The
purpose of this feature is to give scout leaders, educators and naturalists an
idea of some of the natural events coming up each month. We will try to
cover a variety of natural events ranging from sky events to calling periods of
amphibians, bird and mammal watching tips, prominent wildflowers and
anything else that comes to mind. We will also note prominent
constellations appearing over the eastern horizon at mid-evening each month for
our area for those who would like to learn the constellations. If you have
suggestions for other types of natural information you would like to see added
to this calendar, let us know!
Though we link book references to nationwide sources, we encourage you to
support your local book store whenever possible.
Notes From March 2023
March seemed to squeeze all four seasons of the year into one
month! I gathered data for this image of the Rosette Nebula over four
nights. The first night was beautifully clear but very cold. Temperatures
were in the low 20's with a wind chill in the teens. Four days later, on
the last night, temperatures were in the high fifties.
That last night I stretched out on a lounge chair beside the telescope and listened
to Spring Peepers, American Toads, Pickerel Frogs and Southern Leopard
Frogs calling from the pond next to my house. This is prime time for the
American Toads, and their intertwining songs create a rich harmony that
casts a spell. I also spent a little time looking at the Rosette in
binoculars and star-hopping to a few galaxies.
The Rosette
Nebula, March 19th, 20th, 23rd, ZWO ASI2600 camera and Askar
FRA400 Astrograph Total exposure 3.5 hours
The Rosette Nebula is a cloud of gas and dust about 5,000 light-years away.
It's about 130 light-years in diameter. In the sky it appears about one
degree in diameter, about as wide as two full moons side by side. Like the
Orion Nebula, it is a stellar nursery. As parts of the nebula contract,
the dust and gas are compressed to a point that nuclear fusion can occur
and a star is born.
Many of the bright stars at the center of the Rosette were formed
by this process. The radiation streaming outward from these central stars
has driven away some of the gas in the center of the nebula. This results
in the dark center one sees in the image. This same radiation causes the
gas in the nebula to ionize and glow. In the detail of the full-sized
image below, you can see the small, dark "Bok Globules" of dust and gas
that have been compressed in this process.
Detail from
the full-sized version of the top image showing Bok globules
The Bok globules look a little like gremlins peering into the dark
center of the nebula. They are named after Dutch-American astronomer Bart
Bok. I highly recommend the Wikipedia link to him
here. Bok and his
wife studied the Milky Way for decades. Bok proposed that the globules
were dust clouds that were compressed by the radiation from the cluster's
stars. According to Stephen J. O'Meara in his book ,
The Caldwell Objects, Bok chose to call
them globules because they reminded him of the globules of fat floating in
cream delivered to his home in Belmont,
Massachusetts.
Rosette Nebula
wide field Finder Chart From Sky Safari
Though they look small in the image above, consider that something the
size of our solar system would be entirely invisible at this distance.
Even the tiniest globule that you see could condense into an entire solar
system.
The image above was made using a narrowband Hydrogen alpha filter for the
red channel, a green broadband filter for the green channel and a
narrowband Oxygen III filter for the blue channel, which produces natural
colors but with more contrast than a fully broadband image.
The image at right shows the location of the
Rosette Nebula in the sky. I found it easy to locate by drawing an
imaginary line through the bright "shoulder" stars of Orion and continuing
about the same distance between them to find the faint star 13
Monoceros. Once found, look below it for epsilon Monoceros, which will be
in the same binocular field of view.
NGC 2244, which is the cluster in the center of
the Rosette, will make an equilateral triangle with those two stars. On a
dark moonless night, you can see the glow of the cluster with the naked
eye. In binoculars you can easily see the two roughly parallel lines of
stars at the center of the Rosette. The nebulosity will be colorless and
faint, and will call for careful observation with binoculars.
The star cluster in the center of the
Rosette Nebula has been known since the seventeenth century. Although
individual knots of
nebulosity were noted by William Herschel and others, the knowledge that the nebula
completely encircles the star cluster came only with the advent of photography.
The constellation of Monoceros, the Unicorn,
was not a member of the original 48 constellations created by Claudius Ptolomy.
Ptolemy's constellations date to the second century. Monoceros was added
in 1613 by Dutch geographer Petrus Plancius.
Sky Events for April 2023
Conditions are favorable for the Lyrid Meteor Shower in the
morning hours of April 23rd. Look to the northeast near the bright star
Vega in the constellation of Lyra.
Morning Sky:
Saturn,
Tethys and Dione, June 11th, 2016, 20 Inch Newtonian Reflector and
ZWO Camera. South is up to match the view in an inverting
telescope.
Saturn will
begin April low in the east before sunrise. Try looking for it
around 45 minutes before sunrise about 10 degrees above the horizon. Binoculars will help you get a
good view, as will a flat eastern horizon. Saturn will gradually
climb higher in the morning sky as the month progresses.
Evening Sky:
Bright Venus is climbing higher and higher into the western sky
after sunset this month. Mercury has a particularly good
apparition in April. It reaches greatest elongation from the Sun
on April 11th. Start looking for it about 30 minutes after sunset.
Binoculars are always helpful when looking for Mercury but it
should be easy to see with the naked eye around the 11th. Just
find bright Venus and look between it and the horizon.
