Commets, have always held a special place in our hearts. Wait did I say hearts. I meant nightmares because back in the day, the night sky was a tapestry on which we sketched our mythologies, our creation, myths, the gods that ran our lives.
It was eternal, it was unchanging, it gave structure to our beliefs. So when something new happened like say, a big bright swoosh appears across the sky. That meant something usually not something good for the majority of human history.
Comets have been harbingers of doom, bad omens, bad signs of things to come. This is actually where the word disaster comes from dis, aster, meaning bad star. Many major historical events, defeats in battle, deaths of kings, natural disasters plays and pestilence all have been associated with the appearance of a comet.
But then we figured out that the Sun is actually the center of the solar system that we’re. Just one of many planets orbiting around it and the Comets are just big icy rocks blowing snow around them as they go, and that these icy rocks have actually hit our planet and caused major mass extinctions in our past.
So they kind of were harbingers of doom. But still comets remain the mystery. Where do they come from? How many of them are out there, and this is something we didn’t really fully understand until 1950 and the answer it’s pretty far out.
The Oort cloud is an incredibly distant sphere of trillions of icy artifacts from the very beginning of our solar system. It’s, an unthinkably vast field of potential comets radiating out in all directions from the Sun and it’s.
An archaeological treasure trove because our solar system was born when a cloud of dust and gas coalesced into itself until it got hot enough to spark fusion creating a star in an enormous nuclear blast.
This blast blew ice and debris out beyond the gravity. Well, the star, leaving the heavier rocky dust and debris around the star which, eventually because of physics, weirdness flattened into an accretion disk, later becoming the planets and moons and asteroid belts, and that’s.
Why comets are a particular interest to astronomers because they’re, a picture of what the solar system was like when it was still fresh in the oven that’s? Why the rosetta mission landed on comet 67p to take measurements and learn what the composition of the comet is, so we can see what elements were present at the very birth of our solar system might be wondering why don’t.
We just fly out to the Oort cloud and you know take measurements there. We, you know New Horizons, just blew past ultimate Uli. Could we just keep going out to the Oort cloud and the answer is yes, we totally could and New Horizons will definitely reach the Oort cloud in about 300 years.
That’s. How far away the Oort cloud is it’s, ridiculous? The idea that the solar system is bordered by an immense cloud of comets is something that’s been thrown around since the early years of the 1900s.
But it was Yong Hendrick or a Dutch astronomer who actually did the math behind it and put it on solid mathematical footing in 1950, which ironically, was one year before kuiper published his paper in 1951, so we actually sort of discovered the Oort cloud.
First, according to arts paper, which I’ll link down below the trajectories of the Comets didn’t indicate that they were coming from other stars. They weren’t interstellar objects, meaning they had to come from.
You know fairly close by to where our star is their orbits indicated that they’ve, always been a part of our solar system orbiting just outside of it. The specific comments that Oort looked at are what are known as long period comets.
These are comments whose orbits take at least 200 years, given the speed and angle of Oort sample comments, he concluded that they came in from a distance of about 50,000 astronomical units from the Sun.
An astronomical unit or au is the distance from the Sun to the earth or 93 million miles or 150 million kilometres. Just for comparison, Neptune’s orbit actually takes it out to about 30.1 AU from the Sun, and the Kuiper belt extends out to about 58.
You just to reiterate the Kuiper belt is 50 au away. The Oort cloud is 50,000 au away and extends for another 100,000 au. After that also just for comparison, one au, the distance from the earth to the Sun takes about 8 minutes for the light to reach us to reach Neptune.
It takes 4 hours and 12 minutes for light to span the Oort cloud would take a year and a half with such a vast field to play, and the trillions of comments. Aren’t exactly cramped, even if the astronomers say that the mass of the Oort cloud is probably 50 to a hundred times that of Earth.
They’re so far apart. They rarely come anywhere near each other, so rather than object to object, collisions being what dislodges these things and causes them to fall down toward the Sun, it’s, thought more likely that that’s.
The whole solar system passing through some interstellar gas or maybe even another star, passing close by and it’s, gravity and messing things up. This also explains why a lot of comets tend to come from similar directions.
You know, disturbances that happen a long time ago, so, whatever it is, it does it. Something dislodge is one of these comets and it starts falling towards the Sun. So what happens next well when they reach a distance about 121 au from the Sun? They kind of take a pause, a Helio pause that is, the heliopause, is the boundary of the Sun.
Stellar wind. You may remember hearing in 2012 that voyager actually crossed into interstellar space. That means that it actually passed the heliopause, and this is actually a second line of evidence that were presented when making this argument.
The idea that if there wasn’t a big huge cloud out there outside of the the sun’s influence. Then these long period comets would have burnt out years ago either by crashing into a Sun or a planet or eventually their tails would just evaporate because it’s.
The evaporation of ice from the comet’s nucleus. That creates that big gorgeous tail, that’s, freaked us out all these years that tail by the way, always flows away from the Sun. So even after the comet has circled around the Sun and is moving away from it.
It’s. Actually, moving in the direction of its tail, most people know that, but you know some don’t, but the point is: if these comets lost tail material every single time they went down through the solar system, then they would have probably lost their tails.
In about two million years, so how could you have these comets flying through the solar system for 4.6 billion years and still have tails, or it argued that it can only be because they spent the first 4.
6 billion years beyond the heliosphere once they got knocked into? Where it was warm, they were on a ticking clock, but as long as they were beyond the heliopause, they were safe. So there had to be a reserve of new comments so far out that we can’t see them.
