The Night Sky in May 2024
As the sky darkens Sirius appears midway down the western sky. It is the brightest star and twinkles with all colours when setting in the southwest around midnight. Sirius, 'the Dog Star', marks the head of Canis Major the big dog, now head down, tail up. Canopus, second brightest star, is southwest of overhead. At the beginning of the month Jupiter might be seen setting on the WNW horizon around 6:30 p.m. (Jupiter isn’t on the chart.) It soon disappears from the evening sky.
Below Sirius are bluish Rigel and reddish Betelgeuse, the brightest stars in Orion. Between them is a line of three stars, Orion's belt. To southern hemisphere star watchers, the line of three makes the bottom of 'The Pot', now tipped on its side.
Orange Arcturus is the brightest star in the northern sky, rising in the NE at dusk. It often twinkles red and green when low. It is 37 light years* away and about 120 times brighter than the sun.
Crux, the Southern Cross, is southeast of the zenith, to the right of 'The Pointers'. Alpha Centauri, the brighter Pointer, is the closest naked-eye star, 4.3 light years away. Beta Centauri, like most of the stars in Crux, is a blue-giant star hundreds of light years away. Canopus is also very luminous and distant: 13 000 times brighter than the sun and 300 light years away.
Following the Milky Way down into the southeast finds Scorpius. Orange Antares marks the Scorpion's body. The scorpion's upside-down tail curves to the right of Antares. Antares is a red-giant star like Betelgeuse: around 12 times the mass of the sun but wider than Earth's orbit. It is 600 light years away and 19 000 times brighter than the sun. There is a Greek legend that the Scorpion and Orion were always fighting so a goddess put them on opposite sides of the sky. That way they never appeared in the sky together. It doesn’t work for the southern hemisphere.
The Milky Way is brightest in the southeast toward Scorpius and Sagittarius. In a dark sky it can be traced up past the Pointers and Crux and fading toward Sirius. The Milky Way is our edgewise view of the galaxy, the pancake of billions of stars of which the sun is just one. The thick hub of the galaxy, 27 000 light years away, is in Sagittarius. The nearby outer edge is by Orion where the Milky Way is faintest. A scan along the Milky Way with binoculars shows many clusters of stars and some glowing gas clouds, particularly in Carina and Scorpius.
The Clouds of Magellan, LMC and SMC, are midway down the southern sky, easily seen by eye on a dark moonless night. They are small galaxies. The Large Magellanic Cloud is 160 000 light years away and the Small Cloud is around 200 000 light years away. They are much smaller than our Milky Way Galaxy but there are many billions of stars in each.
Saturn, Mars and Mercury are in the morning sky (so are not on the chart.). At dawn at the beginning of the month the three planets are equally spaced on a tilted line down the eastern sky. They are all the same brightness. Saturn has a cream tint, Mars is reddish, Mercury white. From places with a low eastern skyline, brilliant Venus might also be seen rising around 6:30 a.m. at the beginning of the month. It disappears in the twilight soon after. Saturn and Mars remain the same brightness but Mercury, at the bottom end of the line, gets brighter. This line-up continues till the end of the month. The Moon will be above Saturn on the 4th and again on the 31st. It will be above Mars on the 5th and between Mars and Mercury on the 6th.
Many meteors might be seen in the pre-dawn sky around May 7 as the Eta Aquarid meteor shower peaks. It runs from late April to late May. The meteors are dust from Halley’s comet, distributed around the comet’s orbit. As we pass close to the orbit, the dust is hitting Earth’s atmosphere at 66 kilometres per second. Friction with the thin air high up heats the dust so it glows. The meteors burn up far above the ground. The shower is named after the star it appears to radiate from.
*A light year (l.y.)is the distance that light travels in one year: nearly 10 million million km. Sunlight takes eight minutes to get here; moonlight about one second. Sunlight reaches Neptune, the outermost major planet, in four hours. It takes sunlight four years to reach the nearest star, Alpha Centauri.
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