First measurement of a day on a planet outside our solar system.

As a species we have known how long a day is for a long time and since we discovered the planets and figured out we are not the centre of the universe, we have even know how long a day is for the planets in our solar system but how long is a day on another planet in another solar system?

Well, thanks to the European Southern Observatory we have now measured how long a day is on an exoplanet that is over 60 light years away from earth and considering we only discovered one of Pluto’s moons, Kerberos in 2011, this is a huge achievement.

The exoplanet in question is Beta Pictoris b with orbits the star Beta Pictoris and it is approximately 10 times larger than Jupiter and spins at speeds of 100,000km/hr, that’s 60 times faster than earth. So how long is its day I hear you ask? Amazingly its 8 hours long.

Swinburne University of Technology astronomer Dr Alan Duffy says the finding appears to confirm a pattern seen in our Solar System of larger planets spinning faster and therefore having shorter days than smaller planets, but we still don’t know why this occurs.

Artist Depiction of Pictoris-b
Artist Depiction of Pictoris-b (Image credit: ESO/L. Calcada) 

Using the same principle as police speed guns, the astronomers were able to measure the Doppler shift in the colour, or wavelength, of the light from the planet. As one side moved towards us it produced a shorter wavelength or bluer colour, and as the other moved away it stretched out the wavelength producing a redder colour.

Until today we only knew of the rotations of planets in our own Solar System, with larger planets like Jupiter spinning much more quickly than smaller planets like Earth. We didn’t know if this was something strange about our own Solar System, but with this discovery now we know that it’s seemingly the rule. We just don’t know why.

Either way, you look at it this is an amazing achievement by astronomers and we can’t wait to see how much detail can be garnered when a series of new telescopes that are under construction currently go live, like the European Extremely Large Telescope that has a collecting area 1/3 times larger than its biggest predecessor.

Stay Curious – C. Costigan


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