Nemesis

Nemesis is a hypothesized and probably factitious companion star to the sun. It is said to be trans-Neptunian and to enter the Oort cloud every 26 million Julian years. When it so enters the cloud, according to theory, it perturbs it and sends a shower of comets into the inner solar system. A significant portion of these comets then strike the earth and cause extinction-level events. To date no astronomer has developed definitive evidence for the existence of the Nemesis star. (Two comprehensive surveys of the sky that might decide the issue are currently under way, and a third survey by a polar-orbiting rocket probe is planned.)

A study published in July of 2010 urges even evolutionists to abandon the Nemesis hypothesis, on the theory that any hypothetical dwarf star ought to have changed its orbit long ago, as a result of multiple close encounters of the Sun with other nearby stars, but has not.

Background of the Nemesis Hypothesis
In 1984, paleontologists David Raup and Jack Sepkoski published their time-series analysis of the geologic strata that, according to uniformitarian geology, were laid down during the last 250 million years. They determined that twelve extinction-level events (ELEs) had occurred during this time, and that the time between one ELE and the next was 26 million years. Previous investigators had linked two of these putative ELEs to large meteorite impacts. Raup and Sepkoski therefore concluded that such events (including the alleged extinction of the dinosaurs 65 million years ago) happened regularly and might have an extraterrestrial cause.

Proposal and naming
Two independent teams of astronomers then proposed the same type of cause: a companion star to the Sun, either a red dwarf or a brown dwarf, having a sidereal period equal to the period of Raup and Sepkoski's ELE cycle. Subsequently, Muller published a book-length treatment of the Nemesis theory.

Muller and others named this star Nemesis after the Greek goddess of retribution.

Orbital characteristics
Nemesis, if it exists, would probably be in a highly eccentric, almost parabolic orbit around the Sun. The semimajor axis would be 88,000 AU and the eccentricity 0.9. The sidereal period of 26 million years would be inferred from Raup and Sepkoski.

Muller holds that Nemesis is at or near aphelion at present and would not cause another ELE until the year 15,000,000 AD. Yarris has suggested that Nemesis would be visible in the constellation of Hydra.



Physical characteristics
Whitmire and Jackson have suggested that Nemesis would have a mass varying from 2 * 10-4 to 7 * 10-2 times the mass of the sun. This is the range of masses of brown or black dwarf stars. Muller has argued that the star is a somewhat hotter red dwarf, of magnitude between 7 and 12.

Controversy
Nemesis has been a subject of heated controversy ever since the publication of the papers by Whitmire and Jackson, and Davis, Hut, and Muller. Muller has perhaps compounded the controversy by asserting that Nemesis would be visible with binocular field glasses or a small to medium-sized telescope. No astronomer, amateur or professional, has even claimed to have seen Nemesis, much less had a sighting confirmed.

Muller has suggested that the Moon suffered a bombardment event as recently (per uniformitarian theories) as 400 to 600 million years ago, and that Nemesis might have been the cause. Yet no geologist has developed evidence for periodic bombardment of the Moon, in line with the alleged 12 ELEs on the earth.

The orbit of Nemesis would be unstable, and many astronomers hold that Nemesis should long ago have escaped the Sun's gravity. Muller disputes these claims and insists that Nemesis ought to remain a part of the solar system for another billion years.

Recently, Walter Cruttenden at the Binary Research Institute has decided that Sedna, a scattered disk object, actually is in orbital resonance with Nemesis. Sedna's sidereal year is estimated to be 12,000 Earth years. If Sedna is in resonance with Nemesis, then it would probably have an actual period of 13,000 years and be in a 20:1 resonance with the hypothetical star.

However, even uniformitarian geologists do not necessarily accept the claimed periodicity of ELEs.

Re-examination
On 2 July 2010, Mellot and Barnbach published a study suggesting that the ELEs have occurred over 500 million years, during which galactic tides and encounters with passing stars should have perturbed the orbit of the hypothetical Nemesis, but did not. Therefore, they now say, such a star cannot be blamed for ELEs occurring regularly ever 26 million years.

A creationist perspective
The Nemesis hypothesis depends on uniformitarian geology, and in particular the acceptance of deep time. If, instead, one accepts the model of the global flood, then one has no need of a theory of a companion star (or, for that matter, a cloud of comets for the star to dive into). The alleged regular layers of extinct species could all result from laminar flow patterns during the Flood.

Search for Nemesis
As mentioned, no one has yet seen Nemesis. A recent infrared survey of the sky failed to detect it. But at least two more wide-ranging surveys of the sky are planned, by the Panoramic Survey Telescope and Rapid Response System (Pan-Starrs) and the Large Synoptic Survey Telescope (LSST)

Video
ERy-MTfgulc Richard Muller's hour-long lecture, given May 4, 2006 at the University of California, Berkeley, California, USA, outlining the Nemesis theory.

Related Link

 * Nemesis by Wikipedia