Pluto and Charon as seen by Hubble Space Telescope

Pluto and Charon Picture – Hubble’s Point of View in 1994

Pluto Pic of the Week Has A Guest Star

Pluto and Charon, starring together!

Should we say a guest moon?
Our library of weekly Pluto pictures is used to include only Pluto, until now. Perhaps it’s because Charon is a Pluto moon and they have a common destiny? Or maybe this is just small talk?

The Hubble Legend

The name Hubble is legendary for two reasons:

1) Mr. Edwin Powell Hubble himself. He was not only the first person to find out that the universe was made of galaxies and Milky Way was an ordinary one of them. But also he initiated categorization of galaxies.

Squeezing those revolutionary discoveries to only few years, Mr. Hubble had no intention to stop there. Consequently, his further analysis framed that when the distance between galaxies is more, they move away from each other faster.
And this led to two very important things in history of science and our knowledge about universe:

The universe was expanding uniformly.

OK, this fact is huge itself. While it is that big for both understanding the universe and obtain better inferences, it had more mind-blowing consequences:

Edwin Hubble
Edwin Powell Hubble. Source: NASA

– In addition, if one rolled back the time for several billion years, she would see the universe forming by a sudden expansion of a minor and extremely dense singularity. And this is later on called and hypothesized as Big Bang Theory.

2) Such extraordinary leaps and the discoverers are always honored in science after years. Hubble’s name was given to the space telescope which was launched on 24 April 1990. And it became one of the best tools that astronomers ever have. Hubble Space Telescope is used to serve with thousands of invaluable observations and discoveries since than.

Hubble Space Telescope
A real photo of Hubble Space Telescope from 2009. Source: NASA

Pluto and Charon In 1994 – Background of Image

As you might guess, the picture of interest is taken by Hubble Space Telescope on 21 February 1994. It was by far the best image of planet Pluto and her moon Charon together, from Pluto discovery up to that time. Hence it was a thrilling news by than.

The shot was taken by ESA’s (European Space Agency) Faint Object Camera equipped on Hubble. During the shot, Pluto and Charon were approximately 4.4 billion kilometers away from lenses.

This camera is removed from Hubble in 2002 for replacement with Advanced Camera for Surveys for more enhanced imaging.

Faint object camera
The Faint Object camera, photographer of this picture of Charon and Pluto. Source: Wikipedia, Credit: Stefan XP

Resolution of Faint Object Camera was stunning for those days. It could distinguish different objects which were 0.05 arcseconds away from each other. This is equivalent to the power to distinguish two different light bulbs in a living room in Western coast of United States by observing them from France!

Pluto and Charon In 1994 – What Do We Actually See Here?

Quality of this image led astronomers to calculate diameters of both Pluto and Charon better than ever: with less than 1% error. Furthermore, the image tells us that the reflectivity of Charon surface and Pluto surface are not the same. And this refers to a slight difference in surface compositions.

Although this picture serves some powerful information about Pluto System, you might think that we didn’t know much about Pluto and Charon in 1994. However this is not completely true.

The truth is, you don’t need to send a spacecraft close to a planet in order to understand its behaviour. You just need to know what kind of cameras/detectors you need to choose. Additionally, you need to know how to detect planets’ features, how to use suitable methods and interpret the resulting data properly.

Later and detailed analysis mostly (not completely) confirmed Hubble and other scientific data from 1990’s about Pluto and Charon. In addition, Hubble Space Telescope was on the title again during discoveries of remaining smaller Pluto moons Hydra, Nix, Styx and Kerberos.

Pluto and Charon, New Horizons Image
Pluto and Charon, via New Horizons Spacecraft cameras in 2015. Source: NASA

Pluto and Charon In 1994 – Is What You See a Real Image?

Well, what do you think? The image itself looks like two suns in different sizes face each other. Not like a planet and its moon!

Faint Object Camera had been working with two seperate cameras and detecting near ultra-violet wavelengths together with visible ones. So this image was recorded by the cameras, sent to Earth and combined into a proper image.

As a result, what you see is not a real image, but a digital combination of visible wavelength (which can be considered as real image) and ultraviolet wavelength views of Pluto and Charon.


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