Skywatch: October 2012

The brightest star in Scorpius, known as Antares – the reddish-orange star in the lower left of the picture.

The planet show includes just a few of them in October with the two best, Jupiter and Venus, being seen late at night or early in the morning before sunrise, in the eastern sky. A third planet, Mars, puts on a nice show on the night of October 19th. Mars appears then just a few degrees above the brightest star in Scorpius, known as Antares. Antares is a reddish-orange star and Mars is a reddish-orange planet, and they will have almost the same level of magnitude (brightness; at +1.2). They will appear very similar. But to see them, we will need to look low in the southwestern sky right after it gets dark and for about an hour afterwards, because Scorpius is now very low and both Mars and Antares will set only a little while after twilight has ended completely.

Venus, on the other hand, is easy. It rises around 3:30 am in the East and will be visible even after the Sun comes up if one watches it as darkness fades and dawn approaches and marks its position. >From October 1 to October 3rd, Venus, among the stars of Leo, will appear close to Regulus, the brightest star in Leo (though Venus will be 100 times brighter than Regulus). On October 1st the two will be only two degrees apart. This gap narrows even more over the next two mornings, going down to less than a Moon’s width apart on October 3rd. Venus will remain visible all through October, but it will be rising later (around 4:30 am) by the end of the month as its orbit takes it closer to the Sun and farther from Earth.

Jupiter shines brightly at –2.6 magnitude between the horn stars of Taurus the Bull, rising in the East at 10 pm at the beginning of October and by 8 pm at the end of the month. The waning gibbous Moon will be seen just below Jupiter on the night of October 5/6, and again close to Jupiter on October 31st to help light the way for the Halloween trick or treaters. That evening the Moon and Jupiter will rise together between 7 and 8 pm.

Several bright first magnitude stars grace October evenings, but most are not part of true fall constellations. Deneb in Cygnus the swan, Vega in Lyra the harp, and Altair in Aquila the eagle form the well-known asterism called the Summer Triangle, which is now seen high in the western sky. Over in the northeast, just above the horizon, bright Capella starts to show up. But Capella is part of the oddly named winter constellation, Auriga, the goat herder.

The only true fall 1st magnitude star is in a dim constellation called Pisces Austrinus, the southern fish. This should not be confused with the zodiac sign constellation Pisces (the fish), which appears in the fall sky but well above Pisces Austrinus. Indeed, only half of this constellation appears above our horizon. One needs to go much farther south to see all of it.

But Fomalhaut is up at the top and can be seen in the south to southeast sky, very near the horizon throughout October. Fomalhaut is an Arabic name as are many “common” star names. Arabic traders used the stars to navigate at night as they traveled from Europe to Africa and Asia, often in desert lands, using the night as a cooler time to travel. Their legacy is carried on today in many star names.

Fomalhaut is a a hot white star some 23 light years from Earth, and when seen it often twinkles a lot because we are seeing it close to the horizon and the thicker air nearer Earth’s surface makes the light wiggle.

Moon phases this month include: Last quarter on October 8th; New Moon October 15th; First Quarter October 21st, and Full Moon October 28th.