Look for the Moons of Jupiter


Face south after the sky has completely darkened, and look for the brightest point in the heavens. The steady light, even on a cold night when all the other stars seem to be twinkling indicates it is one of the planets. The brilliance and the time of night narrow the choices down to Jupiter, the largest world in our solar system.

Jupiter is a planet that is nearly 11 times as wide as the Earth, with a volume that could swallow our planet more than 1,000 times. But Jupiter is very far away, so it appears as nothing more than a brilliant star in the night sky until you magnify the view a little bit. It doesn’t take much magnification to see Jupiter is different from the stars; a pair of binoculars will do the job.

When you look at stars in binoculars, even the very brightest ones, they appear as the tiniest pinpoints of light. Stars are so far away that even the most powerful telescopes can only show a handful of the closest stars as anything more.

When you look at Jupiter with binoculars, the speck of light grows into a tiny circle or disk shape, still not very big, but clearly bigger than any star. And if you can hold the binoculars really steady by bracing your elbows or using a camera tripod, you may be able to see up to four tiny stars lined up next to the planet’s disk. These tiny stars are the four biggest moons that circle around the planet. The moons were discovered by Galileo Galeli in January, 1610, at a time when Jupiter was just a little farther East of where we find it this year.

Galileo used a telescope about 4 times as powerful as a pair of binoculars to view the planet. If we view Jupiter with an inexpensive telescope that can magnify the tiny disk of the planet by 80 times, twice as powerful as Galileo’s telescope, in addition to the moons we can detect faint dark bands crossing the planet. The dark belts and light bands are the tops of the clouds that surround this huge gas planet. With sharp eyes, you may even be able to detect a faintly reddish oval between one of the dark belts and the adjacent bright band. This oval is Jupiter’s Great Red Spot, a hurricane like storm that has been swirling  in Jupiter’s clouds as long as there have been telescopes powerful enough to see it.

Better views of the planet were provided by the six space probes that have visited Jupiter. Two Pioneer space probes returned the first close up images as they flew past the planet, followed a few years later by the two Voyager space probes. The Galileo probe orbited Jupiter more than two dozen times before plunging into the planet’s atmosphere. And as the Galileo mission was nearing its end, the Cassini space probe sped by, calibrating its instruments on Jupiter before heading on to Saturn.

While you can look at the pictures taken over the years through telescopes and by space probes, there’s still a special thrill to looking up at the blazing planet in the night sky and knowing you have Jupiter in your sight. Jupiter, the largest planet in our solar system, will remain visible in the evening sky until the last snow of winter has fallen.

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Time to Fall Back

Daylight savings time is over. If you did not set your clock back last night you’re  alarm went off an hour early.

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South Taurid Meteor Shower

Tonight is the peak of the South Taurid meteor shower. It is a minor shower producing about ten shooting stars per hour, but they will be difficult to see because the ten day old moon is shining nearby.

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1st Quarter Moon Crosses the Meridian

First Quarter Moon

The first quarter moon crosses the meridian, an imaginary line that runs from due south through the zenith (the highest point in the sky) and due North, at 7:57 tonight, just above the stars of Capricornus.

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Moon and Jupiter


Tonight the moon and the giant planet Jupiter rise together a little north of East. Jupiter is the bright star to the right of the moon in the early evening sky. Looking at the planet with binoculars on a tripod or braced to hold them steady, you will find three of Jupiter’s moons to the west of the planet, and one to the right. The planet Saturn in directly behind the sun today, so it cannot be seen.

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Hunter’s Moon

Hunter's Moon

Hunter's Moon

The long days of summer have passed and as we move into autumn months the hours of daylight are fewer while the hours of darkness increase. In the third week of September the sun is above the horizon just as long as it is below the horizon. This event occurs on the Autumnal Equinox, the day the sun crosses the celestial equator going from North to South.

The path of the sun, called the ecliptic, is tilted to the celestial equator by 23½ degrees. This tilt is the reason we have seasons’ It causes the sun spend more time over the horizon in the summer and less in the winter. Because the moon also follows the ecliptic around the sky, how this tilted line intersects the local horizon in the mid-northern latitudes leads to other interesting phenomena, the Harvest Moon and the Hunter’s Moon.

The Harvest moon is the full moon that occurs closest to the date of the Autumnal Equinox, and the Hunter’s moon is the next full moon of the year. During September and October the path of the ecliptic is tilted to the Eastern horizon at a shallow angle, so for a few nights around the full moon, the moon peeks over the horizon at nearly the same time the sun sets.  The change in time of moonrise from one night to the next is only about 30 minutes, noticeably less that the 50 minute average change. During those evenings the sky remains bright into the late evening while farmers gather in their crops or hunters track their prey.

The moon is visible near the horizon during dusk for several days. While the moon is low in the sky moonlight passes through a thick layer of Earth’s atmosphere. The atmosphere scatters out blue colors making the moon appear amber. Glare reducing twilight allows your eyes to out more detail, and the moon’s position just above distant landscapes makes the moon seem larger – “the moon illusion”. If you think the moon is larger, compare it to your outstretched fingertip as it rises and again later in the night when it is higher in the sky.

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Radio Astronomy

Karl Jansky

On this date in 1933, amateur radio operator Karl Jansky reported that he had detected radio emissions coming from the Milky Way. This discovery began the science of radio astronomy.

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Draconid Meteor Shower

The Draconid meteor shower reaches its peak tonight. Shooting stars will streak out of the northwestern sky. Light from a bright, waxing gibbous moon will interfere with observations most of the night.

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Far Side

Far side of the moon

On this date in 1959, the probe Luna 3 returned the first images of the far side of the moon to the Soviet Space Agency.

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First of Its Kind


On this date in 1957 the USSR launched the first artificial satellite, Sputnik, into orbit around the Earth.

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