2:00 PM - 2:15 PM
[PPS03-14] Spectroscopic observation of the target of Hayabusa2# 1998 KY26
Keywords:Asteroids, Hayabusa2, Telescopic observation
Following its successful mission to asteroid Ryugu and the return of precious samples to Earth, the Japanese spacecraft Hayabusa2 embarked on a new extended mission. Its current target is the near-Earth asteroid 1998 KY26, a fascinating celestial body notable for its diminutive size and rapid rotation. Estimated to be approximately 30 meters in diameter, 1998 KY26 spins on its axis at an astonishing rate of roughly 10 minutes per rotation [1]. This rapid spin presents unique challenges and opportunities for scientific investigation.
Despite its discovery in 1998, favorable viewing windows for 1998 KY26 are infrequent. April and May of 2024 presented the first such optimal opportunity for observation in over two decades. Seizing this chance, we conducted spectroscopic observations of 1998 KY26 using the 10.4-meter Gran Telescopio Canarias (GTC). Located at the Roque de los Muchachos Observatory on the island of La Palma in the Canary Islands, Spain, the GTC is one of the largest and most advanced optical and infrared telescopes in the world. The spectroscopic data provides valuable insights into the asteroid's surface composition, potentially revealing its origin and evolutionary history.
1998 KY26 was observed on the night of May 21st, 2024, at 04:14 UTC. Spectroscopic observations were done using the OSIRIS camera-spectrograph installed at GTC under the program GTC37-24A (PI, J. de León). OSIRIS is equipped with a blue-sensitive monolithic 4096x4096 CCD that provides a field of view of 7.8’x7.8’. We used the R300R grism that covers a wavelength range from 0.48 to 0.92 microns with a dispersion of 7.74A/pixel for a 0.6” slit. We combined the R300R grism with a slit of 1.2”, oriented to the parallactic angle and with the telescope tracking rate set to match the asteroid’s proper motion. Two consecutive spectra of 900 s of exposure, at an airmass of 1.36 were obtained. To get the asteroid’s reflectance spectrum, we also observed solar analog star Landolt SA112-1333, using the same instrumental setup and at a similar airmass to that of the asteroid. At the moment of the observations, 1998 KY26 presented an apparent visual magnigutde of mV=20.4, a phase angle of 29.7deg, and was at a distance of 1.053 au and 0.047 au from the Sun and the Earth, respectively.
To obtain the asteroid taxonomical classification, we used the M4AST online tool (Popescu et al. 2012). This tool fits a curve to the data and compares it to the taxon defined by DeMeo et al. (2009) using a chi^2 fitting procedure. The best fitted was Xe-class, a subclass of X-complex asteroids. The Xe-class asteroids are characterized by a broad absorption band around 0.49 µm. However, the absorption in the reflectance spectrum of 1998 KY26 is not very clear due to a large signal to noise and the limitation of wavelength. To have a definitive classification, the albedo information is necessary.
Xe-class asteroids are often found in the Hungaria family, a group of asteroid located in the in far inner asteroid belt with high inclination ~20 degree. Furthermore, (44) Nysa is known as Xe-type asteroid in the Nysa-Polana complex family. As this complex family is located in the inner main belt with low inclination angle, the possibility of having this family members in the near-Earth orbits is high. We compare the reflectance spectrum of 1998 KY26 with those asteroids and discuss the possible origin.
Despite its discovery in 1998, favorable viewing windows for 1998 KY26 are infrequent. April and May of 2024 presented the first such optimal opportunity for observation in over two decades. Seizing this chance, we conducted spectroscopic observations of 1998 KY26 using the 10.4-meter Gran Telescopio Canarias (GTC). Located at the Roque de los Muchachos Observatory on the island of La Palma in the Canary Islands, Spain, the GTC is one of the largest and most advanced optical and infrared telescopes in the world. The spectroscopic data provides valuable insights into the asteroid's surface composition, potentially revealing its origin and evolutionary history.
1998 KY26 was observed on the night of May 21st, 2024, at 04:14 UTC. Spectroscopic observations were done using the OSIRIS camera-spectrograph installed at GTC under the program GTC37-24A (PI, J. de León). OSIRIS is equipped with a blue-sensitive monolithic 4096x4096 CCD that provides a field of view of 7.8’x7.8’. We used the R300R grism that covers a wavelength range from 0.48 to 0.92 microns with a dispersion of 7.74A/pixel for a 0.6” slit. We combined the R300R grism with a slit of 1.2”, oriented to the parallactic angle and with the telescope tracking rate set to match the asteroid’s proper motion. Two consecutive spectra of 900 s of exposure, at an airmass of 1.36 were obtained. To get the asteroid’s reflectance spectrum, we also observed solar analog star Landolt SA112-1333, using the same instrumental setup and at a similar airmass to that of the asteroid. At the moment of the observations, 1998 KY26 presented an apparent visual magnigutde of mV=20.4, a phase angle of 29.7deg, and was at a distance of 1.053 au and 0.047 au from the Sun and the Earth, respectively.
To obtain the asteroid taxonomical classification, we used the M4AST online tool (Popescu et al. 2012). This tool fits a curve to the data and compares it to the taxon defined by DeMeo et al. (2009) using a chi^2 fitting procedure. The best fitted was Xe-class, a subclass of X-complex asteroids. The Xe-class asteroids are characterized by a broad absorption band around 0.49 µm. However, the absorption in the reflectance spectrum of 1998 KY26 is not very clear due to a large signal to noise and the limitation of wavelength. To have a definitive classification, the albedo information is necessary.
Xe-class asteroids are often found in the Hungaria family, a group of asteroid located in the in far inner asteroid belt with high inclination ~20 degree. Furthermore, (44) Nysa is known as Xe-type asteroid in the Nysa-Polana complex family. As this complex family is located in the inner main belt with low inclination angle, the possibility of having this family members in the near-Earth orbits is high. We compare the reflectance spectrum of 1998 KY26 with those asteroids and discuss the possible origin.