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Dragon of deep space

Visible and infrared images of M17 Swex

Before and after. The top half shows a visible light image of the region of space known as M17 Swex, while the bottom half is an infrared image of the same region, taken with the Spitzer Space Telescope. Details are revealed that are completely unseen at visible wavelengths.

A new infrared image from NASA’s Spitzer Space Telescope (above) shows what appears to be a dragon-shaped cloud of dust flying out from a bright explosion in space (bottom half), a creature that is entirely cloaked in shadow when viewed in visible part of the spectrum (top half).

The image has revealed that this dark cloud, called M17 SWex, is forming stars at a furious rate but has not yet spawned the most massive type of stars, known as O stars.

Such stellar behemoths, however, light up the M17 nebula at the image’s centre and have also blown a huge “bubble” in the gas and dust to the left of M17.

See the full-size infrared image here (1.1MB, will open in a new window).

The stars and gas in this region are passing though the Sagittarius spiral arm of the Milky Way (moving from right to left), touching off a galactic star-forming “domino effect.”

Stars are formed when interstellar gas clouds collapse in on themselves, often driven by pressure or shockwaves from outside.

The youngest episode of star formation is playing out inside the dusty dragon as it enters the spiral arm. Over time, this area will flare up like the bright M17 nebula to the left of the dragon, glowing in the light of young, massive stars.

The remnants of an older burst of star formation blew the bubble in the region to the far left, called M17 EB.

The different parts of M17 Swex

Stars and gas are moving through the Sagittarius spiral arm, sparking off star formation episodes.

The visible-light view of the area clearly shows the bright M17 nebula, as well as the glowing hot gas filling the “bubble” to its left. However the M17 SWex “dragon” is hidden within dust clouds that are opaque to visible light.

It takes an infrared view to catch the light from these shrouded regions and reveal the earliest stages of star formation.

Cold spacecraft takes hot pictures

The Spitzer Space Telescope comprises a 0.85-metre diameter telescope and three science instruments that perform imaging and spectroscopy in the 3–180 micron wavelength range.

Since infrared is primarily heat radiation, detectors are most sensitive to infrared light when they are kept extremely cold. Using the latest in large-format detector arrays, Spitzer has made observations that are more sensitive than any previous mission.

Artist's impression of the Spitzer Space Telescope

Artist's impression of the Spitzer Space Telescope (left) and a diagram showing its component parts.

Spitzer launched on 25 August 2003, but its coolant fluid has now run out. Now in an extended mission phase known as the Spitzer Warm Mission, the telescope continues to operate, but with some small limitations due to its not-as-cold-anymore status.

The telescope is surrounded by an outer shell that radiates heat to cold space in the anti-Sun direction, and is shielded from the Sun by the solar panel assembly. Intermediate shields intercept heat from the solar panel and the spacecraft bus, or main structure.

The outer shell and inner, middle, and outer shields were vapour cooled—ie. the cold helium vapour from the helium tank was used to carry away the heat from these structures—prior to the expiration of the coolant fluid.

The spacecraft bus contains the subsystems required for housekeeping and control engineering: telecommunications, reaction control, pointing control, command and data handling, and power. The star tracker and gyro package is mounted on the spacecraft bus. The main antenna is located at the rear of the spacecraft bus. Control thrusters are located on outriggers from the spacecraft bus.

Adapted from information issued by NASA / JPL-Caltech / Penn State / DSS.

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