This is good; for one thing, it means I still have a job; more importantly, however, it means the sky is still full of wonder.<\/p>\n
Planets are one such wonder. The word \u2018planet\u2019 comes from the Greek \u2018plan\u0113t\u0113s\u2019, meaning \u2018wanderer\u2019. They were so named because our closest planetary siblings in the Solar System<\/a> appeared to wander across the night sky.<\/p>\n Alas, detecting our distant planetary cousins \u2013 the exoplanets that lie beyond the Solar System \u2013 takes far more effort than glancing skyward once the Sun<\/a> has set. It requires enormous telescopes, long observing campaigns and a lot of computing.<\/p>\n But believe me when I tell you, it\u2019s worth the effort. Exoplanet detection is booming. At the time of writing, astronomers have discovered<\/a> over 6,000 of them and we think that most stars have them.<\/p>\n But of course, in a field characterised by so many discoveries, occasionally truly extraordinary things turn up.<\/p>\n There have been planets that flirt with the line separating science and science fiction; planets that force us to revisit our theories of how they form; and planets that, in all fairness, feel like they shouldn\u2019t exist.<\/p>\n Planets like the 10 that follow\u2026<\/p>\n The planet too big for its star The discovery of TOI-6894 b<\/a> was only announced in June 2025 and it presents a genuine challenge to our understanding of planet formation.<\/p>\n Its star is a tiny red dwarf (roughly 20 per cent the size of the Sun), but TOI-6894 b is almost as big as Jupiter.<\/p>\n It\u2019s a problematic combination because our current best theory of planet formation says that very small stars can\u2019t have very big planets.<\/p>\n The planet-forming discs around nascent red dwarf stars simply don\u2019t have enough material. And yet, here is TOI-6984 b.<\/p>\n It\u2019s not the first problematic pairing of this kind to be found, but it is a record breaker: TOI-6894 b\u2019s star is the smallest known to host a giant planet.<\/p>\n Two Suns are better than one The \u2018(AB) b\u2019 part in this exoplanet\u2019s name tells us something crucial: it\u2019s circumbinary, meaning the planet orbits a double star system.<\/p>\n Roughly 50 per cent of stars in the Milky Way are in binaries of some sort, but 2M1510 (AB) b<\/a> orbits both stars at once. That\u2019s uncommon in itself, with only 16 circumbinary systems discovered to date. But there\u2019s more.<\/p>\n This isn\u2019t just any binary, it\u2019s a binary pair of failed stars known as brown dwarfs and that really is a rarity. Only one other pair like it has ever been found.<\/p>\n But wait, there\u2019s still more. The planet is on a polar orbit. This means it\u2019s orbiting at 90\u00b0 to the plane the brown dwarfs are orbiting in, looping over the top of them. It\u2019s the first of its kind ever detected.<\/p>\n Astronomers had an inkling that they might be a thing since we\u2019ve found protoplanetary discs in polar orbits, but for the first proper one to be found orbiting a pair of brown dwarfs is wild.<\/p>\n Read more:<\/p>\n Worlds built from the ashes of a dead star Exoplanets PSR B1257+12 b<\/a> and c were the first<\/a> to be discovered, back in January 1992, with d being found a couple of years later. This system really set the scene for the field, because it\u2019s ridiculous.<\/p>\n The planets orbit a stellar remnant called a pulsar \u2013 a rapidly rotating neutron star.<\/p>\n Neutron stars are very dense, have very strong magnetic fields and emit all sorts of electromagnetic radiation. But PSR B1257+12 b \u2013 the first exoplanet discovered \u2013 is still the lowest-mass planet ever detected.<\/p>\n Plus, there\u2019s the fact it was found at all, as planets orbiting pulsars are rare. Only 0.5 per cent of these long-dead stars are thought to host planets.<\/p>\n That\u2019s because the process of becoming a neutron star is such a violent end-of-life affair that there\u2019s almost no chance any existing bodies would\u2019ve made it through the tumultuous late stages of stellar evolution.<\/p>\n PSR B1257+12 b, c and d<\/a> are probably the result of a second round of planet formation. It\u2019s kind of nice that their star decided to have a second crack at parenthood in later life. It\u2019s never too late!<\/p>\n Sapphire rain over a boiling planet The first exoplanet discovered orbiting a regular star \u2013 51 Peg b<\/a> \u2013 is a kind of planet we don\u2019t have in the Solar System. It\u2019s a hot Jupiter.