The Earliest Stardust

by Paul Gilster on January 19, 2009

A familiar scenario from the early universe is getting a tune-up. It’s long been believed that cosmic dust was first produced by supernovae, becoming the essential building block for the formation of planets. New work using the Spitzer Space Telescope suggests a second mechanism that complements the first. So-called ‘carbon stars,’ stars late in their lives and similar to red giants but containing more carbon than oxygen, may have played as significant a role as supernovae themselves.

The work focused on the carbon star MAG 29, some 280,000 light years away in the Sculptor Dwarf galaxy. Says Albert Zijlstra (Jodrell Bank Centre for Astrophysics):

“All the elements heavier than helium were made after the Big Bang in successive generations of stars. We came up with the idea of looking at nearby galaxies poor in heavier elements to get a close-up view of how stars live and die in conditions similar to those in the first galaxies.”


Image (click to enlarge): The star MAG 29, shown in relation to the Sculptor Dwarf. Credit: Anglo-Australian Observatory.

This look back in time could offer clues to the formation of our own world. The existence of carbon stars in early galaxies was thought unlikely until now, but MAG 29 is found in a galaxy that contains only four percent of the carbon and other heavy elements seen in the Milky Way. It’s similar, in other words, to the primitive galaxies under active investigation at the far reaches of the universe. Learning how carbon stars contribute to dust in ancient galaxies should firm up our understanding of how these stars and their galaxies evolve. Thus Gregory Sloan (Cornell):

“We haven’t seen carbon-rich dust in this primitive an environment before. What this tells us is that carbon stars could have been pumping out dust soon after the first galaxies were born.”

It’s also interesting that MAG 29 is exceptionally rich in hydrocarbons, vital components of life’s appearance. Once again we look at phenomena in the distant universe whose chemical signature reminds us of the factors that produced life on our own planet. If we’re not inside a cosmos that is teeming with life, the real problem may be explaining why not. But is intelligence a natural outcome, and does it invariably lead to technology?

The paper in Science appears as the International Year of Astronomy launches with opening ceremonies at UNESCO headquarters in Paris. Science‘s own cover marking the event is a spectacular Spitzer image of dust clouds in the center of the Milky Way. The carbon star paper is Sloan et al., “Dust Formation in a Galaxy with Primitive Abundances,” Science Vol. 323, No. 5912 (January 16, 2009), pp. 353-355 (abstract). A Science & Technology Facilities Council news release is also available.


djlactin January 20, 2009 at 10:37

“But is intelligence a natural outcome, and does it invariably lead to technology?” No, and no.

Mark Phelps January 20, 2009 at 21:40

Well perhaps a better question is given the ‘ingenuity’ of natural selection over time
and perhaps the helping ‘hand’ of plate tectonics what sort of technologies could be
developed with some form of opposed, grasping ‘manipulators’.? Fire
and a tool environment are given,it does not a bit of good to have a culture and poems etc if you can not build a radio .(ask the Cetaceans) But Paul you are right, if it is not teeming with life,of all sorts and abilities,then that is a puzzlement. Loren Eisley
has a great quote that I will try to find on this topic.



djlactin January 22, 2009 at 1:09

Perhaps I should elaborate: (First, as background: I believe that when we have the technology, we will find that life is extremely common, and that it will take forms that we cannot imagine.) But even if we assume that like is carbon-based, cellular, and uses nucleic acids for genetic material and proteins for structure, we cannot extrapolate its evolutionary trajectory. (Evolution does not have a goal!)

In my view, the main impediment to attainment of intellect and technology is the complexity of the transition from prokaryote to euakaryote.

I think many people underestimate the importance of ‘attaining eukaryote grade’ in the attainment of complexity. Eukaryotes have their DNA bundled into separate clusters (chromosomes) and practice sexual reproduction (in which meiosis is a key process). Meiosis is a very complex process that allows events that greatly amplify genetic variability: crossing-over; recombination; duplication of genes, chromosomes, and whole genomes. These phenomena greatly amplify genetic variation, compared to prokaryotes, in which variation is essentially limited to mutation (and some rare horizontal transfer).

IMO, sexual reproduction (and backtracking: meiosis, eukaryote grade) is essential to development of specialized tissues like like nerves (and brains).

But the origin of eukaryotes was not inevitable; quite the contrary. Eukaryotes are fully-integrated chimaeras of prokaryote cells, in which reproduction of the whole assemblage somehow came to be organized into a single process. Eukaryotes are hugely more complex than prokaryotes. At the cellular level, eukaryotes have histone-coated genetic material; nuclear membranes; endoplasmic reticulum; spindles that sort the chromosomes during meiosis; organelles; spliceosomes and a lot more stuff. On an organismal level, (some!) eukaryotes have complex bodies composed of specialized tissues, which have been elaborated into organs that include (in some cases) brains.

My point is that I believe that the transition to eukaryote grade was essential to the origin (ultimately) of multicellularity, and that this transition an extremely complex process. It happened on Earth, but I don’t believe that it was inevitable; in fact, I think that it was extremely flukey, given that eukaryotes did not appear on Earth until about 2 billion years after the origin of life.

I believe that without this transition, the emergence of complex organisms, ‘grasping appendages’, and ultimately intelligence and technology, could not have occurred.

That’s my basic argument. Another is that evolution has no direction; we cannot assume that just because some trait evolved in one group, it should always evolve. Even on Earth, cultural intelligence has evolved only once (or a few times, if you count cetaceans) among tens of millions of extant species (and perhaps hundreds of millions of species if you sum this number over 3.5 billion years). It is not inevitable, and by the evidence around us, it is vanishingly rare.

Hence my previous terse response.

Adam January 29, 2009 at 19:48

Hi djlactin

I think you’ve summarised the basic complexity argument quite well, but prokaryotes form all sorts of colonies and a variety of endosymbiotic forms exist – one lineage just happens to have produced all the Eukarya. I’m not sure if the “goallessness of evolution” is really a choke-point on the road to complexity. Complexity “just happened” too when organisms learnt how to communicate and form colonies.

ljk April 7, 2009 at 13:03

Do Hydrogen-deficient Carbon Stars have Winds?

Authors: T. R. Geballe, N. Kameswara Rao, Geoffrey C. Clayton

(Submitted on 3 Apr 2009)

Abstract: We present high resolution spectra of the five known hydrogen-deficient carbon (HdC) stars in the vicinity of the 10830 Angstrom line of neutral helium. In R Coronae Borealis (RCB) stars the He I line is known to be strong and broad, often with a P Cygni profile, and must be formed in the powerful winds of those stars. RCB stars have similar chemical abundances as HdC stars and also share greatly enhanced 18O abundances with them, indicating a common origin for these two classes of stars, which has been suggested to be white dwarf mergers.

A narrow He I absorption line may be present in the hotter HdC stars, but no line is seen in the cooler stars, and no evidence for a wind is found in any of them. The presence of wind lines in the RCB stars is strongly correlated with dust formation episodes so the absence of wind lines in the HdC stars, which do not make dust, is perhaps to be expected.

Comments: 18 pages incl. 3 figures; accepted by ApJ on 3 April 2009

Subjects: Galaxy Astrophysics (astro-ph.GA)

Cite as: arXiv:0904.0652v1 [astro-ph.GA]

Submission history

From: Thomas R. Geballe [view email]

[v1] Fri, 3 Apr 2009 20:42:52 GMT (49kb)

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