Now’s the Time to See Asteroid Pallas at its Best

Looking for something off of the beaten celestial path to observe? The coming weeks will offer telescope users a rare chance to catch a well known asteroid, as it puts on its best show for over two decades.

Over the coming weeks, 2 Pallas, one of the “big four” asteroids – or do you say minor/dwarf planet/planetoid? – reaches a favorable observing point known as opposition. Gliding northward through the constellations of Hydra and Sextans through February and March 2014, 2 Pallas presents a favorable binocular challenge for both northern and southern hemisphere observers as it rises to the east opposite to the setting Sun and transits the local meridian around midnight.

And although 2 Pallas reaches opposition roughly every 16 months as seen from our Earthly vantage point, 2014 provides a chance to catch it under exceptional circumstances. And to top it off, the other “Big 4” asteroids – 1 Ceres, 3 Juno and 4 Vesta – are all currently visible as well and reach opposition in the January through April time frame.

Pallas HST
2 Pallas as imaged by the Hubble Space Telescope. Credit: NASA

Pallas and its brethren also have a checkered history though the course of 19th century astronomy.  The second minor planet to be discovered, Heinrich Wilhelm Olbers spied 2 Pallas near opposition on the night of March 28th, 1802. Olbers made this discovery observing from his home rooftop observatory in Bremen, Germany using a five foot – telescopes were often measured in focal length rather than aperture in those days – Dollond refractor.

Olbers discovered 2 Pallas on the border of the astronomical constellations of Virgo and Coma Berenices shining at magnitude +7.5.

Pallas orbit
A simulation of the orbit of 2 Pallas near opposition this month. Credit: NASA/JPL Horizons.

If the name Olbers sounds familiar, it’s because he also lent it to the paradox that now bears his name. Obler’s paradox was one of the first true questions in cosmology posed in a scientific framework that asked: if the universe is actually infinite in time and space, then why isn’t the sky infinitely bright? And, on a curious side note, it was American horror author Edgar Allan Poe that delivered the answer.

But now back to our solar system. Olbers also discovered 4 Vesta just five years after Pallas.

He was definitely on a roll. The discoveries of these space rocks also grabbed the attention of Olbers contemporary, Johann Bode. Bode had formulated a law now known as the Titus-Bode Law that seemed to put the spacing of then known bodies of the solar system in tidy order. In fact, the Titus-Bode law seemed to predict that a body should lie between Mars and Jupiter, and for a brief time in the 18th century — and again in 2006 when the International Astronomical Union let Eris and Pluto in the door before kicking them back out — Ceres, Pallas, Juno and Vesta were all considered planets.

Comparison
A size comparison of the first ten asteroids discovered compared to Earth’s moon. Wikimedia Commons graphic in the Public Domain.

Today, we now know that 2 Pallas is a tiny world about 575 kilometres in diameter. 2 Pallas orbits the Sun once every 4.62 years and has a relatively high inclination of 34.8 degrees relative to the ecliptic. Pallas has no confirmed satellites, though one was once hinted at during a May 29th, 1979 stellar occultation. And though we’ve yet to send a mission to examine Pallas up close, there were early planning considerations to send NASA’s Dawn spacecraft there after its visit to 1 Ceres.

wide
The path of 2 Pallas from February 16th though March 21st. Created by the author using Stellarium.

This month, look for 2 Pallas as a +7th magnitude wandering star at dusk. Mid-February finds 2 Pallas in the constellation Hydra, and it crosses briefly into Sextans starting on March 22nd until it passes just three degrees east of the 2nd magnitude Alphard (Alpha Hydrae) on March 1st, making a good guidepost to find it at its brightest.

2 Pallas last broke +7th magnitude visibility as seen from Earth in 1991 and won’t do so again til 2028. This is because 18.5 Earth years very nearly equals four orbits of Pallas around the Sun, bringing the two worlds back “into sync.” According to calculations by Belgian astronomer Jean Meeus, the 2014 opposition season offers the closest passage to Earth for Pallas from 1980-2060. Pallas can appear at a maximum brightness of magnitude +6.5 — just on the threshold of naked eye visibility — as seen from Earth.

Narrow
A narrow field finder chart  for 2 Pallas with sample comparison magnitudes, decimal points omitted. Created by the author using Stellarium.

Opposition for Pallas occurs on February 22nd, 2014, when the asteroid is 1.23 AUs distant from our fair planet. Watch for 2 Pallas near opposition this year moving at just under half a degree a day — about the diameter of the Full Moon — headed northward at closest approach.

