Introduction and Monthly Reminders
September has started off cooler and much more pleasant to be outdoors. Northern Utah experienced some decent-sized thunderstorms and a cold front, which dropped the temperatures by over 20º F. The cold front brought heavy winds, which made the atmosphere unstable, creating poor telescope views and astrophotography image quality unless the tripod was securely mounted. Before the storms rolled through, I was able to capture some great images of the night sky that I will share in a future post.
The remainder of the month is projected to remain cool with a chance of more rain storms. Astronomers will still be able to enjoy Neptune reaching opposition and the zodiacal light, weather permitting. Observers in Utah can also watch the Moon occult Neptune in the early morning hours on the 18th.
Dwarf Planets
Many individuals were upset about the reclassification of Pluto from the ninth planet to a dwarf planet in 2006. Since its discovery in 1930, Pluto had not even completed a full orbit of the Sun before this demotion occurred. Some of the disgruntled created memes, t-shirts, and other propaganda depicting how Pluto went from angry to sad to lonely for not being considered a planet. Fortunately for Pluto, it is not alone! There are currently four other dwarf planets orbiting our Sun, and there are over 100 other likely candidates. But why was Pluto demoted, and what distinguishes a dwarf planet from a regular planet?
After the discovery of Pluto in 1930 and prior to the reclassification of it as a dwarf planet in 2006, several other objects were discovered to be similar in size to Pluto. The previous ninth planet is actually smaller than the Earth’s own Moon and a few of the Moons of Jupiter and Saturn. However, size is not the only thing that distinguishes dwarf planets from other planets. A planet must orbit its parent star like the Earth orbits the Sun. A planet must be relatively round, and its gravity must be sufficient enough to have cleared its orbit of all other objects that are similar in size. Pluto and the other dwarf planets orbiting the Sun failed the last criteria of clearing their orbit of similarly sized objects.
The International Astronomical Union (IAU) is a worldwide organization of astronomers. It is the group that votes on and decides what makes a planet a planet and what makes dwarf planets what they are. The closest dwarf planet to the Sun is Ceres. It resides in the asteroid belt between Mars and Jupiter. It was discovered in 1801 and was thought to be an asteroid. Fast forward 214 years when the Dawn spacecraft from NASA visited this rock to determine its size and composition. Ceres makes up about a quarter of the mass in the asteroid belt, is primarily spherical but is roughly 14 times smaller than Pluto. Given this information, Ceres was promoted from an asteroid to a dwarf planet.
Pluto is the most famous of the five dwarf planets and lies, on average, 40 AU from the Sun. This distance places this dwarf planet in the Kuiper Belt. It was visited by the New Horizons mission in 2015. This mission was able to capture several images of Pluto, including the one of the heart shaped feature on its surface, seen below.
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| The heart of Pluto was taken in 2015. |
Even at the great distance of 40 AU, where it takes sunlight over 290 minutes to reach this dwarf planet, Pluto is the second closest dwarf planet to the Sun. One complete orbit of the Sun takes 248 Earth years while one day lasts about 6 Earth days.
Haumea is also located in the Kuiper Belt, orbiting the Sun at 43 AU. It was discovered in 2004 by two separate astronomy teams. Haumea is about the same size as Pluto but is oval shaped, much like a football. One year on this dwarf planet is about 285 Earth years. However, a day is only four earth hours, meaning Haumea is one of the fastest-rotating large-bodied objects discovered to date. Haumea is also the first object found in the Kuiper Belt to have a ring system.
Makemake is about half the size of Pluto and resides in the Kuiper Belt, roughly 46 AU from the Sun. One year on Makemake is equal to 305 years on Earth, while a day is similar to an Earth day at 22 hours. Not much is known about this dwarf planet except that it is brownish in color, similar to Pluto.
Eris is currently the fifth and last known dwarf planet in our solar system. It also resides in the Kuiper Belt at a distance of 68 AU. It takes Eris 557 Earth years to complete one orbit, but its day length is similar to Earth's at 25.9 hours. The discovery of Makemake and Eris made the IAU redefine the classification of planets, hence demoting Pluto to dwarf planet. For those upset by this demotion, remember that dwarf planets are planets, too!
Check back soon for my next post!
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| Now get outside and look up! |
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