Jupiter show starts in southeast sky

PUBLISHED : Monday, 01 July, 1996, 12:00am
UPDATED : Monday, 01 July, 1996, 12:00am

Jupiter, the largest planet in the solar system, will be directly opposite the sun on July 4. Astronomers call this planetary alignment an opposition, a term used when the Earth comes between any of the outer planets, Mars to Pluto, and the sun.

To see Jupiter, look towards the southeast two hours after sunset. Its milky white brilliance outshines all celestial objects save the moon.

Tonight, the two bodies will only be about five degrees - 10 lunar diameters - apart. The same will happen on the night of July 28.

This year Jupiter is in the constellation Sagittarius, the Archer. Most stargazers refer to Sagittarius as 'the teapot'.

It is an interesting constellation because it lies against the centre of the Milky Way galaxy.

Astronomers now know that the Milky Way is a vast star system, comprising over 100 billion stars including our sun, shaped like a spiralling disk with a diameter more than 100,000 light years across.

The centre of the disk forms a bulge with a high concentration of stars. Latest findings strongly suggest the centre of the Milky Way galaxy harbours a giant black hole.

The sun, together with its retinue of planets, is located about 30,000 light years from the centre and near the central plane of the disk. This 'insider' location gives us the impression of a faint luminous band of stars encircling us which we called the Milky Way.

The brightest part of it seen from Earth is its centre and had it not been for the intervening gas and dust, which block most of its light, the centre would have been much brighter.

Summer is the best time of the year to observe the Milky Way as it crosses the zenith soon after dark.

To get the best view of the Milky Way, choose a clear moonless night away from urban areas. Its centre will appear as a faint glowing patch west of Jupiter.

On July 6, Earth passes Aphelion, the point on its slightly elliptical orbit where it is furthest away from the sun and closest to the stars.

Full moon is tonight and last quarter on the 8th. New moon is on the 16th and first quarter on July 24. There will be another full moon on July 30, which may seem very large because its orbit brings it closest to Earth on that night.