Universe Today
One of the most fascinating stories in modern astronomy involves the pursuit of a world that never was.
Tomorrow marks the 135
th
anniversary of the total solar eclipse of
July 29th, 1878
. With a maximum totality of 3 minutes 11 seconds, this eclipse traced a path across western Canada and the United States from the territory of Montana to Louisiana.
A curious band of astronomers also lay in wait along the path of totality, searching for an elusive world known as Vulcan.
Long before
Star Trek
or Mr. Spock,
Vulcan
was a hypothetical world thought to inhabit the region between the planet Mercury and the Sun.
The tale of Vulcan is the story of the birth of modern predictive astronomy. Vulcan was a reality to 18
th
century astronomers- it can be seen and the astronomy textbooks and contemporary art and culture of the day.
Urbain J.J. Le Verrier
proposed the existence of the planet in 1859 to explain the anomalous precession of the perihelion of the planet Mercury. Le Verrier was a voice to be taken seriously — he had performed a similar feat of calculation to lead observers to the discovery of the planet Neptune from the Berlin Observatory on the night of September 23, 1846. Almost overnight, Le Verrier had single-handedly boosted astronomy into the realm of a science with real predictive power.
[caption id="attachment_103732" align="alignnone" width="380"]
An 1863 photograph of Lescarbault's country house observatory. (Wikimedia Commons
image
in the public domain).[/caption]
The idea of Vulcan gained traction when a French doctor and amateur astronomer
Edmond Lescarbault
claimed to have seen the tiny world transit the Sun while viewing it through his 95 millimetre refractor on the sunny afternoon of March 26
th
, 1859. Keep in mind, this was an era when solar observations were carried out via the hazardous method of viewing the Sun through a smoked or oil-filled filter, or the via safer technique of projecting the disk and sketching it onto a piece of paper.
[caption id="attachment_103733" align="alignnone" width="580"]
A early right-angle solar viewer from Robert Ariail collection at the
South Carolina State Museum
in Columbia, South Carolina. Note the vent holes in the back to dissipate heat, and word SUN stenciled on the side! (Photo by author).[/caption]
A visiting Le Verrier was sufficiently impressed by Lescarbault's observation, and went as far as to calculate and publish orbital tables for Vulcan. Soon, astronomers everywhere were "seeing dots" pass in front of the Sun. Astronomer F. A. R. Russell spotted an object transiting the Sun from London on January, 29
th
, 1860. Sightings continued over the decades, including a claim by an observer based near Peckeloh Germany to have witnessed a transit of Vulcan on April 4
th
, 1876.
Incidentally, we are not immune to this effect of "contagious observations" even today — for example, when
Comet Holmes
brightened to naked eye visibility in October 2007, spurious reports of
other
comets brightening flooded message boards, and a similar psychological phenomena occurred after amateur astronomer
Anthony Wesley
recorded an impact on Jupiter in 2010. Though the event that triggered the initial observation was real, the claims of impacts on other bodies in the solar system that soon followed turned out to be bogus.
[caption id="attachment_103746" align="alignnone" width="580"]
Possible "target zone" for the existence of Vulcan, and later Vulcanoid asteroids. (
Graphic
in the public domain).[/caption]
Still, reports of the planet Vulcan were substantial enough for astronomers to mount an expedition to the territory of Wyoming in an attempt to catch dim Vulcan near the Sun during the brief moments of totality. Participants include Simon Newcomb of the Naval Observatory, James Craig Watson and Lewis Swift. Inventor
Thomas Edison
was also on hand, stationed at Rawlins, Wyoming hoping to test his new-fangled invention known as a
tasimeter
to measure the heat of the solar corona.
Conditions were austere, to say the least. Although the teams endured dust storms that nearly threatened to cut their expeditions short, the morning of the 29
th
dawned, as one
newspaper reported
, "as slick and clean as a Cheyenne free-lunch table." Totality began just after 4 PM local, as observers near the tiny town of Separation, Wyoming swung their instruments into action.
Such a quest is difficult under the best of circumstances. Observers had to sweep the area within 3 degrees of the Sun (six times the diameter of a Full Moon) quickly during the fleeting moments of totality with their narrow field refractors, looking for a +4
th
magnitude star or fainter among the established star fields.
[caption id="attachment_103744" align="alignnone" width="502"]
Map of the path of the total solar eclipse of
July 29th, 1878
. (Credit: Fred Espenak/NASA/GSFC).[/caption]
In the end, the expedition was both a success and a failure. Watson & Swift both claimed to have identified a +5
th
magnitude object similar in brightness to the nearby star Theta Cancri. Astronomer Christian Heinrich Friedrich Peters later cast doubt on the sighting and the whole Vulcan affair, claiming that "I refuse to go on a wild goose chase after Le Verrier's mythical birds!"
