Ongoing development in high-precision cosmology may soon provide yet even more compelling evidence for the supernatural origin of the universe. Astronomers’ ability to accurately measure distances to “standard candle” stars has been the limiting factor in their quest to build a precision model for the origin and history of the universe. However, a recent measurement has lowered this limit by a factor of nearly five times.1
Measuring Astronomical Distances
The most critical measurements needed for developing a detailed cosmic creation model are measurements of the cosmic expansion rates at different epochs throughout the history of the universe. Such measurements require knowledge of the velocities at which astronomical bodies are moving away from us and knowledge of the distances to those astronomical bodies. (Expansion rate = velocity/distance.)
Spectra (measurements of the different wavelengths of radiation) of the bodies provide high-precision measures of their velocities, sometimes to better than 0.001 percent. The limiting factor is the distance measurements. Presently, astronomers consider themselves fortunate if they have a distance measurement accurate to ±5 percent.
Standard candle stars provide the pathway toward the best astronomical distance measurements. A standard candle star has a known intrinsic or absolute luminosity. The apparent luminosity of a star is the observed brightness of the star from Earth. This brightness depends on the distance of the object. The inverse square law for light implies that with every doubling of the distance, the apparent luminosity dims by four times. Astronomers define the absolute luminosity of a star as the apparent luminosity it would manifest if it were located exactly 10 parsecs (32.6156 light-years) away.
A standard candle in astronomy is a class of objects that (1) all possess the same absolute luminosity, or (2) all possess a characteristic that permits their absolute luminosity to be calculated. An example of the first category is a type Ia supernovae. When such stars go supernova, at a certain time in their eruptive phase they all manifest the same intrinsic or absolute luminosity. An example of the second category is a Cepheid variable star. Cepheids are regularly pulsing stars. Their pulsation period is related to their absolute luminosity in a known way.
Using the inverse square law of light, astronomers can convert a measurement of the apparent luminosity of a standard candle star into the absolute luminosity of that star. This method assumes, of course, that for that category of standard candle stars astronomers possess an accurate direct distance measurement to at least one such standard candle star.
A direct distance measurement is one based on the plane geometry theorem students learn in high school. For any isosceles triangle, from knowledge of the length of the base of the triangle and the angles at both ends of the base, one can determine the distance to the vertex of the triangle (see figure 1).
Figure 1: Geometric Distance Measuring Method. Measurements of the angles, a and b, and of the baseline distance, C, yields the distance to the vertex, D, free of any assumptions. Image credit: Hugh Ross
One Measurement Breakthrough
An international team of 21 astronomers announced in a recent issue of the Astrophysical Journal that they had achieved the most accurate direct distance measurement to date for a Cepheid variable star.2 Their measurement was possible because the Cepheid variable star they observed, V1334, is orbited by a companion star.
Newton’s laws of motion state that the time it takes for a massive body to orbit another massive body is determined by the diameter of the orbit. Therefore, if astronomers can accurately determine the timing of the orbital period, they gain a measure of the diameter of the orbit in kilometers, light-years, or parsecs. Then, an accurate measure of the angle of the cross section of the orbit as seen from Earth yields a direct, assumption-free measurement of the distance to the two stars (see figure 2).
Figure 2: Geometric Distance Measurement to the Binary Cepheid V1334. A measure of the period of the orbit of the companion star near V1334 yields the diameter of the orbit. A measure of the angle subtended by the orbit as seen from Earth yields the distance to V1334 and its companion star. Image credit: Hugh Ross
The most observationally challenging component of the distance measurement to V1334 was determining the angle subtended (viewed from the vertex) orbit as seen from Earth. The 21 astronomers gained unprecedented accuracy in this angular measurement through observations carried out from July 2012 to October 2016 using the best optical interferometer currently available. They used the Michigan Infrared Combiner (MIRC) installed at the Center for High Angular Resolution Astronomy (CHARA) located on Mount Wilson overlooking the Jet Propulsion Laboratory and the California Institute of Technology in Pasadena, California.
MIRC consists of six 1-meter-diameter optical telescopes placed in a Y-shaped configuration with two telescopes on each branch of the Y. The baselines of the Y can be varied from 34 to 331 meters. The angular resolving power of MIRC is 0.2 milliarcseconds, equivalent to the angular size of a nickel seen from a distance of 10,000 miles away and more than fifty times superior to the best-achievable resolution of the Hubble Space Telescope.
The astronomers’ measurements on V1334 rank as the first time that a binary Cepheid star was resolved both spatially and spectroscopically. They rank, by a factor of nearly five times, as the most accurate geometric distance ever made on a Cepheid variable star. The geometric distance the astronomers measured for V1334 = 720.35 ± 7.84 parsecs (2,349.46 ± 25.57 light-years). That is, the team achieved a distance measurement to V1334 accurate to ± 1 percent.
The researchers also achieved the most accurate mass measurement for a binary Cepheid variable star system. They measured the masses of the two stars to be 4.288 ± 0.133 solar masses (Cepheid) and 4.040 ± 0.048 solar masses (companion). These accurate mass measurements will enable astronomers to develop more detailed models for the burning history of giant stars.
An important caveat noted by the team of 21 is that the companion star is sufficiently close to V1334 as to make separating its light contribution from that of V1334 challenging. Thus, it is premature to claim that a factor of five improvement in cosmic creation models has been achieved. Hence, the team calls for more MIRC observations of the V1334 system and to use MIRC to make observations on other binary star systems.
Nevertheless, these 21 astronomers have demonstrated through their measurements that very-high-precision cosmology is just around the corner. Such high-precision cosmology has the potential to deliver ever stronger evidence for the biblically predicted cosmic creation model.2
Featured image: RS Puppis, one of the brightest Cepheid variable stars in the Milky Way Galaxy. Image credit: NASA/ESA/Hubble Space Telescope