by Anne Holt Sunrise 1st: 06.43 30th: 05.37 Sunset 1st: 19.43 30th: 20.36 Astronomical darkness 1st: 21.49 to 04.35 30th: 23.21 to 02.50 New Moon: 5th at 09.50 Full Moon: 19th at 12.12 Lunar apogee: 1st at 00.15 (405576 km) 28th at 18.21 (404576 km) Lunar perigee: 16th at 22.06 (364208 km) Because
we have 2 Lunar apogee in April it means that the month includes a
complete anomalistic month - the name given to the period between 2
successive perigee or apogee. April full Moon
is known as the Pink Moon, because of the pink flowers which bloom in
the spring (tra la - for any fans of G&S). Other names are the
Sprouting Grass Moon, Hare Moon and Fish Moon. The Old English/Anglo
Saxon names are Egg Moon and Paschal Moon, because this is the one used
to calculate the date of Easter. Highlights What
highlights? It's almost the end of our 2018/19 season and now the
clocks have changed it's too light to do any observing before 9pm, even
when the sky is clear. At the start of April we have 6 hours 46 minutes
of astronomical darkness, but only half as long by the end of the month.
The only planet putting on a good show is Jupiter, shining brightly in
the morning sky at mag -2.3. The downside is that it remains very low.
The first reasonable meteor shower in months will be washed out by the
glare of the just past full Moon and we'll probably have a lot of rain -
April is known for its showers. Looking away from the
sky, we do have Easter to look forward to, towards the end of the
month. It has an astronomical connection in the way it is calculated,
Easter Sunday is the Sunday after the first full Moon on or after the
Vernal Equinox, the date of which is always taken as March 21st even
when, as in the last few years, it actually occurs on 20th. The
earliest possible date for Easter Sunday, March 22nd, is extremely rare,
the last time was in 1818 and the next won't be until 2285. The latest
date, April 23rd, is much more frequent, some of us may have been around
the last time in 1943, others may still be here for the next in 2038.
The sequence of dates isn't quite as random as it may appear - it will
start to repeat itself after 5,700,000 years. Which got me thinking:
is this why mathematicians keep on calculating pi to more and more
decimal places? Do they hope to eventually find a pattern? The latest
attempt, by a Google employee, has got it to 31,415,926,535,897 decimal
places. I did wonder why they stopped there, rather than adding a few
more to make a nice round number - till I realised that this is the
first 14 digits of pi. Constellations Now
that BST has been forced upon us, we have to wait even longer for the
skies to darken each evening. By the time it gets really dark the winter constellations, including the beautiful area
around the Winter Hexagon, so rich in bright stars, is sinking slowly in
the West.Ursa Major is now high in the sky with the Plough overhead around midnight in the second half of the month. Follow the curve of the handle down to the orange coloured Arcturus, brightest star in the constellation Bootes the herdsman, and the 4th brightest in the night sky. The signature constellation of spring, Leo, is still riding high in the south and the Summer Triangle of Vega (in Lyra), Deneb (Cygnus) and Altair (Aquila) is now rising in the east and visible in the early hours. Planets Mercury: in Aquarius, mag 0.8 A
morning object this month but very low in the sky throughout. On 1st it
rises at 06.07 but is still 3 degrees below the horizon at dawn. It is
at aphelion (furthest point in its orbit from the Sun) on 10th at 08.40
and the following day reaches greatest western elongation at 27.7
degrees west of the Sun but, because of the angle of the ecliptic, is
still very low. On 13th it reaches its highest point in the morning
sky, rising at 05.46 but still not managing to clear the horizon before
the sky begins to brighten. On 16th it moves into Pisces and from 23rd
spends a few days over the border in Cetus, before returning to Pisces
on 27th, brighter at mag -0.2 but still too low to be seen easily. By
month end it rises at 05.17, only 20 minutes before the Sun. Venus: in Aquarius, mag -4.0 Also
very low in the morning sky this month but, because it is so much
brighter than Mercury, might be seen in the morning twilight. On 1st it
rises at 05.55, just under an hour before Sunrise, reaching 2 degrees
in the ESE by dawn. On 2nd the crescent Moon passes south of the
planet, closest (2.5 degrees) at 08.11, about 90 minutes after
Sunrise. Mercury is also quite close to the pair but much harder to see
in the dawn sky. Venus is at aphelion on 18th, then follows the
smaller planet into Pisces on 17th, then into Cetus from 27th to 29th.
