Planets are formed in protoplanetary disks, but they form at a rapid pace. We had observed protoplanetary disks as old as 10 million years, but now it has been discovered one with 25 million years of life; as astronomer L. Hartmann says: "Finding this disk is as unexpected as locating a 200-year-old person". It's possible that this proplyd will never form planets http://www.universetoday.com/am/publish/25_million_years_dust_disk_form_planets.html?1972005
Interesting. I do not know how many protoplanetary disks have been found so far. The number is not large and statistically we should expect the odd extreme. In this case I wonder about the fact that "the disk in question orbits a pair of red dwarf stars". I would anticipate that disk life increases with a decrease in the size of the parent star. That would be consistent with these being red dwarfs. However, do the protplanetary disks discovered to date show any such correlation between spectral class and disk life? The presence of a binary system, rather than a single star, will surely have an effect on the formation and evolution of the disk. Agianm I wonder how many protoplanetary disks have been found around binary systems and does there appear to be any correlation between single v binary and disk age.
i don't know either, but here's a list of protoplanetary disks (14) http://www.extrasolar.net/starlisttour.asp?StarcatID=proto
Here's an article of 1994 that mentions 56 protoplanetary disks. I suppose that the number as of today has increased substantially http://hubblesite.org/newscenter/newsdesk/archive/releases/1994/24/text/