The Star That Said Goodbye

The problem was that their star was in the wrong place.

Not wrong like a little bit off, which could be the telescope, or the tracking software, or the fact that Soren had bumped the tripod twenty minutes ago and spent five minutes pretending he hadn't. Wrong like it shouldn't be there at all.

Maya had found it Tuesday. They were supposed to be comparing archival images of a star field near the constellation Libra, matching old survey photos against new ones to measure proper motion. Tiny shifts. Patient work. Soren liked it. Maya kept calling it "spot the difference for space."

But one dot had moved too much.

"It's probably a satellite," Soren said, for the second time that week. He was sitting on the concrete ledge of the school observatory, his notebook open, the comparison images printed out and taped side by side.

"Satellites don't show up in survey archives from nineteen ninety-seven," Maya said.

"Could be a near-Earth asteroid."

"It's not moving like an asteroid. It's in both images. Same dot. Just way further along than anything else in the field."

Soren looked at the two printouts again. She was right. Everything else in the frame had shifted by tiny fractions of an arcsecond between the old survey and the new one. This particular point of light had moved noticeably more.

"Okay," he said. "So it's closer to us. Nearby stars have more proper motion. Parallax."

"Maybe," Maya said. But she said it the way she said maybe when she had already moved three steps past maybe.

"What?"

"I looked up its radial velocity in the database. The spectral shift."

Soren waited.

"It's blueshifted. Coming toward our part of the galaxy. And fast. Like, the number I got doesn't make sense."

"How fast?"

"Over a thousand kilometers per second."

Soren put his pencil down. That was wrong. Stars in the neighborhood of the Sun moved at tens of kilometers per second relative to each other. Maybe a hundred for the fast ones. A thousand was something else entirely.

"Show me," he said.

They went inside to the computer lab. Ms. Okoro had given them access to the online spectral databases for their project, which she probably regretted because Maya had been in there every night that week. The room smelled like old carpet and the vending machine in the corner.

Maya pulled up the catalog entry. The star had a designation, not a name. A string of letters and numbers that meant nothing to anyone who wasn't looking for it.

Soren read the radial velocity entry. Then he read it again.

One thousand one hundred and thirty kilometers per second.

He converted it in his notebook. Roughly four million kilometers per hour. He stared at the number.

"That can't be right," he said. "Nothing in the disk moves that fast. That's faster than the escape velocity of the whole galaxy."

"I know," Maya said.

"So it's leaving."

"I know."

They sat with that for a moment. Soren wrote the number down, then circled it, then wrote a question mark next to it.

"What kicks a star to a thousand kilometers per second?" he asked.

Maya had already been reading. She turned the monitor so he could see the paper she'd found. It was from two thousand and five, and the title had the words "hypervelocity star" in it.

"Binary system," she said. "Two stars orbiting each other. They fall close to the supermassive black hole at the center of the galaxy. Sagittarius A-star. Four million times the mass of the Sun."

"And?"

Maya held up two fingers close together, then flicked one away. "The black hole captures one. Flings the other. Like a slingshot. The energy has to go somewhere, so the surviving star gets launched. Hard."

Soren leaned back. He tried to picture it. Two stars, companions, orbiting each other for maybe billions of years. Drifting too close to something with a gravity well so deep that space itself bent around it. And in one encounter, one interaction, one star swallowed, the other thrown so hard it would never stop. Would cross the entire galaxy. Would leave.

"It lost its partner," he said.

"It lost everything," Maya said. "It's not bound to the Milky Way anymore. It's moving faster than escape velocity. It'll just keep going. Into intergalactic space. Forever."

The vending machine hummed in the corner. The fluorescent light buzzed. Outside the window, the stars looked fixed and permanent, which they were not.

"How many of these are there?" Soren asked.

"They've found a couple dozen confirmed ones. But the models say there should be about a thousand in the galaxy right now, at any given time. Crossing through. On their way out."

A thousand stars, right now, screaming through the Milky Way at speeds nothing else could match. Not orbiting. Not staying. Just passing through, because something enormous and irrevocable had happened to them, and now they were going somewhere no one could follow.

Soren looked at the catalog entry again. The little string of letters and numbers.

"Do you think anyone else has looked at this particular one?" he asked.

"Probably. It's in the database. Someone measured it."

"But has anyone looked at it? Through a telescope? Actually watched it?"

Maya understood what he meant. "Probably not. There's no reason to. It's faint. It's just data."

"Let's go look at it."

They went back up to the roof. It took twenty minutes to align the telescope, find the field, and locate the right dot. Ms. Okoro had gone home hours ago. The school was quiet. The sky was clear and very cold.

Soren looked first. Through the eyepiece, it was just a point of light. Faint. Steady. Indistinguishable from any other star unless you knew what you were looking at.

But he knew.

That light was moving at four million kilometers per hour. It had been torn from a companion by something with the mass of four million suns. It was crossing the galaxy alone, and it would never come back, and right now, tonight, it was passing through a part of the sky where two eleven-year-olds on a school roof could see it.

"Your turn," he said.

Maya looked. She was quiet for a long time.

"It's the loneliest thing I've ever seen," she said.

"It's the fastest thing I've ever seen," Soren said. "We just can't tell by looking."

"That's what gets me. If we didn't know, it would just be a dot. If we didn't look it up. If we didn't wonder why it moved too far. It would just be a dot and we would never know it was saying goodbye to the whole galaxy."

Soren thought about that. About all the things that looked ordinary until someone wondered why they didn't quite fit.

The star traveled on above them, silent and fast beyond comprehension, aimed at the dark between galaxies where nothing waited and no one watched.

Maya pressed her eye to the lens again.