New Horizons Spots Neptune’s Moon Triton

Article written: 12 Mar , 2009
Updated: 24 Dec , 2015
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New Horizons got a great shot of Neptune’s moon Triton last fall, as it was trucking toward Pluto and the Kuiper Belt. 

The mission was 2.33 billion miles (3.75 billion kilometers) from Neptune on Oct. 16, when its Long Range Reconnaissance Imager (LORRI) locked onto the planet and snapped away. The craft was following a programmed sequence of commands as part of its annual checkout. NASA released the image Thursday afternoon.

Mission scientists say the shot was good practice for imaging Pluto, which New Horizons will do in 2015. Neptune’s moon Triton and Pluto — the former planet retitled in 2006 as the ambassador to the Kuiper Belt — have much in common.

“Among the objects visited by spacecraft so far, Triton is by far the best analog of Pluto,” said New Horizons Principal Investigator Alan Stern. 

Triton is only slightly larger than Pluto, boasting a 1,700-mile (2,700-kilometers) diameter compared to Pluto’s 1,500-mile (2,400-kilometer) girth. Both objects have atmospheres primarily composed of nitrogen gas with a surface pressure only 1/70,000th of Earth’s, and comparably cold surface temperatures. Temperatures average -390 degrees F (-199 degrees C) on Triton and -370 degrees F (-188 degrees C) on Pluto. 

Triton is widely believed to have once been a member of the Kuiper Belt that was captured into orbit around Neptune, probably during a collision early in the solar system’s history. Pluto was the first Kuiper Belt object to be discovered.

Furthermore, “We wanted to test LORRI’s ability to measure a faint object near a much brighter one using a special tracking mode,” said New Horizons Project Scientist Hal Weaver, of Johns Hopkins University, “and the Neptune-Triton pair perfectly fit the bill.”

LORRI was operated in 4-by-4 format (the original pixels are binned in groups of 16), and the spacecraft was put into a special tracking mode to allow for longer exposure times to maximize its sensitivity.

Mission scientists also wanted to measure Triton itself, to follow up on observations made by the Voyager 2 spacecraft during its flyby of Neptune in 1989. Those images revealed evidence of cryovolcanic activity and cantaloupe-like terrain. New Horizons can observe Neptune and Triton at solar phase angles (the Sun-object-spacecraft angle) that are not possible to achieve from Earth-based facilities, yielding new insight into the properties of Titan’s surface and Neptune’s atmosphere.

New Horizons is currently in electronic hibernation, 1.2 billion miles (1.93 billion kilometers) from home, speeding away from the Sun at 38,520 miles (61,991 kilometers) per hour. LORRI will continue to observe the Neptune-Triton pair during annual checkouts until the Pluto encounter in 2015. 

LEAD IMAGE CAPTION: The top frame is a composite, full-frame (0.29° by  0.29°) LORRI image of Neptune taken Oct. 16, 2008, using an exposure time of 10 seconds and 4-by-4 pixel re-binning to achieve its highest possible sensitivity. The bottom frame is a twice-magnified view that more clearly shows the detection of Triton, Neptune’s largest moon. Neptune is the brightest object in the field and is saturated (on purpose) in this long exposure. Triton, which is about 16 arcsec east (celestial north is up, east is to the left) of Neptune, is approximately 180 times fainter.  All the other objects in the image are background field stars. The dark “tails” on the brightest objects are artifacts of the LORRI charge-coupled device (CCD); the effect is small but easily seen in this logarithmic intensity stretch. (Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute)

Source: NASA


9 Responses

  1. Calvin says

    Google agrees with you Jorge 😉

    On another note, personally at that low of temperature Kelvins have more meaning to me than big negative degrees celsius numbers. I kind of wish people would use Kelvins alot more.

  2. Jorge says

    Hm… temperatures do not compute.

    The temperature in Triton, as far as I know, is slightly less than 40 K. Since 0 K is equivalent to – 273.15 ºC, this means the temperature in Triton is some -235, -240 ºC, not -199.

    Similarly, Pluto’s surface temperature is about 45 K, i.e., some -228 ºC, not -188.

