EXOPLANETS

“There are more things in heaven and earth, Horatio, Than are dreamt of in your philosophy.” – William Shakespeare; Hamlet, Act 1, Scene 5

It seems recently that we are gazing up at the skies a lot more and we are seeing much more than we have ever seen in the past. New technology of course, is helping with better telescopes, electronics and image enhancers, radio-astronomy, computer modelling, x-ray detection, etc, etc. However we now also have a whole new armamentarium to help astronomers with their investigations. The International Space Station, the Hubble telescope, rockets that carry unmanned exploratory space modules that send back data ceaselessly all contribute to the masses of new information that is available nowadays. And the discoveries are startling, with the “big one” not too far away it seems (the big one of course being extraterrestrial life).

The latest news concerns what astronomers considered before an inconceivable state of affairs. Planets that do not orbit around a star like a sun, but rather wandering hither and thither in deep space. Scientists that have been scanning the heavens for the past two years have found about ten planets with roughly the mass of Jupiter (the largest planet in our solar system with a diameter of 143,000 km), at such huge distances from the nearest star that they seem to float freely through the galaxy! This was published recently in the prestigious scientific journal “Nature” and breaks new ground in the study of “exoplanets” – planets that exist beyond our solar system.

More than 500 exoplanets have been identified since 1995, but this is the first time that discovered planets show such baffling behaviour. The paper suggests that these planets became displaced from their orbit around their sun at a very early stage of the formation of solar systems. There appear to be a lot of these rogue planets, seemingly even more common than main sequence stars.  Numerous questions are now being asked: Did these planets from near a star only to be ejected from its solar system? If they truly have never been bound to any stars, do these planets represent a new planetary formation process, unlike the one that formed our own solar system? Do they represent failed suns that never attracted enough material around them to form solar systems of their own?

To find a planet that is not associated with a star is quite difficult, especially as many of these objects are hundreds of light years away from us. In this latest reported search, a technique called gravitational microlensing was used. Essentially, this is based on the following principle: As you look at a background field of stars, if an object passes between you and one of the stars, there will be a temporary brightening of that star. This occurs as the gravity of the object bends light around itself, which acts as a lens for light from the background star, hence “gravitational lensing”. Microlensing occurs when the foreground object is too small to create measurable distortion of the background star and only a brightening is observed. This makes it an ideal detector for small, dim objects.

The mass of the lensing object determines the duration of the brightening event, with the longer the duration, the more massive being the object. A Jupiter-sized object would produce lensing event with a duration of around one day.  The odds of a microlensing event occurring are exceedingly small, as the lensing object has to line up exactly between the observer and the background star. To compensate for these slim chances, astronomers looked at 50 millions of stars over several years, which yielded 474 microlensing events. Out of those 474, 10 had durations of less than two days, consistent with a Jupiter mass object. No host stars were observed within 10 astronomical units of these lensing objects. Hence the rogue planet discovery…

planet |ˈplanit| noun
A celestial body moving in an elliptical orbit around a star.
• (The planet) the earth: No generation has the right to pollute the planet.
• chiefly Astrology, historical a celestial body distinguished from the fixed stars by having an apparent motion of its own (including the moon and sun), esp. with reference to its supposed influence on people and events.
The nine planets of the solar system are either gas giants—Jupiter, Saturn, Uranus, and Neptune—or smaller rocky bodies—Mercury, Venus, Earth, Mars, and Pluto. The minor planets, or asteroids, orbit mainly between the orbits of Mars and Jupiter.
DERIVATIVES
planetology |ˌplaniˈtäləjē| noun
exoplanet |ˈeksōˌplanit| noun
A planet that orbits a star outside the solar system: Most of the 100 known exoplanets are comparable in mass to Jupiter.

ORIGIN Middle English: From Old French planete, from late Latin planeta, planetes, from Greek planētēs ‘wanderer, planet,’ from planan ‘wander.’