Jane Houston Jones » Sun

Observing in the neighborhood

jane — Thu, 21 Jun 2012 05:09:52 +0000

Summer Milky Way, Scorpius and dark nebulae, image by Morris Jones

Observing near the summer solstice means a short observing night sandwiched between a late sunset and an early dawn. Rather than rush through an observing project I find it’s a great time of the year to sit back and trace familiar constellations in my minds eye, and marvel with anticipation as the eastern horizon brightens. Soon, the stars of Scorpius and Sagittarius will rise and the “clouds” on the horizon take shape as lumps and glittery clusters, bisected by dark nebulae — those mysterious star-less regions within our Milky Way Galaxy.

It’s hard not to just sit and gaze at the unfolding spectacle. So for the first hour or two after darkness last Saturday night (June 16, 2012) I sat in my meteor observing chair and observed the sky with my own eyes. Every now and then I jumped up and eyeball-aimed Mojo’s 15-inch Litebox reflector at this cluster or that nebula. The sky conditions at Amboy Crater were near perfect.

We have 360 degree perfect horizons at this site, with small light domes from 29 Palms, and from departing trains. Temperatures are warm with just a hint of breeze, hot before sunset, shirtsleeve observing all night long, humidity 10% rising to 20% at dawn. Conditions are dry and warm. No dew. Ever! Here’s the Clear Sky Chart for Amboy Crater.

Lyra

Ophiuchus and Poniatowski's Bull

the demoted constellation Poniatowski's Bull and Ophiuchus

As I was looking at the constellation Lyra and its gem-of-a-telescope-target, the Ring nebula, M57, I spotted an asterism nearby, in the northeastern section of Ophiuchus that looked just like Lyra, except it was upside down.

That looked like a good place to select an observing project, so I cracked open my copy of the Night Sky Observers Guide, volume 2 Spring and Summer to the constellation Ophiuchus. I noticed this little group of stars that looked like Lyra were part of an open cluster, and that there was another pretty cluster in the neighborhood.

Best of all, Barnard’s Star was within the cluster! Barnard’s Star is the second closest star to the Earth — only 6 light years away, shining at a faint magnitude 9.5. The Alpha Centauri system, including Proxima Centauri, together are about 4 LY away, but we can’t see them from the US. Barnard’s Star has the greatest proper motion — the angular annual movement across the line of sight against the distant stellar background of any star. It moves 10.4 seconds of arc per year. That compares to a quarter of a degree in a human lifetime, roughly the angular diameter of the full Moon.

Amateur astronomers, carefully sketching or imaging Barnard’s Star once a year for a couple years can actually track the movement of the star. It’s a cool red dwarf. And it’s listed in Jim Kaler’s fabulous book The Hundred Greatest Stars. Jim writes “Barnard’s Star has a metal content only 10 percent that of the Sun. That coupled with its high velocity shows it to be a special, rather rare, kind of star called a “subdwarf” that more belongs to the metal-poor and ancient halo of our Galaxy (the Sun belonging to the disk). It is merely passing through our local neighborhood.”

You’ll definitely need a star chart to find it. Here’s one showing Barnard’s Star within the Melotte 186 star cluster with pretty IC 4665 nearby. This tiny faint red dwarf is a challenge, but it’s worth it, as are the two clusters.

The neighborhood it’s passing (to our line of sight), is through the demoted constellation Poniatowski’s Bull. This V- shaped set of stars looks like a bull’s head and horns in northeastern Ophiuchus. I see Lyra, instead, by adding a few other stars. It was named Poniatowski’s Bull (Taurus Poniatovii), to honor Stanislaus Poniatowski, King of Poland from 1764 to 1795. Named by Polish-Lithuanian astronomer and mathemetician Marcin Odlanicki Poczobutt whose observatory at Vilnius gained royal favor from the King.

So now, when you are looking at our Milky Way, notice Vega and her constellation Lyra. Then turn your head ever so slightly to the right, and you’ll see huge Ophiucus, which looks like a big percolator coffee pot to me. It’s above and between Scorpius and Sagittarius. The left star of the “lid” of the coffeepot is part of my “upside down Lyra”.

Nothing beats visual astronomy. Without taking the time to sit down and just look at the sky, and trace the constellations I never would have discovered this lovely demoted constellation for the first time!

There is always something to observe that you’ve never seen before, even if it is the same old stars. That’s what makes visual astronomy my go-to hobby. Pun intended!

