February 10th, 2016
With the constellation of Aries the Ram still flying high over the south-western horizon in the evening, there’s still time to target an easy double star for small telescopes. Mesarthim is the best-known double in the constellation, but there’s another nearby there’s often overlooked.
Lambda Arietis is slightly off the beaten track but should still be quite easily found. It lies between two brighter stars – Hamal to the east and Sheratan to the west. Lambda appears slightly closer to Hamal in the map and finderscope views depicted here.
Some observers have reported this as being split with binoculars, but I’ve had no luck with my 10×50’s.
However, a low magnification of 26x should easily reveal a brilliant white star that’s about twice as bright as the bluish secondary. (On one occasion I noted hints of violet in the companion but the color seemed to disappear with a higher power eyepiece.)
A magnification of about 65x will provide a nice view. Look out for a third, slightly fainter companion nearby that forms an elongated triangle with the main pair.
Lambda is thought to be a true double star system as both stars appear to be moving together through space. In reality, both stars are actually yellow but the primary is hotter and its color is closer to yellow-white.
The reason the secondary appears blue is because your eyes are sensitive to contrasts in light and you see an exaggerated contrast effect as a result.
The stars lie at a distance of about 129 light years and take more than 33,000 years to orbit one another.
Text, map, finderscope and eyepiece depictions slightly adapted from my book, Easy Things to see With a Small Telescope, available in both Kindle and paperback formats from Amazon in the United States, Canada and the United Kingdom.
All Astronomical Events for February 10th, 2016
00:40 UT – The waxing crescent Moon is north of Neptune. (Neptune: magnitude 8.0, diameter 2.2”. Aquarius, not visible.)
Saturn increases its apparent diameter to 16.0”. (Magnitude 0.5, Ophiuchus, pre-dawn sky.)
Events in bold involve objects and/or events that are visible with the naked eye.
All times are in Universal Time (UTC). To convert the time to your timezone, click here.
Astronomical events taken from 2016: An Astronomical Year, available in Kindle and paperback formats from Amazon in the US, Canada and the United Kingdom. Night sky simulations created using Mobile Observatory for Android devices.
Easy Things to See With a Small Telescope
|2016: An Astronomical Year||2016: The Night Sky Sights||The Astronomical Almanac (2015-2019)||The Deep Sky Observer’s Guide|
(Kindle & Paperback)
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Details of all available books across the world can be found here or by visiting the author’s page on Amazon. If you have any comments or questions, please feel free to contact me at astronomywriter “at” gmail.com