When you're right in the middle of something, it's pretty hard to tell exactly how big it is.
Like the Milky Way galaxy, for instance. We can't exactly go take a picture of it from the outside, so our best estimates rely on distance measurements to objects on the outskirts.
An estimate based on Gaia mapping data last year gave us a disc diameter of about 260,000 light-years, give or take.
But, just as the Sun's influence extends farther than the Kuiper Belt, the gravitational influence and density of the Milky Way - its invisible dark matter halo - extends farther than the disc.
How much farther? Well, as new calculations have found, quite a bit.
In a new paper submitted to the Monthly Notices of the Royal Astronomical Society and uploaded to arXiv, astrophysicist Alis Deason of Durham University in the UK and colleagues have revealed a diameter of 1.9 million light-years.
There's more to the Milky Way than the stuff we can see - the stars and gas all whirling in orbit around Sagittarius A*, the supermassive black hole at the galactic centre.