Are you the type of person who gets dizzy just watching a
merry-go-round go round and round? If so, don't plan a visit
to the planet known as Beta Pictoris b. The thing spins like
Scientists have for the first time measured the spin of a
planet outside our solar system - a large gas planet located
a relatively close 63 light years from Earth.
They determined that the planet spins faster than any in our
solar system, with a rotational velocity at its equator of
Jupiter, a large gas planet that has the quickest spin in our
solar system, whirls at about 47,000kmh while Earth spins at
about 1700kmh. A day on Beta Pictoris b lasts only
eight hours, compared to 10 hours for Jupiter and 24 hours
Scientists have spotted about 1800 planets beyond our solar
system, but very little is known about these distant worlds
including the basics like what they are made of and how they
travel around their stars.
Beta Pictoris b is one of the better understood of these
planets. It is one of only about a dozen that have been
directly observed rather than found using indirect detection
methods in which scientists can only see the planet's
influence on the host star.
"Only if we know more about other planets - like
temperatures, atmosphere and rotation - can we tell how
unique our home in the universe really is," said one of the
researchers, Bernhard Brandl, an astronomy professor at the
University of Leiden in the Netherlands.
Beta Pictoris b is big, hot and young. It is about 3000 times
more massive than Earth and seven times more massive than
Jupiter, our solar system's largest planet. It is only about
20 million years old, compared to about 4.5 billion years for
Earth, and is still hot from its formation, the scientists
Its host star, Beta Pictoris, is approximately twice as
massive and 10 times as luminous as our Sun.
The head-spinning speed at which Beta Pictoris b whirls, the
scientists said, lends support to the notion that a planet's
rotational velocity is closely related to its size: the
bigger, the faster.
"Yes, the relation between mass and spin velocity was already
known in our solar system," said University of Leiden
astronomy professor Ignas Snellen, another of the
"We now extend it to a more massive planet to see that the
relation still holds. We need to observe more planets to
confirm this is really a universal law," Snellen added.
The technique the scientists used to measure the planet's
spin was based on the Doppler effect, the well-known
phenomenon people notice when they hear a change in the pitch
of an ambulance siren when the vehicle whizzes by.
"When we observe a rotating planet, the light from one half,
which is approaching us, has a slightly different frequency,
or color, than the other half, which is receding from us. The
relative difference in color, or frequency, between the two
halves is a measure of the spin-rotation velocity," Brandl
Beta Pictoris b is located in the southern constellation of
Pictor and was discovered about six years ago. It orbits
eight times farther from its host star than Earth orbits the
The scientists are hoping in the future to make a global map
of it including possible cloud patterns and storms.
The research was published in the journal Nature.