Finding Real-Life Tatooines: 27 New Two-Sun Planets Discovered!

When you gaze upon the sunset, do you ever think about how two suns would look if they were both setting beneath the horizon?

If you're into sci-fi books and movies, then you don't need a lot of help imagining it. Just think of Luke Skywalker looking at Tatooine’s two sunsets, and you can picture what a planet with two suns feels like. This image has become the quintessential symbol of an alien world that exists far away from here, and the concept of an actual planet orbiting two stars is a concept that has been stuck in the realm of science fiction for so long, it feels like it was only ever going to exist in a galaxy far far away.

Now, for the first time ever, this piece of fantasy became reality!

In the most exciting announcement you could ask for during May the 4th, a group of brilliant scientists from the University of New South Wales have discovered 27 planets that could potentially be circumbinary.

That's right! 27 New worlds with twin sunsets are NOT simply a film effect; they are real places where twin sunsets occur every day!

Join me in uncovering the details behind this amazing discovery, why it is so challenging to locate these new planets, and how a completely new technique for locating planets is going to revolutionize our view of the universe.

How Rare is a World with Two Stars?

Before we can jump into the new discovery that we’ve found out about making things even more difficult, let's review what is already on record. Astronomers have confirmed over 6,000 exoplanets (planets outside our planet's solar system) to date.

Can you guess how many of these 6,000 exoplanets are circumbinary?

Only 18. A mere 18 circumbinary planets out of 6,000 discovered so far. This statistic appears to be a very, very small percentage of all planets discovered to date and implies that circumbinaries may be among the rarest of planets discovered, however that is not the case. As far as the universe is concerned, astronomers do not believe circumbinary planetary systems are among the rarest in the cosmos. Binary star systems - two stars orbiting each other about a shared centre of gravity — are in fact very common. Many, if not most, of the stars you see in the night sky are, in fact, two stars in orbit around one another. Therefore, circumstellar binary systems should also be fairly common.

So why do we see so few circumbinaries? Because we have not previously "looked" at them.

The problem with our best way to find the planets that orbit other stars

The "transit method" has been the most effective way to find exoplanets for many years.

Think about being in a dark room looking at a very bright light bulb. Now picture a tiny moth flying directly in front of that light bulb. For just a tiny fraction of a second, the light bulb would become just the tiniest bit dimmer than it was before because the moth blocked the tiniest bit of light from reaching you.

This is exactly how the transit method works. We use very large space telescopes, look at a very distant star for a very long time, and then watch the light from that star. If we see a drop in the light we are looking at from the star and that drop occurs on a regular, timed basis, then we know that there is an object passing in front of the star blocking some light from it (a planet).

The transit method is, without question, an extraordinary way of finding exoplanets. It is how over 90% of all of the exoplanets that have been confirmed (almost 6,000 total) were discovered; however, like most things in life, it has a huge flaw - it is totally dependent on geometry. In order for a planet to pass in front of a star and block some of the light from the star, the planet has to go directly between the telescope and the star. If the planet's orbit is tilted even a small amount compared to the line of sight of the telescope, then the planet will never be visible for a transit measurement.

Let’s take for example, using the transit method of locating a possible circumbinary planet. If you consider that the two stars revolve around each other and the planet revolves around the two stars, then the gravitational pull between these bodies becomes very complicated, the paths of these bodies wobble as they move about the other bodies, and therefore the chances of the three bodies (one of which is the observer’s vantage point (the earth)) lining-up perfectly to cause a transit, is extremely small.

Thus, if we only relied on the transit method, the majority of circumbinary planets would be undetectable for all time. Therefore, we needed a different technique.

The Discovery from the UNSW team: Apsidal Precession!

And here’s where the divide became apparent. Instead of searching for shadows as with Kepler’s method the UNSW team was introduced to a whole new way to look for a planet. They turned towards "Apsidal Precession" to find a gravitational tug-of-war.

Apsidal Precession may sound complicated; however, it is actually quite simple once you break down the idea.

The UNSW Scientists looked at star systems that are in a binary system and that eclipse one another from our perspective. While the two stars are dancing around one another, one of the stars passes in front of the other star blocking some of the light from reaching Earth. Since we understand the physics of the two stars dancing around one another so well, astronomers can tell you when the next eclipse of the two stars will take place. Using this method, they have a “perfect cosmic clock.”

Now if the “perfect cosmic clock” begins to run slow or fast what does it actually mean?

Over long periods of time if the time between star eclipses changes and it can not be accounted for by either general relativity or the two stars' influence on one another, this opens up the possibility that there is an additional gravitational influence present with the stars.

Somewhere in space, there is a "third body" affecting the perfect motion of the stars with its gravitational pull.

That third body is a circumbinary planet, which affects the stars indirectly by its gravitational attraction.

This not only takes away the need for perfect alignment between our view of the binary stars and the circumbinary planet, but also means that the circumbinary planet does not even have to transit the binary stars from our perspective. The circumstellar planet has enough gravitational influence that its apsidal precession will detect it, regardless of how it is aligned with the stars. While this method has previously been utilized for analyzing binary stars, it has never before been used to discover hidden planets on such a large scale.

Examining TESS Data

Obtaining large numbers of highly precise astronomical data is critical in conducting astronomical research. You can’t just look at the night sky from your own home with a telescope; you need a powerful telescope capable of observing multi-star systems and measuring their brightness accurately.

NASA’s Transiting Exoplanet Survey Satellite (TESS) was selected to collect the data required to conduct the research required in this study. TESS was launched by NASA into Earth’s orbit in 2018, and is considered to be one of the best exoplanet detector systems ever built, as its mission is to collect bright-star photometric data for scientists around the world.

The UNSW team processed and analyzed the vast quantities of TESS data, and in addition, they utilized their new methodology for identifying àpsidal precession in exoplanet systems on a trial basis. The results from their analysis exceeded their expectations and produced many more circumstellar planetary systems than were previously known. They discovered a total of 27 new potentially habitable exoplanets in one iteration of data processing and analysis. Prior to this research project, the worldwide astronomy community had confirmed the existence of only 18 of such planetary systems, making this research project a significant milestone in the hunt for “real-life” Tatooines.