It’s Easy to See Ceres, the Full Strawberry Moon meets Mars after Saturn, and the Ringed Planet Peaks for 2018!
The Moon and Planets
To begin this week, the moon will be shining brightly in the evening sky as a nearly full (waxing gibbous) globe. Remember to pull out your binoculars or small telescope and look along the boundary separating the lit and dark sides. That’s where the most dramatic moonscapes are. Because the moon reaches its full phase on Thursday at 12:53 am EDT, the moon will look full on Wednesday evening and slightly past full on Thursday night.
The June full Moon, colloquially known as the Strawberry Moon, Mead Moon, Rose Moon, or Hot Moon, always shines in or near the stars of southern Ophiuchus (the Serpent-Bearer). Because the Moon reaches full when it is opposite the sun in the sky, full moons always rise in the east as the sun sets, and set in the west at sunrise. Since vertically impinging sunlight casts no shadows on a full moon, all of the surface brightness variations are generated by differences in the reflectivity, or albedo, of the lunar surface rocks.
In the southeastern sky after dusk on the Wednesday evening, the full moon will sit one finger’s width above bright, yellowish Saturn. The two objects will cross the sky together during the night and will easily fit within the field of a small telescope at low magnification. Meanwhile, the moon’s separation from Saturn will noticeably increase as the moon slides eastward in its orbit during the night.
The large open star cluster called Messier 24 will sit a few finger widths above (to the northeast of) the moon and Saturn. The cluster, also known as the Small Sagittarius Star Cloud, is three times wider than the moon! Try to see it using binoculars, or wait for the moon to move away on the following nights and use Saturn to find it then.
After midweek, the Moon will slide east, rise later, and begin to wane — with the dark region growing on the moon’s western (our right-hand) side. About 11 pm local time on Saturday night, bright red Mars will rise in the east with the waning gibbous moon shining 4 finger widths to the upper left (northeast) of it. Both objects will fit into the field of view of binoculars. By dawn, the pair will appear low in the southwestern sky.
Venus continues to catch our eye in the western evening sky this week while it continues to swing away from the sun — and it will still get brighter! The planet will be setting at about 11:30 pm local time all week because it is travelling east while the entire sky is shifting west, holding it in place. Venus is gradually growing larger as it moves towards Earth. In a small telescope, the planet’s disk will not look round. Instead, it will exhibit a gibbous (70% illuminated) phase.
This is the best week to see elusive Mercury sitting low over the northwestern horizon for a brief period after sunset. It recently peaked in brightness and the best time to look is between 9:45 and 10:15 pm local time. You’ll need a low open horizon because the planet will be only a few finger widths above the horizon (or less).
Jupiter is the bright object you will see shining brightly in the southern sky after dusk this week. Around that time, it will be at its highest elevation (about three fist diameters) above the southern horizon. Over the following five hours, it will move west and descend — setting in the west-southwest about 3 am local time. Once it’s dark enough, look for a bright star sitting just to the lower left of Jupiter. That’s Zubenelgenubi, the brightest star in Libra (the Scales). In binoculars or a small telescope, it splits into a closely separated pair of stars.
On Monday, June 25, and visible between 9 pm (in twilight) and 10:42 pm EDT, the little, round, black shadow of Jupiter’s moon Ganymede will cross (or transit) near the north pole of Jupiter’s disk. On Saturday, June 30 starting at 1:14 am and visible until Jupiter sets, the shadow of Jupiter’s moon Io will transit. A reasonable backyard telescope will show the black shadows, but a very good telescope is needed to see the moons themselves. More shadow transits are available in other time zones around the world.
The Great Red Spot (or GRS, for short) takes about three hours to cross Jupiter’s disk. But the planet’s 10-hour rotation period (i.e., its day) means that the spot is only observable from Earth every 2–3 nights. If you’d like to see the GRS, use a medium-sized telescope (or larger). You’ll have your best luck on evenings with steady air — when the stars are not twinkling too much. The best times to try this week are: Monday, June 25 at 1:18 am and again at 9:09 pm (in twilight, with a Ganymede shadow bonus), Wednesday, June 27 at 10:48 pm, and Saturday, June 30 at 12:27 am. All times are given in Eastern Daylight Time (EDT), so adjust for your local time zone. Try to look within an hour before or after the times I’ve given.
