Sunday September 30th the 20-day old waning gibbous Moon will be within 1-2o from the reddish star Aldebaran in the open star cluster the Hyades. The Hyades are a v-shaped group of stars making up the face of Taurus the Bull.
Aldebaran is at the tip of one of the
lines making up the v-shape and, with its reddish color, represents the ‘angry eye’ of the Bull.
Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.
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For the next several evenings Asteroid Vesta will be passing within 2-3o from the outer planet Saturn. Currently Vesta is only a couple of months past opposition, June 20th, and is still bright enough to be seen and followed as its position relative to Saturn slowly changes each evening. Saturn has an apparent magnitude of 0.47 while Asteroid Vesta has an apparent magnitude of 7.0.
With binoculars Vesta is visible under dark enough skies and with careful observation and a star map of that area the motion of Vesta may be followed. In that same general area, within the field of view of 10×50 binoculars, at least 3 Messier objects may also be seen. The Lagoon Nebula, M-8; The Trifid Nebula, M-20; and open star cluster, M-21.
This animated graphic shows a binocular view of Saturn and Vesta each day from September 25th to the 30th.
Tuesday September 25th the position of the planet Saturn with respect to the Earth and the Sun places this ringed planet at what is called eastern quadrature. Saturn is at a 90 degree angle from us as this graphic shows. Think first quarter Moon as that is a fair comparison of the relative positions. At this position Saturn follows the Sun across the sky from east to west as the Earth is rotating, meaning that Saturn rises after the Sun and sets after the Sun.
Where is Saturn now? Saturn is over the southern to southwestern horizon at sunset and is east (to the left) from the reddish star Antares in the constellation Scorpius the Scorpion. Further toward the west is the planet Jupiter, and to the east from Saturn is the planet Mars. And the 16-day old waning gibbous is above the eastern horizon.
Saturn currently has a 0.47 apparent magnitude and is centered on the Milky Way within about 2o from a few easy to see Messier Objects. These include M-21 a 7th magnitude open star cluster; 5th magnitude M-8, the Lagoon Nebula; and 5th magnitude M-20, the Trifid Nebula.
Learn a little (or a lot) more about Saturn by visiting the Cassini at Saturn mission web site. Click here to go to the Cassini Mission web site.
This is a short 5 minute video I made as part of a live musical performance called “Orbit” that I was part of in May 2011. This is a piece from the much longer tour of the solar system performance and video and shows Saturn and some of its moons as viewed from the Cassini spacecraft that month.
On Sunday September 23rd at 1:52 UT, (Saturday September 22nd 8:52 pm CDT ) the Sun will have reached the astronomical coordinates of 0 degrees declination and 12 hours of right ascension, or RA. This places the Sun within the boundaries of the constellation Virgo the Maiden, or as some would say, “the Sun is in Virgo.” This is the actual position of the Astronomical Sun as opposed to the pseudoscience of astrology which has the astrological Sun entering the constellation of Libra the Scales.
Read a little more about how astrology has the Sun incorrectly placed in a previous blog, and in another blog discussing the effects of precession.
Declination is the astronomical equivalent to latitude measuring from 0 degrees at the equator to 90 degrees at either pole. Right ascension, or RA, is like longitude except that there is only east RA. The globe is divided into 24 sections, and like meridians of longitude, these hour circles are 15 degrees wide at the celestial equator and taper to a ‘point’ at the north and south pole respectively. In RA the ‘hour’ circles are counted from 0 hours to 23 hours. The 0 hour circle is at the intersection of the ecliptic and the celestial equator in the constellation of Pisces the Fishes.
In a class lesson about seasons today would be one of the two days during the year when the Sun would be described as being over the Earth’s equator. If you were at the Earth’s equator the Sun would have an altitude of 90 degrees, or straight up in your sky at your local time for midday. At that moment there would not be a shadow. However at any other latitude, north or south at midday, the Sun would be at an angle less than 90 degrees and there would be a midday shadow. (Midday is the local time when the Sun is halfway between local rising time and local setting time. At any midday the Sun is at its maximum altitude above the southern horizon in the northern hemisphere, or is at its maximum altitude above the northern horizon in the southern hemisphere.)
What is often noted about an equinox day is the reminder that equinox means equal night as a reference to there being equal amounts of daylight, and night. Also on an equinox day the Sun would rise due east and set due west for virtually everywhere on the globe. The times for sunrise and sunset would be approximately 12 hours apart, and the rising time would be around 6 am local time, and the setting time would be around 6 pm local time.
This short video shows students at Colegio Menor San Francisco de Quito, a school in Quito Ecuador, measuring the altitude of the sun hourly on the day of the 2004 September Equinox. They were taking part in Project SunShIP, Sun Shadow Investigation Project. There are also some pictures showing a local midday shadow from other participating schools in the United States and U.K.
Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.
Friday September 21st the innermost planet Mercury reaches superior conjunction. At superior conjunction Mercury will be on the opposite side of the Sun. The graphic to the right shows the planet positions relative to the Earth and Sun for both inner planets and outer planets.
While at this superior conjunction Mercury will not be directly in line with the Earth and the Sun – on the ecliptic. Mercury has an orbital inclination of 7o with respect to the ecliptic. So like our Moon, Mercury during each complete orbit, will cross the plane of the ecliptic moving north (ascending node) and also moving south (descending node). For this superior conjunction Mercury will be a few degrees north of the ecliptic and will cross the ecliptic moving south, descending node, on September 23rd.
Thursday September 20th the waxing gibbous Moon will be crossing the plane of the ecliptic moving south. This is known as the descending node, one of two intersections the Moon’s orbital path (dark green line) has with the ecliptic.
Our Moon also reaches apogee, (greatest distance from Earth), on Thursday September 20th. At that time the Moon will more or less be at a distance of 31.74 Earth diameters (361,354 km or 224,535 miles) from the Earth.
On the evening of the apogee and node crossing the 11-day old waxing gibbous Moon will be over the southeast horizon at sunset in conjunction with the ‘Red Planet’, passing within 10-11o east from the planet Mars. Joining the Moon and Mars are the planets Saturn, Jupiter, and Venus – all to the west from the Moon and Mars.