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[...] readers of this column will recall that Omicron Eridani & Sirius B are closer, but Omicron Eridani is in a trinary star system and Sirius B is [...]
The Sky is Waiting.
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Pictured is a Delta IV rocket launch from Cape Canaveral on November 21st, 2010. The image is a 20 second exposure taken at dusk, shot from about 100 miles west of the launch site. The launch placed a classified payload in orbit for the United States Air Force.
Difficult but not impossible to catch against the dawn or dusk sky, spotting an extreme crescent moon can be a challenge. The slender crescent pictured was shot 30 minutes before sunrise when the Moon was less than 20 hours away from New.� A true feat of visual athletics to catch, a good pair of binoculars or a well aimed wide field telescopic view can help with the hunt.
The Sun is our nearest star, and goes through an 11-year cycle of activity. This image was taken via a properly filtered telescope, and shows the Sun as it appeared during its last maximum peak in 2003. This was during solar cycle #23, a period during which the Sun hurled several large flares Earthward. The next solar cycle is due to peak around 2013-14.
Located in the belt of the constellation Orion, Messier 42, also known as the Orion Nebula is one of the finest deep sky objects in the northern hemisphere sky. Just visible as a faint smudge to the naked eye on a clear dark night, the Orion Nebula is a sure star party favorite, as it shows tendrils of gas contrasted with bright stars. M42 is a large stellar nursery, a star forming region about 1,000 light years distant.
Orbiting the planet in Low Earth Orbit (LEO) every 90 minutes, many people fail to realize that you can see the International Space Station (ISS) from most of the planet on a near-weekly basis. In fact, the ISS has been known to make up to four visible passes over the same location in one night. The image pictured is from the Fourth of July, 2011 and is a 20 second exposure of a bright ISS pass.
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Next to the Sun, the two brightest objects in the sky are the Moon and the planet Venus. In fact, when Venus is favorably placed next to the Moon, it might just be possible to spot the two in the daytime. Another intriguing effect known as earthshine or ashen light is also seen in the image on the night side of the Moon; this is caused by sunlight reflected back off of the Earth towards our only satellite.
A mosaic of three images taken during the total lunar eclipse of December 21st, 2010. The eclipse occurred the same day as the winter solstice. The curve and size of the Earth�s shadow is apparent in the image.
Astro-Challenge:Spy a White Dwarf!
This week, I’m going to introduce you to a unique but fascinating multiple star system, and one that’s definitely worth seeking out as it’s a good study in comparative stellar evolution; Omicron Eridani. This one will require a telescope of about 4′ aperture or greater, a go-to scope or a good finder chart, and patience. But the quarry is worth it; for Omicron Eridanus B is a white dwarf, the most easily observable in the sky, paired with C, a red dwarf star! Omicron Eridani is a triple star system, about 16.5 light years distant. The primary star, a K type main sequence star, is visible to the naked eye at a magnitude of about +4.5. Known to the Arabs as Al Keid (�the Egg�),
the star system may also be familiar to science fiction fans as 40 Eridani, home of the planet Vulcan in the Star Trek series. In fact, NASA has listed 40 Eridani as one of the top 100 targets for its Terrestrial Planet Finder mission. Omicron Eridani is orbited by a pair, one each white dwarf and red dwarf at 83� arc seconds of separation or an actual distance of 400 Astronomical units (AU). �B� has a visual magnitude of about +9, while �C� is a bit tougher, at about magnitude +11 and a very low stellar mass of 0.2 suns. The B-C pair orbit at a distance of about 34 AU and are closing the gap since a maximum separation of 9� in 1990. in 2080, a minimum separation of about 4� seconds will be attained. The binary nature of Omicron Eridani has been known since the discovery of the A-B pair by William Herschel in 1783, and the separation of the B-C pair was discovered by Otto Struve in 1851. The white dwarf nature of the B component was first deduced in 1910. Although not the nearest to our own solar system (Sirius B is closer at 7 light years), Omicron Eridani B is the easiest to observe, because Sirius B tends to be swamped in the primaries glare. It was also the first white dwarf discovered…and for those with setting circles, the coordinates for Omicron Eridani are;
R.A. 04H 15 min and 16 secs & Declination -07 degrees 39′ 10�.
As the Full Moon comes and goes on December 2nd, give this unique star system a shot…Live long, and prosper!
The astro-term of the week is white dwarf. A white dwarf such as Omicron Eridani B is a degenerate star at the end of its life. A main sequence star like our Sun will eventually wind up as a white dwarf once it has exhausted or shed its supply of hydrogen, helium and carbon. The remaining core is about the diameter of the Earth and will no longer be able to sustain itself via fusion and thus become incredibly dense; about 1 ton per cubic centimeter. Electron degeneracy is not a commentary on the stars’ moral state; rather, its the outward force that prevents further collapse and the maximum upward limit (also known as the Chandrasekhar limit) for a white dwarf is about 1.4 solar masses. White dwarfs can thus be thought of as slowly cooling cinders, radiating away energy until becoming cold black dwarfs. This happens over an extremely long time; its estimated that a white dwarf will last for about 1015 years, which is well past the current estimated 13.7 billion year age of our universe! White dwarfs will be with us for some time!