Tuesday, 9 September 2014

Observations of New Horizons candidate bodies with the Hubble Space Telescope.

The New Horizons Spacecraft was launched in January 2006, and is due to pass through the Pluto System (Pluto is now recognized to be a cluster of at least six objects rather than a single large body) in July 2015. After this it is hoped that New Horizons will be able to adjust its path in order to visit one of the smaller bodies of the Kuiper Belt, possibly the only such body that will be visited by a probe in the lifetime of anyone currently alive. As well as hopefully visiting a small Kuiper Belt object, New Horizons will pass within 0.3 AU (30% of the distance of the Earth and the Sun) of a larger number of bodies, providing the opportunity to provide clearer observations than possible from any Earth-based telescope, or space telescope in a near-Earth orbit.

Attempts to locate Kuiper Belt objects that would be within range of New Horizons observation began in 2004, though the wide area of space that required surveying in order to detect bodies that would be close to the New Horizons path in 2015/16, combined with the smallness of the telescopes available at the time, prevented the production of useful results. By 2011 the area of space that needed to be searched had shrunk considerably, and it was possible to use larger telescopes in the search for target bodies, notably the 8.4-m Subaru Telescope and 6.5-m Magellan Telescopes. As yet no object has been located that would be within range of a a New Horizons flyby, but a number of candidate objects for longer range observation have been identified.

In a paper published on the arXiv database at Cornell University Library on 28 May 2014, and accepted for publication in the journal Icarus, Susan Benecchi of the Planetary Science Institute and the Department of Terrestrial Magnetism at the Carnegie Institution of Washington, Keith Noll of the Goddard Space Flight Center, Harold Weaver of the Space Department at the Applied Physics Laboratory at Johns Hopkins University, John Spencer, Alan Stern and Marc Buie of the Southwest Research Institute and Alex Parker of the Department of Astronomy at the University of California, Berkeley describe the results of follow-up observations of four objects discovered by the ground based survey with the Hubble Space Telescope.

One of the objects found by the Earth-based survey could not be recovered by the Hubble Space Telescope. 2011 JW31 was discovered on 4 May 2011 (the name 2011 JW31 implies the 797th object discovered in the first half of May 2011), and is thought to have a 306 year orbital period and an elliptical orbit titled at an angle of 1.9° to the plane of the Solar System that takes it from 42.9 AU from the Sun (i.e. 42.9 times as far from the Sun as the Earth) to 47.9 AU from the Sun (47.9 times as far as the Earth). However it was the faintest of the objects included in the study, and was predicted to be in front of a cluster of faint stars at the time of observation, making it hard to observe and poorly understood.

The Calculated orbit 2011 JW31. JPL Small Body Database Browser.

2011 JY31 was discovered on 4 May 2011 (the name 2011 JY31 implies the 799th object discovered in the first half of May 2011), and re-observed 6, 34, 65 and 365 days after its initial discovery, so its parameters were reasonably well understood. Hubble Was able to observe it 510 days after its initial discovery, on 18 September 2012, within 0.4 arcseconds of its predicted position (the sky is a sphere split into 360 degrees by astronomers, each degree is subdivided into 60 arcminutes, and each arcminute into 60 arcseconds), which corresponds to about 14 000 km at a distance of 44 AU (44 times the average distance between the Earth and the Sun). 

Hubble Space Telescope image of 2011 JY31. Benecchi et al. (2014).

2013 JW31 appears to be a single body; Hubble was unable to observe any potential companion object within 0.02 arcseconds (700 km at 44 AU). It has a 291 year orbital period and an elliptical orbit tilted at an angle of 2.6° to the plane of the Solar System that takes it from 41.5-46.3 AU from the Sun (41.5-46.3 times as far as Earth), and will have its closest encounter with New Horizons on 27 September 2018, when it will be 0.16 AU (23 940 000 km) from the spacecraft.

The calculated orbit of 2011 JW31. JPL Small Body Database Browser.

2011 HZ102 was discovered on 28 April 2011 (the name 2011 HZ means the 2575th asteroid discovered in the second half of April 2011). It was re-observed by Hubble 17 September 2012.

Hubble Space Telescope image of 2011 HZ102. Benecchi et al. (2014).

2011 HZ102 also appears to be a single body; Hubble was again unable to observe any potential companion object within 0.02 arcseconds (700 km at 44 AU). It has a 283 year orbital period and an elliptical orbit tilted at an angle of 2.4° to the plane of the Solar System that takes it from 42.6-43.6 AU from the Sun (42.6-43.6 times as far as Earth), and will have its closest encounter with New Horizons on 16 December 2018, when it will be 0.15-0.16 AU (22 400 000-23 940 000 km) from the spacecraft.

The calculated orbit of 2011 HZ102. JPL Small Body Database Browser.

2013 LU35 was discovered on 5 June 2013 (the name 2013 LU35 implies the 895th asteroid discovered in the first half of June 2013). It was reobserved by Hubble on 27 September 2013.

Hubble Space Telescope image of 2013 LU35. Benecchi et al. (2014).

2013 LU35 also appears to be a single body; Hubble was again unable to observe any potential companion object within 0.02 arcseconds (700 km at 44 AU). It has a 288 year orbital period, and an eccentric orbit tilted at an angle of 3° to the plane of the Solar System that takes it from 41.3-45.9 AU from the Sun (41.3-45.9 times as far as Earth), and will have its closest encounter with New Horizons between 4 February and 12 October 2019, when it will be 0.30-0.38 AU (44 880 000-56 850 000 km) from the spacecraft.

The calculated orbit of 2013 LU35. JPL Small Body Database Browser.

A fifth body, 2011 HJ103, will also come within long range observation distance of New Horizons, though this was not observed by Hubble. 2011 HJ103 was discovered on 28 April 2011 (the name 2011 HJ103 implies the 2585th asteroid discovered in the second half of April 2011). It is calculated to have a 314 year orbital period, and an eccentric orbit tilted at an angle of 5.3° to the plane of the Solar System that takes it from 40.3-52.2 AU from the Sun (40.3-52.2 times as far as Earth). It is predicted to be at its closest to New Horizons between 24 February 2017 and 10 January 2018, when it will be 0.19-0.43 AU (28 420 000-64 330 000 km) from the spacecraft.

The calculated orbit of 2011 HJ103. JPL Small Body Database Browser.

See also…


The dwarf planet Pluto will reach opposition slightly before 3.00 am GMT on Friday 4 July 2014; this means that it will be directly opposite the Sun in the sky when viewed from Earth, on this occasion in the...



The Kuiper Belt is a region of the Solar System extending from the orbit of Neptune at about 30 AU (i.e. 30 times the distance between the Sun and the...


NASA scientists announced this week (20 July 2011) that they had discovered a new moon around the dwarf planet Pluto. The discovery was made by scientists using the Hubble Space Telescope in a set of five long exposure pictures taken over a period of two months...


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