Many astronomy articles have a bad habit of assuming star formation without demonstrating or explaining it.
In Hollywood, A Star Is Born by intelligent design. Out in the near vacuum of space, however, it’s complicated. The laws of physics don’t cooperate. Gravity may begin condensing gas and dust toward a hopeful career in the lights, but then those darn laws of heat and pressure take over, pushing the gas back out. Something has to give the gas an extra push to make it over the pressure barrier. Maybe a supernova explosion could do it. That appeal, however, is likely to get philosophers of science smirking. They will ask, “If that is your answer, where did the first stars come from, before there were no supernovas?” [For purists, that’s supernovae.] “You can’t require stars to make stars.”
Let’s review; here are previous CEH stories on the subject of star formation.
- In 2005, star formation was described as a “very rich problem” in astronomy (11/18/05).
- In 2007, one “elegant” theory of quiet star formation was judged “wrong” (6/30/07).
- In 2011, we learned there is “still much that astronomers don’t understand” about star formation, including what triggers it (2/22/11).
- In 2014, star formation theory was caught in a fast-and-furious scandal (9/30/14).
- In 2015, we caught astronomers lying about star formation (6/20/15).
Many astronomers and science reporters like to waltz around these issues, simply assuming that stars form somehow. There are lots of stars, after all. Obviously they formed, right? It seems justifiable to talk about “star formation” without having to explain it. Here are some recent examples of how astronomers leap over the difficulties, speaking of star formation without explaining how stars can form by natural processes.
One might think Phys.org‘s article “Forming stars in the early universe” would talk about forming stars. Let’s search on “form” in the article.
- The first stars appeared about one hundred million years after the big bang, and ever since then stars and star formation processes have lit up the cosmos.
- When the universe was about three billion years old, star formation activity peaked at rates about ten times above current levels. Why this happened, and whether the physical processes back then were different from those today or just more active (and why), are among the most pressing questions in astronomy.
- Since stars are made from gas, the gas content of galaxies is a measure of their star formation potential and (at least in the local universe) the fraction of matter in form of gas, the “gas fraction”, is a measure of the star formation capability.
- Gas in galaxies is depleted as new stars are formed and as some of it is blown out of the system by supernovae or by winds; gas can also be added by infall from the intergalactic medium.
You see a pattern developing; star formation is spoken of as a matter-of-fact process – but without the process. It doesn’t do any good to speak of “star formation activity” or “star formation potential” when you can’t explain the origin of a single star.
Maybe that’s a bad example. Instead of a layman’s science site, let’s look at Nature, the world’s premiere science journal. Here’s a short news item titled, “Star Formation: Star-rich early galaxy clusters.” Look carefully for an explanation of how stars form.
When a galaxy becomes part of a cluster — a group of galaxies bound together by gravity — its crowded surroundings often cause it to stop producing stars, an effect called environmental quenching. Using the Keck Observatory in Hawaii and the Very Large Telescope in Chile, a team led by Julie Nantais at the Andres Bello University in Santiago observed four galaxy clusters nearly 10 billion years old. They found that, in these early clusters, only about 30% more of the galaxies had stopped producing stars than had the surrounding galaxies, compared with a difference of about 50% in newer clusters.
Knowing how quenching changes over the history of the Universe may help scientists to determine why the cluster environment causes the phenomenon.
No help here. That was about stopping star formation. There’s no explanation of how it starts, or how it works. Again, the writer merely assumes star formation occurred somehow. Same in Science Daily‘s lengthier coverage of the survey. “The paper concludes that about 30 percent of the galaxies which would normally be forming stars have been quenched in the distant clusters, compared to the much higher value of about 50 percent found in nearby clusters.”
Try, Try Again
Let’s try again. Science Daily presents another story titled, “New stars discovery shed new light on Galaxy’s formation.” Sounds like a good article to look for explanations, considering it comes from the Hubble Space Telescope Science Institute. While primarily about galaxy formation, it includes star formation, because obviously you can’t have a galaxy without stars (ever heard of a “gas galaxy”?). We search on “form” again:
- An astronomer from LJMU’s Astrophysics Research Institute has discovered a new family of stars in the core of the Milky Way Galaxy which provides new insights into the early stages of the Galaxy’s formation.
- The discovery has shed new light on the origins of globular clusters — which are concentrations of typically a million stars, formed at the beginning of the Milky Way’s history.
- This means that a substantial fraction of the old stars inhabiting the inner parts of the Galaxy today may have been initially formed in globular clusters that were later destroyed.
- Ricardo Schiavon, lead researcher on the project said: “This is a very exciting finding that helps us address fascinating questions such as what is the nature of the stars in the inner regions of the Milky Way, how globular clusters formed and what role they played in the formation of the early Milky Way — and by extension the formation of other galaxies.”
This article turns out to be less than helpful. It talks primarily about the destruction of globular clusters that should have formed but are not seen.
Try, Try, Try Again
Let’s give Science Daily one more pitch. In “Large number of dwarf galaxies discovered in the early universe: Astronomers have discovered a large number of dwarf galaxies in the early universe by using the gravitational lensing phenomenon” we look once more for a scientific explanation of star formation. We’re getting warmer! This article promises science that “could reveal important details about a productive period of star formation in the universe billions of years ago.” It teases with a discussion of “the most productive time for star formation in the universe.” Together we peer into the crystal ball of the early universe. We see faint, dwarf galaxies. They speak:
Despite their faintness, these dwarf galaxies produce more than half of the ultraviolet light during this era. As ultraviolet radiation is produced by young hot stars, dwarf galaxies host a significant fraction of newly-formed stars at these cosmic times.
Is that it? Stars are producing UV light all right, but where did stars come from? “Newly-formed stars” – how is that possible? Who formed them? What formed them?
If you saw a lot of cakes in bakeries, but never saw one being made, you would assume some process of cake formation exists. You might be justified writing about “cake formation” in articles. But what if you wrote that cakes spontaneously appear by some unknown natural process? That’s the point where you open yourself up to criticism, especially if you are a scientist.
Stars obviously exist, and there is some process of star formation, whether natural or designed. Astronomers may some day put together a coherent, testable theory of natural star formation. But they need to prove it, not assume it.
Let’s all sing the cosmology song from 12/05/2008:
When you wish upon a star, nature makes you what you are,
Anything your heart concocts is science true.
If your heart is in your dream, no proposal’s too extreme
When you hyper-speculate as scientists do.
Fate is kind, she gives reality,
The sweet fulfillment of our observing.
Like a bolt out of the blue, observation creates you,
When you wish upon a star, your dreams come true.