Showing posts with label Lyra. Show all posts
Showing posts with label Lyra. Show all posts

Saturday, August 13, 2011

Lyre Solo (or Solo Lyre)

.....The constellation of Lyra is small, but it holds one corner of the Summer Triangle, and the fifth brightest star in the sky - the second brightest star in the northern sky.  Lyra contains the star Vega noteworthy because this constellation, unlike some others like Scorpius, is quite high in the sky in the northern hemisphere, passing directly overhead of the southern United States.  (Spookily, Vega passes almost directly overhead of Washington D.C..) 

.....While this is something that I have done for the last few constellations, I have a more well-defined standard format for how constellations are presented.  The first map shows the sky, centered on the constellation in question, with a radius of thirty degrees.  For all but the largest constellations (and Lyra is kind of small), this will show a number of bordering constellations.  This gives us a standard starting point, and helps us find the constellation in the sky.  (In the case of Lyra, this helps us find other constellations as Vega is pretty hard to miss.)


.....Zooming in on Lyra (this map has a radius of eight degrees, we see Lyra as it is usually portrayed, a triangle of stars sharing a corner with a parallelogram.
.....Looking up on a summer night, Lyra seems quite and serene.  Less than a dozen stars, one bright, but otherwise quite.  Actually, Lyra has some notable weirdness to its stars.  Vega is larger and more luminous than the Sun, but its brightness in the sky is due to its closeness.  Vega is only a little more than 25 light years away, so the light that you can see from Vega tonight left in late April of 1986.  Being close, Vega is relatively easy to study, and astronomers have fond a massive disk of gas and dust around Vega, with irregularities that might indicate the presence of planets.  Weirder than this is the other star only in the "triangle" of Lyra, designated Epsilon Lyrae.  Through binoculars (and on the second map), this star is revealed as a pair of stars close together in the sky.  This is no coincidence; those are actually orbiting a common center of mass - but it get stranger.  Looking through a telescope with high magnification on a clear, steady night, each of these stars is revealed as a double star in their own right, so this is also called the Double-Double, four stars orbiting in pairs that orbit each other.

.....Even weirder is Sheliak, or Beta Lyrae.  Sheliak is 882 light years away, so for the light reaching us (from 1129, the year of the Council of Troyes franchising the Knights Templar - let's see what Dan Brown does with that) to still make Sheliak the second brightest star in constellation must be something outstanding indeed!  Sheliak is also a double star; nothing strange in this, most stars orbit in pairs (or more).  In Beta Lyrae's case, the two stars are so close together that the gravity of each star distorts the other, and material is pulled off of one towards the other.  These stars are orbiting so quickly that as the stream of gas moves toward the hotter star, it misses the star, building up into a disk.  Even this disk overflows, with material escaping into space from the poles, and leaking out from the opposite side of the accretion disk

.....Because Lyra is a fairly tiny constellation, I have included two telescope objects on this map as well.  This kind of skips ahead in my plans, since I intend to discuss these objects on my next tour of the constellations, but if you have even the smallest of telescopes, the object M57, aka the Ring Nebula, is straightforward to find between Sulafat and Sheliak.  (When I was in seventh and eighth grade, my backyard telescope had a lens actually slightly smaller than the human eye, and a tripod with legs six inches long that I would need to balance on the posts of a chain-link fence.  I could find Jupiter, Saturn, the Orion Nebula, the Andromeda Galaxy ... and the Ring.  The other deep-sky object is M56, a globular cluster that is one of literally dozens of globular clusters that can be seen in the summer sky.

.....As a last point, I have previously discussed how the north star can be hard to find because the constellation it is in is so faint.  Also, there are a number of people who (if pressed) will claim that the North Star is the brightest star in the sky.  (There is at least one who simply tongue-in-cheek defines the North Star this way be fiat.  Her car has GPS, so navigating by the stars is not a daily requirement.)  The North Star is not the brightest, but due to the Earth's long, slow 26,000 year wobble on its axis, if you wait about twelve thousand years, you (or your head in a jar) can see Vega as the star closest to the pole.

Tuesday, August 24, 2010

Lyre, Lyre

.....Lyra the lyre is the first of the constellations of the Summer Triangle; a small constellation consisting of a triangle of stars joined to a parallelogram, but easy to find because it contains one of the brightest stars in the sky. The westernmost star in the Summer Triangle is Vega, and when you can see it over the horizon it the fifth brightest star in the sky. (If someone is reading this over your shoulder, they probably made some joke like, "except for the Sun, dude." I'll wait for a second if you choose to slap them.)

(All good? Yeah, I feel better, too.)