<\/p>\n These planets are so named because they\u2019re gas giants (like Jupiter), but much closer to their stars. They\u2019re silly enough, what with their super-inflated sizes, blisteringly hot temperatures and painfully short orbits, but WASP-121 b<\/a> is actually an ultra-hot Jupiter.<\/p>\n So the extreme conditions are just a touch more extreme. For one thing, WASP-121 b orbits its star in little more than 24 hours, but it doesn\u2019t actually have days because it\u2019s tidally locked \u2013 the same side always faces the host star, so it has a permanent nightside and dayside.<\/p>\n The sizeable temperature difference between the two hemispheres (1,500\u00b0C-ish\/about 2,730\u00b0F) causes wind speeds of over 16,000km\/h (10,000mph). It\u2019s hot enough on this planet to vaporise iron, aluminium and titanium.<\/p>\n Clouds containing these elements and their oxides can then be blown from the toasty dayside to the cooler nightside, causing rain of iron and gemstones, including sapphires.<\/p>\n There\u2019s an episode of Doctor Who where the Doctor visits a spooky planet called Midnight and goes on an ill-fated train ride to see some sapphire waterfalls.<\/p>\n Planets like WASP-121 b somehow make even the most bonkers sci-fi locations seem plausible.<\/p>\n The dancing planet where you might not get a birthday If you have one planet orbiting a star and there\u2019s absolutely nothing else in the vicinity, you can likely get a full understanding of the system, with enough observational data.<\/p>\n Things get trickier if you add one more planet in, as now you\u2019re into \u20183-body problem\u2019 territory \u2013 so-called because going from two to three celestial bodies in a system means it\u2019s no longer possible to get a full solution for the orbits via mathematical equations.<\/p>\n In most cases though, it\u2019s possible to get a decent approximation. Unless, of course, the two planets are in a special little dance called a \u2018mean motion resonance\u2019 (MMR).<\/p>\n An MMR (not the life-saving vaccine) means the planets\u2019 orbital periods are very close, in a ratio like 2:1 or 3:2, and it leads to frequent gravitational interactions between the bodies.<\/p>\n As is the case with TOI-4504 c<\/a>: it\u2019s locked in a resonance with its neighbour, completing two orbits for every one by its counterpart.<\/p>\n The result of these gravitational kicks? The length of a year isn\u2019t fixed. In fact, in this record-breaking case, a year can vary in duration by up to 2.4 per cent.<\/p>\n Can you imagine if that happened on Earth? A year could vary in length by eight days either way. People born in late December would never know if they were getting a birthday or not!<\/p>\n Read more:<\/p>\n Hotter than the surface of a star No list of extraordinary exoplanets would be complete without KELT-9 b<\/a>, the second ultra-hot Jupiter to make this list.<\/p>\n Its parent star is one of the hottest stars known to host a planet and, typically, we wouldn\u2019t expect to see planets orbiting anything at the upper end of the temperature scale.<\/p>\n Hot stars live fast and die young, burning through their nuclear fuel so quickly that planetary formation doesn\u2019t really stand a chance. But here\u2019s KELT-9 b, defying the odds.<\/p>\n The result is a planet so hot that, at over 3,700\u00b0C (6,700\u00b0F), it\u2019s actually hotter than most stars in the Milky Way. That\u2019s because roughly 75 per cent of our galaxy\u2019s stellar population are red dwarfs with typical temperatures under 3,200\u00b0C (5,800\u00b0F).<\/p>\n Hell on (another) Earth We\u2019ve known about this planet for more than two decades and it\u2019s been a conundrum the whole time. 55 Cancri e<\/a> is a super-Earth, meaning it\u2019s a bit larger than our home planet.<\/p>\n But if you\u2019re picturing a slightly enlarged version of here, complete with greenery and oceans, think again. It\u2019s a literal hellscape.<\/p>\n 55 Cancri e orbits in just 18 hours \u2013 this means it\u2019s very close to its star. So close, in fact, that the star\u2019s gravitational forces are continuously pulling the planet\u2019s surface apart. It\u2019s such a horrendously violent place, that it\u2019s thought to rain lava there.<\/p>\n In fact, this planet is so close to its star that the intensity of the radiation it receives is immense, so much so that astronomers thought there was almost no chance of it harbouring an atmosphere. Atmospheres don\u2019t generally get on with outrageously high temperatures; they tend to escape.