17 billion Earth-sized planets – you gotta be kidding!

The center of the Milky Way rises high over the domes of the European Southern Observatory in Chile. A new study suggest there could be at least 17 billion Earth-sized planets orbiting stars in our galaxy. The laser beam creates an artificial star to monitor atmospheric turbulence. Data from the “star” is used to adjust the telescope’s mirror to cancel out the blurring effects of the atmosphere. Credit: Yuri Beletsky / ESO

Can you believe the news? It’s estimated that at least one-sixth of the stars in the Milky Galaxy harbor Earth-sized planets. Since our galaxy contains at least 100 billion stars, that means a minimum of 17 billion planets. Next time you look up into the night sky, consider how many worlds your gaze encompasses.

Francois Fressin, of the Harvard-Smithsonian Center for Astrophysics (CfA), presented the study Tuesday in a press conference at a meeting of the American Astronomical Society in Long Beach, Calif. His work is based on a new analysis of data from NASA’s Kepler spacecraft which has been monitoring over 145,000 stars in the direction of the constellations Cygnus and Lyra for the past 22 months.

Illustration of the variety of Earth-sized planets detected by Kepler. Credit: C. Pulliam and D. Aguilar (CfA)

Kepler spots planets by looking for periodic fadings when an extrasolar planet crosses in front of (transits) its host star. Called the transit method, a planet’s size is calculated by measuring precisely how much the star’s light is dimmed. Timing the intervals between repeat transits yields an orbit. As of this week, Kepler has tallied up more than 2,700 potential planets with more than 100 already confirmed.

Through a clever simulation, Fressin and colleagues determined that 90% of Kepler’s candidates are the real ticket, with the remainder false positives. They then extrapolated that figure to the heavens at large and arrived at these amazing statistics:

* 50% of stars have a planet of Earth-sized or larger in a close orbit. That proportion goes up to 70% when larger planets in wider orbits are included.

* Extrapolating the Kepler results with other ongoing surveys and techniques that to date have uncovered 854 exoplanets indicate that all sun-like stars have planets.

Graph showing the fractions of different kinds of planets around Milky Way stars. At least one-sixth of our galaxy’s stars have Earth-sized planets in tight orbits. Credit: F. Fressin, CfA

The team then grouped the planets into these categories: 17 percent of stars have a planet 0.8 -1.25 times the size of Earth in an orbit of 85 days or less. About one-fourth of stars have a super-Earth (1.25 – 2 times the size of Earth) in an orbit of 150 days or less. (Larger planets can be detected at greater distances more easily.) The same fraction of stars has a mini-Neptune (2 – 4 times Earth) in orbits up to 250 days long.

Folks, we’ve got company. 17 billion? Even if 99 percent are either too close or too far from their host suns to support any form of life, that still leaves 17 million open to the possibility. Astronomers predict the best places to find not just Earth-sized planets but versions friendly to life are in the Goldilocks zone, where liquid water can exist without vaporizing before you get to the end of this sentence.

The sweet zone for life has expanded in recent years as scientists have uncovered bacteria completely at home in acid and boiling water. Deinococcus radiodurans, listed in the Guiness Book of World Records as the planet’s toughest bacterium, can survive cold, acid, dehydration, a vacuum and powerful doses of radiation. Yeah! That’s what I love about life.

A selection of planets discovered by Kepler, many of which are similar in size to Earth. Credit: NASA/Kepler Mission/Wendy Stenzel

“Earths and super-Earths aren’t picky. We’re finding them in all kinds of neighborhoods,” says co-author Guillermo Torres of the CfA. And they include not only sun-sized stars but also red dwarfs that are smaller and cooler than the sun. Less common are big Jupiter-sized worlds even though that’s what most ground surveys of exoplanets have found. Kepler’s broad sample shows that only 5 percent of stars are orbited by gas giant planets with periods of 400 days or less.

We all enjoy looking up at night and letting our sense of wonder take us away. The next time you’re out, consider a planetary journey. Pick any star and the chances are 3 out of 4 it’s orbited by an alien world.

Comet C/2012 K5 sprouts tails of wonder to brighten the night

Seen up close by spacecraft, comets resemble asteroids, only they’re made of ice, dust and rock. When near the sun, solar energy causes comet ices to vaporize and form a coma and tail. Comet Tempel 1 is about 4 miles across; Hartley 2, 1.4 miles. Most comets are no bigger than about 15 miles in diameter. Credit: NASA

Comets are changeable by nature. When far from the sun, they’re frozen, inert bodies that look like points of light in large telescopes. No warm, fuzzy outside, no tail.  But once a comet’s orbit takes it “downtown” to the inner solar system, heat from the sun vaporizes dust-laced ices to form a hazy atmosphere around the comet called a coma. Comas can grow up to 60,000 miles or more across or nearly as big as Jupiter. While impressive in size and appearance, they’re extremely rarified and possess little mass.

