Catching a Glimpse of New Horizons

3 June 2017
Catching a Glimpse of New Horizons

In the early hours of the morning on 03 June 2017, while most locals are sleeping, dozens of astronomers across South Africa will be looking up at the night sky in hopes of viewing a shadow from a mysterious, distant object.  They are part of a large, international effort to study the target of NASA’s New Horizons spacecraft extended mission.  New Horizons stunned the world in 2015 when it passed through the Pluto system and returned unprecedented images and information about Pluto and its five moons.  The extended mission will allow the spacecraft to collect data on an even more remote object, called 2014MU69 (Figure 1).

2014MU69 was discovered by the Hubble Space Telescope. It is dynamically classified as a classical Kuiper Belt object.  Because it is very faint, with a  26.3 visual magnitude, little is known about its physical properties.  A stellar occultation, during which the light of a distant star is blocked by 2014MU69, has been predicted to be observable from specific regions of the Southern Hemisphere on 03 June (Figure 2).  If successfully observed, this fleeting event could allow measurement of 2014MU69‘s size and shape, could detect rings, dust or debris, and could improve the positional accuracy, all of which would be vital information for planning the spacecraft encounter.  2014MU69 is located nearly 6.5 billion kilometers away with an estimated diameter of approximately 40 km, and the entire occultation will only last roughly 2 seconds. Thus, the observers need to be in exactly the right place, at the right time, with the right equipment to detect the brief dip in the starlight.

To optimize the likelihood of successful observing opportunities (and to avoid bad weather!), observers will be stationed in South Africa, Namibia, Chile, Brazil, Uruguay, and Argentina. Locally, SAAO observers will be using both the 74-inch telescope and the three Las Cumbres Observatory telescopes in Sutherland.  Multiple members of the ASSA (Astronomical Society of South Africa) are also contributing to the effort.  In Southern African alone, there are roughly three dozen overseas visitors who pre-shipped more than a dozen portable telescopes and specialized cameras (Figure 3).

“It is impressive to have so many people visiting South Africa and to see the amount of effort put in to taking the data. It’s a particularly challenging observation that can’t be done without international collaborators. If we are successful, this will be an occultation observation by the faintest object ever and will allow new, accurate measurements to help support New Horizons,” says Anja Genade, an SAAO/UCT student in the NASSP program whose research involves stellar occultations.

Currently, the spacecraft is approximately halfway between Pluto and 2014MU69, and it is scheduled to fly by the target on 01 January 2019. This will be the most distant Solar System object ever encountered by a spacecraft.  Pluto was revealed to be a dynamic, exciting object by New Horizons, and we are sure to expect further surprises and enlightenments from the extended mission as it explores the edge of our Solar System.


(1) Schematic of the New Horizons spacecraft journey through the Solar System. Credit: NASA.
(2) Predicted shadow path for the 03 June 2017 stellar occultation by 2014MU69. The red lines represent the centerline of the shadow, yellow lines represent 1-sigma error bars, and blue lines represent 3-sigma error bars. Observing stations will thus be located in South America and Southern Africa. (Map courtesy of M. Buie and S. Porter of SwRI.)
(3) Map of South Africa showing parallel locations centered on the predicted shadow path, creating a "picket fence" coverage across the full 3-sigma error bar. This is representative of the 10-25 km spacings along which portable teams can be stationed, in an attempt to ensure that the shadow is detected without slipping in between two stations. (Map courtesy of M. Buie and S. Porter of SwRI.)


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