SCIENCE ALERT

FROM QUARKS TO QUASARS
 



How many of you are aware of the transitional stars that link nuclear firebombs to planets like Jupiter or Saturn? These "brown-dwarfs" (as they are called) are what separates a large planet from a low-mass star like a red-dwarf. Currently, we know of dozens of them, but the number of hot-Jupiter exop

lanets far exceeds those numbers. Now, scientists have made a somewhat baffling discovery.. a large gas-giant that is 13 times more massive than Jupiter, which pretty much defies even our best stellar classification models, some of which, say that any object with ten times the mass of Jupiter is unlikely to be a planet at all.

The parent star of this planet lies only about 168 light-years from Earth in the constellation (not galaxy) of Andromeda. Kappa Andromedae (or just "Kappa And" if you dislike formal names) is a very bright baby star that is only 30 million years old (in comparison, our sun is a middle aged star that's about 5 billion years old) and it now holds the record for the most massive star known to have an orbiting planet that can be imaged directly! (which is a feat in and of itself!) The planet lies about 55 AU's from its parent star (1 AU is the distance that separates the sun and Earth), which is about 1.8 times as far as Neptune. Surprisingly, it's pretty hot. The temperature is estimated to be around 2,000 degrees F (1,400 degrees C) and if you were observing the planet from close-by, it would look bright red to human eyes.

More interestingly, this object straddles the dividing line between a planet and a brown-dwarf so closely, astronomers are having a difficult time trying to decide which category it fits into, therefore, it is currently being inserted into a category all of its own, a "super-Jupiter." As I mentioned before, brown-dwarfs are the link between massive planets and low-mass stars. You have likely heard them being referred to as "failed stars." Astronomers use this term since most of these objects are much more massive than the typical gas-giant planet, but not quite massive enough to sustain the process of hydrogen to helium fusion in its core.

Massive planets such as Kappa And b spend most of their lives radiating left over energy from their formation, which gives them star-like attributes. For example, the most massive planet in our solar system, Jupiter -- gives off over twice the amount of energy it receives from the sun, though more massive objects (like brown-dwarfs) can internally generate large amounts of energy by fusing a particular form of hydrogen known as deuterium into Helium-4. The amount of deuterium burnt depends on the composition of the object (specifically, it depends on the amount of deuterium, helium and some of the heavier elements present in the object's core) The theoretical line that separates the current upper mass limit of a planet before being classified as a brown dwarf is about the mass of 13 Jupiter-sized bodies; while the line separating a brown-dwarf from a red-dwarf is around 75 Jupiter masses.

Though quite large, it is still very difficult to observe these objects because unlike typical stars, they emit no light on the visible part of the spectrum. They can typically only be detected in infrared and even then, the detection process is tedious and grueling. This discovery will ultimately send astronomers back to the drawing board, trying to form a more precise planetary formation model. This will hopefully help us better understand both high-mass planets and low-mass brown-dwarfs.

.-- Jaime