Sun vs. ISON

Tomorrow, Thursday the 28th, as we prepare for Thanksgiving (and Hanukkah) a cosmic drama is set to unfold. For months, astronomers have been observing Comet ISON approach the sun, now estimated to be less than a mile wide, wondering whether the comet will survive its close encounter and re-emerge from behind the sun to become visible to the naked eye through December. You can follow this drama on line. Between 12noon and 2.30 pm (CST) tomorrow, NASA will host a Google Hangout while all eyes on the sun will watch Comet ISON make its plunge, passing perilously close (within 730,000 miles) above the sun’s surface and accelerating to 150,000 mph. Will it survive? Break up? Evaporate? Join the Google hangout to keep track of ISON’s progress!

There is already one recent video posted of ISON coming into view of one of the extended-corona imagers from NASA’s STEREO spacecraft, seen on the STEREO website.
Discernible for most of November in binoculars, ISON is probably the most scrutinized comet ever by NASA, but from the beginning of its discovery it’s also been one of the most confusing, frustrating and unpredictable objects to observe over time. I’m still betting on ISON becoming the comet of a lifetime.

This Morning’s Comet

For the first time in nearly a week, this morning’s pre-dawn sky was clear and so I stepped outside, away from street lights and spotted Comet ISON.  I used a pair of 10 x 50 binoculars, but there it was – a faint, diffused comet with a stubbly tail just above the eastern horizon tree line.  The bright gibbous moon overhead didn’t help with observing, but it was still worth getting up for.  And since I was already outside, I turned my binoculars on Jupiter and Mars, then the Orion Nebula, the Hyades star cluster and again back to Comet ISON just before dawn was braking. 

There’s been a lot of mixed reviews recently about Comet ISON; how it was becoming a naked-eye object and then how it might not survive intact after its closest approach to the sun, or perihelion, on the 28th (Thanksgiving).  If the comet breaks up as some predict it will, then this weekend, which is suppose to be clear, might be your last chance to see the comet.  But then again, it still could become the comet of the decade late December.  Fingers crossed.  

Pale Blue Dot

NASA just released a panoramic image of Saturn and some of its closest moons, but it also includes the tiny, blue dot we call home – planet Earth, some 900 million miles away.  Taken by the Cassini probe now orbiting Saturn, the image also captures our companion worlds Venus and Mars.  The panorama was pieced together from natural-color photographs taken in July.

Each pixel in the photograph represents about 45 miles. Seven out of Saturn’s 53 known moons are visible in their planet’s seven rings. There’s Prometheus, Pandora, Janus and Epimetheus near Saturn’s slim F ring. There’s Enceladus in the bright blue E ring. There’s Tethys, a yellow bulb, and Mimas, just a crescent, wedged between rings.

Cassini at Saturn 1

Venus is located to Saturn’s upper left, which is seen as a bright, white spot.  Mars, a pale red dot, is above and to the left of Venus. There are 809 stars captured by Cassini’s lens in this image.  And we Earthlings are on the blue dot at Saturn’s lower right.

This cosmic portrait had been planned for months and on July 19, NASA announced that all the conditions were right for such a picture, including that on this date, Saturn completely eclipsed the sun, allowing Cassini’s sensors to image this portrait.  The cosmic photo is a composite of 141 images taken over four hours, selected out of 343 images total. The photograph was then digitally enhanced to pull from the blackness Venus, Mars, Earth, Saturn’s moons, and all the stars in the frame. Most of the objects in the photograph, including Earth, were brightened by 8 times relative to Saturn; some of the stars were brightened by as much as 16 times.

This was also the first time that humans were told in advance that Earth was being put before a camera. So, in what was called NASA’s “Wave at Saturn” campaign, the Cassini’s Imaging team asked us all to turn out for the July 19 picture day to wave and smile for the camera in the cosmos.

