Wednesday, August 31, 2016

The September Sky for September 1-13

The coming of September also signals the arrival of the Autumnal Equinox, which means that, by month's end, the night will once again be longer than the day. Also, with the equinox upon us, the most dramatic differences in solar movement (and thus length of day) will also occur, which means that, at least at the start of the night, the September sky is not all that different than it is in August.. During the course of the month, we will lose a lot of daylight. In all, the earlier nights combined with the lingering presence of the summer stars and summer heat makes for what is arguably the best time for astronomy in the entire year.

Cool Constellations
With the advent of September, the spring constellations are rapidly saying goodbye, with Virgo the next major constellation to disappear. Also getting low in the Southwest is Libra and Bootes and Corona are now just about due West at nightfall. In the North, the Big Dipper continues its dive, flattening out as it starts to approach the horizon. Perhaps the best part of the September sky is that one doesn't need to stay up late to see all the best sights of summer. At nightfall, Hercules is still near zenith, the Summer Triangle (Lyra, Cygnus, and Aquila along with hangers-on Saggita and Delphinus) is at zenith, Scorpius is due South with Ophiuchus and Sagittarius on either side, both still well-placed for observing. Also, the Milky Way is at its best positioning right after nightfall, too. For people who like to stay up late (or get up extremely early) a fall preview in the form of Pegasus, Pisces, Cetus, Andromeda, Aries, Capricorn, Aquarius, and even Perseus is on tap in the wee hours of the morning while, by month's end, the bright stars of winter in the form of Orion, Auriga, Taurus, and Gemini are visible, too.

Planetary Perceptions
With the arrival of September, changes are coming in the planetary world. First, Jupiter, which has been up seemingly forever, will disappear into the Sun's glare by mid month and will remain invisible for the remainder of September, reaching solar conjunction on the 26th. Moving slightly later Saturn and Mars will continue to separate this month after Saturn assumed the lead position last month. It should be noted that time to catch these outer planets under dark skies is limited thanks to the plane of the ecliptic, which is at its lowest position for prime time viewing all year. Staying with the evening theme, Venus will continue to hang extremely low in the Western sky all month. The real treat for September is in the morning as Mercury will be putting on quite a show in the morning come the end of the month. Look for it to emerge from the predawn glare around the 15th and it should be easy to spot by the 20th. On the morning of the 29th, there is a spectacular conjunction with the Old Moon, so circle your calendars for this one.

Tonight's Sky for September 1: New Moon
Today, the Moon, second brightest object in the sky, has reached the New Moon phase, which means that it is directly between the Sun and Earth, and thus invisible for us Earthlings as of now.

As for lunar mechanics, the Moon is always half lit. The reason we don't always see it as such is thanks to orientation in relation to us. Right now, with the Moon directly between the Earth and Sun, e can't see any of its lit side.

After today, we will see more of the Moon each night as its lit side turns more toward from us and heads toward first quarter.
Tonight's Sky for September 2: Young Moon Meets Jupiter, Venus
It may be two days since New Moon but the Moon is making its first appearance in the dusk sky tonight thanks to the flat ecliptic. However, the wait is worth the while as the thin crescent Moon will be parked very close to both Jupiter and Venus.

To see the show, head out after sunset and look extremely low in the West to spot the Moon. Luna found, look for two bright 'stars' nearby, which are actually Venus and Jupiter, Venus being the brighter and Jupiter the dimmer. Interestingly enough, these are the three brightest objects in the night sky-all within a few degrees of each other.

Tips: get optical aid in the form of binoculars. Yes, Venus and Jupiter are bright, but they're so close to the Sun that they may even be able to spot with the naked eye. Second, you'll need a good horizon with less than 5 (3 fingers held together at arm's length) degrees of obstruction, so scouting out a location in advance may be a good idea.
Tonight's Sky for September 3: Jupiter Sets 30 Minutes After the Sun
Anyone wanting to catch Jupiter had better hurry as the planetary king is setting just 30 minutes after the Sun as of this evening. To see Jupiter, grab a pair of binoculars and scan low in the Western sky.
Tonight's Sky for September 4: Saturn Sets 4 Hours After the Sun, Mars 1 Hour Later
It's not only Jupiter that's rapidly going away for the season, but Saturn, followed by Mars, are also rapidly approaching twilight's last rays, too. As of tonight, Saturn sets a 4 hours after the Sun with Mars following roughly 1 hour later. While 4 and hours don't seem all that urgent, they are this time of year as the ecliptic is at its lowest point for prime time viewing all year, which makes for some extremely low planets.
Tonight's Sky for September 5: Teapot Due South at Dark
You know it's late summer when the Teapot is due South at dusk. To see the cosmic kettle, go out as the sky is about half way to dark and look due South to find the relatively bright (2
nd magnitude for the most part) shape of stars resembling a teapot. Having trouble locating it? If you live under a relatively dark sky? You're in luck as you can find the Teapot by following the Milky Way down to the horizon as the galactic plane appears to be steam coming out of the spout.
Tonight's Sky for September 6: Apogee Moon
Tonight, the Moon is about as small as it will ever get thanks to the fact that the Moon is at apogee, a point in its orbit that is farthest from Earth.

