Nearly 89 years after its original discovery, the long-lost asteroid (719) Albert has finally been reobserved. With this finding, it can safely be said that the current position is known of every one of the 14,788 asteroids in the numbered sequence that began with the discovery of (1) Ceres in 1801.
Albert, or "MT", as it was initially known, was discovered visually by Johann Palisa at the Vienna Observatory on the night of October 3-4, 1911. It was also seen at the Copenhagen Observatory the following night. From these observations it was clear that the object was very roughly 20 million miles from the Earth. After (433) Eros, discovered in 1898, Albert was only the second asteroid then known to come that close. Although faint traces of Albert were found on photographs deliberately exposed for it two weeks after discovery, the only other data useful for the orbit computation came from accidental images later recognized on photographs taken at observatories in Germany and England on September 16 and October 11. This computation suggested that Albert had been at its closest to the Sun, 110 million miles, in late August and that it orbited the Sun in a period of about 4.1 years.
But that also means that Albert spends most of its time 300 million miles or more from the Sun. If it were difficult to observe in 1911, when it was close, there was little hope it would be bright enough to detect at other times. A photographic search was in fact made for Albert in February 1913 with the Crossley reflector at the Lick Observatory. Even though this 36-inch telescope at a fine California site was then one of the best in the world for the job, the exposures of up to 160 minutes would not have been sufficient then to record the object. In any case, it is now known that the telescope was not pointing at the correct location. There seemed to be a more promising opportunity in 1915, a full orbital revolution after the discovery, but the uncertainty in the period--perhaps it was 4.2 years, not 4.1--meant that there was too much sky to search.
It is now evident that the orbital period is really 4.28 years. This is known because, earlier this month, Albert was, at last, again under observation. It was identified by the International Astronomical Union's Minor Planet Center (MPC), located at the Smithsonian Astrophysical Observatory, in Cambridge, Massachusetts. The MPC was analyzing recent data from the Spacewatch asteroid survey project, observing with the 36-inch telescope of the University of Arizona's Steward Observatory on Kitt Peak mountain in the Tohono O'odham Nation, Arizona. This project is one of four or five around the world that regularly scan the sky electronically for asteroids that can come close to the Earth, often nowadays much closer than is possible for Albert. Gareth V. Williams, the Associate Director of the MPC, has been vigilant in checking the frequent new discoveries of Earth-approaching asteroids by all the survey groups for the purpose of seeing if they link with asteroids discovered earlier.
The Spacewatch Project is a survey of the whole solar system, from the vicinity of the Earth's orbit all the way out to beyond the orbit of Neptune. It was begun in 1980 by Tom Gehrels and Robert S. McMillan at the Lunar and Planetary Laboratory of The University of Arizona. More information about Spacewatch can be found on the web site: http://www.lpl.arizona.edu/spacewatch/.
The object that turned out to be the lost Albert was detected by Jeffrey A. Larsen during his observing shift on May 1 while he was recovering another potentially interesting asteroid. Larsen reobserved the new target the same night and passed on the candidate to McMillan, whose shift followed his, and to James V. Scotti later. At the time of observation the observer does not necessarily know whether an object is already known, and that was certainly the case with this object, to which the MPC later gave the designation 2000 JW8.
Gareth Williams has dreamt about finding the lost asteroid (719) Albert since he was still in school in England. His work on identifications of asteroids, and particularly in the main belt of asteroids that orbit the Sun between Mars and Jupiter, brought Williams to the attention of MPC Director Brian G. Marsden. As recently as the late 1970s, more than 20 of the then-2000 asteroids in the numbered sequence were lost. At the time Williams joined the MPC staff in 1990, all but two of the lost numbered asteroids had been found. A year or so later, Williams was able to identify (878) Mildred in recent images. Down to only one lost numbered asteroid, Williams checked every asteroid reported to the MPC in hopes of spotting the long-lost Albert.
