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Gemini Cuts Deep Into Galactic Core with Release of First Data

October 16, 2000

The first scientific observations from the Gemini North telescopeprovide a dramatic glimpse into the elusive core of the Milky Way,including an intriguing bow-shock from a star as it plows into apoorly understood gas cloud a mere 3 light-years from the galacticcenter.


Long-suspected of harboring a huge black hole, the center of the MilkyWay is a beehive of activity, with hapless stars flung around the coreat tremendous speeds.

"There has a been a buzz of increased interest by astronomers latelyin looking at the properties of the core," says UCLA AstronomerDr. Andrea Ghez, whose work over several years at the W.M. KeckObservatory is responsible for pinpointing the exact location of thecentral black hole. "With this excellent science-quality data, Geminihas demonstrated its many unique capabilities for studying our galaxyand beyond. It is a remarkable new tool in our toolbox for exploringthe universe."

The vast extent and extreme clarity of the Gemini infrared imagesoffer tantalizing hints that the center of our galaxy is home to evenmore exotic objects than once believed, at least one of which Geminihas revealed clearly for the very first time.

The object, known by the unglamorous name of IRS8, was only anill-defined smudge until Gemini came along. Now, the Geminitelescope's advanced optics show that IRS8 appears to be a star thatis plowing through a poorly understood gas and dust cloud near thegalactic center. Moving relative to the cloud, the star creates avery obvious bow-shock wave, similar to the wave that forms in frontof a boat as it goes through water.

This finding could alter our understanding of the center of our galaxyonce astronomers determine how the star and gas cloud are movingrelative to each other. By studying this interaction, the propertiesof the gas cloud and the conditions surrounding the star will bebetter understood and provide a valuable new tool for probing theintense conditions near the center of our galaxy.

The image released today represents only a fraction of the total dataavailable to scientists from this study. "Never before have we seensuch a large area of the galactic center this clearly," saidDr. François Rigaut of the Gemini Observatory who led theproject. "The data is also being released to scientists world wideregardless of affiliation so that astronomers can make the most ofthis data as quickly as possible."

However, it will still take some time before astronomers will be ableto dig out all of the treasures buried in this initial digital goldmine of data. "This is the first scientific data to be released tothe astronomical community by the Gemini Observatory," says DirectorDr. Matt Mountain, "and to be able to release such a spectacularimage and data set shows the tremendous potential of thesetelescopes."

The data was taken at several infrared wavelengths and combined tocreate a "color" image. The remarkable sharpness of the image is dueto a technology called adaptive optics that actually corrects fordistortions to starlight caused by turbulence in the Earth'satmosphere (more details onadaptive optics). The adaptive optics instrument used iscalled Hokupa`a, on loan to Gemini from the University of HawaiiInstitute for Astronomy, where it was built and funded through a grantby the National Science Foundation.

Observing the galactic center is especially difficult because itslight must travel through thousands of light-years of gas and dustbefore we can see it from our perch in the galactic suburbs. Only asmall portion of the light ever makes it to our planet and most ofthat is in the infrared (or heat) part of the spectrum. The GeminiObservatory has been designed to make the most of the trickle ofinfrared radiation from space by using sophisticated new technologieslike adaptive optics and infrared optimization that capitalize on theideal infrared conditions at Mauna Kea.

The data were obtained over several nights in July and August as partof a preliminary science testing period as the Gemini North telescopenears completion on Mauna Kea in Hawaii.

The Gemini 8-meter Observatory Project is a multi-nationalcollaboration that will provide two nearly identical 8-metertelescopes to an international community of astronomers. Bothtelescopes will incorporate new technologies that allow large,relatively thin mirrors to collect and focus both optical and infraredradiation from space - at times with even more clarity than ispossible with the Hubble Space Telescope. The telescopes are locatedon Hawaii's Mauna Kea (Gemini North) and on Cerro Pachón in centralChile (Gemini South), and hence will provide full sky coverage.Gemini North is nearing scientific operations early in the year 2001and Gemini South will follow about six months later. More informationon the Gemini Observatory can be found at

The Gemini Observatory provides the astronomical communities in eachpartner country with state-of-the-art astronomical facilities thatwill allocate observing time in proportion to each country'scontribution. In addition to financial support, each country alsocontributes significant scientific and technical resources. Thenational research agencies that form the Gemini partnership include:the US National Science Foundation (NSF), the UK Particle Physics andAstronomy Research Council (PPARC), the Canadian National ResearchCouncil (NRC), the Chilean Comisión Nacional de InvestigaciónCientifica y Tecnológica (CONICYT), the Australian ResearchCouncil (ARC), the Argentinean Consejo Nacional de InvestigacionesCientíficas y Técnicas (CONICET) and the Brazilian ConselhoNacional de Desenvolvimento Científico e Tecnológico (CNPq). TheObservatory is managed by the Association of Universities for Researchin Astronomy, Inc. (AURA) under a cooperative agreement with the NSF.The NSF also serves as the executive agency for the internationalpartnership.

Video b-roll available through Gemini partner country offices.