Hunting asteroids at the eyepiece can be a challenge, as they visually resemble pinpoint stars and show no apparent disks even at high magnification. Sketching or photographing the field of view on successive nights is a fun and easy way to cross this object off of your life list. For those who own scopes with digital setting circles, Heavens-Above is a great quick look source for current coordinates.

2 Pallas just passed perihelion at 2.13 Astronomical Units from the Sun on December 6th, 2013, and passes closest to Earth on February 24th at 1.2 A.U.s distant.

Don’t miss the chance to spy this fascinating an enigmatic worldlet coming to a sky near you this season!

-Got pics of 2 Pallas and friends? Be sure to send ‘em in to Universe Today!

A Weird West Tale and the Hunt for Planet Vulcan

One of the most fascinating stories in modern astronomy involves the pursuit of a world that never was.

Tomorrow marks the 135th 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 18th 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.

An 1863 photograph of Lescarbault's country house observatory. (Wikimedia Commons image in the public domain).
An 1863 photograph of Lescarbault’s country house observatory. (Wikimedia Commons image in the public domain).

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 26th, 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.

A early right-angle solar viewer from the South Carolina State Museum in Columbia, South Carolina. Note the vent holes in the back to disappate heat and word SUN stenciled on the side! (Photo by author).
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).

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, 29th, 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 4th, 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.

Possible "target zone" for the existence of Vulcan, and later Vulcanoid asteroids.
Possible “target zone” for the existence of Vulcan, and later Vulcanoid asteroids. (Graphic in the public domain).

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 29th 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 +4th magnitude star or fainter among the established star fields.

Map of the path of the total solar eclipse of July 29th, 1878. (Credit: Fred Espenak/NASA/GSFC).
Map of the path of the total solar eclipse of July 29th, 1878. (Credit: Fred Espenak/NASA/GSFC).

In the end, the expedition was both a success and a failure. Watson & Swift both claimed to have identified a +5th 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!

Vulcan search map for the Smithsonian Obervatory's 1900 eclipse expedition. (From the collection of Michael Zeiler @EclipseMaps, used with permission).
Vulcan search map for the Smithsonian Observatory’s 1900 eclipse expedition. (From the collection of Michael Zeiler @EclipseMaps, used with permission).

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?

The search strategy for NASA's high-altitude mission to hunt for Vulcanoids in 2002. (Credit: NASA/Dryden).
The search strategy for NASA’s high-altitude mission to hunt for Vulcanoids in 2002. (Credit: NASA/Dryden).

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!

One of NASA's fleet of high-performance F-18 aircraft. (Credit: NASA).
One of NASA’s fleet of high-performance F-18 aircraft. (Credit: NASA).

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 18th, 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 22nd, 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.

Libya
Mr. Noll explains the aspects of an eclipse during a 2006 expedition to Libya. (Coutesy of Landon Curt Noll, used with permission).

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 +8th 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.”

Vulcanoid search diagram
The modern day Vulcanoid search strategy. (Diagram courtesy of Landon Curt Noll, used with permission).

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 3rd, 2013) will be much more difficult, with a max totality located out to sea of only 1 minute and 40 seconds.

Libyan 2
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).

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.

Remembering the Great Meteor Procession of 1860

“Year of meteors! Brooding year!”

 -Walt Whitman

July 20th is a red letter date in space history. Apollo 11, the first crewed landing on the Moon, took place on this day in 1969. Viking 1 also made the first successful landing on Mars, seven years later to the day in 1976.

A remarkable astronomical event also occurred over the northeastern United States 153 years ago today on the night of July 20th, known as the Great Meteor Procession of 1860. And with it came a mystery of poetry, art and astronomy that was only recently solved in 2010.

A meteor procession occurs when an incoming meteor breaks up upon reentry into our atmosphere at an oblique angle. The result can be a spectacular display, leaving a brilliant glowing train in its wake. Unlike early morning meteors that are more frequent and run into the Earth head-on as it plows along in its orbit, evening meteors are rarer and have to approach the Earth from behind. In contrast, these often leave slow and stately trains as they move across the evening sky, struggling to keep up with the Earth.

The Great Meteor Procession of 1860 also became the key to unlock a 19th century puzzle as well. In 2010, researchers from Texas University San Marcos linked the event to the writings of one of the greatest American poets of the day.

Whitman...
Photograph of Walt Whitman taken by Mathew Brady circa 1860 (Library of Congress image in the Public Domain)..

