The Planck telescope, which launched in May with another telescope Herschel, has reached its destination – the second Lagrangian point 1.5 million kilometres away from Earth. It has also reached its working temperature – a chilly 0.1 degrees above absolute zero, making the craft officially the coldest thing in space.

On the Planck science website, the temperature 0.1K is written in big red letters and the feeling is one of jubilation: “This is a very big milestone for Planck… Hurrah !”

Of course, this news isn’t exactly unexpected – the real news would have been if Planck’s coolers had failed to cool the instrument sufficiently, because this would have made it impossible to carry out the mission to measure the cosmic microwave background.

But any excuse to write corny headlines like “ESA’s Planck is Truly Too Cool” (Errr, actually, it isn’t too cool, rather it is just cool enough), or “”https://www.hardocp.com/news.html?news=NDA1NTksLCxoZW50aHVzaWFzdCwsLDE=“>ESA’s Planck Telescope is One Cool Spacecraft” (technically correct) . We also get a nice analogy from the press release about the trouble Planck has picking out the tiny variations in the CMB. Seeing the tiny changes in temperature, that might be remnants of the big bang, is comparable to measuring from Earth the heat produced by a rabbit sitting on the Moon.

Image: ESA – D. Ducros