How a tail develops and grows as a comet approaches and then recedes from the sun along its orbit. Ion tails always point directly away from the sun. Credit: NASA

Being made of nearly nothing, makes it easy for the sun to fashion them into tails by the sun. Radiation pressure – literally the pressure of sunlight – pushes back dust inside the coma to form a yellow-hued dust tail.

Ultraviolet light from the sun ionizes or electrifies atoms and molecules inside the comet’s temporary atmosphere. One of the most common gases found in comets is carbon monoxide. Yep, the same stuff that comes out of your car’s tailpipe. As the sun’s magnetic field washes across the solar system like so many waves rippling a pond, it sweeps ionized carbon monoxide molecules out of the coma to form a second, blue-colored ion tail.

Ion tails always point directly away from the sun much like a wind vane, while dust tails tend to follow the curve of the comet’s orbit. Depending on where the comet is in relation to Earth, tails can appear long and narrow, short and spiky, fan-like or even hide for a time behind the coma.

The changing faces of comet C/2012 K5 from mid-Dec. 2012 through Jan. 6, 2013. The tail originally pointed northwest, then flopped over to the northeast. On the 24th, notice the ion tail (blue) and fainter yellow dust tail. The yellow dust tail displayed a nice curve a few nights ago but is now straightening out. Credit top row (l-r): Michael Jaeger, Gerald Rhemann, Jaeger. Bottom: Jaeger, Rolando Ligustri and Ligustri.

Current bright telescopic comet C/2012 K5 has displayed both types of tails during its travels across the evening sky the past week. Because the comet plunged from directly above the plane of the planets to below it around the time of its closest approach to Earth (Dec 31, 2012), our perspective on it has been changing daily.

The appearance of C/2012 K5′s tail has varied as the comet passed through the plane of the solar system as seen from the moving Earth. Arrows show direction of movements. Credit: JPL/NASA

I’ve seen comets’ tails morph this way and that, but few as quickly as C/2012 K5′s twists and turns. You’ve seen a few pictures of the comet in this blog already, but today I thought I’d put them all together to give you a perspective on the changeable nature of this icy wonder.

Comet C/2012 K5 shown every 2 nights around 8 p.m. CST. The comet slows down in the coming weeks as it distance from Earth continues to increase. Stars shown to mag. 8. Right-click, save and print to use at the telescope. Created with Chris Marriott’s SkyMap software

Sadly, the comet is fading but it remains visible in 7×50 or 10×50 binoculars from a dark sky; through an 8-inch or larger telescope, the coma – along with it bright central nucleus – opens up into beautiful, broad dust tail fanning to the northeast. I’ve included an updated chart to help you find it.

Tomorrow I’ll have some news on another comet, C/2012 S1 ISON, which is expected to put on a spectacular show later this fall.

How to catch an asteroid? Put a bag over it

Artist’s conception of the asteroid-catcher with bag extended ready to grab a 7-meter space rock. Photo: Rick Sternbach / KISS

Why bother with an expensive, potentially dangerous manned mission to an asteroid when you can just tow it to lunar orbit and study it there? That’s the thinking behind a recent proposal by NASA’s Keck Institute for Space Studies (KISS). Researchers there have come up with a plan to launch a spacecraft to a small 7-meter (23-foot) near-Earth asteroid, capture it, de-spin it and then tow the garage-sized rock into lunar orbit, where it could be studied and mined for raw materials at a convenient distance from home. The Keck team points out that 842 lbs. of rocks were returned from the moon during the entire Apollo program, while this mission would bring an approximately 1.1 million-pound kilogram asteroid within Earth’s reach by the year 2026. Total price tag: about 2.6 billion.

The craft would be launched from an Atlas rocket and travel to its target using a solar electric propulsion system similar to the one that propelled NASA’s Dawn spacecraft to the asteroid Vesta and will soon carry it to Ceres. Upon arrival, the probe will first study and characterize the asteroid. Prior to capture, the craft would match the asteroid’s rotation, then, using inflatable arms, extend a large bag around the object. Cinching cables would close the bag. Once secured inside, the probe would fire its thrusters to de-spin both it and the asteroid, and then return to the vicinity of the moon and park itself in lunar orbit.

