## Kepler Spots "Perfectly Aligned" Alien Worlds 73

astroengine writes

*"When NASA's Kepler space telescope started finding planets at odd angles to their parent stars, scientists wondered if our solar system's tidy geometry, with the planets neatly orbiting around the sun's equator, was an exception to the rule. That idea can be laid to rest thanks to an innovative use of the Kepler data which aligned three planets circling the sun-like star Kepler-30 with a giant spot on the star's surface. 'The planets themselves are not all that remarkable — two giant Jupiters and one super-Earth — but what is remarkable is that they aligned so perfectly,' astronomer Drake Deming, with the University of Maryland, told Discovery News."*
## I'd have assumed... (Score:2)

## Re:I'd have assumed... (Score:5, Informative)

I'm a software engineer so my knowledge is rather limited, but I'd have assumed that the orbits of planets would tend to be in the same plane as the spinning of the galaxy, so if you look at a mostly flat galaxy, you'll find mostly aligned orbits, and if a galaxy was more... "chaotic", the orbits would be likewise less aligned in respect with each other.

Well, each solar system has an invariable plane [wikipedia.org] perpendicular to its aggregate angular momentum vector. The rotation of the star and the orbits of the planets tend to be quite close to this plane. The exception is when the orbits have been perturbed by passage of an object of significant mass at an angle to the plane. Note that the invariable plane of any particular solar system in a galaxy is not necessarily similar to that of the galaxy as a whole, although aggregated over all solar systems in the galaxy they are the same.

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I think it's indeed an extension of the phenomenon you can see happening in those toy 2d simulators of gravity of stars and planets: start with a chaotic configuration, let it evolve for some time, and see how the stuff often evolves in one big central blob with possibly some circular orbits and short lived elliptical ones

## Re:I'd have assumed... (Score:5, Informative)

> those toy 2d simulators of gravity of stars and planets: start with a chaotic configuration, let it evolve for some time, and see how the stuff often evolves in one big central blob with possibly some circular orbits and short lived elliptical ones

The technical term is called

N-Bodysimulation/problem and is impossible to solve an exact solution with our current mathematics and computers where N > 3.http://en.wikipedia.org/wiki/N-body_simulation [wikipedia.org]

http://en.wikipedia.org/wiki/N-body_problem [wikipedia.org]

I found one demo here ...

http://michael.peopleofhonoronly.com/dev/nbody.html [peopleofhonoronly.com]

In order for the simulator to work properly, every simulator has to use a hack: gravity has infinite speed, which contradicts the mainstream assumption that gravity is limited to the speed of light.

Another anomaly is that the the galaxy "seems" to rotate in lock-step.

http://en.wikipedia.org/wiki/Galaxy_rotation_curve [wikipedia.org]

It "appears" the orbits of the planets also seem to be quantized.

Celestial Mechanics is not going to be "solved" anytime soon.

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Q for a physic-y person - The earth orbits around the sun's equator, but its own equator is at an angle to the sun-planet plane (hence, seasons). Does the moon, then orbit around earth's equator (at an angle to the sun), or in the sam

## Re:I'd have assumed... (Score:5, Informative)

Disclaimer: IAAAA (I am an amateur astronomer).

The moon orbits at a mean inclination of 5.something degrees to the ecliptic. If it were synchronised to the equatorial plane we wouldn't have nearly as many eclipses (lunar or solar) as we do. In fact, we'd have about 1/50 the number.

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Can you explain why. Like a lot of things in life it seems to go against what one would think. For example, the transit of Venus occurs twice about every 120 years, I would have thought the transit would occur 1.6 times a year (365 / 225), if our orbits were in the same plane.

## Re:I'd have assumed... (Score:5, Informative)

Actually, I can.

Even assuming that the orbital inclination of both planets were identical, those orbits undergo what's known as apsidal precession. This is the movement of apoapsis (the furthest point of the orbit) around the primary over time - the orbit orbits. For Earth this varies between 100,000-400,000 years, and is tidally dependent. Ergo, the relative angle of inclination between planets changes and while Earth is below the ecliptic, the orbit of Venus at that point, even if the planet was in the same orbital position (ie between Earth and Sol), may be above the ecliptic hence no transit occurs.

This also happens with the Moon. Fortunately the systems are stable enough that we can predict when transits and eclipses will occur by concentrating only on dates and times where ascending and descending nodes of their orbits intersect the ecliptic. The great thing about the Moon is that it crosses the ecliptic exactly twenty six times per year, so we can predict with reasonable certainty from the off that solar and lunar eclipse patterns will repeat with fair precision every 6585 days, or every 223 Lunar orbits. (approximately 18 years).

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addendum: think of a toy gyro. When you spin it, the pole (axis) starts to describe a circle in the air. Ignore that bit, look at the plane of the gyro - the edge represents the orbital plane relative to a fixed point in space (your eye). It is not only spinning, it is also describing an oscillation such that a fixed point in its orbit is moving in a sinusoidal motion. The wider the gyro, the slower this oscillation, but it is there.

