Friday, April 30, 2010

Discovering Tyche

Is there an undiscovered massive object orbiting the Sun in the Oort Cloud, elusively hidden in the perpetual frigid darkness? The Oort Cloud occupies an immense region of space surrounding the Sun; from a couple of thousand AU to as far as 50000 AU from the Sun! The term AU is the acronym for Astronomical Unit, where one AU is the mean distance of the Earth from the Sun and it has a value of 149.6 million kilometers.

The Oort Cloud is estimated to contain several trillion objects larger than 1 kilometer in diameter, with each object spaced tens of millions of kilometers away from its closest neighbor! To put the size of the Oort Cloud into perspective, even the distance of Pluto from the Sun is less than 0.1 percent the distance to the edge of the Oort Cloud!

A paper by John J. Matese and Daniel P. Whitmire (2010) entitled “Persistent Evidence of a Jovian Mass Solar Companion in the Oort Cloud” describes the possibilities of a Jupiter-mass object orbiting the Sun at a distance large enough to place it within the Oort Cloud. Tyche is the name that has been suggested for this hypothetical object. The name Tyche, which means “luck” in Greek, is also the good sister of Nemesis in Greek mythology.

In this paper, the possible existence of Tyche was inferred from dynamical and statistical analysis of the orbits of comets entering the Solar System from the Oort Cloud. The gravitational perturbations from a distant Jupiter-mass object like Tyche could also explain the peculiar orbits of extended scattered disc objects such as Sedna. These objects orbit the Sun on highly elliptical orbits that take them out to hundreds of AU from the Sun. Sedna for example, has a very elongated orbit which takes it from a minimum of 76 AU from the Sun out to an incredible 976 AU from the Sun and it takes over 12 thousand years to orbit the Sun once.

Being located at such a huge distance from the Sun, the amount of insolation that Tyche gets from the Sun will be negligible. Tyche will be a gas giant world like Jupiter and it is expected to glow feebly at a temperature of about 200 Kelvin from heat emanating from its warm interior. Therefore, Tyche can only be detected in the infrared band since such a cool object is expected to emit almost no visible light. Interestingly, NASA’s recently launched Wide-field Infrared Survey Explorer (WISE) will be able to easily detect the presence of such an object in the Oort Cloud! Visit to find out more about WISE.

Although a positive detection of Tyche might not be much of a surprise, the discovery of such a world will be extremely fascinating. Jupiter is currently by far the most massive known object in orbit around the Sun and the discovery of something more massive than Jupiter will have interesting implication regarding our perspectives of things in orbit around the Sun. What kind of moons will orbit this object and might some of these moons be similar to the ones in orbit around Jupiter? What kind of exploratory robotic spacecraft might possibly be sent there? Additionally, since the formation mechanisms for such an object are probably be very different compared to the formation mechanisms for the planets in our Solar System, should Tyche be classified as a planet or a brown dwarf?