The text and images in this article were originally published on March 6, 2003, and reflect information about the Milky Way available at that time.
Hubble’s Virtual Journey to the Center of Our Milky Way Galaxy
Peering deep into the heart of our Milky Way galaxy, NASA’s Hubble Space Telescope reveals a rich tapestry of more than half a million stars. Except for a few blue, foreground stars, the stars are part of the Milky Way’s nuclear star cluster, the most massive and densest star cluster in our galaxy. So packed with stars, it is equivalent to having a million suns crammed into the volume space between us and our closest stellar neighbor, Alpha Centauri. At the very hub of our galaxy, this star cluster surrounds the Milky Way’s central supermassive black hole, which is about 4 million times the mass of our sun.
Astronomers used Hubble’s infrared vision to pierce through the dust in the disk of our galaxy that obscures the star cluster. In this image, scientists translated the infrared light, which is invisible to human eyes, into colors our eyes can see. The red stars are either embedded or shrouded by intervening dust. Extremely dense clouds of gas and dust are seen in silhouette, appearing dark against the bright background stars. These clouds are so thick that even Hubble’s infrared capability could not penetrate them.
Hubble’s sharp vision allowed astronomers to measure the movements of the stars over four years. Using this information, scientists were able to infer important properties such as the mass and structure of the nuclear star cluster. The motion of the stars may also offer a glimpse into how the star cluster was formed—whether it was built up over time by globular star clusters that happen to fall into the galaxy’s center, or from gas spiraling in from the Milky Way’s disk to form stars at the core.
This picture, spanning 50 light-years across, is a mosaic stitched from nine separate images from Hubble’s Wide Field Camera 3. The center of the Milky Way is located 27,000 light-years away. The “snowstorm” of stars in the image is just the tip of the iceberg: Astronomers estimate that about 10 million stars in this cluster are too faint to be captured in this image.
This image was created from archival data of the Milky Way Center from multiple science proposals led by Tuan Do and Andrea Ghez from UCLA. STScI Research and Instruments Analyst Varun Bajaj was instrumental in mosaicking the multiple pointings together and working on the color composite of the WFC3 data.
Featured Image Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)
Acknowledgment: T. Do and A. Ghez (UCLA), and V. Bajaj (STScI)
Fast Facts about the Milky Way
About this Object
| Object Name: | Galactic Center |
| Object Description: | Center of the Milky Way Galaxy |
| Position (J2000): | R.A. 17h 45m 36.00s Dec. –28° 55‘ 58.8″ |
| Constellation: | Sagittarius |
About the Data
| Data Description: | The HST data were taken from proposals 13049, 12663, and 12182 PI: T. Do (UCLA) and 11671 PI: A. Ghez (UCLA). The science team comprises T. Do, A. Ghez, and M. Morris (UCLA), R. Schodel (Instituto de Astrofisica de Andalucia), J. Lu (University of Hawaii), W. Clarkson (University of Michigan), D. Merritt (RIT), B. Hansen and S. Yelda (UCLA), J. Bullock (University of California, Irvine), J. Anderson (STScI), L. Meyer, E. Mills, and N. McCrady (UCLA), and J.-U. Pott (Max Planck Insititue for Astronomy, Heidelberg). |
| Instrument: | WFC3/IR |
| Filters: | F127M (H2O/CH4 continuum), F139M (H2O/CH4 line), and F153M (H2O and NH3) |
| Exposure Date: | 2010–2014 |
About this Image
| Image Credit: | NASA, ESA, and the Hubble Heritage Team (STScI/AURA) |
| Release Date: | March 6, 2003 |
| Color: | This image is a composite of separate exposures acquired by the WFC3/IR instrument. Several filters were used to sample various wavelengths. The color results from assigning different hues (colors) to each monochromatic (grayscale) image associated with an individual filter. In this case, the assigned colors are: F127M (H2O/CH4 continuum) – blue F139M (H2O/CH4 line) – green F153M (H20 and NH3) – red |
Additional Images of the Center of the Milky Way Galaxy
Draft Composite 
Filter Comparison 
Scale/Orientation
Four-Panel Zoom into the Galactic Core
This four-panel graphic zooms into the Hubble Space Telescope view of the galactic core. The first panel shows a wide view of the Milky Way in visible light. The second panel, which zooms into the boxed area in the first panel, shows interstellar dust obscuring much of the view of the core. The third panel zooms in yet again, but the view shifts to infrared light that penetrates the dust and exposes the core. Finally, the fourth panel is a close-up of the galactic core as seen in infrared by the Hubble Space Telescope. The locator mark in the middle designates the galaxy’s nucleus, which is home to a central, supermassive black hole.
Credit: NASA, ESA, and Z. Levay (STScI)
Acknowledgment: NASA, ESA, A. Fujii, Digitized Sky Survey (DSS), STScI/AURA, Palomar/Caltech, UKSTU/AAO, NASA/JPL-Caltech/S. Stolovy (Spitzer Science Center/Caltech), the Hubble Heritage Team (STScI/AURA), T. Do and A. Ghez (UCLA), and V. Bajaj (STScI)
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