Archive for August, 2009

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Mission 4: The Big Dipper

August 22, 2009

Mission Objectives: Constellation, Bright Stars, Multiple Stars

Equipment: Naked eye, Binoculars

Required Time: 3 minutes

Instructions: Get to a place with a clear northern horizon, look to the northwest, and find the Big Dipper. Seriously, it’s just that easy. Here, you can practice with this:

The view to the northwest right after sunset in the southern US, in Stellarium.

The view to the northwest right after sunset in the southern US, in Stellarium.

Note the little red W and N in the corners of the picture; at this time of year, the Dipper is exactly halfway between those cardinal points. If you can’t find it, make sure that it’s just after dark, see that your view isn’t blocked by clouds, trees, or mountains, and double check that you are, in fact, in the Northern Hemisphere.

The Big Dipper as a guidepost to the northern sky.

The Big Dipper as a guidepost to the northern sky.

If you can find the Dipper, you can find at least two more bright stars and have an edge on identifying their constellations. The path that is most widely known is that the two stars that make up the front end of the “pan” point unfailingly to Polaris, the North Star, around which everything else in the heavens appears to rotate. Also, you can follow the handle of the Dipper and arc to Arcturus, the brightest star in the constellation Bootes.

Like Lyra, Ursa Major has a double star treat for naked eyes and binoculars. The middle star in the handle is in fact two, Mizar and Alcor, the horse and rider. Your eyes don’t have to be particularly sharp to see that the brighter of the two, Mizar, has a dim companion. This is also a dead easy split with binoculars. A telescope working at even low magnifications of 40-50x will reveal that Mizar has another, even fainter companion, called Mizar B. Mizar was probably the first telescopic binary discovered, possibly as early as 1617, less than a decade after Galileo first aimed a telescope at the heavens. As if all of that weren’t enough, Mizar A and B are themselves both binary, although the components are too close to be separated by telescopes and can only be detected through spectroscopy.  So Mizar is a four-star system, another “double double”, all by itself.

The Big Dipper is just the rear end and oddly long tail of the constellation Ursa Major, the Great Bear. Polaris is at the end of the tail of Ursa Minor, the Little Bear. There are lots of stories about how these bears came to have such long tails–see what you can find. Because Ursa Major is so close to the celestial North Pole,  it is visible for most of the year and only dips below the horizon briefly at mid-northern latitudes. If you go far enough north, the Great Bear is visible all the time. The Greek word for bear is ‘arctos’. And so we call those far northern regions, under the eternal reign of the bear, the ‘arctic’.

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Mission 3: Waxing Lyrical

August 20, 2009

Mission Objectives: Constellation, Multiple stars

Equipment: Naked eye, Binoculars

Required Time: 3 minutes

Related Missions: Summer Triangle

Instructions: Ready for another constellation? This one is a piece of cake: nice and compact, all bright stars that show up easily even in the city, two simple shapes, high enough to be seen clearly throughout the Northern Hemisphere, and it even has a couple of nice Easter eggs for binoculars and small scopes. I’m talking about the constellation Lyra, the Lyre.

You remember how to find Vega, I’m sure (if you’ve forgotten, refresh your memory here). This time of year it is the brightest star overhead in the early evening; in fact, it is the fifth brightest star in the sky. It is so bright mainly because it is so close, only 25 light years away, not because it is big, although it is about twice the mass of the sun. Because it is heavier it is burning through its fusion fuel faster, and it will swell into a red giant in perhaps half a billion years. By comparison, the sun is only about halfway through its 10 billion year lifespan.

The constellation Lyra (red lines), and the Double Double (white arrow), from Stellarium.

The constellation Lyra (red lines), and the Double Double (white arrow), from Stellarium.

You already know that Vega is at the apex of the Summer Triangle. Even with the naked eye and under city lights, you should be able to see that Vega is also one point of a much smaller triangle, and that the smaller triangle has a parallelogram hanging off its southeast corner. That’s it, the constellation Lyra. If you can find the triangle and the parallelogram, you’re done.

But wait–there’s more! If you’re very sharp-eyed–or your corrective lens prescription is up-to-date–you may be able to see that the star at the “free” corner of the triangle is not one point of light, but two close together. This is Epsilon Lyrae, the famous “Double Double” star. It’s called the Double Double because both of the two stars that make up the naked-eye binary are themselves binary; so, two pairs of binary stars, circling each other. As if that wasn’t enough, spectrometry shows that the system includes a fifth star that is too dim for even telescopes to see.

