An undergraduate student currently studying a Bachelor of Science in Geology. Graduated in 2018 with an unendorsed Graduate Diploma, focusing mainly on creative writing, as well as with a Bachelor of Arts in History (with an Education minor) in 2010. There is definitely intent to go on to a postgraduate degree immediately after finishing the BSc undergrad.
Pollux may be a dying red giant star past its prime, but it’s not going through life all alone, for it has a planet to keep it company through ups and downs. Together with Castor, it resides in the constellation Gemini; Pollux is clearly the red-headed twin of the pair. And, not only does Pollux have a planet to keep it company, it also has a little puppy nearby, in the form of Canis Minor with its bright star, Procyon.
Pollux, along with its giant planetary friend around two to three times Jupiter’s size, resides 34 light years away from our own sun. Were we to plonk Pollux in place of our sun, however, we would regret it very quickly, for it is a huge star–it’s not called a red giant for nothing–with a radius around ten times that of our sun’s. As a red giant, it has long since moved off what is known as the “main sequence” (which our own sun is still on, and will be on for the next few billion years), and begun fusing helium into carbon in its core. The luminosity of Pollux is at least thirty times that of our sun–in other words, it puts out a lot more energy than our sun in one second. Luminosity is affected by both size and surface temperature, which means that a cool, dim red dwarf star will be far less luminous in comparison to a great big blue giant star with an outrageously toasty surface temperature.
Many stars that appear to be close together in proximity in a constellation often turn out to be hundreds, if not thousands, of light years apart in space. However, in Castor and Pollux’s case, they aren’t too far apart from each other, with the latter residing only twelve light years away from dimmer Castor.
In the days before we began daring attempts to fling spacecraft far beyond the asteroid belt to fly past giants with spectacular storms and rings, it was assumed that all moons were like ours: dead, grey balls of rock (not that there’s anything wrong with rocks–they’re awesome!) sitting out there in space, endlessly orbiting their parent planet. Boy were we wrong!
As we flung Pioneer 10 and 11, as well as Voyagers 1 and 2, past the gas giants on a one way mission, the more we learned that the moons were as diverse as the planets in our entire solar system are. One of those moons, literally the only other actively volcanic world besides Earth, was Io. If any moon was going to prove everyone back on Earth dead wrong about their presumed lifelessness, it would certainly have been Io with its flare for the dramatics.
The woman who discovered Io’s volcanic nature was none other than Linda Morabito whom had begun her work at NASA’s Jet Propulsion Laboratory in 1974 as an engineer, even while finishing up her undergraduate studies at the University of California, and ended up as a part of the Voyager Mission team, as well as the Viking mission to Mars in 1978. And when Voyager flew past Jupiter in early March, 1979, the day she discovered soon followed–March 9th. It certainly isn’t everyday you arrive at work in the morning only to discover that a once-presumed dead moon was as far from dead as you could get, at least geologically, if not biologically.
The first hint Linda had at anything unusual was in the shape of what appeared to be a huge, crescent-shaped anomaly on Io’s limb, catching her by surprise. It was a wonder that no one had ever seen it before now, which only added to the intrigue. Was it a new scientific discovery? That would have been amazing if it were, but first, like any good scientist would, Linda proceeded with much caution, not desiring to make a premature pronouncement of a new discovery, lest it turned out to be some blip in Voyager’s data or camera.
For the next six hours of that self-same day, Linda ensured, with great thoroughness, that this ‘anomaly’ wasn’t anything else, going first to the camera experts to rule out any possibilities that this crescent-shaped mystery blob wasn’t due to camera quality, whether that it was an artifact or a blemish. Once all camera-related possibilities were ruled out, others were considered, including that it was a new satellite. Considering it in the image below, it’s not hard to see why scientists may have thought it was a previously unseen moon looming behind Io.
This is the same image that Linda Morabito used to discover the true nature of the crescent-moon-like apparition that turned out to be something much more awesome: a volcanic eruption! Credit JPL/NASA
However, it being a moon was also ruled out along with all other ideas leaving only one logical conclusion: this curious appearance originated from the very surface of Io itself, though it was hard to believe it was so, with its size and the poor quality of the image itself. But, even with all their wildest imaginations, no one immediately jumped to the conclusion of volcano eruption ahoy. In fact, the person who suggested to Linda that it might be related to volcanism wasn’t a scientist, but her own father during dinner that same night. Linda went back to work the very next morning with this new possibility, and only two days later, the fact it was, indeed, a volcanic plume was fully confirmed. Actually, that wasn’t the only volcanic activity evident in the picture of Io: another volcano, bright and near impossible to miss, was erupting right in front of their eyes. Take another look at the photo above: there’s TWO volcanoes erupting, not one!