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Q for a physic-y person - The earth orbits around the sun's equator, but its own equator is at an angle to the sun-planet plane (hence, seasons). Does the moon, then orbit around earth's equator (at an angle to the sun), or in the same plane as the sun's equator (or some other plane entirely)?

Along with the above answer to your question, I will also mention that Luna is the

onlysizable moon in the entire Solar System whose orbit is more closely aligned to the ecliptic than to the parent planet's equator.## Re:I'd have assumed... (Score:4, Informative)

Q for a physic-y person - The earth orbits around the sun's equator, but its own equator is at an angle to the sun-planet plane (hence, seasons). Does the moon, then orbit around earth's equator (at an angle to the sun), or in the same plane as the sun's equator (or some other plane entirely)?

First things first. There is no actual link between the equator of a body, and the orbits of the satellites of that body. The rotation of the planet, its orbital plane, the rotation of any moons or satellites of that planet, and the orbital planes of those moons are all independent from each other.

Now, having said that, if a satellite formed by being spun off of a quickly rotating object, or if both the satellite and the planet both coalesced from the same rotating blob of matter, then there will be a tendency for the satellite to be in the equatorial plane. However, once the satellite is no longer physically connected, the orbital plane or the planetary axis can both shift independently of each other (through perturbations from other bodies). If a satellite was formed by an asteroid collision knocking the planet apart, then there may be some relationship between the planet's original spin and the satellite's orbit. However, it also greatly depends on the speed and angle that the asteroid hit the planet with, and of course, the collision could drastically change the axis of rotation of the planet. If a satellite was captured by the planet's gravity, it could be in any orbital plane, and could even orbit completely opposite to the direction of rotation of the planet.

It takes a lot of energy to alter an orbital plane. So, just like the Earth spins and its axis is fixed in space, (pointing towards Polaris), so too the Earth's orbit is fixed in space. We call this the ecliptic. The ecliptic is inclined roughly 23.5 degrees from the plane of the Earth's equator. The equatorial plane of the sun is inclined roughly 7 degrees from the ecliptic. The plane of the lunar orbit is inclined at about 5 degrees from the ecliptic. Saturn's rings are along it's equator, and they are tipped 26.7 degrees. Uranus has its axis almost in the plane of the ecliptic at an inclination of 97 degrees. Venus's north pole is pointing south relative to ours (177.4 degrees).

Of course, having said all that, there may be tidal effects and relativistic effects that a spinning gravity well may impart on a satellite to coax it into the equatorial plane.

## Re:I'd have assumed... (Score:5, Informative)

I'd have assumed that the orbits of planets would tend to be in the same plane as the spinning of the galaxy

If you consider that the Milky Way is not aligned with the ecliptic [wikipedia.org] then you should see that the assumption is erroneous with respect to the only solar system we understand well.

## Re: (Score:2, Interesting)

It doesn't have anything to do with the spinning of the galaxy. Our ecliptic plane is not the same as that for the galaxy (60 degrees off).

When a nebula collapses, there will be areas of lower and higher densities. Eventually this will impart an angular momentum. The rotation flattens out the protoplanetary disk [wikipedia.org]. Thus retrograde rotation or anything out of the ecliptic is very odd (such as the dwarf planet Pluto) and probably needs to be explained by events outside of the initial formation of the system.

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no, it's more like the tip of a helicopter rotor at extreme velocities - rather than describe complete ellipses through space, as they would if they were flat onto the plane of travel, they describe a sort of mutant helix, with a cutting angle of about 60 degrees - so for part of its orbit, the Earth is actually travelling in the opposite direction in relation to the cosmic microwave background to the Sun. At one point during its orbit, the Earth actually slows down.

## Statistics anyone ? (Score:1)

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Woah, that's trippy.

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What if... C-A-T really spelled dog?

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What if C-A-Ts really taste like tasty wheat?

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The null hypothesis would say that planets could orbit the star in any method. To reject it you would have to calculate the probability that 3 separate planets would have an orbit that would allow them to cross over the same sunspot. The probability isn't high, and 3 planets might be enough data to answer it with statistical significance. I'm not claiming to say that it is or not (it would be a pain in the ass physics problem). All that I'm saying is that the data could very well be the equivalent to rolli

## mind-job, anyone? (Score:1)

if the universe is infinite, then there are an infinite number of stars. It follows that orbiting those infinite stars is an infinite number of planets. HOWEVER, and here's the paradox: if not all stars have orbiting planets, then the number of stars with orbiting planets is less than infinite, ie, finite. There are two countering assumptions right there: there is an infinite number of planets in the universe, there is a finite number of planets in the universe.

Statistically speaking, this is significant, a

## Re:mind-job, anyone? (Score:5, Informative)

HOWEVER, and here's the paradox: if not all stars have orbiting planets, then the number of stars with orbiting planets is less than infinite, ie, finite.

Bzzzt! Fail - thanks for playing.

Once you start playing with infinite numbers you have to be very careful with concepts like "less than" or "more than". Just because you can demonstrate that one set is in some way smaller than another infinite set does *not* demonstrate that the smaller one is finite.

