Constellations that are prominent in the south at around midnight at this time of the year include Gemini, Cancer, Canis Minor, and the “head” of Hydra. Although these constellations are not particularly rich in easy targets for binoculars or small telescopes, this collection of constellations does contain some deep-sky objects that are worth hunting down with modest amateur equipment. In addition to exploring these celestial objects, astronomical events to look forward to in January 2020 includes a partial lunar eclipse, and the Quadrantids meteor shower.
The Moon in January 2020
Dedicated lunar observers will have an opportunity on January 10th to test their observing skills in terms of gauging the amount of darkening of the Moon’s surface when a partial eclipse of the Moon occurs. Note that no part of the Moon will be in complete shadow for the slightly more than 4-hour long event that will be visible from Europe, most of North America (including Alaska), Asia, Africa, and Australia.
Although the eclipse occurs three days before perigee, which will make the Moon appear about 2.6% bigger than “normal”, the best that could be expected is a subtle shadow gradient across the lunar surface that might go unnoticed by casual observers. The principal reason for the slight darkening of the Moon is the fact that during a penumbral eclipse the Earth blocks out only a small part of the Sun’s light, which does not greatly affect the Moon’s illumination by the Sun.
Moon Phases
| First Quarter | Full Moon | Last Quarter | New Moon |
| January 3rd | January 10th | January 17th | January 24th |
Note that the January 10th Full Moon is the first of the highest Full Moons of 2020. The second highest Full Moon occurs in December.
The Planets
– Mercury will be lost in the Sun’s glare for much of the month. It may become visible very low above the south-western horizon during the last week or so of January when it will set about an hour and 20 minutes after the Sun.
– Venus will set about four hours after the Sun during most of January, but while it is shining, it will be the brightest object in the sky. Venus will be in close conjunction on the 27th of the month with Neptune, one of the dimmest objects in the solar system. The best views of this starkly contrasting pairing will be had with a small telescope at low power; look for Neptune as a faint blue-white point of light about 5 minutes of arc to upper rightward of Venus.
– Mars rises about three hours before the Sun throughout January close to the red giant star Antares, the brightest star in the constellation Scorpius. Note that although Mars will be shining at magnitude +1.5, the fact that Antares is closer to the horizon than Mars means that it might be difficult to tell the star from the planet since both objects will have similar magnitudes and colors. However, the best time to make a good comparison between the star and the planet occurs during the middle of the month, when both objects will be within 10 degrees of the south-south-western horizon, with Mars being slightly higher than Antares.
– Jupiter was at superior conjunction with the Sun on the 27th of December, and the King of the planets will therefore slowly become visible towards the end of January. However, be aware that when Jupiter does become visible, it will rise only an hour or so before the Sun, and will rise to no more than about three degrees above the southeastern horizon. Therefore, great care must be taken when trying to spot the planet with binoculars as the Sun might appear above the horizon unexpectedly.
– Saturn is now approaching a point of conjunction with the Sun, and will therefore not be visible during the entire month of January.
– Uranus is still visible in the constellation of Aries until about 2 hours after midnight (GMT). Note that since Uranus is now approaching the threshold of naked-eye visibility at magnitude +6.0, small telescopes or large binoculars might be needed to spot the planet’s 3.8-arcsecond disc.
Meteor Showers in January’s Night Sky
The Quadrantid Meteor Shower runs from about the 28th of December to about the middle of January. The shower is expected to peak on the night of the 3rd/4th of January this year when a maximum hourly rate of about 80 or so meteors could be expected- largely because the Moon will not obtrude unduly.
Note that the Quadrantids is a relatively young shower that consists of debris from an asteroid designated as 2003 EH1 that broke up about 500 years ago. As a point of interest, the name “Quadrantids” derives from Quadrans Muralis, the name of a now-defunct constellation that once existed in the area where the northern part of the constellation Boötes is now located. Therefore, the radiant of this shower is a point just to the leftward of the handle of the Plough (Big Dipper).
Deep Sky Objects to Look for in January 2020
Below are some details of a few prominent deep-sky objects that can be observed using modest amateur equipment in January 2020.
Messier 35 (NGC 2168)
Located about 2,800 light-years away in the constellation Gemini, this cluster has an apparent visual magnitude of 5.30 and covers an area about as big as the apparent diameter of the Full Moon. It is interesting to note that while the M35 star cluster appears to be relatively densely populated, the number of member stars remains largely undetermined. For instance, 305 stars appear to be members with a 95% or higher probability of being members of the cluster proper, while another 4,349 stars have only a 50% probability. Nonetheless, based on their variable radial velocities, 64 stars in the cluster have been conclusively shown to be members of binary or multiple star systems. The cluster also appears to contain at least four known chemically peculiar stars, but the membership status of these four stars remains undetermined.
Jellyfish Nebula – IC 443 (Sharpless 248)
Another notable deep sky object in Gemini is the Jellyfish Nebula. Located at a distance of about 5,000 light-years from Earth, this 70-light-year-wide nebula is a suspected remnant of a particularly violent supernova event that occurred between about 3,000, and 30,000 years ago.
Apart from the fact that the supernova event had created a neutron star from the massive progenitor star, the most interesting aspect of the Jellyfish Nebula involves the fact that it consists of two discrete parts that have greatly different radii, emissions, and structures. For instance, the north-eastern part of the nebula is not only the bigger of the two parts, it also emits light from neon, iron, oxygen, and silicon atoms. All of these are largely absent from the smaller south-western part, which emits light from excited hydrogen gas and various types of super-heated dust.
Beehive Cluster (Praesepe, Messier 44, M44, NGC 2632, Cr 189)
Also known as “Praesepe”, the Beehive Cluster is visible with the naked eye, being located only about 577 light-years away in the constellation Cancer. All told, the cluster contains at least 1,000 stars, about 63% of which are red dwarf stars, while about 30% are Sun-like F, G, and K-type stars. Note that while the brightest stars in the cluster are massive blue-white stars with magnitudes of between 6.0 and 6.5, the brightest objects in this image are over-exposed, unrelated foreground stars, hence the diffraction spikes.