New Horizons: Star Fields Beyond

by Paul Gilster on April 6, 2017

The attitude you bring to a star field changes everything. When I was a kid trying to figure out how to use a small telescope, I scanned the usual suspects — the Moon, Saturn and its rings, the Galilean satellites of Jupiter — all the while planning to branch out into major wonders like M31 or the Ring Nebula in Lyra. But when I turned to deep sky objects, what I discovered was that I could see little more than faint smudges — I was using no more than a 3-inch reflector. It was a disappointment for a while, until I accepted the limitations of my equipment.

And then I became a cataloger of faint smudges, as avidly tracking down celestial objects as any stamp collector sorting through new finds. A patient uncle showed me how to look slightly away from the object I sought, to pick it up in peripheral vision. I began keeping notebooks listing my first glimpses of various nebulae and clusters. So many celestial objects were out of reach, but somehow a field of stars became wondrous not only for what I was seeing but for what I knew I might see with a larger instrument.

The image below recalled those days precisely because of what we cannot see in it. This is actually drawn from a series of images taken by New Horizons’ LORRI instrument showing the area toward which the craft is heading. We’re looking toward a close approach and flyby of the Kuiper Belt object MU69 at 0200 Eastern US time (0700 UTC) on New Year’s Day of 2019. Right now we’re still far enough way that the target isn’t visible even to LORRI, but to me this image is freighted with the raw excitement of exploration as we push ever deeper into the Solar System.


Image: In preparation for the New Horizons flyby of 2014 MU69 on Jan. 1, 2019, the spacecraft’s Long Range Reconnaissance Imager (LORRI) took a series of 10-second exposures of the background star field near the location of its target Kuiper Belt object (KBO). This composite image is made from 45 of these 10-second exposures taken on Jan. 28, 2017. The yellow diamond marks the predicted location of MU69 on approach, but the KBO itself was too far from the spacecraft (877 million kilometers) even for LORRI’s telescopic “eye” to detect. New Horizons expects to start seeing MU69 with LORRI in September of 2018 – and the team will use these newly acquired images of the background field to help prepare for that search on approach. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

New Horizons is going into hibernation this week for a 157 day period, and I hadn’t realized until getting this JHU/APL update that the craft had been in full operational mode for almost two and a half years now, which of course dates back to the Pluto encounter and the long period of data return (16 months). Along the way New Horizons has continued to study the dust and charged particle environment of the Kuiper Belt as well as hydrogen in the heliosphere.

We’re now halfway between Pluto and MU69, having reached this point — a distance of 782.45 million kilometers from Pluto and MU69 — early on April 3 (UTC). The gravitational pull of the Sun continues to slow the craft, so it won’t be until tomorrow (April 7) that we reach the halfway point in terms of time between the two close approaches. Remember that New Horizons left Earth orbit traveling faster than any vehicle ever launched, but nine years of climbing out of the gravity well have slowed it to 14 kilometers per second at the Pluto/Charon flyby, significantly below the 17 kilometers per second-plus that Voyager 1 has attained.

The good news is that the mission includes further exploration beyond MU69. Hal Weaver is a New Horizons project scientist from the Applied Physics Laboratory (Laurel, MD):

“The January 2019 MU69 flyby is the next big event for us, but New Horizons is truly a mission to more broadly explore the Kuiper Belt. In addition to MU69, we plan to study more than two-dozen other KBOs in the distance and measure the charged particle and dust environment all the way across the Kuiper Belt.”

Looking ahead once we’re past MU69, there will be so many things we cannot see in the star field ahead. So much to discover for the deep space missions beyond New Horizons. When will a true interstellar probe — a mission designed from the start to examine the local interstellar medium — be launched? Without an answer, we can only keep pushing for exploration, an innate characteristic of our species, and one unlikely to be limited by our Solar System.


{ 19 comments… read them below or add one }

jonW April 6, 2017 at 15:09

Two dozen more KBOs! What does this mean, surely they can’t be hoping to find another fly-by target after MU69?


Raj Pillai April 7, 2017 at 8:09

Jon W.. See the timelines for observation of each KBO.. MU69’s flyby is Jan 1st 2019.. Enjoy…


jonW April 7, 2017 at 20:55

I see, thank you! So they are not actual fly-bys, but some of them are relatively close… the closest will be something called 2014OS393 (diameter ~46 km), at just under 0.1 AU or about 9 million miles, at the very end of 2018.


jonW April 6, 2017 at 15:24

If we did want to launch an interstellar probe using today’s launch technologies, and we aimed for the most favourable set of gravity assists available in the next several years for reaching the interstellar medium asap, not caring about the ultimate direction* of the probe, what kind of speeds could we get it to/how long would it take? I’m wondering if the long wait expected for contact with the interstellar medium is what makes such a mission seem less attractive.