Mojo’s images and writeup from the same night: predawn planets & astrophotography

More Fast Moving Stars

More Demoted Constellations

Early morning hikes – the Chuckwallas of Amboy Crater

The Crescent Moon

jane — Sat, 19 Feb 2011 21:47:05 +0000

The moon's summer and winter path, courtesy NASA's Starchild website

The winter's moon - a smiling crescent just after sunset Feb 5, 2011 (click to see moon upper center)

Closeup of winter crescent moon

The summer's "backwards C" crescent moon at sunset, late June 2007 (click to see moon in lower right)

Closeup of summer crescent moon

Have you ever wondered why the crescent moon looks like a smile in the winter and spring and like a backwards “C” in the summer and fall? It looked like a smile right now – below, next to and above Jupiter for several days after the February new moon. You can see the same waxing (getting bigger) crescent in early March 2011. Just look in the western sky after sunset beginning the day after new moon, on about March 5 or 6th. You’ll also see Jupiter and Mercury just above the horizon an hour after sunset.

Early birds can see a repeat of the waning (getting smaller) crescent moon phase a few days before the new moon, too. Look in east the last days of February up until new moon on March 4th. That bright object sharing the dawn skies with the crescent moon is the planet Venus! You can read more about moon phases here on the EarthSky website.

The best way to understand the reason why, is to look where the sun is, and how and where it shines on the moon. Draw an imaginary line connecting the setting sun, the moon, and any other planets that appear in the sky. That imaginary line is the ecliptic – the path the sun takes through the stars. It’s also the Earth and planets’ orbital plane. You can think of it as a projection of Earth’s plane on a sky sphere. The planets orbit the Sun, and the moon orbits the Earth and so you will always find the planetary lineup along the ecliptic.

In the winter and spring, the ecliptic appears almost vertical and arcs higher in the sky. The moons’ lit side faces the sun. That makes the waxing crescent moon look like a smile, or a boat, or the old moon in the new moons’ arms once light reflected off the Earth – called earthshine – reveals the unlit disk of the moon lit by reflected from Earth.

In the summer/fall, the ecliptic has a lower or shallower angle in the sky, and the lit crescent, as always, faces the sun, showing us a lit crescent facing the sun, which appears like a backwards “C”. I could write more, but instead, I’ll let you enjoy the images from our own observing sessions in the winter and the summer, and then get out and see the crescent moon for yourself soon.

A Ten Planet Night

jane — Tue, 15 Jun 2010 05:32:03 +0000

Setting up my favorite Pluto hunting telescope, a 17.5 inch f/4.5 Litebox reflector. Oh, in case you were wondering, its name is Hagrid. All my telescopes have names.

Chuckwalla Bench horizons

Earth shadow at sunset, and Mojo setting up his astrophotography rig

A starry necklace spans the sky from dusk to dawn

The planetary lineup from dusk to dawn

Two planets, Venus and Earth at sunset

M24 cluster and 60 day path of Pluto

Do you see the Sagittarius teapot and the Milky Way "steam" rising from the spout? How about M24, the huge Sagittarius starcloud (the oval of stars 1pm above center) where Pluto hides?

Earth shadow at sunrise

Bonus picture: This is the "naked eye" view of the sky where Comet McNaught can be found. Can you see the green comet near the Perseus Cluster? If not go to Mojo's Blog for closeup. Click to enlarge. It took binoculars for most of us to spot the first time.

Every couple of years I get the yearning to see all the planets in one night. Saturday night, June 12 seemed like the perfect opportunity. Our Old Town Sidewalk Astronomers club planned an outing to our regular observing spot, Chuckwalla Bench, which has very good horizons. We needed good horizons to catch Mercury rising just before sunrise.

Here are my planet observations, in observing order. All distances are listed in astronomical units and represent the distance from Earth on June 12, 2010, the night of my observations.

Earth! Facing away from the setting sun, the Eastern horizon turned shades of blue above the pinkish sky. That’s the shadow of the Earth! The dark blue band seems to rise above the landscape and spans 180 degrees. The pinkish sky above the shadow is the antitwilight arch. As the sun sets, the boundary between the reddened (pink) color and the horizon grows until it blends with the darkening night sky. The same thing happens at dawn of course. Look for it, and tell me what you see!

Venus! The first “star” to appear in our sky after sunset was Venus. Through the telescopes its gibbous phase is unmistakable! Its distance from Earth is 1.2 AU (astronomical units).

Mars! I was not expecting to see any features on Mars, since it is so far away and so small. Mars is 1.7 AU from Earth, but only half the diameter of Earth. I was surprised that I could see some dark markings, through a small refractor. When we checked a Mars map for the time of the observation, the large dark feature Syrtis Major was indeed right smack on the central meridian – the imaginary line in the center of the planet facing Earth at that moment.

