reasons are why MAROON-X is specifically designed to look for planets around red dwarf stars.
More information can be found at this press release: https://www.gemini.edu/news/press-releases/noirlab2510
Special Events
Lāhainā Noon
Hawaiʻi residents will be treated to a unique solar phenomenon in May known as Lāhainā Noon, when objects will briefly lose their shadows as the Sun passes directly overhead through the center of the sky. Due to its proximity to the equator, Hawaiʻi experiences Lāhainā Noon twice a year — once in May and once in July — in the months before and after the Summer Solstice. This phenomenon only occurs in tropical locations on Earth. Lāhainā Noon occurs on different dates and times in the Hawaiian Islands due to slight changes in latitude. For example, Lāhainā Noon will take place at 12:20 p.m. May 17 in Kailua-Kona and 12:16 p.m. May 18 in Hilo, even though both towns are located on Hawaiʻi Island. In Honolulu, Lāhainā Noon will occur at 12:28 p.m. May 26. The exact moment of Lāhainā noon, when the Sun is at the exact center of the sky, will only last a moment. At ʻImiloa, our mosaic “Voyage of the Navigator” is positioned exactly under our sky light so that during Lāhainā noon the mosaic is perfectly illuminated by the sky light above.
Eta Aquarids Meteor Shower
This meteor shower is produced by dust particles left behind from the comet Halley. The best time to observe the shower is after midnight on the night of May 6 and morning of May 7. Most meteors will radiate from the region around the constellation Aquarius but can also appear in any part of the sky.
Evening Observing
Now as we look after sunset in our western night sky we will see Kekāomakaliʻi setting lower and lower as we continue through this month. As Kekāomakaliʻi sets it gives way for our spring and summer star line called Kaiwikuamoʻo, a significant star line used in oceanic navigation on waʻa kaulua (sailing canoes). After sunset we can see Nāhiku (The big dipper) in the Koʻolau (Northeast) quadrant rising in the house of Nālani (Declination +56.25). Following the pan handle we can see our Zenith star Hōkūleʻa (Arcturus) and looking eastward we can see Hikianalia (Spica) and even Meʻe (Corvus) in the Southeast.
Morning Observing
Early morning before sunrise you'll be able to see the famous Kamakaunuiamāui (Scorpio) in our southern night sky in the star family known as Mānaiakalani. Within this star family we have the Navigators Triangle featuring Humu (Altair), Keoe (Vega), Piraʻetea (Deneb) in the north and Pīmoe (Sagittarius) next to Mānaiakalani.
