What’s up? Night sky for April 2012

Star trails over an observatory

The southern sky is full of wonderful treats for the stargazer. (This star trail photo by Iztok Boncina was made by keeping the camera shutter open.)

Except where indicated, all of the phenomena described here can be seen with the unaided eye. And unless otherwise specified, dates and times are for the Australian Eastern Standard Time zone, and sky directions are from the point of view of an observer in the Southern Hemisphere. (If you’re in the Northern Hemisphere, please see the video at the bottom of the page for What’s Up in your night sky.)

April 3

The Moon, now just over three-quarters full, will be about 11 Moon widths above and to the left of the bright blue star, Regulus, the brightest star of the constellation Leo. A little further below is what looks like a red star, but is actually the planet Mars. The colours of Regulus and Mars make a nice contrast. About 77.5 light years from Earth, Regulus is not one star but four, grouped into two pairs. Multiple star systems are very common throughout the Milky Way galaxy.

April 4

The Moon is still in the vicinity of Mars tonight, being above and to the right of the planet. Incidentally, when I use a term such as “vicinity”, it is not to be taken as suggesting the two bodies are physically near each other out there in space. Rather, they are simply within similar lines-of-sight from our vantage point on Earth.

April 4 sky view

April 4, 8:00pm. The Moon, Mars and the star Regulus will make an attractive triangle in the northern part of the sky. Note the colour difference between blue Regulus and ruddy Mars.

April 7

Full Moon occurs today at 5:19am Sydney time (19:19 Universal Time on April 6). In a similar fashion to its “encounters” with Regulus and Mars a few days earlier, tonight the Moon will be about six Moon widths to the right of another bright star, Spica, and about 10 Moon widths above the planet Saturn. Spica is the brightest star of the constellation Virgo; it is a blue giant star about 260 light years from Earth. This is a great time to see Saturn (see April 16), so it’s a good idea to use the nearby Moon to identify it.

April 8

Today the Moon will be at the closest point in its orbit, called perigee. The distance between the two bodies today will be 358,311 kilometres.

April 10

This evening, take a look about 12 Moon widths below the Moon and you’ll see a reddish looking star that looks a bit like Mars. It’s the star Antares, and its name actually “rival of Mars”. Antares is the brightest star of the constellation Scorpius, and is a red supergiant star about 883 times bigger than our Sun!


Saturn, as it appears through a backyard telescope. Image by Steve Massey.

April 13

It is Last Quarter Moon tonight at 8:50pm Sydney time (10:10 Universal Time).

April 16

Today the planet Saturn reaches what astronomers call “opposition”. This means that, from an Earthly perspective, it is the opposite direction to the Sun—so if you could look down on the Solar System from above you’d see the Sun, Earth and Saturn (in that order) in a straight line … although Saturn, of course, is much further from us than the Sun. The period around opposition is a considered a great time to view a planet, as it rises in the east around the same time as the Sun sets in the west, and is therefore nice and high in the sky by late evening.

April 19

If you’re an early riser, out to east this morning before sunrise you’ll see the very thin crescent Moon. Above and to its right is a bright looking star. Well that’s not a star; it’s the planet Mercury, the closest planet to the Sun.

April 19 sky view

April 19, 6:30am. The thin crescent Moon and the planet Mercury will be visible together in the eastern sky before sunrise.

April 21

New Moon occurs today at 5:18pm Sydney time (07:18 Universal Time).

April 23

Today the Moon will again reach the farthest point in its orbit, apogee, at a distance from Earth of 406,421 kilometres.

April 24

Today the Moon makes another apparent close approach to a star, this time Aldebaran, the brightest star of the constellation Taurus. The pair will be low in the western sky after sunset. Like Antares, Aldebaran too is a red star, but not a supergiant—it is only about 44 times the size of our Sun. It’s about 65 light years from Earth.

April 25

There’ll be a lovely astronomical pairing in this evening’s sky, with the Moon very close to Venus. The Moon is the second-brightest object in our night sky, and Venus is the third-brightest.

April 25 sky view

April 25, about 7:15pm. The thin crescent Moon and Venus will be close together in the western sky.

April 29

It is First Quarter Moon today at 7:58pm Sydney time (09:58 Universal Time). First Quarter is a good time to look at the Moon through a telescope, as the sunlight angle means the craters and mountains are throwing nice shadows, making it easier to get that 3D effect.

There’s more great night sky viewing information at Melbourne Planetarium’s Skynotes site.

If you’re in the Northern Hemisphere, here’s a Jet Propulsion Laboratory video that details what you can see this month:

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 and Iztok Boncina / ESO.

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  1. Mrs H says:

    Very interesting stuff Mr J. Posted photos of my visit to Tidbinbilla on my Facebook page with a link to http://www.spaceinfo.com.au. Granddaughter No.1 studying at the Conservatorium of music is composing a piece of music based on the sounds of space. Apparently NASA have put them on their website?

  2. Jonathan Nally says:

    It’s a great sight, isn’t it? I’ll always have a fond spot for Mars, as it was the first planet I identified when I was a kid.

  3. Anne says:

    Hi Jonathan, just been outside with my trusty binocs, and yes indeed, there is Regulus and Mars and a very bright Moon. Read the news today about Tidbinbilla broadcasting the landing of the Mars vehicle in August to the world. Fantastic.