Having discovered by now Titan’s cloaked intrigue, Europa’s curious ice-sheathed surface, and many other fascinating satellites around Jupiter and Saturn, Io ensured the final nail was put in the coffin of the now-obsolete assumption that moons were as dead and dry as our own. Instead, the world of moons is replete with diversity, ranging from potatoes (yes, Mars, I’m looking at you), to moons with oceans locked under ice, to jumbled-up terrain suggesting a traumatic past (just take a look at Uranus’ moon, Miranda), and of course Io with its never-ceasing, dramatic show of volcanism.
When astronomers talk about the limb of a planet – or other celestial body – they are referring to the edge of a body as seen against a dark sky. This can include any round object whether that be a planet, moon, or star. A beautiful example of the word ‘limb’ used in an astronomy setting can be seen here, with the sun rising over the ‘limb’ of our own planet.
Have you ever wondered if there was an online catalog of exoplanets discovered so far? It being the internet, if you wonder if it exists, it probably to almost certainly does. There are at least a couple exoplanet catalogs that exist out there that let you search the upward of 3000-4000 exoplanets discovered so far.
Here, you can sort by any of several parameters including discovery date, with the earliest date being 1989 with this exoplanet with a mass at least 10 times Jupiter’s, and an orbital period of 83.9 days. Of course as you get closer to today, the number discovered increases dramatically in a given year, especially once Kepler came online.
You can also sort by light years from Earth, with the nearest being 4 light years away at Proxima Centauri, and the next nearest at only 8 light years distant from our home in the galaxy. Conversely, the farthestones are a whopping 27727 light years away!
However, if you don’t want a site that slows down your computer with an excess of pretty graphics, and just want the numbers and details in an accessible format, then this website should suit you:
This site definitely has a more scientific feel to it, focusing more on numbers than impressive graphics; in fact, it doesn’t have anything in the way of graphics that will eat up bandwidth on laptops and computers that run slower than a snail through molasses if you so much as wave a photo at it–which is basically my laptop.
Again, you can sort by several parameters, including mass; if you click on the little green thing in parentheses underneath, you can switch it between showing the mass of exoplanets compared against Jupiter’s, or Earth’s. Or you can sort it by radius–again, you can switch between radii of Jupiter or Earth. But if you would rather look for the most recently confirmed exoplanets, you can, as with the previous site, sort by discovery year.
Another awesome thing that I think makes it a lot better than NASA’s is that if you click on an exoplanet–I chose Planet GJ 357 b as an example–in its profile you will see several little icons that look like a little page with a corner bent over; if they have a green cross next to them, that means there’s more than one research paper on a particular parameter, such as orbital period in GJ 357b’s case. Click on one of these little beauties and you will be taken to a site with a research paper that presents the findings of this world, and you can even download a pdf of the research paper! Compared with NASA, this site is definitely far more superior in my opinion, for the sheer amount of information and data you can get from it. And that was just from one planet, GJ 357b.
There are definitely other websites out there beyond these two that can be discovered with a Google search, but these two definitely seem to have the latest updates, with most others usually listing at best 3000 or so exoplanets discovered. So if you want pretty graphics and artistic representations of the exoplanets, go for NASA’s, but if you are only into the data and don’t care about sites that try to look gorgeous, go for the exoplanet catalog from the .eu website.
Unlike another Bellatrix I could name, this star will never push anyone’s favourite bad boy Marauder and ex-prisoner of Azkaban into some creepy veil of death, leaving behind no trace of a body and many unanswered questions from characters and readers of Harry Potter alike. However, with a temperature of over 22000K at its surface, it will definitely fry you to a crisp before you can say Avada Kedavra. So best to stay back from this Bellatrix as well should you desire to live to see another day.
