April 2014

Welcome to the inaugural edition of Scope Out Next Month, a monthly newsletter about some interesting astronomical objects and events that can be observed in the month ahead. “Scope Out” is only intended as a clever astronomy pun, and is in no way intended to exclude unaided eye and binocular observation.

CONSTELLATIONS

It is important for observers to learn the constellations, because they help map the locations of the objects and events that are to be observed. Some constellations are bright and easily recognizable even in light polluted skies, while others have many dim stars that can only be seen under dark skies that are usually found only in remote locations. There are several aids that can help locate and identify constellations. I’ll briefly mention some of my favorites before moving on. Wikipedia is a great place to start. It provides great charts, photographs, and descriptions of the constellations that show the observer what to look for when trying to find a particular constellation. Next, a planisphere, or a smartphone app like SkySafari or Google Sky Map are great aids for locating constellations.

First up this month is Orion (The Great Hunter), which is perhaps one of the brightest and most recognizable constellations in the night sky. Once you’ve identified this one once, it will be unmistakable for the rest of your life. Find it by looking southwest right after sunset. The three equally spaced belt stars of almost equal brightness is likely to be the first thing noticed. Next, look for the bright the stars outlining the torso, and be sure to look more closely for the dimmer stars that comprise Orion’s club and shield on either side of his torso. And finally, his dagger is located below the left end of the belt stars. Within the dagger is The Great Orion Nebula, a reddish fuzzy blob. It can be seen can be seen with the unaided eye, but is a very pretty object with magnification.

Next is Canis Major (The Great Dog), which has the distinction of featuring Sirius, the dog star. This is the brightest star in all of the sky. Follow the stars in Orion’s belt to the left to locate Sirius, and the rest of the constellation’s dimmer stars from there. Many of Canis Major’s stars are bright enough to be seen in a light polluted sky. A ‘dog’ can be clearly seen among the dimmer stars in a very dark sky.

Returning once again to Orion and following the belt stars in the other direction this time, the bright reddish star nearby is Aldebaran in the constellation Taurus (The Bull). Aldebaran is part of a distinct V-shaped asterism that represents the face of the bull. Other stars in this constellation can be difficult to locate in light polluted skies. Further to the right, and located within Taurus, are The Pleiades (Seven Sisters). This open star cluster, sometimes mistaken to be the Little Dipper, becomes even more beautiful with even the slightest magnification.

Returning to our Orion base one last time, Gemini (The Twins) is located above and to the left of Orion. Most notable is two rather bright stars, Castor and Pollux, that represent each of the Gemini twins. Gemini is a rather distinct constellation, and most of its stars can be seen easily.

SOLAR SYSTEM OBJECTS.

The Sun is the massive object at the center of our Solar System about which the planets orbit. The Sun is also the source of life sustaining heat and light for our planet, Earth. April begins just over a week after the Vernal Equinox (the first day of Spring), so days and nights are pretty close to equal length at the beginning of the month, but days become noticeably longer as the month progresses.

Look for the Moon at the beginning of the month as a thin crescent just after sunset above and to the left of the sunset point on the horizon. Each subsequent evening the Moon will have moved a little farther east, and away from the Sun. Notice too that the crescent will have grown a little wider each evening. The Moon will reach 1st quarter (right half lit) on April 7th, full Moon on April 15th, last quarter (left half lit) on April 22nd, and finally the new Moon arrives on April 29th.

To the casual observer, the planets are indistinguishable from bright stars. For the purposes of our unaided eye observation, the stars remain fixed in place relative to one another. Even without magnification, planets can be observed to move among the stars as they move along their orbital paths around the Sun. Movement of the planets closer to the Sun, which orbit the Sun faster than the planets that are farther from the Sun, can be detected from one night to the next. The motions of the planets more distant from the Sun can be detected over the course of weeks or months. I have actually seen Venus’ movement over the span of a few minutes through a telescope during the 2012 transit of Venus across the face of the Sun. Even when greatly magnified, stars will never appear as more than a single point of light when observed from Earth. Planets on the other hand, will appear larger with magnification, and a disk can be observed. Features on some of these disks can be observed with sufficient magnification.

Venus appears as a morning star throughout the month. It is the brightest object in the southeastern sky in the pre-dawn hours, above and to the right of the sunrise point. Venus will be just past its greatest separation from the Sun (as viewed from Earth) and brightest magnitude at the beginning of April. It will slowly decrease in brightness as its separation from the Sun decreases as it moves along its orbital. Venus’ phases, which are similar to the Moon’s phases can be observed through a modest telescope. Venus will appear about half lit at the beginning of the month, and about 2/3 lit by month’s end. This change is also as a result of Venus moving along its orbital path.

Mars rises shortly after sunset in the western sky at the beginning of the month, and it will be already above the horizon at sunset by the end of the month. It will appear as a bright and noticeably reddish object in constellation Virgo. Virgo features the bright star Spica, and can be located easily with a planisphere or smartphone app. Virgo, and Mars, will be more easily observed a few hours after sunset, because they will rise higher in the sky over time, just as the Sun rises low in the east, and climbs higher above the horizon as the morning progresses.

