You are here: Home USNO News, Tours & Events Sky This Week The Sky This Week, 2015 February 24 - March 3

The Sky This Week, 2015 February 24 - March 3

Distant Suns, nearby Moon.
The Moon, Venus, & Mars, 2015 February 20
Imaged from Alexandria, VA
Canon EOS Rebel T2i DSLR, EF-S 55 - 250mm zoom lens, 0.8s @ f/8, ISO 3200

The Moon brightens our wintry landscape this week as she wends her way through the heart of the seasonal constellations.  First Quarter occurs on the 25th 12:14 pm Eastern Standard Time.  Look for the bright star Aldebaran less than a degree south of the Moon on the evening of the 25th.  On March 2nd she passes five degrees south of bright Jupiter.  

This should be a banner week for novice telescope owners to give our natural satellite a good, long look.  As the Moon waxes through her gibbous phases she is placed high on the ecliptic, so you’ll be looking at her through a much less dense airmass than at other times of the year.  Some of the best observing conditions seem to occur when the night is cold and still, so it’s a good time to push your optics to their limits.  Very modest telescopes will show a wealth of detail on the Moon’s battered face, and I often find myself looking at details that I’d never noticed before.  A “must-have” accessory for exploring Luna’s surface is a good lunar map; by associating names with particular features you’ll remember them each time you see them.  There are many good atlases available in book form as well as software and smart phone apps that will enhance your appreciation of the Moon and her features.  If you’re like me you’ll find yourself exploring our nearest space neighbor whenever she’s well-placed and the sky is clear.  It’s the only other place in our solar system that we’ve explored “first-hand”, and it’s the easiest one to visit from your back yard.

Despite the increasing glow of the waxing Moon, the winter constellations hold their own thanks to the preponderance of bright stars in their midst.  The outline of Orion crosses the meridian at the end of evening twilight, marked by the bright stars Betelgeuse and Rigel along with his distinctive “belt” of the stars Alnitak, Alnilam, and Mintaka.  These three stars are some of the most intrinsically bright stars in our sky, and if our eyes were more sensitive to ultra-violet light they would be among the brightest objects that we would see in the night.  It is estimated that Alnilam, the middle star in the belt, is some 275,000 times more luminous than our Sun.  At its distance of some 1300 light years it appears as a second-magnitude star, but if we were to magically place it at the distance of Sirius, 8.5 light years, it would appear brighter than the Full Moon and its powerful UV radiation would necessitate wearing sunblock at night!  As it turns out most of the bright stars in Orion are between 500 to 1500 light years away from us and form a loose association with each other.  A planet located in the heart of this association would probably never experience the darkness of a moonless night that we are able to enjoy.

Back in our own tiny neck of the galactic woods, we find bright Venus rapidly moving away from ruddy Mars.  The two planets had a beautiful conjunction last week, accentuated by the nearby waxing crescent Moon.  This provided for a wonderful photo opportunity, and I was pleased to see the wonderful images captured by astro-imagers from around the world on social media.  You’ll have another opportunity to see this trio again this year in the pre-dawn sky of November 7th.

The bright glow of Jupiter won’t be affected by the light of the Moon.  He appears in the eastern sky as evening twilight falls, then works his way to the meridian as the evening progresses, transiting at around 11:00 pm.  Of all the planets Jupiter holds the most interest for owners of small telescopes, subtending the largest disc of any planet except Venus at certain times in her apparitions.  Unlike Venus, though, Jupiter shows details that become increasingly sharper and more diverse as larger aperture instruments are applied.  It is hard to appreciate the scale of Old Jove until you realize that an atmospheric feature like the Great Red Spot is as large in surface area as that of the entire Earth, or that Ganymede and Callisto, the two largest Galilean moons, are bigger than the planet Mercury.  You can try to see the Red Spot on the evening of the 25th and again on March 2nd; on the latter night the moon Ganymede will drag its shadow across the planet’s face. 

Saturn beckons us in the morning sky with a promise of warmer weather to come.  The ringed planet is located among the stars of Scorpius, one of the signature constellations of the summer.  Right now you’ll have to suffer the chill of the pre-dawn sky to see him well in a telescope, but by the time he’s well-placed in the evening sky I’ll be observing him in shorts and swatting mosquitoes!




USNO Master Clock Time
Javascript must be Enabled