It's hard to get a good distance in space.
It is extremely difficult to work out how far away something is. There is a lot of stuff in the universe that is not well defined.
Sometimes we can get wrong distances. New simulations show that a huge structure may be a lot closer than we thought.
The structure is called the Magellanic Stream, and it is a huge stream of gas.
The material is from the Large and Small Magellanic Clouds, which are satellite dwarf galaxies that will eventually be eaten by the Milky Way.
A large amount of gas has been ripped out by the Clouds' interactions.
There are a lot of things in the sky that are more visible than the Magellanic Stream, so figuring out how it formed has been an ongoing problem. A team of scientists found last year that the gas was likely stripped from the halos of the clouds of gas and plasma that surround most galaxies.
The team has used models from astronomy to model the evolution of the stream over 3.5 billion years and found that it could be five times closer to us than we thought.
Scott Lucchini of the University of Wisconsin-Madison said that the origin of the Magellanic Stream has been a mystery for 50 years.
We came up with a new solution. The models brought the stream closer to the stars.
The team predicted that the Stream should be surrounded by a warm gas. They created a new model for the corona and the clouds that suggest that they have only been in contact with each other for 3 billion years.
The simulations show that when the two dwarf galaxies began to circle each other, they did so in the opposite direction from what they had been thought to be. The Magellanic Stream moved towards our galaxy when they started stripping gas from each other.
It's just 65,000 light-years away from Earth. It was thought to be between 325,000 and 650,000 light-years away. This is a big deal. We need to rethink the Stream's key properties if it is closer than we thought.
Andrew Fox of the Space Telescope Science Institute said that the revised distance changed their understanding of the stream. It means we need to revise our estimates of the stream's properties.
The results show that the gas in the Magellanic Stream is likely to start colliding with the Milky Way sooner than we thought, injecting it with new material and generating shocks that will cause gas to clump together to form new stars. The team's calculations show that this will happen in 50 million years.
Astronomers can now start looking for the stars that should be in the Magellanic Stream. The stars should have been removed from the Clouds along with the gas, but so far only a few have been identified. The model suggests that we've been looking in the wrong place.
Lucchini said it was shifting the paradigm of the stream. Some people think the stars are too far away to see. The stream is at the outer part of the disk.
Future observations of that region could help confirm the findings of the team.
The research was published in a journal.