DISCOVERY
2341 CE
The spectrogram, marked with the characteristic emission lines of the nebula, made a long glowing stripe across Werner‘s wallscreen. He scratched the small scab at his temple, where the mosquito had drawn blood. If he’d only stayed indoors like his fellow amateur astronomers, and played with the data feeds from the space ‘scopes, he wouldn’t be facing yet another malaria test. The bug had spread to Germany from the south.
“Take out the background stuff,” Werner said. His system swept a vertical line from left to right across the long horizontal band, and the spectral emission lines sharpened into clarity. Werner was bored. He’d been over XXX a dozen times; why was François bothering him with it now? Something about a stray line he couldn’t identify. The message hadn’t been too clear, which was normal for the Arabic-woven syntax of the messages from François. This one had been more than usually cryptic, which meant that François had been excited.
“Show me the base reference lines in the displayed region,” Werner said. A second stripe appeared below the one high on his wall: the standard hydrogen line, some others scattered nearby, all fitting in at just the right redshift for the nebula. XXX was moving away from the sun and its planets.
One line was out of place, fuzzy and faint. It hovered just on the blue side of the hydrogen reference line, barely above the rejection threshold. Werner stared. If the line matched the hydrogen reference, this was odd. The nebula was drifting farther away, but this object, directly in line with the nebula, was moving in the opposite direction, toward Earth.
Werner sat back in his wobbly swivel chair. “Select line just to blue side of hydrogen reference A. Compute apparent velocity based on reference A.”
A soft, lazy female voice said, “Nine hundred twenty kilometers per second in approach, standard error plus or minus eighty kilometers per second.”
What was bothering François? Werner said, “Connect me with François Abdu’l-Karim.”
A moment later the long, bony face of François hovered just below the spectroscopic display, dark eyes wide in their deep sockets. “You got my message. Did you find it?”
“Find what?” Werner asked.
“The line.”
“Yah. It’s just hydrogen, blue-shifted. Something’s coming our way from the nebula at about sixteen hundred kilometers per second, but at that rate it won’t reach us for millions of years. You think it’s something unusual? There are all kinds of objects zooming around out there.”
“You are sure it’s the hydrogen?” François raised a eyebrow.
“Unless something else is getting emitted at some monster shift, it is.”
“Because I saw the same thing near the same place six months ago.”
“So?”
“It wasn’t in exactly the same place.”
Werner straightened up, leaned forward. “What?”
“I did parallax on it yesterday. That is why I called you. My spectro software has had a long bug.”
“What do your parallax readings indicate?” Two readings six months apart: if the object appeared to have ‘jumped’ between the time of the first reading and the second, it had to be close enough that the earth’s position in its solar orbit could make a difference. That was too close.
“It’s about twenty five thousand AU out from the solar system.”
Far too close. The nearest star to Earth was just over twice that far away. “Wait. How do you know that it’s parallax and not apparent motion?”
“Because a year ago I ran the same measurements. It was very close to where it is right now. I had thought it was apparent motion.”
Werner leaned back. “You’re telling me that this thing that’s showing us weak hydrogen-line emission is coming straight toward us, and it’s almost here.” He started calculating in his head. “At its current speed and apparent distance, it’ll be here in about seventy-five years.”
François said, “Shall we report this to the Union together?” The two young men had recently joined the Informal Astronomical Union, an amalgam of several smaller Web societies of amateur astronomers tediously cataloging intragalactic objects. Once in a while the amateurs hit something interesting, but not like this.
“Yes,” Werner said. “I’ll work up the details on the blueshift, and you do the parallax and the rest.”
“Thank you,” François smiled. “I owe you one.” He vanished from the wallscreen.
Werner studied the spectro display. His smile slowly faded. Whatever this thing was, coming so fast at the Solar System, it emitted a faint hydrogen line. If it was a star, why wasn’t it brighter? Ah, a brown dwarf, maybe a near-black dwarf. That put its size at about a tenth of a solar mass.
In the hot Frankfurt evening, Werner shivered. What would a body that size, coming so close, do to the Solar System? Would it drag some planet out of orbit and fling it blindly at the others?
Slowly the implications of what he and François had found began to sink in. This was no minor item for some footnote in a catalog on some Website. No. The human race was staring down the barrel of God’s gun.