On Wednesday, the Earth’s orbit will carry us between Saturn and the sun. Sitting opposite the sun in the sky (a term that astronomers call opposition), Saturn will be visible all night long, and the planet’s disk will be the brightest and largest (18 arc-seconds) for the year. Planets don’t emit their own light. We see them because the sun’s light has travelled all the way out to them and reflected off their surfaces. At opposition, the reflected light from Saturn will travel for 75 minutes to reach Earth — and our human eyes.
Yellow-tinted Saturn will rise in the southeastern sky at about 9 pm local time this week, just as the sun sets. The ringed planet will be spending the summer of 2018 just to the left of the Milky Way, and just above the Teapot-shaped stars that form Sagittarius (the Archer). Saturn moves over the southern horizon, its highest point in the sky at 1:30 am local time. It will remain visible until about 5 am local time, when it will sit more than a fist’s width above the southwestern horizon. Scientists have recently determined that Saturn’s reflective icy rings formed only a few hundred million years ago — during Earth’s Carboniferous Period, when early dinosaurs roamed our planet!
Mars is getting good now! The Red Planet will be rising in the east just after 11 pm local time this week. Mars will continue to steadily brighten and increase in apparent size (when viewed through a telescope) as the Earth’s faster orbit brings us closer to the red planet until July 31. Mars will reach its highest position, over the southern horizon, around 3:30 am local time, and then remain visible until just after 5 am.
Distant blue Neptune, among the modest stars of Aquarius (the Water-bearer), is observable in telescopes in the eastern sky after it rises around 13:30 am local time. This week, look for the magnitude 7.9 planet sitting one finger width to the right of the naked eye star Phi (φ) Aquarii and about five finger widths to the left of brighter Hydor (Lambda Aquarii).
Blue-green coloured Uranus is visible in binoculars, if you know where to look. It, too, is in the eastern pre-dawn sky, located about four finger widths to the left of the modestly bright star Torcular, which is down toward the “V” where the two cords of Pisces (the Fishes) meet. I posted sky charts for Uranus and Neptune here.
It’s Easy to See Asteroids — Sometimes
Here’s a very easy way to see an asteroid with your own eyes. After dusk on the evening of Wednesday, June 27, the large dwarf planet (formerly asteroid) Ceres will sit only 9 arc-minutes (or less than one third of the moon’s apparent diameter) above the bright, visible double star Algieba in Leo (the Lion). Algieba marks the throat of the lion, midway along the backwards question-mark that forms the front of the constellation. After dusk, the lion will be positioned over the western horizon and tipped with his face downward to the right. I’ll post a sky chart here.
Use binoculars to look for Ceres as a little, star-like object just a short distance above Algieba. A small telescope at medium-high magnification will show Ceres and Algieba’s close-together pair of distant stars together in the same field of view.
After a determined search by many astronomers who were looking for a theorized missing planet, Ceres was the first asteroid ever discovered, by Giuseppe Piazzi in Palermo, Sicily, on January 1, 1801. It was named after the Roman Goddess of Agriculture. (The same name gave us the word “cereal”!) Ceres was originally given planet status, orbiting as it does between Mars and Jupiter. But calculations of its 950 km diameter, and later discoveries of countless additional bodies in the asteroid belt, led to its demotion to queen of the asteroid belt. But in 2006, the same rules that demoted Pluto to dwarf planet status promoted Ceres to the same class of objects. Good luck!
As I mentioned last week, another asteroid, the minor planet (4) Vesta, is now visible all night long, and appearing about its brightest (magnitude 5.33) for the year — within reach of binoculars and small telescopes. Look for the object above the Teapot-shaped constellation Sagittarius (the Archer), about a fist’s diameter to the upper right of Saturn.
Astronomy Skylights for this week (from June 24th, 2018) by Chris Vaughan.
Keep looking up to enjoy the sky!
