How to Observe a Dwarf Planet as an Amateur Astronomer - by finding Ceres

Dwarf planets are largely ignored in amateur astronomy probably because they are not as impressive as some of the beautiful nebulae or galaxies in the night sky.

I thought it would be helpful to provide some background information about dwarf planets before I describe what I have observed and how you can observe a dwarf planet yourself.

Many people can probably recall how the concept of dwarf planets came about since, prior to the discovery of Pluto in 1930, there were nine planets in our solar system.

However, when Eris was discovered in 2005 which is slightly bigger than Pluto it put Pluto's status as a planet was put into doubt.

After estimates that there might be one hundred other similar planets yet to be discovered in the outer solar system, what a planet is as a concept needed to be clearly defined for the first time.

What is a Planet

The definition is as follows: a planet must be in orbit around the sun and not a moon, it must be round and have cleared the neighbourhood around its orbit.

Those planets not fulfilling this last requirement are described as dwarf planets.

And so, Pluto was duly demoted, amid many protests to a dwarf planet. Most of the dwarf planets are found in the outer reaches of the solar system, beyond the orbits of Uranus and Neptune.

Such distances pose a problem for the amateur astronomer because they are so far away, they are difficult to see with amateur equipment, very dark skies are required and probably a 12–14-inch telescope to see the dwarf planet Pluto visually. Pluto at its brightest is only a dim magnitude of 13.65.

While the other dwarf planets in the outer solar system such as Eris, require even larger telescopes.

During the protests against Pluto's demotion from planethood, Ceres, located in the much closer asteroid belt, was promoted from asteroid to dwarf planet.

Ceres was discovered in 1801 and was along with several other objects thought to be planets.

This led to a situation in the past when there were a great number of planets in the solar system compared to today before they were reclassified as asteroids due to their small sizes.

However, Ceres is massive enough to be classified as a Dwarf planet.

Ceres is brighter than Pluto and other dwarf planets, with the brightest magnitude of 6.7, which is just out of being visible with the naked eye, but is visible in binoculars and above as well.

Indeed, it was visible in my 50mm finderscope, which is equivalent to a pair of binoculars.

All of this makes Ceres a great target for the amateur astronomer wanting to see a dwarf planet.

So how do you identify a dwarf planet?

Well unfortunately unlike the main planets they cannot be identified from the fact that they have a planetary disc. Instead, they look like a star.

But this should not be surprising. When you realise that Ceres only has a diameter of 946km and is out beyond the orbit of Mars!

So instead, I would recommend first attempting to view Ceres when it is in opposition. This will mean it appears as bright as it can be when observing.

The second tip is to look at a star chart to see its current location in the sky.

The positions of all the planets are constantly changing, so you will want to use a planetarium app if possible, such as Stellarium.

One good technique to find Ceres in the night sky, wait until it is close to something more obvious, like a star or planet, which will act as a signpost.

A low power magnification will allow you to see more of the night sky, as well as be able to see Ceres's movement in the stars.

Ceres appears like a star when you locate it, so to identify it for certain you will need a photograph or drawing for confirmation. Then come back the following night or so and repeat the process.

When comparing the two images, you should notice that one of the stars has moved, and that should be Ceres as shown in the two images I managed to capture over two consecutive nights. As you can see in just one night Ceres has moved quite a bit.

It is also important to capture images or drawings over two nights close together so the movement of Ceres can be observed in both images.

You can also measure the brightness of the dwarf planet between each observation, which may change due to alternating surface features such as Ceres' white spot. This theoretically could be used to indicate the planet's spin speed.

For some people accustomed to seeing episodes on the more visually impressive objects of the night sky, this may seem a bit of an anti-climax. Being able to confirm that I had observed a dwarf planet was a highlight of my amateur astronomy journey.

To see what Ceres looks like you can watch the episode below.

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