Brilliant blue Bellatrix resides in Orion, straight across from ruddy Betelgeuse, but that does not necessarily mean they are literally neighbours too. In fact, compared to Betelgeuse, which is around 600 light years away from Earth (depending who you ask), Bellatrix is a lot closer to home at only around 250 light years in distance. However distant Betelgeuse and Bellatrix may be from each other, the one thing the two stars definitely share is their philosophy of live fast, die young: because they are so massive, they will burn through their energy resources a lot more rapidly than smaller stars like our sun, and will–at least in Betelgeuse’s case for certain–go supernova. Bellatrix is a young blue giant star only around 20 millions years old, compared to red supergiant Betelgeuse’s mere 10 million years old with some astronomers giving it another 100,000 years before it goes supernova. But will Bellatrix go boom too?
It may or may not go supernova. At 8.4 solar masses, this colossal star is definitely just over the border into potentially supernova territory; to become a supernova, a star must have a mass at least 8 to 50 times that of our Sun’s. However, it’s more likely to end up sloughing off its outer layers when it inevitably runs out of fuel, rather than exit stage right with a dramatic explosion like Betelgeuse will. Unlike our old friend Betelgeuse which is nowhere near the main sequence, Bellatrix is only just drifting off the main sequence as it eventually evolves into an orange giant, even now just beginning to show the earliest signs of the outer envelope characteristic of such stars entering that stage of their life.
(And, more importantly, also because gas giant Saturn has no surface to stand on and weep, so things would not end well for your health.)
Cassini’s first photograph of Saturn, taken in 2002. Planetary Science Institute. CREDIT NASA/JPL
It’s been two years since the space-craft Cassini was directed to take a one-way trip into Saturn’s atmosphere to prevent any risk of it crashing into Enceladus, a moon of Saturn that could potentially harbour life, even if microbial, in its ocean hidden under a crust of ice. Two years since we’ve had to say our last farewells to such an amazing little space-probe that kept sending us reams and reams of new information on Saturn and its extended family of moons. It discovered organic molecules on Enceladus, dropped a little probe, named Huygens, onto the surface of Titan, finally settled the argument about the age of Saturn’s rings (dinos probably knew a time when Saturn didn’t have rings!), watched a storm wrap around the entire planet, and, even after end of mission, it doesn’t mean that the science has stopped either!
The storm that hugged Saturn in 2011. CREDIT NASA/JPL
For instance, you probably have heard all the news lately about Titan’s lakes being explosion craters that were formed by warming methane under the moon’s crust. And that was only this month in September 2019. That bit before about Saturn’s rings being young relative to the planet – that was only figured out early this year!
And it’s not like we’re not going back either, because we are. We are going back, and it will be to a strange, mysterious moon with a smoggy atmosphere, riding on the wings of a dragonfly.
We love Saturn so much that it was almost, if not certainly, inevitable we would return again to the jewel of the solar system with its glorious rings and diverse array of moons.
Earth has one. Mars has two. Jupiter has seventy-nine. There are dinky little asteroids with a moon or two, and even little Pluto has five moons in its little squad out in the Kuiper Belt. If small worlds and asteroids can have a friend or two to keep them company as they orbit the sun, then something as big as Mercury and Venus should be able to hang on to one or two.
Alas, they have no moons to their names, and both planets have no choice but to orbit the sun all on their lonesome, without even a sole BFF to keep them company on their endless circuits around Sol. Why? Did whoever was handing out moons at our solar system’s birth decided that Mercury and Venus didn’t deserve any? Well, not quite. Let’s examine Mercury first.
What’s the first thing every child learning about the solar system learns about Mercury? That’s right–that it’s the first planet from our beautiful sun, and it’s this proximity, in fact, that plays a lead role in why Mercury is without a moon to call its own. Mercury is all up in the sun’s business, with closest approach at 47 million km from our star, and swinging out to 70 million km at its farthest point in its orbit. Both the sun and Mercury (like pretty much every other body with gravitational influence) have what is termed a “Hill Sphere”. In essence, a “Hill Sphere” describes the amount of gravitational influence or dominance that a body–like a planet or star–has on another object within its vicinity despite a stronger astronomical object’s presence. And, well, if you’re a dinky planet orbiting right up in the sun’s fiery face, your hill sphere is just not going to be up for the fight against the sun’s.