Mars will be high in the west this month in Gemini but it is
getting fainter. Its apparent diameter is only about 6 seconds of
an arc, making surface details very difficult to see.
Constellations:
Messier 13, the
Hercules Globular Cluster August 14th, 2014, 12.5 Inch Newtonian
Reflector and
SBIG ST2000XCM camera, total exposure time 80 minutes.
The views below show the sky looking east at 10:15pm EDT on April 15th
from the Chattanooga area. The first view shows the sky with the
constellation outlined and names depicted. Star and planet names are
in green. Constellation names are in blue. The second view
shows the same scene without labels.
Arcturus and
Spica dominate the eastern sky this month.
New constellations are
Serpens Caput, the Serpent (Head), and
Hercules,
the Strongman.
As spring progresses and Hercules rises higher in the sky, look for the
globular cluster Messier 13, which appears like a small fuzzy patch of
light about 1/3 of the distance from Eta to Zeta Hercules (see
the chart below). A cluster of stars about 21,000 light years
away, M13 can be made out with the naked eye in a dark country sky when
the constellation is high in the sky. Binoculars will help pick it
out. In small telescopes you can make out some stars around the edges of
the cluster. It's a beautiful sight in a large telescope, and you can see
a small shadowy three-sided feature (about the 4:00 o'clock position in
the image above) nicknamed "the propeller."
April 15th, 10:15pm EDT, Looking East
April 15th, 10:15pm EDT, Looking East
On Learning the
Constellations:
We advise learning a few constellations each month, and then following them
through the seasons. Once you associate a particular constellation coming
over the eastern horizon at a certain time of year, you may start thinking about
it like an old friend, looking forward to its arrival each season. The
stars in the evening scene above, for instance, will always be in the same place
relative to the horizon at the same time and date each April. Of course,
the planets do move slowly through the constellations, but with practice you
will learn to identify them from their appearance. In particular, learn
the brightest stars (Like Arcturus and Spica in the above scene looking east),
for they will guide you to the fainter stars. Once you can locate the more
prominent constellations, you can "branch out" to other constellations around
them. It may take you a little while to get a sense of scale, to translate
what you see on the computer screen or what you see on the page of a book to
what you see in the sky. Look for patterns,
like the stars that make up the constellation Corona Borealis.
The earth's rotation
causes the constellations to appear to move across the sky just as the sun and
the moon appear to do. If you go outside earlier than the time shown on
the charts, the constellations will be lower to the eastern horizon. If
you observe later, they will have climbed higher.
As each season
progresses, the earth's motion around the sun causes the constellations to
appear a little farther towards the west each night for any given time of night. If you want to see where the constellations in the above figures will be on
May 15th at 10:15pm, you can stay up till 12:15am on the April
16th and get a preview. The westward motion of the constellations is
equivalent to two hours per month.
A good book to learn the constellations is
Patterns in the Sky, by Hewitt-White.
For sky watching tips, an inexpensive good guide is
Secrets of Stargazing, by Becky Ramotowski.
A good general reference book on astronomy is the Peterson
Field Guide,
A Field Guide to the Stars and Planets, by Pasachoff. The book retails for around $14.00.
The Virtual
Moon Atlas is a terrific way to learn the
surface features of the Moon. And it's free software. You can
download the Virtual Moon Atlas here.
Apps:
The Sky Safari 6 basic version is free and a great aid for
the beginning stargazer. I really love the
Sky Safari 6 Pro. Both are available for iOS and
Android operating systems. There are three versions. The Pro is
simply the best astronomy app I've ever seen.
The description of the Pro version reads, "includes over 100 million stars, 3 million galaxies
down to 18th magnitude, and 750,000 solar system objects; including every comet
and asteroid ever discovered."
You may also want to try the very beautiful app
Sky Guide.
Though not as data intensive as Sky Safari, Sky Guide goes all out
to show the sheer beauty of the night sky.
Great for locating the planets.
A
nother
great app is the Photographer's
Ephemeris. Great for finding sunrise, moonrise, sunset and
moonset times and the precise place on the horizon that the event will
occur. Invaluable not only for planning photographs, but also nice to plan
an outing to watch the full moon rise. Available for both androids and iOS
operating systems.
Amphibians:
Fowler's Toad
In addition to earlier breading species like Upland Chorus
Frogs,
Spring Peepers,
Southern Leopard Frogs,
and American Toads,
listen for
Pickerel Frogs,
Fowler's Toads,
Eastern Cricket Frogs and
Gray Treefrogs. I've been hearing Pickerel Frogs this year since the
end of February.
It's a good idea to
listen to the croaking sounds made by Southern Leopard Frogs to avoid confusing
them with the longer snoring calls of the Pickerel Frog.
The early calls of Gray Treefrogs sound raspier than the normal trill, as
if the frog needs to clear its throat. A
fairly new arrival to our area is the Green Treefrog. Don't be too surprised if you see or hear one.
Listen
also on warm days for American Bullfrogs
and
Green Frogs.
Nature Notes Archives: Nature Notes
was a page we published in 2001 and 2002 containing our observations about
everything from the northern lights display of November 2001 to frog and
salamander egg masses.
Night scenes prepared with The
Sky Professional from Software Bisque
