You are still in it. The group chat from your school class, with the class name and the graduation year, the cover photo from a June festival nobody quite remembers. The last message was a «congratulations!!» with three balloon emojis, answered with a heart. Before that, a chain message about a bank scam. No one leaves, because leaving feels rude. No one speaks, because what is there to say?

And, somewhere in that list of thirty names, there are one or two people you still talk to every week. People who knew you with braces on your teeth and still know when you're having a hard time just from the way you write «I'm fine».

Why did those two stay while the other twenty-eight turned into a birthday reminder on the calendar? And why did that inseparable friend from university, the one from the whole summer of 2012, vanish in six months without a single fight? Friendship ends differently from a relationship: almost always without a final conversation, by drifting apart, and that is why it leaves behind a question no one answers.

Crossing two charts helps answer part of it. It is the same technique used for couples, the synastry, and between friends it looks at different pieces.

Some friendships are born of circumstance: the same classroom, the same office, the same beach in January. While the circumstance lasts, the friendship seems eternal. When it ends — graduation, the job, the return from holiday — the friendship finds out it was made of that circumstance.

And some friendships are born of recognition. You talk to the person for the second time and it already feels like the tenth. In synastry, this shows up in the contacts between one Sun and the other's Sun, between the two Moons and between the Ascendants, and in the material of each chart: the element and modality that dominate in each. Similar material tends to give easy conversation from day one. Opposite material tends to give admiration with friction, which can last a lifetime if both know what they are admiring.

A summer friendship tends to have strong Venus and Jupiter contacts, and a busy house 5: fun, laughter, plans. It is wonderful, and it is the part that depends on being together. The thirty-year one almost always has something more underneath, and that something more tends to sit in the Moon and in Saturn, which is the subject of the next sections.

Neither one is lesser. Some friendships exist for a summer and fulfil exactly what they were meant to.

You lost your job, or broke up, or someone in the family got sick. And the friend who was at every party disappeared. She didn't answer, or answered with a short line, or showed up three weeks later as if nothing had happened. And another one, whom you barely spoke to, showed up at your door with food.

The piece that describes this in the chart is the Moon, the piece about comfort, along with house 4. Each person's Moon says how she offers care and what she does in front of someone else's pain. Some people move closer and some freeze up, because they don't know what to say and would rather say nothing wrong. The friend who disappears is sometimes afraid of getting in the way.

In friendship synastry, one person's Moon is compared to the other's Moon, and you read whether one's way of caring reaches the other as care. A Moon in earth cares by bringing soup and sorting out the bank. A Moon in air cares by calling, talking, sending the right text. One in water cares by staying, and one in fire cares by getting you out of the house. All of them are caring, and each can go unnoticed by someone expecting something else.

It is one of the most relieving discoveries this kind of reading brings: the friend you thought was absent was present, in a language you weren't reading.

One sends an eleven-minute voice note. The other replies in writing, two days later, with three lines. The first concludes the friendship has gone cold. The second didn't even notice there was a question in minute seven.

Mercury describes how each person talks: the pace, the format, the length of the reply, how much they need to talk in order to think. In synastry, one person's Mercury is compared to the other's Mercury, Sun and Moon, and whichever planet of each falls in the friend's house 3 joins in too. That is where you see whether the two understand each other with half a word or need to translate everything.

Much drifting apart starts this way, over the pace of conversation. No one fought; one stopped texting because she felt she was talking to herself, and the other thought everything was fine because, for her, it was. Two friends who discover that one thinks out loud and the other thinks in silence can settle this with one sentence and save ten years.

And there is the other side: the friend you talk to for three hours and it feels like twenty minutes. That shows up in the chart too, and tends to be one person's Mercury sitting well with the other's Sun or Moon.

Some friends you see twice a year, and when you sit down in front of her, it feels like the last conversation was yesterday. No one keeps score of the absence. No one takes stock. This is the friendship that feels most like home.

