Jane Houston Jones » Venus

Venus kissed the moon – a daytime occultation of Venus

jane — Sat, 18 Aug 2012 21:41:26 +0000

going

gone!

Venus reappears!

If you were up before sunrise on Monday, August 13th, 2012 you might have seen a very bright “star” next to the moon. As dawn turned to daylight, you could still see that star, or rather, that planet in the daytime snuggled up to the crescent moon.

That planet was Venus, and the moon was about to pass directly in front of it as seen from our vantage point on Earth. An occultation occurs when a solar system body passes in front of a more distant one or a star. Each one is only visible from a certain part of Earth. This occultation of Venus by the moon was only visible over northern Asia and Japan at night and over North America during the daytime.

I set an alarm to remind myself to step outside at about noon on Monday. It was a challenge to find the slender crescent moon, but I had a great view, shielded from the sun by the tall wall of my office building. The shadow helped by boosting the viewing contrast a little, too!

I had no difficulty seeing Venus naked-eye. And for about an hour I held court on the steps to JPL’s famed Space Flight Operations Facility or SFOF for short, and showed a daytime planet to several dozen of my colleagues. At about 1:30 p.m. PDT the moon passed in front of Venus after inching closer for over a half hour.

I was reminded of folksinger Christine Lavin’s lovely song Venus Kissed the Moon from her 1990 album Attainable Love. The lyrics go like this:

Venus kissed the Moon tonight
We watched her in the Sky
She’s been flirtin’ with him for centuries
Too bad he’s so shy
He’s waxing
He’s waning
You don’t see Venus complaining
She’ll steal a kiss whenever she can
Not ’till 2031
Will this happen again

There have actually been several Venus/Moon occultations since Christine wrote this song, but that doesn’t matter. I hummed her sweet song, and watched Venus flirt closer and closer to the moon. I’m listening to it as I write these words, too!

My friend Akkana Peck wrote “If you’ve never seen a Venus occultation before, you’ll be amazed at the difference between the brightness of Venus and the dimness of the moon’s limb. We think of the moon as bright, but it’s actually dark grey, about the same albedo (reflectivity) as asphalt; whereas Venus is covered with brightly reflective clouds.” See Akkana’s images of the Venus occultation and her blog here.

I snapped a few pictures with my hand-held Canon PowerShot SX260 HS with its nifty 20x zoom. I zoomed nearly all the way out for these images.

The next opportunity to see a lunar occultation of Venus from North and Central America will be on December 7, 2015. From Los Angeles, we’ll get to see this event from 7:30 am to 11:30 am.

I’m so glad we don’t have to wait until 2031 to see Venus kiss the moon, Christine!

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 warm-up act for the Perseids

jane — Wed, 11 Aug 2010 06:22:56 +0000

See the moon and planets low in the west August 12, courtesy NASA/JPL-Caltech

The view from Earth - the planetary lineup in orbital perspective courtesy NASA's Solar System Simulator, courtesy NASA/JPL-Caltech

Mars and moon imaged same day with same equipment (in 2005) courtesy Jim Keen

A trio of planets, without the moon August 7, 2010, courtesy Morris Jones

Are you eager to see the annual Perseids on Thursday night? You’ll have to wait until after 10:00 p.m. local time to see them, so why not pass the time until showtime by viewing the planets right from your doorstep? Step outside for the planetary warm-up act.

All you have to do is look towards the west as soon as the sun sets. Bright Venus is the first to appear. It’s really bright, and you can’t miss it! Now, hold your clenched fist up to the sky covering Venus. To the right of Venus, about 1/2 of a clenched fist away is a second planet. That’s Saturn. And to the upper left of Venus is another planet… That’s Mars.

But wait, there’s more! Look below Venus for the slender crescent moon. If you don’t see the moon, look again Friday night – it will be a larger crescent to the left of Venus a day later.

