In the Transient Sky This Month
April 2013 Highlights * Comet C/2011 L4 (PANSTARRS) will be visible in the morning sky fading from magnitude 4 to 7 * Comet C/2012 F6 (Lemmon) will be a 5th-6th magnitude object for SH observers * Saturn at opposition on the 28th * Jupiter continues to dominate the early evening sky * Mercury finishes a great morning apparition for southern observers (not so good for northerners) 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>.
Venus – Venus was in superior conjunction last month. This month the planet is still too close to the Sun for most observers. A lucky few may be able to pick it out against the bright glow of evening twilight by the end of the month.
Jupiter – The King of the Planets dominates the early evening sky being high in the western sky at the end of evening twilight. On the 1st Jupiter sets around 11:30 pm and by 10 pm at the end of the month. It spends the month a few degrees northeast of the stars of the Hyades cluster in Taurus as it fades from magnitude -2.1 to -2.0. The Moon pays Jupiter a visit on the evening of the 14th.
Saturn – Saturn reaches opposition this month on the 28th. On that data the ringed planet will be observable all night long. It will also be at its brightest for the year on that night at magnitude +0.1. The Moon passes close to Saturn on the morning of the 25th.
Mercury – Mercury starts the month in the midst of a good morning apparition for Southern Hemisphere observers. The view is much worse for northern observers. Mercury slowly moves back towards the Sun as the month progresses.
Mars – Both planets are too close to the Sun for easy observation this month. They will be back this summer, Venus in the evening sky and Mars in the morning sky.
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 is near its annual minimum 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 April mornings, 5 or so Sporadic meteors can be observed per hour from a dark moonless sky. The rate is near an annual minimum this month.
Major Meteor Showers
This year’s Lyrid meteor shower is seriously hampered by a nearly Full Moon on the night of its peak (April 22nd). The Moon will greatly reduce the usual number of 10-15 meteors per hour.
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)
C/2011 L4 (PANSTARRS)
Comet PANSTARRS peaked around magnitude 1.5 when it reached perihelion at 0.30 AU from the Sun on March 10. The comet has rapidly faded as it moves away from the Earth and Sun. Observations over the past few days place is around magnitude 4.0 to 5.0.
In March it was an evening object though it spent all month hugging the western horizon and was only visible in twilight. In April the comet can still be seen in the evening with difficulty but it has become much easier to see in the morning. PANSTARRS starts the month in Andromeda only a few degrees from the Andromeda galaxy. As the month progresses it will continue moving north across Andromeda and Cassiopeia.
The comet will fade by ~1 magnitude per week but should remain a good sight in small telescopes and binoculars all month long.
Finder charts can be found at Chasing Comets.
Ephemeris for C/2011 L4 (PANSTARRS) Date RA DEC Delta r Elong V 2013 Apr 01 00m 31m +36d 33' 1.275 0.684 32 4.4 2013 Apr 11 00h 27m +48d 13' 1.358 0.899 41 5.5 2013 Apr 21 00h 21m +58d 12' 1.442 1.102 50 6.3 2013 May 01 00h 11m +67d 12' 1.528 1.295 57 7.0 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
C/2012 F6 (Lemmon)
Everyone was expecting C/2011 L4 (PANSTARRS) and C/2012 S1 (ISON) to be the two naked eye comets of 2013. No one was expecting C/2012 F6 (Lemmon) to be vying for the status of naked eye comet when it was discovered by Alex Gibbs of the Mount Lemmon survey back on March 23, 2012. At that time the comet was a faint 20th-21st magnitude and 5.0 AU from the Sun. It also appeared to be an intrinsically faint comet. So faint in fact that I though it had a good chance of disintegrating near perihelion. Instead the comet brightened at a rapid rate.
This surprise comet brightened to magnitude 4.5 to 5.0 as it reached perihelion on March 24, 2013 at a distance of 0.73 AU from the Sun. Unfortunately there have been very few brightness estimates made over the past few weeks. Not only is the comet not visible for those north of the Equator but the comet is also located only ~24 degrees from the Sun.
Lemmon should fade now that it is moving away from the Sun and Earth and may be as faint as magnitude 6-7 by month’s end. Even though it is moving nearly due north through Cetus and Pisces this month it will still not be visible to northern observers till May.
Finder charts can be found at Chasing Comets.
Ephemeris for C/2012 F6 (Lemmon) Date RA DEC Delta r Elong V 2013 Apr 01 00h 11m -17d 50' 1.547 0.746 24 4.9 2013 Apr 11 00h 12m -08d 40' 1.622 0.810 24 5.3 2013 Apr 21 00h 14m +00d 06' 1.671 0.910 28 5.8 2013 May 01 00h 17m +08d 32' 1.701 1.031 34 6.4 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
Binocular Comets (V = 6.0 – 8.0)
Small Telescope Comets (V = 8.0 – 10.0)