What many people may not realize is the fact that the Moon (and all other celestial bodies) do not orbit their parent bodies in circles, but ellipses, which are slightly elongated circles. Result: any given day of an orbital period, any orbiting body will be at a slightly different distance from its parent body. As for the Moon, this variance in orbit amounts to about 20,000 miles.

As for tonight, the Moon will be about as far from Earth as it is going to get. When it comes to practical implications, the difference will be hard to notice with the naked eye to all but an experienced observer but, in a telescope, the difference will be obvious

Tonight's Sky for September 7-8: Moon, Saturn, Mars, and Antares
Tonight and tomorrow night, there will be a 4-body cosmic meet-up in the Southern sky as the Moon, Mars, Saturn, and Antares will all be in the same small area of sky both tonight and tomorrow. For tonight, the 3 solar system bodies will form a line going left to right of Mars, Saturn, and the Moon with Antares slightly below. Tomorrow, the Moon will shift East (left) and appear directly above Saturn, making for a vertical Moon, Saturn, Antares line with Mars off to the side.

As an interesting aside, 'Antares' means 'rival of Mars' and, with the two bodies so close together, it is easy to see why as both display a very obvious shade of red and, when they're near the same brightness (Mars varies in brightness as it travels around the Sun), it can be easy to see how they can be confused with each other. AS for now, Mars is about 1 magnitude (roughly 2.5 times) brighter than Antares.

Tonight's Sky for September 8: First Quarter Moon
Today, the Moon, second brightest object in the sky, has reached the First Quarter phase, which means that it is exactly 90 degrees around its orbit of Earth and is one quarter finished with its current orbit..

As for lunar mechanics, the Moon is always half lit. The reason we don't always see it as such is thanks to orientation in relation to us. Right now, with the Moon at a 90 degree angle relative to the Earth-Sun line, we only see half of the lit side.

After today, we will see more of the Moon each night as its lit side turns more toward from us and heads toward Full in a week.

Tonight's Sky for September 9: Viking 2 Launched (1975)
On this date in 1975, NASA launched the second of its Viking Mars probes. At the time, these were, by far, the most advanced planetary science missions ever attempted by the space agency. Consisting of an orbiter and a lander, the pair of Vikings revolutionized our ideas about Mars. When the first close-up images of Mars were captured in 1965, long-held hopes of an Earth-like planet were dashed when Mariner 4 returned two dozen images of a barren planet.

Fast forward a decade.

When the Vikings arrived at Mars, they revealed a world that was, to say the least, tantalizing. For starters, the landscape was surprisingly Earth-like as there were mountains, volcanoes, and, most importantly, river valleys and other features that were clearly created by long-gone water. Unfortunately, while providing more data about Mars than all previous missions combined, the landers' inability to find any organic compounds was regarded by the general public as a disappointment, so much so that NASA would not return to Mars for another 2 decades.

Tonight's Sky for September 10: Saturn Rises 1 Hour Before Mars
Remember how for all year Mars led Saturn through the night sky? Well, that changed last month when they switched positions and now, not even a month later, Saturn is rising 1 hour ahead of the Red Planet.
Tonight's Sky for September 11: Mars Global Surveyor Arrives at Mars (1997)
It was on this date in 1997 that the Mars Global Surveyor mission arrived at the Red Planet. Launched for Mars in On November 7, 1996, scientists had high hopes for this mission, especially thanks to its coming on the heels of the failed Mars Observer, which was lost in 1993. The goal: study Mars from the top of its barely-there atmosphere down to its surface and, for the first time, create a global map of the planet. Unlike Observer, Surveyor performed flawlessly, operating in Martian orbit for over 9 years. During that time, Surveyor mapped the planet, analyzed its atmospheric and surface composition, and scouted out possible landing areas for future surface missions among many other achievements.

Tonight's Sky for September 12: Venus Sets 1 Hour After the Sun
Tonight, Venus is setting an hour after the Sun, as hard as that is to believe. Why? The ecliptic plane is at a very low angle relative to t he horizon, which means that the planet is not very high. This is in contrast with Mercury, which is set to make an excellent appearance in the morning at month's end. The difference? When Mercury is up, the ecliptic will be almost perpendicular to the horizon, which makes for a much higher planet.
Tonight's Sky for September 13: Mercury at Inferior Conjunction
Want to see Mercury? Well, forget about it tonight as the speedy first planet from the Sun will be at inferior conjunction. What does that mean? In layman's terms, Mercury will be directly between the Earth and Sun in a Sun, Mercury, Earth alignment. End result: the little planet will be at its worst point for viewing. So, while this is more of a what not to see tonight event, mark this date on your calendar as we all will soon see how the planet again in the coming days (yes, days)!   

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