Skylights featured on Astronomy Picture of the Day

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Skylights featured nine times on Earth Science Picture of the Day: 1 2 3 4 5 6 7 8 9

Waxing Moon

Photo of the Week.Third quarter in morning's light.

Astronomy news for the two weeks starting Friday, November 21, 2014.

Phone: (217) 333-8789
Prepared by Jim Kaler.

Clear skies and thanks to Skylights' blogger visitor reader.

Go to STARS for previous stars of the week. Last week's Skylights is still available. Access Skylights' Archive and photo gallery. From the Sun to the Stars: the OLLI Lectures provides a linked, illustrated introduction to astronomy.
The Constellations has a linked list with locations and brightest stars. Constellation Maps show the locations of the constellations. The 170 Brightest Stars lists them through magnitude 3.00. For more on stars and constellations, visit Stellar Stories.
Tour the Milky Way. Watch a total eclipse of the Moon and an annular eclipse of the Sun. Moon Light presents scenic photos of the Moon. Go to MoonScapes for labelled telescopic images of the Moon and other lunar information.
See the Moon move and pass just below Nu Virginis. Watch planets move against the background stars. See a classic proof of the curvature of the Earth with a "hull down" series. Visit Measuring the Sky to learn about the celestial sphere.
Admire sunsets, rainbows, and other sky phenomena in Sunlight. Read the illustrated Day Into Night on the phenomena of the sky See the The Aurora and the Midnight Sun. See and understand the ocean tides.
Enjoy Our Complex Universe: A Human Understanding through Art, with 12 illustrations. Advances in Astronomy, 1989-2011. Take a ride aboard Asteroid 17851 Kaler (1998 JK). Look for Books about the sky and stars.


ASPSupport science literacy by joining the Astronomical Society of the Pacific, an international organization that is among the world's premier providers of astro education. Get Mercury and a variety of other benefits.

Presenting three audio courses with 70 to 100-page study guides, narrated and written by Jim Kaler.
Heavens Above: Stars, Constellations, and the Sky from Recorded Books. Astronomy: Earth, Sky, and Planets, is available from Recorded Books. Astronomy: Stars, Galaxies, and the Universe, is also now available from Recorded Books.
Astronomy: Earth, Sky, and Planets is published as Vault of the Heavens: Exploring the Solar System's Place in the Universe by Barnes and Noble.

Enjoy Our Complex Universe:A Human Understanding through Art, with 12 illustrations.

Read "Heaven's Touch: From Killer Stars to Seeds of Life, How We Are Connected to the Universe," Princeton University Press.

SSTo learn about stellar spectra, read STARS AND THEIR SPECTRA: An Introduction to the Spectral Sequence, Second Ed., with two new chapters and 140 new illustrations, Cambridge University Press (UK or North America), 2011.

Read From the Sun to the Stars: the OLLI Lectures, which provides a linked, illustrated introduction to astronomy.

SSNEWEST! FIRST MAGNITUDE: A Book of the Bright Sky, World Scientific, 2013. Read the interview with Jim Kaler.

NEW! Read Under the Handle in Stellar Stories.

The next Skylights will appear Friday, December 5.

Another fortnight (necessitated by a move, Thanksgiving -- wishes for a happy one to all -- and other things) pretty much spans the waxing half of the lunar phase cycle. New Moon takes place on Saturday, November 22, and is followed by the waxing crescent (first visible in western twilight the evening of Sunday the 23rd), first quarter on Saturday the 29th, then the growing gibbous, which terminates at full Moon on Saturday. December 6. The evening of Tuesday the 25th, the crescent will appear to the right of Mars, while the following evening it will be up and to the left of the red planet. For planetary passages, that is about it except for Neptune on Saturday the 29th and Uranus on Monday the 1st, the planet occulted as seen from western Canada and eastern Alaska. On Thursday the 4th, the lunar disk will appear to the west of Aldebaran and the Hyades of Taurus and to the south of the Pleiades. More significantly, the Moon goes through perigee, where it is closest to the Earth, on Thursday the 27th.

Dominating the sky, Jupiter rises ever earlier in Leo a bit to the west of Regulus just after 10:30 PM at the beginning of our session, 9:30 at the end of it. Mars, falling only slowly behind the Earth, maintains its constancy, setting at 8 PM as it glides to the east of Sagittarius's Little Milk Dipper approaching Capricornus. The other three ancient planets, those known since ancient times, are hidden by the glare of twilight.

It's hard to miss the lowering of the Sun as it nears its most southerly point of the sky at the Winter Solstice in Sagittarius on December 21 with only a couple degrees left to go. Correspondingly, the temperate northern hemisphere receives less heat as a beam of Sunlight covers more ground and the air chills, while the southern hemisphere heats up.

In mid-evening, the star streams of Perseus, the hero of the Andromeda myth, climb high in the northeastern sky. The famed figure is followed by another of the great ancient constellations, Auriga, the Charioteer, instantly recognizable by Capella, the sixth brightest star in the sky, third brightest of the northern hemisphere, and the most northerly of first magnitude (actually magnitude zero), just barely beating Deneb in summer's Cygnus for the honor.

STAR OF THE WEEK: GORGONEA SECUNDA (Pi Persei). It's rather odd to see a fifth magnitude star (though at 4.70 on the bright side) with a proper name. But not when we look at its surroundings. Perseus, who rescued Andromeda, is known for its many massive, hot, blue stars, the Alpha Persei Cluster that surrounds and includes the constellation's luminary, the striking young Double Cluster, and perhaps topping them all, Algol, Beta Persei, the Demon Star that represents Medusa, the hideous gorgon (one look turns you to stone) slain by the famed Hero. Traditionally there were three gorgons. In Perseus there are four (mythology seemingly quite flexible), as three others hover to the south made of a close triangle of fainter stars, the second (Gorgonea Secunda), third (Gorgonea Tertia), and the fourth (Gorgonea Quarta), which are much better known by their Greek letter names as Pi, Rho, and Omega Persei (Algol also Gorgonea Prima). Oddly, they are all about the same brightness and distance, Pi Per 310 light years away (with an uncertainty of 8), Rho and Omega Per at a distance of 308 and 288 light years. Though they at first might seem to be related as some kind of a spread-out cluster, they have nothing to do with one another, as their motions are wildly different, their placement from Earth merely a coincidence. They are also very different kinds of stars, our Pi Per a class A (A2) dwarf, Rho an M4 bright giant, and Omega a common K1 giant. Focusing back on Pi, it could certainly use more work. Published temperatures range from 8180 to 9290, with an uncertain mean of 8700, which is a bit low for an A2 dwarf. Given most of the light in the visual spectrum, with distance we find a luminosity of 96 times that of the Sun and a radius of 4.3 times solar The star could either be a failing dwarf (about to give up core hydrogen fusing) with a mass of 2.7 Suns or a "failed" subgiant of 2.5 solar masses. It will before long turn into a helium-fusing giant not dissimilar to Omega Per. Pi Persei's one outstanding feature is its rapid spin of at least 177 kilometers per second at the equator, giving a rotation period of under 1.2 days. The rotation rate is enough to keep the atmospheric gases stirred up so as to prevent abundance anomalies caused by gravitational sinking of some and radiative lofting of others. While not related to Pi Per (which has no known companions), the other two gorgons would present quite a sight to anyone looking from Pi.

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