September 2016: Skies Over Crestone

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Spinning Black Hole Spewing Forth Radiation (Artist's rendition, NASA).

Spinning Black Hole Spewing Forth Radiation (Artist’s rendition, NASA).by Kim Malville

Skies-Titan-artist-rendering

Artist’s depiction of a river on Titan. by Carlos Oliveira

Radar image of a river on Titan.

Radar image of a river on Titan. NASA

Mountain waves over Venus.

Mountain waves over Venus. NASA

The first two weeks of September lie in the current eclipse season. There will be an annular solar eclipse visible in Africa on September 1 and then two weeks later there will be a lunar eclipse visible practically everywhere on the earth but the Americas. But, despair not. Next summer on August 21 we shall have a marvelous total eclipse in North America, lasting over 2 minutes in Wyoming, for instance. This month we can see Venus in the evening soon after sunset. Saturn and Mars are brilliant objects in the southwestern sky in the constellation of Scorpius.

September 2-4: Watch the slender crescent moon in the west. On the second a beautiful tiny crescent will be close to Jupiter and below Venus above the horizon some 20 minutes after sunset. The next night it will have moved above and to the right of Venus. On September 4 the moon will be above the bright star Spica.

September 8-9: The half moon will be moving eastward above Saturn and Mars. Below Saturn will be red Antares. Note how it twinkles, unlike the two planets.

September 22: Autumnal equinox occurs at 8:21am when the sun crosses the celestial equator.

Venus, the sad victim of global warming

Venus may have been habitable early in its history. It once held a shallow ocean, which evaporated because of the planet’s close proximity to the sun. During perhaps two billion years, the haze due to water vapor resulted in a climate a little cooler than that of the earth right now, not unlike foggy San Francisco. However, that water vapor eventually led to a greenhouse temperature rise that destroyed the oceans. Without an ocean to absorb carbon dioxide, that greenhouse gas built up in the atmosphere making it the hottest planet in the solar system, with an average surface temperature of 860°F. Although its original atmosphere may have been similar to that of the earth, today its atmosphere is made up almost completely of carbon dioxide. Whatever life that may have formed in its warm oceans two billion years ago was boiled alive, like the unfortunate frog in a pan of warming water.

Today, its atmosphere has bizarre weather patterns that are similar to some on the earth, in fact, similar to some that we experience in the Front Range. Winds blowing over our mountains set up regular wave patterns in our clouds. Hot winds on Venus that blow across Aphrodite Terra, a 15,000-foot mountain range located near Venus’ equator, rise high up in its atmosphere and produce striking patterns, which are related to the mountain waves that we often see above Boulder, laid out in parallel lines, like the white keys of a piano.

Singing black holes

I have heard the mermaids singing, each to each./I do not think that they will sing to me.

-T. S. Eliot, The Love Song of J. Alfred Prufrock

The frenzied feeding of gigantic black holes fills the universe with powerful X-rays, creating an ever-present background of cosmic music. Although this cacophonous choir singing in the language of high-energy x-rays has been heard for some time, the individual singers have remained obscure.

An instrument aboard the Chandra satellite, known as the Nuclear Spectroscopic Telescope Array, (NuSTAR) is beginning to identify the individual singing black holes that had previously been hidden behind thick clouds of gas and dust, like x-rays can penetrate skin and flesh to reveal bones. For the first time we now have sharp images of many of these black holes.  They pull in huge amounts of gas and dust, some of which is heated and accelerated close to the speed of light, producing powerful X-rays.

We can’t see the black hole itself, but we can see the x-rays produced just beyond its edge. And we can see the reflection of those x-rays in the disk of gas and dust that orbits the black hole, as shown in the figure.  We have hundreds of billions of galaxies in our universe and most contain supermassive black holes at their centers, which sing “each to each,” and now they sing to us.

Titan: Saturn’s greatest moon

Much like the water that carved Earth’s Grand Canyon over millions of years, liquid methane has cut a network of canyons on Saturn’s moon of Titan, a new study of radar images captured by NASA’s Cassini spacecraft has revealed.

Titan is the largest moon of Saturn, one and a half times larger than our moon, with a surface temperature of -292°F. A most intriguing recent discovery of radar images is a glint, a reflection of dim sunlight, coming from inside some deep canyons. Liquid methane lies within them, sculpting them now as it has for millions of years. These canyons lead to a sea the size of Lake Superior, a vast reservoir of methane with a depth of 600 feet.

While water once carved canyons on Mars, flowing liquid water largely disappeared a billion years ago. Earth and Titan are the only two worlds in the solar system known to still harbor stable liquids. On Earth’s we have a hydrological water cycle. On Titan, it’s a methane cycle. Methane in the lakes and seas evaporates, rises to condense as clouds, then returns to the surface as rain. Methane flows in rivers to the sea. The longest river, Titan’s version of the Nile, is some 250 miles long.

Once we though the Antarctic was uninhabitable. Now it’s a home to scientists during the Antarctic winter when temperatures drop to -128.6°F.  Sometime in the distant future, perhaps people will explore the surface of Titan. What an alien place they will encounter. Titan is rotationally locked with Saturn, meaning that at certain latitudes, Saturn will be hanging overhead. Faintly visible in hazy brown light, it will appear eleven times larger than our moon, with its magnificent rings extending far beyond. Saturn has more moons than any other planet, 64 at last count. Some of these may be visible moving in its dusky sky. The interior of Titan may contain “magmas” of liquid water and ammonia, which could harbor strange forms of water-based life. But, this is the place to go if you’re looking for life unlike anything we know on Earth. Instead of being water-based, it may use liquid hydrocarbons as a solvent. If such life forms exist, they would demonstrate a Second Genesis and reveal the ease with which life could populate the hundreds of billions of galaxies in our cosmos.

 

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