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New Horizons revealed: Pluto's diameter is 2,370 km

The observations of the New Horizons spacecraft that will pass today at a distance of about 12,600 km from Pluto determined that the diameter of Pluto's large moon - Charon is 1,208 kilometers.

The brave new worlds Pluto and Charon are in the focus of the field of view of the LORRI camera on the New Horizons spacecraft. Photo: NASA TV
Pluto and Charon in the focus of the field of view of the LORRI camera on the New Horizons spacecraft. Photo: NASA TV

Image of Pluto, July 11 in high resolution. The color is processed, when the color images arrive it will be possible to update this image Credits: NASA-JHUAPL-SWRI

The New Horizons spacecraft managed to answer one basic question about Pluto - its diameter. Mission managers discovered that the diameter of the dwarf planet is 2,370 kilometers, slightly larger than previous estimates. Images taken by the Long Range Reconnaissance Imager (LORRI) installed on the New Horizons spacecraft helped make this determination. This result made it possible to confirm what had until now been an estimate: Pluto is larger than all the other objects in the solar system beyond the orbit of Neptune.

"Pluto's size has been debated since it was discovered in 1930. "We are happy to finally put an end to that question." says mission scientist Bill McKinnon of Washington University in St. Louis. It seemed that the debate was resolved with the discovery of the moon as an ark, and the measurement of the mutual influence of the two bodies, but it turns out not exactly.

The meaning of the new estimate is that its density is slightly lower than previously thought, and that the friction of the ice within the inner crust is slightly stronger than the estimate so far. Also, the lower layer of Pluto's atmosphere - the troposphere - is shallower than previously thought.

Measuring Pluto's size has been difficult due to factors in the atmosphere that can be misleading. Its large moon, Aron, lacks a significant atmosphere, and its diameter was easier to calculate based on observations from ground-based telescopes. Observations by the New Horizons spacecraft determined that Charon's diameter is 1,208 kilometers.

The LORRI camera also observed two of Pluto's small moons - Nix and Hydra. "We knew from the moment we planned the flyby that we could study the small moons in detail a few days before approach," says New Horizons principal investigator Alan Stern of the Southwest Research Institute in Boulder, Colorado. "Now is the time to probe deep into Pluto's sphere of influence."

Nix and Hydra were discovered by the Hubble Space Telescope in 2005. To Hubble too, they appeared as small points of light, and so they remained until New Horizons observed them a few weeks before the transit near Pluto. Now, the latest LORRI images show these secondary moons not as dots but as moons whose size can be measured. The diameter of Nix is ​​estimated at about 35 kilometers and that of Hydra - 45 kilometers. These sizes led the mission scientists to conclude that their surface is bright, possibly due to the presence of ice.
And what about the other two moons Cerberus and Styx? They are smaller and smaller than Nix and Hydra and it is more difficult to measure their size. Mission scientists will be able to estimate their size when New Horizons transit observations reach Earth at a later date.

More of the topic in Hayadan:

For information on the NASA website

7 תגובות

  1. Wow amazing, that explains why it takes so long to release them, you have to filter out a few decent comments from dozens of spam comments. Are these comments written manually by human commenters? Or something automatic that causes flooding?

    (like spam mail)

  2. checker. For some reason, the rate of freezing of responses increased greatly in the last week, from isolated ones a week to dozens of days.
    my father

  3. Father, I see that Wikipedia was also helped by your article and determined that the diameter of the coffin is 1280, which is not true at all. The diameter of the coffin is 1208. The Hebrew Wikipedia should be updated.

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