Cool preview of Pluto craft’s next target

How do you study a body only tens of miles across, nearly 4 billion miles away? Wait for it to pass in front of a star! Astronomers call these events occultations of stars, and they’ve been scientifically fruitful in the past. For example, rings for the planet Uranus were first discovered in 1977, when that outer planet occulted a star. Starting today (June 3, 2017) and for the next six weeks, the mission team of the New Horizons spacecraft – same team that has been busy analyzing data from New Horizons’ 2015 Pluto flyby – will be peering through earthly telescopes at three different occultation events involving the craft’s next target object, a tiny and almost wholly unexplored body in the Kuiper Belt known as 2014 MU69.

New Horizons will race past MU69 on January 1, 2019, bestowing upon this little world the distinction of being the farthest object yet encountered by any earthly spacecraft. But that’ll be then. For now the team is traveling to Argentina, South Africa and boarding NASA’s airborne Stratospheric Observatory for Infrared Astronomy (SOFIA) in order to observe MU69 as it passes in front of stars on June 3, and on July July 10 and 17.

You can follow their observations on Facebook and Twitter using #mu69occ.

According to these astronomers’ statement, the occultations by MU69 will give the New Horizons mission team:

… a preview of sorts – and a chance to gather some critical encounter-planning information – with a rare look at their target object from Earth …

To observe the June 3 [occultation], more than 50 team members and collaborators are deploying along projected viewing paths in Argentina and South Africa. They’ll fix camera-equipped portable telescopes on the occultation star and watch for changes in its light that can tell them much about MU69 itself.

New Horizons Principal Investigator Alan Stern, of Southwest Research Institute (SwRI) in Boulder, Colorado explained why these observations are so important for the New Horizons team:

Our primary objective is to determine if there are hazards near MU69 – rings, dust or even satellites – that could affect our flight planning. But we also expect to learn more about its orbit and possibly determine its size and shape. All of that will help feed our flyby planning effort.

Marc Buie, the New Horizons co-investigator from SwRI who is leading the occultation observations, said that because MU69 is so small – thought to be about 25 miles (40 km) across – the occultations should only last about two seconds. But he said scientists can learn a lot from even that, and observations from several telescopes positioned at different places on Earth can reveal information about an object’s shape as well as its brightness.

The team provided this description of their equipment and plans:

The mission team has 22 new, portable 16-inch (40-cm) telescopes at the ready, along with three others portables and over two-dozen fixed-base telescopes that will be located along the occultation path through Argentina and South Africa. But deciding exactly where to place them was a challenge. This particular Kuiper Belt object was discovered just three years ago, so its orbit is still largely unknown. Without a precise fix on the object’s position – or on the exact path its narrow shadow might take across Earth – the team is spacing the telescope teams along ‘picket fence lines,’ one every 6 to 18 miles (10 or 25 km), to increase the odds that at least one or more of the portable telescopes will catch the center of the event and help determine the size of MU69.

The other telescopes will provide multiple probes for debris that could be a danger to the fast-moving New Horizons spacecraft when it flies by MU69 at about 35,000 miles per hour (56,000 km per hour), on January 1, 2019.

These scientists say they welcome any information on MU69, gathered from the skies or on the ground. Carly Howett, deputy principal investigator of New Horizons’ Ralph instrument, of SwRI, said so little is known about MU69 that the team is planning observations of a target it doesn’t fully understand. She also pointed out that time to learn more about the object is short:

We were only able to start planning the MU69 encounter after we flew by Pluto in 2015. That gives us two years, instead of almost seven years we had to plan the Pluto encounter. So it’s a very different and, in many ways, more challenging flyby to plan.

Alan Stern said:

Spacecraft flybys are unforgiving. There are no second chances. The upcoming occultations are valuable opportunity to learn something about MU69 before our encounter, and help us plan for a very unique flyby of a scientifically important relic of the solar system’s era of formation.

Bottom line: On June 3, July 10 and July 17, 2017, astronomers will be watching as tiny MU69 in the outer solar system – the New Horizons spacecraft’s next target – occults or blocks the light from three different stars.

Via New Horizons mission