Why does Earth’s orbit tilt? Scientists finally think they know

By | November 21, 2012

Why does Earth's orbit tilt? Scientists finally think they know

It’s an enduring puzzle that’s had astronomers and astrophysicists scratching their heads for years: Why does the Earth tilt? Our planet orbits with a slight (7-degree) angle relative to the sun, and we’ve never been able to figure out why, but now one scientist thinks he’s got our planet’s crooked spin solved.

When astronomers discovered a “hot Jupiter,” a gas giant planet orbiting very close to its star, in 1995, they were baffled. Gas giants don’t normally behave that way (or so they thought), so to explain this hot Jupiter’s proximity to its star the theory of “disk migration” was developed. The theory goes that planets form farther away from their stars but then migrate inward until they reach the protoplanetary disk of gases surrounding the star. Once inside the disk, the planet begins to match the star’s orbit.

But that theory was called into question four years ago when astronomers began discovering more hot Jupiters that were just as close to their stars but orbiting in very different ways. These planets orbited at odd angles, and some even orbited backward relative to their stars. Clearly the disk migration theory wasn’t making sense anymore.

Some astronomers explained these oddly tilted orbits as the result of other planets pushing the hot Jupiters toward their stars, but Konstantin Batygin of the Harvard-Smithsonian Center for Astrophysics has a different idea.

“Misaligned orbits are actually a natural outcome of disk migration–once you take into account the fact that planetary systems are usually born in multistellar environments,” Batygin said.

If a planet is born in a system with two stars, the second star can cause it to spiral in and tilt. The second star might eventually migrate away, but the orbit of the planet stays the same. According to Batygin, that’s what happened to Earth.

“I think somewhere in the Milky Way, there’s a star that’s responsible for tilting us,” he said.

Batygin’s theory seems sound, but it still has to be tested, and Batygin hopes to confirm it with measurements of a system that still has multiple stars: Alpha Centauri. By measuring the alignments of each of Alpha Centauri’s three stars, Batygin hopes to confirm that neighboring stars can tilt each other’s protoplanetary disks, which would in turn affect the orbits of any planets in the area.

There’s a good chance that astronomers will find misalignment in the Alpha Centauri system,” he said.

So, if Batygin is right, he’s just solved yet another of Earth’s cosmic mysteries.

(Via Huffington Post)

via Why does Earth’s orbit tilt? Scientists finally think they know | Blastr.

Related… it’s not just the Earth that is tilted, it is the entire solar system. Space is a mess.

Have you ever looked at the sky at night and found the famous band of stars called the Milky Way? Probably, but did you notice it’s tilted at an angle? Well, this thing really puzzled astronomers for quite some time.

That’s because what you saw is actually our galaxy itself, seen from the side. The classical maps of the galaxy place our solar system in one of the spiral arms of the Milky Way galaxy. However, we ought to be oriented to the galaxy’s ecliptic, with the planets aligned around our Sun in much the same angle as our Sun aligns with the Milky Way.

Now, a team of astronomers at universities of Virginia and Massachusetts used a supercomputer to come up with a strange answer to the question: why are we tilted in the galaxy?

Our solar system comes from another galaxy!

They used volumes of data from the Two-Micron All Sky Survey (2MASS), a major project to survey the sky in infrared light led by the University of Massachusetts and discovered that our galaxy is in fact cannibalizing a smaller neighbor, the Sagittarius Dwarf galaxy.

Although it is one of the closest companion galaxies to the Milky Way, the main parent cluster is on the opposite side of the galactic core from Earth and consequently is very faint, although it covers a large area of the sky.

Milky Way is currently absorbing the dwarf galaxy, 10,000 times smaller in mass, which is getting stretched out, torn apart and gobbled up by our bigger galaxy. The stars in the Sagittarius form a cosmic spaghetti noodle wrapping itself around the Milky Way.

The really big news is the fact that our solar system is located at the exact nexus crossroads where two galaxies are actually joining. This would explain the odd angle at which we see the Milky Way in the sky, at night, meaning that our Sun is influenced by some other system.

This could mean that our solar system could in fact have come from the Sagittarius Dwarf galaxy.

“This first full-sky map of Sagittarius shows its extensive interaction with the Milky Way,” said Steven Majewski, University of Virginia professor of astronomy and lead author on the paper describing the results. “Both stars and star clusters now in the outer parts of the Milky Way have been ‘stolen’ from Sagittarius as the gravitational forces of the Milky Way nibbled away at its dwarf companion. This one vivid example shows that the Milky Way grows by eating its smaller neighbors.”

So it seems we don’t have to look for aliens anymore, since we are aliens to this galaxy ourselves.

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