Tucson - May 29, 2003
Astronomers announced this week early results of a prototype, three-telescope array of automated astronomical imagers. These have been used to discover new Solar System objects, as well as to discover and monitor the time variable brightness of stars, especially those potentially harboring extrasolar planets.
The report was presented Monday by Dr. Eric R. Craine of the Global Network of Astronomical Telescopes (GNAT), Tucson, Arizona to the American Astronomical Society meeting in Nashville, Tennessee.
The system is of special interest because of its very low cost, extremely high data output and application to myriad astronomical observations.
This array is named the Moving Object and Transient Event Search System (MOTESS). It was designed by Roy A. Tucker of Goodricke-Pigott Observatory (GPO), Tucson, Arizona.
It was originally implemented for discovery and astrometric measurement of asteroids, but it is also used as a large-scale, cost-effective photometric monitoring instrument with large volume data handling techniques developed under direction of Dr. Eric R. Craine and Mark S. Giampapa of the National Solar Observatory (NSO), Tucson, Arizona.
The prototype automated MOTESS observatory, located in Tucson, is a proof-of-principle system for a 48-telescope, globally distributed network planned by GNAT. During its first two years of automatic operation, MOTESS has yielded valuable observations of asteroids as well as stellar variability.
The MOTESS system is both cost-effective and productive. Costs for the telescope hardware are minimized through "scan-mode" operation, whereby each telescope in the array is pointed at a specific position in the sky with respect to the Earth.
The view of the sky seen by each telescope changes by virtue of the rotation of the Earth, thereby scanning the sky across the field of view of each instrument. With no moving parts in the hardware system, costs of the prototype system were held at under $20,000, a fraction of the cost of more traditional, comparable telescopes.
The telescopes make their observations automatically and continuously throughout the night, and hence remain unattended by human operators during that time.
Since the cameras make one long, uninterrupted exposure throughout the night, there is no deadtime for moving the telescopes to new positions or inactivating camera recording while individual images are read out.
Each image has a width nearly twice the full Moon's diameter, and about 10-12 hours of time long, thus typically covering about 200 square degrees on the sky per night, per telescope in the array.
During the course of a year, the system typically makes several observations per night of approximately 1.5 million stars, as well as hundreds of asteroids and transient events.
Asteroid searches with the MOTESS system involve acquisition of triplets of images of select regions of the sky, each telescope contributing one of the images of the triplet each night.
These images are aligned with respect to one another and they are alternately displayed in software such that moving objects are visually distinguished from the fixed background stars.
Detection of asteroids as faint as 20-21 magnitude is possible with this system. During the first year of observation, 290 newly discovered asteroids were measured.
Naming rights for over 180 new asteroids have accrued to the program. Experience with this system is leading to data handling software which is expected to provide automated detection of such asteroids.
The MOTESS system is presently accumulating a catalog of three brightness observations per night of the 1.5 million stars in its current observing list. These observations are repeated nightly throughout the year, enabling the creation of long-term light curves for each of these stars.
In the region of the sky along the celestial equator presently monitored, there are 179 known variable stars, all of which have been observed. In addition, examination of the light curves in this database indicate that there are approximately 55,000 newly discovered variable star candidates.
These include stars that vary periodically, either due to eclipses by companion stars or by intrinsic internal pulsations, as well as stars which vary irregularly over long periods of time.
The MOTESS system is a pioneering complement to other planned major survey instruments, and it is a valuable test-bed for developing techniques of handling large volumes of specialized astronomical images.
Combined discovery rates of asteroids as well as varyiable stars of many different types provides analysis opportunities which could occupy hundreds of students and researchers for many years to come.
The flow of MOTESS data will triple by Spring of 2004 with the implementation of six more telescopes in the emerging network of scan-mode systems. GNAT is actively seeking collaborators interested in studying and analyzing these interesting new objects.
Global Network of Astronomical Telescopes
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Newly-Discovered Star May Be Third-Closest
Pasadena - May 26, 2003
The local celestial neighborhood just got more crowded with a discovery of a star that may be the third closest to the Sun. The star, "SO25300.5+165258," is a faint red dwarf star estimated to be about 7.8 light-years from Earth in the direction of the constellation Aries.
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