Headlong into the celestial abyss
While we're looking up at the space station, the astronauts are looking down and seeing the sights of Earth like this large thunderstorm cloud complete with anvil head. Credit: NASA
Or how about looking out the window and seeing this -- the city of London at night. Credit: NASA
Now that we're fully within the circle of summer, it's time for an International Space Station (ISS) marathon. During midsummer, the ISS is high enough and nights are short enough that not one, not two but many passes are visible throughout the night. Here's a short list of when to look for the next few evenings. Remember that during most passes, the station will first appear low in the west or northwest and cross the sky from west to east. Look for a very bright, moving "star". All times are Central daylight and are good across northern Minnesota and Wisconsin. Click here and type in your zipcode to get exact times for your location.
Sunday morning July 5: passes at 12:07 a.m. (this one very low and brief in the eastern sky), 1:39, 3:14 and 4:49.
Mon. July 6: 12:29 a.m., 2:03, 3:38 and then (thankfully!) evening passes begin with one at 9:44 p.m. and again at 11:17 p.m.
Tues. July 7: 12:52 a.m., 2:28, 4:03 and then in the evening at 10:06 and 11:41 p.m.
Wed. July 8: 1:17 a.m., 2:53, 4:28 and in the evening at 10:30 p.m.
Last night's moon wore a halo of light created by ice crystals in high clouds. Photo: Bob King
The moon will be in its fat gibbous phase tonight and lurking low in the southern sky in the constellation Ophiuchus (oh-phee-YOU-kuss). When constellation boundaries were set by the International Astronomical Union in 1930, the southern boundary of Ophiuchus the Serpent Bearer was drawn to include part of the traditional zodiac. Every month the moon spends a day (at most two) traversing Ophiuchus while swinging from Scorpius to Sagittarius. Sadly, it's unlikely that astrological tradition will allow Ophiuchus official membership in the Club d'Zodiac, so it will probably always be considered the family's dark sheep.
This map shows the sky as you look east around 11 p.m. when Vega is up high. The direction our sun and solar system are traveling among the neighboring stars is marked. Maps created with Stellarium.
While you're out getting your moon tan, lay back in a lawn chair or on the grass with your feet pointed south around 11 o'clock. Look straight up. The really bright star to your left but nearly overhead is Vega, the Alpha star in the constellation Lyra. Just shy of one outstretched fist below Vega is the point in outer space that bears the lofty name the Apex of the Sun's Way. As our galaxy rotates, it carries all the stars in a grand circle about its center. Those closer to the center complete one orbit in a shorter time than those near the edge. Traveling at 137 miles per second, our sun takes 220 million years to go around once, a period astronomers call a cosmic year.
This closeup view shows that the Apex of the Sun's Way lies right along the border of Hercules and Lyra.
The sun also has its own individual motion with respect to the local neighborhood stars. It's moving at some 12 miles per second in the direction of the constellation Hercules just southwest of Vega. Put simply, this is the point in space you, I, the sun and all the planets are headed toward.
A current illustration of the Milky Way galaxy showing its spiral arms, the bright, star-rich core and a bar of stars on either side of center. The sun is located in a spiral arm about 2/3 from center to edge. Credit: This image is copyright Mark A. Garlick and has been used with permission. No other use is granted unless the artist is contacted.
While you're out tonight, gaze up toward Vega and imagine your incredible journey through space. You're riding a rotating Earth that orbits the sun. The sun is speeding through the neighboring stars toward Vega, and the whole works flys around the center of the galaxy at many miles per second. There's no such thing as standing still.
Posted by: rking@duluthnews.com on 7/4/2009 at 11:02 AM | Comments (0) | Permalink
Astronomy comedy
A couple goes for a magic carpet ride in the evening moonlight in this mural on the Arabian Daze Fun Haus. The painter threw in another interesting detail, the Mercedes-Benz hood ornament on the carpet's leading edge. Photo: Bob King
I can get pretty excited about small things so please indulge me a moment when I tell you how thrilled I was to see this painting of the crescent moon on the side of the Arabian Daze Fun Haus at the Mighty Thomas carnival. The carnival set up in town earlier this week and my job was to illustrate its effect on downtown parking.
What caught my attention about the airbrushed painting of the hapless man and voluptuous princess on the magic carpet was that the creator had the moon's phase correct. Not that any phase of the moon is incorrect, but just about every cartoon representation of the moon has the phase reversed. Astute skywatchers will know that a crescent lit on the right side appears in the evening sky. One lit on the left side only appears very low in the east at dawn.