  3. Hmmm … thanks. I’ll revisit my conversions.

  4. McRude says

    Lets not confuse the issue more than it needs to be.
    If NASA and other space agencies want to be more user friendly (therefore keeping the interests of the public which equates to better funding), they should at least put the normal English temperature-mileage unit measurements in all articles so that a calculator isn’t necessary to get the “WOW” factor. Using Kelvin is just irritating to a kid that doesn’t have an explanation handy.
    You may think of this comment as a “dumbing down” of science – but I see it as a way to incorporate as much interest in as many levels of education as possible. Remember even uneducated people vote.
    We have the “WOW” factor of Hubble pictures to thank exclusively for the interest in Space we are enjoying right now, which hasn’t been seen since we landed on the moon. If we are really going to go to the Moon again, we need to keep that interest at all costs – and increase it as much as possible. Before Hubble, only serious Space enthusiasts and severely educated people knew or cared what a light year was let alone how far it is.
    Now I hear kids asking why they always say a light year is “about” 6 trillion miles? I tell them they say that to keep it simple. Now they can almost automatically convert Kilometers to miles. They still only care about miles.
    Keeping kids interested is a simple way to continue the future of almost anything in science. I feel that will better our chances of actually getting to the Moon.

  5. Yael Dragwyla says

    McRude — You’re right. This isn’t a club for elites — we desperately need to engage the interest of the general public in space-related endeavors, and using common measurement units in articles helps to avoid alienating the vast majority of people out there. Those who are in the sciences know how to do the conversions, but they don’t have the money to fund such ventures; the general public is the source of the revenues to fund them, but doesn’t have that much familiarity with metric units. We need to follow the money, not cater to those who want to keep this an exclusive “just us” group of enthusiasts.

  6. Jorge says

    Well, this time I didn’t complain about the use of Fahrenheit and Celsius scales; I simply noted that the Celsius temperatures were (and still are as I’m writing this) wrong.

    You can debate weather or not this kind of article is better with Kelvin, Celsius, Fahrenheit or a combination of these scales, but you can’t argue, I believe, that whatever the scale you better make sure your numbers are right.

    But since this same old discussion about units came up, for some reason, let me say two things:

    1. It was not just the English and English-derived cultures that had their own traditional units of measure. Every culture did. And yet, most of the world has since abandoned their traditional units and embraced SI units, because they are far more rational and easy to use. They did it in a time when most of the people using the units (carpenters, smiths, traders, etc.) were illiterate and didn’t have the benefits of a formal education, and yet they did it neatly, with relative ease and without much ado. Some anglos, however, largely literate and formally educated, stick stubbornly to their archaicisms and I really (really) can’t understand why.

    2. This site isn’t made for american schoolchildren. It has a global audience, and therefore should try its best to satisfy this global audience. This doesn’t mean that everything should be primarily in SI, but it does mean that values in SI should always be there. Because SI isn’t just the language science understands; it’s the language the world understands.

  7. farco says

    I eager to see the probe arrives in orbit of pluto in 2015.

  8. McRude says

    I agree that the numbers should always be correct … -regardless of the scale. I know it is a global audience. I was merely suggesting that English units be used alongside Kilometers or whatever, but in parenthesis only. I don’t believe that the scale used could or would make an article better because a great article is simply based on CORRECT facts, (and great pictures). My point was that we should keep the information simple for a wider appeal.
    NASA is a dominant partner in Space exploration with Europe so naturally my concern would be with American school children simply because I cannot influence anything that ESA does, I can only TRY to influence what NASA does.

    I don’t want the loss of public interest to help kill ANYONES exploration of Space like in did in the early 1970’s. (which STILL Pisses me off to this day!) You have to keep in mind- the American public has the attention span as long as one of my Malamute puppies – About two minutes on a good day

    No matter what is happening on this planet, it is a nice mental vacation to visit sites like this. When the news starts to get on my nerves I pull up Hubble’s pics and then go searching for info on whatever……. It keeps me in focus about how small and insignificant we really are in the grand scale of things.

  9. bobo says

    lame and get a life

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