There are a lot of “blink and you missed it” things that are hard to see here on Earth. From the site of a particularly bright meteor during a star party to the acrobatics of a dolphin leaping out of the water on a ferry trip, if you are looking the wrong way and at the wrong moment, you miss everything. 

In looking at the sky, what it means for something to be short-lived is a little different, but the idea is the same. As we scan across the sky, we see lots of fully formed stars, which can live for billions of years. We see a fair number of things that last hundreds of millions of years, but the shorter-lived the phenomena, the harder it is to find an example in the sky. 

Catching planets in the process of forming is one of those short-lived phenomena we are struggling to catch. This is a double problem: we have to catch a short-lived phenomenon, and we have to catch it with just the right geometry that we can see the planet separately from the star. Of the 4,000 exoplanets of all ages so far found, only fifteen have been directly imaged by a telescope, as a dot beside a star. 

Now, with a combination of hard work and a bit of luck, a still-forming planet has been imaged orbiting an orange dwarf star, PDS 70, just 370 light-years from Earth. This is one of three planets in this system, and according to researcher lead researcher Yifan Zhou: This is the youngest bona fide planet Hubble has ever directly imaged. 

Zhou developed novel data processing techniques that allow the research team to carefully separate the light from the star and the planet, allowing the team to determine the planet is continuing to slowly grow as it circles at a Uranus-like distance from its star. Now, we just need to find a whole bunch more of these at different ages so we can measure growth rates at a variety of different ages. This work is published in The Astronomical Journal.

More Information

NASA press release

“Hubble Space Telescope UV and Hα Measurements of the Accretion Excess Emission from the Young Giant Planet PDS 70 b,” Yifan Zhou et al., 2021 April 29, The Astronomical Journal