Each month I will describe sights of interest in the night skies of South Carolina. These sights will be broken down into three sections; what you can see with the naked eye, with binoculars, and with a small telescope. The best time to view the night sky is at and around the times when the Moon is not visible, what is known as a New Moon; which will occur this month on July 26th. For July, your best viewing nights will be from July 16th to the 31st. The Star chart below is set for Florence, SC on July 15th at 10 pm.
Can I see a Dwarf planet?
Dwarf planets became popular around 2006, which is when Pluto lost its planet title. I am often asked why Pluto is no longer an official planet. The answer is quite straight forward. As our telescopes became better, astronomers began to find planets beyond Pluto. Haumea was discovered in late 2004, and was smaller than Pluto; did we now have ten planets? Shortly after that in early 2005, Eris was discovered, and Eris was larger than Pluto; eleven planets? A few months later another small planet beyond Pluto was discoved, Makemake; thirteen planets? The trend was obvious; we would be finding more and more small planets.
The astronomers decided to make a set of rules defining what is a planet, and these rules would have to eliminate these new tiny planets beyond Pluto. However, because Eris was larger than Pluto, these new rules would also eliminate Pluto as a planet. The three rules to define a planet were as follows.
- A planet must be in orbit around the Sun.
- A planet must have sufficient mass and gravity to form a sphere.
- A planet must have cleared the neighborhood in its orbit.
The third rule is what eliminated Pluto and all the planets beyond. During the billions of years since the formation of the planets, their significant gravity pulled in all of the debris that existed in their orbit. Smaller planets would be unable to clear their orbital path of significant debris. These rules resulted in the Sun now having only eight official planets. All other planet-like objects are now known as dwarf planets.
An interesting result of these rules, specifically rule 2 was that a dwarf planet was discovered in 1806! This dwarf planet is the asteroid Ceres. The reason for this is that astronomers just assumed that Ceres was just the largest chunk of rock orbiting in the asteroid belt. However, when the Hubble telescope first viewed Ceres, it was found to be spherical. Since it orbits the Sun, and certainly has not cleared its orbit of debris, Ceres became an official dwarf planet. The Hubble image of Ceres is shown below.
There are officially five dwarf planets; in order of size: Eris, Pluto, Makemake, Haumea and Ceres. At this time, there are six other planet-like objects located beyond Pluto, but not enough data is available to classify them as dwarf planets. All dwarf planets except Ceres are known as trans-Neptunian objects (TNOs). Some of the dwarf planets have moons. Some official and unofficial dwarf planets compared to the size of the Earth are shown below.
So back to the original question; can I see a dwarf planet? The image below shows that this month four dwarf planets are in the night sky; see below:
Makemake and Haumea are well beyond the range of any amateur telescope. If you have at least an 8 to 10 inch Dobsonian, then you could see Pluto. This is most difficult, but possible if your use a good astronomy program such as Starry Night. This month Pluto is in its best position for viewing; good luck.
This leaves the dwarf planet Ceres. Ceres can be seen with just a pair of binoculars! If you use 7-10 power binoculars, be sure to brace them on a solid object, or better yet place them on a simple tripod.
Not only can you see Ceres this month, but Ceres is also moving alongside the asteroid Vesta. So if you have never seen a dwarf planet or an asteroid, this is a good month to check these off your viewing list.
To locate Ceres and its companion Vesta, look to the southwest and locate the planet Mars; see chart below set at 10 pm on July 4th:
The red circle on the image shows the field of view for a 10 X 50 mm binocular. Once you locate Mars in your binoculars, move directly up until you see the star Heze in Virgo. Ceres and Vesta will now be in your field of view with either 7 or 10 power binoculars.
If you wish to keep things simple, you know that one of those dots of light below Heze is definitely the dwarf planet Ceres, therefore, you have seen a dwarf planet. If you wish to be a more dedicated amateur astronomer, you will try to locate which dot is Ceres, and which is Vesta. The easiest way to locate these objects is to make a pencil sketch of what you see through your binoculars. The next night check the same area, and you will see which objects moved. July 1st through the 7th, Ceres will be above Vesta. On July 8th, Ceres will be to the right of Vesta. After that, Ceres will be below Vesta. It is also possible to notice the movement of Ceres and Vesta after only two hours on the same night.
Naked Eye Sights: The summer constellations Scorpius and Sagittarius and the summer Milky Way.
Binocular Sights (7 to 10 power): Try to locate the dwarf planet Ceres as it passes with the asteroid Vesta above Mars.
Telescope Sights (60-100mm): The planet Saturn is still nicely placed for viewing in the southwest.
10 Inch Telescope: Try to locate the dwarf planet Pluto; very difficult so use a good astronomy program to help guide your search.
See you next month!