.....Vega is actually one of the stars we use to define the "magnitude" scale that defines the brightness of stars. Originally, this system goes back to the Greek astronomer Hipparchus, who defined the brightest stars as "stars of the first rank" and the dimmest stars as "stars of the sixth rank". Now that we can use cameras to measure exactly how much light we receive from a star, it is now possible to be a little bit more precise. Vega and Arcturus (in Boötes) were use to define zero magnitude. In this reconstructed system, stars with a magnitude of 1.00 are bright, stars with a magnitude of 6.00 are just barely visible one a clear, dry, dark night, and the Sun has a visual magnitude of -27.
.....The only stars brighter than Vega are Arcturus (just barely), Sirius (a winter star), and Canopus and Rigil Kentaurus (stars not visible from the middle and upper United States).

.....The second brightest star in Lyra, Sheliak, is special in another way. Like most stars, it does not travel through space on its own, but Sheliak is actually two stars orbiting closely to each other. As I said, most stars travel in pairs (or more), but these two stars are orbiting so closely to each other that the shape of both stars is distorted, and material is apparently escaping out of the "back end" of Sheliak A. Incredibly funky physics, but you can't see anything through a telescope.

.....What you *can* see in a telescope is Epsilon Lyrae, the other star in the triangle at the top of Lyra. This might look a little funny in the star map, and this star in even a good pair of binoculars will be revealed as a pair of stars. If you then look at Epsilon Lyrae in a telescope under high power, each of these stars is revealed as another pair of stars; Epsilon Lyrae is known as the "double-double" star, four stars (two pair) appearing as one.

.....Numerous times in the past, I have shaken loose from the constellations of the past merely held on to because, ooh, the ancient Greeks created all of western civilization, big whoop, so as I proposed in my last post, I'm replacing the lyre with the lyrebird. After all, how many of us own harps in this day an age? I myself only have one CD of harp music. Hey, it was at a concert; support artists, art establishes and maintains the common culture! You like culture, right? (If you are next to someone who answered no, remember, engineers are often helpful to society as well.)

NEXT: Telescopic objects in Lyra

Thursday, August 19, 2010

The Birds of Summer

.....One of the problems that can keep people from moving from a peaceful contemplation of a dazzling array of stars to finding the dazzling variety of clusters, nebulae, and galaxies that are surprisingly accessible once you make the shift from seeing the sky as a featureless expanse of stars to recognize patterns that will allow you to find wonders hiding in plain -er- slightly assisted sight.

.....Starting in the summer (but lasting until November), three of the brightest stars in the northern sky form a (duh) triangle that covers much of the sky. This "triangle" that first appears in the "summer" sky is called the Summer Triangle because at some point, astronomers got tired of doing things like grabbing a rough pentagon of fourth magnitude stars and calling it "the giraffe"
.....The three bright stars are in three different constellations because the Summer Triangle really does cover a large selection of the sky, and ancient astronomers invented constellations to be able to break the sky into manageable pieces, so they weren't going to invent constellations that tokk up most of the sky. Well, not more than once, anyways. The three bright stars are Altair, Vega, and Deneb, in the constellations of Aquila, Lyra, and Cygnus (the next three constellations I'll write about), and you can use these to do a bit of traveling into the past. Altair, the southernmost star in the triangle, is about 16.8 light years away. This means that it has taken the light from Altair more than sixteen years of traveling through space. The light that reaches us on Friday left Altair about November 12th, 1993.

.....In the northwest, the brilliant star Vega appears to be a step brighter than Altair, but it is actually giving off more than four and a half times as much light into space than Altair does, but Altair is closer. Vega is 25.3 light years away, which mean that Friday's light from Vega left about May 2nd, 1985.

.....The third star, Deneb, is the faintest of the three as seen from Earth, but it actually gives off more than 60,000 times as much light as the Sun does. If we wanted to move Earth to Deneb and get as much light as we do now, we would have to move the Earth to be seventeen times as far away from Deneb as Pluto is from the Sun. Deneb is more than three thousand light years from our solar system, meaning that the light we see now has been traveling through space since 1218 BC, when Ramses II (the Great) was Pharoah of Egypt, and the Trojan War was going on*.

.....These three constellations will be the next three that I write about, Cygnus the swan, Aquila the Eagle, and Lyra the Lyre ... y'know, since two of these three are birds, and since I have felt no compunction about changing constellations, let go ahead and change Lyra to the Australian Lyre-bird, and have these three as as the birds of the Summer Triangle. There are a couple of small constellations that will also show up: Sagitta the arrow, located inside the Summer Triangle, and Scutum, the shield, which I will discuss along with Aquila the eagle, because Aquila has no Messier objects of its own.


* or at least this falls into the range of time in which the original Trojan War took place.