After a short arc of observations, the plane of an asteroid's orbit can be reasonably well defined and the shape of the orbit can be determined with additional observations. In the case of Albert, the observations covered about one month. Williams was able to narrow down his search to asteroids that were in the plane of Albert's orbit. He also knew that Albert would be bright, as seen from the Earth, if it came to perihelion, or was at its closest to the Sun, in late August, as in 1911, but that a perihelion during much of the rest of the year could keep the object then behind the Sun for months on end, and that by the time it had moved out from the Sun's rays it would be far away and very faint. Any asteroid near the plane of Albert's orbit was suspect, particularly if it moved like an Earth Approaching asteroid, also called by a Near-Earth Object (NEO).
The object found by Spacewatch had certainly been unusual enough to warrant placing it in the MPC's NEO Confirmation Page: http://cfa-www.harvard.edu/iau/NEO/ToConfirm.html
As a result, astronomer Michael Hicks and a colleague imaged it using the 84-inch telescope, also on Kitt Peak, on May 9. It was later that day, as Williams was putting together the information on 2000 JW8 for a more formal publication on a Minor Planet Electronic Circular, that he paid attention to the orbit plane. "That looks an awful lot like Albert's", he thought to himself. Over the course of the next hour, he attempted to link the observations of 2000 JW8 together with the 1911 observations of Albert into a single orbit calculation. This was easier said than done, because although the quality of the 2000 data was much greater than those of 1911, the 1911 data better determine the orbit, once one knows which are the bad observations that should be removed. Furthermore, there were some moderately strong perturbations by Jupiter, which passed some 130 million miles from Albert in 1956. Williams showed his calculations to Marsden, who in a matter of moments was convinced that the linkage was 100-percent certain.
The Spacewatch rediscovery images were made when Albert was just moving in from its most distant, or the aphelion point of its orbit. At a distance of some 260 million miles from the Earth and 330 million miles from the Sun, it had a magnitude of 21.6, near the detection limit of Spacewatch. By going extremely faint, Spacewatch, despite its covering a relatively small area of sky, can reach far out into the solar system, while other surveys that do not go so faint can only see Earth approaching asteroids when they are relatively close by.
Although Albert's orbital period changes slightly because of the planetary perturbations, it is remarkable how close it is to four and two-sevenths years, particularly in the early years after discovery. This means that seven revolutions of Albert about the Sun take just 30 years--very precisely so between 1911 and 1941, when the object would again have had the same brightness, sky position and minimum distance of 19 million miles from the Earth. Albert escaped detection in 1941, probably because most of the astronomers who might otherwise have observed it were involved in less peaceful activities. It would have been a little farther away and fainter in 1971. It is somewhat more surprising that Albert was not observed in that year, although it was a little before the current interest in NEOs really got going, even though Gehrels had just discovered the Earth-approacher (1864) Daedalus, and the Czech-German astronomer Lubos Kohoutek then found (1865) Cerberus.
The 30-year cycle also means that Albert will be close and bright again in 2001. It comes to a distance of 27 million miles on September 5 next year, allowing an excellent opportunity for careful study. That study could include a determination of its size, rotation period and other physical characteristics. At present, Albert's estimated 2-mile diameter is scarcely more than a guess. Given the collective success of modern search programs it is hard to believe that Albert would not have been found by accident on its pass next year, but the rediscovery so conveniently a year or more ahead will instead allow careful planning of the observations then.
Albert was named in 1913 in honor of Baron Albert Freiherr von Rothschild, a benefactor of the Vienna Observatory. For the foreseeable future, he cannot come much closer to the Earth than he did in 1911 and 1941.
An Image of (719) Albert
The following image of (719) Albert was subsequently located by Andrew Lowe,
on a Siding Spring photographic plate taken on 1988 Aug. 2 and digitized
Observatory. Albert is the trailed object to the lower-right of the
center of the image. The trail is caused principally by the motion of Albert
during the exposure of the photographic plate. At the time
of the exposure, Albert was some 80 million miles from the earth,
in the constellation Serpens Caput.
Financial support for the Spacewatch Project is summarized on its web site.
The MPC computations were carried out using the Tamkin Foundation Computer Network.
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