A Tour of the J1407b Analogues

J1407b is arguably one of the most famous objects outside the solar system we know of, and that's due to a lot of popular misconceptions about it, and because it is genuinely a really weird and abnormal place. Obviously it's no stranger to being covered on this channel, but to be fair I cover a lot of famous exoplanets multiple times, and videos about this one just happen to do well. For those who aren't up to speed, J1407b is an unconfirmed object, likely a subbrown dwarf surrounded by a large debris disk that transited the star V1400 Centauri in 2007. This caused the star to dim by 95%, suggesting that whatever object passed in front of it was both very large and surrounded by an enormous disk of material. The most likely explanation for this dimming is that J1407b is essentially a very small scale star system, a small brown dwarf surrounded by a disk where new planets are actively forming. Importantly, this is meaningfully different from a planet with a large ring system, and it would be inaccurate to call J1407b a Super Saturn. Its disk is much more comparable to the sun's asteroid belt rather than the rings of Saturn. The other notable thing about J1407b is that it's likely a rogue object not orbiting any star. This is because it only ever transited V1400 Centauri once, and based on its speed it should have transited multiple times by now, strongly suggesting it doesn't orbit the star it passed in front of, and instead experienced an extremely close flyby of it. This also makes J1407b extremely difficult to study, as we currently don't know where it is, and attempts to directly image it moving away from V1400 Centauri have so far failed. This also makes it technically not actually confirmed to exist, though this rogue subbrown dwarf hypothesis is so far the most likely one. Point is, while J1407b is not a planet with rings as it's been claimed to be online, it is regardless an extremely interesting object that still has a lot of mystery surrounding it. I'll explain this in more detail soon. But this video will be about more than just this object. J1407b isn't the only object of its type we know of. It was only the first to be discovered. Since the first transit of J1407b in 2007, numerous additional objects with similar characteristics to the original J1407b have been suspected to exist, though with varying degrees of confidence. Some are confirmed, others are candidates, and some, like J1407b, have only been seen once and cannot be detected again. Again, while these aren't super-saturns, they do represent a class of world we currently have very little knowledge of, a middle ground between gas giants and their moon systems, and stars and their planetary systems. J1407b and objects like it mostly form like stars do, yet don't gain enough mass and remain planetary in scale. Despite this, they're still surrounded by protoplanetary disks of their own, the same type young star systems have. And like planets, some orbit stars while some are rogue, and each J1407b analog is going to be unique from the rest, despite having broadly similar characteristics. Studying these types of objects can give us good insights into both how planetary systems and moon systems form at once, and this is the only class of object we can do that with. So this video will be a tour into every object we currently know of similar to J1407b, and everything we know about them. We'll start with OTS-44, but for a quick comparison, let's go over the general characteristics of J1407b itself. Almost nothing is known about J1407b, but we do know a fair amount about its surrounding debris disk. J1407b's disk is about 0.6 AU in radius, which if it replaced the sun, would put the maximum extent of its disk between Mercury and Venus. For comparison, when the sun was forming, its disk is estimated to have been between 100 and 200 AU wide. It's also been estimated that the total mass of J1407b's disk is a bit larger than the mass of Earth, and is separated by many gaps that could indicate the presence of planets forming around it. For example, a gap 0.4 AU away from the object could have been carved by a young planet around the size of Venus or smaller, and a gap at 0.35 AU may suggest the existence of a second, smaller planet. This is also another reason why calling this disk a ring system would be inaccurate. Planetary rings like Saturn's are formed by the destruction of previous objects and don't typically form into new moons, though there are exceptions to that, while J1407b's disk is primordial, meaning it formed when J1407b did, and will eventually coalesce into a system of planets, and is already in the process of doing so. Saturn's rings, by comparison, are falling into the planet itself, formed after Saturn did, and the small moons that have formed out of ring material so far are really just dustballs that physically can't get much larger than a few kilometers wide. J1407b itself has an unknown mass, though based on the failure to directly image it, it must be less than 6 Jupiter masses. This object passed within a few tens of AU of the sun-like star V1400 Centauri in 2007, which was an extremely close passage and suggested it was in orbit around the star, but later observations showed this was unlikely. If J1407b is a rogue object, it should be far enough away from V1400 Cen today to be directly imaged. This has been attempted in 2017, but the object was not able to be detected, also indicating its disk is thin and made of small dust particles less than a millimeter in width. Importantly, this non-detection doesn't necessarily mean J1407b doesn't exist, which is