SKYLIGHTS

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

billowing clouds

Photo of the Week. Silver linings.


Astronomy news for the two weeks starting Friday, February 13, 2015.

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. 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.

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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 February 27, 2015.

Our fortnight opens with the Moon thinning in its waning crescent phase as it approaches new on Wednesday, February 18, your last look in the east the morning of Thursday the 17th with Mercury to the right. The previous morning, the little planet will be down and to the left of the crescent. Making a decent appearance, Mercury goes through its greatest western elongation from the Sun on Tuesday the 24th. The Moon then flips to the other side of the sky, appearing as a waxing crescent in the west with first look the evening of Thursday the 19th, the Moon nearly at perigee, where it is closest to Earth. It then heads toward first quarter on Wednesday the 25th, after which it will enter the waxing gibbous phase.

The planets (indeed, with the Moon) give us a special treat during the middle of our period. Mars has been slowly working its way north as it falls behind Earth, but has been setting around 8 PM since early last November. At the same time, Venus has night-to-night been slowly and brilliantly creeping up (you can't miss it in western twilight), the two approaching each other. Finally, on Saturday the 21st, they meet in conjunction just half a degree apart, the angular diameter of the full Moon, Mars to the north. The contrast is remarkable, Venus a creamy white, Mars a yellow-orange, even reddish color, Venus some 100 times brighter. Even better, on that night the Moon gets into the act, the slim crescent hovering above the two. The evening before, a slimmer crescent passes a couple degrees north of them. The planets then slowly separate as each night Venus climbs ever higher.

What's left but Jupiter, which is now already up in the east as the sky darkens and transits the meridian shortly before midnight?. Moving slowly retrograde, westward against the stars, Jupiter stands brightly between Leo and dim Cancer to the west of the star Regulus. Oh, but then there is Saturn rising a couple hours after Jovian transit, and Neptune, which invisibly goes through conjunction with the Sun on Wednesday the 25th. And speaking of the Sun, it's slowly creeping northward toward the Vernal Equinox and northern spring and is now a full 10 degrees north of the Winter Solstice parallel.

In early evening, Orion and the rest of the winter gang ride high. But as Jupiter announces, Leo and spring are not far behind. To the northeast the Big Dipper rises, while the "W" of Cassiopeia descends. Lonely Polaris, however, maintains its steadfast position, up from the horizon at an angle about that of your latitude: the first law of celestial navigation.

STAR OF THE WEEK: HR 1040 CAM (HR 1040 Camelopardalis). Massive stars (indeed probably all stars) tend to be born in groups within the cold dusty clouds of interstellar space. They burn out fast and consequently don't get very far from their birthplaces, and thus form expanding "OB associations" named after the spectral classes of the hot dwarfs that occupy them. Some are tight and compact, while others, like the Cam OB1 association (mostly in the far northern constellation, Camelopardalis, the Giraffe), spread rather widely. Cam OB1 is dominated visually by the fourth magnitude (4.21) class B (B9) bright supergiant HR 1035 and just-barely fifth magnitude (4.54) HR 1040 (a similar A0 bright supergiant), the designation referring to their listings in the "Bright Star Catalogue." Oddly, ranking numbers 2 and 5 in brightness within the constellation, they carry neither Greek letters nor Flamsteed numbers. HR 1035 (which is only about a degree north of HR 1040) is the brighter because there is less absorbing interstellar dust in the way. Were there none, HR 1040 would appear one and three-quarter magnitudes brighter and shine at magnitude 2.78, reversing their roles. The higher dust absorption is probably because of HR 1040's greater distance of 2510 light years, as opposed to 1035's distance of 1940 l-y. Such distances, though, are fraught with uncertainties. HR 1040 could statistically be as near as 1750 l-y or as far as 4400 l-y. HR 1035 has a similar problem. All we can do is adopt the star_intro.html#brightness">parallax measure and hope for the best.

HR1035 HR 1035 at left and HR 1040 at right are both related to dusty interstellar clouds that reflect or, more accurately, scatter their starlight. The scattering process is much more efficient toward shorter spectral wavelengths, which gives the "reflection nebulae" a bluish color, not seen here in this early black and white photograph. (Palomer Sky Survey.)

Given a temperature of 10,540 Kelvin there is only a little ultraviolet radiation to add. With the nominal distance we then find a huge luminosity of 51,000 times that of the Sun, 70 percent more than 1035's and similar to that of Deneb's, whose slight variable nature it mimics (and is thusly also called CE Cam), the star among the great ones of the local Galaxy. Luminosity and temperature give a radius of 68 times that of the Sun, about 80 percent the size of Mercury's orbit. Theory yields a mass of 15 times that of the Sun if the star is in transition to the red supergiant state with a dead helium core or maybe 13.5 solar masses if it is in a quiet state of core helium fusion. Unlike HR 1035, HR 1040 appears all alone, with no binary companion. Both stars are within or near dusty clouds that reflect, or scatter, their tremendous light. HR 1040 seems to be buried in such a "reflection nebula" (the most famed of which surrounds the Pleiades) that is roughly two light years across. The most amazing thing perhaps is that such stars are nearly lost within obscure constellations that have practically no "outline" to speak of, figures one would be hard-pressed to find. And there are others. Also belonging to Cam OB1 is the sixth magnitude (5.79) class A0 bright supergiant HR 964, the sixth magnitude (5.76) K4 lesser supergiant HR 1112, and the sixth magnitude (5.77) B0 giant HR 1417, better known perhaps as 1 Cam (at least one star got a Flamsteed number), after which we run out of naked eye stars.


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