Clear nights have been rare this fall in the Vancouver area. In October, we set a record for rain on 28 out of 31 days while normally there are about 15 days of rain. November was not better with 25 rain days – the 4th most rain days for November. But I took advantage of a recent clear night last Wednesday (Dec 7th) to get in some imaging of the Moon and the Pleiades.
The cool weather presented some challenges. At -3°C, the temperature was slightly below freezing but quite manageable for me with a good jacket, boots, and gloves.
My equipment didn’t fare as a well.
The first problem became apparent when I went to polar align my mount. I built a concrete pier topped with an aluminium adapter last summer but had removed the CGEM mount head during the two months of rain. So I reattached the mount head and stuck my 80mm Esprit refractor on it early to allow it to cool down. A couple of hours later, I went to polar align the mount and found that I could not adjust the azimuth at all: a thin layer of frost and snow on the adapter likely froze the mount head to the adapter and prevented it from moving. Poor polar alignment meant that I would have to use short exposures for imaging – not a problem with the moon at all and I could try stacking lots of short exposures for the Pleiades (lucky imaging).
I powered up the CGEM mount (it is a goto mount) and looked at the LCD hand controller to work through the initialization procedure. The second line of display on the hand controller appeared garbled and unreadable – apparently, LCDs are sensitive to temperature as the fluid tends to “stiffen” in the cold. I managed to get through the initialization and start tracking mostly by pressing “enter” to accept the defaults but decided to manually slew the mount rather than trying to do a star alignment and using the goto capabilities.
Finding the moon was easy, and I managed to take a few images though the camera battery only lasted about ½ an hour in the cold. Fortunately, I had a spare battery charged and ready to go for the Pleiades.
Finding the Pleiades was more difficult. The Pleiades are an easy naked eye object even under normal city light pollution. But my yard in Coquitlam was still covered with 10-15 cm snow from the previous day. It was amazing how much light reflected off the blanket of snow and made it difficult to spot the Pleiades. I did manage to find them after a few minutes of random hunting – thank goodness the 80mm Esprit has a wide field of view!
I ended up getting 45×15 second sub-exposures of the Pleiades but, as a final insult, part way through my imaging, the neighbours decided that the cool night was a good time to use their outdoor hot tub and turned on a bunch of bright exterior lights that shine into my yard. Ah well, I still stacked and processed the sub-exposures to get an image that shows some of the nebulosity around the Pleiades.
It is a good time to try to observe the dwarf planet Ceres as it is just past opposition and is located between the constellations Cetus and Pisces. The clear sky clocks don’t look favourable over the next few days but if the clouds part then take a look towards the south about 30 degrees above the horizon around midnight. If it remains cloudy read on to learn more about the Ceres.
Ceres is, by far, the largest object in the asteroid belt that lies between the orbits of Mars and Jupiter. Like Pluto, Ceres was originally classified as a planet shortly after it was discovered in 1801 by Italian astronomer Giuseppe Piazzi. It was “demoted” to an asteroid (“star-like” object) by William Herschel in 1802, and was classified, along with Pluto, as a dwarf planet in 2006.
NASA’s Dawn spacecraft went into orbit around Ceres in March 2015. Images from Dawn, as it approached Ceres highlighted bright white spots, within the Occator Crater whose composition puzzled scientists. Recent studies of spectroscopy data sent back by Dawn have indicated the presence of ammonia-rich clays. This suggests that Ceres may have formed in the Kuiper belt, past Neptune, and migrated inward as ammonia-bearing salts have been detected in the outer solar system such in the geysers of Enceladus (a moon of Saturn). Other studies conclude that recent geologic activity was probably involved in the creation of the bright spots.
In Sept 2016, NASA scientists released a paper in Science that claims that Ahuna Mons is the strongest evidence yet for the existence of ice volcanoes. Cryovolcanoes are similar to regular volcanoes except they spurt out a mixture of salt and water rather than lava. The ejected salty water freezes and creates an icy dome at the top, which, for the NASA scientists is one of the telltale signs that Ahuna Mons is a cryovolcano.
Ahuna Mons appears to be quite young. It likely formed in the last 200 million years or so. In contrast, Ceres probably formed about 4.6 billion years ago like the rest of the solar system.
The heating process that leads to this cryovolcanism is not clear – Ceres doesn’t experience tidal heating; its insides are not heated by another object’s powerful gravitational pull as Ceres never gets close enough to a giant planet. So Ceres is again similar to Pluto in that the energy driving cryovolcanism must come from the dwarf planet’s internal heat, likely the heat left over from its long-ago formation along with some contribution from radioactive decay.
Other interesting facts:
Ceres was the first object considered to be an asteroid.
Plumes of water vapour shooting up from Ceres’ surface were observed by the Herschel Space Telescope.
Ceres accounts for one-third of the mass in the asteroid belt yet it is still the smallest dwarf planet.