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Hubble's patchwork
of proplyds

DR EMILY BALDWIN
ASTRONOMY NOW
Posted: December 14, 2009


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A collection of 30 never before seen images of embryonic planetary systems – proplyds – in the Orion Nebula represent the longest single Hubble Space Telescope project ever dedicated to studies of star and planet formation.

Hubble's patchwork of proplyds, the first results from a HST Treasury Program. Image: NASA, ESA and L. Ricci (ESO).

Proplyds are thought to be young planet systems in the making. As newborn stars emerge from the nebulous gas and dust of star-forming regions like the heart of the Orion Nebula, discs form around them. While the spinning disc generates heat to become a new star, remnants around the far reaches of the disc attract clumps of dust.

Using Hubble's Advanced Camera for Surveys, astronomers have observed 42 such protoplanetary discs, identifying two regions where these discs are forming: those that lie near to the cluster's brightest star Theta 1 Orionis C and those further away. Those near to this bright star are being heated up, causing them to shine brightly, while further away where such energetic radiation is lacking they can only be detected as dark silhouettes. These still have a lot to offer, however, allowing astronomers to characterize the properties of the dust grains that are thought to bind together and possibly form planets like our own.

Six proplyds are highlighted in this stunning image of the Orion Nebula. Image: NASA, ESA, M. Robberto (Space Telescope Science Institute/ESA), the Hubble Space Telescope Orion Treasury Project Team and L. Ricci (ESO).

All of the discs appear in random orientations with glowing cusps of material facing the bright star but some appear edge on while others are face on. Other eye-catching features include emerging jets of matter and shock waves formed when the stellar wind from the nearby massive star collides with the gas in the nebula to sculpt a variety of shapes, notably arrow- and boomerang-like structures in the patchwork image seen here.

It is relatively rare to see visible images of proplyds, but the high resolution and sensitivity of Hubble and the Orion Nebula’s proximity to Earth leant itself to such study. The new proplyd atlas is the first scientific outcome from a long-duration HST Treasury Program, which are carried out to allow scientists to conduct comprehensive studies over longer periods of time than usual.

The Atacama Large Millimeter/submillimeter Array (ALMA), one of the largest ground-based astronomy projects of the next decade is set to pick up the baton by observing the proto-planetary dust at longer wavelengths in emission (instead of in absorption as seen here at optical wavelengths) and with an angular resolution up to 10 times better than that of Hubble.

To find out more about the Hubble Space Telescope, see our special publication, Hubble Reborn.