Cassini at Saturn 2

Backyard Astronomy

Clear November night skies offer several good reasons for bundling up and spending some time stargazing, even when it’s from your backyard. For early morning risers, Comet ISON should reach naked eye brightness toward the end of this month, but until then its visible in small telescopes low in the east-southeast sky before sunrise. ISON passes closest to the Sun on November 28 and is expected to become as bright as the planet Venus.

ISONNov20If you’re having trouble seeing ISON, try looking for the ring planet Saturn, along with the closest planet to the Sun – Mercury, near the horizon. Saturn is a pale, yellowish object that will rise higher in the early morning sky beginning in December and a sight not to be missed if you’re out before sunrise. But the solar system’s largest planet, Jupiter, is a much easier object to locate primarily because it,s big and bright – visible in the east shortly after 8 pm. and high overhead by midnight; it’s the brightest object in the eastern sky. Even throiugh a pair of binoculars, you should be able to observe its four brightest moons and from night to night notice that these tiny moons change position as they orbit Jupiter.
A must see object in the eastern evening fall and winter night sky is the Pleiades star cluster, easily visible even in an urban setting without any optical aid. The cluster is located in the constellation Taurus the Bull and is best when seen through a pair of binoculars.

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Fall and early winter skies are usually clear and less humid, making backyard observing very rewarding, even without binoculars.

Lunar Eclipse…Sort Of.

Lunar Eclipse

Lunar Eclipse (Photo credit: Peter Neish)

On Friday, 18 October, this month’s full moon occurs and with it, weather permitting, we’ll see a penumbral lunar eclipse – so called because only the full moon passes through the outer bright rim of the Earth’s shadow, or penumbra, as it rises in the east at sunset. Unlike total eclipses, in which Earth’s umbra — the central region of its shadow — darkens the moon entirely, a penumbral lunar eclipse involves only a slight dimming. Still, sky watchers should expect to see a much more subtle sight with a maximum shadowing on the lower half of the full moon occurring at 6.50 pm. CDT. Sky watchers should start observing the moon at sunset. Best place for observing this Friday’s eclipse is in Europe, Africa and the Middle East where it will be visible as a total eclipse. From Baton Rouge however, this penumbral eclipse should last about 45-minutes. The next lunar eclipse to be seen from our area will be Tuesday, 15 April 2014. Mark your calendars!

What’s Astronomy Anyway?

So What is Astronomy?

I’ve been asked this question a lot over the years and I usually reply by saying the science of astronomy is more than learning a whole lot about stars. Astronomy actually comprises many different ways to look at the universe. At its simplest, astronomy is observation. You go out each night, look up at the sky and notice the star patterns, the planets, and the Moon… (if visible). But, astronomy also helps us understand how the objects we see formed. It answers questions such as “How are stars formed?” “How do stars end?” “Where do planets come from?” “How far away are the objects we see?” “How do galaxies form?” “When did it all begin?”

Astronomy is an ancient science – perhaps the first one humans invented. The names of stars come to us from ancient history. The constellations are ones that people have seen for thousands of years, and each culture made up stories about those star patterns.

To study faraway objects, people invented telescopes that extend our vision so that we can see dim, distant objects. You can start extending your own vision simply by using a pair of binoculars in your own backyard. They magnify the view and let you see things you can’t quite make out with your naked eye. If you want to see farther out to space, you need a telescope. Or, you can browse the Web to see what professional astronomers are finding out at the limits of the observable universe.

Astronomy is a very visual science and one that everyone can enjoy, even without knowing much of the science. So how do you “do astronomy”? The first step is simply to go out and look up. If you have a star chart, a pair of binoculars, or even an astronomy app on your smart phone you have at your fingertips incredibly powerful tools to help you explore on your own. So get out there and do some astronomy.

Traveling Companions

Comet C/2012 S1 (ISON) wasn’t alone in the pre-dawn skies above Slooh’s Canary Islands Observatory recently. Accompanying Comet ISON was the huge asteroid “433 Eros” – the second largest Near-Earth Asteroid. Eros was traveling in roughly the same direction as ISON, but at a slightly faster apparent speed, and can be seen above and to the right of the comet. Slooh Members watched the images come in from the observatory in real-time, and immediately spotted the second object moving between successive images.