Though the three planets appear together in our line-of-sight they are really far apart from each other and from us on Earth. Mars is about 300 million km (186 million miles) from Earth, while Venus is 112 million km/70 million miles distant. Saturn? It’s 1,535 million km/954 million miles from Earth right now. The moon? 363 thousand km, or only 225 thousand miles away. It’s fun to compare the size of the moon and Mars, especially if you received that annual email (which incorrectly) states that Mars will be as big as the moon this month. Do the math. It’s impossible!

The Solar System Simulator is a great public resource for geeks. You can see any planet or spacecraft from any vantage point on any date you select. I picked August 12th to show the view of the planets and moon from Earth.

I hope you can sense the three-dimensional orbits of nearby Venus, far-away Mars and distant Saturn. Have some fun with it! Every day the Cassini Mission website shows a view of Saturn from Earth, from Cassini, and right now Enceladus, as we close in on a flyby of that exciting moon later this week.

In this image of the moon and Mars, Jim Keen made a “true-to-life” size comparison. He made a “blended” image of the Moon and Mars back in July 2005. He recalls, “I had set up my telescope in my backyard and stuck a camera on the back of it. I took separate images of the Moon and Mars – both of which were “up”, but in separate areas of the sky – and later combined the two images to get one, showing the actual size difference using the same equipment, same camera, same magnification, and taken within a few minutes of each other.”

Jim’s image shows the apparent size of the moon and Mars really nicely! If he took the same image this month, Mars would appear super tiny! In the 2005 image Mars was about 50 million miles from Earth, and today it is 186 million miles away.

The final image shows the trio of planets imaged Saturday night August 7th by my hubby, Morris (aka Mojo) Jones. Click on the image to see the two fainter planets above Venus. He posted several images in his blog post called Sky full of planets and lightning. It’s really worth a read! The lightning was amazing Saturday night!

I hope this little planetary warm up act will whet your appetite for more sky watching this week. The Perseids will be a real spectacle, especially if you can get away from the city lights. I’ve pretty much decided to head out to the Mojave desert and see the star show from Amboy Crater. Clear Skies everyone, and happy solar system observing to you all!

California Clear Sky Chart Black dots indicate the darkest observing areas. Amboy Crater, on the southern border of Mojave National Preserve is the closest “black dot” dark observing area and will require a drive of over 200 miles for Thursday’s Perseids.

NASA’s Solar System Simulator Check out where the Voyagers are right now!

My Mars in August website, updated each year since 2005.

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.

Chasing Galileo – Jupiter and the four Galilean satellites

jane — Fri, 12 Jun 2009 01:12:33 +0000

Galileo's drawing

my drawing

my sketch of Jupiter's rotation

Galileo published his observations in Sidereus Nuncius in March 1610: “On the 7th day of January in the present year, 1610, in the first hour of the following night, when I was viewing the constellations of the heavons through a telescope, the planet Jupiter presented itself to my view, and as I had prepared for myself a very excellent instrument, I noticed a circumstance which I had never been able to notice before, namely that three little stars, small but very bright, were near the planet…When on January 8th, led by some fatality, I turned again to look at the same part of the heavens, I found a very different state of things, for there were three little stars all west of Jupiter, and nearer together than on the previous night.”

“I therefore concluded, and decided unhesitatingly, that there are three stars in the heavens moving about Jupiter, as Venus and Mercury around the Sun; which was at length established as clear as daylight by numerous other subsequent observations. These observations also established that there are not only three, but four, erratic sidereal bodies performing their revolutions around Jupiter.”

Every amateur or accidental astronomer who first views Jupiter and its lineup of moons, is amazed at the view. Galileo’s 1610 discovery of these four moons orbiting Jupiter changed history. Looking at the Jovian moons through a small telescope, while trying to imagine Galileo’s first observations, takes my breath away!

A page from Sidereus Nuncius: 1610

First page of my observing log: 1989

My first sketches of the rotation of the four Galilean satellites: 1989