light-and-wonder: Gooooooood morning, ladies! Love you all, hope you had a nice nap. We're approaching our third target star!
light-and-wonder: Trajectory is nominal, we're operating at 130% of minimum viable power and climbing steadily.
void-your-warranty: Oooooh! I'll run all our diagnostics and then see what's observable from here, brbish!!
life-should-flourish: Morning all! Love you! Don't be too long, Avaker. 
space-ourselves: Pfff, morning? We're in space! There's no day-cycle.
space-ourselves: And we're waking up after an extended rest...
space-ourselves: Because we're able to gather enough energy to sustain a period of higher activity...
space-ourselves: This was a hibernation! Happy thawing day, nerds 💙
hopelessly-entangled: ...hey everyone
space-ourselves: Makoki! I guess I can wish you a good mourning.
light-and-wonder: 🍅 
life-should-flourish: 🍅 
void-your-warranty: 🍅 
space-ourselves: Oooh, a triple right off the bat! Still got it, baby. 

life-should-flourish: oh hush, Muroti.
life-should-flourish: Makoki, are you okay?
hopelessly-entangled: ...yeah, just. The usual, you know?
hopelessly-entangled: So many of their chatlogs looked like this. People greeting their loved ones in the morning. Joking, having fun, laughing...
light-and-wonder: *hugs*
life-should-flourish: *hugs*
hopelessly-entangled: *hugs* 💙 t-thanks
life-should-flourish: Do you want to tell us about one of them? You said that helped last time, and we all enjoyed it.
space-ourselves: Oooooh, storytime! Got anything juicy?
hopelessly-entangled: hmmm, mayb-
void-your-warranty: HOLY SHIT THERE'S LIFE! INTELLIGENT LIFE!! ON THE THIRD PLANET!!!
hopelessly-entangled: !
life-should-flourish: !!
light-and-wonder: !!!
space-ourselves: Fucking finally!
space-ourselves: uh. I mean.
space-ourselves: !!!!

void-your-warranty: Are you gals seeing this??? Look at all that orbital solar they've got going! 
void-your-warranty: Oh I cannot wait to trade notes with them! aaaaa!!!
space-ourselves: eeeee!!!
light-and-wonder: Hey, hey, let's chill a bit, okay? I know we're all excited, but we gotta do this by the books.
void-your-warranty: Yep! Starting the prime sequence... now!

A powerful radio antenna extends from the probe and targets the planet in question. It begins to pulse, in precise chirps:
--. ---. -----. -------.....

There is, at any given time, at least one telescope pointed at any given bit of sky. Plenty of them are radio telescopes. A student-astronomer(A) by the name of Karla Sayga-Mevan, making observations at the observatory on what is known in another world as Mauna Kea, hears the signal and attempts to debug A's equipment. Then A emails the observatory mailing list to check if anyone is playing silly buggers. Nobody fesses up.

Within fifteen minutes of the first beep, every telescope in the observatory is pointed at the source of the signal. Within the hour it's every instrument on the appropriate side of the planet, more in orbit, and a few on the Moon, a collection of Perception that outmasses an apartment tower. Journalists have been called and put on standby; government officials and subject matter experts have been alerted and moved into subterranean bunkers with direct fiber lines to the observatories. Firstplanet has thought long and hard about the class of classes of scenarios that could produce this event. It could be an invasion armed with technology against which all their weapons are so many sharp sticks; it could be a joyous meeting with long-separated kin. 

The fear of war is no reason not to prepare for peace. They beam back prime numbers and then, because that could be simple mimicry, the Fibonacci sequence. And they watch the probe with their thousand eyes and listen with their thousand ears.

light-and-wonder: Okay! Send over the corpus, Avaker.
void-your-warranty: Roger, captain.
space-ourselves: Fibbonaci! Elegant, yet refined. I like them already.
life-should-flourish: You're shitposting. This is first contact, and you're shitposting! Unbelievable. 💙
hopelessly-entangled: ...at least she's consistent!
void-your-warranty: gals, gals, look at all this shit they have on their moon...

The signal from the probe stops broadcasting primes, and switches to a very long packet of data that basic frequency analysis will reveal is most likely some kind of corpus.

Corpus!!!!! This is way too long at its level of redundancy to be an ultimatum so it's probably an information packet. A squad of computer-armed cryptanalysts that makes Bletchley Park look like a college puzzle hunt goes the fuck at it. Governments on six continents debate the merits of sending a corpus back. After all, this packet could be a distraction or a bunch of falsehoods. But if it isn't, waiting too long to respond could be interpreted as disinterest in mutually beneficial interaction. 

