StarWatch: Moravian College Astronomy
StarWatch for the greater Lehigh Valley


128    FEBRUARY 7, 1999:   Elongations
Have you found Venus in the evening sky? You can observe it about 6:00 p.m., 15 degrees, or about one and a half fists above the SW horizon. About three fists up (30 degrees) is the planet Jupiter, and two more fists brings you is Saturn. It should be obvious that Venus is overtaking Jupiter. Venus is 15 degrees from Jupiter tomorrow, 10 degrees on Feb. 13, and 5 degrees on Feb. 18. The race will conclude with a beautiful planetary conjunction on Tuesday, February 23, best seen about 45 minutes after sunset. The positioning of Venus, Jupiter, and Saturn presently lie to the left of the sun. Astronomically put, the elongations of Venus, Jupiter, and Saturn are to the east of the sun. Planets which are farther from the sun than Earth--superior planets--can have elongations as great as 180 degrees (opposition). Then they are opposite to the sun and rise at sunset. When the moon is at opposition, we say it is in the full phase. When elongations equal zero, the planet or moon appears in the same part of sky as the sun (a conjunction) and, therefore, cannot be seen. For the moon this is the new phase. Mercury and Venus lie inside the Earth’s orbit and are also tagged as inferior planets. They can never have an elongation of 180 degrees. In fact, their maximum elongations are 28 degrees (Mercury) and 47 degrees (Venus). They always follow the sun, visible either in the early evening after sundown or prior to dawn. Venus will reach its greatest eastern elongation of 45 degrees on June 11. It will be in the sky throughout a good part of this year to mingle with Saturn (March), bright stars, and, of course, the moon.
129    FEBRUARY 14, 1999:   Moon, Venus, Jupiter Embrace
The countdown continues as brighter Venus steadily gains on Jupiter in the western sky. Observe between 6-7 p.m., for the Earth’s rotation carries them quickly to the horizon by the time of complete darkness. Tonight, Venus has crept to within nine degrees of the planet Jupiter. By the weekend, look for Venus to be only three degrees from Jupiter. However, the week holds more promise than just the nightly embrace of two conspicuous planets. If you saw the moon late last week, it had to have been in the early morning hours. It was a waning crescent shrinking nightly as it approached the sun’s position. Incidentally, the new moon occurs on Tuesday. There will be a solar eclipse (annular) in the Southern Hemisphere, but it won’t be visible from here. Now the moon swings east of the sun to begin appearing in the evening sky. Look for an extremely thin pale crescent on Wednesday, directly below Venus around 6:15 p.m. The separation of the moon from Venus will be about the same as the distance between Venus and Jupiter. On Thursday, the moon is above and to the left of Jupiter. With just a little added magnification, the sight of the Moon, Jupiter, and Venus on Thursday will be spectacular. View with binoculars. By the weekend, keep watching the moon for earthshine (reflected Earth light from the moon) as it draws farther away from Jupiter and appears higher in a dark sky. Follow the pursuits of Allentown School District astronomy students as they keep you informed of their field experience at the web site below.
130a  FEBRUARY 21-23, 1999:   Venus Courts Jupiter
The moon continues to brighten during the week, but its luminescence will be no match for Tuesday’s close planetary conjunction between Venus and Jupiter. If Tuesday evening is clear, a real treat is in store for the East Coast of the US. Venus should become easily visible about 15-25 minutes after sunset (sunset occurs at 5:45 p.m.), and if you look closely, Jupiter will be only about 1/5 of a degree away. Use binoculars to make your first sighting, but as the sky becomes darker, Jupiter should easily reveal itself to the unaided eye. Venus will outshine Jupiter by about six times. Dust off your telescope, if you own one, because this will be one of the few times where you will be able to compare two bright planets in the same field of view at the same time. Ironically, fainter Jupiter will be 3.7 times more distant than Venus, but will appear nearly three times larger than Venus through the eyepiece. Jupiter is truly the king of all the planets with regards to size. There has been some speculation that people unaware of the conjunction and casually viewing the western sky during twilight, will perceive the close grouping as one object. The 1/5 degree separation between Venus and Jupiter is less than half the diameter of the moon. It will be the closest planet pairing of the year. If your western horizon is unobstructed, check with binoculars for elusive Mercury between 6:15 p.m. and 6:30 p.m. It will be about one fist below Jupiter and Venus, and about one fist above the horizon.
130b  FEBRUARY 24-26, 1999:   See the Venus-Jupiter Conjunction
Last night had to be a disappointment for those of us who had been patiently watching Venus nearing Jupiter over the past several weeks. The two planets were paired only 1/5 of a degree apart, making this the closest planetary conjunction of the year. Cloud cover shrouded this event from being seen by local residents. However, not all is lost. As the days continue, you will see Venus leading Jupiter by ever greater distances. Eventually, the sun will overtake Jupiter, hiding it from our view, while only brilliant Venus and less striking Saturn reign in the early evening sky. Last week, while in Arches National Park, near Moab, Utah, local astronomy students from Dieruff and Allen high schools captured the beautiful conjunction of the moon, Venus, and Jupiter visible low in the western sky after sunset. These photos can be seen at the web site address noted below. When the front page loads, simply click on the "Postcards from the Dieruff Academy" button and you’ll be able to see what we saw in Utah. The near approach of Venus to Jupiter seen on Tuesday from the Lehigh Valley, is also included. Feel free to download the pictures or print them as a souvenir of this magnificent event. If weather conditions improve later in the week, look for more photos to be posted at this site address. Other pictures from the Dieruff Academy’s New Mexico-Utah Field Experience can also be viewed.
131    FEBRUARY 28, 1999:   Mercury Debuts in West
If you have been casually viewing the western sky at dusk over the past several weeks, you certainly have noticed Venus move up to Jupiter, and then pass it. It was cloudy here in the Lehigh Valley on the evening of the big event, February 23, but there were reports that some people caught the close planetary coupling from the Reading area. Venus has now pulled an impressive distance away from Jupiter, setting its sights on fainter Saturn. These two planets will be grouped with the thin waxing crescent moon on the evenings of March 19 and 20. This will be the focus of next week’s StarWatch column. Presently, Mercury is making a quick debut into the evening sky and can be viewed below Jupiter if your western horizon is free from obstructions, and the night is clear. View between 6:20 p.m. and 6:40 p.m. for the best results. The week will start with Venus, Jupiter, and Mercury almost equally spaced. Venus will be the brightest and highest in the sky, while Mercury will be the faintest and closest to the horizon. Binoculars will probably be necessary to spot Mercury. By the end of the week, Mercury’s position will be about four degrees (8 lunar diameters) to the right of Jupiter. On March 8, look for Mercury, Jupiter, Venus, and Saturn to be separated by only 28 degrees. Remember that all of these events are viewed in the west during twilight, as the sky is becoming darker. Binoculars will surely help make your viewing experience more pleasurable.
February Star Map