Chapter 1: What types of strange planets exist in our galaxy?
Our galaxy is filled with strange planets. Now this should not surprise anyone. You just need to look at our own solar system to get a sense of the variety that exists. Rocky planets, gas giants, boiling surfaces, icy worlds.
Some planets with rings, others with moons. Some with storms the size of entire smaller planets.
but those pale in comparison to the marvels that exist once you start to look further afield. To date, NASA has confirmed the existence of more than 6,000 exoplanets in the Milky Way, and while many of them seem to follow the mould of what we would see in our solar system, others, to say the least, seem truly bizarre.
Chapter 2: What is the significance of exoplanets with multiple suns?
Worlds with multiple suns in their skies.
Worlds with rain made of molten iron. Worlds with rings the size of Venus' orbit. Worlds larger or hotter than stars.
But out of all this, what are the strangest planets we've discovered? What are the marvels our galaxy has in store for us?
And what further wonders may still be out there?
I'm Alex McColgan and you're watching Astrum. Join me today in this supercut as we take a look at the Milky Way's strangest exoplanets. When it comes to planets, many things can make them strange. For instance, sometimes strangeness is not found in the planet itself, but how it moves around its star.
While we are used to some large or small orbits in our solar system, how long or short can a year actually get? Let's start off close to home. Mercury has a pretty short year, only 88 Earth days, which is the shortest orbit that we know of in our solar system. And very interestingly, due to the way Mercury rotates, one Mercurian day is twice as long as its year.
Yes, there's exactly two years in its solar day. So, should anyone ever live on Mercury, you would have to switch around your way of thinking when it comes to describing a shorter reference of time. But it's kind of cheating to say a year on Mercury takes half a day, when it still takes 88 Earth days. So, let's keep to Earth timescales as the point of reference.
Outside of the solar system, most exoplanets that we know of have really short years, and that's because of the way we detect the majority of exoplanets. There are observatories that look closely at thousands of stars at the same time, looking to see if an orbiting exoplanet passes in front of its parent star, causing the star to dim ever so slightly from our perspective.
In order for us to confirm that the dip in brightness is caused by an exoplanet, we need to see a pattern of dips in regular intervals. So, if an exoplanet does transit a star, but it takes two Earth years before it transits again, then we would need to be constantly monitoring the star for many years before we can confirm that the dips in the star's brightness are caused by an exoplanet.
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Chapter 3: Which exoplanets have the shortest and longest years?
Binary star systems are generally simple enough – binary stars orbit around a barycenter or in other words, their centre of mass. If the masses of these two stars are similar, then nearly symmetrical elliptical orbits are often seen. Although, there can be occasions where they orbit in circles, in a similar fashion to Pluto and Charon.
In the case that one object is more massive than the other, then the more massive object's orbit doesn't take it as far out compared to the less massive object. Beyond binary systems, you can have 3, 4, 5, 6, 7 or more stars in the same system, and as you will see, there is a structure within these systems to keep them stable.
In the case of three stars, you'll have two stars orbiting each other in a binary configuration, with the third orbiting around a barycentre with the other two. This keeps the system stable, because if three stars had their orbits cross, one would certainly get ejected from the system at some point.
In a three star system, two of the stars are contained in their own enclosed little system, acting as one star in the grand scheme of the whole system itself. We group this binary configuration into a tier, with that tier acting together in its association with the single star.
In a way, once you have grouped the binary configuration in the system, this upper tier now acts like a two star system again, with the two stars and the one star orbiting each other. In the case of four stars, you'll either have two binary configurations orbiting around a barycenter,
or one binary system orbiting a barycentre with a third star, and all three of those stars orbiting around a barycentre with a fourth star. From here on is where the hierarchical system really comes in handy. With a chart like this, you can easily see how the system works. In the two binary configuration case, you have the two binaries orbiting the system's centre of mass.
In the single binary and two single stars configuration, you'll add another lower tier in the configuration. You have the binary here, which orbits this third star, and all three of these stars are orbiting together with the fourth star. If there are more stars in the system, say 5, you can have an array of configurations, with various binaries or single stars on a variety of tiers.
Yet with this chart, you can easily see where the mass lies. You can do the same for systems with 6, 7, or more stars, but anything above 7 is exceptionally rare and probably won't remain stable, although maybe there are examples somewhere in the universe where it exists. So, let's add planets into the mix. Could there be a planet out there with 7 suns in its sky? Well, yes.
Let's have a look at this hypothetical 7 star system again. By here, there are three stars in a configuration, two in a binary configuration, and a single star. We see that the single star has planets that specifically only orbit that star. They have one sun. Beyond that, there are planets that orbit both that star and its binary companions.
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Chapter 4: How do multi-star systems affect planet orbits?
Its exoplanet is one of the few exoplanets to be discovered using direct imaging. its host star is dim enough, the exoplanet is far enough away from the star, and big enough to be seen simply by using a powerful telescope. Unfortunately though, this means that while the mass of the exoplanet has been determined, we can't know of its radius for sure.
However, this is one of the most likely candidates that we know of. Also, because of the margins of error involved, it could well be that either or both objects are brown dwarfs, meaning we can't say if this is truly a star and planet system.
So, while we don't have definitive proof of a planet being bigger than its host star, we have found some promising candidates, and there's almost certainly cases out there that we haven't found yet. Some of the smallest stars out there have a radius of roughly 70,000km. Some of the biggest planets out there can be double or triple that. Which leads on to the final question I wanted to cover here.
What is the biggest exoplanet that we know of? Unfortunately, it is not clear cut. One possible answer is GQ Lupi b. It is another directly imaged exoplanet, which again means we don't have a good grasp on its physical characteristics. From the margins of area involved, it could be a brown dwarf. but it's probably the largest exoplanet that we know of.
Scientists have estimated its radius to be three times the size of Jupiter, but again, there are margins of error involved. Other contenders to this throne would be DH Tauri b and ROX 42BB. We've looked at a lot of exoplanets in the course of this video today. Some of the hottest, the coldest, planets with multiple stars, planets with none, the fastest orbits, and the longest.
But I want to finish with an exoplanet that would be visually stunning if its existence were to be confirmed. J1407b touted as the first exoplanet discovered with a ring system like Saturn. Sometimes, it is surprisingly tricky to spot ring systems around planets. It was only in 1977 that Uranus' rings were discovered.
Jupiter's rings were only spotted in 1979 when they were imaged by the passing Voyager probe. and Neptune's rings weren't seen until the early 1980s.
This is because, in the absence of nearby probes to photograph them, rings are usually discovered via either the transit method or stellar occultation, when they pass in front of a near or distant star, causing the light reaching us to momentarily dim. Usually, you have to be looking carefully. However, not so with J1407b.
When planets like Jupiter pass in front of its neighbouring star, they can sometimes block as little as 1% of the star's light. Their rings? Much less than that. When J1407b passed in front of its star, it blocked an incredible 95% of the star's light. Why was this? In 2012, researchers who noticed this phenomenon in the super wasp data came up with the answer. J1407b had rings. Massive ones.
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