Venus Kisses Saturn On Friday Jan. 8

On Friday, January 8, the planet Venus will appear to pass just 5 arc minutes north of the planet Saturn, That is a mere one-sixth of the diameter of the moon, a small enough distance to fit in the eyepiece of a powerful telescope.

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On January 9, the planet Venus will appear to pass just north of the planet Saturn. Credit: Starry Night software.

This will be a rare opportunity to see two planets at the same time in a telescope’s narrow field of view. In a lifetime of observing the skies, I have seen such a close conjunction of two planets only two or three times. With the naked eye, sharp-eyed observers will be hard pressed to separate the two points of light.

Unfortunately for observers in North America, the point of closest conjunction will occur at 11 p.m. EST, while the planets are below the local horizon. For a skywatcher in New York, for example, the planets won’t clear the eastern horizon until 5 a.m. EST, at which time they will have separated so that they are 17 arc minutes apart, or slightly more than half the diameter of the moon. Even so, they will still fit in a telescope eyepiece.

Of course, this conjunction is something of an optical illusion. The two planets aren’t anywhere near each other in space, but merely appear close together from our perspective here on planet Earth.

Venus is currently on the far side of the Sun from Earth, 1.22 astronomical units distant (1.22 times the average distance from the Earth to the sun), so it appears similar to a gibbous moon.
Saturn is 10.79 astronomical units from Earth, nearly 9 times farther away than Saturn.

The two appear almost the same angular diameter: 14 arc seconds for Venus, 15 arc seconds for Saturn, yet in reality Saturn is actually almost 10 times the diameter of Venus. So Saturn’s greater distance balances out is larger size, and the two appear almost the same from Earth.

The most striking difference between the two is their difference in brightness. Venus is magnitude –4.0 on the upside-down brightness scale astronomers use, while Saturn is only magnitude +0.5, 4.5 magnitudes (or almost 100 times) fainter than Venus. This difference is mainly due to Venus’ closeness to the sun (0.72 astronomical units) compared to Saturn’s (9.55 astronomical units).

When you look for the twin planets just before dawn on Saturday morning, the first thing you will notice is Venus shining brightly in the southeastern sky. You will have to look closely to spot “tiny” Saturn just above and to the right of it.

If you own a planetarium program like Starry Night that lets you travel to other planets, check out the view Saturday morning from Saturn. You will see Earth and Venus in a close conjunction, Venus a narrow crescent from Saturn’s perspective, and Earth a rounded gibbous shape, since despite being close in the sky, they are actually on opposite sides of the sun, and lit by it quite differently.

Venus Vanishes Behind The Moon

Next Monday, December 7, the planet Venus will do a vanishing act behind the moon. 

In the course of its monthly journey around Earth, the moon often passes in front of stars, and occasionally planets.

Next Monday it will pass in front of the brightest of them all, the planet Venus, in what is called a lunar occultation.

This will be visible, weather permitting, all over North America. The only catch is that it occurs in broad daylight.

I’m often surprised that many people don’t know that the moon is visible in the daytime sky; in fact my son first spotted it when he was about 2 years old. That mainly says that very few people bother to look closely at the sky. On Monday, the moon will be a slender crescent only a few days away from new moon, so may be a bit harder to spot, though if you start observing at dawn you should have no trouble following it up into the blue sky.

Venus is also visible in daylight provided you know exactly where to look. On Monday, its closeness to the moon will help you spot it.

The time the occultation will occur depends on your exact location. For example, in New York City, Venus will disappear behind the moon at 12:43 p.m. EST and reappear at 1:51 pm. In Chicago the occultation lasts from 11:20 a.m. CST until 12:35 p.m. In Los Angeles, the times are 8:06 and 9:56 a.m. PST. The easiest way to get the exact times for your location is with a planetarium program like Starry Night or SkySafari.

It was observations of occultations by the moon of stars and planets that first told us that the moon has no significant atmosphere. Stars simply wink out and in as they pass behind the moon; planets show no fuzziness as they disappear behind the moon’s edge.

Starry Night gives you the opportunity to travel to other places in the universe, and view events from a different perspective. Our second image today shows the view of this occultation from the planet Venus at 12:35 p.m. EST. Instead of an occultation, we see what is called a transit, as one object (the moon) passes in front of another (Earth). The moon is moving from right to left in this view.

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Seen from Venus, the moon will transit Earth, blocking the view of most of North America. If the moon looks strange here, it’s because we’re looking at its far side, the side never seen from Earth. Credit: Starry Night software.