Hence the Oort cloud and astronomers speculate that some comets with short orbital periods, which came from the same place. They just kind of got caught up in the gravity well of the Sun, probably being slowed down by passing by certain planets.
One of those captured comments is arguably the most famous comet of all time. Halley’s Comet by the way young, or it was one of the few people in history that actually got to see. Halley’s Comet twice in his lifetime.
As many of you know, Halley’s. Comet comes around once every 76 years will yawn or it was born in 1900. So he got to see it at 10 years old in 1910 and then he got to see it again in 1986 and in fact, when it came around in 1986, it wasn’t at a very good angle for him to see it from the Ground so he actually got to go up in a and see it from the sky.
They made sure that he got to see it, which is fitting because he’s. The guy who discovered where that comet came from now fun Halley’s. Comet fact the one that he saw in 1910 actually coincided with the death of Mark Twain who actually predicted his death because he was born at the same time that it came.
The previous time, which was 1835, in fact he said quote, it will be the greatest disappointment of my life. If I don’t go out with Halley’s Comet, the almighty has said no doubt now. Here are those two unaccountable freaks.
They came in together, they must go out together. Now I was actually 11 when Halley’s, Comet came in 1986 and I got to see it. I remember it was a big deal. It was all over the news and everything, and it actually happened on my birthday ironically, and I and I got a little telescope that has Halley’s, Comet a little commemorative telescope.
It’s at my dad’s place and I hope I & # 39. Ll still be around to see it when it comes around in 2061. That would be cool. I mean well, who knows that this rate, I might actually get to see it from space, but the one in 1986 was also cool because ESA’s, Giotto spacecraft actually got up close and personal and got some really cool photos of it.
Actually, one more cool thing about Halley’s. Comet is that you can actually see little parts of it twice a year, because there are two media showers that edit upwards in May, and the Orionid z — in September that are caused by the earth.
Passing through the cloud of dust that Halley’s, Comet left behind so pretty cool. Now this might be a good time to point out that technically we’ve, never actually seen the Oort cloud, but in the years since Orton made his calculations more and more evidence is piled up to back up his theory, including the 2003 discovery of Sedna Sedna’s; a dwarf planet that was first spotted by a team from Caltech led by Mike Brown.
Mike Brown is one of the people who had a lot to do with the fact that Pluto got demoted to a dwarf planet. So Pluto lovers, don’t quite love him that much, but to be fair, he also discovered Eris, which is actually more massive than Pluto, and he calls that a dwarf planet too.
So there’s. That Sedna makes his closest approach to the Sun at 76 au, but it has an elongated orbit, stretching all the way out to 936 AU. They say this makes it eligible to be considered an inner Oort cloud object or an IOC object.
Although there’s, a lot of disagreement about this, because a lot of people think that the Oort cloud – doesn’- t really begin until about 2008. You but one argument that it should be considered an inner or cloud object is because it extends way beyond the Kuiper belt, which kind of fades away after about 48 au.
So it’s, definitely from whatever is outside of the Kuiper belt. As for whether or not that can be considered an Oort cloud, that’s, a discussion for another time, but is it possible that the Oort cloud starts in closer than we think it does? Is it possible that said that actually interacts with some objects in the Oort cloud? It’s, hard to say for sure guys, like Mike Brown, have been looking for more and more distant orbiting objects for a long time now, and there’s, a good reason for that, because they’re.
Looking for planet 9, in fact, brown heads up a team of researchers, including konstantin batygin fellow astronomer, Chad, trujillo and scott sheppard, currently working out of hawaii. What they’re looking for is a huge planet about six times the size of Earth.
That’s orbiting way outside the Kuiper belt. That could be stirring up these Oort cloud objects. So I’ve talked about this back in 2016, but these guys are studying a handful of comets that all seem to be coming from the same direction and probably got stirred up.
At the same time, period mean it was all caused by one object that passed through them in a particular time, and the math they had to work with is just as solid as anything that Oort had or Kuiper had or Clyde Tombaugh who found Pluto.
In fact, Tombaugh was looking for the exact same thing when he found Pluto, but Pluto is just way too small to be the culprit. The point is, according to some of the most reputable and accomplished astronomers out there, planet 9 exists and it’s out there and it’s still waiting to be discovered.
If they can prove this exist, it will completely revolutionize our understanding of how our solar system is constructed and maybe even give us a better understanding of our entire stellar neighborhood.
What might also help is being able to see the Oort cloud itself? Badging and brown are looking forward to 2022 when the large synoptic survey telescope goes online and Chile. This one might actually be strong enough to actually spot Oort cloud objects, but another option is to actually find work.
Clouds around other stars – and this won’t, observe the Oort cloud directly. It’s just way too far away, but it would be able to infer that there is an Oort cloud by the interference of Oort cloud objects around stars.
Even the James Webb Space Telescope is not gon na, be strong enough to see for cloud objects. So for now we have to let those objects come to us. If we want to get up close and personal with them, and one possible option could be Sedna itself.
It’s currently on an approach trajectory and according to Ethan Siegel from the starts with a bang vlog. He thinks we could actually intercept this. He says there are two launch windows may of 2023 and June of 2014 and in either case we could actually launch a probe that would get there a probe that would take 24 years to arrive.
I’m gon na be an old man by then well. By that time we could just wait for Halley’s. Comet to come back Halley by the way was not remotely the first person to spot Halley’s Comet. He was just the first person to calculate its trajectory and make a prediction as the wind would come back so when it did come back, everybody’s like oh okay, we’ll name the comment after you and I think that’s fair enough.