Level 1 — Absolute Beginner
Our galaxy is called the Milky Way. It is a huge group of stars, and our sun is one of them.
Scientists made new computer models of the Milky Way's past. The models show something surprising.
A very long time ago, a smaller galaxy crashed into the Milky Way. This crash may have made the Milky Way flip on its side.
Scientists say the Milky Way's flat disk of stars tipped more than 90 degrees because of this old crash.
- galaxy
- a huge group of stars, gas, and dust held together by gravity
- Milky Way
- the galaxy that contains our sun and solar system
- scientist
- a person who studies and learns about the natural world
- model
- a computer program that copies how something in nature works
- crash
- a violent collision between two objects
- flip
- to turn something over or to one side
- disk
- a flat, round shape
- degree
- a unit used to measure how much something turns or tips
Level 2 — Elementary
Astronomers have new evidence that our home galaxy, the Milky Way, once experienced a dramatic transformation billions of years ago. New computer simulations suggest its flat, star-filled disk tipped more than 90 degrees after a head-on collision with a smaller galaxy.
That smaller galaxy is known as the Gaia-Sausage-Enceladus, a dwarf galaxy that crashed into and was absorbed by the young Milky Way roughly 10 to 11 billion years ago. Scientists consider it one of the most important events in our galaxy's early history.
Researcher Kirill Batrakov of Durham University presented the simulation results at the Royal Astronomical Society's National Astronomy Meeting, showing how the Milky Way's disk may have gradually tilted onto its side over billions of years following the impact.
The findings gain extra credibility because they match an earlier, independent study published in February 2026 that reached a similar conclusion using a completely different method: measuring the three-dimensional shape of the Milky Way's dark matter halo using data from more than 600,000 stars.
- transformation
- a major change in the form or structure of something
- simulation
- a computer-based imitation of a real process, used to study how it works
- dwarf galaxy
- a small galaxy with far fewer stars than a large galaxy like the Milky Way
- absorb
- to take in and combine with something else
- tilt
- to lean or slope from a level position
- credibility
- the quality of being believable or trustworthy
- independent study
- research carried out separately from another study, without relying on its methods
- dark matter halo
- a large, invisible region of mass surrounding a galaxy that can only be detected through its gravity
Level 3 — Intermediate
New simulation work presented at the Royal Astronomical Society's 2026 National Astronomy Meeting offers striking evidence that the Milky Way's galactic disk underwent a far more violent transformation in its early history than previously assumed, tilting more than 90 degrees relative to its current orientation following a head-on collision billions of years ago.
Durham University astronomer Kirill Batrakov's simulations trace the disruption to the Gaia-Sausage-Enceladus, a dwarf galaxy whose merger with the still-forming Milky Way roughly 10 to 11 billion years ago is already recognized as one of the most consequential events in the galaxy's assembly history. The new work models how such a collision could have imparted enough angular momentum to progressively reorient the disk over a span of billions of years, rather than in a single abrupt event.
What lends the finding particular weight is its convergence with an entirely independent line of evidence: a peer-reviewed study published in Astronomy & Astrophysics in February 2026 arrived at a comparable conclusion using six-dimensional positional and velocity data gathered from more than 600,000 giant stars observed by the LAMOST telescope and the European Space Agency's Gaia mission, reconstructing the three-dimensional shape of the galaxy's dark matter halo rather than simulating the disk's history directly.
Two methodologically unrelated approaches, one built on dynamical simulation and the other on direct observational reconstruction, converging on the same picture of a dramatically reoriented disk substantially strengthens confidence that the Milky Way's structural history is more turbulent than the relatively settled spiral galaxy visible in the night sky might suggest.
- orientation
- the position or direction something faces relative to a fixed reference
- merger
- the combining of two separate galaxies (or objects) into one
- angular momentum
- a physical quantity describing the rotational motion of an object
- reorient
- to change the direction or position something faces
- convergence
- the coming together of separate lines of evidence toward the same conclusion
- methodologically
- relating to the specific methods or techniques used in research
- dynamical simulation
- a computer model that calculates how a physical system changes and moves over time
- turbulent
- marked by violent or disordered change
Level 4 — Advanced
The presentation of new dynamical simulations at the Royal Astronomical Society's 2026 National Astronomy Meeting adds a further, methodologically distinct line of evidence to a growing body of work suggesting that the Milky Way's galactic disk underwent a structural transformation far more dramatic than its current, relatively settled spiral morphology would suggest, tilting more than 90 degrees from its ancient orientation.
Kirill Batrakov's modeling attributes this reorientation to the merger of the Gaia-Sausage-Enceladus, a dwarf galaxy whose absorption into the still-assembling Milky Way roughly 10 to 11 billion years ago already ranks among the most consequential events in the galaxy's formation history, proposing that the collision imparted sufficient angular momentum to progressively, rather than instantaneously, reorient the disk over a timescale spanning billions of years.
The finding's evidentiary weight derives less from the simulation itself than from its convergence with an entirely independent methodology: a February 2026 study published in Astronomy & Astrophysics reconstructed the three-dimensional geometry of the galaxy's dark matter halo directly from six-dimensional phase-space data, positions and velocities, drawn from more than 600,000 giant stars observed jointly by the LAMOST spectroscopic survey and the European Space Agency's Gaia astrometric mission, arriving independently at a comparable picture of a dramatically reoriented disk.
That two approaches so methodologically unrelated, one a forward dynamical simulation of a hypothesized collision, the other a direct observational reconstruction of present-day stellar kinematics, converge on a substantially similar conclusion constitutes a considerably stronger form of corroboration than either result could offer in isolation, and reframes the Milky Way's structural history as one shaped by episodes of violent disruption rather than the quiescent, steady evolution its present appearance might otherwise imply.
- morphology
- the form, shape, or structure of something, especially in science
- evidentiary weight
- the degree to which evidence supports a conclusion
- phase-space data
- data describing both the position and velocity (motion) of objects in a system
- astrometric
- relating to the precise measurement of the positions and movements of stars and other celestial objects
- kinematics
- the branch of physics or study describing motion without regard to its causes
- corroboration
- independent confirmation or support for a claim or finding
- quiescent
- inactive or in a state of rest, showing no significant change
- reframe
- to present or interpret something from a new perspective
Talk about this article with KatePractice this story's vocabulary in a real spoken conversation with your AI tutor