The planet, now known as PDS 70b, is shown orbiting within a huge spinning "protoplanetary disc" of gas and dust, which proves it is continuing to accumulate matter, and so is not yet fully formed.
European Southern Observatory teams used a powerful planet-hunting instrument called SPHERE on the Very Large Telescope in the Atacama Desert, Chile, to produce the image. The analysis shows that PDS 70b is a giant gas planet with a mass a few times that of Jupiter.
The first clear image of a planet - the bright point to the right of centre - caught in the very act of formation around the dwarf star PDS 70. "The problem is that until now, most of these planet candidates could just have been features in the disk".
They also deduced that it has a cloudy atmosphere.
PDS 70 is a youngster itself, a 4.5-million-year-old T Tauri star surrounded by a circumstellar disc of gas and dust about 130 astronomical units across, or about 19 billion kilometres (12 billion miles). It takes the planet 120 years to orbit the star, which fits with astronomers' predictions that gas giants would need to form quite far from their stars. That blob is a coronagraph - a mask that researchers apply directly onto the star, lest its light blocks out everything else in the image. Two sets of researchers, published in two different papers in the journal Astronomy & Astrophysics on Monday, detailed how a planet is formed.
In the images, the newborn planet rips through the material surrounding the star.
"After more than a decade of enormous efforts to build this high-tech machine, now SPHERE enables us to reap the harvest with the discovery of baby planets!"
Capturing a planet's birth is exceptionally hard because it's often too far away to see on a telescope.
"Keppler's results give us a new window onto the complex and poorly-understood early stages of planetary evolution", said astronomer André Müller of the MPIA.
Despite the fact that it can take ages for a planet to fully form, actually capturing the process of planet formation has proven to be incredibly hard.
Astronomers observing circumstellar disks shredded with gaps, rings and spirals have long thought planet formation could be behind these structures.