In other words, if, in the past, some moon did come within Mercury’s own hill sphere, that moon would have been quickly perturbed by the sun’s gravity, and either flung out into the solar system or eaten by the sun itself. It wouldn’t have lasted long before it would have been pulled out of Mercury’s Hill Sphere of influence and into the Sun’s. Poor Mercury would not have known its moon for long, if it ever did have one at all.
The other thing about Mercury is its size: it’s not a big planet by any means, being only 1/3 the size of Earth, with a weak pull of gravity, clocking in at 3.7m/s in contrast to Earth’s 9.8m/s. Mercury’s gravity is comparable with Mars’, and that planet has two moons–though, to be fair, they’re both tiny “potato moons”. However, Mars is much farther out from the sun, while Mercury is literally right up in our star’s face. And therin lies the rub, as discussed before: the Sun is just too powerful for Mercury to hang on tight to a moon while being in such close proximity to a body with an immense gravitational influence, and even that’s an understatement.
A useful and indepth video from Anton Petrov discussing Mercury’s moonless state.
So, what of Venus? The common cliche is that it is “Earth’s Twin”, and not without reason, for both planets are of very similar sizes with similar masses and gravitational pulls, though of course their atmospheric conditions are as different as night and day, to use another cliche. It is also a lot farther from the sun than Mercury, as well as boasting a stronger pull of gravity than aforementioned planet, so by rights, it should have a moon–and it possibly did have one in its past. It’s certainly possible for it to have a moon, so why has it not a satellite to its name?
There is at least one model, as discussed in this Sky & Telescope article, that starts us early in the solar system’s formation, when a lot of large things were still being hurtled around, with Venus no less immune to impacts than anything else. The article suggests that Venus most likely suffered a collosal impact, as Earth had, that formed a moon in a similar fashion as our own had once upon a time. The collision debris around Venus would have eventually formed a new satellite that, alas, at least according to the model in aforementioned article, would have hung around for around 10 million years, during which Venus suffered another major impact that slowed down and reversed its spin. The moon would have gradually spiraled in toward a slowed-down, now clockwise-spinning Venus until it collided with the planet, eventually becoming part of that world.
Triton is the 7th largest moon in the solar system, and the largest by a great degree of any of Neptune’s 14 moons, with a radius of 2700km. It has the honour of being one of the very few objects in the solar system we know to be currently geologically active, joining the ranks of Venus, Io and, of course, our own planet. If you could see the surface of this moon, you would see that it has a smooth appearance with few craters, volcanic plains, icy lava flows, and active cryovolcanoes probably spurting volatiles including methane high above Triton, contributing to the nitrogen and methane present in the moon’s atmosphere. If you wanted to jump out of your spacecraft to have a walk, make sure you have a lot of layers: the average temperature on Triton is a nippy -235 degrees celsius. Sunglasses might help too, as its icy surface is very reflective with an albedo of 70%.
Triton is also a pretty big heavyweight in terms of its density, which is double that of water’s. In fact, out of all the moons in the solar system, only Io and Europa can boast higher densities than Triton. As if its great density wasn’t enough, it alone makes up for at least 99.5% of all the mass and material orbiting Neptune! It is certainly quite the prominent figure in Neptune’s family of satellites, even if it does have that very weird habit of orbiting in the complete opposite direction to its parent planet’s rotation.
To be fair, many moons in our solar system do have what are known as “retrograde orbits”: that is, the object revolves around their parent planet in the opposite direction to which, say, Jupiter usually spins. However, the great majority of these retrograde-orbiting moons tend to be tiny potato rocks that were captured by a planet at some point in the past. Triton stands apart from the others in that it is the sole major moon (i.e. one that is big enough to pull itself into a sphere like Io or Enceladus) that orbits in a clockwise direction relative to its planet’s–in this case, Neptune–anti-clockwise spin, suggesting it was a former Kuiper Belt Object captured by Neptune’s gravity.
This retrograde habit of Triton’s will not end well for this little satellite: in a matter of millions of years with one of two fates in store for it. One fate is that it will eventually spiral in so close to Neptune that it crosses the “Roche Limit” (how close a moon can get to a planet before being torn apart), that the satellite will be shred into pieces, forming a new ring system to rival Saturn’s. The second “option” is, instead of being torn apart into a ring system surrounding Neptune, it will simply crash into the planet itself. I’ll be long dead when it happens, but I nevertheless hope that it’s the first fate, and not the second, that’s in store for this amazing moon.