An example mission that would return near-Earth asteroid 2008 HU4 to lunar orbit. Credit: KISS

Expect the entire mission to take a decade to complete. Escaping the Earth’s gravity using ion propulsion requires between 1.6 to 2.2 years, then 2 years to reach the asteroid and 2-6 years to return depending upon the asteroid’s mass. If we were to start working out the details now, including building the spacecraft, we might just get our asteroid home by the projected 2026 time frame.

Top view of the spacecraft showing instruments and the capture mechanism before being released. Credit: KISS

Assuming that humans will be tooling around in lunar orbit by the 2020s, having a nearby asteroid opens up the possibility for mining. If we choose the right object, not only might there be precious metals available, but more importantly, water. Water can be used for shielding astronauts from dangerous solar radiation and cosmic rays on future missions to other planets. You can also chemically break down water into hydrogen and oxygen to make fuel for your spaceship.

It’s an intriguing idea that on the surface sounds almost as crazy as the sky-crane and tethers used to land the Curiosity rover on Mars last August. But hey, that was a carefully-engineered plan that worked flawlessly, and this may too. Read the full proposal HERE.

Jupiter’s poles crackle with volcano-induced auroras

Both a bar magnet (left) and Earth are surrounded by magnetic fields with north and south poles. Earth’s field is shaped by charged particles – electrons and protons – flowing from the sun called the solar wind. Credit: Andy Washnik (left) and NASA

On Earth the aurora is intimately connected to solar activity. High speed electrons and protons from the sun find their way into the upper atmosphere by following invisible lines of magnetic force that surround our planet much like the those around an old fashioned horseshoe magnet. You can render the invisible visible by placing a magnet on a sheet of paper and sprinkling iron filings around it. Immediately they’ll align themselves in series of arcs defining the magnetic lines of force.

Solar wind particles are a bit like guided missiles. Under the right conditions, they spiral down the field lines and crash into Earth’s atmosphere, temporarily dislodging electrons in oxygen and nitrogen atoms. When the sprung electrons meet up with their parent atoms an instant later, those billions of oxygens and nitrogens emit tiny flashes of green and red light. It’s this sub-microscopic activity that’s behind a spectacular display of northern lights.

Nature often dazzles by numbers. We don’t notice a few snowflakes, but trillions of them can be whipped into a storm powerful enough to stop us in our tracks.

Jupiter’s aurora photographed in ultraviolet light in March 2007 by the Hubble Space Telescope. The bright dot at right is Io’s auroral “footprint” described below. Click to enlarge. Credit: NASA/ESA/J.Clarke

Jupiter also possesses a magnetic field or technically, a magnetosphere, but as you might guess, it’s far larger and more powerful than Earth’s. This is due both to Jupiter’s size and rapid rotation rate of just 10 hours. We can picture planets with magnetospheres as spinning magnets. Spinning a small magnet creates a small electric current but spinning a huge magnet like Jupiter at a rapid speed creates a current of 10 million volts at its north and south poles. Powerful electric fields coupled with the planet’s “animal magnetism” grab hold of any particles in the neighborhood and dash them into Jupiter’s upper atmosphere, where they spark extensive auroras.

Northern and southern lights on seen by Hubble on September 20, 1997. Electrified sulfur and oxygen atoms from Io are primarily responsible for Jupiter’s auroras, but the sun and possibly material in the planet’s high atmosphere also play a role. Click to enlarge. Credit: NASA/ESA/J.Clarke

On Earth, particles from the sun are the chief cause of the aurora, but on Jupiter they play only a small role. The planet relies largely on its moon-sized moon Io, the most volcanically active body in the solar system.

Io is the innermost of the Jupiter’s four brightest moons and orbits the planet in just 1.8 days. Astronomers have mapped more than 300 active volcanoes on this small world that spew lava across the landscape and volcanic gases into outer space at the rate of one ton per second.

Sulfur and oxygen atoms in the expelled gas are electrified (ionized) by Jupiter’s magnetic field and eventually make their way down the field lines headed for the poles. As they crash into molecules in the planet’s atmosphere, their electrons are temporarily stripped off. When the sulfur and oxygen ions eventually slow down, they snatch back their electrons and emit tiny bursts of ultraviolet and X-ray light in the process. Voila – auroras bloom over Jove’s poles!

Like blurry images in a mirror, Io, Ganymede and Europa leave an electrified impression of themselves in Jupiter’s polar aurora in this photo taken in 2000 by Hubble. Io even has a ‘tail’ that sweeps around the top of Jupiter as the planet rotates. Click to enlarge. Credit: NASA/ESA/J. Clarke

Jupiter auroras, which show up best in UV and X-rays, are thousands of times more intense than anything here on Earth. Buried within their curtains and curls are features never seen in earthly auroras. As Jupiter’s magnetic field sweeps past Io, powerful electric currents connect the moon directly with the planet’s magnetic poles. Billions of electrified sulfur and oxygen ions are swept along by the field, slamming into the polar atmosphere to create a set of bright dots or “footprints” of aurora at both poles.

