Can I see planets without a telescope? The answer is yes!

Have you ever gazed at the night sky and wondered if an exceptionally bright ‘star’ is actually a planet? Or maybe you’ve seen other ‘stars’, just a little brighter than most, that look subtly different in colour or steadiness of light. The chances are that you have discovered (I use the term loosely) a planet or planets!

They can be tricky to identify, but with a little bit of knowledge and practice, we’ll have you spotting planets in no time at all!

But first – a little background. Stars are VERY different to planets. Stars are enormous spheres of gas and much more massive than planets. They generate their own light whereas planets only reflect light. Planets, being smaller, orbit around stars. The Sun is a star. It appears impossibly bright because it’s millions of times closer than most other stars. The planets of our Solar System (that orbit the Sun) are the planets we can see with the unaided eye.

 

What planets can I see without a telescope?

Since antiquity, people have known of five ‘lights’ that seemed to slowly move among the familiar patterns of stars. In fact, our word planet comes from the Greek word planetes, meaning ‘wanderer’. The visible planets are Mercury, Venus, Mars, Jupiter, and Saturn. The other two, Uranus and Neptune, had to wait for the advent of the telescope for them to be discovered.

 

How do planets differ from stars, and each other, in their appearance?

Two of the planets, Venus and Jupiter, are very bright – Venus especially so. Venus is a brilliant white colour and Jupiter a softer golden white – though both of them are stunning. Mars is usually quite faint but varies a lot. On rare occasions it can outshine Jupiter, as it did in our winter of 2018 when it was a striking orange. Yes, Mars, the ‘red’ planet, is closer to orange! It varies in brightness the most because its relative distance from Earth varies the most. Saturn has a pale yellow tinge, is a lot fainter than Venus and Jupiter, though it outshines most stars. Faint Mercury, hardest to spot of them all, is a greyish white.

The other thing to remember is that stars twinkle, and planets usually don’t. Stars are incredibly remote so their beams of light, being very thin, are easily disturbed as they pass through our atmosphere. This is especially noticeable for bright stars near the horizon – they may even twinkle different colours! The effect on the light from our planets is much less noticeable.

 

Do planets return to the same part of the sky each year like the stars do?

The short answer is no. Think of the stars as far points of light on a background infinitely beyond our most distant planet. The planets, including Earth, orbit our Sun at differing speeds. Earth takes one year to orbit the Sun and so our view of the distant stars changes on a yearly cycle. However, the planets, much closer than the stars, are orbiting the Sun at their own speeds. The combinations of these movements means that we see the planets at different times each year.

 

Can I ever see all five planets at one time?

The short answer is very rarely but it’s fantastic when it happens! More often you’ll be able to see several at one time and that’s pretty cool. These events are called ‘planetary alignments’, and depending on which planets are involved, can last for many weeks, or even months. Occasionally you might see all five over the course of a night, but more often than not, at least one or two will be obscured by the glare of the Sun.

 

Where and when can I find the planets then?

That is the best question of all, and now that you know what the planets look like, you’re on the homestretch. Stay with me first for the ‘where’ part of the question!

The planets will always be found against the backdrop of one of the 13 constellations of the Zodiac (12 in astrology). You might be familiar with them – but just to be clear – we don’t teach astrology or horoscopes at Stardome. The science is simply this: due to Earth’s annual motion around it, the Sun appears to pass in front of these constellations during the course of a year. The line it traces is known as the ‘ecliptic’, and since the planets orbit the Sun on a more or less flat plane, they too will always be found against the backdrop of the Zodiac constellations.

From our southern hemisphere perspective, the ecliptic runs across our northern sky. On our winter nights it is high in the north and on summer nights somewhat lower. Near the horizon it can be east, west, or a little north or south of these points (depending upon the time of night and/or the time of year). This is all due to the Earth’s tilt. The ecliptic is where you’ll find the Zodiac constellations and all of the planets.

 

Why is Venus sometimes called the ‘evening’ or ‘morning’ star?

Having got the above information under your belt here is one more important thing to remember:

The planets that are further from the Sun (Mars, Jupiter, and Saturn – the outer planets) can be found anywhere along the ecliptic, but not so Venus, or for that matter, Mercury. These inner planets are closer to the Sun than Earth is. This means that they never appear fully on the night side of Earth because they simply don’t go there! Like the others, they will always be quite close to the ecliptic, but unlike them, they will never be seen far from the glare of the Sun. When they are seen, just before sunrise or just after sunset, they can be called the evening or morning stars (although they are not stars).

 

When can I see which planets?

It’s easy these days! 😊. You can download our latest monthly star charts with helpful sky guides here. You may wish to subscribe to our ‘Space News’ and read our Sky Spotter column here. There are many excellent app’s available, some are free, and will help to make your night sky searches very rewarding. Examples: Star Walk, Sky Safari, Stellarium.

 

Summary:

  • Five planets can be seen with the unaided eye.
  • Planets look different from stars and different from each other.
  • How close a planet is to the horizon affects how bright it appears. When high, there’s less air to look through – so the higher they are, the brighter they appear.
  • Mars’ brightness varies hugely over the course of a couple of years.
  • Mercury (the hardest to spot) and Venus (the easiest) are sometimes called the ‘evening’ or ‘morning’ star. Mercury comes and goes very quickly (just a few weeks) while the others hang around for many months.
  • The planets will always be found near the ecliptic against the backdrop of the Zodiac constellations – approximately east or west when rising or setting, or near north when they are highest in the sky.

 

STOP PRESS:

At the time of writing we’re fast running up to Matariki season. Matariki can be hard to spot at this time of year as it emerges from the east-northeast horizon just before sunrise. A cloudy horizon, trees, hills, or city lights don’t help either. Providentially, this year 2020, brilliant Venus will be the key – Matariki will be just to its left well into July. Also, the Moon will play a role early on June 19th and July 17th (see images).

Mars is stooging around in the early morning sky as I write but as spring approaches it will appear in the evening sky as well. Approaching mid-October 2020 it will reach opposition and will be brighter than Jupiter and won’t be this bright again until June 2033! Best viewing will be around midnight half-way up the northern sky.

The giant planets Jupiter and Saturn will be in our evening sky for the rest of 2020. Watch this pair as they slowly draw closer to one other. On 21st December they’ll give us a one in twenty year treat as they seemingly almost ‘touch’. Called a ‘great conjunction’ we might think of this as a modern rendition of the Christmas Star 😊.

From late June to late August all four of these planets will be on show simultaneously! However, to see them stretched out across the sky, you’ll need to rise early before the sky brightens. During a brief window from about July 15th to 31st 2020, faint Mercury will join the clan to make five! You’ll need sharp determined eyes to find it though. It will be close to the horizon below and to the right of Venus. Cross your fingers for a clear morning on July 19th, since on this morning the tiniest sliver of Moon will sit to Mercury’s left, making it easier to find.

Fast forwarding to Mercury’s next window, from about mid-September to mid-October, you’ll find it low in the west just after sunset. Lending a helping hand on September 19th 2020, a crescent Moon will sit just to Mercury’s right.

NOTE: The viewing times attached to our images are specific to Auckland. Times and directions will be slightly different for different locations.

John Rowe, Astronomy Educator