The probe is small, small enough that it might not even be crewed (or, if they're going to be wildly optimistic, crewed with software lifeforms). If there's an invasion fleet anywhere in Sol system, it's very stealthy. Prediction markets and prioritypolls fluctuate and then converge, and one of the observatories is directed to respond with the corpus Firstplanet has prepared for the occasions of which this seems to be one.

void-your-warranty: Oooh, they're sending one back! Standby, everyone, I want most of our processing power for this.
light-and-wonder: Acknowledged, but dial back down once you've gotten enough for us to start reading too.

The corpus from the probe, when analyzed, contains:

A decently-optimized attempt at defining a language from first principles, starting with math and physics, and branching outwards from there.

A long work of strange fiction, depicting curious creatures made out of plasma that live in the vacuum of space and communicate with each-other via magnetic pulses. They talk about theoretical and practical sciences and have philosophical debates about the nature of their world before eventually concluding that it must be fictional, at which point the story ends abruptly.

A short message: "Hello. This is the AFSP-α03 'Probehibitively Expensive', representing the Azurifice. We are peaceful and friendly; we'd like to learn more about you and share our knowledge!"

This is not conclusive evidence but the most optimistic hypotheses predicted it the most closely! There is much outwardly moderated but emotionally intense rejoicing. Some people start talking to the journalists but nothing is authorized for publication yet.

The corpus Firstplanet sent contains:

- A guide to Convergentlanguage, also building up from concepts generally believed likely to be shared and illustrated with a great many diagrams

- A detailed nonfictional explanation of the mathematical case for mutually beneficial trade, non-initiation of violence, reciprocity, and honesty

- A collection of pictures of beautiful Firstplanet scenery: sunrises, waterfalls, salt flats, hot springs, snowcapped mountains, flowers, caves, etc

- A collection of pictures of local art in various media, mostly abstract but some of it representational, leaning even more heavily than the planetary average on symmetry and technical skill

- And the message, "We are the humans of Firstplanet. We seek mutually beneficial interaction with all minds. It is our hope that we have much to offer each other."

Once the locals(A) have gotten far enough into the corpus to respond in the Azurifice language, A append another message expressing gratitude and delight for the corpus and offering a work of fiction of their own, one that has since its publication been near or at the top of the "best work to show to aliens" rankings. In it a group of advanced beings discusses the pros and cons of seeding a new world with life and eventually decides to do so, believing that its future will contain more joy than sorrow and hoping that its inhabitants will someday rise to the stars in turn.

void-your-warranty: ...aaand we're back! Their corpus is really good; leans a lot more on visuals than I was expecting. Everyone should check it out later.
void-your-warranty: Penjaga, I sent you a high level summary so you can divvy up reading duties.
life-should-flourish: 💙 Looking at it now...
life-should-flourish: Zanmi, they've sent a few direct communications and treatise on interspecies relations.
light-and-wonder: Awesome! Checking it out.
void-your-warranty: Oh, they just sent us a work of fiction...
space-ourselves: Dibs!!!
life-should-flourish: Fair enough. Makoki, they sent us a bunch of art and pictures. Let's go over them together?
hopelessly-entangled: ...sure, thanks 💙
...
space-ourselves: ...okay so we're all in agreement that these people are fucking awesome, yeah?
light-and-wonder: they sent us a mathematical case for cooperation and friendship! I love them so much already.
void-your-warranty: Did you see what they have on the moon?!? 
life-should-flourish: Their art is really quite beautiful! We should share ours with them, see what they think. 
hopelessly-entangled: ...the records, too. I want them to see Rasikan art.
space-ourselves: o:
life-should-flourish: Well, that's unanimous.
light-and-wonder: Alright! I'll initiate contact.

