The landscape of exoplanet systems is a wasteland: from an orbital point of view, the majority of systems look like the beat-up survivors of giant dynamical battles. The reason for this is simply that their original configurations were not “Lindy” — that is, not built to last indefinitely.
If it exists, Planet Nine should be found in the next few years by the Vera Rubin telescope. The problem is: no one know how a planet could have got there — until now.
While we humans get massive health benefits from social interactions, the same cannot be said for planetary systems. Passing stars are like darts being thrown at the Solar System.
Life on Earth has about a billion years left. There’s a 1% chance of a star zooming within 100 astronomical units of the Sun in that time. Could a flyby rescue life on our planet?
Could a protoplanet, or even a full-sized planet, be lurking in the icy darkness of the Oort cloud?
Earth will lose its oceans. Chaos may destabilize the rocky planets. The Sun will go red giant and swallow the inner planets. The outer planets’ orbits will widen as the Sun becomes a white dwarf. Passing stars will destabilize the planets’ orbits and, in about 100 billion years, finally strip away the last planet.
The list of factors needed for life to originate on Earth remains uncertain, although water was essential. Earth’s water was likely delivered by planetesimals scattered inward by Jupiter. Yet, ironically, Earth would probably be much wetter with no Jupiter.
TL;DR: The planets’ orbital shapes, tilts and spins oscillate due to the gravity of the other planets — this has a strong effect on Earth’s climate. On billion-year timescales the terrestrial planets’ orbits are chaotic and cannot be predicted precisely.
Asteroids and comets are the leftovers from the planets’ formation. They’re like the potato peels that end up on the floor instead of in the mashed potatoes. So, what have those leftovers been up to the past few billion years?
TL;DR: The Moon is thought to have formed in Earth’s last giant impact with a planetary embryo about 100 million years after the start of planet formation. Highly-siderophile elements indicate that ~0.5% of Earth’s mass was accreted after that point.
TL;DR: The giant planets underwent a dynamical instability that shook up the entire Solar System and likely ejected an extra ice giant. The instability happened early, perhaps triggered by the dispersal of the gaseous planet-forming disk.
This is chapter 6 in the Solar System’s story. This is an action-packed, epic chapter in which a lot of pieces of the puzzle are put together in different ways. (It’s my favorite part.)
TL;DR: Most giant planets form in a bottom-up way, by first growing large cores and then piling gas on top. They migrate throughout their formation. Jupiter may have protected Earth from migrating ice giants.
TL;DR: Earth- to Neptune-mass planets migrate through the disk — usually inward, and fast. Giant planets carve gaps in the disk (“anti-donuts”) and migrate slowly, usually inward. Things can get crazy when lots of planets migrate together.
This is chapter 3 in the Solar System’s story. We’re chugging along, growing bigger and bigger things… Planetesimal accretion After mountain-sized (~100 km-scale) planetesimals form from concentrations of drifting pebbles, they continue to grow in two ways. The simplest growth route for planetesimals is simply to crash into other planetesimals; this is called planetesimal accretion….
TL;DR: planetesimals are mountain-sized rocks (sometimes with ice) that grow from clumps of drifting dust (“pebbles”). The two types of meteorites come from planetesimals that formed in different parts of the Solar System and remained separate.
The TL;DR version of this post: the Sun formed in a cluster of about 1000 stars. The Sun’s gas-dominated disk disappeared in a few million years, about the same timescale as the cluster’s dispersal.
This blog series will discuss what we know (and don’t know) about the formation and evolution of our Solar System.
Just one stretched-out orbit takes up lots of space
Can’t add any planets, there just isn’t space
Now, circles are best. And trust me, I’ve tried
Eight or ten orbits fit nicely inside.
The Sun will puff up to gargantuan size
As big as Earth’s orbit. And fill up our skies
The red giant Sun will eat Venus alive
But Mercury’s first. It will not survive.
Some people like to call Jupiter and Saturn the “architects” of the Solar system, as though they had a clear plan for how our system should turn out. Not us. We think of the gas giants as bullies that pushed Earth around and made a lot of decisions for us.
Ceres is Queen of the belt. She’s the best-a.
Her husband is Pallas. Court jester is Vesta.
She makes up a third of the belt on her own
She’s cratered and icy and sits on her throne.
Have you ever been lost in the desert?