The top cartoon is a strip from the Wizard of Id; the bottom from B.C. Both show how cartoonists represent nighttime by using a backwards (dawn) crescent rather than a night crescent moon. Credit and copyright: johnhartstudios.com
A year ago I wrote about this topic and artistic license, etc. etc., but unless cartoon characters are different, most people aren't up at dawn reflecting on life, watching TV or just crawling into bed. Am I being too literal? Well, yes, probably. We'll just take it as a fun observation of our ever-inventive culture.
Today the Earth is farthest from the sun, a point in our orbit called aphelion (ap-HEE-lee-un). We travel about the central heating unit in a slightly elliptical orbit with the sun offset from the center. In January, we're a couple million miles closer to the sun (perihelion) but because it's winter in the northern hemisphere at the that time, we don't notice any increased heating. Come July, we're farthest, but since it's summer, the decrease in heat doesn't matter a whit. You might think folks in Australia would feel the chill since it's winter down under, but the vast amount of ocean in that part of the world ameliorates the effect.
Layers of dusty ice near Mars' south pole. Hi-res image here. Credit: NASA/JPL/University of Arizona
Now that we've touched on winter, how about those Zamboni tracks on Mars? This recently-released photo was taken by the Mars Reconnaissance Orbiter satellite of an area near the planet's south pole. The landscape there consists of multiple layers of dusty ice stacked one atop the other. Some kind of erosional process has scooped down below the surface to show centuries of deposits that resemble the pattern a Zamboni makes while clearing an ice rink. Gorgeous, isn't it?
Posted by: rking@duluthnews.com on 7/3/2009 at 11:09 AM | Comments (2) | Permalink
How thin would you like that sliced?
Will the sky ever clear in northern Minnesota? To everyone living outside the region, I hope you've been enjoying summer sunsets and sunrises. It feels like a different season here. The leaves are green but the sky's been grey and low for almost a week with temperatures in the 50s and 60s.
Look to the south tonight (Thurs.) and tomorrow night to watch the moon beam in on Scorpius' brightest star, Antares. Created with Stellarium.
Tonight the clouds may finally break and when they do, the gibbous moon will cast a glorious light. You'll find it a little more than one outstretched fist to the right of Antares, the bright red star in Scorpius the Scorpion. Tomorrow the moon will move to within just a few degrees of the star. Hmmm .... degrees. What exactly is a degree?
Every month as the moon orbits the Earth, it travels a full 360-degree circle around the sky. If you divide 360 degrees by 30 days, you get 12 degrees of movement per day along the circle. Since a fist held horizontally at the end your arm spans an angle of 10 degrees, a good rule of thumb to remember is that the moon moves to the east in its orbit (which translates as "left" in the northern hemisphere) about one fist a day.
Now let's break this daily movement down into individual degrees. One degree of sky is equal to two full moons side by side, or the amount of sky you can cover with your little finger. Since it takes two moons to make one degree, that means the moon must be 1/2 degree in diameter. If you do a little division, you discover that the moon moves its own diameter eastward in one hour's time. That's slow enough that the Earth's rotation still carries the moon in the opposite direction -- east to west -- over the course of the night.
Most things in the night sky are much smaller than one degree. Planets show as disks but to see much detail on them, you have to use at least 20x magnification. Illustration: Bob King
Shall we chop things a little finer? Every degree is subdivided into 60 minutes. I know that sounds confusing, since it's the same term used to divide time, but stay with me a moment. The minutes that make up a degree are called "minutes of arc" to distinguish them from time's minutes. The moon's diameter is 1/2 degree or about 30 minutes of arc. A nice-sized crater would be in the neighborhood of three arc minutes. When Venus is closest to the Earth, it measures just one arc minute. We can further subdivide a minute into -- you guessed it -- seconds of arc. Jupiter is 45 seconds across while Mars never gets bigger than 25 seconds. No wonder you need to a telescope to see any detail on these planets! They're tiny.
We can go smaller of course. The planet Neptune is only two seconds in diameter while the dwarf planet Pluto is a mere 0.13 seconds. Only very large telescopes can resolve Pluto as a disk. By the way, minutes are often abbreviated as a simple apostrophe, and seconds to a quotation mark -- 30' stands for 30 minutes while 30" is 30 seconds.
Using powerful instruments like the Hubble Space Telescope, Betelgeuse is one of very few stars large enough to show a disk. Credit: NASA/ESA
How about the stars? They're all incredibly small because of their vast distances from Earth. No amateur telescope and most professional telescopes can't resolve their tiny disks. They look like so many bright pinpoints even with magnification.