If you can’t split Epsilon Lyrae into two components with the naked eye, grab your binoculars–any binoculars. Binoculars will show the wide separation between the two pairs, but to split the four visible stars requires a telescope with good optics. At 96x in my 90mm Maksutov-Cassegrain scope, the two pairs look like a couple of 8s, one standing up and one laying on its side. For a much better view, check out this photo of the four stars by acclaimed astrophotographer Damian Peach.

And as long as you’ve got your binoculars out, you might as well have a look at the third “star” in the triangle, Zeta Lyrae (the one star shared by the triangle and the parallelogram). This one is a simple double, not a Double Double, and the two component stars are much closer together than the double-eights of Epsilon Lyrae. Using my 10×50 binoculars and bracing my arms on the top of my car, I just make out that Zeta Lyrae is indeed two points of light, but I can’t hold the binoculars steady enough freehand. About time for a post on mounting binoculars, methinks.

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Success!

August 20, 2009

Mt Wilson 60 inch 800

Jupiter from Mt Wilson 800

Up far too late, but I couldn’t turn in without posting these. Full report to follow. I took both photos with my Nikon Coolpix 4500. That’s Io next to Jupiter, by the way.

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Observatory trip preview: A night on Mt. Wilson

August 19, 2009
View from the Mt Wilson towercam.

View from the Mt Wilson towercam.

One of the perks of living in California is being close to several nice observatories. When I lived in Merced I got to visit the Lick Observatory on Mt. Hamilton above San Jose. A few months ago I visited the Griffith Park Observatory in Los Angeles, which is just a fantastic and beautiful place to tour, not least because it’s free. But the gleam in my eye has been a visit to Mt. Wilson (image above from UCLA’s Towercam; go here for a regularly updated Towercam picture).

The Mt. Wilson Observatory was founded in 1904 by George Ellery Hale, and for almost half of the twentieth century it was home to the largest telescopes on Earth. The 60-inch telescope was the world’s biggest telescope when it saw first light in December, 1908. It held that title until November, 1917, when it was eclipsed by the 100-inch Hooker telescope, which is also at Mt. Wilson. No larger telescope would see first light until January, 1949, when the monster 200-inch (5 meter) Hale telescope started operations on Mt. Palomar.

The 60-inch telescope as it appeared when my grandfather was born.

The 60-inch telescope as it appeared when my grandfather was born.

The 60-inch telescope is no longer used for research. Instead, ordinary citizens can rent it for $900 a night and spend the evening observing the heavens with what is, as far as I know, the largest telescope in the world still used for visual observations (image above from here; image below from here). Usually an astronomy club will get a couple dozen people together and everyone will chip in to cut down on the cost of the trip. The Pomona Valley Amateur Astronomers are going tonight, and they had a few extra slots available, sooo…

The 60-inch telescope as it appears today.

The 60-inch telescope as it appears today.

…I’m going with them!

And I’m FREAKING OUT!! I have gotten to look through the 36-inch Great Lick Refractor on two occasions, and both times the views were absolutely unbelievable. The 60-inch reflector at Mt. Wilson has almost double the resolving power and almost three times the light gathering ability as the Great Lick Refractor, so I don’t even have a reference standard for how awesome this will hopefully be. The only dark cloud on the horizon would be, well, a dark cloud on the horizon–the PVAA group has already gotten clouded out once this year. But currently the skies and the forecast are both clear, so with any luck I will have the mother of all observing reports up in a day or two. Stay tuned!

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In the footsteps of Galileo redux

August 18, 2009

Galileo_moon_phases

Hoo boy. So all of three days ago I started this blog with a post entitled, “In the footsteps of  Galileo”, about Galileo’s  achievements, IYA 2009, and starting out in astronomy (image above from Wikipedia).

All of three minutes ago I discovered that the Astronomical League has an IYA 2009 project called, “In the footsteps of Galileo”, with instructions for replicating Galileo’s discoveries for those starting out in astronomy. It’s a cool project, and all it takes is a pair of binoculars and some patience (or fortitude; the Pleiades [#4 on the list] rise about midnight right now and aren’t what you’d call “well placed” until 2 or 3 AM).

