August Mountain Skies

Graphics produced by permission with TheSky Astronomical Software, Software Bisque.

JUPITER AND SATURN ARE UP AT DUSK

The planets: We have two planets easily visible in the early evening.   Jupiter is the second brightest planet of all and, since Venus (the brightest) is lost in the glare of the sun this month, Jupiter is currently our “evening star.” Look for it due south as the sky darkens. It is just above and to the east of the bright red star Antares, which marks the heart of the scorpion. If we check a star map, we find that Jupiter is in the very bottom part of Ophiuchus the doctor. On the evening of August 9, the waxing gibbous moon stands close by. Saturn appears as a bright “star” to the east of Jupiter. Saturn is currently in the eastern part of Sagittarius the archer which is the most southern of the zodiac constellations. If you were to take a trip into the southern hemisphere, you would find Saturn much higher in the sky.

Remember last summer when we had all five of the visible planets in our evening sky? Because they are moving so slowly, Jupiter and Saturn are still in what we call the “summer skies.” The other three, however, move much more swiftly and are no longer on this side of the sun. Mars is now too low in the sunset to spot, and, in fact, it passes behind the sun on September 2. Mercury will do the same the next day. But this is not because they are moving together. Mercury is moving much faster than Mars, and this is the fourth time it has been around the sun since last summer. The beautiful Venus will beat both these guys, however, as she will pass behind the sun next week.

MercuryCan be spotted in the morning twilight for the first half of the month. Then it is lower each morning and essentially disappears into the morning twilight by the last week of the month. Passes behind the sun in superior conjunction on September 3.
JupiterVery visible this month. This month it is the brightest object in the evening sky when the moon is not present. Look for it well up in the south after sunset. It sets shortly after midnight.
SaturnEasily spotted low in the south in Sagittarius. At its highest point in the mid-evening and sets well before dawn.
VenusNot visible this month. Passes behind the sun in superior conjunction on August 14.
MarsNot visible this month. Technically, still in the evening sky but too low in the twilight to see. Passes behind the sun in superior conjunction on September 2.

 

The stars: For this issue’s constellation study, let us go a bit later in the evening than usual. Rising in the northeast about sunset is the beautiful constellation of Cassiopeia the queen, sometimes referred to as “the lady in the chair.” Cassiopeia is best spotted by looking to the northeast for a big letter “W” made up of five bright stars. Then, about 11 p.m., we begin to see the first stars of Perseus, the hero who rescued the beautiful Princess Andromeda from the sea monster Cetus. By 1 am Perseus is well up in the northeast.

The Perseid Meteor Shower: What is the significance of these two constellations? About halfway between “Cass” and “Pers,” as astronomers refer to them, lies the radiant of the Perseid meteor shower. This is the point out of which the meteors in the shower appear to radiate. It’s really an effect of perspective. Since the meteors are originating from the dust left by Comet Swift-Tuttle, they are streaming towards us down the orbital path of the comet. Thus, as we look out into space in that direction, the meteors appear to radiate out of a single point, the radiant, which happens to lie in Pers, almost in Cass. At their peak, the 2019 Perseids are predicted to reach a display of about 90 meteors per hour Monday night to Tuesday morning, August 12-13. Thus, the shower will be in progress as Perseus rises. The Perseid Meteor Shower is one of the more reliable showers and lasts for several days on either side of its peak. We can look for them for a few mornings before and after August 12 and 13. The Perseids are best observed between about 11 p.m. and dawn from a clear, dark location with a good horizon. This year the almost full moon will, unfortunately, interfere with observing all but the brightest meteors. Now, hope for clear skies.   Binoculars or telescopes are not necessary for meteor observing.

Celestial Calendar:

  • August 7, 1:31 pm EDT – First Quarter Moon
  • August 10 – The sun in its annual path around the sky appears to move from Cancer the crab into Leo the lion.
  • August 12-13 – Peak of the Perseid meteor shower
  • August 15, 8:29 am EDT – Full Moon

HIGH TIDES LATE THIS MONTH!