The occultation is already over on the east coast, to the right of the Moon, and has yet to begin on the west coast, to its left. The surface of the moon looks strange because we are seeing its “far side,” the side permanently turned away from Earth. This side has more mountains and craters and fewer open flat plains than the side we usually see.

Extreme Venus And A Close Encounter With Jupiter

On Monday morning, October 26, Venus will be at its greatest elongation west, the farthest it can get from the sun as seen from Earth.

Venus has been dominating the morning sky for the last two months, and reaches its greatest angular separation from the sun on the 26th: 46 degrees west of the sun. Remember, directions in the sky are the reverse of directions on the surface of the Earth because we are looking outward rather than inward, so west is to the right in the sky if you live in the northern hemisphere.

The inner planets, Mercury and Venus, never stray far from the sun in Earth’s sky. Mercury was at greatest elongation west, 18 degrees from the sun, last Friday, October 16, and is now moving back towards the sun. Venus is still moving away from the sun, but will pause and reverse directions on the 26th. Mars and Jupiter, with orbits outside that of Earth, both appear to be moving steadily westward relative to the sun.

As a result, Venus and Jupiter will pass very close to each other on the 26th, within 1.1 degrees.

Venus is by far the brightest of the two, at magnitude –4.6, while Jupiter is nearly 3 magnitudes fainter at magnitude –1.8. Mars, which is also nearby in the sky, comes a distant third in brightness at magnitude +1.7, more than 3 magnitudes fainter than Jupiter and 6 magnitudes fainter than Venus.

This close conjunction of Venus, Jupiter, and Mars is best observed with the naked eye or binoculars. In a telescope, Venus will appear as a perfect miniature quarter moon, because at greatest elongation it is lit by the sun exactly from its left side. It is 24 arc seconds in diameter, slightly smaller than Jupiter at 33 arc seconds, but much larger than Mars at 4 arc seconds.

Venus appears brightest because it is both close to the sun and close to Earth. Jupiter is much larger in actual diameter, but is far from the sun so only lit dimly. Mars, in between in distance from the sun and small in size, is currently very far from Earth, so appears even dimmer.

To put them in perspective, even though grouped close together in our sky, the three planets are at vastly different distances. Venus is closest at 0.69 astronomical units, Mars next at 2.2 a.u., and Jupiter farthest at 6.0 a.u., nearly ten times farther than Venus. An astronomical unit is the average distance between Earth and the sun.

Many photographers have been taking advantage of the close approach of these three planets to photograph them in the dawn sky, though the different brightnesses present a challenge in exposure. As always, we welcome your pictures of this beautiful event.

Catch The Double Crescents This Week: Venus and the Moon

On Saturday evening, July 18, the crescent moon, moving eastward in the sky, will pass directly below the crescent planet Venus, moving westward, soon to pass below the sun.

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On Saturday, July 18, the moon passes just below the planet Venus, both objects showing narrow crescents.  Credit: Starry Night software.

Both objects are being back-lit by the Sun, so that both appear in our sky as crescents. The moon is just three days past new moon, so only nine percent of its disk is lit by the sun. The remaining 91 percent is lit by sunlight reflecting off the surface of the Earth, what is called “earthshine” or “earthlight.” Sometimes this view is also called “the old moon in the new moon’s arms.”

To the naked eye, Venus appears like a brilliant pinpoint of light. Turn your binoculars on it, and that slight additional magnification will allow you to see that Venus is also a narrow crescent.

Because Venus is farther away than the moon, it is lit by the sun at a slightly different angle, so is nineteen percent illuminated, a slightly fatter crescent than the moon.

Some observers have suspected a faint glow coming from the part of Venus not in direct sunlight, a phenomenon called “the ashen light.” No one knows exactly what causes this glow, but it has been reported by many experienced astronomers. Spectroscopic observations have shown pulses in the light, so it might be due to lightning in the hot acidic atmosphere of Venus.

As mentioned above, even small binoculars provide enough magnification to turn the naked-eye pinpoint of Venus into a visible crescent. This is one of many objects in the sky which are revealed or enhanced in binoculars, which is why they are considered an essential tool for all serious skywatchers.

Binoculars for astronomy should have a front aperture of at least 50 millimeters (2 inches). This is seven times the diameter of the fully dark-adapted eye. Such a small binocular has seven times the resolution and 50 times the light-gathering power of the naked eye. 50 millimetre binoculars come in two magnifications, 7 power (7x50) and 10 power (10x50). Both are very useful for astronomy, but I prefer the 10x50 because of its slightly higher magnification and better contrast in a bright sky. I find more powerful binoculars too heavy to hold steadily for any length of time, and mounting them on a tripod defeats the ease of use.

