The exoplanet WASP-69b has a comet-like tail – this unique feature helps scientists like me learn more about planetary evolution

163 light-years from Earth, a Jupiter-sized exoplanet named WASP-69b offers astrophysicists insight into the dynamic processes that shape planets across the galaxy. The star it orbits burns, stripping the planet of its atmosphere, and that escaped atmosphere is formed by the star right into a huge, comet-like tail not less than 350,000 miles long.

I’m an astrophysicist. My research team published an essay within the Astrophysical Journal describes how and why WASP-69b's tail formed and what its formation may reveal in regards to the other varieties of planets that astronomers are discovering outside our solar system.

A universe filled with exoplanets

When you have a look at the night sky, the celebrities you see are suns orbited by distant worlds called exoplanets. Over the past 30 years, astronomers have made discoveries over 5,600 exoplanets in our Milky Way.

It's tough to find a planet light years away. Planets pale compared to the celebrities they orbit, each in size and brightness. But despite these limitations, exoplanet researchers have discovered an astonishing diversity – all from small rocky worlds barely greater than our own moon to gas giants so colossal that they “”Super Jupiter.”

However, that’s commonest Exoplanets that astronomers are discovering are larger than Earth, smaller than Neptune and orbit their stars closer than Mercury does to our sun.

These extremely common planets are likely to fall into certainly one of two different groups: super-Earths and sub-Neptunes. Super-Earths have a radius as much as 50% larger than Earth's radius, while sub-Neptunes typically have a radius two to 4 times larger than Earth's radius.

Between these two radius ranges there’s a spot called “Radius gap“, where researchers rarely find planets. And Neptune-sized planets that orbit their stars in less than four days are extremely rare. Researchers call this gap the “hot Neptune desert.”

Some underlying astrophysical processes must prevent these planets from forming – or surviving.

Planet formation

When a star forms, a big disk of dust and gas forms around it. Planets can form on this disk. As young planets gain mass, they will accumulate significant gaseous atmospheres. However, because the star matures, it begins to emit large amounts of energy in the shape of ultraviolet and X-rays. This stellar radiation can burn away the atmospheres which have gathered on the planets Photoevaporation.

However, some planets resist this process. More massive planets have stronger gravity, which helps them retain their native atmosphere. Furthermore, planets which are further away The radiation from their star shouldn’t be as heavily polluted, so their atmosphere is less eroded.

It is feasible that a significant slice of super-Earths are literally the rocky cores of planets which have had their atmospheres completely removed, while sub-Neptunes were massive enough to retain their puffy atmospheres.

As for the Neptune Hot Desert, most Neptune-sized planets simply aren't massive enough to completely withstand the destructive power of their star if it orbits too close. In other words, a sub-Neptune that orbits its star in 4 days or less quickly loses all of its atmosphere. When observed, the atmosphere has already been lost and what stays is a bare rocky core – a super-Earth.

To put this theory to the test, research teams like mine have collected observational evidence.

WASP-69b: A novel laboratory

Enter WASP-69b, a novel laboratory dedicated to studying photoevaporation. The name “WASP-69b” comes from the best way it was discovered. It was the 69th star with a planet, b, present in the Wide angle seek for planets Opinion poll.

Although it’s 10% larger As far as Jupiter's radius goes, WASP-69b is definitely closer to the mass of the much lighter Saturn – it's not very dense and is simply about 30% the mass of Jupiter. In fact, there are about that on this planet same density as a bit of cork.

This low density results from this ultra-close 3.8 day orbit around his star. Due to its proximity, the planet receives an infinite amount of energy, which heats it up. When gas heats up, it expands. Once the gas expands enough, it begins to finally escape the planet's gravity.

When we observed this planet, my colleagues and I discovered that helium gas was rapidly escaping from WASP-69b – about 200,000 tons per second. This is similar to the mass the Earth loses every billion years.

Over the lifetime of the star, this planet will lose a complete equivalent of atmospheric mass almost 15 times the mass of the earth. That feels like quite a bit, but WASP-69b has about 90 times the mass of Earth, so even at this extreme speed it only ever loses a small fraction of the full amount of gas that makes it up.

WASP-69b's comet-like tail

Perhaps most striking is the invention of WASP-69b's prolonged helium tail, which my team was capable of trace not less than 350,000 miles (roughly 563,000 kilometers) behind the planet. Strong stellar winds, that are a continuing flow of charged particles emitted from stars, form tails like this. These particle winds ram into the escaping atmosphere, forming it into one Comet tail behind the planet.

Our study is definitely the primary to suggest that WASP-69b's tail was this huge. Previous observations of this technique suggested that the planet had done this only a humble cock or no tail in any respect.

This difference is probably going on account of two principal aspects. On the one hand, each research group used different instruments for his or her observations, which could lead on to different detection rates. Or there may very well be actual variability within the system.

A star like our Sun has a cycle of magnetic activity called the “solar cycle.” The sun lasts 11 years. During years of peak activity, the Sun has more solar flares, sunspots, and changes within the solar wind.

To make things much more complicated, each cycle is exclusive – No two solar cycles are the identical. Solar scientists are still trying to higher understand and predict developments the activity of our sun. Other stars have their very own magnetic cycles, but scientists simply don't yet have enough data to grasp them.

So the variability observed for WASP-69b may very well be on account of the indisputable fact that the host star behaves in another way every time it’s observed. Astronomers might want to proceed observing this planet in the long run to get a greater idea of ​​what exactly is occurring.

Our direct have a look at WASP-69b's mass loss tells exoplanet researchers like me more about how planetary evolution works. It gives us real-time evidence of atmospheric escape and supports the speculation that hot Neptunes and radius-gap planets are hard to search out because they simply aren't massive enough to retain their atmosphere. And once they lose it, all that is still to be observed is a rocky core of the super-Earth.

The WASP-69b study highlights the fragile balance between a planet's composition and its stellar environment, shaping the varied planetary landscape we observe today. As astronomers proceed to explore these distant worlds, each discovery brings us closer to understanding the complex fabric of our universe.