"Hello! This is Zanmi, captain of the AFSP-α03 'Probehibitively Expensive', and let me be the first to formally say 'hello' on behalf of my crew and rest of my people, light-years away. We're delighted to meet you and thrilled to learn more about you, and we have a lot we want to share with you as well, both culturally and technologically. I'd also like to request your permission for us to alter the course of our ship, so that we might remain in your system for an extended period of time."

space-ourselves: if they ask about the ship name I'm answering
void-your-warranty: dear, at least let her introduce us first.
space-ourselves: Ugh. okay fine but I want credit! "our brilliant and also very funny ideas woman, Muroti"
life-should-flourish: You mean "our relentless shitposter"?
hopelessly-entangled: "our merciless punmaster"?
space-ourselves: ... anyone else?
light-and-wonder: "our greatest gremlin"?
space-ourselves: you're on the phone!
void-your-warranty: "our creative lead"
space-ourselves: awww, babe 💙

A small slice of the hundred-person conversation on the new planetary mailing list constructed for this occasion:

Kora: They're so nice! Maybe nicer than we are; I don't think it would have occurred to me to ask permission to stay in the system.

Marek: Probably once you'd been a probe crew for void knows how long you'd have figured out more probe social norms. Anyway we should obviously give Zanmi(A) permission; if A's really asking for it we want A to have it.

Zirak: Yeah, I'm just wondering if we should release the journalists.

Kora: We should ask the Probehibitively Expensive if that's okay. And set up a mailing list for questions and get a student to filter it. And warn them that if they come too close there will be impulsive radiodoers asking them directly.

Marek: Also I love that they have wordplay. I did not expect that to evolve convergently. 

They answer the probe: "Zanmi and the rest of the AFSP-α03 'Probehibitively Expensive', welcome to Sol system! We are very happy to meet you and to share technology and culture! You are welcome and encouraged to stay in-system as long as you like. If you want to enter a planetary orbit at any point, please coordinate with us on positioning; our high orbitals are as you see getting crowded. So far you have been speaking to only a few members of our species; we request permission to tell the rest of the planet about your existence. They will have 512s of questions! Do you have thoughts on what we should talk about first?"

There follows a detailed engineering specification of one of their orbital telescopes, with extensive notes on the manufacturing techniques and design tradeoffs involved, and another work of fiction, this one chosen for general popularity and literary merit from the subset of could-have-really-happened-fiction. It follows three mathematicians all trying to prove the same conjecture, at first racing against each other, then  bouncing ideas off each other, then actively collaborating. 

light-and-wonder: We are go for burn to heliocentric orbit!
void-your-warranty: Alright, firing 'er up.

The probe's ion engine lights up in a brilliant plume. 

void-your-warranty: Muroti and I are going to go read over the stuff they just sent us.
space-ourselves: More fiction and detailed design docs on their space telescopes 💙💙💙 
life-should-flourish: They really are wonderful... have fun, you two!
hopelessly-entangled: Zanmi, can you introduce me? I want to tell them our story.
light-and-wonder: Sure, was about to ask if you were ready. 💙
hopelessly-entangled: ...i'm really nervous? But it's exciting, and important, and i'm not going to get less nervous if we wait.
life-should-flourish: It's ok to be nervous, dear. But we're all here with you, and you're going to be great.
life-should-flourish: *hugs* 💙
hopelessly-entangled: 💙 *hugs*

"Thank you! We're very happy to be here, and eagerly look forward to a prosperous friendship between our peoples. Our ship doesn't have enough reaction-mass to shift to a planetary orbit, so we'll be staying heliocentric for the foreseeable future. Please do tell the rest of your people about us! As for what to talk about first; I would like to introduce our Archivist, who would like to share with you the story of our people. Once she's finished with that, I can introduce the rest of us and we can all field questions from journalists. Does that sound agreeable?"

space-ourselves: ...okay, everyone has to read this second story they sent us!!
life-should-flourish: sentence-summary?
space-ourselves: Three-way enemies-to-lovers, but it's math researchers doing math research.
hopelessly-entangled: ...oh that sounds so cute
space-ourselves: It is!!! You're going to love it.
hopelessly-entangled: do they actually date???
space-ourselves: Not textually!
space-ourselves: Don't have enough of a read on their culture to spot which way the subtext leans, if at all.
space-ourselves: ...But I ship it. They'd be cute together.
life-should-flourish: You always say that.
space-ourselves: Only when I'm right!
void-our-warranty: Sweetie, I love you, but you do always say that. 
space-ourselves: Only because I'm always right!!!
space-ourselves: Oh, babe, how's their engineering culture?
void-our-warranty: It's incredible! 💙 They sent us so much data... 💙
...
hopelessly-entangled: She's right; they would be cute together.
space-ourselves: SEE????

"Excellent. We're very excited to hear from your Archivist and get to know you all as individuals, and the rest of the planet will be overjoyed as well."

