The expanding universe: the redshifts of galaxies and quasars indicate distance

milky-way-atacama-desert-redshift-scopeImmensity of the observable universe

The latest article — actually the first of two related articles — by astronomer Danny R. Faulkner (2018) called “A Case for Cosmological Redshifts” was published earlier this year in Answers Research Journal. In the article, Dr. Faulkner reviewed at length three important discoveries in cosmology: the Hubble relation, the expansion of the universe, and the redshifts of quasars. Moreover, Dr. Faulkner explored the historical ramifications of these discoveries while emphasizing the development of a well-ordered cosmological model of the universe, especially regarding the construction of a correct biblical cosmology. As a result of the comprehensiveness and utility of the review, the article has rapidly become a valuable resource in the creation literature by helping many of us better understand the observational science that has taken place for close to a century now on the expanding, observable universe. This is something particularly important to those of us who are not astronomers.

Given the impact on our understanding of cosmology offered through Dr. Faulkner’s article, we are currently revising our cosmology-related question for the 2018-2019 update to our student writing contest. Presently, this question focuses on generalized concepts related to galactic redshifts and cosmic microwave background radiation. However, within the question’s revised framework, we intend to stress why the aforementioned discoveries reviewed by Dr. Faulkner are important for a working, biblically-based cosmology. Therefore, the students who choose this question for their papers will need to write about fundamental concepts behind the redshift of light. We anticipate having these students describe the electromagnetic spectrum, the duality of light, the concept of spectroscopy, and the notion of redshift. We will also require a table that highlights differences between so-called normal galaxies and the most energetic active galactic nuclei (i.e., quasars).

As for the balance of this blog, we turn our attention to the key points discussed in Dr. Faulkner’s article. However, for reasons of clarity related to definition of terms used in the article, it is worth mentioning here that when Dr. Faulkner uses the term recent creationists, he is referring to people who believe creation was recent — that is, believe in a recent creation — rather than a reference to creationists from recent decades.

The immensity of the observable universe: A quick summary of “A Case for Cosmological Redshifts.”

Hubble relation:

The Hubble relation is named after Edwin Hubble based on his famous 1929 paper “A Relation Between Distance and Radial Velocity Among Extra-Galactic Nebulae.” Using the Hooker 100-inch telescope at the Mount Wilson Observatory in California, Hubble plotted the redshifts of 24 individual galaxies (with each galaxy’s redshift expressed in velocity per second) compared to distance (in units of parsecs). A linear relationship was shown, such that the larger the galaxy’s redshift, the greater the galaxy’s distance is from the earth. Thus, the heart of the paper (i.e., the observational science behind the plot of the data) represents the original work showing an expanding universe.

Universal expansion was anticipated by early cosmologists (for example, De Sitter, Friedman, and LeMaître) who had applied general relativity to the universe prior to or about the same time as Hubble’s discovery of the Hubble relation.

– Danny R. Faulkner, Astronomer

Pragmatically, the Hubble relation confirmed a prediction based on general relativity — one of the most successfully tested theories of all time. In point of fact, prior to the publishing of Hubble’s paper, cosmologists had used the theory of general relativity to predict that the universe would be either expanding or contracting.

Dr. Faulkner painstakingly addresses three issues:

  1. Is the universe expanding? According to Dr. Faulkner, the most straightforward interpretation of the data is, “yes,” the universe is expanding.
  2. Does the redshift of light from other galaxies indicate distance? Similarly, the most straightforward interpretation is, “yes,” redshifts associated with other galaxies indicate distance. Observationally, this specific form of redshift is cosmological in nature, in other words, occurring because of the stretching of space (see below).
  3. Does the redshift of light from quasars also indicate distance? From Dr. Faulkner’s review of evidence compiled over the last 50 years, this answer is a compelling “yes.” Here, too, the redshift is also cosmological in nature, which means it likewise occurs as a result of the stretching of space (again, please see below).

The expanding universe and the redshifts of galaxies and quasars indicate distance.