Find Jupiter, the most massive of all Solar System planets, high in the sky in the constellation Gemini shortly after sunset. Get a look at it early in the evening, because it will become increasingly more difficult to observe as the evening progresses, because Jupiter is descending downward to the western horizon as the Earth rotates. It is bright and pretty to the unaided eye, but very spectacular with modest magnification. The two dark equatorial bands are observable through most telescopes. A little more than minimal magnification will be necessary to see the Great Red Spot, if it happens to be on the Earth-facing side of Jupiter at the time of observation. Also visible with minimal magnification are Jupiter’s four Galilean moons. All four moons may not be readily visible at any one time, because one or more of them may be either transiting in front of Jupiter’s disk, or be eclipsed behind it. The positions of the moons will change from night to night as they orbit their parent planet. Also note that the moons are always found on a straight line extending through Jupiter’s equator, which is the bright band across the center of the disk (between the two darker ones previously mentioned).

DEEP SPACE OBJECTS (DSOs)

This section is devoted to objects outside of our Solar System. While this description technically includes stars, this topic is about nebulae, galaxies, and star clusters. Most are small and dim, so a telescope is needed to see them. Others can be seen with modest magnification of binoculars or a small telescope. Initially I will limit this newsletter to those visible with the unaided eye, and eventually cover those that can be seen with some magnification. It is important to note that DSOs never appear as bright and colorful to the eye, even when using a amateur telescope, as they do in astrophotographs. This is because camera film (in days past) or sensors can gather light over much longer periods of time than can the human eye. Many of the brighter and more interesting DSOs were cataloged by Charles Messier in the 18th century. Messier objects are assigned an ‘M’ number.

Two DSOs have already been covered in this month’s edition: The Great Orion Nebula (M42), and The Pleiades (M45).

EVENTS

Events come and go, but are interesting to observe. Event durations can vary from an instant to seconds, minutes or days, or even longer. Examples include eclipses, certain planetary arrangements and alignments, meteor showers, and transits of the Sun. One must know when, where, and how to observe an event in the night sky. Most events covered here provide insight into how the Solar System actually works.

April 9th – Opposition of Mars
Mars reaches opposition (in the opposite direction from the Sun when viewed from Earth) on this date, and is closest to Earth on April 14th. A few weeks either side of this date is the best time to view Mars through a telescope, because it appears larger, and more detail can be seen. Polar caps, light and dark features, and sometimes even clouds and dust storms can be observed in larger amateur telescopes.

April 15th – Lunar Eclipse
The full Moon occurs when the Moon is at the point in its orbit on the side of the Earth opposite the Sun. Another way of describing this, is to say that the Earth is directly between the Sun and Moon when the Moon is full (fully lit). The Earth, like all objects upon which sunlight falls, the casts a shadow. This shadow extends into space in the Moon’s direction at full Moon. The Moon usually misses the Earth’s shadow by passing just a little above or below it at full Moon. But the Moon will pass through the Earth’s shadow this month in the early morning hours of April 15th. The Moon enters the penumbra (the lightest part of the Earth’s shadow) at 12:37am EDT, but the best viewing begins at about 2am when the Moon enters the umbra (the darkest part of the Earth’s shadow). Totality occurs when the Moon is completely inside the umbra from 3:06am until 4:27am, at which time it begins to re-enter the penumbra. This stage of the eclipse is the beginning of the Moon’s exit from the Earth’s shadow. The Moon completely exits the umbra at 5:30am, and the eclipse is completely over when the Moon exits the encumbrance at 6:30am.

There are two really neat things to note about the eclipse. First, the “sunset” effect. The portion of the Moon within the umbra will have a distinct reddish cast as a result of the Sun’s rays passing through the edges of the Earth’s atmosphere. As the eclipse progresses, the umbra can first be seen on the eastern edge of the Moon. Over the next hour or so, the portion of the Moon covered by the umbra will grow larger, until the Moon is completely engulfed by the umbra. The reverse will occur as the Moon slides back out of the umbra. Here’s the other neat thing to note. What the observer is actually watching as the Moon passes through the Earth’s shadow is the Moon moving along it’s orbital path around the Earth.

April 16th – 25th – Lyrids Meteor Shower
Named meteor showers occur at roughly the same time each year. Astronomers estimate that the this year’s shower will be somewhat subdued because the Moon brightens the sky, which prevents the dimmer meteors from being seen. All of the meteors associated with the Lyrids shower will appear to come from inside the constellation Lyra. Even though the visible meteor trails are likely to begin outside of Lyra, and the end of the trails will be even farther away from Lyra in every direction, all of visible meteor trails associated with this shower can be traced backward to a common point within Lyra. The shower begins around April 16th and occurs every night through about April 25th. The shower will peak (highest number of meteors per hour) on April 22nd and 23rd. Lyra will rise in the east at about 11:30pm during this period, and can be found by locating its bright star Vega using a planisphere or smartphone app. To observe, be sure to dress warmly and sit in something comfortable, like a reclining lawn chair.

© 2014 James R. Johnson