About the Object

Category:	MIRI NIRCam Picture of the Month Stars

Oph 163131 (annotated close-up)

This shining disc is named Oph 163131, and it’s one of two protoplanetary discs featured for this month's ESA/Webb Picture of the Month. Also catalogued as 2MASS J16313124-2426281, it is located about 480 light-years away in our galaxy, in the constellation Ophiuchus. Its close location, almost edge-on inclination of 85 degrees (where 90 would be perfectly edge-on) and its considerable size of 66 billion kilometres across — several times wider than our Solar System — make it an excellent target for studying these kinds of planet-forming discs.

At the centre of Oph 163131 is a newly formed star that’s still wrapped in a thick disc of gas and dust. Eventually the new star will disperse all the dust with its ferocious radiation, but before that happens there’s a chance for the dust to clump together and grow into pebbles, planetesimals and eventually planets — hence, a protoplanetary disc. Whether planets appear, and what kind of planets they are, depends on how larger and smaller dust grains migrate in the disc. An edge-on view like this shows us if dust grains are settling into a layer of large dust grains at the core of the disc. Such a layer is critical for dust grains to further grow and begin forming planets, and the thicker it is, the better.

This image of Oph 163131 combines near- and mid-infrared data from Webb’s NIRCam and MIRI instruments with visible light captured by the NASA/ESA Hubble Space Telescope and radio waves from the Atacama Large Millimeter/submillimeter Array (ALMA). Where Hubble and Webb each image tiny dust grains only micrometres across, ALMA sees larger dust grains that are about a milimetre in size, which are concentrated in the central plane of the disc. Combined with the very slightly off-edge perspective, this creates a particularly clear picture of the structure of Oph 163131. The annotations on this image describe different features of the disc.

[Image Description: A close-up of protoplanetary disc Oph 163131. Parts of the disc are annotated with labels: “Scattered dust”, at top and bottom, “Dark lane” across the centre, and “Inner disc”, “Outer disc” and “Gap” in the middle of the disc. A red glow around the disc is labelled “Extended diffuse emissions”. In the bottom right there is a scale bar, labelled “100 au”. It is about a quarter as long as the disc is wide.]