a mistake I made in a previous video I've since deleted, it simply constrains possibilities for the structure of its disk. So to summarize, J1407b is likely a rogue sub-brown dwarf less than 6 times the mass of Jupiter, with a small debris disk 1.2 AU wide, with at least two unconfirmed candidate planets around it, that is composed of small particles, that experience an extremely close passage of the star V1400 Centauri. This flyby also likely disrupted the V1400 Cen system and maybe any planets that were inside it. A rogue planet entering your system is usually pretty bad for stability, but that's a subject for another video. Attempts are ongoing to directly image J1407b, but have so far come up empty. So with that out of the way, let's talk about the most well-known object with properties similar to J1407b, OTS-44. OTS-44 is a rogue brown dwarf in the Chameleon Cloud Complex, one of the closest star-forming regions to Earth. Specifically, it's in the Chameleon 1 Cloud, which has about 200 to 300 stars forming inside it. OTS-44 has some around 6 to 17 Jupiter masses, making it likely larger than J1407b. It's also extremely young, just 1 to 6 million years old. For comparison, J1407b is estimated to be around 20 million years old, though this estimate may be inaccurate as it's based on the age of V1400 Centauri, which we now know J1407b is likely not associated with. Because OTS-44 is so young, it's extremely hot, with temperatures comparable to red dwarf stars despite being planetary mass. Based on the way stars are classified, this would actually make OTS-44 an M-type brown dwarf, which is interesting as the M-type classification is usually reserved for red dwarfs and red giants. Interestingly, OTS-44 was actually discovered 2 years before J1407b in 2005, though J1407b is far more famous due to it once being thought to orbit a star. It has always been known that OTS-44 is rogue, and its debris disk has always been called a debris disk rather than a ring system. In addition to being more massive than J1407b, OTS-44's debris disk is also about 30 times more massive, with about 30 Earth masses of material being present in it, mostly in the form of gas. The disk is also much wider, over 100 AU in length. The disk decreases intensity but flares out vertically the further it gets from the object, as seen in this diagram. To the best of my knowledge, we don't currently know of any large scale gaps in OTS-44's disk where planets may be present, but this is likely due to the object's significantly younger age. Any planets that may have already formed may not have had enough time to carve out their gaps. In short, OTS-44 is larger, younger, and has a more massive and wider disk than J1407b, with the potential for larger, more interesting planets around it. However, it's pretty much remained solitary its entire life, and as far as we currently know, hasn't been close to any other objects. So while it may be significantly larger than J1407b, J1407b has so far had a more interesting history. But one of the things these two objects have in common is that they're both rogue and don't orbit a star. However, most of the other J1407b analogs we know of are actually bound to stars. I should mention here that OTS-44 is basically the only object of this type we know with an absolute fact definitely exists. Not coincidentally, it's also the only one that was found with direct imaging rather than transit. J1407b almost certainly does, but the fact we haven't found it again yet means we can't really say for certain. But after that, confidence in the existence of these objects goes down a bit, and many will be unconfirmed. This is mainly because many of these objects have such long orbits that they've only ever transited their star once in our entire history of observations, which isn't enough to fully confirm it. And a great example of this is Assassin-21-JSB. Assassin-21-JS is another young star circled by an object much more similar to J1407b than OTS-44. But, again, it's disk is almost twice as wide as J1407b's, with a radius of about 1.05 AU instead of 0.6. This object doesn't yet have an official designation, but for the purposes of this video I'll be calling it Assassin-21-JSB. This is because this is also the first J1407b analog in this video confirmed to be orbiting a star, and it's not a rogue object. This goes for every object we'll be covering in the rest of this video, none of which have official designations yet. That being said, Assassin-21-JSB has an extremely long orbit, and it's estimated to be about 13,000 AU away from its star. For comparison, the exoplanet with the widest confirmed separation from its star, Coconuts-2b, is about 7,500 AU away from its parent. The sun's Oort cloud begins at about 2,000 AU. So Assassin-21-JSB does orbit a star, but since it's a full 0.2 light years away from it, for all intents and purposes it acts pretty much like a rogue object. This orbit is estimated to take roughly 610,000 years to complete, though Assassin-21-JSB is still a transiting object, and is currently passing in front of its star from our perspective. However, because this orbit is so long, as well as the size of its disk, Assassin-21-JSB's transit has already lasted several years, and is expected to complete in May 2027. For reference, the transit began in 2021. But after this transit is over, we will literally never see this object again for another 610,000 years, so we only have a few months left to study it before it's gone forever. That being said, we already know a fair amount about this J1407b analog. Assassin-21-JSB's disk is likely split into two concentric