The 11th house is the house of friendships, groups and the people we choose to walk alongside. In synastry, one person's planets that fall in the other's house 11 describe how she enters your life: as part of the group, as an ally, as someone who pulls you into a project. Saturn is the piece about consistency and keeping your word, and Saturn contacts between two people tend to describe friendships that weigh a little at first and then never move from their place.

One person's Saturn on the other's Moon, for example, can be the friend who gives the hard advice no one else gives, and who seems cold at first. Years later, she is the only one whose advice you still ask for. An easy Venus contact is fun; a Saturn contact stays.

This is also the part of the reading that says whether the friendship can survive distance, moving cities, children, one person's marriage and the other's divorce. Consistency has a pattern, and it can be read.

No one likes to admit it, but some friendships have rivalry inside them. The good news you share and she receives with a slightly flat «that's nice». The promotion, the wedding, the body, the kids who came earlier. Sometimes the competition runs both ways and neither says so.

In synastry, this friction shows up in the contacts of Mars, of Saturn and Pluto between the two charts, and in tense aspects in general. Mars with Mars can be the pair who push each other to run a marathon, and can be the pair who cannot decide where to have dinner without one feeling steamrolled. One person's Pluto on the other's personal planet describes an intense friendship, with a dose of influence that needs watching so it doesn't turn into control.

This is also where differences in pace and space come in. One needs daily contact to feel like a friend, the other needs weeks alone to come back whole. Neither is wrong, and the friendship that lasts is the one that figured this out in time.

Naming the friction is usually half the work. The other half is a conversation the reading makes much easier to start.

Everyone has one. The friend who said «go for it» when you weren't sure about taking the job in another city, going back to school, ending things. The one who introduced you to a book, a course, a country. Years later, you look back and see that a piece of your life passed through her hands.

In synastry, this is read in Jupiter, in the North Node and in houses 9 and 11 received. One person's Jupiter on the other's Sun or Ascendant tends to describe exactly this person: the one who expands, the one who believes before you believe. One person's North Node touched by the other describes a friendship that pulls in the direction life wants to go, even when it's uncomfortable.

And there is a curious effect that shows up when one of the two moves to another city. Friendship built on Venus and house 5 tends to lose strength with distance, because it lived off doing things together. Friendship built on Jupiter often grows stronger: the one who left becomes proof that leaving was possible, and the one who stayed becomes the root the other comes back to visit.

That growth usually runs both ways, and it is worth noticing. The one who always felt like the friend who receives is often, in the other's reading, the one who gave her courage at a moment she does not even remember.

Friendship synastry does not say who is a good friend and who is not. It does not rank anyone, it gives no score to a friendship, and it does not calculate a percentage of compatibility. Two people with difficult synastry can have the most loyal friendship of their lives.

It does not predict the end of any friendship and it does not decide whether someone is worth keeping close. If a friendship hurts, the answer lies in what happens between you, and the chart can help you understand it, never tell you to stay. And a friendship that ended was not a failure either: many served their purpose and finished.

It is also not meant for investigating the other person. The best use is with your friend knowing, and even better, reading it together over drinks. Using someone's chart to justify an old hurt, without her being able to answer, trades a conversation for a verdict.

And it depends on both birth times for the part about the houses. Without them, houses 3, 4, 5 and 11 disappear, leaving the planets by sign and by aspect, which still say a good deal about closeness, conversation and friction.

Almost two thousand four hundred years ago, in the Nicomachean Ethics, Aristotle divided friendships into three kinds. Those of utility, which exist because one serves the other, like a colleague at work. Those of pleasure, which exist because it is good to be together, like the summer crowd. And those of virtue, where each one likes the other for who she is.

The first two, he wrote, end easily: when the utility or the pleasure ends, the friendship ends. The third is the hardest to find, and also the one that lasts. He added a detail anyone in her forties can confirm: this kind of friendship takes time and shared life, and nobody builds it in a hurry.

Open your school group chat today and run your eyes down the names. Try to place each one in one of Aristotle's three drawers. The two people you still talk to every week are probably in the third, and the chart shows why they got there.

And the questions that come up most on this subject, with the short answer: