Leo Blitz, a professor of astronomy at the University of California, Berkeley, and his colleagues have charted this warp and analysed it in detail for the first time, based on a new galactic map of hydrogen gas emissions.
The warp, seen most clearly in the thin disk of hydrogen gas permeating the galaxy, extends across the entire 200,000-light year diameter of the Milky Way.
Our sun and the Earth sit somewhere near the crease.
The astronomers found that the atomic gas layer is vibrating like a drum, and that the vibration consists almost entirely of three notes, or modes.
Previously dismissed
Astronomers previously dismissed the Magellanic Clouds as a probable cause of the galactic warp because the galaxies' combined masses are only two per cent that of the disk.
It was thought to be too small to influence such a massive disk, equivalent to about 200 billion suns during the clouds' 1.5 billion-year orbit of the galaxy.
But Martin Weinberg, a professor of astronomy at the University of Massachusetts teamed up with Professor Blitz to create a computer model that takes into account the Milky Way's dark matter.
Although invisible, dark matter is 20 times more massive than all visible matter in the galaxy combined.
When this dark matter is included, in the computer programme, the Magellanic Clouds, in their orbit around the Milky Way, very closely reproduce the type of warp observed in the galaxy.
Flapping in the Breeze
"The model not only produces this warp in the Milky Way, but during the rotation cycle of the Magellanic Clouds around the galaxy, it looks like the Milky Way is flapping in the breeze,” said Professor Blitz.
Professor Weinberg said the simulation was "still not a perfect fit, but it has a lot of the character of the actual data."
The starting point for this research was new spectral data released last summer about hydrogen's 21-centimetre emissions in the Milky Way.
The survey merged a northern sky survey conducted by astronomers in the Netherlands with a southern sky survey from the Argentine Institute of Radioastronomy.
The data were corrected by scientists at the Institute for Radioastronomy of the University of Bonn, Germany.
Meanwhile, astronomers have discovered that a one-way journey from the heart of a galaxy into the oblivion of a black hole probably takes about 200,000 years.
Black holes are drains in space that have gravitational pull so strong that nothing, not even light, escapes.
Huge black holes are believed to lurk at the centre of many galaxies including the Milky Way.
By tracking the death spiral of cosmic gas at the centre of a galaxy called NGC1097, scientists figured that material moving at 177,000 kph would still take hundreds of thousands of years to cross into a black hole.
"It would take 200,000 years for gas to travel the last leg of its one-way journey," Kambiz Fathi of Rochester Institute of Technology told a meeting of the American Astronomical Society.
No one has ever seen a black hole, but astronomers study the way matter and energy behave around them.
An international team led by Mr Fathi studied the black hole at the middle of NGC1097, a behemoth with 100 million times the mass of our sun.
The team managed to observe behaviour, towards the black hole, 10 times closer than ever before, seeing clouds of material within 10 light-years of the galactic core, where the black hole is believed to reside.
Previous research has detected gas clouds from 100 to 1,000 light-years from the galaxy's heart.
A light-year is about 10 trillion kilometres, the distance light travels in a year.
The galaxy NGC1097 is about 47 million light-years away from Earth, relatively close in cosmic terms.