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


Photo of the Week: Sunrise.

Astronomy news for the two weeks starting Friday, February 24, 2017.

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, now in Chinese translation.

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.

SSLive in town? Read FIRST MAGNITUDE: A Book of the Bright Sky, World Scientific, 2013. See the interview with Jim Kaler.

NEW! Read Dust to Dust in Stellar Stories.

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

IT'S HERE!, From the Sun to the Stars by Jim Kaler, World Scientific, 2016, a new book based on From the Sun to the Stars: the OLLI Lectures, which provides a linked, illustrated introduction to astronomy.

Please Note

Skylights has been produced in various forms for 31 years, since 1985, and even before that as an annual bulletin. It's now time to simplify Skylights and bring parts of it to a close. We will continue to list lunar phases, planetary passages, and other significant events for the coming two-weeks prtiod on this website, but by bullet, not prose text. Because there will no longer be any script, the telephone and emailing services have been dropped. The Star of the Week will continue as before, as will the Photo of the Week. Thanks all for your support.
Jim Kaler

The next Skylights will appear Friday, March 10.
Primary source: The Astronomical Almanac.


107 PSC (107 Piscium)

The naked-eye sky is made almost entirely of stars more luminous - really much more luminous - than the Sun. Otherwise stars are so distant that you would not see them. Put the Sun - a pretty standard class G dwarf - at 30 light years and it would be about bright as the faintest stars of the Little Dipper. The constellations are made mostly of hot class A and B hydrogen-fusing dwarfs above 9000 Kelvin and cool orange evolved class K Proxima Centauuri. Even class K dwarfs are rare and faint, the outstanding exception being Alpha Centauri B, the K1 companion to brighter G2 Alpha Cen. By itself, Alpha Cen B would be the third brightest star in the sky. Among the most famed of K dwarfs is the K5-K7 double star 61 Cygni, whose distance was first measured via parallax. Others of note are the (again) binary K0-K5 70 Ophiuchi and Epsilon Indi. Almost all K dwarfs are less massive than the Sun. Their importance is in the study of magnetic fields and cycles and how they relate to those of the Sun. Here's another. In far eastern Pisces we find the fifth magnitude (5.24) class K (K1) dwarf 107 Psc; since the Flamsteed numbers go just to 109 Psc, it must be close to the Aries border. To be visible to the naked eye, 107 Psc must also be close, and it is, just 24.6 light years (give or take just 0.1) away. With a temperature of 5196 Kelvin, 107 Psc shines with the light of just 0.45 Suns. The radius comes out to be 0.81 times that of the Sun. Interferometric observations give 0.76 times solar, in decent agreement. The mass appears then to be about 90 percent that of the Sun, though one study gives 1.01 Suns with a 4.6 billion year age. From the variation in its chromospheric (the "chromosphere" the layer just outside the photospheric surface), the star has a rotation period of 33.7 days with a 9.8 year starspot or magnetic cycle. A projected equatorial velocity of 1.7 kilometers/sec indicates an axial tilt to the plane of the sky of about 45 degrees. Sort of approaching us, 107 Psc will eventually come to within 15 light years of us, when it will shine about a magnitude brighter. A pair of 12th magnitude companions hover some 1 and 3 minutes of arc away, but their motions suggest that they are just line of sight coincidences. There seems to be no dusty disk around the star that might indicate a planetary system" .

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