In the Transient Sky – April 2012
March 30, 2012 3 Comments
Though not quite as spectacular as March, 4 planets are visible in the evening this month (Venus, Jupiter, Mars and Saturn).
April 2012 Highlights * Venus dominates the evening sky * Jupiter sinks lower into the evening twilight * Mars fades but rides higher in the evening sky * Saturn reaches opposition on the 15th * Comet C/2009 P1 (Garradd) is a nice binocular object in the evening sky * Mercury is the midst of a relatively poor morning apparition for northern observers and a great apparition for southern observers
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>.
Jupiter – The King of the Planets continues to slowly sink into the twilight glow this month. For most of us this will be the last time to spot Jupiter in the evening sky till next year. At magnitude -2.1 to -2.0, it is still the second brightest “star” in the sky after Venus. A very thin and difficult to see Moon will pair up with Jupiter on the evening of March 22.
Venus – Other than the Moon Venus is the brightest object in the sky. The brilliant beacon is visible high up in the southwest after sunset. Venus starts the month at its highest in the twilight sky and ends the month at its brightest (magnitude -4.7). The real showstopper occurs at the end of the apparition in June when Venus will transit the disk of the Sun. This will be the last Venus transit till 2117. The Moon and Venus make a gorgeous pair on the evening of the 24th.
Mars - Mars is the bright reddish “star” high in the East after evening twilight. Mars reached opposition the point opposite the Sun on the sky) in early March. Since Mars was near its aphelion when we passed it on our inside track, this opposition is almost as faint as can be at a magnitude of -1.2. In April, it fades from -0.7 to -0.1. The red planet will spend the month in the constellation of Leo.
Saturn - Saturn reaches opposition on April 15 at a distance of 8.75 AU (813 million miles or 1.3 million km) from Earth. Opposition means Saturn is directly opposite the Sun in the sky. As a result, it rises around sunset and is highest in the sky at midnight. The Full Moon visits on the mornings of the 7th and 8th.
Mercury – If you live in the Southern Hemisphere, Mercury will put on a nice display in the morning sky reaching its highest around April 19th. If, like me, you live north of the equator, this month’s display will be a hard one to observe.
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. March marks the lowest rates of the year.
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 January mornings, 10 or so Sporadic meteors can be observed per hour from a dark moonless sky.
Major Meteor Showers
April brings the first major meteor shower since the Quadrantids of early January. The Lyrids were produced by Comet Thatcher, a comet on a ~400 years orbit that has only been observed once back in 1861. The Lyrids meteors, on the other hand, can be seen every year.
The radiant is located between the constellations of Lyra and Hercules. Though the radiant rises during the evening, the best time to see Lyrids is after 11 pm when the radiant is high in the sky. The shower is active from April 16 to 25 with a peak on the morning of April 22. The shower only shows good levels of activity on the night of the peak. Even then, this is the most minor of the major showers with a peak rate of ~15-25 meteors per hour.
Though there are no predictions on enhanced activity, the Lyrids have been known to put on grand displays. The 1st great display goes back almost 25oo years while the last happened in 1982. But you never know, this year the Lyrids could put on a good show.
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)
C/2009 P1 (Garradd)
First seen way back on August 13, 2009 by Gordon Garradd who was observing for the Siding Spring Survey, a NASA-funded survey observing from Australia. At the time of discovery it was located at a distance 8.7 AU from the Sun, nearly the distance of Saturn. Perihelion occurred 2 days before Christmas 2011 at 1.55 AU from the Sun. Though the comet does not get very close to the Sun, it is an intrinsically bright comet and could have been a real sight had it come closer to the Sun and Earth.
The comet is in full retreat from the Earth and Sun as it heads outward on its long journey back to the cold depths of the outer Solar System. Comet Garradd is slowly moving south through the constellation of Cancer in the evening sky. Since the comet is moving away from us and the Sun it should continue to fade from around magnitude 7.0 to 7.9 as the month progresses. The comet does appear to be fading rather slowly and may be brighter than predicted here as the month progresses.
Date RA DEC Delta r Elong Mag Apr 1 09h 34m +58°01' 1.517 2.047 107 7.0 Apr 10 09h 08m +50°53' 1.693 2.124 101 7.3 Apr 20 08h 55m +44°06' 1.919 2.212 93 7.6 Apr 30 08h 50m +38°31' 2.165 2.302 85 7.9
Small Telescope Comets (V = 8.0 – 10.0)