44 Nysa is a large and very bright main-belt

asteroid An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...

, 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 55 Pandora is a fairly large and very bright asteroid in the asteroid belt. Pandora was discovered by American astronomer and Catholic priest George Mary Searle on September 10, 1858, from the Dudley Observatory near Albany, NY. It was his f ...

is only slightly smaller).

Discovery

It was discovered by Hermann Goldschmidt on May 27, 1857, and named after the mythical land of Nysa in

Greek mythology Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of ancient Greek folklore, today absorbed alongside Roman mythology into the broader designation of classical mythology. These stories conc ...

Physical properties

In 2002 Kaasalainen ''et al.'' used 63

lightcurve In astronomy, a light curve is a graph (discrete mathematics), graph of the Radiance, light intensity of a celestial object or region as a function of time, typically with the magnitude (astronomy), magnitude of light received on the ''y''-axis ...

s 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 The Hubble Space Telescope (HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the Orbiting Solar Observatory, first space telescope, but it is one of the largest and most ...

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.'' An observation of an occultation by 44 Nysa of TYC 6273-01033-1 from the Dutch amateur astronomer Harrie Rutten showed a two-phase reappearance on March 20, 2012. This confirms the conical shape or the binary nature of Nysa. In December 2006, Shepard ''et al.'' performed three days of

radar Radar is a system that uses radio waves to determine the distance ('' ranging''), direction ( azimuth and elevation angles), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track ...

observations on Nysa with the Arecibo radio telescope. The asteroid was found to have a high radar polarization value (''μ_c'') of 0.50 ± 0.2, a radar albedo (

\hat_

) of 0.19 ± 0.06, and a visual albedo (''p_v'') 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 A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

three times.

Studies

44 Nysa was in a study of asteroids using the Hubble FGS. Asteroids studied include 63 Ausonia, 15 Eunomia,

43 Ariadne 43 Ariadne is a fairly large and bright main-belt asteroid. It is the second-largest member of the Flora asteroid family. It was discovered by N. R. Pogson on 15 April 1857 and named after the Greek heroine Ariadne. Characteristics Ariadne ...

, 44 Nysa, and 624 Hektor.

Notes

References

External links

* * {{DEFAULTSORT:000044 Nysa asteroids Nysa Nysa E-type asteroids (Tholen) Xc-type asteroids (SMASS) 18570527 vec:Lista de asteroidi#44 Nisa