[meteorite-list] Observations Show 2005 FY9 Is Very Similar To Pluto

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Sat Jan 14 12:39:26 2006
Message-ID: <200601141737.k0EHbm202772_at_zagami.jpl.nasa.gov>

Isaac Newton Group of Telescopes
Apartado de correos 321
E-38700 Santa Cruz de la Palma
Canary Islands, Spain

Contact:
Javier M?ndez, Public Relations Officer
jma _at_ ing.iac.es

News release date: 13th January, 2006

WHT and TNG Observations Prove that the Large Trans-Neptunian Object 2005
FY9 is Very Similar to Pluto

Visible and near-infrared spectroscopic observations carried out on August
1st 2005 by a group leaded by the ING-IAC astronomer Javier Licandro[1]
using the William Herschel Telescope (WHT) and the Telescopio Nazionale
Galileo (TNG) at El Roque de Los Muchachos Observatory show that the
recently discovered trans-neptunian object (TNO) 2005 FY9 is very similar
to Pluto. Results have been published in the journal Astronomy &
Astrophysics (Licandro et al., 2006, A&A, 445, 35L).

2005 FY9 is the third brightest known TNO, after 2003 UB313 and Pluto.
Although discovered early in 2005 by USA astronomers M. Brown and
co-workers, the discovery wasn't reported until July 29th. The size of
2005 FY9 is 0.7 times that of Pluto approximately. The semi-major axis of
its orbit is 46 Astronomical Units (AU, 1 AU=149,597,892 kilometres), the
perihelion distance is 39 AU and the inclination of the orbit is 29 deg.
These values are typical of the classical TNO family.

Visible spectroscopy was obtained using the ISIS spectrograph on the WHT,
and near-infrared spectroscopy was obtained using the NICS spectrograph on
the TNG. The complete visible and near-infrared spectrum is shown in
Figure 2 and compared with the spectrum of Pluto and that of pure methane
ice. Figure 2 clearly shows that the spectra of both TNOs are very
similar. They are dominated by strong absorption bands produced by methan
ice. In fact, the absorption bands in the spectrum of 2005 FY9 are deeper
than in the spectrum of Pluto as a result of the larger abundance of
methane ice in 2005 FY9. Also the colour of the surface of the TNO is red
(indicated by the slope of the spectrum), similar to that of Pluto. This
shows the presence of complex organic compounds in the surface.

The discovery of a Pluto 'twin' in the trans-neptunian belt is relevant as
Pluto is the only known TNO possessing a small atmosphere. The similar
size and surface composition of 2005 FY9 are facts that suggest it can
also have such a tenuous bound atmosphere.

Until now only one known TNO, Pluto, showed the presence of strong methan
ice absorption bands in the spectrum. However, apart from 2005 FY9,
recently these bands were also observed in the spectrum of the largest yet
known TNO, 2003 UB313 (Brown et al., 2005, ApJ, 635, 97). As shown in
Figure 3, the near infrared spectrum of 2003 UB313 is very similar to that
of 2005 FY9.

The discovery that 2005 FY9 is very similar to Pluto provides astronomers
with a new and exciting laboratory for the study of volatile mixing and
transport, atmospheric freeze-out and escape, ice chemistry, and nitrogen
phase transitions in Pluto-like objects.

Notes:

[1] The members of the international team led by Javier Licandro (ING-IAC)
are William Grundy (Lowell Observatory), Ernesto Oliva (FGG-TNG), Marco
Pedani (FGG-TNG), Noem? Pinilla-Alonso (FGG-TNG) and Gian Paolo Tozzi
(Osservatorio di Arcetri).

IMAGE CAPTIONS:

[Figure 1:
http://www.ing.iac.es/PR/press/8451.jpg (23KB)]
The size of the largest objects known in the outer Solar System compared
with the size of the Moon.

[Figure 2:
http://www.ing.iac.es/PR/press/spectrum2005FY9.gif (28KB)]
The spectrum of 2005 FY9 compared with the spectrum of Pluto and that of
pure methane ice. Notice the strong methan ice absorption bands present in
the spectrum of both TNOs.

[Figure 3:
http://www.ing.iac.es/PR/press/img19.gif (29KB)]
Near infrared spectrum of 2005 FY9 obtained by Licandro et al. (2006)
compared with that of TNO 2003 UB313 from Brown et al. (2005). The
similarity of both spectra shows that the surface composition of both
objects must be also similar.
Received on Sat 14 Jan 2006 12:37:48 PM PST