44 Nysa
Encyclopedia
44 Nysa is a large and very bright main-belt asteroid
, and the brightest member of the Nysian asteroid family
. It is classified as a rare class E
asteroid and is probably the largest of this type (though 55 Pandora
is only slightly smaller).
on May 27, 1857, and named after the mythical land of Nysa
in Greek mythology
.
et al. used 63 lightcurves from the Uppsala Asteroid Photometric Catalog (UAPC) to construct a shape model of 44 Nysa. The shape model is conical, which they interpreted as indicating the asteroid may actually be a contact binary
.
In 2003, Tanga et al. published results obtained from the Fine Guidance Sensor
on the Hubble Space Telescope
in which high-precision interferometry was performed on Nysa with the goal of a more accurate shape determination. Due to Hubble's orbit around the Earth, hours-long photometry sessions, as are normally used to resolve the asteroid's shape, were not possible. Instead the team used interferometry on the asteroid at the time in its rotation when it would have its longest axis perpendicular to the Earth. Ellipsoidal shape models were then fit to the resulting data to determine an estimate of the asteroid's shape. Both single and double ellipsoid models were fit to the data with both providing approximately the same goodness of fit; leaving the team unable to differentiate between a single elongated object and the contact binary model put forth by Kaasalainen et al.
In December 2006, Shepard et al. performed three days of radar
observations on Nysa with the Arecibo radio telescope
. The asteroid was found to have a high radar polarization value (μc) of 0.50 ± 0.2, a radar albedo (
) of 0.19 ± 0.06, and a visual albedo (pv) of 0.44 ± 0.10. The albedo measurements were based on a shape model worked out at Arecibo. The best fit shape model as measured by the Arecibo team has parameters a/b = 1.7 ± 0.1, a/c = 1.6–1.9, with an a-axis of 113 ± 10 km; this gives an effective diameter of 79 ± 10 km, which is in agreement with the HST study by Tanga et al. in 2003. The data gathered also showed signs of significant concavity in Nysa's structure, but the dip in the radar curves is not pronounced enough to indicate bifurcation, calling into question whether or not Nysa really is a contact binary.
Nysa has so far been reported occulting
a star
twice.
Asteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...
, and the brightest member of the Nysian asteroid family
Nysa family
The Nysa or Nysian asteroids are a group of asteroids in the Main Belt orbiting the sun between 2.41 and 2.5 AU. Asteroids in this family have eccentricities between 0.12 and 0.21 and inclinations of 1.4 to 4.3...
. It is classified as a rare class E
E-type asteroid
E-type asteroids are asteroids thought to have enstatite achondrite surfaces. They form a large proportion of asteroids inward of the main belt known as Hungaria asteroids, but rapidly become very rare as the main belt proper is entered. There are, however, some that are quite far from the inner...
asteroid and is probably the largest of this type (though 55 Pandora
55 Pandora
55 Pandora is a fairly large and very bright main belt asteroid. Pandora was discovered by George Mary Searle on September 10, 1858 from the Dudley Observatory near Albany, NY. It was his first and only asteroid discovery....
is only slightly smaller).
Discovery
It was discovered by H. GoldschmidtHermann Mayer Salomon Goldschmidt
Hermann Mayer Salomon Goldschmidt was a German-French astronomer and painter who spent much of his life in France. He started out as a painter, but after attending a lecture by the famous French astronomer Urbain Le Verrier turned to astronomy...
on May 27, 1857, and named after the mythical land of Nysa
Nysa (mythology)
In Greek mythology, the mountainous district of Nysa, variously associated with Ethiopia, Libya, Tribalia, India or Arabia by Greek mythographers, was the traditional place where the rain nymphs, the Hyades, raised the infant god Dionysus, the "Zeus of Nysa"...
in Greek mythology
Greek mythology
Greek mythology is the body of myths and legends belonging to the ancient Greeks, concerning their gods and heroes, the nature of the world, and the origins and significance of their own cult and ritual practices. They were a part of religion in ancient Greece...
.