Particles from Io, shown as the glowing red donut around Jupiter, get pulled into the planet’s magnetic field (blue arcs) and slam into the atmosphere to create auroras. The electrical conduits (pink) from Io, Ganymede and Europa lead to their individual “footprints”. Credit: LASP/NASA

Ganymede, the only moon in the moon in the solar system with its own magnetic field, and Europa are also connected to Jupiter’s magnetic field and sport their own polar footprints. While it’s understood how Ganymede can hook up with the planet’s field, it’s less clear with Europa. You need something to conduct electricity like Io’s ions or a magnetic field to make the connection to Jupiter. Maybe we’ll learn the answer come 2016, when the Juno space probe, launched in August 2011, is expected to arrive at Jupiter. One of its mission’s goals is to examine and take close-up photos of the planet’s mighty auroras.

(Note: Thanks to Jan Karon’s question for the inspiration for this blog.)

Meet Rigel in Orion, a star with supernova potential

Both Betelgeuse and Rigel are potential supernova candidates. The view shows the sky facing southeast around 8 p.m. local time in early January.  Maps created with Stellarium

Everybody’s always worried about Betelgeuse in Orion blowing up as a supernova. There’s a good chance that may happen one day, but no need to panic. The star’s too far away to trouble earthlings with its future fireworks. Opposite Betelgeuse and below the winsome triad of stars that form Orion’s Belt, another potential supernova star sparks and sputters on winter nights – Rigel. The name comes from ancient Arabic and refers to the foot or leg of Orion.

Like Betelgeuse, Rigel (RYE-jel) is also a supergiant star but one of a different color and temperature. Astronomers classify it as a blue supergiant with a surface temperature of over 20,000 degrees, twice that of the sun and 3 1/2 times hotter than Betelgeuse.

Rigel, a blue supergiant star, is 18 times more massive than the sun and 74 times its size. Credit: CWitte with minor alterations by Bob King

At a distance of 860 light years, Rigel is big enough and close enough to have its diameter measured directly. As you might guess, it’s huge – 74 times the size of our sun.

Placed where the sun is now, this stellar beast would extend nearly to the orbit of Mercury. From Earth, Rigel would span 35 degrees of sky and shine at a blinding -38 magnitude. We’re talking a powerful sunburn in a minute or two.

Great distance tames Rigel’s true ferocity as a young, energy gobbling star into a pretty blue-white twinkle reminiscent of sunlight on snowflakes. Rigel shines at 0.1 magnitude or about as bright as Capella in Auriga and Vega in Lyra.

Being extremely hot, blue supergiants burn up their energy stores quickly. At the tender age of 10 million years (young for a star), Rigel has already depleted its core of hydrogen fuel and has moved on to burning hydrogen in a surrounding shell.

If put in place of the sun 93 million miles from Earth, Rigel would cover 35 degrees or sky or about twice the area of the constellation Orion.

Helium “ash” created from hydrogen burning will one day ignite and serve as fuel as will progressively heavier elements like oxygen, neon and silicon over time. Rigel will puff up and redden just like Betelgeuse in those far-off days.

Just before a supergiant star blows it has a core made of iron that cannot “burn” to create energy to push back the force of gravity. Gravity takes hold and the star collapses.

Unfortunately, supergiant stars reach the end of the line once all the remaining silicon fuel has undergone nuclear fusion to create a core of iron. Iron requires more energy to fuse than the energy it releases, so it won’t burn like the other elemental fuels. With no burning to push back against the crushing force of gravity in so large a star, the core collapses and sends out shock waves that rip it apart in a supernova explosion.

Rigel is a close double star in a small telescope. Use 100x and up to split it cleanly. Credit: Fresno State University Observatory

When will this happen? Probably millions of years down the road. Since Rigel’s 300 light years farther from Earth than Betelgeuse, we needn’t worry about it either. Instead, our future descendants should prepare for a wondrous light show. Jim Kaler, professor emeritus at the University of Illinois, estimates that Rigel will become as bright as the half-moon when it finally blows up. Picture all that light concentrated in a tiny point of light. We’d easily see our shadows at night by supernova light!

If you have a small telescope 4.5 inches or larger, point it at Rigel some night. It’s one of the finest, if challenging, double stars in the sky. The 7th magnitude companion peaks out from under the glare of the main star a very short distance (9 arc seconds) to its south. On a night with steady air and good seeing, this pair is a beautiful sight.

