Xeelee Sequence species

This article details the various alien races and human offshots present in Stephen Baxter's Xeelee Sequence of future history.

upergalactic civilizations

Xeelee

The Xeelee are a hyper-advanced civilization which has existed for billions of years. Their technology far exceeds that of any other species, and lesser civilizations strive to acquire bits and pieces of Xeelee science. Even crude or damaged, this technology gives a huge technological boost to a species. The Xeelee are sometimes called "The Baryonic Lords", and are arguably the most advanced species in the universe.

The Xeelee are spread across the universe, typically being concentrated in the heart of galaxies where they use the black holes for their own purposes. However, they have spread gigantic artifacts and huge inscrutable structures throughout space.

Humanity first became aware of the Xeelee from the "Friends of Wigner", a cult-like group of humans from the future, during the events of Timelike Infinity. However it was not until the end of the Qax occupation that humanity had direct contact with the Xeelee when Jim Bolder visited the site of The Ring (giving it the colloquial name of "Bolder's Ring"). This object, also known as The Great Attractor, is drawing in galaxies for millions of light years around with its awesome gravitational well, and the current xenophobic human government that rose after the fall of the Qax believed that it was an immense weapon.

Humanity avoided conflict with the Xeelee at first, but after conquering all other races in the Milky Way, they began to war with the Xeelee. This war lasted over ten thousand years, with the last three thousand years being a virtual stalemate siege of the Milky Way's core black hole (named "Chandra" in the series).

In the events of Exultant humanity finally forced the Xeelee out of the Milky Way galaxy. 100,000 years passed, with humanity rising and falling throughout history. The scattered shards of humanity unified and began warring with the Xeelee once more, this time on a grander scale. Despite humanity being nearly as advanced as the Xeelee were, the war led nowhere. Humanity stopped attacking the Xeelee and returned to the Milky Way.

Little is known of the Xeelee in the next centuries since humanity was largely confined to one galaxy and had almost no contact. It was widely believed that the Xeelee had forgotten the human race, or had chosen to permanently ignore them. However, many millennia later, the stars in the Milky Way started disappearing - encased in Xeelee construction material. War broke out again as humanity was driven from the stars and slowly, over 300,000 years, forced back to the original Solar System. The Xeelee reduced the Human race severely with the fighting, and eventually trapped humanity on Earth, folding the planet into a pocket universe to seal mankind from the rest of the universe.

This was when humanity finally realised their mistake. The Xeelee had been fighting another menace: the Photino birds - dark matter beings who had been accelerating the aging of the stars. Humanity was at best a distraction but the Xeelee had decided to put them aside.

After humanity's fall the Xeelee returned to The Ring. The Ring had not turned out to be a weapon after all; it was an "escape hatch" -- A huge construct that tore a hole in the universe and opened a portal to parallel universes. The Xeelee's fight against the Photino Birds had been lost, and the Xeelee sought to escape. Their final act was to leave "lifeboats" of Xeelee technology for the less advanced species trapped in the doomed universe.

Photino birds

Photino birds are a species of dark matter entities that inhabit the gravity wells of stars. Because this habitat is dangerous, the photino birds engage themselves in an effort to age stars to the point where they are not prone to supernovae. This effort would make the universe uninhabitable by baryonic life forms; it therefore catches the attention of the Xeelee, whose ultimate purpose is to combat the photino birds. Photino birds are discovered to inhabit Earth's own sun.

Despite the best efforts of the Xeelee all attempts to defeat the birds fail and the Xeelee and the other surviving Baryonic life are forced to flee via the Ring. After this the few remaining Baryonics watch the long projects of the birds until the last of the stars go out.

The Photino birds are not considered as an evil species. With the likely exception of the Xeelee, they hardly know about other existing life-forms. Lack of knowledge on other species has caused them not to realize that the aging of stars has unfortunate effects to the "normal" universe.

Milky way civilizations

Humanity

Qax

The Qax are the second extrasolar intelligent species to dominate the solar system. Their race is comprised of very few and long lived individuals. Being composed of convection cells, a Qax requires complex life support and can be damaged easily - therefore their contact with the humans is usually indirect.

queem

The squeem are a race of group minded aquatic beings, or "fishes", as referred by the humans. They are the first extrasolar intelligence contacted by mankind in the Xeelee series, and by the time of that contact, they occupy the solar system and enslave the human race. The Squeem are not especially intelligent or advanced, and resort to stolen technology from the Xeelee, for instance, the hyperdrive.

ilver Ghosts

The silver ghosts are a race that humans encounter during the era of the Third Expansion. Silver Ghosts consist of a set of symbiotic organisms inside a super-reflective shell that efficiently maintains internal temperature and reflects radiation. The silver ghosts are therefore able to exist in space without additional vehicles. The species is known for its pursuit of physics, particularly their experiments regarding changing physical constants in regions of space. They are eventually conquered and nearly wiped out by humans, who adopt their silver skin technology for their own purposes.