SJAA Ephemeris September 2004 | SJAA Home | Contents | Previous | Next

The Shallow Sky

Wake Up for the Morning Show

Akkana Peck

The image was taken with the Cassini spacecraft narrow angle camera on July 13, 2004, from a distance of 5.1 million kilometers (3.2 million miles) from Saturn, through a filter sensitive to wavelengths of infrared light centered at 889 nanometers. Courtesy NASA/JPL-Caltech.


It's not a great month for evening planet observers. There are outer planets to look at.

Uranus (in Aquarius), Neptune (in Capricornus), and Pluto (in Ophiuchus) are all well placed for observing in the evening sky. Uranus and Neptune were both at opposition last month, so their timing is virtually ideal for the evening observer, though unfortunately they never get very high in the sky (around forty degrees).

Jupiter and Mars are too close to the sun to observe this month. But the real show in September is in the mornings.

Mercury has its best morning apparition all year, rising as much as an hour and a half ahead of the sun. On the evening of Sep 9, Mercury has a very close encounter — about 3.5 arcseconds — with the bright star Regulus. Regulus is roughly a magnitude fainter than Mercury, and with Mercury at roughly half phase and seven arcseconds in size, you won't have any difficulty telling them apart!

While you're out there, don't miss gibbous Venus, which rises four hours before sunrise. It passes within two degrees of Saturn on the first of the month — should be a lovely low-power view, if you have an eyepiece which can show two degrees.

If Mercury, Venus, and Saturn aren't enough for you, and you're out under a dark sky before dawn begins, the latter half of September is a good chance to look for the Zodiacal Light (which you may remember from March's column). Look for a faint band of light stretching upward along the ecliptic from the unseen location of the sun. What you're seeing is reflections off the dust left over from the protoplanetary disk out of which the solar system formed.

While you're straining to see the dim pillar of light which marks the remains of the planetary disk from which we formed, take a moment to reflect on some of the science releases this year.

In May, JPL announced that the Spitzer Space telescope had detected organic materials in the dusty planet — forming discs of several stars in Taurus (high in the sky as you await sunrise). The targets of the Spitzer were all young stars, with chunkier planetary disks they're full of material which in our solar system has long since been swept up by planets. But they're quite a bit farther away, too — over 400 light years from us.

Earlier, in February, a team from Berkeley and the University of Hawaii unveiled a direct image of the planetary disk around the star AU Microscopium, a star only half the mass of the sun and 33 light years away. That observation was made with a 2.2 meter telescope on earth.

Take a look at our Zodiacal Light, and reflect on how modern telescopes are able to capture spectra and direct images of disks around other stars, and spy on their planetary formation.

That's pretty amazing!

The stories I reference are at and


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