Stumbling along the sand dunes, the Sun beating down on you, your mouth sticky and dry. All you can think about is water…
To start things off, a limerick: My dear old friend ‘Oumuamua I asked her — What’s up? What is new-ah? “I’ve been thinking of That guy Borisov The interstellar number Two-ah!” Figuring out what’s up with a new population of astronomical objects is like going to a party without knowing the dress code. Here’s what’s…
Imagine this. You’re drinking your morning coffee. A small blob zooms at top speed through the kitchen, into the hall and out an open window. You only catch a quick fuzzy glimpse before it’s gone. What was that thing? What’s your first guess? A neighborhood cat? A squirrel? Maybe something more exotic like a raccoon…
A space mission to intercept an Oort cloud comet — or, if we’re lucky, an interstellar object like ‘Oumuamua.
Where would we be without the occasional asteroid crashing into the Earth?
Planets orbit stars. Moons orbit planets. But no moons have their own moons (let’s call them submoons). Why is that?
Short answer: Well sort of, but it’s more useful to think of it as being built from the same stuff as comets. Like an Uncle of the comets. Read on for an explanation. Earlier this week my wife mentioned a headline she saw. “Pluto is a giant comet? Whoa!” It was all over the place:…
One fine week in May, well, I needed some peace
I packed up my bags and I headed to Nice…
Mars is a weirdo. (Well, as far as planets go). Why is it so small (just 11% as massive as Earth)?
I once ordered a beer then straight away spilled it all over the bar. There was just a tiny sip left in the glass. Frowny face.
Remember ‘Oumuamua, the weird-shaped rock flying through the Solar System? Just like my sip of beer, it might only be a small piece of what it once was.
In Rendezvous with Rama (by Arthur C. Clarke), a mysterious object is discovered passing through the Solar System. The object has a strange shape — it’s a giant cylinder. It was discovered by the Spaceguard survey, designed to find objects that might impact Earth (so-called near-Earth objects). Spoiler alert: the cylinder is a spaceship sent…
The asteroids may be cosmic refugees, ejected from their homes to wander the Solar System, eventually settling in the asteroid belt.
Imagine a dry Earth. No waterfalls. No oceans. No beer (or people to drink it). A sad place. Water is pretty important stuff. In this post we will go deep into how Earth got its water (much deeper than in this post from a while back). And since it’s connected with how Earth formed, our…
Systems of super-Earths may form as long resonant chains, most of which go unstable.
At a Solar System party, in a room full of planets, the asteroid belt is full of angst. And it should be. It’s out of place. It’s wearing a clown outfit but it’s not a costume party. What makes the asteroid belt so different? Well, for one, it’s not just one object like each individual…
This post could also be titled: How blogging and social media help make science happen. Here is the story. Planet Nine was conjectured in late January 2016. In February 2016 I started to think about where Planet Nine may have come from. This led to 3 blog posts, each exploring a different origins story for…
It is hard to know where things come from. If I drink a Belgian-style beer brewed in Colorado using hops from Washington state and I live in France, where did the beer actually come from? And what does that mean anyway? The cosmic situation is just as confusing. We know where the planets are right…
We are discussing the origins of Planet Nine. In part 1 we explored whether it could have been produced during an orbital instability in the early Solar System. In part 2 we showed that Planet Nine could have been captured from another star. Here we will explore another plausible idea that is a little less…
We are discussing the origins of Planet Nine. In part 1 we explored whether it could have been produced during an orbital instability in the early Solar System. Here we will explore a much more exotic origin. Scenario 2. Planet Nine is a planet that formed around another star and was captured by the Sun…
It’s official: there might be an extra planet in the Solar System. It’s called Planet Nine. Like Hansel, it’s so hot right now. To find it you must trek past Uranus and Neptune into the dark reaches of the Solar System. It’s on an orbit hundreds of times larger than Earth’s, that takes 20,000 years…
Giraffes are covered in patches. The patches are brown and the space in between the patches is white. Everyone knows this. Here is something you probably didn’t know: you can see those patches in infrared light. In simple terms, infrared light measures heat (at least at the temperatures we are used to in everyday life). …
A while back I performed an experiment called build a better Solar System. The game was to make better use of the Solar System’s habitable real estate. In the game I was required to keep all of the Solar System’s planets (and large moons) and their orbital configurations. Just by switching the orbits of different…
[UPDATE: a new series on building the ultimate Solar System starts here] The Solar System is a disappointment. It does contain an inhabited planet with forests and oceans and frisbees and beer (Earth). But it only has one. There are a couple worlds with some potential, but they are pretty disappointing too. Jupiter’s moons Europa…