Astronomer: In around six to seven billion years the Sun will exhaust all its hydrogen fuel and begin the process of stellar death. When that happens, the Sun will grow so large it will engulf planet Earth. Audience member (distressed): Wait, when will this happen? Astronomer: Six to seven billion years from now. Audience member: Whew! I thought you said million.
A recently published paper shows that the number of stars in the universe may be three times larger than previously thought. Increasing the calculated number of stars in the universe seems like a big change. However, just as the difference between millions and billions of years is inconsequential on a human timescale, the change in star count is not a big deal. In fact, the change reflects good scientific practice and progress. It also points toward another argument for design. Here’s how.
In order to measure the number of stars in the universe, astronomers take the number of galaxies in the universe and multiply that value by the number of stars contained in an average galaxy. Although this may sound simple, the process involves difficult observations and assumptions that must be verified. To find the number of galaxies in the universe, astronomers make careful, thorough observations of a particular some region of the sky. For example, the most detailed picture to date for this purpose is the Hubble Ultra Deep Field (HUDF). Based on the 10,000 galaxies in the HUDF and the size of the image on the sky (roughly one fiftieth the size of the Moon), scientists estimate that the universe contains around 100 billion galaxies. However, because of the assumptions involved and our inability to see every galaxy, we can only approximate the number of galaxies in the universe.
After estimating the galaxy count, astronomers need to know the number of stars in each galaxy. Since astronomers can measure the types of stars in our galaxy, the simplest approach is to assume that all galaxies have a distribution of stars like the Milky Way. A paper published in Nature shows how scientists tested this assumption and found it inaccurate. As it turns out, large elliptical galaxies (where most of the stars in the universe reside) have a larger fraction of smaller, red M-dwarf stars.1 Because M-dwarf stars are the most abundant type of star, using this latest, more accurate research increases the estimate of the number of stars in the universe.
Two apologetic points warrant mention regarding this discovery. First, galaxy type and environment influence the number and kind of stars formed. Large elliptical galaxies represent one of the dominant galaxy types in the universe and this recent research provides more evidence that these types of galaxies don’t host habitable planetary systems. The stars in elliptical galaxies typically formed long ago (before sufficient heavy elements that habitable planets require existed). This research shows that an even larger fraction of the stars in elliptical galaxies are M-dwarfs—stars that pose serious problems for habitable planets.
Second, a common charge leveled against RTB is that using scientific discoveries to inform biblical interpretation risks undermining the authority of Scripture. According to this line of reasoning, science changes but the Bible doesn’t. Thus, coupling our scientific understanding to our theology puts biblical interpretation on an unstable scientific footing. However, this argument fails to properly understand how RTB frames its biblical and scientific models. In both scientific and theological interpretation, certain issues and ideas play critical roles and others play secondary (or tertiary) roles. In relation to primary issues such as the universe being created, science provides the strongest evidence to affirm the interpretation. In the secondary issues, many interpretations exist and science can help choose which of these interpretations is correct. Even less overlap exists for tertiary issues such as the number of stars in the universe. In this instance, tripling the number of stars in the universe has no impact on our biblical interpretation because the Bible does not address this issue in any significant way.
Astronomers continue to test the assumptions used in determining the number of stars in the universe. In this instance, the assumption needed revision and provided additional evidence that the universe is fine-tuned for our existence. RTB expects future scientific research to continue this trend.
- Pieter G. van Dokkum and Charlie Conroy, “A Substantial Population of Low-Mass Stars in Luminous Elliptical Galaxies,” Nature, published online December 1, 2010, doi:10.1038/nature09578.