WHEN STARTING OUT IN STARGAZING, most people are particularly keen to spot the planets, five of which are visible to the naked eye – Mercury, Venus, Mars, Jupiter and Saturn. The problem is that, to the novice, planets and stars look pretty much alike. An easy way to identify planets is to find them in relation to nearby bright stars or the Moon, and then watch as they change their positions slightly as each night passes. The information below will help you spot planets using this method.
Except where indicated, all of the phenomena described here can be seen with the unaided eye. Dates and times are for the Australian Eastern Summer Time zone, and sky directions are from the point of view of an observer at mid latitudes in the Southern Hemisphere.
The Moon is in its ‘new’ phase (the opposite of ‘full’) tonight at 10:14pm. This means that, seen from Earth, it is in the same direction as the Sun, and therefore won’t be seen all night – which is good for stargazing, as the absence of its light will make fainter objects easier to see.
Today at 8:01am, the Moon will be at the closest point – called perigee – in its elliptical orbit around the Earth. The distance between the centres of the two bodies will be 356,921 kilometres.
Today the Earth reaches perihelion, which is the point at which our planet is closest to the Sun during its orbit. The distance separating the two bodies is 147,089,638 kilometres. Note the similarity between the words perigee and perihelion – perigee is used for anything orbiting the Earth (‘peri’ coming from the Greek for ‘around’, while the ‘gee’ part derives from gaia, the Greek word for Earth), while perihelion is used for anything orbiting the Sun (the ‘helion’ part coming from ‘Helios’, the ancient Greek god of the Sun).
There’s a common misconception that the Earth’s changing distance from the Sun (it varies from about 147 million to roughly 152 million kilometres over the course of the year) is responsible for giving us our summers and winters. This is wrong, and a few moments thought shows why. Taking perihelion as an example, the misconception says that with the Earth being at its closest point to the Sun, our planet should experience summer. Well, it’s certainly true that perihelion occurs when it is summertime in the Southern Hemisphere… but what season is it in the Northern Hemisphere? It’s winter. And why is it winter and not summer? Because perihelion has nothing to do with our seasons. The seasons are caused by the tilt of the Earth’s axis of rotation, which sees the Southern Hemisphere tilted toward the Sun at the end of the calendar year, and the Northern Hemisphere tilted away. Six months later it’s the other way around – the north is tilted toward the Sun (and thus the northern summer and southern winter are in the middle of the calendar year) and the south is tilted away.
It is first quarter Moon today at 2:39pm. A few days either side of first quarter is a good time to look at the Moon through a telescope, as the sunlight angle means the craters and mountains throw nice shadows, making it easier to get that 3D effect.
Tonight, the almost-full Moon will be just below the star Aldebaran, the brightest star in the constellation Taurus. Aldebaran is a red giant star roughly 44 times as big as the Sun, located about 65 light-years from Earth. Have a look to the left of Aldebaran and you’ll see a beautiful, broad group of stars in a V-shape. These are the Hyades. If you have a pair of binoculars, take a look; you’ll be amazed by the beautiful sight of these sparkling stars! (A little further to the left, or west, is an even more beautiful cluster of stars – the Pleiades. See the diagram for its location.)
Tonight the almost-full Moon will be just above and to the right of what looks like a very bright star, but is in fact the planet Jupiter – the largest planet in our Solar System. If you have a decent pair of binoculars (ie. anything bigger than opera glasses), train them on Jupiter and you should be able to see its shape and perhaps even some of the ‘banding’ of the atmosphere (the planet’s different weather zones). You should also be able to see up to four tiny, bright pinpricks of light – these are the famous moons discovered by Galileo. You might see one or two on one side of Jupiter, and the others on the other side. (If you take a look in the late evening on January 18, you’ll see them all on the same side.)
Full Moon occurs today at 3:52pm. When the Moon is full, it rises in the east around the same time as the Sun is setting in the west, which means it will be visible all night long. This is great for finding your way around in the dark, but the Moon’s glare is generally not welcomed by stargazers as it makes fainter objects harder or impossible to see.
Still on the subject of the Moon, today at 12:54pm it will reach apogee (the opposite of perigee), which is the farthest point in its orbit around the Earth. The distance separating the centres of the two bodies will be 406,536 kilometres.
If you’re awake around midnight, look out to the east and you’ll see the Moon with a reddish star just below it. That ‘star’ is actually the planet Mars. Mars is a small planet, so you need at least a medium-sized backyard telescope to get any decent sort of view of it. But even as you gaze at it with the naked eye, stop and think for a moment – right now there are two missions on their way to Mars (NASA’s MAVEN and India’s Mars Orbiter), plus there are three orbiters and two operational rovers already working at or on the Red Planet. When the two new spacecraft reach their destination in September 2014, Mars is going to become a busy place!
It is last quarter Moon today at 4:19pm. When you take a look tonight, you’ll notice that Moon has moved a bit since last night (as a result of its slow crawl around its orbit), and Mars is now above and to its left. But directly above the Moon is a bright star called Spica, which is the brightest star in the constellation Virgo. Spica is a blue giant star located about 260 light-years from Earth.
If you’re awake in the early hours after midnight, you’ll be rewarded with the view of the just-less-than-half Moon down near the eastern horizon, with a brightish ‘star’ just above it. That’s not a star, it’s the planet Saturn. If you have access to a small telescope, train it on Saturn and you’ll its magnificent system of rings.
If you’re up before the sunrise today, look out to the east and you’ll see a very thin crescent Moon. Just below it is what looks to be a very bright star, but is in fact the planet Venus. After the Sun and the Moon, Venus is the brightest object in the sky.
The Moon reaches perigee today, with the distance between the centres of the Earth and Moon being 357,079 kilometres.
New Moon occurs for the second time this month, at 8:39am
Here are some more great sources of southern stargazing information:
If you have any questions or comments on the night sky, we’d be happy to answer them. Please use the Feedback Form below. Happy stargazing!
Images courtesy IAU.
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