*Actaully, would we want to travel in the direction of the sun’s motion, to exit the heliosphere faster?


djlactin April 7, 2017 at 9:03

I think the response depends on how long you are willing to wait for the interstellar encounter. Voyager, Pioneer and NH are already ‘interstellar probes’ but our species may no longer exist when the encounters happen. I doubt that we could get the requisite speeds by mere gravitational slingshots. Energy required to accelerate 1 kg to 0.1c is 4.5 x 10^15 J (neglecting thermodynamic losses), or approximately 125000 tonnes of TNT.


jonW April 7, 2017 at 20:50

I meant “interstellar probes” in the sense Paul did in his post: probes of the interstellar medium, not probes of other star systems. Voyager 1 took about 30 years, but of course its mission was optimised for planetary encounters and the interstellar medium is just a bonus. But if you’re shooting for the interstellar medium to begin with, surely you can make use of slingshots to get there quicker even with current launch technology. Can we get there in less than a decade, for example? (New Horizons was launched faster than Voyager, but without as powerful gravitational assists it took 9 years to get to Pluto, about 32 AU away–the heliopause is about 121 AU from the sun)


Geoffrey Hillend April 6, 2017 at 15:51

Any new targets after MU69?


Gideon Marcus April 8, 2017 at 10:17

From Emily Lakdawalla’s blog:

“What happens after the flyby? Unfortunately, even if Hubble surveys continued, they would be very unlikely to yield another reachable object after 2014 MU69. The little world is at the edge of the classical Kuiper belt; beyond that, the space around the Sun is far more empty.”


George King April 6, 2017 at 16:17

Voyager 1 took the Pale Blue Dot shot from 40.5 AU out, according to Wikipedia.

They shut down V’ger’s cameras a short time later, essentially permanently.

New Horizons currently is 38.10 AU from Earth and has somewhere around 5 AU more to go before it reaches MU69. So it looks like it likely will have operational cameras at 40.5 AU out from Earth and beyond.

Are they planning to do another one of Carl Sagan’s Pale Blue Dot views back once they reach or exceed 40.5?

And will New Horizons thereafter, as it turns its cameras to MU69 and beyond, be the furthest out operational camera that we’ve had to date?

Peering further out from further out (well, subject to the limits of the instruments in comparison to larger, closer in ones).


Gideon Marcus April 8, 2017 at 10:13

I suppose the question is does New Horizons have good an inclination angle on the solar system as Voyager 1 did. Pluto is definitely angled to the ecliptic, but I don’t know if it’s angled enough to make as pretty a shot.


Ryan Cornell April 21, 2017 at 1:02

I’ve used Simulation in Astronomy programs… It’s Awesome! You can see the Difference right away… they’re closer together!


Daniel Suggs April 6, 2017 at 22:20

I wonder if it would be possible to aim the camera back at the sun and use gravitational lensing to look at another system? Maybe just as a proof of concept?


djlactin April 7, 2017 at 9:06

Interesting thought! but I think we’re not yet into Sol’s focus, which is (I think) out in the Oort cloud. But if the operators try the idea and it works, you deserve credit!


Paul Gilster April 7, 2017 at 10:58

Alas, the focus begins at 550 AU, and I’m not sure where it begins for optical wavelengths. Will need to calculate how long it will be before New Horizons gets out that far!


Gideon Marcus April 8, 2017 at 10:14

Paul, this is one my favorite articles of yours. Beautifully written and an exciting topic. Thank you.


Paul Gilster April 8, 2017 at 16:55

My pleasure, Gideon, and thank you. Always glad to have you on the site. And I’m enjoying the recent Twilight Zone material on Galactic Journey. I’ve had a complete run of Twilight Zone on DVD for some time and am finally going through it show by show — just happen to be in Season 3 right now, so your post is quite timely!


MaleBlueDot April 9, 2017 at 6:57

Maybe if we located Planet X (or 9 or whatever you want to call it) in time, and we had the immense luck that its orbit was within the reach of the NH with some adjustments of trajectory …


Harry R Ray April 11, 2017 at 9:46

MORE EVIDENCE FOR PLANET NINE: “The curiously warped plane of the Kuiper belt.” by Katheryn Volk, Renu Malhorta. Adding THIS to the mix of ALL THE OTHER CLUES to Planet Nine’s location, my guess is that it will be discovered in LESS THAN A YEAR!


Harry R Ray April 11, 2017 at 9:52

arXiv: 1704.02444


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