An international team of astronomers has discovered more than 100 new extrasolar planets using data from the Kepler Space Telescope. The planets were confirmed and characterized by a suite of ground-based telescopes, including four telescopes on Maunakea. Six astronomers from the University of Hawaii (UH) contributed to the international team of 44 scientists from seven countries.
The new planets range in size from smaller than Earth to larger than Jupiter. All of the planets orbit close to their host stars, and many of the stars show evidence for multiple planets. One star hosts four planets that are just bigger than the Earth, two of which have estimated temperatures similar to Earth.
"The diversity of planets is astounding. We're finding planets where we don't see them in our Solar System," said Evan Sinukoff, a graduate student at the Institute for Astronomy (IfA) at UH. "For example, we discovered many planets about twice the size of the Earth orbiting so close to their host stars that they are hotter than 1000 degrees."
Image montage showing the Maunakea Observatories, Kepler Space Telescope, and night sky with K2 Fields and discovered planetary systems (dots) overlaid. An international team of scientists discovered more than 100 planets based on images from Kepler operating in the K2 Mission. The team confirmed and characterized the planets using a suite of telescopes worldwide, including four on Maunakea (the twin telescopes of Keck Observatory, the Gemini-North Telescope, and the Infrared Telescope Facility). The planet image on the right is an artist's impression of a representative planet. Credit: Art by Karen Teramura (UHIfA) based on night sky image of the ecliptic plane by Miloslav Druckmuller and Shadia Habbal, and Kepler Telescope and planet images by NASA.
After the Kepler space telescope revealed more than 4,000 planets during its initial four-year survey, NASA modified the mission due to the malfunction of two of the spacecraft's reaction wheels that maintain its precise orientation in space. With this revised K2 mission, the telescope no longer stares at one small patch of sky, instead scanning a much larger portion of the Milky Way. As with the original Kepler mission, K2 discovers planets by measuring the tiny decrease in a star's brightness caused by a planet passing in front of the star during its orbit. The new planets are from K2's first five Fields in the sky.
"K2 casts a wide net for planets," said Ian Crossfield of the University of Arizona and the lead author of the team's paper. "The mission has been spectacularly successful at finding planets, particularly planets orbiting stars called red dwarfs that are cooler than the Sun."
Four telescopes on Maunakea in Hawaii played crucial roles in confirming and characterizing the new worlds. The twin telescopes of Keck Observatory, the Gemini-North Telescope, and the NASA Infrared Telescope Facility (IRTF) contributed images and spectra of the planets' host stars. This allowed the astronomers to verify that the planets are real and not spurious signals in the Kepler images. Data from the ground-based telescopes were also used to precisely measure crucial properties of the planets including their sizes and temperatures. Additional facilities that contributed to the effort include the Robo-AO system led by IfA Astronomer Christoph Baranec, and other telescopes in California, Arizona, and Chile.
"This study shows the great value of Maunakea and the synergy of the best telescopes on the ground and in space," said Andrew Howard, an astronomer at IfA who contributed to the study.
With the number of known planets now in the thousands, these hundred new planets are valuable because they orbit relatively nearby and bright stars that are easier to study. The team is already making more detailed measurements of the planets using Keck Observatory, the Hubble Space Telescope, and the Spitzer Space Telescope. These planets are also possible future targets for the Thirty Meter Telescope (TMT) and NASA's James Webb Space Telescope (JWST).
"My group has targeted twenty of the new K2 planets for observations with Keck Observatory to measure their masses and estimate their compositions," said Howard. "One day I hope that we can measure properties of the planets' atmospheres with TMT."
The six astronomers from IfA that contributed are Evan Sinukoff, Andrew Howard, B. J. Fulton, Christoph Baranec, Mike Liu, and Kimberly Aller. For a full list of authors and funding information, please see the research paper, "197 Candidates and 104 Validated Planets in K2's First Five Fields," which has been accepted by the Astrophysical Journal Supplement and is available for download at https://www.lpl.arizona.edu/~ianc/docs/crossfield_K2s_new_planets.pdf.
Founded in 1967, the Institute for Astronomy at the University of Hawaii at Manoa conducts
research into galaxies, cosmology, stars, planets, and the
sun. Its faculty and staff are also involved in astronomy education,
deep space missions, and in the development and management
of the observatories on Haleakala and Maunakea. The Institute operates facilities on the islands of Oahu, Maui, and Hawaii.