The birth of a star (actually four)

Steph P. Bianchini February 12, 2015 2 Comments

Birth is certainly one of the most emotionally charged phenomena in nature, and a star makes no exception. For much as humans tend to think about space objects as eternal, they are not – they have a start and an end, like the universe itself (yes, there’s a new theory that actually discuss if a Big Bang has actually happened. But this is the topic of another post). Sometimes we look at things that don’t even exist any longer, because they’re so far away that the images of their demise have yet to reach us (the magnificent Pillars of Creation are just an example).

Baby stars quartet (Credit:NASA)

The observations of star births do happen, but this week for the first time four infant stars have been seen emerging together from a gas cloud.  This is an important discovery, considering the high number of double and multiple stars in the universe, and it confirms the theory that stars do often begin their lives in some kind of joint fashion, instead of aggregating later on.

The age of this baby quartet in the Perseus star-forming region has been estimated at less than 100,000 years, thus it can reasonably qualify to be the youngest multiple star system ever surveyed (the single youngest stars themselves -<10,000 years old – seem to be gestating instead into the Lagoon Nebula M8).  Given their considerable distance – between 3 to 4 thousand AU – these Perseus stars were believed to be single ones too. This is because the normal distance in generally lower than that, even though there are examples of both (Albireo, the beautiful β Cyg, for example, is actually a system of three stars, two quite near – about 27 AU – e the third one farther away – 4107 AU). But then researchers found out that these stars all forming out of the same gas filaments, thus they belonged to a unique multiple system.

This kind of systems are interesting for many reasons, and not only because binary stars are known to host exoplanets or for their spectacular demise in the form of supernovae.  They are for example quite unstable systems once they’re formed, whatever the real dynamics is, and their reciprocal gravitational pull can produce a series of possible interactions, one of this resulting in the likely ejection of one of the components. Also, as throughly explained in this article on Nature, these baby stars “are the result of fragmentation of dense gas filaments, and each condensation is expected to form a star on a timescale of 40,000 years. We determine that the closest pair will form a bound binary, while the quadruple stellar system itself is bound but unstable on timescales of 500,000 years.” 

Lagoon Nebula M8 (Credit:NASA)

For some additional reading on this fascinating topic, see the following references: Moeckel, N. & Bate, M. R. On the evolution of a star cluster and its multiple stellar systems following gas dispersal. Mon. Not. R. Astron. Soc. 404, 721–737 (2010); Connelley, M. S., Reipurth, B. & Tokunaga, A. T. The evolution of the multiplicity of embedded protostars. I. Sample properties and binary detections. Astron. J. 135,2496–2525 (2008); Reipurth, B. et al. Multiplicity in early stellar evolution (2014), available at Arxiv.