Seven Sisters

Earlier this week, I blogged about looking at Venus passing in front of the Pleiades. If you missed it, there are nice pictures here and here. The sky is marvelous in visible light, but what we can see with the expanded range of infrared, ultraviolet, and x-ray instruments on orbit is astounding!

For example, M45, the lovely Pleiades or Seven Sisters star cluster, is well-known in astronomical images for its striking blue reflection nebulae. In visible wavelengths, the starlight is scattered and reflected by dust, but in this infrared image by the Spitzer Space Telescope, the dust itself glows. The false color image spans about 1 degree of sky (about seven light-years at the distance of the Pleiades). The densest regions of the dust cloud is shown in yellow and red hues. Data from Spitzer survey have revealed many cool, low mass stars, brown dwarfs or failed stars, and possible planetary debris disks.

Image Credit: NASA

A Starry Spider Web

Like a spider’s web swirled into a spiral, Galaxy IC 342 appears as a delicate pattern of dust. Captured in infrared light by NASA’s Spitzer Space Telescope, faint starlight gives way to the glowing bright patterns of dust found throughout the galaxy’s disk. IC 342 is relatively close by galactic standards, only about 10 million light-years away, however our vantage point places it directly behind the disk of our own Milky Way. The intervening dust makes it difficult to see in visible light, but infrared light penetrates easily.

IC 342 is nearly face-on to us, giving a clear, top-down view of the structure of its disk. It’s surface appears fairly dim compared to other spiral galaxies, indicating a lower density of stars (seen here as a blue haze). Its dust structures show up much more vividly (red). (The blue dots are stars closer to us in our own Milky Way.) New stars are forming in the disk at a rapid rate. The center glows brightly in the infrared because of an enormous burst of star formation in this tiny region. A small band of dust and gas on either side of the central region is helping to fuel the star formation.

Data from Spitzer’s infrared array camera are shown in blue (3.6 microns), green (4.5 microns) and red (5.8 and 8.0 microns).

Image Credit: NASA


The ring floating in the picture above is the size of a galaxy. In fact, it’s part of the Sombrero Galaxy, one of the largest galaxies in the nearby Virgo Cluster of Galaxies. The dark band of dust that obscures the mid-section of the Sombrero Galaxy in optical light actually glows brightly in infrared light. The digitally enhanced image above shows the infrared glow as recorded by the Spitzer Space Telescope superposed in false-color on an existing image taken by the Hubble Space Telescope in visible light. A visible light image is shown below for comparison. The Sombrero Galaxy, also known as M104, is about 50,000 light years across and roughly 28 million light years away. It can be seen with a small telescope in the direction of the constellation Virgo.

Image Credits: NASA/Spitzer and NASA/Hubble