rings separated by a gap, though what material it's made of and the structure beyond that, as well as the mass of the disk, are all unknown. Similarly, the object itself has an unknown mass, but the paper discovering it, linked in the description, suggests it is substellar, meaning it could be a planet or a brown dwarf. If Assassin-21-JSB is planetary mass, it would dethrone Coconuts-2b as the planet with the longest orbit ever confirmed, though there's a few problems with that. This large orbital separation suggests this object probably would have formed outside of its star's protoplanetary disk, which would suggest it may have formed similar to the way stars do, which would classify it as a subbrown dwarf, even if it's planetary mass. But to be fair, it's possible the same thing also applies to Coconuts-2b, and these definitions are murky anyways. But since that's all we currently know about this object, let's move on. Gaia-21-BCVB is similar to Assassin-21-JSB as well, and is the next J1407b analog we'll talk about. This is the first object on this list that has a disk smaller than J1407b's, with a It orbits a star as well, but its orbit is much shorter than the previous entry, lasting somewhere less than 3,375 years, and it's somewhere less than 225 AU away from the star. Gaia-21-BCVB is basically what we originally suspected J1407 to be when it was thought to be orbiting V1-400-Cen, though with a significantly larger orbit. But again, because this object has only ever been seen once, we can say very little about it, and as far as I can tell its transit is over, so our chance to study it further has already passed. The transit lasted about 800 days and began in 2019, and the star has since returned to its normal brightness. As far as I can tell, we don't know of any gaps in Gaia-21-BCVB's disk, though the object is suspected to be about 10 million years old based on the age of the star. Like Assassin-21-JSB, Gaia-21-BCVB's mass is unknown, but it's suspected to either be planetary mass, a brown dwarf, or potentially a low-mass star. A comparison of this object's disk, as well as J1407-B and Assassin-21-JSB's, can be seen here. Also visible in this is VVVWIT-08, which we'll talk about next. I should mention here that it's currently unknown if VVVWIT-08-B is a substellar object or a star. However, unlike the previous entries, this object being a star is more likely for a few reasons. For one, its star is not young, unlike all previous objects in this video, and is also a red giant, which tend to be more massive. Red giants also more often host stellar companions rather than brown dwarfs. That being said, it's currently completely unknown what type of object VVVWIT-08-B is. It could be a planet, brown dwarf, or star, all we know is that it possesses a disk smaller than J1407-B's with a radius of about 0.25 AU, half the size of Gaia-21-BCV-B's. Like Gaia-21-BCV-B, the transit of VVVWIT-08-B lasted a few hundred days and is now over, though unlike Gaia, there's only a lower limit on this object's orbital period instead of an upper one. VVVWIT-08-B's orbit must be longer than 11 years for the observations to make sense, and its orbital separation is currently unknown. Unfortunately, it's unlikely we'll know any more about this object any time soon, leaving it a mystery. We do, however, know it has a disk, which is odd given its supposedly older age. It's also worth noting the reason we don't know this object's mass is because we don't know the mass of the red giant it orbits, making radial velocity observations as well as pinning down its true orbit difficult. But this does open the possibility for something extremely interesting. It's unlikely for a young object to exist in this system because the VVVWIT-08 system isn't young. There aren't many ways for an older object like this one to produce a disk, and yet it has one. However, there is one method. Stars that have already gone supernova, or have shed their outer layers and become white dwarfs, can briefly regain disks of material, potentially like the one this one has. So while there's no direct evidence of this, it may be a possibility that VVVWIT-08-B is a white dwarf, neutron star, or black hole with an accretion disk. This would definitely make it not a J1407B analog, and instead a stellar remnant, but it would remain an incredibly interesting object nonetheless, so I thought it was worth mentioning in this video, even though it's probably unlikely to be planetary mass, and thus unlikely to actually be a J1407B analog. An object we do know a bit more about, however, is Assassin-24FWB. Or rather, we know more about its star, which can tell us more about the disk's object orbiting it. Assassin-24FW, the star, is estimated to be about 40% more massive than the sun, almost twice its radius, and about 2.75 billion years old, making it a pretty massive star. Because we know its mass, we can say with a higher amount of confidence the mass of Assassin-24FW would be the companion orbiting it. This object has one of the smallest disks covered in this video so far, with a radius of just 0.17 AU, over three times smaller than J1407B's, but still pretty large. This object has a minimum mass of about 3.4 Jupiter masses, putting it well within planetary range, but this is only a minimum and was calculated based on the size of the disk itself. 