Consider the set of natural numbers - 1,2,3,4 etc. This is infinite. Then consider the set of even natural numbers - 2,4,6,8 etc. Clearly there are members of the first set which are not members of the second set, and so one might be tempted to conclude that the second set is in some way smaller, and therefore by your argument, finite.

In fact one can set up a one-to-one mapping between the two sets:

12

24

36

etc. and thus both sets have precisely the same (infinite) number of members.

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No, but we can set up a fraction. Let's say that 1/1000 stars have orbiting planets. That would be infinity/1000, which equals infinity. Still not finite. As another commenter noted, there is a one-to-one mapping of rational numbers (3/4, 1/72, 399/12, etc.) to integers.

Or, as my sig used to say, "Space is big - really big. Better pack a lunch."

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Actually you don't. At least not if you are starting from the assumption that there are infinite stars in the first place. No matter what the process is that results in flat star systems SOMETHING caused it, that something has a probability of occurring, all probabilities can be represented as a fraction of the sample set since in this case your sample set is infinity stars and any fraction of infinity is also infinity you don't have to actually know the probability of occurrence.

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## Re:mind-job, anyone? (Score:4, Informative)

Once you start playing with infinite numbers you have to be very careful with concepts like "less than" or "more than".

Numberphile has a nice video about different types of infinity: http://www.numberphile.com/videos/countable_infinity.html [numberphile.com]

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I'm not really sure why people have trouble with any of that. All of it seems like a logical given if one accepts infinity as a valid concept in the first place.

Accepting that an infinity exists in the physical universe is the challenging part.

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I found that the easiest way for them to grasp the difference between countable and uncountable infinities is the difference between whole numbers and real numbers. A countable infinity will always have a finite number of elements between any two elements (whole numbers) where as an uncountable infinity will have an infinite number of elements between any to elements in the set (real numbers).

This is severely misleading, as there are an infinite number of elements between any two rational numbers, yet the rational numbers are still countably infinite.

If you really want to explain it correctly, then the best way is talk about one-to-one correspondence. Having a one-to-one correspondence with the natural numbers is what it means to be countably infinite, and has a direct analogy to people counting with their fingers. Cantor's diagonalization argument shows why you can't count the reals, or more t

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it would be extremely improbable that the only other flat system would be so close to earth.

so your authority wouldn't be the same in casual observers view.

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if the universe is infinite, then there are an infinite number of stars. It follows that orbiting those infinite stars is an infinite number of planets.

"Would you like a cheese and ham Breville?"

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love one.

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It makes perfect sense in the realm of popular statistics... thousands of reports come out saying smoking/chocolate/coffee/alcohol/etc is bad for you. Then one comes out saying that there are some positive aspects of <product>, and the world thinks "Ah. So <product> is not so bad for you after all!".

Still... in the scale of the galaxy, spotting another such system in the galaxy proves that earth isn't the _only_ one, and the chance that we've seen the only other well-aligned solar system in the

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this is a piss-take

Yes, an utterly pathetic one. The kind of witless yammering you'd expect from a 14 year old.

I'm no fan of religion, but this kind of empty sneering does nothing to promote the adoption of reason.

## sour grapes (Score:1)

## Re:sour grapes (Score:5, Funny)

## Next step: invasion (Score:2)

we'll show those blue freaks that unobtainium isn't fer plantin' trees on!

## We all know (Score:5, Funny)

Universe is 2D.

The 3D stuff is just to milk more money!

## puppeteers (Score:2)

Where's Larry Niven's Kemplerer rosette in known space when you need it .....

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## Less exciting than it could have been. (Score:3)

The planets are merely aligned in the same plane - and not perfectly.

When I first read the headline, I was expecting to read about a ring of planets sharing the same orbit - what would be equivalent to the first stage of maneuver for the development of a niven ring or even a dyson sphere. Now that would have been exciting news.

## Still don't get the cellophane 'S' tho. (Score:1)

> innovative use of the Kepler data which aligned three planets...

Well, in Superman III, we learned weather satellites could be used to control the weather, so why couldn't astronomy satellites be used to align planets?

## Summary (Score:1)

I am still trying to make sense of the summary...

The 3 planets are aligned perfectly with what? A spot on the surface of the star?

(Maybe thats the shadow of another (very close in) planet).

Reads on further

"but what is remarkable is that they aligned so perfectly,' astronomer Drake Deming, with the University of Maryland,"

So the planets are aligned with the University of Maryland ?

Generaly the planets of our solar system are on the same plane as each other - except for Pluto, and that was kicked out for its

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## Rotating disk of gas? (Score:2)

The alignment does not prove they were formed from a rotating disk of gas. Planets in stable orbits around a sun with great tilts will gradually shift their orbits to nearly a common plane. This is caused by their own gravity affecting each other. How fast it happens depends on things like locations of larger planets and orbital timings. Note that while this is happening, their own rotational angle does not change. So the net result is planets with rotation planes not in alignment with orbit planes. T

## Selection bias, anthropic principle (Score:2)

Any scientist wondering this should probably look up the terms

selection biasandanthropic principle,and stop calling himself a "scientist."