Stellar cocoon doesn’t contain ingredients for recipe of life
If you want to cook up a nice meal, you need the right ingredients. Without beans, you can’t make a good chili. And to bake an apple pie, you need apples, of course. In the Universe, it’s the same. The available ingredients determine what can be ‘cooked up’.
One of the most special things that have formed in the Universe are living organisms, like bacteria, plants, animals and people. Life could only form in our Milky Way galaxy because the right ingredients were present: organic molecules. Now, ALMA has found that those molecules may not always be so common.
Japanese astronomers used ALMA to study a massive newborn star in the Large Magellanic Cloud. The Large Magellanic Cloud is a small galaxy, just beyond our own Milky Way. From the southern hemisphere, it can easily be seen on a clear night as a nebulous patch in the sky.
ALMA found that the star is embedded in a thick cocoon of dust particles and molecules. Such cocoons have also been found around young stars in the Milky Way. They usually contain lots of organic molecules, such as methanol and ethanol. Those molecules are an important ingredient for the recipe of life.
The cocoon that surrounds the star in the Magellanic Cloud is the first one found in another galaxy. Surprisingly, it has a very different chemistry. Some molecules, like sulfur dioxide, nitric oxide and formaldehyde, are present in large quantities. But the cocoon has almost no organic molecules like methanol.
Astronomers already know that the Large Magellanic Cloud has a different chemical makeup than the Milky Way. Atoms heavier than hydrogen and helium are less common. Maybe that difference has affected the formation of certain molecules.
If the ‘kitchen’ of the Large Magellanic Cloud contains different ‘ingredients’ than the kitchen of the Milky Way, it may be more difficult to ‘cook up’ life in this neighboring galaxy. Anyway, the discovery reveals that the chemistry of the Universe may vary strongly from place to place.
The Large Magellanic Cloud and the Small Magellanic Cloud are two small galaxies orbiting our larger Milky Way galaxy. The Large Magellanic Cloud is at a distance of some 170,000 light-years. It contains many active star-forming regions. The newborn ‘young stellar object’ observed by ALMA is known as ST11 (its official designation is 2MASS J05264658-6848469). The cocoon of gas and dust that surrounds the star is called a hot molecular core. It is less than one light-year across. The word ‘hot’ is misleading: the cocoon is more than 150 degrees Celsius below zero. It’s called ‘hot’ because most molecular clouds are much colder still.
The composition of ST11’s cocoon was determined by four Japanese astronomers: Takashi Shimonishi of Tohoku University in Senday, Takashi Onaka of the University of Tokyo, Akiko Kawamura of the National Astronomical Observatory of Japan, and Yuri Aikawa of the University of Tsukuba. The four astronomers have published their results in The Astrophysical Journal.