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The Many Colors of M87

When creating a color astronomical image, image processors at the Space Telescope Science Institute use single-filtered datasets and combine them in various orders to produce the desired effect. M87 is a galaxy that is made up of stars. Stars emit light in all visible wavelengths. By combining filters that cover broad areas of the optical and near-infrared portion of the spectrum, M87 looks like the image at right.



Three-arcminute-Hubble Telescope image centered around M87 (courtesy Hubble Heritage Team).

A wider optical field centered on M87 shows the neighboring galaxies in the center of the Virgo Cluster.




Wide-field ground-based image of Virgo Cluster centered around M87 (courtesy R. Gendler). Note that the optical jet is located within the center of M87 and is not visible in this image.
Click on image for larger view.

If optical data were combined with X-ray and radio observations of the same field, the resultant image of M87 would look like this.

The peculiar appearance of M87 has much to do with the black hole and high-energy particle jet being emitted from the core of the galaxy.





Learn more about the M87 Multi-wavelength Composite Image

By looking at the center of M87 and viewing just the jet in white light- it looks uncolorful. However, by using filters that allow light to be received at the telescope based on the motion of particles in the jet and the direction they are traveling toward our line of sight- the image is much more colorful. Place the cursor on the image below to see the same object in polarized light.

M87 optical jet in white and polarized light.
[Place Mouse on Image]

What's going on in this image?

In this image taken with the Hubble Space Telescope's Advanced Camera for Surveys High Resolution Camera. The image is a false-color composite of visible light images taken through three different polarization filters, each one of which allows light polarized in a specific direction to pass through it. Each of the polarized light images is rendered in either red, green or blue and then combined to produce the image shown. In contrast to the center of the galaxy which appears white much of the jet appears highly colorized because most of the light from it is polarized. The color changes gradually as one moves along the length of the jet, indicating that the polarization direction is also changing gradually.

The polarization filters are much like the ones used in ordinary sunglasses which allow one to avoid the bright glare of sunlight reflecting off a road or water surfaces. Ordinary starlight consists of light waves in which the vibrations of the electromagnetic energy which make up these waves are transverse to the direction in which the light is traveling. For unpolarized light, these vibrations are randomly oriented at all angles. But when light waves are reflected or scattered off something, only waves with vibrations along a preferred orientation reach our eyes, and the light is said to be polarized along that orientation.