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Astronomers Determine the Length of Day of an Exoplanet
The Bad Astronomer writes: "Astronomers have just announced that the exoplanet Beta Pic b — a 10-Jupiter-mass world 60 light years away — rotates in about 8 hours. Using a high-resolution spectrometer and exploiting the Doppler shift of light seen as the planet spins, they measured its rotation velocity as 28,000 mph. Making reasonable assumptions about the planet's size, that gives the length of its day. This is the first time such a measurement has been achieved for an exoplanet."
I mean, we need to know when to schedule parties.
7 hours in the mountain and central tz.
Fuck systemd. Fuck Redhat. Fuck Soylent, too. Wait, scratch the last one.
Day length can amount to half a year on good old Earth.
It would be measuring whatever is reflecting or generating the light being analyzed. The cloud deck or whatever. The Doppler effect measures velocity, not RPM. The 28,000 is probably the maximum value, so it would be how fast the clouds at the equator are going east. The surface of the Earth rotates at the equator at 1400 mph.
My car gets 40 rods to the hogshead and that's the way I likes it!
You can calculate a lot from this information. From the rotation period and velocity we get a radius of 57,000 km, and an equatorial rotation velocity of 12.5 km/s.
From the mass we get a surface gravity of 389.6 m/s^2 (about 40 g's), but the centrifugal acceleration from rotation is -2.74 m/s^2. Thus the body would not be flattened as much as Jupiter. The density is about 24,500 kg/m^3, higher than Osmium. Iron at the core of a planet is quite compressible, so for a large body such as this, it can give such a high density.
I did not understand one word of what you just said, but it sure sounds important.
Are you sure none of what you just derived wasn't what lead up
to their 28,000 mph in the first place?
On a side note: are universal distances measured in miles?
I think not.
Beta Pic b — a 10-Jupiter-mass world
How is that not a star?
I thought Jupiter was half-way to critical mass where it all explodes into a fireball?
Searching...
Nope. I was wrong. Jupiter would need about 75 times more mass before it went nuclear, fused hydrogen at it's core and became a star. A 10-Jupiter mass planet is totally legit.
I think he was on Beta Pic b, and the rotation was so fast it made him a little dizzy. He meant to post on Deadspin, but it ended up here instead.
I still remember when respectable astronomers were phoo-phooing the idea that we would ever be able to detect planets in other stellar systems. This is incredibly cool. I wonder what we'll know about these systems in another 20 years.
"Think about how stupid the average person is. Now, realise that half of them are dumber than that." - George Carlin
What if the week is 8 days, or 9? Are they working on this?
Planet 'A' rotates once and hour. Planet 'B' likewise. But 'A' is the size of Pluto and 'B' is 10 times the size of Jupiter. One really needs to consider two numbers when comparing rotations of planets - either angular velocity or surface linear velocity at the equator AND the size of said planet.
How does the rotation affect the gravity of a planet?
If the planet is rotating fast enough, does that reduce the force of gravity, or does the gravity still 'squash' you since it is actually affecting the space around it.
For example, if there was a planet with twice the mass of Earth, but spinning twice as fast, what would it be like to stand on the surface?
Do black holes spin? -or are they 'locked in' because the mass would be impossible to move.
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