* Astronomy

Sagittarius and the Galactic Centre.
For northern observers, the Teapot of Sagittarius should be dashing across the southern horizon. Observe the lower western corner, which lies immediately above the stinger of Scorpio, the scorpion. You are now looking straight toward the heart of the galaxy, the galactic centre. The actual centre is not visible to us due to the unimaginable amount of dust and stars blocking the way, but we do know something about it thanks to both radio and infrared radiation that is not so easily blocked.

Summer triangle
The Summer Triangle is what is known in the trade as an "asterism", or a portion of a constellation. Asterisms are simply convenient grouping of stars which may lie within a single constellation or stretch across several, and frequently reflect local culture. For instance, what some people call the Big Dipper since it looks somewhat akin to a large spoon or water ladle, the Scottish refer to as The Plough.
The Summer Triangle is made up of the three stars Vega in Lyra, Altair located in Aquila, and Deneb which is found in Cygnus the Swan. Vega is the brightest of the three and at .04 magnitude, the fifth brightest star in the sky. As with all bright stars it has its share of myth and lore tightly bound to it.
The Greeks called it "Cithara," the Babylonians named it "Dilgan" and it was "Allore" to the Arabs. And it is toward this part of the sky that our solar system is rushing (the "Solar Apex"), at 12 miles-per-second. At this rate it will take us 450,000 years to reach the vicinity of Vega. But what a view we will have then! Vega, about 27 light years away, is 58 times the luminosity of the Sun and 3 1/2 times the diameter.
Over toward the east is Deneb, the tail of the swan. Deneb is one of the furthest of the bright stars, and one of the most luminous. Deneb is a "supergiant," and represents one of the greatest known. With a luminosity equal to 60,000 suns, it has an absolute magnitude of -7.1 and lies 1600 light years away.
Below Cygnus is Aquila the Eagle, home of Altair the 11th brightest star in the sky at magnitude 0.76. It is also one of the closest, nine times more luminous than the Sun and 1 1/2 times the size. Altair has one of the fastest rotations known, making a complete spin in only 6 1/2 days, compared to over 25 days for the Sun. Because of this it must be rather flattened, with an equatorial diameter nearly twice the polar diameter.

Epsilon Lyrae
The beautiful constellation of Lyra, the Lyre, contains one of the most acclaimed and spectacular multiple star systems. Known as Epsilon Lyrae this grouping is actually made of four stars sometimes called the "double double". The two brighter ones may be easily split in a pair of binoculars, and each of them have a dimmer companion that a small telescope should reveal.
The constellation also contains most enchanting of all deep-sky objects, the Ring Nebula. The Ring is what is called a "planetary nebula" formed largely from an expanding shell of material cast off by a star as it ages. M57 is one of the brightest and best of these. Unlike many deep-sky objects that often require just a bit of imagination to make out, this comes close to actually looking like the photographs. A stark, slightly elongated loop of material standing out against the darkness of the sky, the ninth magnitude ring is very easy to find, located right in between the two end stars of the constellation.
Located about 1400 light years distant the Ring is estimated to be about 1/2 light year in diameter, expanding at 12 miles per second. The central star that illuminates the material is a real challenge for amateur telescopes. Shining at a feeble 15th magnitude, it is well beyond the range of smaller instruments.

Whirlpool Galaxy, M51
M51 is better known as the "Whirlpool Galaxy" due to its pronounced spiral form, and is located right below the handle of the "Plough". This was the first ever to be seen as a spiral in the mid-19th century. While visible in the smallest instruments, its twisted nature will not show in anything less than an eight-inch telescope, while a 12-inch is recommended. Its galactic arms loop around the central core three times. With a luminosity of 10 billion suns and a diameter of 100,000 light years, M51 is roughly equivalent to M31, the great Andromeda galaxy and in turn, our own Milky Way.
The Whirlpool is about 35 million light years away and glows at a genial eighth magnitude. In the sky it is seen face on and is about 1/3rd of the visual width of the Moon. It should be visible as a dim fuzzy patch in a pair of binoculars in a very dark sky. If you are lucky in that regard, step outside and see what you can see tonight.

Shower	Activity Period	Maximum	Radiant		Velocity	ZHR
		Date	R.A.	Dec.	km/s
S. Delta-Aquariids	July 14-Aug 18	30th July	3.9h	-51.8d	14 km/s	11.2
Gamma Aquarids		2 August
Alpha Ursa Majorids		10 August
Northern Iota Aquariids		12 August
Kappa Cygnids		12 August	18.6h	46.2°	29.7km/s	5.8
Piscids		13 August
Perseids		13 August	3.2h	58.1°	59.3km/s	79.9
Alpha Capricornids		15 August	21.2h	-5.8°	17.5km/s	11.7
Cygnids		18 August
Ypsilon Pegasids		18 August	1.1h	53.4°	34.8km/s	4.7
Alpha Ursa Majorids		25 August	12.3h	65.8°	35.0km/s	3.7
Alpha Aurigids		26 August
	for UK (A.Smith)	Radio Meteor Observation Station Track

Britain is well placed to enjoy the best of this year's Perseids meteor shower, which peaks under moonless skies on the morning of 13 August. Of course, our weather will have the last word and we can only hope for an improvement after the recent dismal spell.
Elsewhere in our August skies, Venus and Saturn have disappeared at last into our evening twilight to leave Jupiter as our only prominent evening planet. It lies very low in the south-west at our map times as the Summer Triangle (Vega, Deneb and Altair) dominates our high southern sky and the "W" of Cassiopeia stands high in the north-east.
Mars is climbing and brightening during the morning hours while Mercury may be glimpsed before dawn during the coming week. Venus becomes a morning star at the month's end, when, on the 28th, there is also a total eclipse of the Moon.

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2007 08 03  5:00 UT    Mercury at greatest illuminated extent (morning)
2007 08 04  0:00 UT    Moon at perigee, 368,891 km
2007 08 13  5:00 UT    Meteor shower peak -- Perseids      
2007 08 13 18:00 UT    Neptune at opposition
2007 08 19  3:00 UT    Moon at apogee,  404,618 km
2007 08 28 10:00 UT    Total lunar eclipse -- totality lasts from 09:52 UT to 11:23 UT
2007 08 31  0:00 UT    Moon at perigee, 364,171 km