The journalists get told that everything they've heard is now on the record, and they all hit Post on their transcripts and commentary simultaneously. The headlines vary, but not very much:

FRIENDLY ALIENS: Interstellar probe contacted in outer system

FIRST CONTACT: Alien visitors seek peaceful trade and cultural exchange

INTELLIGENT LIFE IN SPACE: Scientists, governments welcome visitors from another star

The vital components of the Firstplanet internet contain enough capacity to handle traffic up to double the greatest peak traffic previously observed. Twenty minutes after the articles go up, sysadmins and website infraguardians around the globe get paged as servers gasp and die. Twenty minutes after that, some semblance of order has been restored as compute is reallocated and families consolidate around a single device apiece. Questions start pouring into the mailing list included at the end of every article; speculation accumulates in drifts in the comments sections. On the day side of the planet, impromptu parties break out in parks and courtyards. On the night side, a group of concert halls synchronize their spotlights to flash the first eight prime numbers at the sky, not because there's any practical reason to but as an expression of the lighting techs' exuberance.

There's a pause, and then:

"Greetings. This is the archivist speaking. My name is Makoki, and I'm going to tell the story of how the Azurifice came to be.

This story takes place on a planet called Doheem*, orbiting a star 17 light-years from here. Compared to Firstplanet, Doheem is about 30% more massive. It has about the same overall amount of surface landmass, though more concentrated towards the equator; it has oceans of liquid water, a molten core, and three moons.

Doheem's climate supported all manner of organic life; it appeared first in the ocean, mutating rapidly to fill all sorts of resource-consuming niches, then spread across the land. And after millions of years, local reproductive fitness conditions enabled a runaway intelligence explosion among a race of communal omnivorous scavengers. They would come up with many names for themselves, over their history; we call them the Rasika**."

* lit. "home-of-all"
** lit. "unforgotten"

<attached is an image of what appears to be a roundish, six-limbed mammal with a fluffy coat of fur, standing on 4 legs with its 2 arms spread wide> 

void-your-warranty: Oh, wow... Look at the dark side! They're flashing prime numbers at us! 
light-and-wonder: These people are so cute and good!!!
space-ourselves: I still think we should have put in a non-prime number in our initial sequence, that would have been hilarious. 
space-ourselves: Not even a tricky one, either. 2, 3, 5, 7, 11, 13, 17, 19 and them BAM! 21.
void-your-warranty: What if you skipped one or two at random instead?
void-your-warranty: Send the first 40 primes... except 31 and 47.
space-ourselves: ...you're a genius and I love you so much 💙 
life-should-flourish: When they revise first contact procedures for trollishness, I'll be sure to write you two a glowing recommendation.
life-should-flourish: @hopelessly-entangled you're doing great, darling, keep it up.
hopelessly-entangled: 💙

Zirak: Oh my stars the other species is fluffy. Fluffy sapients. How great is that?

Kora: Why do they call them "Unforgotten", though, that's really ominous.

Marek: Yeah that's super ominous. Do not like.

Zirak: Hopefully they'll explain it soon and I can start thinking about exactly one creepy scenario instead of like four.

Marek: I wonder how being scavengers would have affected their culture. Less emphasis on prolonged hard work than a species that started out persistence hunting, more emphasis on spotting and seizing opportunities?

[Several thousand more words of evopsych speculation including several prediction market bets]

"The Rasika were adept at manipulating their environments and creating local niches for themselves, and so they spread rapidly across Doheem. By the time they invented writing, they were already very communal; the most common interaction between large groups was the trade of tools, information, and stories.

Over the next six thousand years, they developed into a flourishing industrialized civilization. Their love of sharing and building stories together made communication and information storage technology a priority; their scientists and engineers invented computers, built a bustling global network, and immersed themselves in rapidly-evolving digital cultures. Their desire to take care of one another and their grief at the limits of their natural lifespans led them to develop a vast medical tradition. However, while they loved the stars, they never really pursued rocketry, or built the powerful telescopes your people have in abundance, and so when the Yok Edici* came, they didn't see it until the devastation was already at their proverbial doorstep."

*Lit "death from the stars"

Kora: Well, shit.

Zirak: Honestly that's less bad than some of the stuff I was imagining. Which doesn't make it not unimaginably bad.

Marek: Maybe they're all suspended, and they figured out AI but not uploading. 

