Caption

Details of a simulated image of the Andromeda galaxy highlight the high resolution of WFIRST imagery. Unlike a typical wide field camera, which can cover a large area of sky but cannot reveal fine details, WFIRST will provide both a large field of view and high resolution. The details shown here each cover about 0.0013 square degrees of sky, the equivalent to a single infrared image from Hubble’s WFC3 camera. The pixel scale is 0.11 arcseconds/pixel.

The pull-out detail on the left shows the diversity of populations in the disk. The bright blue stars are young, recently formed hot populations that tend to be in association, while the red stars are the old stars that are well-mixed throughout the disk.

The middle pull-out shows a thick cloud of dust in the disk. Near the center of the detail, the dust is thick enough that there are noticeably fewer stars detected, even in the near infrared, which penetrates more dust than optical light.

The right pull-out shows another mix of populations, but this time the young blue stars are spread along a relatively linear structure. There is also an example of a background galaxy in the lower middle portion of the image.

This simulated image was made using high-resolution near-infrared data collected by Hubble for the Panchromatic Hubble Andromeda Treasury (PHAT) program. Researchers used the PHAT imagery to compile a catalog of stars in the field of view. The color and brightness data were then fed into a computer program that models the corresponding output from WFIRST, based on the design of the telescope and its instruments.

One notable difference between WFIRST and Hubble is wavelength range: the colors they can detect. While Hubble covers the full spectrum of visible light, along with near ultraviolet and near infrared, WFIRST is limited to the near infrared and the red end of the visible spectrum. The colors used in this image are not the colors that our eyes would see: blue represents visible red light (0.62 microns); green represents very near infrared light (1.06 microns); and red represents near-infrared light (1.58 microns).