It was discovered in the 1980s. That means something nearby must be emitting IR, and the most common source of that is dust. Vega is also a young star, and young stars commonly have disks or clouds of material around them. Vega is too young to have completely swept away its cocoon. The problem is the movie had too much dust around Vega.
Measurements show that the total amount of dust is about one-half the mass of the Moon.
To be fair, that mass would be in the form of dust, and there might be bigger particles that we haven't detected. But that wouldn't add up to much. I remember an undergrad class I had shortly after the dust cloud was discovered. My poor primitive computer could barely work out the number, but I was shocked to find out it was less than the mass of the Moon. My vision of planets circling a nearby star were dashed.