SCI - Night sky for April

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ET ISSUE 2137 Sunday 1 April 2001

The night sky for April By Adrian Berry

The night sky for April

THE chart shows the sky at midnight on April 1. The positions of the stars on other nights can be found from previous charts (our last appeared on March 1), for they rise two hours earlier each month. Thus, the appearance of the sky at 10 pm at the beginning of April (except for the Moon and planets) is identical to that a month ago at midnight. The Moon, which is full on the 8th and new on the 23rd, is shown in its various phases. The hazy area represents the billions of stars of the Milky Way. Constellations are in capitals, and the brighter stars are in italics. The larger the circle denoting them, the brighter the star.

A HUGE campaign is at present underway to send a spacecraft to Pluto, the Sun's most distant planet. Astronomers passionately want such a mission, to be launched in 2004, arriving by 2012, but the US Government opposes it on grounds of cost.

It is a case of now or never. With any other planet or moon, postponing the mission would not greatly matter. But Pluto won't wait. Heading away from the Sun on its eccentric orbit, its surface temperature is getting steadily colder, and may already be down to minus 380°F.

Within a few years, its atmosphere of methane, nitrogen, carbon monoxide and water will freeze and collapse, its ice becoming as hard as concrete, so that a spacecraft wouldn't find much worth looking at. Pluto, the only planet in the solar system not yet visited by a spacecraft, won't approach the Sun again and warm up for another 200 years. Hence the urgency.

Details of this hoped-for mission can be found on www.plutomission.com, where people are asked to vote on a petition and comment. "Please go to Meiosei!!!" wrote a resident of Osaka, using the Japanese word for Pluto. "Don't break our kids' dream."

Winter stars are now vanishing with the appearance of spring constellations. Chief among them is Leo, the Lion, one of the finest of zodiacal constellations. Its brightest star is Regulus, a pure white star (which is quite rare in the cosmos), 85 light-years from Earth and 130 times brighter than the Sun - if the two were seen from the same distance.

Just to the north of Regulus is Gamma Leonis (Algieba), a fine double star system which should be easily resolvable through a small telescope since its two stars are so far apart. At the far eastern extent of Leo is Denebola, or Beta Leonis, a star much used by astronauts as a navigational marker, and which was reported in ancient times to be even brighter than it is today.

High overhead, to the north of Leo, are the familiar seven stars of the Plough, the brightest part of the huge constellation of Ursa Major, the Great Bear. The Plough is famous in history, since before the invention of clocks its position made an excellent method of telling the time.

Follow the line of the Plough to the south-east to find the brilliant orange star Arcturus in Boîtes, the Bear-Driver, the fourth brightest star in the sky and an important herald of spring. Arcturus is one of the few stars to be mentioned in the Bible. "Canst thou guide Arcturus with his sons?" ---Job 38, 32, although it is unclear which stars are meant by his "sons."

And to the west of Boîtes is Coma Berenices, or Berenice's Hair, named after an Egyptian queen who sacrificed her hair to the gods. This constellation is crowded with galaxies that a small telescope should distinguish. Of the planets, Mars rises at midnight in Ophiuchus, and is bright in the early morning sky---as is Venus.

Jupiter and Saturn, riding together, are better seen at the beginning of the month than the end. There is a good chance to see Mercury on the 8th, when it is nine degrees north of Venus. Uranus and Neptune are low in the morning sky and hard to see.

-- Anonymous, March 31, 2001


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