A comet tale plus pummeling asteroids leave carbon stains on Vesta

Comet C/2012K5 passes near the bright star cluster M36 in the constellation Auriga the Charioteer last night. The comet is fading now but still visible in binoculars from a dark sky. Details: 200mm lens at f/2.8, ISO 800 and 2-minute exp. Photo: Bob King

Last night I attached my camera to a battery-operated mount designed to track the stars. What a comedy. Polar alignment kept slipping, the camera-lens weight was too much for the mount and focusing the telephoto lens proved tedious. All I wanted was a single picture of comet C/2012 K5. In the end, I got a lot of exercise hopping back and forth making adjustments …  and a somewhat serviceable image.

Up around 6 a.m. this weekend? Look south and you’ll see the last quarter moon pass the bright star Spica in Virgo Saturday and then Saturn on Sunday. Created with Stellarium

The comet had faded a bit but was still a fuzzy blotch in binoculars and showed an obvious northeastward-pointing tail at low magnification through the telescope. Although the tail color was too subtle to be seen with the eye, a time exposure reveals the yellow tint caused by sunlight reflecting off dust particles. Heat from the sun vaporizes comet ice, releasing embedded rocks and dust into the tail behind the comet’s head.

Scene from Yellowknife Bay on Mars photographed today Jan. 4, 2013. Credit: NASA/JPL-Caltech with color added by Bob King

Not much news has been reported from the Curiosity rover of late. NASA mission specialists are probably happy they can work in peace out of the media spotlight. Pictures keep pouring in just the same. You can view the most recent set of raw images HERE.

The rover’s been exploring a shallow basin called Yellowknife Bay. It’s one bleak-looking landscape that begs for the introduction of a few saguaro cacti. After finishing up exploration of the bay, scientist plans to spend most of 2013 piloting the rover toward the mission’s primary science destination – the 3-mile-high layered mound at center of Gale Crater center named Mt. Sharp. There the robot will study and sample water-rich clays deposited long ago when Mars was a wetter world.

Most of the dark, carbonaceous material on Vesta can be found on the rims of smaller craters (left) or scattered in their surroundings (right). Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

A recent paper published in the November-December issue of the journal
Icarus describes the dark splotches of carbon-containing materials exposed along the rims of small craters as well as along the edges of the huge impact craters Rheasilvia and Venenaeia on the asteroid Vesta.

NASA’s Dawn mission to Vesta last year took thousands of photos, some of which show dark patches of carbonaceous (car-bon-NAY-shuss) material that matches the dark, carbon-rich mineral fragments found in Vesta meteorites here on Earth.

Dark materials streak Vesta’s Cornelia crater in this three-dimensional image from Dawn. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

“The dark material was most probably delivered during the formation of the older Veneneia basin (large impact crater in Vesta’s southern hemisphere) when a slow impacting asteroid collided with Vesta. Dark material from this two to three billion year old basin was covered up by the impact that Dark material from this two to three billion year old basin was covered up by the impact that subsequently created the Rheasilvia basin,” according to Lucille Le Corre and Vishnu Reddy, lead authors of the study.

In this slice of a Howardite meteorite found in the Sahara Desert, some of the small, dark chips are carbon-rich rocks from an asteroid that collided with Vesta long ago. Howardites and eucrites were blasted from the crust of Vesta by later impacts and arrived on Earth as meteorites. Photo: Bob King

The scientists measured the light from the dark patches on Vesta and discovered they were made of the same material as the dark carbon-rich fragments inside a group of fallen space rocks called eucrites and Howardites.

Asteroids, many of which orbit in the main belt between Mars and Jupiter, come in all flavors. Some are made of bone-dry, rocky materials, others contain clays and water and still others are nearly pure metal. Bashing and smashing into one another they left their marks not only on each other but in the pieces that came (and still come) to Earth.

Read more about the new study HERE.

Close but still so far away – the sun at perihelion

Quadrantid meteor shower Jan. 2-3, 2013

Were you like me and got up this morning only to find the sky still overcast? No meteors for this poor astronomer. I hope some readers fared better.

It always seems to be clear over John Chumack’s home in Dayton, Ohio. Chumack, a long-time amateur astronomer, recorded 52 Quadrantid shower meteors overnight using a low-light video camera. Click the video above to watch it all go by in just 33 seconds.

Earth’s oval or elliptical orbit causes our distance from the sun and orbital speed to vary during a year. This week we’re both closest and moving fastest. Illustration: Bob King

At 10:37 p.m. January 1 this week, Earth passed an annual milestone in its orbit, reaching its closest point to the sun for the year. Astronomers call it perihelion, a Greek-rooted word combining ‘peri’ (close) and ‘helios’ (sun). Earth’s distance from the sun varies over the course of a year because our orbit is not a circle with the sun at the center. Rather it’s an ellipse – like all the other planets’ orbits – with the sun slightly off to one side.

