Look up

Follow the Moon to the stars and Jupiter

Moonshine at Flinders, Victoria. Alex Cherney, CC BY-NC-ND

The ABC is encouraging us all to get out and observe the sky with their exciting Stargazing Live series to air April 4-6 with Professor Brian Cox and involving many astronomers across Australia. Here’s some tips from our own stargazer who will be taking part in the ABC Stargazing Live event at Melbourne’s Federation Square, April 6.

Look to the skies this April and by following the Moon we can catch sight of a number of interesting stars and planets. In particular, its a great time to see the planet Jupiter which reaches opposition on April 8.

If you have never explored the sky before, following the Moon is a perfect way to begin. Or perhaps you are already an accomplished stargazer, if so the Moon can be a great reminder to keep looking up.

The Moon passed its New Moon phase back on March 28, which is when the Moon and Sun come together in the daytime sky.

Now, the Moon is drifting away from the Sun and beginning its own journey across the early evening sky. Here’s how we can use it as an easy guide to the stars above.

Close but not too close

Let’s begin on Saturday April 1, when the Moon will appear just below the red giant star Aldebaran, a star that is older than our Sun and has already begun to enter old age.

The thin crescent Moon sits right between the eyes of Taurus the bull, with Aldebaran being the bull’s fiery red eye.

After sunset, the thin crescent Moon appears in the constellation of Taurus. Museums Victoria/stellarium

From Australia, we’ll see the Moon and Aldebaran quite close to each other, but across Asia people will see the Moon occult Aldebaran. The star will disappear behind the Moon for about an hour or so before reappearing.

The National Astronomical Observatory of Japan (NAOJ) provides details of what will be seen from several Japanese cities, but the event will also be visible from China, India and other Asian countries.

It’s interesting to note, that we will never see an occultation of Aldebaran from Australia. The star is too far south of the ecliptic (the path the Sun appears to follow across the sky) for the Moon and Aldebaran to ever cross paths from our point of view.

The next phase

By Tuesday April 4, the Moon will have grown to its First Quarter Phase, with ‘first quarter’ referring to the Moon being a quarter of the way around its orbit of the Earth. During this phase the Moon straddles day and night - rising at midday and setting at midnight.

Below the First Quarter Moon are a pair of bright stars. To the ancient Greeks, these are Castor and Pollux, the twin stars of Gemini.

Below the First Quarter Moon are Yurree and Wanjel as seen by the Boorong people. Museums Victoria/stellarium

But from Australia, the Boorong clan of Lake Tyrell in north-west Victoria saw these stars as a pair of hunters - Yurree is a fan-tailed cuckoo and Wanjel the long-necked tortoise and together they are chasing Purra, the kangaroo. Although at this time of year Purra (denoted by the star Capella) has got away and has already set in the north-west.

Rise of the king

The fat gibbous Moon can be found to the right of Regulus on Friday April 7. Regulus is the little king star of Leo, the lion, another zodiac constellation. However, unlike Aldebaran, Regulus aligns almost perfectly with the ecliptic, so it is possible for both hemispheres to see the Moon occult Regulus.

The Moon passes by Regulus on the evening of April 7, while Jupiter is seen rising in the east. Museums Victoria/stellarium

There was a lunar occultation of Regulus back in February. Most people across Australia were clouded out that night, but amateur astronomer Ian Musgrave managed to snap some great shots of the event despite the poor weather.

There will be another chance to see Regulus disappear behind the Moon from Australia on May 4.

Planet in the east

There is one bright planet in the evening sky this month and it is striking. Look towards the east after sunset and you can’t miss Jupiter. It reaches opposition on the morning of April 8, which means it lies in the opposite part of the sky to the Sun.

This also brings Jupiter closest to us, so now is a great time to see the planet at its best.

NASA’s Juno spacecraft is doing some close-up exploring of Jupiter and delivering superb images and a wealth of data. The spacecraft recently completed its fifth fly-by of the planet, when it dived to just 4,400 km above the cloud tops.

The swirling storms of Jupiter, both bright (to the left) and dark (to the right), captured by Juno. NASA/JPL-Caltech/SwRI/MSSS/Roman Tkachenko

A problem with the spacecraft’s fuel system has meant that it remains in a 53-day orbit of Jupiter, rather than dropping to a 14-day orbit as originally planned. The same great science will be done, just at a slower pace.

Here on Earth, we’ll see the Moon partner with Jupiter on the night of April 10 and again the following night, April 11. The Moon will fall into line with Jupiter and the star Spica, the brightest in the constellation of Virgo, on April 10.

The following evening, the Full Moon will be below Jupiter and Spica and the trio will form a little triangle in the east after sunset.

The Full Moon passes by Jupiter and the bright star Spica on the nights of April 10 and April 11. Museums Victoria/stellariums

We have now followed the Moon on half its journey around the Earth, from New Moon to Full Moon, and seen it drift from the daytime to the nighttime sky. Keen Moon watchers can keep following the Moon into the pre-dawn sky, where it will pass Saturn during the early hours of April 17 and Venus on April 24, just before sunrise.

Often in astronomy we rue the Moon for its bright light but the Moon can have its purpose too by encouraging all us stargazers to look up and explore.

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