Have you ever looked through a family member’s photo album? As you look over the different photographs, the history of that relative’s life unfolds. The album is especially revealing if the photographs are dated.
In much the same way astronomers learn a lot about the universe by examining its status at different points in its history, known as “look-back times.” They learn even more when they can determine the timing of different events in the universe’s history accurately. What researchers have, in fact, learned during the past few weeks yields several important tests for creation.
Detailed examination of the history of the universe can test the biblical doctrine of cosmic creation in five important ways:
- Was the universe created?
- How was the universe created?
- Was the universe supernaturally designed in advance for life and human beings in particular?
- How successful was the Bible in predicting future scientific discoveries about the universe?
- How old is the universe?
Of course, accurate understanding of the details of the universe’s history requires reliable chronometers to provide accurate data. The “main-sequence turn-off point” represents one standard chronometer used by astronomers for several decades. Now a team of four Italian and three American astronomers led by M. Cignoni has demonstrated that the “pre-main-sequence turn-on point” provides another useful chronometer.1
Star Bright, Star Light
The main sequence is a continuous band of stars that appears when astronomers plot star color against star luminosity (brightness). This color-luminosity plot is known as the Hertzsprung–Russell diagram named after its developers (see figure 1).
Figure 1: The Hertzsprung–Russell Diagram
The mass and age of a star determines both its luminosity and color. At certain points in its history (the main sequence lifetime) a star changes luminosity and color far more slowly than it does at other times.
Image credit: Richard Powell
Main-sequence stars are stars whose light output results from the nuclear fusion of hydrogen into helium. The more massive a main-sequence star the brighter its luminosity and the bluer its color. Stars remain on the main sequence as long as they possess in their cores hydrogen that can be fused into helium.
While on the main sequence, stars move very slowly up the main sequence track. For example, the Sun has been on the main sequence for the past 4.5 billion years and still retains an additional 4.5 billion years worth of hydrogen ready to fuse into helium. However, the length of time a star spends on the main sequence is greatly dependent on its mass. The more massive a star, the faster it consumes its hydrogen fuel. Supermassive stars spend as little as a million years on the main sequence, while the least massive stars can spend as much as eighty billion years.
Pre-main-sequence stars have not yet ignited nuclear fusion because they are not old enough to have gravitationally condensed sufficiently. Post-main-sequence stars are stars that have exhausted their supply of hydrogen that can be fused into helium.
The main-sequence turn-off is the point on the Hertzsprung-Russell diagram at which stars in the plotted cluster begin to leave the main sequence. That is, the stars begin to move to the right, or redder part, of the Hertzsprung-Russell diagram. Consequently, the main-sequence turn-off point is a measure of a star cluster’s age. The older a star cluster, the fainter the main-sequence turn-off point (see figure 2).
Figure 2: Main Sequence Turn Off Points
Astronomers know the star cluster NGC 188 is older than M67 because in NGC 188 fainter (and consequently less massive) stars are turning off to the right from the main sequence.
Image credit: User: Worldtraveller
Up until the past few years, measurements of the main-sequence turn-off points for a large ensemble of the oldest star clusters represented the most accurate method astronomers possessed for calculating the age of the universe. This method was precise because stars are so simple (giant balls of completely ionized gas where hydrogen and helium make up about 98 percent of the gas) that straightforward physics (the gas laws and the principle of hydrostatic equilibrium) predicts in detail exactly where on the Hertzsprung-Russell diagram a star of a given mass and age will reside. Using Newton’s laws of motion astronomers could accurately determine the masses of at least a few of the stars in a particular cluster. Thus, measurements of the colors and luminosities of most of the stars in a cluster yield an accurate calculation of that cluster’s age.
Astronomers attain other important information about the universe by determining the main-sequence turn-off points for a large number of star clusters. The turn-off points are a distance indicator. Thus, turn-off point measurements for star clusters over a wide range of ages give astronomers an accurate picture of how rapidly the universe has expanded over its entire history. Turn-off point measurements also help astronomers test and refine their theories of the evolution (burning history) of stars. This is helpful because, while astronomers can calculate the history of high-mass stars accurately and unambiguously (owing to these stars’ simple structure and composition), the situation is more complex for low-mass stars.
Now the research team led by Cignoni has given astronomers a tool for determining the ages and burning history for very young high-mass stars and for young low-mass stars. They demonstrated that main-sequence turn-on points for star clusters provide an equally accurate chronometer compared to main-sequence turn-off points. The team showed for all star cluster ages younger than 15 million years that the isochrone (positions of stars in the Hertzsprung-Russell diagram manifesting the same age) portion just before the main sequence has a hook and then becomes significantly flatter than the main sequence. The main-sequence turn-on is at the vertex of the hook and, like the main-sequence turn-off point, is quite easy to recognize. Cignoni’s team proved the effectiveness of their pre-main-sequence turn-on technique by showing its efficacy for determining the ages of three young star clusters in the star-forming region NGC 346 in the nearby dwarf galaxy the Small Magellanic Cloud. They measured the ages of clusters SC-1, SC-13, and SC-16 to be 3.5–6.5 million years, 3.0 million years, and 12.5–18.0 million years, respectively.
The new technique developed by Cignoni’s team is extending the range over which astronomers can measure the cosmic expansion rate, the physics of star burning, and the detailed history of the universe. Such an extension will provide an even more definitive test of the biblical doctrine of cosmic creation. It also yields yet another falsification of the young-earth creationist model. It demonstrates that for even the youngest star clusters the derived ages are about a thousand times greater than the claimed age for the universe in young-earth creationism.
In part 2 of this series I will describe another new cosmic chronometer, one that measures the time of death for a star cluster.
|Part 1 | Part 2 | Part 3 | Part 4|