The Last Light

The astronomer was crying, and that was the part Maya could not figure out.

Not sobbing. Not making a scene. Dr. Alvarado was standing at the far end of the rooftop with her phone pressed to her ear, and her voice was steady, and tears were running down both sides of her face. She finished the call and put the phone in her pocket and stood there looking at the city lights.

Maya looked away. She went back to aligning the eight-inch Dobsonian the way Dr. Alvarado had shown them, nudging the tube until Sirius sat dead center in the finder scope.

"She okay?" Soren asked. He was crouched over his notebook, sketching the eyepiece arrangement for the visitors who would arrive in forty minutes.

"I don't know."

Soren glanced up. Then back down. He added a label to his sketch.

Dr. Alvarado came back wiping her eyes with her sleeve, and she did not explain. She checked each telescope with the brisk efficiency of someone who had done this two hundred times. When she got to their Dobsonian she leaned into the eyepiece and said, "Good. Sirius. Nice choice."

"It's the brightest," Maya said.

"It is. Do you know what it will become?"

Maya knew. She had known since she was eight. "A white dwarf."

"Both of them, actually. Sirius B already is one." Dr. Alvarado tapped the telescope tube. "Point this about eight arc-seconds from the main star and you won't see anything. Sirius B is there, though. A white dwarf the size of Earth with the mass of the Sun. Incredibly dense, incredibly hot, and just sitting there. Cooling."

She said the word cooling the way other people said forever.

Then she walked to the next telescope, and that was all.

Soren wrote something. Maya looked at the scope.

"She said cooling like it meant something else," Maya said.

"Yeah." Soren clicked his pen. "How long does a white dwarf cool for?"

"I don't actually know."

He pulled out his phone. Maya watched him scroll, then stop, then scroll back up, then read more carefully. His eyebrows did the thing they did when numbers got strange.

"What."

"So a white dwarf has no fusion. No fuel. It's just leftover heat radiating away. And the time it takes to cool down completely is..." He turned the phone toward her.

Maya read the number. She read it again.

"That can't be right."

"Trillions of years. More than trillions. A hundred trillion, maybe a quadrillion, depending on mass."

"The universe is thirteen point eight billion years old."

"Right."

They looked at each other.

"So," Maya said slowly, "no white dwarf that has ever existed has had enough time to finish cooling."

"Not even close. Not even a fraction of the way."

Maya sat down on the concrete ledge. The city hummed below them. She could feel the cold through her jeans.

"There is no such thing as a cold white dwarf," she said. "Anywhere. In the entire universe. They haven't had time."

Soren sat down next to her. "The article calls the theoretical end state a black dwarf. A white dwarf that's finally cooled to background temperature. Zero radiation. Invisible. And it says the universe is too young for a single one to exist. Anywhere."

Maya looked up at Sirius, the real one, the bright furious point above the city haze. Somewhere right next to it, Sirius B was glowing. It had been glowing since before humans existed. It would be glowing long after the sun burned out and the Earth was gone and every single thing she had ever heard of was finished.

And it would still be warm.

"The universe is a baby," she said.

"That's what it feels like, right? Like we're in the very beginning of something."

"Not even the beginning. The first second of the first minute."

Soren was writing now, fast, the way he did when the inside of his head wasn't enough. "Okay. Okay. So here's what's strange. Everything we think of as the universe, all the stars, all the light, all the galaxies doing everything, that's a tiny bright blip at the start. The vast majority of the universe's future is just white dwarfs sitting in the dark. Cooling. For longer than we have words for."

"That's most of the story," Maya said. "The part with light in it. The part with us. That's the opening sentence."

They sat with that.

Dr. Alvarado's voice came from across the rooftop. "Visitors in twenty. Check your focus."

Maya stood up but didn't move toward the telescope yet. "Do you think that's why she was crying?"

Soren looked at her.

"Not the white dwarfs. But maybe she got bad news. And maybe she came back and talked about something that will still be warm in a quadrillion years because..." Maya stopped.

"Because it helps," Soren said. "Knowing that."

"Does it help? Or does it make everything feel tiny?"

Soren closed his notebook. Opened it again. "Both. That's why it works."

Maya almost understood what he meant. She understood it the way she understood most true things, which was all at once and not quite completely, a shape she could feel before she could draw.

The visitors started coming up the stairs. A father carrying a toddler. Two teenagers with a school assignment. An old woman with a cane who looked at the telescopes like she'd been waiting all week.

Dr. Alvarado transformed. Bright voice, steady hands, pointing out constellations. She aimed the Dobsonian at Sirius and told the old woman to look.

"Oh," the woman said, with her eye to the lens.

Maya leaned over to Soren. "Should we tell them about Sirius B?"

"That it'll outlast everything?"

"That it's right there, next to the brightest star in the sky, and it's going to keep glowing for longer than the universe has existed so far. And nobody can see it tonight but it's there."

Soren smiled. "Yeah. Tell them that."

The old woman stepped back from the eyepiece, and Maya stepped forward, and the first thing she said was, "There's something next to it you can't see."