On 30th, when it is back in Pisces, it rises at 05.00 as civil twilight begins. Mars: in Taurus, mag 1.4 Visible
in the evening sky, as it begins to darken, still setting around 00.30
each day. On 1st it is about 32 degrees altitude in the west at 20.30. During
the first few days of the month it moves N eastwards between the
Pleiades and the Hyades (the V shaped head of the bull asterism). On
1st it is 3.5 degrees SSW of the small cluster and on 8th and 9th the
Moon joins the party, at 21.00 on 9th the Moon will be 7 degrees to the
SE. On 31st Mars is 20 degrees above the western horizon as the sky
darkens around 21.30, setting 3 hours later. Jupiter: in Ophiuchus, mag -2.3 Very
bright in the morning sky but still low. On 1st it rises at 02.17 and
culminates, 13 degrees above the southern horizon, at 06.05, just over
half an hour before sunrise. It rises earlier as the month progresses
but will remain low for a long time yet. On the morning of 23rd the 84%
Moon passes 6 degrees west of the planet at around 4am. They are at
their closest, less than 2 degrees apart, around 13.00, in daylight. On
30th it rises at 00.21 and reaches 13 degrees in the south at 04.09,
while the sky is still quite dark but not astronomically so. Saturn: in Sagittarius, mag 0.6 Another
morning object in the southern part of the Zodiac, so remaining very
low in the sky. On 1st it rises at 04.00 and reaches an altitude of 10
degrees by dawn. On the morning of 25th, the 67% Moon passes about 6
degrees west of the planet, the following day it is 6.7 degrees to the
east. They are at their closest, only 22 arcminutes, during the day of
25th - if you happen to be in Australia or New Zealand on that day
(night on that side of the world) you might see the Moon occult the
planet. On 30th it rises at 02.09 and reaches 13 degrees before the sky
gets too bright. Uranus: in Aries, mag 5.9 Not
visible this month as it approaches Solar conjunction, when it is on
the opposite side of the Sun from the Earth. On 23rd it sets an hour
and a half after the Sun but is separated from it by only 20 degrees.
At the end of the month it is a morning object but even closer - on 30th
it appears only 6 degrees from the Sun, rising just 9 minutes before
it. Neptune: in Aquarius, mag 8 Still
not visible after last month's Solar conjunction. On 1st it rises 30
minutes before the Sun but is still 9 degrees below the horizon at
dawn. By 30th it rises at 04.29 but still doesn't reach the horizon
before the sky brightens. Dwarf Planets and Asteroids Ceres,
in the asteroid belt, is the only dwarf planet which is close enough
and bright enough to be seen through a small scope. In April it is in
Ophiuchus at mag 8.2. On 1st it rises at 00.55 and culminates, 19
degrees in the south, 75 minutes before Sunrise. It brightens slightly
during the month, reaching mag 7.6 by 30th, when it rises at 22.55 and
culminates, still at 19 degrees, at 03.25. The
rest, which orbit beyond Neptune, in the Kuiper Belt, are too distant
and too faint to be seen even in the best amateur scopes. When well
positioned they could possibly be targets for good amateur
astrophotographers Pluto; in Sagittarius, mag 18.8 Too low in the sky to be a reasonable photographic target, never gets higher than 14 degrees above the horizon. Eris: in Cetus, mag 18.8 Reaches Solar conjunction on 13th, so not visible this month as it appears too close to the Sun. Haumea: in Bootes, mag 17.3 A
much better bet for any keen astrophotographers who fancy a game of
Spot the Difference with images taken a few days apart. On 1st it
reaches 53 degrees above the southern horizon at 02.49. It is at
opposition (directly opposite the Sun in the sky) on 16th, and on 30th
culminates at 00.54 at around the same altitude. Makemake: in Coma Berenices, mag 17.1 Also
well positioned for photography. On 1st it is at 32 degrees in the east
at 21.04, just before the start of astro darkness, and 40 degrees in
the west by dawn. On 30th it is at 57 degrees in the SE at 22.15 and 35
degrees west at dawn. A couple of asteroids
reach opposition in April. They are closer and brighter than the distant
dwarf planets, even though they are much smaller, and might be seen in
amateur scopes - even in good binoculars from a very dark sky site.
