04/04/2026
A pair of planet-forming disc
Science & Exploration
A pair of planet-forming discs
https://www.esa.int/ESA_Multimedia/Images/2026/04/A_pair_of_planet-forming_discs =aa3f2dd0-afca-4b3b-bd27-28f6f4160200
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This month’s NASA/ESA/CSA James Webb Space Telescope Picture of the Month offers us a two-for-one on brand new stars – with some potential planets thrown in as well!
This visual highlights Webb's views of the protoplanetary discs Tau 042021 (left) and Oph 163131 (right), otherwise known by the catalogue numbers 2MASS J04202144+2813491 and 2MASS J16313124-2426281, respectively. Tau 042021 is situated around 450 light-years from Earth in the constellation Ta**us, while Oph 163131 lies about 480 light-years away in Ophiuchus.
Protoplanetary discs like these appear around stars that have recently been born. When a clump of gas inside a larger molecular cloud collapses to form a star, unused gas and dust is left orbiting the star in a thick disc. Over time, this dust too collides and collapses, slowly forming planetesimals which can, in turn, develop into planets. The planetesimals which can’t make the jump to being a fully-fledged planet are left behind as asteroids and comets orbiting the star. Gas that isn’t consumed by this process is blown away by the new star’s radiation over the course of tens of millions of years, ending the protoplanetary disc. This is how our own Solar System formed in the distant past, creating the asteroids, comets, gas giants and terrestrial planets we know today. By observing other protoplanetary discs at a much earlier age, we can work out how this process worked for our own Solar System, and how the different kinds of planets we see across the galaxy could have formed.
The unique feature these two objects have in common is that, as we see them from our vantage point with Webb, they are oriented with the edge of the disc facing us. This means that the bright light from the young star in the centre is mostly blocked, and we see the fine dust that has risen out of the disc as a nebula above and below the disc, lit by reflected light from the star. Not only is this a beautiful sight, producing these images that resemble rainbow-coloured spinning tops in space, it’s essential for studying how these planet-forming discs are composed. The distribution of dust in the disc, both within it and above or below it, strongly affects where and how planets can form.
These images were created using data from Webb’s NIRCam and MIRI instruments, as part of Webb programme #2562 (PI F. Ménard, K. Stapelfeldt). With the broad infrared sensitivity of these two cameras, Webb can track dust grains of different sizes across the disc. The red, orange and green colours of the discs in these images indicate various sizes of dust grains as well as molecules such as hydrogen (H2), carbon monoxide (CO) and polycyclic aromatic hydrocarbons (PAHs).
Both images also feature data from the NASA/ESA Hubble Space Telescope, which shows visible light, mainly from the central star reflected off the fine, floating dust. The image of Oph 163131 also includes observations 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. This can create the right conditions for the grains to continue to grow and potentially form planets. Indeed, the ALMA data for Oph 163131 shows a gap in the inner disc, which may already be evidence of a planet forming and clearing out the dust around it.
[Image Description: Two images of protoplanetary discs side-by-side. The left image shows a dark horizontal band covering the star, with broad, colourful, conical outflows above and below it, and a narrow jet pointing directly up and down from the star. The right image shows the star within a yellow dusty disc, with scattered dust creating purple lobes above and below the disc. Each is on a black background with several galaxies or stars around it.]
