jeudi 31 mars 2016

Hubble’s Journey to the Center of our Galaxy












ESA - Hubble Space Telescope logo.

March 31, 2016


Image above: Hubble's infrared vision pierced the dusty heart of our Milky Way galaxy to reveal more than half a million stars at its core. 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. Image Credits: NASA, ESA, and Hubble Heritage Team (STScI/AURA, Acknowledgment: T. Do, A.Ghez (UCLA), V. Bajaj (STScI).

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 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.


Images above: This annotated, infrared image from the Hubble Space Telescope shows the scale of the galactic core. The galaxy's nucleus (marked) is home to a central, supermassive black hole called Sagittarius A-star. Images Credits: NASA, ESA, and the Hubble Heritage Team (STScI/AURA) Acknowledgment: T. Do, A.Ghez (UCLA),V. Bajaj (STScI).

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.

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Zoom in to the galactic centre

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.

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Panning across the galactic centre

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.

For images and more information about the Milky Way Nuclear Star Cluster and Hubble, visit:

    https://www.spacetelescope.org/
    http://hubblesite.org/
    http://www.nasa.gov/hubble

Images (mentioned), Text, Credits: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)/Acknowledgment: NASA, ESA, T. Do and A. Ghez (UCLA), and V. Bajaj (STScI)/Videos Credits: Risinger/Guisard/ ESO/Hubble, Music: Johan B. Monell.

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