The duplicated title is a coincidence–Google lists almost 3000 hits for the exact phrase “in the footsteps of Galileo”–but a fortunate one, because the “Footsteps of Galileo” project hits some of the best stuff I was planning on covering on this blog anyway. In particular, I’ve got some posts lined up on how to take the binoculars you probably already have and make the most of them for stargazing. Stay tuned for more–or, if you’re chomping at the bit, download the “Footsteps of Galileo” observing guide, dig the binoculars out of the closet, and get going (don’t forget Stellarium if you need a little help finding things).

If you’re  looking for something just a little more challenging, the Astronomical League’s Galileo Club includes 12 projects for small telescopes or serious binoculars. You probably will need something with higher magnification (15x-20x) than your average birding binos for those, but even a very small telescope should be adequate. Like, er, this one (shown below), which people have been having a lot of fun with despite, or perhaps because of, its $20 price tag.

Galileoscope-with-Box

Both AL projects are also listed on the right under Observing Lists. “In the Footsteps of Galileo” appears as “5 binocular targets for beginning stargazers”, and the Galileo Club appears as “12 objects for binoculars and small telescopes”.

Have fun!

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Mission 2: Eye of the Scorpion

August 18, 2009

Mission Objectives: Bright star, Constellation

Equipment: Naked eye

Required Time: 1 minute

Instructions: Go outside after dark and look south. Look for a distinctly reddish or orangey star above the southern horizon. To the right of it you will see three bright stars making a short vertical arc.

Antares in Stellarium, as it appears right after sunset in the southern part of the US.

Antares in Stellarium, as it appears right after sunset in the southern part of the US.

The red star is Antares, a red supergiant star about 600 light years away. It is an immense star, with a diameter about 800 times larger than that of the sun. If you placed Antares at the center of our solar system, it would swallow Mercury, Venus, Earth, and Mars.

Antares comparison

Antares compared to another large star, Arcturus, and the sun. R stands for 'radius'. Image from Wikipedia.

Antares is near the end of its life. Smaller stars, like our sun, eventually turn into red giants and blow off most of their mass to form planetary nebulae (so named because the near-spherical balls of gas look  like planets in telescopes, not because they actually have anything to with planets), each with a white dwarf at the core. No such “out with a whimper” fadeout for Antares–one of these days it will suffer a core collapse and blow itself apart as a Type II supernova. When this happens, the explosion will briefly outshine the entire Milky Way galaxy. Fortunately, “one of these days” could be thousands or even millions of years from now, so there’s no cause for panic.

We’re actually catching Antares pretty late in the season. The best time to see it is in late May and early June, when it is exactly opposite the sun in the sky. That means it rises at sunset, sets at dawn, and is highest in the sky in the middle of the night. I don’t know about you, but I’m not up very often at those wee hours. By August, Antares is high in the sky at sunset, or as high as it’s going to get.

Here’s the rub: Antares is pretty far south, so observers in the US and Europe need a clear southern horizon to see it. And the farther north you are, the worse your chances get. Here’s what Antares looks like just after sunset in southern England (higher and to the east you can see Altair, which I’m sure you remember from Mission 1).

Antares just after sunset from southern England.

Antares just after sunset from southern England.

Antares is also known as Alpha Scorpii, because it is the brightest star in the constellation Scorpio. The three bright stars to the right of Antares are supposed to be the scorpion’s claws, and the J-shaped hook of stars trailing off to the south and east form its body and tail, complete with a stinger on the end. To see the body and tail I have to take a short walk. From my tree-shrouded driveway all I can see are the claws and the giant red eye, as terrifying in life as it is in mythology.

The constellation Scorpio as it appears from the southern US.

The constellation Scorpio as it appears from the southern US.

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Hubble Ultra Deep Field in 3D

August 16, 2009

Over at Deep Astronomy, Tony Darnell makes a pretty good case that the Hubble Deep Field pictures are the most important images ever taken. To drive his point home, he put together a video about the Hubble Ultra Deep Field, how it was made, and what it means. At the tail end of the video the camera flies through the HUDF to show how the galaxies are distributed in three dimensions. The whole thing is only four minutes long, and I guarantee that it will be time well spent.

Hat tip to the blogs at HowStuffWorks.