Venus and Jupiter, Up Close and Personal

If you’ve been watching the western sky just after sunset lately, you will have noticed two bright objects, gradually drawing closer.

These are the two brightest planets, Venus and Jupiter. Venus is the brighter of the two, currently magnitude –4.6 on the upside-down brightness scale astronomers use. It will get slightly brighter over the next 10 days, reaching greatest brilliancy on July 10 at magnitude –4.7.

Jupiter is somewhat fainter at magnitude –1.8, down from a maximum of –2.6 when it was in opposition on February 6.

Although the two planets look very close in Earth’s sky, they are in fact very far apart, on opposite sides of the sun. The first graphic shows their true positions, as seen from far above the sun’s north pole. Venus is slightly nearer Earth than the sun, 0.512 astronomical units distant (47.6 million miles or 76.5 million km.) while Jupiter is 6.083 astronomical units away (565 million miles or 910 million km.) on the far side of the sun.

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Seen from far above the sun’s north pole on Wednesday, July 1, Earth, Venus and Jupiter lie almost on a perfect straight line.  Credit: Starry Night software.

Viewed in a telescope, the two planets are, by coincidence, exactly the same apparent size, 32 arc seconds in diameter, about a 60th of the apparent diameter of the moon, but look very different.

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Seen in the eyepiece of a telescope magnifying 65 times at sunset on July 1, Venus and Jupiter appear very close, but look very different, even though both are the same angular size. Credit: Starry Night software.

Venus, with its bright cloud cover and closeness to the sun, is a brilliant white crescent, lit from slightly behind because it is moving between us and the sun. Jupiter’s cloud tops are somewhat darker than Venus’, but it is also more than seven times farther away from the sun. As a result, despite its large size, Jupiter appears much fainter in a telescope than Venus.

Two bright planets in close proximity make a striking sight with the naked eye. In binoculars you should be able to see that Venus is a tiny crescent and Jupiter is a disk accompanied by 3 tiny moons (on July 1, Callisto will be behind Jupiter). A small telescope will make the view much clearer.

As you continue to watch these two planets over the next few weeks you will see them draw apart as both get closer to the sun, Venus passing between us and the sun on August 15, and Jupiter passing behind the sun on August 26. In another month, both will reappear in the morning sky, where they will join Mars, which passed behind the sun on June 14.

Venus At Its Brightest

If you’ve been watching the sky in the early evening lately, you can’t have missed seeing the planet Venus in the west.

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Credit: Starry Night software.

Venus has been travelling around its orbit towards us, appearing in evening twilight higher and higher in the sky. This week on Saturday, June 6, it reaches its greatest angular distance from the sun, 45 degrees, at what is called “greatest elongation east.” Even though we are looking at it in the western sky, it is elongated in the direction of the eastern horizon, so it is east of the sun in astronomical terminology.

As seen in a small telescope, Venus this week appears like a brilliant miniature first quarter moon. However, unlike the moon’s pock-marked surface, Venus appears perfectly smooth. That’s because we are seeing only the tops of its dense clouds, which mostly appear a featureless blank white.

Beneath those bland clouds lies one of the most bizarre of alien worlds: the greenhouse effect gone wild with a terrain of bare rock heated to a uniform world-wide temperature of  864 degrees Fahrenheit (462 degrees Celsius), where the endless clouds rain down sulfuric acid.

There are, in fact, vague shadings in the surface of Venus’ clouds. These are best seen with a deep violet filter such as the Wratten 47 available in most telescope stores. It also helps to observe Venus in a daylight sky, when much of its glare is cancelled by daylight.

Whenever Venus is close to elongation, we begin to hear many reports of UFOs in the western sky. Venus is so bright that even experienced stargazers are sometimes taken by surprise.

Over the next few weeks, Venus will begin to move closer to the sun at twilight, actually passing between Earth and sun on August 15.

Most of the planets are so small and far away that they appear as star-like dots in most binoculars. Venus is the exception to this. Study it closely with binoculars over the next few weeks, and you will see it first as a tiny half-moon, then gradually getting larger in size but with a thinner crescent shape as it draws nearer the Earth.

Because Venus’ orbit has a slightly different tilt than Earth’s orbit, Venus usually passes above or below the sun, rather than passing directly in front of it. This August it will pass just 8 degrees south of the sun.

Twice so far this century, the orbits of Earth and Venus crossed with both planets in exactly the right position, and Venus was visible in front of the sun. Unfortunately the next such transit of Venus will not occur until the year 2117. I was lucky enough to have clear skies for both the transits of Venus in 2004 and 2012, and seeing the tiny black dot of Venus through a solar filter was a highlight of my observing life.

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