New Horizons

Today, July 14th, 2015 will go down as a major milestone in humanity exploration of the cosmos. After 85 years of pondering what Pluto actually looks like, we know and will learn more in the upcoming days and months.

New Horizons made its closest approach to Pluto at 11:50 UTC, allowing us to see it for the first time with clarity. By now, many of you have probably seen the images of Pluto with its heart-shaped surface feature, which was actually hinted at by Hubble images taken between 2002 and 2003.

If you look at the 180° face, a hint of the heart-shaped feature seen below may now be apparent.

This image of Pluto from New Horizons’ Long Range Reconnaissance Imager (LORRI) was received on July 8, and has been combined with lower-resolution color information from the Ralph instrument.

Via NASA/New Horizons

 

And from images taken on July 11, a composite of Pluto with its companion Charon.

A portrait from the final approach. Pluto and Charon display striking color and brightness contrast in this composite image from July 11, showing high-resolution black-and-white LORRI images.

Via NASA/New Horizons



For more information, follow New Horizons on Twitter and here, Alan Stern, Principle Investigator for New Horizons.

Also, visit the New Horizons page for updated images as they are posted.

 

New Horizons

On December 6, New Horizons "woke up" for the last time. It is on its last 162 million mile journey to an object in our solar system that has never been visited by Earth spacecraft until now.


Pluto will be visited for the first time and we will have the best resolution images of Pluto ever by mid-May. By July of 2015, New Horizons will finally arrive at the Pluto system and we will also have close-up images of five of its major moons (or co-orbital bodies): Charon, Nix, Styx, Hydra, and Cerebus.

New Horizons Instrumentation

Image Credit:

NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Read more about the mission at NASA.gov

Pluto and Charon

Pluto has satellites, or more correctly, objects that co-orbit the Sun with Pluto. The largest of these objects is Charon, which is half the size of Pluto. Why do I say it co-orbits around the Sun rather than orbiting around Pluto? It has f\to do with something called the barycenter of the two bodies.

The easiest way to explain barycenter is it is the balance of mass between the two objects. Think of a seesaw (or teeter-totter) with a person on either end. If both people are the same weight, the seesaw is perfectly balanced with the center of mass being at the fulcrum of the seesaw. However, if one person weighs more then the other person, the seesaw is no longer in balance, and the center of mass shifts towards the heavier person. To get the seesaw back in balance, the heavier person needs to move closer to the fulcrum. Therefore the center of mass is closer to the heavier person.

The same thing is true in orbiting objects. In the Earth-Sun system, the center of mass is closer to the Sun. In fact, the Sun is so much more massive, that the barycenter is within the Sun itself. This is true for all planets orbiting the Sun. In the Earth-Moon system, the Earth is about 83 time more massive than the Moon, so therefore the barycenter for the Earth-Moon is about 4700 km from the center of the Earth (about 75% the Earth's radius). In general, you can look at all the planets and their moons and find the same thing: the barycenter for a planet-moon system will lie within the radius of that planet. (The Jupiter-Sun system is an exception. However, the barycenter is just outside the surface of the Sun.)

However, Pluto and Charon are different. Charon is about half the mass of Pluto. Therefore, the barycenter for Pluto and Charon is a third of the total distance between the two planets, well outside Pluto's radius. This gives us another argument against Pluto being a planet. Charon is not truly a satellite of Pluto since their center of mass is not within Pluto. Pluto and Charon are more like co-orbiting bodies around the Sun.