Again the comparison method is best, as they will never appear as
anything other than a point of light. Pallas: in Bootes, mag 7.9 The
second asteroid to be discovered culminates at 02.35 on the 1st, at an
altitude of 51 degrees in the south, 5 degrees SW of Arcturus. It moves
northwards through Bootes, reaching opposition on 6th. By 30th it will
have faded to mag 8.2, culminating at 00.19, still reaching 51 degrees. Iris: in Corvus, mag 9.4 The
4th brightest object in the asteroid belt is much lower in the sky. On
1st it culminates at 01.20, reaching 22 degrees in the south. It is at
opposition on 5th, when it gets to 23 degrees at 01.01. On 17th it
moves into Virgo and ends the month at mag 9.9 but slightly higher,
culminating 26 degrees above the southern horizon at 22.54. As always, recommended sites for exact positions and more information on Solar System objects Meteor Showers One fairly major shower in April. The Lyrids, active April 16th to 28th, peak on the night of 22nd/23rd. ZHR 18. These
medium paced meteors are the earliest recorded shower, in 687 BC
Chinese astronomers noted that meteors fell like rain. Nothing like that
now but there are occasional outbursts, the last in 1982 when a ZHR of
90 was recorded at the peak. The parent comet is C/1801G Thatcher,
which no one alive now will have seen or ever will see - its last visit
was in 1861 and it won't return until 2276. The bad news
is that this year's shower will be a washout, even if it isn't raining
all but the brightest meteors will be washed out by the glare from the
just past full Moon. Minor Showers A few of these are given in various sites, however none are included in the International Meteor Organisations calendar. Gamma
Virginids, active 5th to 21st, peak 14th. These could well be
considered by the IMO to be part of the Antihelion Source, which has a
radiant moving through Virgo in April. Some
sources mention a couple of weak showers with radiants in Draco, active
in the first half of the month, Delta Draconids, peak 31st March to 2nd
April and the Tau Draconids, peak April 1st. Might be worth keeping an
eye on the general direction of Draco at the start of the month. Alpha
Bootids: active April 4th to May 13th, peak 28th. very slow moving
meteors leaving trails. The shower could include fireballs. Comets A couple are still quite high in the sky but have faded considerably, and continue to do so. 46P/Wirtanen:
in Leo Minor, mag 13.3. On 1st it is 60 degrees above the SE horizon
at 21.04, culminating slightly higher, at 22.30. It moves into Leo on
29th ending the month at mag 15.2, about 60 degrees in the west at
22.14. 38P/ Stephan-Oterma: in Lynx, mag
12.5. Also fading but not as fast as Wirtanen. It's still circumpolar,
on 1st it reaches 78 degrees in the south at 21.23. It moves into Leo
Minor on 25th and ends the month at mag 13.3, reaching 61 degrees in the
SW at 22.14. Unfortunately the website which I usually recommend for details of current comets, seems to have vanished. Maybe it will return in time for next month's sky notes. |