On July 5 this year, Earth will reach its farthest distance from the sun called aphelion (AP-hee-lee-on). The difference from one side of our orbit to the other is only about 3 million miles or 3.3%. While the change in distance affects the amount of heat we receive from the sun, it’s not nearly enough to affect the seasons, which are caused by the 23.5 tilt of our planet’s axis. The tilt of the north pole toward the Sun in June causes summer north of the equator, while summer south of the equator comes six months later when the south pole is facing the Sun.

Difference in the size of the sun when Earth was at aphelion (top) last July and this week at perihelion. It’s very obvious in side-by-side photos but extremely difficult to discern with the naked eye. The difference amounts to just 1.1 minute of arc or 1/30 the diameter of the full moon. Credit: Giorgio Rizzarelli

Because our distance from the sun varies, so does the sun’s size and our planet’s orbital speed. When closest to the sun, Earth moves faster than when farther away, the same way sun-hugging Mercury orbits faster than distant Jupiter. Our average speed is 18.5 miles per second (66,600 mph) through space, but today we’re zipping along 2,160 mph faster than we will come July. I can almost feel the wind in my thinning hair.

The sun is peppered with sunspots in this photo made at  9 a.m. CST today Jan. 3 by the Solar Dynamics Observatory. Sunlight takes 8.2 minutes to arrive at Earth at perihelion and 8.5 minutes at aphelion. Credit: NASA

Giorgio Rizzarelli, a regular reader and commenter on this blog, performed an interesting experiment comparing the size of the sun at aphelion on July 5, 2012 and at perihelion earlier this week. The difference is immediately obvious from his unique perspective.

Giorgio went a step further and measured the difference in diameters to arrive at the Earth’s orbital eccentricity.

Eccentricity or ‘e’ refers to how stretched out a planet’s orbit is compared to a perfect circle. With a circle defined as e = 0, Rizzarelli calculated an ‘e’ of  0.017 (nearly circular but not quite) for Earth’s orbit, in excellent agreement with the published figure of 0.0167. (see calculation below). Amazing what you can do with a camera from your own backyard.

“The disc in lower photo is 3.4% bigger than in the upper, so (dividing by 2) 1.7% bigger than average. Hence Earth today is 1.7% closer to the Sun than average. This defines the approximately eccentricity, (which is) 1.7% or 0.017.” – Giorgio Rizzarelli

Bundle up for tonight’s Quadrantid meteor shower; K5 comet update

The Quadrantid radiant, or point in the sky from the meteor shower originates is found below the handle of the Big Dipper. I’ve shown the sky looking northeast around 2 a.m. Later that morning, the radiant will be high in the northern sky. Created with Stellarium

Yes Bobby, there is life after the Geminids. Last month’s meteor shower was arguably the best of 2012, but more are on the way. We start the year with a shower that originates from one of astronomy’s extinct constellation, Quadrans Muralis.

Although defunct, the group of dim stars was around long enough in the late 1700s to lend its name to the Quadrantid meteor shower.

The Quadrantids are reliable but forever a tease. Unlike most showers, which typically toss meteors our way up to several days before and after maximum, the Quads’ activity is limited to a span of 6 hours centered on the peak. That peak can bring a blast of up to 100 meteors per hour, but after that, the show’s pretty much over.

Quadrantid meteor on Jan. 4, 2011. Details: ISO 400, 30-second exposure and 8mm fisheye lens. Credit: John Chumack

This year’s maximum occurs at 13:00 Greenwich time or 7 a.m. CST tomorrow morning Jan. 3 for the Midwest. That’s well into morning twilight for the eastern half of the U.S. but still close enough to peak to make the shower worth watching.

Observers living in the western U.S. and across Hawaii and east Asia are favored because their skies will be dark for a longer time centered around the expected time of maximum.

No matter where you are, light from the waning gibbous moon will compromise meteor counts.

To watch the Quadrantids, set your alarm for tomorrow morning between 2 and 6 a.m. and face east or north away from the bright moon. Your eyes will adapt better to the darkness in those directions, letting you see more (and fainter) meteors. For mainland U.S. observers, the closer to dawn you’re out the better. I plan on rising about 5 should the sky clear.

Peter Jenniskens, senior research scientist at NASA’s SETI Institute, traces the Quads origin to the asteroid 2003EH1, a likely extinct comet. So yes, tomorrow morning we’ll be watching the remains of an extinct comet radiate from an extinct constellation. What could be more apropos?

