ESA Mars Express TeamApr 08, 2014

Opposition time for Mars, and several months of dancing with the stars

This article was originally posted on the Mars Express blog and is reposted here with permission. It was written by Michael Khan at ESOC.

Once again, it's opposition time. While the Earth requires one year to complete a full revolution, a Mars year, due to the planet's wider orbit, lasts 687 days. As Earth and Mars are plying their separate orbits with different speeds, the distance between each varies considerably with time. But once in a period of just over two years, they are aligned in what astronomers call an opposition. On that date, seen from Earth, Mars is located almost exactly in the direction opposite from the Sun, so stargazers can see the Red Planet high in the sky at midnight, and closer and brighter than at any other time.

The distance from Earth to Mars during the years 2000 to 2019
The distance from Earth to Mars during the years 2000 to 2019

Because the Mars orbit is eccentric (i.e., it is elongated rather than circular), not all oppositions are equal. Many of you will remember the one in the autumn of 2003, when Mars approached Earth to as close as 56 million kilometres. It appeared like a surprisingly bright red star. In 2014, opposition takes place today, but again because of the eccentricity of the orbits, closest approach will in fact be a few days later, on 14 April. The distance from the Blue to the Red Planet will then be 92 million kilometres – two-thirds more distant than in 2003, so Mars will appear only a third as bright as it did 11 years ago.

Admittedly, observing Mars in the night sky is a lot less spectacular than it was, and it will again be, as soon as the year 2018. But still, you should have a look. It's impossible to miss, all the more so because right now it is close to the star Spica in Virgo; Spica is special, because it is in fact not one, but two stars – and big ones at that – that are orbiting a common centre of mass at very close quarters. Spica is interesting, it's massive, it's bright...and it's blue! So you currently have the brilliant blue Spica and the brilliant red Mars both in approximately the same direction in the sky.

Surely you don't need any more coaxing than that to get you to do some stargazing – or do you? All right then...let's see which celestial bodies Mars will encounter in the course of the year. (Of course, we are talking about apparent encounters only, where the bodies involved appear to be separated by only a small angle. In terms of actual spatial distance, the distances will still be 'astronomical,' with the exception of comet C/2013 A1 Siding Spring, which will buzz Mars on 19 October 2014. But as avid readers of our blog, you already know that).

Here is a list of star parties to which Mars has been invited this year. You are welcome to join – no need to feel like a gate crasher. All these events will be easily visible to the human eye. Using a pair of binoculars or a telescope is optional, but not mandatory.

Click on any of the charts below for a larger view.

On 14 April, the full Moon encounters Mars and Spica
On 14 April, the full Moon encounters Mars and Spica Image: Stellarium

This is an easy one for starters. And what's more, it happens on the day, 14 April, when Mars is closest to the Earth. Directly in the south around midnight (all times in the star charts below are given in GMT) the full Moon will intrude between Mars and Spica.

May 15: Solar System Parade
May 15: Solar System Parade Image: Stellarium

A fine sight, and one you won't be treated to often. Shortly after sunset on 15 May – the last faint traces of dusk will still be lingering in the West – you will see not one, not two, not three, no four? Yes! Yes, four planets at once, sweeping a magnificent arc called the Ecliptic through the night sky. The parade is led by the rising full Moon in the East. Then follow Saturn, Mars, Jupiter and, as an extra bonus, little Mercury, in the West. Mercury is not an easily observable planet at any time, but to see it with so many other members of the Solar System is truly rare.

14 July: Mars and Spica getting really close
14 July: Mars and Spica getting really close Image: Stellarium

On 14 July, Mars and Spica will be separated by an angle of only a bit more than one degree. You will be able to appreciate their colour contrast.

25 August: Saturn meets Mars
25 August: Saturn meets Mars Image: Stellarium

On 25 August, the Red Planet meets the ringed world in the evening sky.

31 August: The Moon joins Saturn and Mars
31 August: The Moon joins Saturn and Mars Image: Stellarium

In the evening evening of 31 August, the waxing half Moon will get very close to Saturn, while Mars watches on.

28 September: Mars meets Anti-Mars
28 September: Mars meets Anti-Mars Image: Stellarium

Antares, a red giant star in the constellation Scorpio, was named 'counter Mars' by the ancient Greeks because of its similarity to the Red Planet in colour and brightness. Check it out – on 28 September, you will see both at one glance, with the Moon and Saturn watching on.

19 October: Finally! Siding Spring encounters Mars
19 October: Finally! Siding Spring encounters Mars Image: Stellarium

Those of you who live in the Northern hemisphere won't have seen much of comet C/2013 A1 (Siding Spring). Conversely, as the comet is arriving from way down South in the Solar System, viewers in the Southern hemisphere will have a really good view throughout the summer (albeit not without a telescope). We northerners will see it only before its encounter with Mars. The window of opportunity is rather short – it starts in mid-October and extends over only half an hour or so per day, at most. We have to catch it after sunset, when the sky is dark enough, but before Mars and the comet will also set. And you will still need a telescope, unless all predictions of how the comet's activity will evolve turn out to be false, which of course is entirely possible. With comets, be prepared for the unexpected.

At least it should not be difficult to find it on 19 October, the day of the Mars encounter (closest approach). All you have to do is find Mars – the comet must then be in the field of view of your telescope.

Here in Germany, will not be able to observe Mars and the comet at the time of closest approach, 18:30 GMT. By then, seen from where we are, both will have set. But we can certainly try to see it during that day.

So, bye for now and 'Clear skies!' as star gazers greet each other...


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