One of the largest naked eye stars, Betelgeuse in Orion the Hunter, is 427 light years away and just .055 seconds or 55 milliarcseconds across. When you know that the star's true diameter is something like 690 million miles or 800 times larger than the sun, it helps you to appreciate just how far away they really are.
Posted by: rking@duluthnews.com on 7/2/2009 at 12:53 PM | Comments (0) | Permalink
Feathery nighttime companions; colorful sunsets ahead
A Virginia Ctenuchid moth rests on my door this morning. The moth uses its feathery antennae to sense smell so it can locate food or a mate. Recent research has shown that they also help the moth remain balanced during flight. Photo: Bob King
Moths and amateur astronomers are both creatures of the night. One of the first signs of new life after winter are the moths that catch the beams of our headlights while driving at night in the countryside. I found this moth on my front door window just this morning and went in for a closer look. We share at least one more similarity with moths -- we're both drawn to the light. Scientists believe moths use moonlight for navigation; amateur astronomers use starlight to take them places only the mind can go.
Aerosols from erupting Alaskan volcanos last summer created very colorful sunsets. This photo was taken in early September 2008. Watch for another round from a different eruption this summer. Photo: Bob King
Yesterday I briefly mentioned the fallout from the Sarychev volcano. Sunsets and sunrises have been very colorful across the northern U.S. and Europe due to volcanic aerosols lofted by the eruption. Fine particles of ash and sulfur dioxide gas are carried by winds in the stratosphere and spread over thousands of miles. These small particles scatter blue light very well. When blue mixes with the reds of sunset, the sky in the west takes on a distinctive purple glow. Nearer the western horizon look for thin, pale white bands, which are also caused by high-flying volcanic particles.
NASA's LRO went into orbit around the moon last Saturday, June 27. Illustration: NASA
Good news for NASA -- the Lunar Reconnaissance Orbiter (LRO) has achieved lunar orbit and after a 60-day period of checking each of its instruments, will begin mapping the moon's surface in unprecedented 3-D detail. This is the first step in an ambitious new program to return people to the moon by the year 2020. If all goes according to schedule, the astronauts will descend to the surface in a 4-person lunar lander that was just recently named "Altair", after the bright Eagle Star in the summer constellation Aquila.
The other half of the mission, called LCROSS, will crash a rocket stage into a crater near the moon's south pole in hopes of liberating water from its interior. The LCROSS is currently buzzing along in its cruising orbit preparing for an October 9 impact. Amateur astronomers have even succeeded in photographing it with large telescopes.
An earlier transit of Titan (moon in front of planet, left) and its shadow taken by the Hubble Space Telescope on February 24, 2009. Credit: NASA/ESA
A special alert for amateur astronomers with 6-inch or larger telescopes -- tonight is the final, easily-visible shadow transit of the year of Saturn's moon Titan for observers in the Midwest and Mountain states. There will be more transits for points further west but this wraps it up for much of the country until the year 2024, the next edge-on presentation of Saturn's rings.
Tonight's event starts at 9:42 p.m. Central time (July 1), when the shadow will take a small bite from the eastern edge of the planet. Over the next few hours, the tiny black dot will cross the planet's northern hemisphere. Go out early when the planet is highest in the west. If you wait, it'll be so low that atmospheric turbulence will make the shadow impossible to see.
Posted by: rking@duluthnews.com on 7/1/2009 at 10:56 AM | Comments (2) | Permalink
Spica and the lowdown moon
The moon and Spica tonight (June 30). While you're out this evening, watch for purple-tinted skies during twilight from aerosols lofted into the upper atmosphere by the Sarychev volcano near Japan. More on this in tomorrow's blog. Created with Stellarium
We've been hit big time here in Duluth by clouds, but if it's clear by you this evening, take a moment to enjoy the waxing moon in the company of Spica, the brightest star in Virgo the Virgin. Spica is very close to the ecliptic, the path the moon, sun and planets travel along in the sky. This guarantees a regular monthly visit.
If Spica's so close, how come the moon's still so far away from it? It happens that the moon's orbit is tipped relative to the Earth's. If it were exactly flat and concentric to the Earth's orbit, it would travel along that imaginary red line month after month, year after year, never varying. This week, the moon is near the bottom or most southerly point in its orbit at the same time it passes near Spica. That places it significantly further south of the star than usual. Matter of fact, the moon's so low from the northern U.S., it hardly clears the trees around my house by nightfall. During a different month or year, the moon might be found right on the ecliptic, above Spica or even covering it up in an occultation.
That little tip sure keeps things interesting.
Posted by: rking@duluthnews.com on 6/30/2009 at 4:49 PM | Comments (0) | Permalink