And speaking of birds, Edison ran into another eclipse phenomenon while testing his device, when
chickens
, fooled by the approaching false dusk came home to roost at the onset of totality!
[caption id="attachment_103745" align="alignnone" width="546"]
Vulcan search map for the Smithsonian Observatory's 1900 eclipse expedition. (From the collection of
Michael Zeiler
@EclipseMaps
, used with permission).[/caption]
But such is the life of an eclipse-chaser. Albert Einstein's general theory of relativity
explained
the precession of Mercury's orbit in 1916 and did away with a need for Vulcan entirely.
But is the idea of intra-Mercurial worldlets down for the count?
[caption id="attachment_103739" align="alignnone" width="580"]
The search strategy for NASA's high-altitude mission to hunt for Vulcanoids in 2002. (Credit:
NASA/Dryden
).[/caption]
Amazingly, the quest for objects inside Mercury's orbit goes on today, and the jury is still out. Dubbed
Vulcanoids
, modern day hunters still probe the inner solar system for tiny asteroids that may inhabit the region close to the Sun. In 2002, NASA conducted a
series of high altitude flights
out of the Dryden Flight Research Center at Edwards Air Force Base, California, sweeping the sky near the Sun for Vulcanoids at dawn and dusk. Now, there's a job to be envious of — an F-18 flying astronomer!
[caption id="attachment_103737" align="alignnone" width="580"]
One of NASA's fleet of high-performance F-18 aircraft. (Credit:
NASA
).[/caption]
NASA's MESSENGER spacecraft was also on the
lookout
for Vulcanoids on its six year trek through the inner solar system prior to orbital insertion on March 18
th
, 2011.
Thus far, these hunts have turned up naught. But one of the most
fascinating quests
is still ongoing and being carried out by veteran eclipse-chaser Landon Curt Noll.
Mr. Noll last conducted a sweep for Vulcanoids during total phases of the long duration total solar eclipse of July 22
nd
, 2009 across the Far East. He uses a deep sky imaging system, taking pictures in the near-IR to accomplish this search. Using this near-IR imaging technique during a total solar eclipse requires a stable platform, and thus performing this feat at sea or via an airborne platform is out. Such a rig has been successful in catching the extremely thin crescent Moon at the moment it reaches New phase.
[caption id="attachment_103741" align="alignnone" width="428"]
Mr. Noll explains the aspects of an eclipse during a 2006 expedition to Libya. (Coutesy of
Landon Curt Noll
, used with permission).[/caption]
To date, no convincing Vulcanoid candidates have been found. Mr. Noll also notes that the European Space Agency/NASA's joint
Solar Heliospheric Observatory
(SOHO) spacecraft has, for all intents and purposes, eliminated the possibility of Vulcanoids brighter than +8
th
magnitude near the Sun. Modern searches during eclipses conducted in this fashion scan the sky between wavelengths of 780 to 1100 nanometres down to magnitude +13.5. Mr. Noll told
Universe Today
that "Our improved orbital models show that objects as small as 50m in diameter could reside in a zone 0.08 A.U. to 0.18 AU (1.2 to 2.7 million kilometers) from the Sun." He also stated that, "there is plenty of 'room' for (Vulcanoids) in the 50 metre to 20 kilometre range."
[caption id="attachment_103742" align="alignnone" width="525"]
The modern day Vulcanoid search strategy. (Diagram courtesy of Landon Curt Noll, used with permission).[/caption]
Mr. Noll plans to resume his hunt during the
August 21st, 2017
total solar eclipse spanning the continental United States. Totality for this eclipse will have a maximum duration of 2 minutes and 40 seconds. Circumstances during the next solar eclipse (a hybrid annular-total crossing central Africa on November 3
rd
, 2013) will be much more difficult, with a max totality located out to sea of only 1 minute and 40 seconds.
[caption id="attachment_103743" align="alignnone" width="580"]
Mr. Noll talks with a local reporter during the 2006 total solar eclipse expedition to Libya. (Photograph courtesy of
Landon Curt Noll
, used with permission).[/caption]
Still, we think it's amazing that the quest for Vulcan (or at least Vulcanoids) is alive and well and being spearheaded by adventurous and innovative amateur astronomers. In the words of Vulcan's native fictional son, may it "Live Long & Prosper!"
- Read more about
Edison vs. the Chickens & the eclipse of 1878 here
.
- For a fascinating read on the subject, check out
In Search for planet Vulcan
.
- Read more of Mr. Noll's fascinating
search for Vulcanoids here
.