article_snippet: It's a problem that has perplexed scientists, but now a study claims to have an answer, saying that the heat in star-forming clouds may be hindering stellar formation.
article_snippet: the heat in star-forming clouds may be hindering stellar formation say that the temperatures are likely too hot to allow reasonable amounts of star formation, which leads to the observed lower number of stars we see in the cosmos today.
article_snippet: For a star to form, The Hubble Ultra Deep Field relies on a cloud of gas to cool sufficiently so that The Hubble Ultra Deep Field can gather into the large mass required for stellar formation.
article_snippet: In particular, intracluster gas - that near the centre of a galaxy cluster - is normally a prime region for stellar formation.
article_snippet: But just a handful of stars in  are born every year in some galaxies, despite an abundance of this gas, so there must be something hindering the gas from cooling and forming stars.
article_snippet: For some galaxy clusters, the researchers from MIT and Michigan State University say, the intracluster gas may simply be too hot - on the order of hundreds of millions of degrees Celsius.
article_snippet: For some galaxy clusters, some galaxy clusters're stuck in this hot state, and will never cool and form stars,' Dr McDonald says. '
article_snippet: Once you get into this very high-temperature regime, cooling is really inefficient, and some galaxy clusters're stuck there forever.'
article_snippet: Dr McDonald added to MailOnline that maybe, over tens of billions of years, some galaxy clusters would cool down enough for stars to form.
article_snippet: Dr McDonald told MailOnline that one of the only clusters observed to be 'cool' enough to allow rapid stellar formation was the Phoenix Cluster, shown here. '
article_snippet: This system was identified in the paper as the only cluster that appears to be undergoing a massive cooling-induced starburst,' Dr McDonald said.
article_snippet: Meanwhile, for so-called 'cool core' galaxy clusters, the gas near the center may be cool enough to form some stars.
article_snippet: However, a portion of this cooled gas may rain down into a central black hole, which then spews out hot material that serves to reheat the surroundings, preventing many stars from forming - an effect the team terms 'precipitation-driven feedback.' 'Some stars will form, but before it gets too out of hand, the black hole will heat everything back up -- it's like a thermostat for the cluster,' Dr McDonald Dr McDonald said. '
article_snippet: The combination of conduction and precipitation-driven feedback provides a simple, clear picture of how star formation is governed in galaxy clusters.'
article_snippet: Dr McDonald Dr McDonald also explained to MailOnline that, if a human were to venture into one of these hot clusters, they 'probably wouldn't feel hot, because the particles are very low density.' '
article_snippet: Dr McDonald and his colleagues compared Dr McDonald and his colleagues theoretical framework with the gas cooling times of every known galaxy cluster, and found that clusters filtered into two populations - very slowly cooling clusters, and clusters that are cooling rapidly, closer to the rate predicted by the group as a critical threshold.
highlights_snippet: In some clusters of galaxies temperatures are too high for stars to form .
  