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The Planets

Planet Data For September

Click on any planet below to go straight to its section.

MercuryVenusMarsJupiterSaturnUranusNeptuneObs for All

The table below shows key data for the planets this month, including rise, transit and set times, as well as magnitude, apparent size and position data (right ascension and declination).

Events that occur when the sun is below the horizon are shown with a black background and white text. All other events happen when the sun is in the sky and other for not visible for observation.

July offers good views of all the planets except Mercury which spends most of the month too close to the sun for us to see it. Venus has arguably the worst views now that it is a distant, full disc only visible just before the sky brightens for sunrise.

Mars, Jupiter and Saturn are all morning planets and all heading towards oppositions later this year. Saturn gets there first, which is why we can see it before midnight by the end of the month. All three planets have growing and brightening discs this month.

Uranus and Neptune are also visible in the early morning sky, if you’ve never seen them before they are worth the hunt right now.

All of the images below can be opened full screen in a new tab by clicking on them


Mercury

05th September

2020 1 / We can maybe catch a glimpse of Mercury just before sunrise this morning. It is very low on the horizon half an hour before sunrise.

15th September

1940 0 / It’s one day before the small planet passes behind the sun. That’s why we can’t see the planet today.

25th September

0700 2 / Now an evening planet, Mercury is still too close to the sun to be observed. Here, it’s 2° over the horizon at 9pm.

There’s not much to see of Mercury this month.

It passes behind the sun in the middle of the month, after which it becomes an evening planet. The best (and only practical) time to see it is at the very start of the month before sunrise and at the end of the month after sunset. Even then, don’t expect great views.

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Venus

05th September

0610 4 / This view at 5:20am, which is 40 minutes before sunrise. The planet is 13° over the horizon, shining at magnitude -3.9.

15th September

0630 4 / At 5:30, venus is 14° over the horizon before sunrise. Its disc is 90% illuminated but only 11 arcseconds across.

25th September

0700 5 / At the same time later in the month we see the almost-full disc 12° high.

There is not much change to see in the sky for Venus this month. Viewing is okay but no better than that. Look for the brightly shining jewel before the sky gets too bright.

The disc continues to fill, increasing from 86% to 93% illuminated over July. Across the same period, the disc only shrinks marginally from 11.8 to 10.7 arcseconds across. There’s still some time before it passes behind the sun in October, so it’s disc will further shrink and fill over the coming weeks.

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Mars

05th September

0500 60 / At 5am, Mars is high over the eastern horizon, and larger than it’s been for many months.

15th September

0500 64 / At 5am, Mars is 40° above the horizon, midway between Aldebaran and Jupiter.

25th September

0500 67 / Still at 5am, the Martian disc at last extends beyond 8 arcseconds wide. It’s bright at magnitude 0.3.

It feels like we’ve been counting down to seeing ‘big’ Mars for a long time but we’re now down to about four months to go and the changes over the coming months are noticeable.

The disc of Mars grows by over one arcsecond in July, which doesn’t sound like much but is actually a 15% increase in size. With that comes increasing brightness.

What also happens as Mars moves towards its closest approach is that it rises earlier and earlier. By the end of July, Mars rises before 1am and it’s highest in the sky before 8am. In the next couple of months, we’ll be able to enjoy the Red Planet in the darkness of evening.

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Jupiter

05th September

2359 37 / Jupiter is high in the southeast at 5am, midway between horizon and overhead. It shines at magnitude -2.5.

15th September

2330 39 / Ten days later and Jupiter is a little brighter and placed between Mars and Saturn. Its disc is 42 arcseconds across.

25th September

2330 44 / At 5am now, Jupiter is 52° over the southern horizon, which is practically its highest point in the sky.

We’ve already seen that this giant planet passes within a degree of Venus at the beginning of May and Mars at the end of the month. Both of these events give us the chance to see how the giant compares to the two smaller, and much closer, planets.

It’s only two months until Jupiter’s opposition at the end of September and we see that in the planet’s growing size and brightness, and the fact that it’s rising earlier and earlier.

At the end of July, Jupiter is 44 arcseconds wide, shines at magnitude -2.7, and rises at 11pm. Its best viewing is still around 5am, but it won’t be many weeks before us evening astronomers can take a good long look at it.

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Saturn

05th September

2300 34 / 36° over the southern horizon is where we see Saturn at its highest at 4am.

15th September

2300 35 / There is just one month until conjunction and Saturn’s disc is 18 arcseconds wide and shines at magnitude 0.4.

25th September

2230 35 / At 3am, we see Jupiter in Capricorn 36° over the southern horizon.

It’s only one month until Saturn is as close to Earth as it comes this year. As we observed for Jupiter, the ringed planet is growing larger, brighter and is rising earlier.

In fact, by the end of July, we could comfortably be observing Saturn before midnight, when it will be 26° high above the southeast horizon.

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Uranus & Neptune

15th September – Uranus

0500 68 / Uranus is 30° high in the east at 4:30 in the morning. Use the line of Jupiter and Mars to help you find its small disc in Aries, near Cetus.

15th September – Neptune

2300 37 / At the same time, Neptune is about halfway between the southern horizon and the overhead point, 13° southwest of Jupiter.

Both of the two most distant planets offer good viewing this month, if you’re prepared to be outside in the early hours to see them.

Neptune is the better of the two because it’s higher in the sky, but both are worth hunting down when the moon is not in the sky.

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All Planets Viewer

Use the table below to see when each of the planets is observable for each day this month. Click on it for full screen.

A planet is classed as observable when it is more than 10° above the horizon and the sky is dark enough for it to be observed.

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Planet ephemeris tables produced with the kind permission of Dominic Ford. Sky images are courtesy of SkySafari Pro 6.

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