This time-lapse of five images, created recently by Paul Cox using Slooh’s online robotic telescopes, shows the two objects as they speed through the inner solar system. You can check out updates on Comet ISON and other related online robotic telescope shows at slooh.com.

Umbrellas and Planets

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Artist’s conception of sulfuric acid rain on Venus.

Bringing an umbrella in case of rain may have a different meaning depending upon the planet you’re on.  Our umbrellas protect us from the rain showers here on Earth, but wouldn’t hold up very well if caught in a downpour of sulfuric acid rain on the planet Venus. Atmospheres surrounding different planets produce a wide variety of different weather patterns and atmospheric conditions, most of which are very hostile to human life.  On Earth, atmospheric or air pressure is the force exerted on the Earth’s surface by the weight of the air above the surface. This is an important factor in determining weather patterns and especially when it rains.  Our atmosphere contains water vapor and when the atmosphere pressure is low, clouds usually form and turn the water vapor into liquid water we call rain.  On Venus however, the atmosphere contains opaque clouds made of sulfuric acid, so when it rains there it’s acid rain.

Further out in the solar system, the eighth and last planet in the solar system, Neptune has an atmosphere dominated by ices – methane and ammonia. But even with a chill in the air, Neptune still manages to host some of the most extreme and violent weather in the solar system.  But most amazingly is that as a result of Neptune’s high temperatures and pressure, its methane gas can be turned into diamond.  If liquid methane is squeezed to several hundred thousand times under extreme heat, diamond is produced and that’s what the weather conditions on Neptune are like.  So if diamonds appear in Neptune’s atmosphere, they fall like raindrops or hailstones toward the center of the planet.

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Colorized image captured by Cassini of methane lakes on Titan.

Other than Earth, the only known world to have liquid lakes is the planet Saturn’s largest moon Titan, the second largest moon in the solar system.  Titan’s cloudy atmosphere is believed to be made of liquid methane, but the droplets of liquid methane in the rain clouds are 1,000 times larger than the rain drops here on Earth. NASA’s Cassini spacecraft still orbiting the Saturnian system has detected liquid methane lakes and rivers on Titan.

blue_glass_rain_exoplanet

Artist’s conception of HD 189733b the exoplanet where it rains glass.

Atmospheres and weather conditions are not just confined to worlds of our solar system.  Numerous planets orbiting other stars have been discovered and many of these are known to have atmospheres.  Called exoplanets, these worlds range in sizes and distances from their parent sun.  One such exoplanet, the size of Jupiter, is named HD 189733b and orbits a star 63 light years from us.  Telescopic studies of this planet’s atmosphere imply that it contains significant amounts of water vapor and silicate particles resulting in a beep blue colored atmosphere. Because of this atmospheric mixture, when it rains on HD 189733b it comes down as glass particles.  My favorite exoplanet with bizarre-like weather conditions is a far off world known as OGLE-TR-56b, another Jupiter sized planet.  Intriguingly, the temperature of OGLE-TR-56b’s upper atmosphere is theoretically just right to form clouds, not of water vapor, but of iron atoms. Although unconfirmed, OGLE-TR-56b should experience exotic iron drops, thanks to strong heating from its nearby star.

Night Sky Objects to Find this Weekend!

Take advantage of the Labor Day weekend to observe a number of early morning celestial objects. Beginning early September, Comet ISON is low in the east before dawn in the constellation Cancer the Crab. Right now however, you’ll need good size telescope to observe the comet, which appears as a soft, fuzzy glow, but even without a telescope there’s a pair of very visible planets low in the eastern sky just before sunrise. Near the horizon is Mars – bright orange in color, while brillant Jupiter shines just above Mars. And while you’re at it, look for a very pretty compact star cluster, known as the Beehive star cluster, nearby Mars. Observing the morning sky won’t be disappointing – all good reasons for getting up early, early in September.