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HR 8799 is a very young star only 133 light-years from us. It’s likely about 40 million years old, though its age isn’t well restrained. In 2008, astronomers announced they had found three giant planets orbiting it — the planets were seen directly in imaging, appearing as little dots near the star. In 2010, a fourth planet was found as well.

These observations were made looking at infrared light, which makes it easier. For one thing, the star itself is fainter in those wavelengths (making fainter nearby planets easier to spot), but also the planets are still hot from their formation, so they glow in infrared, making them even brighter.

Over time, more images of the system were taken, leading to one of the coolest astronomical videos ever made: you can physically see the orbital motion of all four planets!

Mind you, the innermost planet moves the most rapidly, and it still takes 40 years to orbit the star once! Seeing this motion is amazing.

All four planets are significantly more massive than Jupiter, and our understanding of how planets form has trouble explaining this system. More observations always help.

But could there be a fifth planet? JWST had been previously used to observe HR 8799^* , but no fifth planet was seen (unfortunately, its capability to see a faint planet close to its star was hampered by internal optics more than had been expected before launch). However, a different team of astronomers took those publically archived observations and reprocessed them using a new method. This used models of the optical system in JWST to correct for issues that made interference from the bright host star less of a problem, allowing them to see fainter nearby objects [link to journal paper].

And it looks like they found evidence for a fifth planet! Nominally called planet f (the first four are b, c, d, and e) it would be the innermost of the system so far detected. Based on the positions of the other planets over time, and the measured position for the candidate fifth planet, the astronomers find its orbit is likely mildly elliptical about a billion kilometers out from the star, and has a mass of roughly 1.6 times Jupiter.

The planet is only about 0.0002 times as bright as the star, so it’s remarkable that they could see it at all, with it being so close in — it’s only about 0.15 arcseconds from the star as seen from Earth, which is the same as the apparent diameter of a dime seen from 14 kilometers away! So yeah, tiny.

Mind you, this isn’t confirmed yet. More observations with JWST could do it; the planet probably takes about 20 years to orbit the star, so images taken in the coming few years may show orbital motion.

If this pans out, astronomers will have fun using its existence and physical parameters to try to figure out how this system formed. Normally five giant planets like this would be unstable around a star, but their orbits appear to be in resonance with each other, with periods (their “years”) all being simple multiple factors of each other. In this case, it’s a 1:2:4:8 chain, meaning the outermost planets has a period 8 times longer than the innermost one, the second outermost takes 4 times as long, and the second innermost takes twice as long. This helps keep the system stable; if a planet starts to wander off its path a bit, the gravity of the other planets will pull it back into line. This isn’t a coincidence; over time planets can affect each other gravitationally and shift positions, and when they fall into a resonance like this they tend to stay there. We see this with three of Jupiter’s big moons, too!

I already love it when planets are directly imaged, and if this one is confirmed it’ll show JWST is back to its design spec for this type of observation. It also makes HR 8799 an even more interesting system, and it had already set a pretty high bar for that.

Tip o’ the dew cap to astronomer Sarah Kendrew on Bluesky for this news!

^* In fact, in 2025 JWST images showed direct evidence of carbon dioxide in exoplanet atmospheres, the first time this had ever been done (CO₂ had been detected before, but by using spectra). [link to journal paper]

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As I wrote last week in Issue 1085, I moderated a Carnegie-sponsored panel on the search for exoplanets and alien life, using a Star Trek theme. The panelists were three Carnegie scientists (Mike Wong, Maggie Thompson, and Nicole Wallack) doing cutting-edge research in the field, and it was a really fun night.

As you can see, we all wore Trek shirts (and we’re all nerds). I have a science officer shirt somewhere in the house but I don’t think I ever unpacked it after we moved to Virginia, so instead I’m wearing my “woke” Trek shirt (showing the Enterprise with a rainbow coming out the back). I love that shirt.

If you want to watch, there’s a video of the night now on YouTube.

One other thing. After the panel was over and the audience was mostly leaving, Mike Wong called me over to meet someone. I figured it was a scientist he worked with, but as I stuck out my hand Mike, from behind me, says, “This is Marc Okrand. He invented the Klingon language.”

I may have had a slight brain cloud for a moment upon hearing that. Holy moly. So I said what any dork in my position would have said: “Well then, qapla’!” He smiled and laughed, at which point my brain said, “You just made the guy who invented Klingonese laugh” and that’s another thing I will always remember about that evening.

The evening was part of the Carnegie Neighborhood Lecture Series, which has talks monthly or so in Washington, DC at the Earth and Planets Laboratory (I gave a lecture based on my book Under Alien Skies for this series in October 2024, too). If you live in or near DC, you should check them out! They’re free, and lots of fun. My thanks to my friend and lab director Mike Walter for inviting me to participate, to everyone who came, and especially everyone who made this night happen. Let’s keep boldly going.

You can email me at [email protected] (though replies can take a while), and all my social media outlets are gathered together at about.me. Also, if you don’t already, please subscribe to this newsletter! And feel free to tell a friend or nine, too. Thanks!