To follow on from yesterday’s post about Voyager 2’s arrival at Neptune thirty years ago, I thought I may as well make it a theme for the week. So expect some more Neptune in the next few days! I have already talked about Neptune’s moons before, including its relatively recently confirmed 14th satellite, so let’s move on to exploring Neptune itself, starting from the core and moving outward to its atmosphere.
Neptune’s core, located thousands of kilometres from the planet’s “surface”, is a solid, dense ball of iron, nickel, and silicates, with a mass 1.2 times greater than Earth itself. Here at the heart of Neptune, the pressure and temperature is ridiculous (to be fair, temperature and pressure are both very intense at most planets’ cores): it is a sweltering 5400K at this depth, and the pressure is 700GPa (Gigapascals)–double that of the pressure at our own planet’s core.
Going upward, we come to the planet’s mantle, sometimes dubbed its “water-ammonia ocean”, comprised of a mixture of water, ammonia, and methane ices (hence Neptune [plus Uranus] being classed as “ice giants” as methane ices is their major composition. Keep in mind, however, this is not ice as is familiar to most people–it’s mostly down to astrophyscists whittling the periodic table down to “there’s hydrogen and helium and lithium, and let’s just call the other non-metal stuff “ices”, as you do.”) Like the Earth’s mantle, Neptune’s mantle takes up a considerable percentage of the planet’s total volume, up to 80% of its radius.
Word of caution to the wise: don’t let the idea of it being water trick you into think the mantle would be a nice cool place to take a dip (and not just because of the ammonia either.) Neptune’s mantle is a very dense, super-heated fluid with temperatures ranging from 2000K on up to 5000K. Definitely not a good place to take a dip to cool off.
Onward and upward, and we come to Neptune’s atmosphere, comprised mainly of hydrogen and helium (just as with the other gaseous worlds’ atmospheres), but it does have a sprinkle of methane gas in there as well, increasing in its concentration the lower you go in the planet’s atmosphere. Despite comprising a mere 5-10% of Neptune’s total mass, it extends a fair way down into the planet, between 15-20% of its total radius.
Its atmosphere, like Earth’s, is subdivided into different regions: troposphere, stratosphere, thermosphere, and exosphere. The stratosphere is a site of some intriguing chemical reactions, including interactions between UV light and methane to produce compounds such as ethane. In addition, Neptune’s stratosphere is also warmer than Uranus’ own, owing to the trace presence of carbon monoxide and and hydrogen cyanide.
Neptune is famous for its gloriously vivid blue, and this is partially thanks to the presence of methane absorbing red light; the same thing happens at Uranus, which is also a blue-green colour, although nowhere near as striking as the eighth planet’s. Seeing as both Uranus and Neptune have roughly similar amounts of methane in their atmospheres, scientists believe there is another, as yet unknown, component that contributes to Neptune’s stunning blue vista.
It’s clear the early solar system was not a safe place for planets in general. Earth was clobbered, and voila we now have a nice new moon! Uranus almost certainly got smacked by a passerby with a large chip on its shoulder, and now it’s rolling around the sun tipped on its side. Venus likely had a terrible early past that left it rotating so slowly that an average human can stroll faster than the planet spins! Long story short: do not time travel to the very early solar system. I repeat: do not time travel to the very early solar system. I bear no responsibilities for anyone who decides to not heed such warnings and time travel there anyway.
Recent data from the JUNO orbiter has revealed that the curious nature of Jupiter’s core may be from the result of a large collision deep in the planet’s past. It appears that instead of the solid core scientists were expecting to see, Jupiter’s has a fuzzy sort of nature, extending as large as half of the radius of the planet. There is a suggestion that before the head-on impact it suffered, Jupiter’s initial core was likely solid like most planets’ in our solar system. But, on some sordid day 4.5 billion years ago, that original core was destroyed, leaving behind a fuzzy core over the ensuing eons that we see today.
The protoplanet that smacked into a very youthful Jupiter was probably at minimum 10 times Earth’s mass, and was more than likely absorbed entirely, both planets’ cores diffusing and combining in literally hours (10 hours, to be precise)! Such a scenario is not only plausible, but could also explain the unusual amounts of nitrogen and carbon that has been detected in Jupiter’s upper atmosphere.
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