In the search for distant planetary systems, astronomers employ a special method to discover planets beyond the range of our telescopes. Thanks to the theory of general relativity, astronomers have access to gravitational lenses that far outstrip the power of any telescope they can build. But even with the amazing detection capabilities afforded to us by gravitational lensing, scientists have yet to discover a planetary system as hospitable to life as our own.

What Is Gravitational Lensing?

Gravitational lensing exists in three forms: strong (or macro) lensing, weak lensing, and microlensing. Strong gravitational lensing occurs whenever a giant galaxy or a cluster of galaxies lies along the line of sight between us and a distant quasar or galaxy. The strong gravitational field of the giant galaxy or cluster of galaxies bends and magnifies the light emitted by the more distant quasar or galaxy. The magnified light of the distant quasar or galaxy, if perfectly aligned, appears as a circle of light, termed an Einstein ring, around the giant galaxy or cluster of galaxies. Figure 1 shows such an Einstein ring.

Figure 1: This Einstein ring occurred as the gravity of a large red galaxy gravitationally distorted the light from a much more distant blue galaxy into a ring.
Image credit: NASA/ESA/Hubble

In weak gravitational lensing, either the alignment is much less than perfect or the gravitational field of the intervening galaxy or galaxy cluster is relatively weak so that the magnified light of the distant galaxy or galaxies fails to form a circle or a set of bright spots. Instead, what astronomers see is a general distortion of images surrounding the intervening galaxy or galaxy cluster (see figure 2).

Figure 2: Image distortion resulting from weak gravitational lensing
Image credit: Wikimedia Commons/TallJimbo

In the case of gravitational microlensing, no distortion in the shape of the image occurs. Light from a distant star is bent by the gravitational field of a closer star that lies in the line of sight (see figure 3). The presence of a planet orbiting the closer star affects the degree of bending of light from the more distant star in a periodic manner. By measuring the period of the change in light bending and the degree of the change, astronomers can determine both the orbit and the mass of the planet.

Figure 3: Gravitational microlensing influenced by an orbiting planet
Image credit: NASA

Advantages and Effectiveness of Gravitational Lensing

The first planet to be detected by gravitational microlensing was OGLE-2003-BLG-235Lb. Discovered in April 2004, the planet appears to be a gas giant planet (similar to Jupiter) that is located approximately 4.3 AU away from its parent star. Unlike other planet detection methods, gravitational microlensing can discover planets tens of thousands of light-years away from Earth and even find planets in other galaxies. Another advantage over alternate detection methods is the ease with which low mass planets and planets that are farther away from their host stars can be located.

The advantages of the microlensing technique give astronomers an opportunity to build a relatively unbiased sample of exoplanets for statistical analysis. Such analysis can help answer the question of whether or not our solar system is unique among planetary systems in manifesting the characteristics needed for complex life to exist on one of the planets in the system.

So far, only 30 planets have been discovered by the microlensing technique. Nevertheless, this sample prompted the three largest microlensing research teams (the OGLE collaboration, the MOA collaboration, and the MiNDSTEp collaboration) to jointly publish the first statistical analysis of their research.1 They reported three findings:

1. Thirty-eight percent of stars host cold super-Earths or cold Neptunes.

2. Forty percent of planets found by microlensing are either cold Neptunes or cold sub-Saturns.

3. Cold super-Earths and cold Neptunes are about seven times more abundant than cold Jupiters.

Here, a cold planet is defined as one that is at least 1.6 times more distant from its host star than Earth is from the Sun. A super-Earth is a planet 1–10 times Earth’s mass. A Neptune is a planet around 10–30 times Earth’s mass. A cold sub-Saturn is a planet that is 30–80 times Earth’s mass. And a cold Jupiter is a planet approximately 100–3,000 times Earth’s mass.

With only 30 planets in the microlensing catalogs, these results are preliminary. Time will reveal the degree to which these initial statistical findings are confirmed.

How Do Exoplanets Size Up to Ours?

