Stars go missing

The BBC has an article by Melissa Hogenboom about some missing stars:

Look at the video above, and watch it to the end. Notice something strange?
In a certain part of the universe, all the stars seem to have disappeared into a black void.
The new imagery was captured by the European Southern Observatory (ESO) from the La Silla Observatory in Chile.
The black void it turns out, is actually a star nursery, a huge cloud of gas and stardust in which new stars are forming from the remnants of previously dead ones, giants that died as exploding supernovae. The cloud is so dense, it completely blocks out any light emanating from the stars behind, giving the appearance of being empty space. This area is some seven hundred light-years away, in a constellation named Serpens in the Northern hemisphere, first classified by the Greek astronomer Ptolemy almost two thousand years ago.
The clouds pictured have their own name too, LDN 483 (Lynds Dark Nebula) and this dark nebula is a perfect location for the birth of these baby stars. These forming stars are between several hundred thousand to a few million years old, explains Fernando Comeron, ESO's Chilean representative. This is "basically nothing" when considering the full length of a star's life, he says. "It's like watching a human just hours after being born, it's just a baby." That they are more than just black voids, he adds, is verified when looking at the infrared wavelengths observed through the obscuring dust. "In the vast majority of such clouds, one finds star formation at work."
To put this in context, stars are known to live for hundreds of millions or even several billion years; indeed our own Sun is already nearly five billion years-old. And it is only in the last few decades that advances in technology have enabled researchers to probe inside such clouds. By doing so, they can answer key questions about how the Universe has changed since its formation.
For one, stars were not yet present shortly after its formation, something the Plank satellite has recently confirmed in astonishing detail.  The early Universe was thererfore a very different place than it is today, says Andrew Pontzen of University College London in the UK. Key questions remain for cosmologists such as Pontzen: how did all these stars form, how did our Universe become the one we know today where we have clumps of galaxies with hundreds of billions of stars in them? We can't quite answer these questions, but that's why it's so important to study the stars being born nearby, he says. It will still take many millions of years before the young stars in this particular part of cloud become bright enough to shine through. 

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