Saturn! What’s not to love about Saturn! The brownish cloud bands contrasted against the butterscotch hued planetary globe. The slender ring, appearing nearly edge-on, bisected the planet, showing a tiny glimmer of sunlight shining on the north side of the rings. Several moons were visible, though one of the larger ones, Dione, was transiting (crossing in front of) the planet on this night. I spotted Mimas and Enceladus — tiny beacons of light — hovering near the edge of the rings. Titan and Hyperion were on the same side, only further away. Rhea was on the other side. Dione’s shadow marched across the face of the planet for astrophotographers to capture. I didn’t see it visually. Distance from Earth is 9.4 AU right now.

Pluto! This small icy world is 30 AU away from Earth. Once a planet, it is now a dwarf planet. But that doesn’t alter my enjoyment of seeing it through a telescope. For the past few years, Pluto has been marching slowly towards the richest part of our Milky Way galaxy making it a challenging object to confirm in backyard telescopes. Right now it is found skimming the Northern border of M24, the Milky Way Star Cloud. That’s a lot of stars to wade through to find one dwarf planet!

I printed out star charts showing just the few surrounding stars and Pluto, indicating the motion over the evening so I could go back and verify the observation closer to dawn. I also made zoomed out charts, showing larger and larger areas of the region. I had some galactic luck this month! A small open cluster called NGC6603 was nearby to Pluto within the larger M24 open cluster. A few distinctive star patterns separated the dwarf planet from the small star cluster, and I was able to easily starhop and make a positive ID. With Pluto bagged, I was feeling confident about the rest of my planetary to-do list.

Note: From July 4th through the 8th Pluto will pass in front of a dark nebula on the Northwest border of the M24 named B92. This should make the tiny magnitude 14 speck-of-a-former-planet easy to spot.

Ceres, another ex-planet was nearby so I hopped over to have a look at it. Ceres spent half a century after its discovery in 1801 as our 8th planet. Then it was demoted to an asteroid, but its significance was cemented by its designation, 1 Ceres. After many years working the solar system as chief #1 asteroid or minor planet, in 2006 Ceres was promoted to dwarf planethood along with Pluto. Ceres is 1.8 AU from Earth, by the way.

With the dwarf planet observations under my belt, I took a short nap to allow Jupiter, Uranus and Neptune to rise higher in the sky.

Uranus and Jupiter! When two planets are at opposition at nearly the same time they appear to pass each other from our viewing vantage point on Earth. This year we will see Jupiter pass Uranus, then appear to loop backwards–in retrograde–passing near Uranus a second time, then resuming its forward motion with third final close pass. The next time this will happen is 2037, so you might want to aim your binoculars at this pretty pair of planets this year. This is the first pas de deux, so you have many months to view the dance of the two gas giants. Through the telescope, Jupiter, which is 5.1 AU from Earth, looked unusual to me. It was my first look at the planet since the Southern Equatorial Band disappeared. A few months ago, this chunky ruddy band went missing.

Uranus has a beautiful aquamarine color. It has several moons just on the border of visibility through large amateur telescopes. I was able to spot three of the brighter moons of this planet — the ones farthest from the planet’s glow. Titania and Oberon on one side and Ariel on the other. A big ‘scope and good dark and steady skies help to see the faint moons! Uranus is 20 AU from Earth. Try looking up at Jupiter in a dark sky and see if you can spot a blue-green “star” nearby.

Neptune! Neptune sports an azure-blue hue and appears like a tiny disc. It’s nearly 30 AU away near the southern tip of Capricornus. At this time of year, that means waiting until 3 am or later for a view.

Now I had snagged all the planets except Mercury. It would be rising an hour before sunrise at 5:30 am, but the elevation of hills on the SE horizon were difficult to measure. I kept my eyes on the Pleaides star cluster as Mercury would rise directly below the famous cluster. By 4 am, with an hour and a half until sunrise, the sky was already brightening. First, the glorious Milky Way faded until it was nothing but a memory. Then, one by one the constellations disappeared, except for their brightest starry ambassadors. I steadied my binoculars as the Pleiades or “Seven Sisters” disappeared one by one. I kept the remaining Pleiades stars in my binocular view while moved back and forth, scanning the horizon for Mercury. Soon the rays of pending dawn punctuated the horizon, and I worried that I’d miss it as sunrise made the landscape visible once again. I could still see some of the Pleiades, and kept looking for over 45 minutes. Finally, just a few minutes before 5:00 am, a bright beacon appeared on the horizon. It was Mercury! I had seen ten planets in the span of nine hours!

The nine hours passed so quickly. With sunrise comes daylight and the views of the night sky fade from view but not from memory. Join us out in the desert sometime or find a local astronomy club closer to you so you can see these wonders of our solar system for yourself! You really have to see this!

Mojo’s report/astrophotos from the same night

Jane’s June 2010 What’s Up podcast: “A Planetary Necklace”

Mercury Rising A nine planet observing night in 2001.