By comparison, our solar system possesses no super-Earths at all; it has as many cold Jupiters as it has cold Neptunes, namely two; and our system’s cold Neptunes are located more than 18 times Earth’s distance from the Sun, as compared to less than nine times Earth’s distance for the sample of cold Neptunes in the microlensing catalogs. All of these distinct features of our solar system are critical for enabling advanced life to exist on Earth.

The fact that no other planetary system out of the 1,349 discovered so far possesses the configuration of planets needed for advanced life to possibly exist within that system is evidence that a supernatural, superintelligent Creator personally designed our solar system so that humans and all advanced plant and animal life could exist and thrive on Earth.2 The expanding microlensed planet catalogs yield yet another demonstration that the more we learn about exoplanets and exoplanetary systems the more evidence we accumulate for the handiwork of God in designing the solar system for the specific benefit of human beings.

Food for Thought

Do you think it’s a good use of resources to continue the search for extraterrestrial life? Visit TNRTB on Wordpress to comment with your response.

Subjects: Solar System Design

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About The Author

Dr. Hugh Ross

Reasons to Believe emerged from my passion to research, develop, and proclaim the most powerful new reasons to believe in Christ as Creator, Lord, and Savior and to use those new reasons to reach people for Christ. I also am eager to equip Christians to engage, rather than withdraw from or attack, educated non-Christians. One of the approaches I’ve developed, with the help of my RTB colleagues, is a biblical creation model that is testable, falsifiable, and predictive. I enjoy constructively integrating all 66 books of the Bible with all the science disciplines as a way to discover and apply deeper truths. 1 Peter 3:15–16 sets my ministry goal, "Always be prepared to give an answer to everyone who asks you to give the reason for the hope that you have. But do this with gentleness and respect, keeping a clear conscience." Hugh Ross launched his career at age seven when he went to the library to find out why stars are hot. Physics and astronomy captured his curiosity and never let go. At age seventeen he became the youngest person ever to serve as director of observations for Vancouver's Royal Astronomical Society. With the help of a provincial scholarship and a National Research Council (NRC) of Canada fellowship, he completed his undergraduate degree in physics (University of British Columbia) and graduate degrees in astronomy (University of Toronto). The NRC also sent him to the United States for postdoctoral studies. At Caltech he researched quasi-stellar objects, or "quasars," some of the most distant and ancient objects in the universe. Not all of Hugh's discoveries involved astrophysics. Prompted by curiosity, he studied the world’s religions and "holy books" and found only one book that proved scientifically and historically accurate: the Bible. Hugh started at religious "ground zero" and through scientific and historical reality-testing became convinced that the Bible is truly the Word of God! When he went on to describe for others his journey to faith in Jesus Christ, he was surprised to discover how many people believed or disbelieved without checking the evidence. Hugh's unshakable confidence that God's revelations in Scripture and nature do not, will not, and cannot contradict became his unique message. Wholeheartedly encouraged by family and friends, communicating that message as broadly and clearly as possible became his mission. Thus, in 1986, he founded science-faith think tank Reasons to Believe (RTB). He and his colleagues at RTB keep tabs on the frontiers of research to share with scientists and nonscientists alike the thrilling news of what's being discovered and how it connects with biblical theology. In this realm, he has written many books, including: The Fingerprint of God, The Creator and the Cosmos, Beyond the Cosmos, A Matter of Days, Creation as Science, Why the Universe Is the Way It Is, and More Than a Theory. Between writing books and articles, recording podcasts, and taking interviews, Hugh travels the world challenging students and faculty, churches and professional groups, to consider what they believe and why. He presents a persuasive case for Christianity without applying pressure. Because he treats people's questions and comments with respect, he is in great demand as a speaker and as a talk-radio and television guest. Having grown up amid the splendor of Canada's mountains, wildlife, and waterways, Hugh loves the outdoors. Hiking, trail running, and photography are among his favorite recreational pursuits - in addition to stargazing. Hugh lives in Southern California with his wife, Kathy, and two sons.

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