Wolf 359

Also known as CN Leonis, CN Leo, GJ 406, G 045-020, LTT 12923, LFT 750, LHS 36, and GCTP 2553

     The next stop on our pilgrimage is a star named after one of the most remarkable and yet uncelebrated figures in astronomy, Max Wolf (1863-1932) of Heidelberg, Germany. Unlike so many other bright lights in the field, such as Copernicus, Kepler, Pickering, or Hubble, we cannot attribute any tremendous discovery or world-altering theory to him, yet by any standard Maximilian Franz Joseph Cornelius Wolf (“Max” to his friends) was a most amazing figure. Having earned his PhD from Heidelberg University by the age of 25, he spent nearly his entire career developing the then-new field of astrophotography. Working in close collaboration with the American E.E. Barnard, he pioneered the idea of creating photographic surveys of the entire sky. The two astronomers engaged in a friendly rivalry for many years, each trying to “scoop” the other in teasing new insights out of the mass of data they were jointly collecting. They shared the discovery that the mysterious “holes in the sky” which had so mystified generations of astronomers were actually dark nebulae. Whereas Barnard discovered the second-closest star system to our sun, which now bears his name (Barnard’s Star), Max Wolf discovered the third, which in turn bears his (and is the subject of this posting). The two friends competed to see who could be the first to observe Halley’s comet in 1910 (Wolf won the wager). Wolf also discovered the existence of the Trojan asteroids, which share an orbit around the sun with Jupiter, leading and trailing the planet by 60º.

     But Wolf’s two greatest contributions to astronomy were the invention of the planetarium, and his catalogue of more than 1500 stars with detectable proper motion. Just try to imagine the patience, diligence, and exacting precision needed to measure the almost undetectable changes in stellar position over time of so many stars, each one being the faintest of the faint points of light on (by today’s standards) primitive photographic plates. To this day, Wolf has credit for more such measurements than all other astronomers combined! And all without the aid of computerized data storage and processing. (Remember, all of his tens of thousands of individual data points had to be determined by sight, recorded by hand, and retrieved by cross-indexing hardcopy files, with all calculations being worked out longhand. Just try it!) To accomplish this task, Wolf also invented the “Blink Comparator”, with which Clyde Tombaugh would later discover the (then) planet Pluto in 1930. The star Wolf 359 is thus the 359th entry in his catalogue.

     At 7.78 ly distance, Wolf 359 is the second nearest star (other than a growing number of newly discovered "brown dwarfs") to the Sun visible from Maryland. Only Barnard’s star is closer. It is in many ways quite similar to CX Cancri, both having about 9% of the Sun’s mass and nearly identical surface temperatures (2800º Kelvin plus or minus 100 degrees). Its luminosity varies from 0.0009 to 0.0011 that of the Sun, which translates at its distance to an apparent magnitude of 13.54 from the Earth’s surface. Looks like we’re in for another observational challenge.

     There is little to distinguish Wolf 359 from the run of the mill red dwarf, other than the fact that it is a good example of one extreme of the type (as Lalande 21185 is of the other). It is about as low-mass as a star can be while still supporting proton-proton hydrogen fusion. With a diameter of 136,000 miles (220,000 km), it is actually smaller than many exoplanets recently discovered by the Kepler Space Telescope. (By comparison, Jupiter has a diameter of 88,846 miles at the equator.) Analysis of chemicals in the star’s photosphere indicates that Wolf 359 is quite young, most likely only about 100 million years old. Its exceptionally strong magnetic field (2,200 times that of the Sun) leads to wolf 359 being a fine example of a flare star, with as many as 16 flare episodes per hour being observed.

     In contrast to Lalande 21185’s “faster than a speeding bullet” approach, Wolf 359 is receding from the sun at a rate of 11 miles per second, traveling in a direction nearly perpendicular the galactic plane.

     Wolf 359, probably because of its proximity to the solar system, has acquired some small amount of fame in the world of science fiction, being a favored location in novels, movies, and even in video games. Most notably, it was the site of a major battle in the Federation’s war against the alien Borg in Star Trek: The Next Generation. The battle was a major defeat for the Federation, resulting in a loss of 39 ships and 11,000 lives, thanks to Captain Jean-Luc Picard’s assimilation by the enemy (thus giving the Borg access to all his knowledge of Federation weaponry and tactics).

What Wolf 239 looked like to me on 27 March 2012.

(See faint red dot below the name of the star.
Click on image to get full resolution.)