The Moon: This month we have another of those high tide phases of the moon. The highest, i.e., spring tides, occur when the moon and sun are lined up and the pull of their gravities on the oceans of the earth are combined. This occurs at full moon and at new moon. The effect will be somewhat stronger if the moon is near its perigee, the point in its orbit when it is closest to the earth. This month new moon occurs at 6:37 am EDT on Friday the 30th followed by lunar perigee at noon, less than 6 hours later. So, for you beach goers, set yourselves up a little higher on the beach that weekend.

The stars: Last month we discussed the appearances of Sagittarius the archer and Scorpius the scorpion low in our southern skies on summer evenings. Standing above these two rather prominent constellations are two other constellations that, while not as prominent as Sagittarius and Scorpius, nevertheless cover more of the sky. These are the intertwined constellations of Ophiuchus the doctor and Serpens the serpent. Recall that the symbol for a doctor is the caduceus, the staff of Hermes or Mercury with serpents intertwined on it. As pictured on constellation maps, Ophiuchus is usually seen holding the serpent in his hands with the head of the serpent, Serpens Caput, to the west and its tail, Serpens Cauda, to the east. Serpens is unique among the 88 classical constellations since it is the only constellation in the sky that is divided by another. The head, Serpens Caput, and the tail, Serpens Cauda, appear on opposite sides of Ophiuchus but are traditionally considered to be a single constellation.

Ophiuchus was the doctor who treated Orion when he was stung by the scorpion; therefore, he is usually pictured with one foot on the back of the scorpion. Ophiuchus is a zodiac constellation. That’s right! You won’t find him in any horoscope because horoscopes are based on fictitious calculations originally derived from the positions of the sun along the zodiac in ancient times. In the past 3500 years or so, the location of the sun’s path through the sky, the ecliptic, has changed due to precession, the wobble of the earth on its axis. In modern times the sun passes in front of the stars of Scorpius November 23-29; it then crosses the southern part of Ophiuchus from November 30 through December 17. So…if you were born in early December, your astronomical natal sign should be Ophiuchus and you are an Ophiuchid!

The planets: Now that the moon has moved into the morning skies, Jupiter reigns as “king of the night.” Look for it high in the south at sunset. It is in the southern part of Ophiuchus and just above the bright red star Antares which marks the heart of Scorpius the scorpion. If you have been watching closely, you will have noticed that the giant planet has been moving westward or “retrograde” in the sky since April 10. However, as of a week ago yesterday, it has resumed its normal or “prograde” easterly motion with respect to the background stars. This seemingly peculiar motion of the outer planets was a very difficult phenomenon to explain until Copernicus placed the sun at the center of the solar system in his model. These retrograde motions are actually due to us observing these planets from a moving platform, i.e., good ‘ol planet earth. Saturn, now located in Sagittarius just east of the famous “teapot” asterism, is also in retrograde motion and will remain so until September 18. There’s not much to say about the other three normally visible planets. Venus just passed behind the sun last week and Mercury and Mars will do so the first week of September. Thus, they are all three too close to the sun for observation.

MercuryCan be spotted in the morning twilight for about another week. Then it disappears into the morning twilight. Passes behind the sun in superior conjunction on September 3.
Jupiter Obvious this month. Look for this “evening star” well up in the south after sunset.
SaturnEasily spotted low in the south in Sagittarius. At its highest point mid-evening.
VenusNot visible this month. Passed behind the sun in superior conjunction on August 14.
MarsNot visible this month. Passes behind the sun in superior conjunction on September 2. 


Celestial Calendar:

  • August 23, 10:56 am EDT – Last Quarter Moon
  • August 30, 6:37 am EDT – New Moon
  • Noon EDT – Moon at perigee, closest to earth
  • September 5, 11:10 pm EDT – First Quarter Moon