Space Butterfly
Ssc2019 04a

Credit: NASA/JPL-Caltech

Observation • March 27th, 2019 • ssc2019-04a


What looks like a red butterfly in space is in reality a nursery for hundreds of baby stars, revealed in this infrared image from NASA's Spitzer Space Telescope. Officially named W40, the butterfly is a nebula - a giant cloud of gas and dust in space where new stars may form. The butterfly's two "wings" are giant bubbles of hot, interstellar gas blowing from the hottest, most massive stars in this region.

The material that forms W40's wings was ejected from a dense cluster of stars that lies between the wings in the image. The hottest, most massive of these stars, W40 IRS 1a, lies near the center of the star cluster.

W40 is about 1,400 light-years from the Sun, about the same distance as the well-known Orion nebula, although the two are almost 180 degrees apart in the sky. They are two of the nearest regions in which massive stars - with masses upwards of 10 times that of the Sun - have been observed to be forming.

The W40 star-forming region was observed as part of a Spitzer Legacy Survey, and the resulting mosaic image was published as part of the MYStIX (Massive Young stellar clusters Study in Infrared and X-rays) survey of young stellar objects.

The Spitzer picture is composed of four images taken with the telescope's Infrared Array Camera (IRAC) in different wavelengths of infrared light: 3.6, 4.5, 5.8 and 8.0 m (shown as blue, green, orange and red). Organic molecules made of carbon and hydrogen, called polycyclic aromatic hydrocarbons (PAHs), are excited by interstellar radiation and become luminescent at wavelengths near 8.0 microns, giving the nebula its reddish features. Stars are brighter at the shorter wavelengths, giving them a blue tint. Some of the youngest stars are surrounded by dusty disks of material, which glow with a yellow or red hue.

NASA's Jet Propulsion Laboratory, Pasadena, California, manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at Caltech in Pasadena, California. Spacecraft operations are based at Lockheed Martin Space Systems Company, Littleton, Colorado. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA.

About the Object

Nebula > Type > Star Formation
Nebula > Appearance > Emission
Nebula > Appearance > Dark
1,400 Light Years

Color Mapping

Band Wavelength Telescope
Infrared 3.6 µm Spitzer IRAC
Infrared 4.5 µm Spitzer IRAC
Infrared 5.8 µm Spitzer IRAC
Infrared 8.0 µm Spitzer IRAC


Position (J2000)
RA =18h 30m 53.2s
Dec = -2° 11' 45.6"
Field of View
1.1 x 0.7 degrees
North is 14.5° left of vertical