The Hot Little Planet Peaks in Visibility, and the New Moon mounts a Messier Marathon!
A Spectrum of Stars
If you missed last week’s guide to seeing the colours of bright winter stars, it’s here.
For about half an hour after dusk during the period between now and the new moon on March 17, look west-southwest for a broad wedge of faint light rising from the horizon and centered on the ecliptic. This is the zodiacal light — reflected sunlight from interplanetary dust particles that orbit in the plane of the solar system. Try to observe it from a location without light pollution, and don’t confuse the zodiacal light with the brighter Milky Way to the northwest. I posted a beautiful picture here.
The Moon and Planets
Between today (Sunday) and Friday, the old crescent moon will appear low in the southeastern pre-dawn sky — growing slimmer and also moving from a fully dark sky into the pre-sunrise twilight. The shallow tilt of the morning ecliptic will cause the moon to rise at roughly the same time for several mornings in a row — just as the Harvest Moon does during autumn evenings. The moon reaches its new phase on Saturday morning, giving the coming weekend dark skies that are ideal for seeing the best deep sky objects. (More on that later.) Your first chance to spot the freshly minted young moon occurs Sunday evening after sunset, when its very slim crescent will linger briefly over the western horizon.
Extremely bright Venus continues its escape from the western evening twilight this week. You can look for its bright bauble well above the western horizon after sunset, until it sets at about 8:30 pm local time. Much dimmer Mercury is easy to see this week. It will sit about four finger widths to the upper right of Venus. On Thursday evening, Mercury will reach greatest eastern elongation, its widest separation east of the sun. Viewed in a telescope the hot little planet will exhibit a waning half-illuminated phase, while Venus will be nearly fully illuminated. The best viewing time for Mercury falls between 7:45 and 8:45 pm local time.
Dim and distant Uranus is located about 17° (1.7 outstretched fist diameters) above the two inner planets, in Pisces (the Fishes). But you’ll need the sky to fully darken before you can see it in binoculars or a telescope.
The pre-dawn planets continue to delight us this week. Extremely bright Jupiter will be rising about 12:15 am local time. It will reach its highest elevation (about three fist diameters) above the southern horizon by 5:30 am local time. And it will continue to catch your eye as you leave for school or work until close to sunrise (about 7:30 am local time).
Reddish Mars is dimmer than Jupiter, but it is steadily brightening as Earth closes our distance from it. Over the next five months, Mars will outshine everything but the king of planets, the moon, and the bright star Vega. For this week, Mars will rise at about 3:15 am local time and appear a bit more than 3 fist diameters to the east (lower left) of Jupiter.
The red planet is steadily moving towards yellowish Saturn — with Mars now only about one fist width to Saturn’s upper right. The ringed planet rises just before 4 am local time, putting it two fist diameters above the southeastern horizon just before the dawn sky begins to brighten. The teapot-shaped constellation of Sagittarius (the Archer) will sit directly below Saturn all year.
Messier Marathon Weekend is Coming!
Charles Messier’s list of the best and brightest showpieces in the night sky is popular with astronomers of all experience levels. During the new moon period in early spring each year, it’s possible for lovers of deep sky objects, who live anywhere on Earth between latitudes 20° south and 55° north, to observe every one of the 110 objects within a single night. For many amateur astronomers, this observing challenge is a bucket list item known as the Messier Marathon. This coming weekend is your chance for 2018!
The Messier list (or catalog) objects are designated by their “M-codes”, M1 through M110 (or Messier 1 through Messier 110). Astronomers commonly refer to the group as the Messiers. Most of these famous objects also have proper names, such as the Whirlpool Galaxy (M51), the Pleiades (M45), and the Beehive Cluster (M11).
The objects in the list are distributed throughout the night sky visible from mid-northern latitudes. (Messier and his contemporaries observed them from Paris.) None of the objects are found in the area between Pisces and Aquarius, so when the sun moves between those two constellations in late March every year, it allows us to see all of the Messier objects between dusk and dawn. The idea of a running a “Messier Marathon” originated in 1979 with another comet hunter, Californian Don Machholz.
To see the fainter Messiers, pick a moonless night within a day or two of the new moon, which occurs this Saturday, March 17. A clear sky all night long is a must, so check the forecast and choose the night that offers the best conditions. If more than one night looks promising, make your attempt on the first night, so you have the option for a second try.
Pick a site free from direct lights and light pollution, with open sightlines to the horizon, especially to the west and the southeast. To improve your site selection, use a star chart, planisphere, or astronomy app to preview where the objects will be, especially the ones that will be observed when they’re near the horizon. A site at higher elevation will also give you more time to observe the low objects. Bring warm clothes, and stock up on snacks and drinks — you’ll be awake all night!
Many Messier objects are visible in binoculars — 10x50 models offer a good compromise between weight and performance. The dimmer objects will require a telescope. A 3-inch diameter (80 millimeter) telescope will work under very dark sky conditions, but a larger aperture telescope will make the job easier. Low power, wide field of view eyepieces are recommended. Be sure to set up your telescope, and organize your other equipment, well before sunset.
To start your marathon, you will need to quickly catch the objects that set in the west after sunset — specifically the dim galaxies M77 and M74. By the time the sky has grown dark enough to see these galaxies, they will be nearing the horizon. It’s a good idea to limit the time spent on the first galaxy so as not to miss the other one. Immediately after viewing those two, you’ll look for M33, the large face-on spiral galaxy in the constellation of Triangulum (the Triangle), and then the Andromeda Galaxy trio of M31, M32, and M110.
From this point, you will have time to work your way systematically across the sky from west to east. As you do so, more objects will rise in the east. By late evening, you should arrive at the Virgo Cluster of galaxies. When you have viewed the 17 objects there, you can take a break until the next group of Messiers rises into view at around 3 am local time. Here’s a website with a recommended viewing order. The objects aren’t ordered simply by their setting time, because brighter objects can be picked out during twilight, while dimmer objects need more darkness. (Be careful not to confuse the viewing order with the Messier number.)
The final wave of objects includes M55, M75, M72, M73, and M2, which rise in the pre-dawn. The last Messier is the globular cluster M30, which will rise in the east as dawn starts to break — so it will be a challenge to see this object. Observers in southerly latitudes will have an advantage because the sun rises and sets more vertically, giving them a shorter twilight period.
Several astronomy organizations will recognize your achievement if you observe all of the Messier objects. The Royal Astronomical Society of Canada will issue an RASC Messier Certificate to members who complete the list and provide documentation. The society recognizes both the Go-to and manual approaches. The Astronomical League will send a Messier Program Certificate to members-at-large or members of affiliated astronomical societies who provide observational notes for 70 objects found without a Go-to telescope. The organization will send a lapel pin and honorary membership certificate for completing the entire list (over any time frame). Both organizations’ websites have information and observing forms to download and print out.
Keep looking up to enjoy the sky! Astronomy Skylights for this week (from March 11th, 2018) by Chris Vaughan.