Difference between Doppler motion and cosmological redshifts:

Doppler motion describes the shift of light out of the visual range and into either the bluer ultraviolet range (for light from objects that travel toward you) or the infrared range (for light from objects that travel away from you). More precisely stated, the wavelength of light from objects traveling toward you is compressed, and the wavelength of light from objects traveling away from you is stretched. Therefore, because everything in space is always moving (including our solar system), the light from any light-emitting object in the observable universe is the combined sum of its Doppler motion (either blueshifted or redshifted) and its cosmological redshift (due to the inherent stretching of space away from us).

As a result of all of this stretching and compressing of the wavelengths of light across the universe, we discover one important fact: the farther away that an object is from us, the more redshifted the signal becomes. In other words, we can have confidence that the light from objects of great distance is dominated by (or more heavily weighted toward) the infrared range of the spectrum.

Hubble constant:

The Hubble constant, H0, is the measurement that defines the expansion rate of the universe. Today’s estimate for H0 is roughly 70 kilometers per second per megaparsecs (i.e., 70 km/s/Mpc).

Enter quasars:

Quasars were initially discovered in the early 1960’s, but it took astronomers some time to figure out what they were seeing. In fact, the term quasar means “quasi-stellar object.” According to Dr. Faulkner, a quasar is a point in space that has more luminosity than that of an entire galaxy (trillions of stars). Though described as a “point in space,” quasars are roughly the size of our solar system compared to the enormous span of a galaxy, such as our very own Milky Way Galaxy or perhaps the “near-by” Andromeda Galaxy. One of the most popular quasars is known as 3C 273; however, a quasar called 3C 454.3 is one of the most luminous known objects in the universe. It is thought today that quasars are powered by super-massive black holes.

artistic-quasar1Artistic rendition of a quasar

Notably, quasars emit across the entire electromagnetic spectrum, from radiowaves to x-rays. In fact, they were first discovered through radiotelescopes. However, as already mentioned, the most distinguishing feature about quasars is their high luminosity (since their peak emission is in the near ultraviolet and optical ranges). It is also important to note that quasars have a large redshift that is cosmological in nature, and thus quasars are very distant objects. More importantly, this combination of high redshift and vast distance equates to a large look-back time (and we can consider look-back time as our window into the observable universe).

Today, quasars are recognized as early galaxies, and are described or noted as galaxies characterized with an active galactic nucleus (AGN). Interestingly, our understanding of galaxies is presently viewed as a continuum that ranges from the most active AGNs (such as quasars) to the so-called normal galaxies (such as the Andromeda Galaxy or the Milky Way).

Remark: Earlier we mentioned that the article highlighted here is the first of two related publications by astronomer Danny R. Faulkner in Answers Research Journal. For the sake of completeness, in the second article called “A Test for Quasar Cosmological Redshifts,” Dr. Faulkner published the outcome of a simple test that revealed a correlation between the redshifts of quasars and their corresponding apparent magnitudes (a finding that supports extragalactic, cosmological redshifts). In the concluding remarks of that work, Dr. Faulkner argues that “it would be much more productive [for recent creationists] if extragalactic redshifts were incorporated into developing a recent creation cosmology” (p. 54).

One reason an understanding of cosmological redshifts becomes important to further study is that two telescope projects are currently underway: the Giant Magellan Telescope and the James Webb Telescope. The former is a land-based telescope located in Chile, and the latter is a space telescope scheduled to be the replacement for the Hubble Space Telescope (HST). Both of these telescopes will have better imaging capabilities than the HST, and thus reach farther back in look-back time.

References

Faulkner, D.R. (2018). A case for cosmological redshifts. Answers Research Journal, 11(3),31-47. Retrieved from https://assets.answersingenesis.org/doc/articles/pdf-versions/arj/v11/cosmological_redshifts.pdf.

Faulkner, D.R. (2018). A test for quasar cosmological redshifts. Answers Research Journal, 11(4),49-56. Retrieved from https://assets.answersingenesis.org/doc/articles/pdf-versions/arj/v11/test_quasar_cosmological_redshifts.pdf.

Hubble, E. (1929). A relation between distance and radial velocity among extra-galactic nebulae. Proceedings of the National Academy of Science of the United States of America, 15(3), 168-173. Retrieved from http://www.pnas.org/content/pnas/15/3/168.full.pdf.