Double stars en Urban Orion <!-- google_ad_section_start --><p><img width="135" vspace="4" hspace="8" height="180" align="left" title="The constellation Orion" alt="The constellation of Orion" src="/sites/" />Orion is not only the best known winter constellation, but it is also a great urban constellation. Thanks to its distinctive arrangement of rather bright stars, Orion shines through in heavily washed-out skies, even when few other constellations can recognized. It is also the home of the Great Orion Nebula (M42) big, bright, and easily visible even in washed-out skies. However, M42 is only the most famous of many interesting astronomical objects in Orion. And best of all for urban astronomers, quite a few of Orion's objects&mdash;like the constellation itself&mdash;can be enjoyed in light-polluted skies. Here is a run down...</p> <!-- google_ad_section_end --><p><a href="" target="_blank">read more</a></p> Double stars Planetary nebulae Emission nebulae Nebula filters Mon, 20 Feb 2012 15:26:57 +0000 Washed-out Astronomer 41 at Hunting the Great White Dwarf <!-- google_ad_section_start --><p>In the early 1900s astronomers were stunned to discover that some stars had masses comparable to the Sun's but packaged into earth-sized volumes. The first such stars discovered were spectral type A (white) and thus became known as <em>White Dwarfs.</em> The most famous white dwarf is Sirius B, the companion to Sirius. Most white dwarfs don&rsquo;t make good targets for washed-out astronomers because they are faint, inconspicuous stars or are hard to see companions to bright stars such as Sirius. But there is one white dwarf that is easy: 40 Eridani B.</p> <p><img width="166" hspace="4" height="94" align="left" title="40 Eridani A, B, and C by David Darling" alt="40 Eridani A, B, &amp; C by David Darling" src="/sites/" />40 Eridani (also known as &omicron;<sup>2</sup> Eridani or Keid) is a relatively bright 4<sup>th</sup> magnitude star. Even in urban areas, it is easy to find by star-hopping from Rigel going via &beta; Eri, &mu; Eri, and &nu; Eri. I recently did it from my light polluted front yard using a 50mm finder. Even looking directly over my neighbor&rsquo;s very bright holiday lights it was an easy hop. 40 Eridani is a triple star system. The primary has magnitude 4.4. Component B&mdash;the white dwarf&mdash;has magnitude 9.5 and is widely separated from A (83&rdquo;, PA 105&deg;) making it easy to see in even small telescopes.<em> (</em><a href=""><em>Image courtesy of David Darling</em></a><em>)</em></p> <p>As a special prize, the third component C is a red dwarf flare star of magnitude 11.2. The B-C separation is much tighter at about 8&rdquo; but it isn&rsquo;t hard to split except for the faintness of the C component. You&rsquo;ll probably need at least a 4 inch (100mm) aperature to see C in washed-out skies, but it&rsquo;s rather easy with 6 inches (150mm) or more. In my 10 inch (250mm) Dob, it looks pretty much like the photo above.</p> <p>So don&rsquo;t miss the chance to &ldquo;bag&rdquo; a white dwarf. If you want to learn more about white dwarfs, read the excellent <a title="White Dwarfs at Wikipedia" href="">Wikipedia article</a>. Now 40 Eridani is interesting for several other reasons, including a connection to <em>Star Trek</em>....</p> <!-- google_ad_section_end --><p><a href="" target="_blank">read more</a></p> Double stars Special stars Wed, 30 Dec 2009 17:03:54 +0000 Washed-out Astronomer 24 at Kruger 60 <!-- google_ad_section_start --><p><img width="70" vspace="1" hspace="8" height="190" align="left" src="/sites/" alt="Triplet of pictures showing Kruger 60&#039;s orbital motion" title="Triplet of pictures showing Kruger 60&#039;s orbital motion" />Kruger 60 is a particularly interesting binary star system in Cepheus. With a short period of only 44.7 years, you can easily see Kruger 60&rsquo;s PA change about 8 degrees per year. There&rsquo;s even a convenient nearby reference star that makes the change in PA obvious. Only 13 light years away, Kruger 60 is also one of Earth&rsquo;s nearest neighbors. Both components are low-mass red dwarfs, but with only 0.18 solar masses, Kruger 60 B is one of the lowest mass stars known. Finally, Kruger 60 B is also a flare star, irregularly doubling in brightness for periods lasting about 5 to 10 minutes. When it flares, it can match or exceed Kruger 60 A in brightness.</p> <p>Kruger 60, however, is a challenging target for observers in light polluted environments. If you want to take on this challenge, I have more information for you&hellip;</p> <!-- google_ad_section_end --><p><a href="" target="_blank">read more</a></p> Double stars Sat, 03 Oct 2009 22:09:58 +0000 Washed-out Astronomer 22 at