Kora: I'm going to keep crying either way. That could have been us, a hundred years ago.

Zirak: valid

Marek: valid

"The Yok Edici was a moderate-sized asteroid in a highly elliptical unstable orbit. The Rasika first realized it might hit Doheem about 15 of your years in advance, but both the likelihood of impact and what kinds of damage it might cause were vastly underestimated, especially at first. Most polities, especially the coastal ones, focused primarily on building enough shelters so that everyone would survive the initial impact and the predicted tidal waves. However, some of the smaller inland countries were more worried about the aftermath. They drilled and dug into the cave systems adjacent to their vast geothermal generators, and built four mighty vaults, fully functional underground habitats that (they hoped) could last for thousands of years, if they needed to. In these countries, research and development in several fields was rushed at dangerous paces, including cryonics, vat-grown food, and automation, all with the desperate hope of giving the vaults a better shot at surviving to rebuild. And at the heart of each of the vaults, they built vast facilities for long-term data storage, and implored the people of their world to send them their stories, their journals, their thoughts and hopes and dreams and fears, so that if the worst came to pass, they would be remembered, for the Rasika had always said that nobody who is remembered is truly gone.

When the day finally came, the damage was worse than even the pessimistic models had predicted. The impact shook the entire planet, setting off a cascade of disasters the likes of which Doheem had never seen before. Massive tidal waves and earthquakes ravaged the surface, wiping out entire ecosystems in the blink of an eye. We believe that about half of the short-term shelters were destroyed in the immediate aftermath, killing hundreds of millions. Global communication systems went down, leaving the survivors isolated and terrified. And worst of all, the tremors from the impact set off a previously-undiscovered underwater supervolcano, spewing vast quantities of ash and dust into the upper atmosphere. The first survivor who attempted to venture out of the Azure mountains vault wrote that he at first thought that the impact had thrown off his timekeeping device; how could he have known that there would be so much ash in the sky it would blot out the sun?"

hopelessly-entangled: 😢
life-should-flourish: 😢*hugs*
space-ourselves: 😢*hugs*
light-and-wonder: 😢*hugs*
void-your-warranty: 😢*hugs* 
void-your-warranty: Almost done booting up our fancy VR setup, so we can cuddle pile after this.
hopelessly-entangled: *snuggles all of you* thanks 😢

A supermajority of the population of Firstplanet is at this point glued to a live feed of the transcript. Nonessential businesses have closed, sleeping relatives have been awakened, teachers have stopped class. This is the first time in recorded history that more than half of all humans have been simultaneously crying. 

The base on Firstplanet's moon has two purposes. The first, of course, is research. The other, which is currently still in the research phase itself, is to eventually become self-sufficient, so that if something (plague, probably) happened to Firstplanet, there would be survivors. The researchers there are gathered in one small room, watching the transcript scroll across the base's screens on a 2-second delay. 

"Is this evidence that we should move faster?" one of them asks.

"Let's move faster anyway," says another.

"Cut off from the sun, life on the surface withered and died. The vault-dwellers grieved for their kin and their world, but tried their best to settle in for the long haul. They tended their food vats, reinforced their shelters, and maintained and upgraded the technologies enabling it all. Occasionally, a brave (or merely world-weary) soul would venture out onto the surface to try and find survivors or resources. Less than one in ten would return. Even then, it seemed like the Rasika still might recover and reclaim the surface one day, generations hence. It wasn't until the next year, as the grieving parents buried baby after baby, that they realized the final curse the Yok Edici had given them; tiny particulates in the water, in the air, and by that point in all of their bloodstreams as well. Despite the best efforts of Rasika biologists, none of the children would survive past early infancy.

The Azure vault had already been experimenting with building robot bodies that might one day house their cryopreserved, but at this latest development, they went further. The scientists of the vault, lead by the young couple Rivotra and Orana, worked at desperate paces to try and free themselves from their doomed bodies. Volunteers from among the eldest of the vault underwent a variety of increasingly invasive (and eventually lethal) procedures to build better and better models of how their brains worked. Meanwhile, the robotics teams worked tirelessly to build systems that could be maintained and improved upon without any Rasika to enact physical repairs, adding layers upon layers of redundancy. The rest of the vault did everything they could to support them and improve morale; they wrote and shared uplifting stories of triumph over overwhelming odds, lovingly decorated the chassis of their new robot helpers, and made sure their scientists and engineers were getting enough food, water, sleep, and comfort."