Physical properties
In 2002 KaasalainenMikko Kaasalainen
Mikko K.J. Kaasalainen is a Finnish applied mathematician and mathematical physicist. He is currently professor of mathematics at the department of mathematics at Tampere University of Technology...
et al. used 63 lightcurves from the Uppsala Asteroid Photometric Catalog (UAPC) to construct a shape model of 44 Nysa. The shape model is conical, which they interpreted as indicating the asteroid may actually be a contact binary
Binary asteroid
A binary asteroid is a system of two asteroids orbiting their common center of mass, in analogy with binary stars. 243 Ida was the first binary asteroid to be identified when the Galileo spacecraft did a flyby in 1993...
.
In 2003, Tanga et al. published results obtained from the Fine Guidance Sensor
Fine Guidance Sensor
The Fine Guidance Sensor is an interferometric instrument on board the Hubble Space Telescope that provides high-precision pointing information as input to the observatory's attitude control systems....
on the Hubble Space Telescope
Hubble Space Telescope
The Hubble Space Telescope is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4 meter aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared...
in which high-precision interferometry was performed on Nysa with the goal of a more accurate shape determination. Due to Hubble's orbit around the Earth, hours-long photometry sessions, as are normally used to resolve the asteroid's shape, were not possible. Instead the team used interferometry on the asteroid at the time in its rotation when it would have its longest axis perpendicular to the Earth. Ellipsoidal shape models were then fit to the resulting data to determine an estimate of the asteroid's shape. Both single and double ellipsoid models were fit to the data with both providing approximately the same goodness of fit; leaving the team unable to differentiate between a single elongated object and the contact binary model put forth by Kaasalainen et al.
In December 2006, Shepard et al. performed three days of radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
observations on Nysa with the Arecibo radio telescope
Arecibo Observatory
The Arecibo Observatory is a radio telescope near the city of Arecibo in Puerto Rico. It is operated by SRI International under cooperative agreement with the National Science Foundation...
. The asteroid was found to have a high radar polarization value (μc) of 0.50 ± 0.2, a radar albedo (
) of 0.19 ± 0.06, and a visual albedo (pv) of 0.44 ± 0.10. The albedo measurements were based on a shape model worked out at Arecibo. The best fit shape model as measured by the Arecibo team has parameters a/b = 1.7 ± 0.1, a/c = 1.6–1.9, with an a-axis of 113 ± 10 km; this gives an effective diameter of 79 ± 10 km, which is in agreement with the HST study by Tanga et al. in 2003. The data gathered also showed signs of significant concavity in Nysa's structure, but the dip in the radar curves is not pronounced enough to indicate bifurcation, calling into question whether or not Nysa really is a contact binary.Nysa has so far been reported occulting
Occultation
An occultation is an event that occurs when one object is hidden by another object that passes between it and the observer. The word is used in astronomy . It can also refer to any situation wherein an object in the foreground blocks from view an object in the background...
a star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
twice.
See also
- AubriteAubriteAubrites are meteorites named for Aubres, a small achondrite meteorite that fell near Nyons, France, in 1836. They are primarily composed of the orthopyroxene enstatite, and are often called enstatite achondrites...
- E-type asteroidE-type asteroidE-type asteroids are asteroids thought to have enstatite achondrite surfaces. They form a large proportion of asteroids inward of the main belt known as Hungaria asteroids, but rapidly become very rare as the main belt proper is entered. There are, however, some that are quite far from the inner...
- Hungaria familyHungaria familyThe Hungaria asteroids are a group of asteroids in the asteroid belt that orbit the Sun between 1.78 and 2.00 AU. The asteroids typically have a low eccentricity and an inclination of 16 to 34 degrees....
- 64 Angelina64 Angelina64 Angelina is a medium-sized main belt E-type asteroid discovered in 1861. It is an unusually bright form of E-type asteroid.-Discovery and naming:...
- 3103 Eger3103 Eger3103 Eger is an Apollo and Mars-crosser asteroid that was discovered in 1982, by Miklós Lovas. It was named after the city of Eger, Hungary.It makes eight approaches to Earth less than in the 20th and 21st centuries. The last close approach was in August 2006 at...
- 55 Pandora55 Pandora55 Pandora is a fairly large and very bright main belt asteroid. Pandora was discovered by George Mary Searle on September 10, 1858 from the Dudley Observatory near Albany, NY. It was his first and only asteroid discovery....
- 2867 Šteins2867 Šteins2867 Šteins is a small main-belt asteroid that was discovered in 1969 by N. S. Chernykh. It is named after Kārlis Šteins, a Latvian and Soviet astronomer...