Suprise: ALMA got to see the line where snow starts around a young star 
New discoveries

Suprise: ALMA got to see the line where snow starts around a young star 

Read time: 3 minutes

What happens if you throw little sticks or dry pine needles in a camp fire? The flames get brighther and the air gets warmer, right? Something similiar happens with new born stars! 

A few million years after they are born, most stars are surrounded by a disk of swirling gas and dust where planets and moons are born. From time to time, there is material from that disk that falls onto the young star, pulled by its gravity, making it shine brighther and heat up everything around it. 

Now, using ALMA, astronomers captured the first image showing the effects of this outbursts of heat and light on the disk surrounding the young stars. Suprisingly, it looks a lot like what you would see if you made your camp fire in a field full of snow! 

The image captured by ALMA shows a line separating the part of the disk where it is too hot for water to exist in any form other than vapor, and the part that is far away enough for the dust and particles to be frozen. Exactly the same line you would see in the camp fire! There would be a circle in the ground without snow, because the heat from the fire would melt it. But also a point where the warmth coming from the fire would stop being enough and everything would be covered in snow. 

This is a very special observation. Normally, there´s no way for astronomers to see this separation line – called water snow line – because it is too close to its star and even very powerful telescopes are dazzled by its radiation. 

The young star observed with ALMA, situated in the famous Orion constellation, is unique though. It burned so bright because of the material falling on it, that it pushed the water snow light far away enough for the phenomenon to be captured for the first time. 

For astronomers, this image opens a new door in the understanding of the formation of star systems in the Universe, including our own Solar System. 


The water snow line was observed in the protoplanetary disk of a young star called V883 Orions. It is located in the famous constellation of Orion. However, V883 Orions is a very faint star, so you will need a big telescope to see it with your eyes. It was the first time astronomers where able to observe this phenomenon, even though they already knew it happens. 


The water snow line observations were made by a group of astronomers lead by Lucas Cieza. Lucas is an astronomer from University Diego Portales in Santigo (Chile). 

The team published their results in a very important scientific magazine called Nature