Walt Whitman described a “strange, huge meteor-procession” in a poem entitled “Year of Meteors (1859-60)” published in his landmark work Leaves of Grass.

English professor Marilynn S. Olson and student Ava G. Pope teamed up with Texas state physics professors Russell Doescher & Donald Olsen to publish their findings in the July 2010 issue of Sky & Telescope.

As a seasoned observer, Whitman had touched on the astronomical in his writings before.

The event had previously been attributed over the years to the Great Leonid Storm of 1833, which a young Whitman would’ve witnessed as a teenager working in Brooklyn, New York as a printer’s apprentice.

Researchers noted, however, some problems with this assertion.

The stanza of contention reads;

Nor forget I sing of the wonder, the ship as she swam up my bay,

Well-shaped and stately, the Great Eastern swam up my bay, she was 600 feet long,

Her moving swiftly surrounded by myriads of small craft I forget not to sing;

Nor the comet that came unannounced out of the north flaring in heaven,

Nor the strange huge meteor-procession dazzling and clear shooting over our heads.

(A moment, a moment long, it sail’d its balls of earthly light over our heads,

Then departed, dropt in the night, and was gone.)

In the poem, the sage refers to the arrival of the Prince of Wales in New York City on October 1860. The election of Abraham Lincoln in November of that same year is also referred to earlier in the work.  Whitman almost seems to be making a cosmic connection similar to Shakespeare’s along the lines of “When beggars die, no comets are seen…

Path of the Meteor Procession of 1860 as depicted in the newspapers of the day. (From the collection of Don Olson).
Path of the Meteor Procession of 1860 as depicted in the newspapers of the day. (From the collection of Don Olson).

The “comet that came unannounced” is easily identified as the Great Comet of 1860. Also referred to as Comet 1860 III, this comet was discovered on June 18th of that year and reached +1st magnitude that summer as it headed southward. The late 19th century was rife with “great comets,” and northern hemisphere observers could look forward to another great cometary showing on the very next year in 1861.

The Great Comet of 1861 as drawn by G. Williams on June 30th, 1861. (From Descriptive Astronomy by George Chambers, 1877)
The Great Comet of 1861 as drawn by G. Williams on June 30th, 1861. (From Descriptive Astronomy by George Chambers, 1877)

There are some problems, however with the tenuous connection between the stanza and the Leonids.

The 1833 Leonids were one of the most phenomenal astronomical events ever witnessed, with estimates of thousands of meteors per second being seen up and down the U.S. Eastern Seaboard the morning of November 13th. Whitman himself described the event as producing;

“…myriads in all directions, some with long shining white trains, some falling over each other like falling water…”

Keep in mind, many startled townsfolk assumed their village was on fire on that terrifying morning in 1833, as Leonid bolides cast moving shadows into pre-dawn bedrooms. Churches filled up, as many thought that Judgment Day was nigh. The 1833 Leonids may have even played a factor in sparking many of the religious fundamentalist movements of the 1830s. We witnessed the 1998 Leonids from Kuwait, and can agree that this meteor shower can be a stunning sight at its peak.

But Whitman’s poem describes a singular event, a “meteor-procession” very different from a meteor shower.

Various sources have tried over the years to link the stanza to a return of the Leonids in 1858. A note from Whitman mentions a “meteor-shower, wondrous and dazzling (on the) 12th-13th, 11th month, year 58 of the States…” but keep in mind, “year 1” by this reckoning is 1776.

A lucky break came for researchers via the discovery of a painting by Frederic Church entitled “The Meteor of 1860.” This painting and several newspaper articles of the day, including an entry in the Harpers Weekly, collaborate a bright meteor procession seen across the northeastern U.S. from New York and Pennsylvania across to Wisconsin.

Such a bright meteor entered the atmosphere at a shallow angle, fragmented, and most likely skipped back out into space. Similar meteor processions have been observed over the years over the English Channel on August 18th, 1783 & across the U.S. Eastern Seaboard and Canada on February 9th, 1913.

On August 10th, 1972, a similar bright daylight fireball was recorded over the Grand Tetons in the western United States. Had the Great Meteor Procession of 1860 come in at a slightly sharper angle, it may have triggered a powerful airburst such as witnessed earlier this year over Chelyabinsk, Russia the day after Valentine’s Day.

The 1860 Meteor Procession is a great tale of art, astronomy, and mystery. Kudos to the team of researchers who sleuthed out this astronomical mystery… I wonder how many other unknown stories of historical astronomy are out there, waiting to be told?