No, the tail does not always trail the comet. To understand how this can be so, you must first understand what causes the tail of the comet. First, a comet is composed of two parts, the core and the tail. The core is a lump of frozen gas, pebbles, dust, and other interstellar stuff, sometimes described as a large, dirty snowball. This “snowball” travels around the Sun in an elliptical orbit.
That means that the comet travels in a long, narrow oval shaped orbit with the Sun close to one end of the oval. When the comet is far away from the Sun it travels relatively slowly and is extremely cold and frozen. As it continues in its orbit, it eventually returns close to the Sun at an extremely rapid rate of speed, swinging around the Sun and whipping back out to the distant regions of the Solar System again. Some Comets have orbital periods of hundreds, even thousands of years.
Comet Halley
As the comet approaches the Sun, it begins to warm up and give off gases and small particles that form the comet’s tail. These gases and small particles are slowly pushed away from the comet’s core by “solar wind” or the pressure of light shinning from the Sun. As the comet approaches the Sun, its tail will appear to stream behind the comet like a vapor trail of an airplane. On the other hand, as the comet recedes back out into deep space, the comet’s tail will appear to lead the comet, as the tail is pushed along by the sunlight.
In any case, the tail of a comet always streams away from the Sun, on the opposite side of the comet from the Sun. One last point I wish to make here. It is this debris trail left behind the comet’s passing that produces a meteor shower. What happens is, the Earth, moving in its orbit about the Sun, happens upon the comet debris trail and cuts through it. The debris left behind by the comet burns up in the Earth’s atmosphere, producing a meteor shower, as the Earth collides with it.
One of my favorite objects in the sky is the Summer Triangle. For me it symbolizes the coming of cooler weather and clearer skies and it has been slowly rising in the early evening skies over the past several months. Now is the prime time to enjoy this beautiful asterism made up of Deneb, in Cygnus, Altair, in Aquila, and Vega, in Lyra.
There are plenty of objects within it boundary, including the constellation Sagitta. Appropriately, Sagitta is Latin for “Arrow.” Even though this is the third smallest constellation (only Equuleus and Crux are smaller) it has been recognized since classical times.
One reason for it being so well recognized is because it can be seen from both hemispheres due to it proximity to the celestial equator.
Seemingly unusual for many constellations, this one looks just like what it is called, an arrow. During classical times it represented many arrows. It is the arrow that Hercules used to kill the eagle that Zeus sent to punish Prometheus, it is also the arrow shot by Heracles at the Stymphalian Birds, it is the one which Apollo used to slay the Cyclops, and it is said to represent Cupid’s arrow.
While, because of its size, there are not many deep sky objects within Sagitta’s boundary there is one beautiful globular cluster right in its center that can be seen with a pair of binoculars, M71. This globular cluster is about 13,000 light years distant, and is a little more than 7 minutes of arc in diameter (not quite as large or as bright as the famous Hercules cluster).
September 1, 1979: Pioneer 11 is first Earth based spacecraft to fly past Saturn.
September 3, 1976: The unmanned spacecraft, Viking 2, landed on Mars to take the first close-up color photos of that planet.
September 3, 2006: SMART-1 spacecraft was intentionally crashed into the Moon. It was a Swedish-designed European Space Agency satellite orbited around the Moon. It was launched on September 27, 2003 at 23:14 UTC from the Guiana Space Centre in Kourou, French Guiana. “SMART” stands for Small Missions for Advanced Research in Technology. On September 3, 2006 (05:42 UTC), SMART-1 was deliberately crashed into the Moon’s surface, ending its mission. Scientists hope that the impact would kick up enough fresh lunar “soil” that they may study its composition.
September 5, 1977: Voyager 1 was launched by NASA from Cape Canaveral aboard a Titan IIIE Centaur rocket. The Voyager 1 spacecraft is an 815-kilogram unmanned probe of the outer solar system and beyond and is currently operational. It is the farthest human-made object from Earth. The Voyager 1 spacecraft has moved into the solar system’s final frontier, a vast area where the Sun’s influence gives way to interstellar space. At 14 billion kilometers (95 astronomical units or 8.8 billion miles) from the Sun, signals from Voyager 1 take more than thirteen hours to reach its control center at the Jet Propulsion Laboratory near Pasadena, California. By the way, this was this probe that the movie, Star Trek: The Motion Picture, featured near its conclusion.
With the Moon waxing from First Quarter to Full on Friday, the stargazing will be poor, especially in the early evening. If you are an early riser, you will have pretty good skies to look at, provided the skies are not filled with big, thick, heavy rain clouds. The Stargaze Rating for the week is poor to fair.
The Moongaze Rating is good because this will be a good week to watch the terminator cross the western quadrant of the Moon, revealing wonderful lunar features.
For a great website to locate the planets, go to www.nightskyinfo.com. This site will tell you about the planets and give you a good star map to locate them (116).
Sunset Sky: (Sunset until 11 p.m.)
Just as the skies begin to get dark enough to see the brightest stars, we can already see Jupiter shining brightly high in the southeast. We are losing Saturn in the early sunset sky. Through a small telescope or pair of binoculars you can see the four Galilean moons and cloud belts which encircle the planet. This past weekend, we had a group of Civil Air Partol cadets at Richard B. Russell airport looking at Jupiter. Over the 2.5 hours of our observing session the cadets noticed that they could actually see that a couple of the moons had changed positions. The Galilean moons move fast enough to see a position change if you look over an hour or so.