3.4 Jupiter masses is the smallest possible mass this object could be to keep all this material in a stable orbit around it. However, the disk is also not very massive, with the paper linked in the description giving an estimated mass just 1% that of the moon, or about the total mass of the dwarf planet Ceres. You may have also noticed that this star is 2.75 billion years old, and thus Assassin-24FWB's disk is unlikely to be primordial, as the object is too old. However, unlike VVVWIT-08B, which had this same problem, we can be somewhat confident that this object is planetary mass, or at least a brown dwarf. So something must have happened for it to form this disk. The same paper suggests a planetary collision could be the potential cause, which while that's currently speculation without that much evidence, would make Assassin-24FWB's disk meaningfully different from the other disks so far, as it would not have formed with the object itself. If this object is a planet, it's a possibility moons may be forming here as well, analogous to our own moon's formation after the Theia impact, which is pretty cool. The transit of this disk lasted about 9 months, and at the time of the transit is estimated to have been about 14 AU away from the star, one of the closest distances seen so far and comparable to J1407B's original transit. It is worth noting, however, that the orbital eccentricity of Assassin-24FWB is currently unknown, and that will affect the estimates for its mass. A more eccentric orbit would require a higher mass to keep the disk stable, potentially up to 25% the mass of the sun, which would make it a star, though an upper limit of about 19 Jupiter masses is also possible, making it likely to be planetary mass or a brown dwarf. Similarly, it also may be much smaller. If the disk fills the entire hill sphere of this object instead of just part of it, masses as small as just half that of Jupiter are also possible. It's also worth noting that this object's star possesses a disk of its own, similar to an asteroid belt, as seen in this diagram. There are many other objects with transiting disks that are all pretty interesting. If you read the papers in the description, the name Epsilon Aurige will pop up with it, a large star surrounded by a smaller star with a disk of its own. However, these are, as far as I can tell, so far the only objects that have the chance of being a brown dwarf or planetary mass, and all the rest are almost certainly stars, and so we'll be skipping them for this video. But as you've hopefully seen, the population of J1407B analogs we know of is extremely diverse, and every object has its own unique conditions. To summarize, we have J1407B, a small sub-brown dwarf with several gaps in its disk indicative of foreign planets that, despite being a rogue object, suffered and survived an extremely close passage with the star, OTS-44, a solitary brown dwarf with a flared disk over a hundred AU wide, wider than the entire solar system, Assassin-21-JSB, a massive object with a large disk orbiting in its system's Oort cloud, Gaia-21-BCVB, an object of an unknown mass on a 3,000 year orbit around its star, VVVWITOAB, a mysterious object that could be a star or even a white dwarf, neutron star, or black hole, though that's unconfirmed, and Assassin-24FWB, an older object, potentially planetary mass, that may have gained its unique disk through a planetary collision. Each object is completely different from every other, and despite only observing most of these worlds only once, there's still a ton we can say and even more we can theorize about. But, unfortunately, speculation is likely all we'll be able to do for a while, as except for OTS-44, these objects will never be observed again. Assassin-21-JSB will come back around in another 600,000 years, Gaia-21-BCVB in 3,000. J1407b is currently lost, and attempts to locate it again are still ongoing. The nature of these objects is what makes them simultaneously so interesting and so hard to study. Objects closer to their stars are easier to see multiple times, but being closer to a star would preclude the formation of these interesting disks. Put the object too close to a star, and the star's gravity will rip away the disks. They have to be on far harder-to-observe orbits to even exist, which is unfortunate for us. Really, the only way to study objects like this right now is to find more, as you really only get one shot at it before it's gone forever. Many more objects like this are expected to be found in the Gaia Telescope's fourth data release, dropping later this year. It's also worth wondering how many worlds like this we're currently missing. There could be hundreds more of these things we can't see yet because they either don't transit or are currently behind their stars and won't be visible for thousands of years. These objects are likely to be pretty rare. With only a handful of exceptions, these objects must be young to even have disks like these in the first place, and there are a lot more old brown dwarfs than young ones. Who knows, maybe older brown dwarfs we currently know of, like for example, WISE-0855-0714, just 7 light-years away from us and the closest rogue, solitary brown dwarf to us, used to have disks like these that have since coalesced in a fully-formed planetary system. Clearly, we currently have more questions than answers about these types of objects, and they'll likely remain questions for a very long time. Until then, J1407b and the strange group of objects similar to it, while not planets with rings as it's often been claimed, are incredibly interesting and a unique perspective into how middle-ground objects between planets and stars form. Hopefully we can find out more about these elusive, mysterious, and incredibly interesting class of worlds soon. Thank you for watching. If you enjoyed, check out my other videos about exoplanets and space exploration.