Photo by: NASA


A Jupiter-Sized Exoplanet Orbiting Two Stars

One of my favorite things about exoplanet systems is just how weird they can get. It seems that every few months we are treated to another surprise. This time around, NASA's TESS observatory delivered a planet almost three times more massive than Jupiter orbiting around not one, but two stars. As an added bonus: that planet orbits its twin suns closer than the Earth does around the sun. Who wants to take a trip?

July 26, 2021

Finding exoplanets -planets orbiting other stars - is pretty much routine nowadays. All you have to do is stare at stars long enough. If you're lucky, an exoplanet will have just the right orbit so that it crosses the face of its parent star as viewed from the Earth. We don't get to see the planet itself, but we do see the subtle dip in brightness from the exoplanet blocking some of its parent star’s light. With this technique, called the transit method, astronomers have discovered thousands upon thousands of worlds outside of our solar system.

And in the case of TIC 172900988b (I’m sorry it’s not a very romantic name, but that’s all we’ve got), astronomers saw this transit happen twice in the same observation. Staring at a star 824 light-years away in the direction of the constellation Cancer with NASA’s Transiting Exoplanet Survey Satellite (TESS), astronomers noticed the characteristic dip in brightness from an exoplanet crossing our line of sight. And then 5 days later, they saw the exact same thing happen again.

Illustration of NASA's Transiting Exoplanet Survey Satellite: TESS

Photo by: NASA's Goddard Space Flight Center

NASA's Goddard Space Flight Center

Illustration of NASA's Transiting Exoplanet Survey Satellite: TESS

The astronomers concluded that they found a case of a planet orbiting a binary star system, and the real treat was that this was the most massive known planet to do that.

And what a wonderful system it is. In the center of the system there are two stars orbiting each other every 19.7 days. And around them sits a giant planet, 2.9 times the mass of Jupiter. That giant planet has an orbit around the binary pair lasting around a couple hundred days. Placed in our own solar system for comparison, that would place that giant world just within the orbit of Venus.

The stars in the system make an eclipsing binary, which occurs when the stellar companions circle each other in our plane of view.

Photo by: NASA/Goddard Space Flight Center

NASA/Goddard Space Flight Center

The stars in the system make an eclipsing binary, which occurs when the stellar companions circle each other in our plane of view.

Imagine coming up on this world for yourself. You see a planet like Jupiter orbiting where Venus ought to be. And instead of a single star you have two stars rapidly rotating around each other.

It's better than anything any science fiction writer could possibly come up with, and the more we observe exoplanets the more we find out just how weird and wonderful our universe is.

Dive Deeper into the Cosmos

Journey Through the Cosmos in an All-New Season of How the Universe Works

The new season premieres March 24 on Science Channel and streams on discovery+.

Paul M. Sutter

Paul M. Sutter is an astrophysicist at Stony Brook University and the Flatiron Institute, host of Ask a Spaceman and Space Radio, and author of How to Die in Space.

Next Up

Six Planets are Retrograde, What Does that Mean for You?

Spoiler alert: It's an optical illusion.

Jupiter Makes Its Closest Approach to Earth in Nearly 60 Years

The last time Jupiter appeared this large and bright in the sky was in October 1963.

How Exoplanets Became the Next Big Thing in Astronomy

To date, we know of over 5,000 planets outside the solar system. And astronomers suspect that there may be *checks notes* around a trillion more in our galaxy alone. The search for exoplanets is one of the hottest topics in astronomy, with expensive telescopes and giant collaborations all searching for the holy grail of the 21st century: an Earth 2.0, a habitable world like our own.

What We’ve Already Learned From James Webb? (Hint: it’s a lot)

That was worth the wait. Just a quick handful of months since its historic launch on Christmas Day, the James Webb Space Telescope has flown to its observing position, unfolded its delicate instruments and ultra-sized mirror, and run through a suite of checks and alignments and calibrations. The team at NASA behind the telescopes released their first batch of images from the science runs, and besides being gorgeous, they're powerful.

This Year, James Webb will Take a Close Look at a Lava World

The James Webb Space Telescope is gearing up to be an exoplanet extraordinaire. Among many other missions and targets, astronomers plan to use the observatory, now in its final stages of preparations to study…well, a world where it might rain lava.

Why Astronomers Care About Super-Old Galaxies?

A long time ago, our universe was dark.It was just 380,000 years after the big bang. Up until that age, our entire observable cosmos was less than a millionth of its present size. All the material in the universe was compressed into that tiny volume, forcing it to heat up and become a plasma. But as the universe expanded and cooled, eventually the plasma changed into a neutral gas as the first atoms formed.

What Comes After the Moon and Mars?

Space hotels may be in our future.

Got You! Astronomers Find an Especially Sneaky Black Hole

Black holes are tricky creatures. Since ancient times the practice of astronomy has been to point our eyes and instruments at all the glowing things in the skies above us. But black holes are defined by the fact that nothing, not even light, can escape their gravitational clutches. So how you do see something that is completely, totally black?

Groundbreaking New Images of Jupiter Exceed NASA's Expectations

NASA’s James Webb Space Telescope captured new images of Jupiter revealing never-before-seen details of the planet.

Want to Name a Planet? Now’s Your Chance

Read on to learn about this rare opportunity to name a distant world observed by the James Webb Telescope.

Related To: