By the numbers

Princeton astronomers who are members of a new research partnership with Japanese scientists are working intensively this spring on preparations to start an exciting sequence of observations to probe the universe.

Researchers from the University are participating in a collaboration with the National Astronomical Observatory of Japan (NAOJ), announced in January, in which they will use new instrumentation on the Hawaii-based Subaru Telescope to peer into space, near and far. The partnership is called the NAOJ-Princeton Astrophysics Collaboration.

Scientists involved with the project are focused on final engineering tests and other checks before beginning actual science operations, which are slated to commence in late fall. The High Contrast Coronagraphic Imager with Adaptive Optics (HiCIAO) will detect extrasolar planets and also look for material orbiting stars that can harbor the raw material that can spawn planets. Researchers who will use the Hyper Suprime-Cam (HSC), a digital camera that captures deep images of large swaths of the sky, are developing the instrument design and detailed plans for the survey.

• The 10-year project will involve Princeton faculty members, postdoctoral fellows and students from departments including astrophysical sciences, mechanical and aerospace engineering, and operations research and financial engineering.

• The Subaru Telescope, whose name is the Japanese word for the Pleiades star cluster, is one of the largest telescopes in the world. The primary mirror of the optical infrared telescope is 27 feet across. The telescope is 72 feet high and weighs 612 tons.

• The telescope is located on the summit of Mauna Kea, a dormant volcano in Hawaii at an elevation of 13,580 feet. The isolated peak protrudes above most of the Earth’s weather, making the site one of the best on the planet for astronomical observing. The skies are clear enough for viewing about two-thirds of the time. There are 13 telescopes at or near the peak. The Subaru Telescope, which is owned and operated by NAOJ, is located at a latitude of 20 degrees north, which gives it a good view of a large fraction of the sky, including much of the southern hemisphere.

• Using HiCIAO, scientists will be looking for planets, hidden in the glare of the star they orbit. Finding these planets is a crucial step in answering the age-old question of the existence of extraterrestrial life. Scientists have discovered about 335 planets orbiting more than 284 different stars (some stars are circled by multiple planets) by indirect means but have directly imaged only four or five such planets. Researchers using the Subaru are targeting about 500 stars that could be orbited by previously unknown planets.

• The scientists will be studying how galaxies form and change over time to learn how they developed the properties observed in the present-day universe. According to scientific estimates, there are about 100 billion galaxies in the observable universe and about 100 billion stars per galaxy. Astronomers believe that galaxies started forming somewhere between 100 million and 1 billion years after the explosive beginning of the universe.

• They also will be scouring the distant universe to discern the properties of the hypothesized substance known as dark energy. About 73 percent of the universe is thought to be composed of dark energy. About 23 percent of the remainder is hypothesized to be made of dark matter with the remaining 4 percent composed of ordinary matter.

• The studies will be made possible by a new generation of instruments specially designed and built for the Subaru telescope. They include the HSC camera, which will be equipped with 800 million pixels to give it extraordinary viewing capabilities, and the HiCIAO, which is designed to detect faint objects near a bright star by masking its far more intense light. With the HiCIAO camera, a planet with an orbit around the star as large as that of the Earth around the sun could be distinguished from the much brighter star at a distance of about 180 trillion miles. Put another way, the camera will have the power to view a dime at a distance of 25 miles. It is designed to pick out planets that are between 300,000 to 1 million times fainter than the stars they orbit.