Comet C/2012 K5 Monday evening Dec. 31, 2012 from Austria. Compare its appearance to the photo taken below in mid-December. The comet’s tail points northeast. Credit: Michael Jaeger

Did someone say comets? Rarely have I seen a comet’s appearance change so rapidly. C/2012 K5, the comet we visited in a blog three days ago, went from compact and bright to big and foggy in just a week. On Christmas morning, C/2012 K5 sported a small, bright head and a striking tail pointing northwest. Two nights ago I was in for a shock when I observed it again. The head had swelled into a big, hazy bulb with a bright, star-like center followed by a wide, much fainter, tube-like tail angled northeast.

There are at least two reasons for these radical changes – the comet was closer by a few million miles – 27 million on Monday night vs. 30 million on the 25th – and our viewing perspective is changing rapidly as C/2012 K5 dives through the plane of the solar system on about Jan. 6.

C/2012 K5 on Dec. 16, 2012 shows a small head and well-defined bright tail pointing northwest. Credit: Michael Jaeger

The comet follows a steeply inclined orbit, looping high above and plunging deep below the plane of the planets and sun. During the first half of December  skywatchers looked up above the Earth and solar system plane to see it. As C/2012 K5 plunges southward, we’re now seeing the comet more from the side.

Since a comet’s tail always points away from the sun, these changing perspectives – a combination of both the comet’s and Earth’s orbital motions – will continue to alter the tail’s direction and appearance in the coming weeks.

C/2012 K5 orbit is steeply inclined to the plane of the solar system, which is why it’s been visible in the far northern sky of late. Now the comet’s rapidly moving southward as it plunges through the plane. Credit: NASA/JPL

Despite the changes, C/2012 K5 remains bright enough to see easily in 8×40 binoculars from a dark sky. It’s a speedy beast too, leaping along at the rate of about 4 degrees per day or 1/3 the moon’s diameter per hour. When the bright core or nucleus happened to pass near a star Monday night, I could see it move in just 15 seconds at 64x in my scope.

Comets and meteor showers keep an amateur astronomer’s life interesting.

First asteroid Ceres discovered New Year’s night 212 years ago

Giuseppe Piazzi

Happy New Year! May you have as pleasant a start to the new year as Giuseppe Piazzi did on January 1, 1801. That night the Italian monk and amateur astronomer was at work in his observatory on the island of Sicily compiling a catalog of the stars in the constellation Taurus. Using an earlier catalog as his reference, he noticed a star that was out of place and not included among its pages. The next night he returned to check it and to his surprise, the star had moved!

Piazzi suspected it might be a “new star” but still cautious, he observed it on a third and even a fourth night – noting it had moved the same distance each night – before sending news of the discovery by letter to colleagues at other European observatories.

He initially reported the object as a comet, similar to what William Herschel did when he discovered Uranus back in 1781, but added in a letter to an astronomical friend:

“I have announced the star as a comet. But the fact that the star is not accompanied by any nebulosity (haziness) and that its movement is very slow and rather uniform has caused me many times to seriously consider that perhaps it might be something better than a comet. I would be very careful, however, about making this conjecture public.”

Front Cover of Piazzi’s book on the discovery of what we now know is the dwarf planet Ceres. Astronomers thought it was the planet hypothesized to orbit between Mars and Jupiter.

Piazzi wrote a similar letter to Johann Bode, director of the Berlin Observatory. Because Napoleon’s invasion of Italy disrupted communications at the time, Bode didn’t get the letter until March 20, nearly 3 months later. But one look at the figures convinced him Piazzi had found something brand new.

Could it be the missing planet astronomers had hypothesized must lie between the vast and apparently empty gap between Jupiter and Mars?

Unfortunately, Piazzi had been the only person to observe the new object before it’s conjunction with the sun and disappearance in the solar glare. When predicted to reappear in the morning sky several months later, astronomers were ready with their telescopes, but no one could find the object.

Because of bad weather and illness, Piazzi hadn’t made enough observations earlier that year to allow astronomers of the day to establish an orbit. Without an orbit, predicting the “planet’s” position after solar conjunction was impossible.

A young German mathematician named Carl Friedrich Gauss became aware of the problem and worked for months to produced a new, more accurate method of orbit determination. He applied it to Piazzi’s handful of positions and confidently predicted where to look for the new “planet” in December 1801. And wouldn’t you know it, one Baron Franz Xaver von Zach , a Hungarian astronomer, found it within 1/2 of a degree of Gauss’ predicted position on December 31, 1801, almost exactly one year after Piazzi’s discovery.

