July 2012 Highlights * Venus and Jupiter share the early morning sky * The Moon, Venus, Jupiter and Aldebaran are within 5° of each other on the morning of the 15th * Mars and Saturn slowly fade in the evening sky * Mercury continues a nice apparition in the evening sky Note: If anyone has pictures or observations of these objects/events and want to share them with my readers, send them to the Transient Sky at <firstname.lastname@example.org>.
Mercury – This month Mercury finishes off a rather good evening apparition for northern observers. On the 1st Mercury is located a few degrees above the WNW horizon an hour after sunset. It will quickly drop (as well as slowly fade) out of sight by the 2nd week of July.
Mars – Mars is the brightish reddish “star” to the SW early in the evening. Mars reached opposition (the point opposite the Sun on the sky) in early March. In July, it fades from magnitude +0.9 to +1.1. The red planet will spend the month moving eastwards through western Virgo. The Moon visits on the evenings of the 23rd and 24th.
Saturn – Saturn reached opposition on April 15 at a distance of 8.75 AU (813 million miles or 1.3 million km) from Earth. This month it continues making a nice but distant pair (~5°) with the bright 1st magnitude Spica. Both can be seen to the South at the end of twilight. Saturn will fade from magnitude +0.7 to +0.8. The Moon visits on the mornings of the 24th and 25th. Mars is quickly closing in on Saturn and Spica and will make a nice trio of similarly bright “star” in mid-August.
Jupiter and Venus – Last March, these two put on a nice display in the evening sky. After parting for a few month, they are back together, this time in the early morning sky. On the 1st, the two are located within ~5° of each other. Jupiter is further from the horizon at magnitude -2.0. Venus is much brighter at magnitude -4.6 and further down. About 3° below Venus is the brightest star in Taurus, 1st magnitude Aldebaran. Both planets will shift down relative to the stars with Venus passing within 1° of Aldebaran on the morning of the 9th. On the morning of the 15th the Moon will join the two planets and Aldebaran. All 4 will be located within an area 7° across. Definitely wake up early to see this.
The year is usually split in 2 with January through June having low rates with few major showers while July through December have high rates with many major showers. Meteor activity really takes off this month.
Sporadic meteors are not part of any known meteor shower. They represent the background flux of meteors. Except for the few days per year when a major shower is active, most meteors that are observed are Sporadics. This is especially true for meteors observed during the evening. During June mornings, 7 or so Sporadic meteors can be observed per hour from a dark moonless sky.
Major Meteor Showers
Southern Delta Aquariids
This shower will be spoiled by the nearly Full Moon this year. Luckily the even better Perseids in August won’t be bothered by the Moon.
Minor Meteor Showers
Minor showers produce so few meteors that they are hard to notice above the background of regular meteors. Info on many minor showers are provided on a weekly basis by Robert Lunsford’s Meteor Activity Outlook.
Additional information on these showers and other minor showers not included here can be found at the International Meteor Organization’s 2012 Meteor Shower Calendar.
Naked Eye Comets (V < 6.0)
None this month.
Binocular Comets (V = 6.0 – 8.0)
Small Telescope Comets (V = 8.0 – 10.0)
Comet 96P/Machholz is the only comet that will be brighter than 10th magnitude this month. And even it will be a difficult object as it will be located very close to the Sun.
This comet was discovered the old fashioned way, by an astronomer looking through a telescope. No cameras, whether photographic or digital, were used. Don Machholz first spotted 96P on 1986 May 12 from Loma Prieta peak in California. It currently takes ~5.3 years to orbit the Sun.
It has one of the smallest perihelion distances of any short-period comet at 0.12 AU. For this go-around, the comet will reach perihelion on July 14. Though the comet will be very bright at perihelion, estimates range from magnitude +2 to -2, it will be located within a few degrees of the Sun at that time making it invisible to everyone except for a few Sun-watching spacecraft. With difficulty, observers with telescopes in the Southern hemisphere will be able to watch the comet rapidly brighten but also rapidly approach the Sun for the first few days of July. Those of us in the Northern hemisphere have a chance of spying the quickly fading comet during the last few nights of July.
Date RA DEC Delta r Elong V 2012 Jul 01 05h 35m -02d 44' 0.955 0.521 31 9.5 2012 Jul 11 06h 51m +14d 14' 1.092 0.211 11 5.1 2012 Jul 21 09h 01m +30d 30' 1.003 0.291 17 6.6 2012 Jul 31 11h 10m +27d 03' 0.894 0.587 35 10.0 RA = Right Ascension, DEC = Declination, Delta = distance from Earth in AU r = distance from the Sun in AU, Elong = elongation from Sun in degrees V = Visual magnitude