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Hubble Telescope Finds New Moon for Neptune

This illustration shows the orbits of Neptune's closest moons, all of which were discovered by Voyager 2 in 1989, except for the newly announced S/2004 N 1. Credit: NASA, ESA, and A. Feild (STScI)
This illustration shows the orbits of Neptune’s closest moons—all of which were discovered by Voyager 2 in 1989—except for the newly announced S/2004 N 1, which was discovered by Hubble. Credit: NASA, ESA, and A. Feild (STScI)

The Hubble Space Telescope‘s keen eye has revealed a previously undetected moon orbiting Neptune.  The July 1, 2013 discovery , 24 years after Voyager 2 swung by the icy-blue giant, expands the known retinue of circling moons to 14.

Known only by its temporary designation —S/20044 N1—the tiny celestial piece of real estate measures no more than 12 miles (19 kilometers) across and appears to have escaped detection until now because of its extreme faintness and far flung orbit beyond the planet’s ring fragment system known as arcs.

According to Mark Showalter, a planetary astronomer at the SETI Institute in California who discovered the moon, the newfound object is almost 100 million times fainter than the faintest star visible to the naked eye. But by tracking the movements of a mysterious white dot visible on 150 Neptune photographs taken by Hubble between 2004 and 2009, he managed to pin down this mini-moon.

“The moons and arcs orbit very quickly, so we had to devise a way to follow their motion in order to bring out the details of the system,” he said in a statement issued by NASA on Monday. “It’s the same reason a sports photographer tracks a running athlete—the athlete stays in focus, but the background blurs.”

This composite Hubble Space Telescope image shows the newly discovered moon, S/2004 N 1, in relation to other satellites orbiting the giant planet Neptune, nearly 3 billion miles from Earth.. Credit: NASA, ESA, and M. Showalter (SETI Institute)
This composite Hubble Space Telescope image shows the newly discovered moon, S/2004 N 1, in relation to other moons orbiting the giant planet Neptune, nearly 3 billion miles (4.8 billion kilometers) from Earth. Credit: NASA, ESA, and M. Showalter (SETI Institute)

S/20044 N1 orbits between the Neptunian moons Larissa and Proteus, and circles the planet once every 23 hours at an altitude of 65,400 miles (104,000 kilometers).

The origins of S/20044 N1 and some of its other tiny neighboring moons is still a mystery. But one theory is that Neptune’s largest moon Triton may have had something to do with it. Triton—nearly the size of Earth’s moon—is thought to be a gravitationally captured dwarf planet, which upon it’s arrival, may have broken apart the original Neptunian satellite system and created many of the small moons we see today. (Related: “Neptune Discovered a Year Ago Today*.”)

Follow Andrew Fazekas, the Night Sky Guy, on Twitter and Facebook.


  1. Bernadette
    October 8, 2013, 2:25 pm

    I wonder about the many things we have yet to discover about the universe. I mean, the hubble telescope only catching glimpses of things is just the beginning. It’s amazing all we’ve found just with it, but if we really want to discover more, and we’re only still discovering “new” objects found around our solar system, we should upgrade a bit. I am absolutely fascinated by these possibilities, and technology is rapidly advancing. Just imagine when we find intelligence somewhere else, or a place for humans to inhibit.

  2. Siliva
    July 21, 2013, 9:43 pm

    wooowooow one more possibility that more life is outthere

  3. Sami Ullah Hashemi
    July 19, 2013, 9:19 am

    What would they do with a lot of moons. We need an extra moon for Khyber Pakhtunkha. They always wish to celebrate their eid one day earlier. If they have their own moon this problem can be resolved. May be one day hubble find a new moon for KPK.

  4. David Kendrick
    Winnipeg, Canada
    July 17, 2013, 3:21 pm

    Must be quite the site to look up from the planet and see all those moons! Although with its temps and winds I don’t think we’ll ever be looking up from the surface of this planet.

  5. king saint
    united states
    July 17, 2013, 11:58 am

    its space any thing can happen at any time

  6. abd elfattah
    July 17, 2013, 9:35 am


  7. Josip
    July 17, 2013, 5:00 am

    Len they wrote newly discovered and newfound moon so its new to us but moon it self is not new

  8. akash yadav
    July 17, 2013, 12:21 am


  9. Marc S
    July 16, 2013, 8:49 pm

    You are all a bunch of mindless idiots. The dude deserves credit for his hard work something it seems all of you know nothing about except for making mindless comments

  10. swap
    July 16, 2013, 7:35 pm

    he is talking about newly discovered moon, and not about newly born moon. but in any means the discovery is not going to favor the world.

  11. Matt
    United States
    July 16, 2013, 6:08 pm

    Let’s assume for a minute that it didn’t take some considerable research to map these over five years and 150 faint images. And let’s assume that this is just idle speculation.

    What benefit do they have in informing people of something they’re not certain of, if only for the sake of reminding people that these organizations still exist and are doing something?

  12. Joshua
    July 16, 2013, 5:33 pm

    Mysteries are left for us to find, let say keep it up.

  13. Emre
    July 16, 2013, 5:14 pm

    ^ whoa another English professor on the horizon 😀

    Richland, WA
    July 16, 2013, 2:52 pm

    It circles the planet every 23 YEARS not every 23 hours.

  15. Scientist
    July 16, 2013, 2:47 pm

    Typo: it’s not “S/20044 N1” (as stated in the first paragraph), it’s “S/2004 N1.”

  16. Evan
    July 16, 2013, 2:40 pm

    At Adnan, the blue thing in the picture in Neptune…the “new” moon is circled…

  17. RevaMadison
    July 16, 2013, 2:23 pm

    Not only is it not a new moon, but the telescope did not find it. It was a human, using a tool, that found it. Come on headline writers and editors, lets use your education a bit more intelligently.

  18. Adnan Khan
    July 16, 2013, 2:03 am

    That’s no moon…

  19. David
    July 15, 2013, 6:26 pm

    Theory about moons = idle speculation.

  20. Len
    United States
    July 15, 2013, 5:21 pm

    I believe the correct word for this title should be “Another” not “New”. The moon has been there a LONG TIME. Its far from New.