Zach was famous for organizing a group of astronomers nicknamed the Celestial Police, whose mission was to find the putative planet predicted by Bode’s Law to lie between Jupiter and Mars.

Hubble Space Telescope photos of Ceres. At 580 miles in diameter, it’s the largest asteroid (dwarf planet) in the Main Belt between Mars and Jupiter. NASA’s Dawn spacecraft will study it up close beginning in 2015. Credit: NASA/ESA

Piazzi named the new object Ceres Ferdinandea, after the Roman goddess of agriculture and grain crops and King Ferdinand IV of Naples and Sicily. The Ferdinand was later dropped (thank you!) leaving us with Ceres.

Ceres became the first – and largest – of the asteroids, a collection of small, rocky bodies orbiting in a broad belt between Mars and Jupiter. Stirred up by Jupiter’s gravity, they never glommed together to form a planet.

Ceres was recently reclassified as as a dwarf planet, joining erstwhile-planet Pluto and icy asteroids Eris, Makemake and Haumea. Three more asteroids – Pallas, Juno and Vesta – were discovered in the next few years. In the early 19th century, it was believed these objects were actual planets; you’ll see them referred to as such in books of the time.

As the discovery pace quickened in the 1840s and beyond, astronomers soon realized there were too many to be considered in the same class as planets. Instead they named them asteroids from the Latin aster or “star”, referring to their appearance in the telescope. It’s estimated there are between 1.1 and 1.9 million asteroids in the main belt 0.6 miles across and larger and millions more smaller ones. While these numbers sound impressive, if you could crunch all the asteroids in the main belt together they’d only form a sphere less than half the size of the moon!

Ceres’s story continues into the present. After departing Vesta this fall, NASA’s Dawn space probe will visit the dwarf planet for a year starting sometime in early 2015. Based on density estimates, astronomers suspect it harbors water beneath its crust. The Hubble picture reveals a pink surface and mysterious white spot.

Piazzi, we’ve only begun to know the world you found that New Year’s night.

Make a toast to the New Year’s Eve midnight sky

The Winter Triangle will greet your gaze at midnight tonight high in the south. To find your directions, face slightly to the right of the sunset direction – that’s west. Then stick out your right arm to point north, your left arm points south and east is at your back. Maps created with Stellarium

Most of us will be wandering around at midnight tonight, right? Why not peek outside to see what’s happening in the sky at a time when we’re normally asleep?

Jupiter beams brightly high in the southwestern sky, but it’s Orion and Sirius that might catch your eye first. During the early evening Orion reclines in the east; by midnight he’s standing straight up staring you in the face. At his lower left, romping and ready for the hunt, is the Great Dog, Canis Major. Sirius, the most brilliant star in the heavens, sparkles from his collar. Yipping for attention well above Orion is the little chihuahua dog Canis Minor with its luminary Procyon. Connect the little Dog Star with Sirius and Orion’s ruby Betelgeuse to form the Winter Triangle.

The moon visits Leo’s brightest star Regulus tonight. Alphard, Hydra’s “alpha” star, shines meekly to the lower right of the moon.

Off to the east, the waning gibbous moon in Cancer isn’t far from Regulus, Leo the Lion’s brightest star. Direct your gaze two outstretched fists to the lower right of the moon to catch sight of Alphard in Hydra the Water Snake, a transitional winter-spring constellation. Even Leo carries a whiff of spring as it rides up in the east – come April, it will  rule the southern sky at nightfall.

In the north, we see that the Big Dipper, which has been slumbering away along the northern horizon all fall, has finally returned to the tray-table upright position in the northeast. The Dipper is the brightest portion of Ursa Major the Great Bear and always strikes me as a little funny at this hour standing on his tail (handle). The ancients, who created the constellations, obviously loved animals – and perhaps a good circus act – as much as we do.

Have you missed the Big Dipper? Go out at midnight, look to the north and you’ll see your old friend has returned.

Queen Cassiopeia belongs to the northern sky but also partakes of the west at this hour. The W-shaped constellation stands on its end opposite the Big Dipper. Between them lies the always reliable North Star also known as Polaris. Like that person you can always count on being there for you, we know where to find our Polaris.

The western sky at midnight is filled with departing constellations of fall including Aries the Ram and Andromeda.

A line of stars angling northwestward is the brightest part of Andromeda the Chained Princess. She dominated the sky overhead sky earlier in the evening, but by the midnight hour the princess repairs to her western bed. Higher up you’ll see the familiar Pleiades star cluster and the curliques of stars forming the constellation Perseus the Hero.

Raise your glass tonight in a toast to the good old stars at the start of a brand new year.

Happy New Year everyone!