Mercury and Saturn were too low to the western horizon to be seen. I doubt if you will be able to see them this week but if you have clear skies in the west and a good low horizon, you may yet get a glimpse of them.
Late Evening (11 p.m. until 4 a.m.):
Uranus and Neptune are both up this time of the evening. You will need a good star map and telescope to capture these gems.
Predawn Sky: (4 a.m. until sunrise)
Around 6:00 a.m. (your time), the sky is bracketed by Jupiter to the west and Venus to the east. Venus is very bright and unmistakable in its splendor. In between these two treasures you will find the Red Planet, Mars. Mars is not as bright as either of the two bookends but it is still a good sight, none the less. Since it is fairly far away from Earth right now, you will not be able to see much detail but it is still worth a look through a telescope. By January, it will be quite a bit closer and we will be able to see more features on its surface then.
Monday (31st), the Moon is at apogee its furthest distance from the Earth for the month (251,823 miles) at 7:02 a.m. EDT.
Wednesday (2nd), the Moon is 3 degrees north of Jupiter.
Thursday (3rd), the Moon is 3 degrees north of Neptune.
Friday (4th), The Moon will be Full at 12:03 p.m. EDT. This is the Full Sturgeon Moon – named after a large fish of the Great Lakes that are most readily caught during this month. Fishing tribes are credited for giving the name of this Moon. Additionally, a few tribes knew the August Full Moon as the Full Red Moon because of its reddish appearance through the sultry haze of summer. It is sometimes called the Green Corn Moon or Grain Moon as well.
Will Mars be so close to Earth that it will appear as large as a Full Moon on August 27th of this year? This is very interesting because since 2003, this has become a perpetual astronomy question that resurfaces each year in August. Somehow this rumor keeps popping up each year. The short answer is “NO!”
Now for the long answer. Most rumors have a kernel of truth in them. This is no different. The fact is, on August 27, 2003, Mars and Earth were as close to each other as they have been in several tens of thousands of years and closer than they will be again for another 60 thousand years. If you were around in 2003, you may remember that Mars was not the size of a Full Moon. You may say, well I don’t remember if it was or not. I submit to you that if it were the size of a Full Moon, you WOULD remember! I really have no clue as to how that part of the rumor developed. The diameter of Mars is actually two times the diameter of the Moon, so that can’t be it.
Ok, so how close is Mars now? Well, let me give you some comparisons. Currently, Mars is 157 million miles from Earth (1.696 AUs). On August 27, 2003, it was only 34.5 million miles from Earth (0.3727 AUs). This means that it is four-and-a-half times further from Earth now than it was back in August ’03.
It is interesting also to note that currently Earth and Mars are getting closer to each other. In five (5) months (January 27, 2010) Mars and Earth will be in another opposition. This means that Mars will pass between the Earth and Sun. This is when Mars and Earth are at their closest point in their orbits around the Sun. This year is not an especially close approach (0.664 AUs from Earth). This is roughly 61.6 million miles or 1.78 times further away from Earth than it was back on August 27, 2003. The opposition of Earth and Mars occurs every 26 months or so.
So now you know. When someone tells you about Mars, you can say: “Actually that is not true. The real story is..……”.
This is a beautiful open cluster which lies over 9,000 light-years from the Sun. It goes by names: the Owl Cluster, Kachina Doll Cluster, or the ET Cluster, due to its resemblance to the movie character.
To locate this cluster look 2° SSW of Cassiopeiae. It is fairly easy to spot because of its magnitude 6.2. It is also nicely positioned so you will not have to strain your neck to keep it in view.
When you see it, you will know why it is called the dragonfly cluster. The stars are very distinct and you will want to spend some time pouring over the stars within this open cluster. Take your time and enjoy this celestial treasure.
August 24, 1989: The Voyager 2 space probe flew by Neptune, sending back striking photographs from a distance of some 63,000 miles from the ringed planet.
August 25, 1981: Voyager 2 came within 63,000 miles of Saturn’s cloud cover, sending back photos and data.
August 27, 1962: The US launched the Mariner 2 space probe, which flew past Venus in the following December.
August 27, 1984: The Teacher in Space program was announced. A year and a half later, the Space Shuttle Challenger, carrying Teacher / Astronaut, Christa McAuliffe, launched on January 28, 1986 and went into the history books.
August 28, 1789: William Herschel discovered Enceladus, the sixth largest moon of Saturn. Enceladus, with a diameter of 310 miles, is about one tenth as large as the Earth’s moon. By Saturn’s standard it is a fairly large moon. The surface of Enceladus has some areas with craters and some areas that are smooth. It is thought that the smooth areas are fairly young resurfaced areas formed from cryovolcanic activity.
August 29, 1965: Gemini 5, carrying astronauts Gordon Cooper and Charles “Pete” Conrad splashed down in the Atlantic after eight days in space.
The Moon will be waxing from a shallow crescent at the first of the week to Gibbous by the end of the week. Because it will set early in the evening at the first of the week, the Stargaze Rating for the first couple days in the week are good. By mid week the moon will be very prominent in the sky, making it difficult to do much deep sky observing except in the early morning.
The Moongaze Rating is very good for the early evening and night as the terminator crosses from the eastern limb to the mid-western meridian.