<\/p>\n Imagine, then, astronomers\u2019 collective surprise when new observations from the James Webb Space Telescope<\/a> revealed that 55 Cancri e appears to have a tenuous atmosphere containing carbon dioxide and\/or monoxide.<\/p>\n \u201cHow?\u201d, we all asked. Constant replenishment, apparently: the gases evaporate from magma oceans on the surface, keeping that atmosphere nicely stocked.<\/p>\n Where in the worlds are all the moons? The PDS 70 system<\/a> has something that absolutely should exist, but has so far eluded us: evidence of exomoons<\/a>.<\/p>\n Moons are fairly ubiquitous in the Solar System, with Saturn and Jupiter boasting about 350 between them. Mars<\/a> has two of them and we\u2019ve got one of our own. Even demoted dwarf planet Pluto has a posse of them.<\/p>\n So, there\u2019s no reason to believe other planetary systems wouldn\u2019t also be riddled with them. But astronomers don\u2019t have the proof to back up that belief.<\/p>\n There have been plenty of \u2018potential exomoons<\/a>\u2019, and countless journal articles on how it might be possible to spot them, but there\u2019s not a single confirmed moon around any of the nearly 6,000 known exoplanets.<\/p>\n There\u2019s still hope, however, thanks to PDS 70; an infant star system, still in the throes of formation.<\/p>\n In the primordial muck of this particular corner in the vastness of space, you\u2019ll never guess what they\u2019ve spotted around planet PDS 70 c. An exomoon? Well, no\u2026 not quite. But astronomers have detected a moon-forming disc.<\/p>\n No smoke without fire, and no moon without moon-forming discs.<\/p>\n Read more:<\/p>\n Rogue planets<\/p>\n Rogue planets<\/a>, also known as free-floating planets (a less cool, but more informative name), are the planetary orphans of our galaxy.<\/p>\n So far around 100 of them have been discovered, but it\u2019s thought there could be as many as a trillion of them in the Milky Way. That would mean rogue planets outnumber stars by about 20 to 1.<\/p>\n It\u2019s a baffling thought because\u2026 well, where are they all coming from? There are two ways rogue planets form.<\/p>\n The more massive ones (a few times heavier than Jupiter, say) are thought to form in a similar way to stars \u2013 from an interstellar gas cloud collapsing under its own gravity<\/a>.<\/p>\n To get a new star out of this process, the resulting ball of gas and dust would need to be hot and dense enough for hydrogen fusion to kick in. When it fails, we\u2019re left with a brown dwarf or a free-floating gas planet.<\/p>\n The less massive rogues would\u2019ve formed in a cushy planetary system only to be kicked out by one of their siblings during a close encounter.<\/p>\n A planet boiling away to nothing
\nTOI-6894 b
\n![\"Illustration](\"https:\/\/www.newsbeep.com\/ie\/wp-content\/uploads\/2025\/12\/10-weirdest-planets-TOI6894b.jpg\")
Image credit: Getty Images<\/p>\n
\n2M1510 (AB) b
\n![\"Illustration](\"https:\/\/www.newsbeep.com\/ie\/wp-content\/uploads\/2025\/12\/10-weirdest-planets-2M1510ABb.jpg\")
Illustration of 2M1510 (AB) b, a planet orbiting two brown dwarf stars. The orbit of the planet is in orange and the two brown dwarfs in blue – Image credit: ESO\/L Calcada<\/p>\n
\nPSR B1257+12 b, c and d
\n![\"Illustration](\"https:\/\/www.newsbeep.com\/ie\/wp-content\/uploads\/2025\/12\/10-weirdest-planets-PSR-B1257-12c-superearth-NASA.jpg\")
Illustration of PSR B1257+ 12 c – Image credit: NASA<\/p>\n
\nWASP-121 b
\n![\"Illustration](\"https:\/\/www.newsbeep.com\/ie\/wp-content\/uploads\/2025\/12\/10-weirdest-planets-WASP-121-b.jpg\")
Illustration of exoplanet WASP-121 b, in front of a Sun – Image credit: NASA<\/p>\n
\nTOI-4504 c
\n![\"\"](\"https:\/\/www.newsbeep.com\/ie\/wp-content\/uploads\/2025\/12\/10-weirdest-planets-gasgiant-TOI-4504c-NASA.jpg\")
Illustration of gas giant exoplanet TOI-4504 c with its Sun in the background – Image credit: NASA<\/p>\n
\nKELT-9 b
\n![\"Illustration](\"https:\/\/www.newsbeep.com\/ie\/wp-content\/uploads\/2025\/12\/10-weirdest-planets-KELT-9-b.jpg\")
Illustration of the hottest known exoplanet, Kelt-9 b – Image credit: Getty Images<\/p>\n
\n55 Cancri e
\n![\"Illustration](\"https:\/\/www.newsbeep.com\/ie\/wp-content\/uploads\/2025\/12\/10-weirdest-planets-55-cnc-e-Nasa.jpg\")
Image credit: NASA<\/p>\n
\nPDS 70 c
\n![\"\"](\"https:\/\/www.newsbeep.com\/ie\/wp-content\/uploads\/2025\/12\/10-weirdest-planets-PDS-70-c.jpg\")
Image of the PDS 70 c system and its rings – Image credit: ALMA\/ESO\/NAOJ\/NRAO<\/p>\n
\nBD+054868A b<\/p>\n