Sky This Week is brought to you in part by Celestron.
Friday, March 27
The Moon passes the outskirts of the famous Beehive Cluster (M44) in Cancer this evening, standing just north of the center of the open cluster around midnight Eastern Time.
Earlier in the evening, Venus lingers long after sunset, and slowly sinks toward the western horizon. Located at an altitude of about 20°, Venus sets around 9 pm local daylight time as the Sun disappears. At magnitude -3.9 it is very bright, and a great object to enjoy before the sky goes completely dark. (Although be sure to wait to bring out any optics until at least several minutes after the sun has completely set from your location, which may vary from the times listed below.)
Through a telescope, Venus appears almost completely illuminated, with 94 percent of its cloud tops illuminated. (When we look at Venus, we don’t see its surface, but rather its dense, sulfurous clouds.) The planet appears to span about 11″ across the sky and is currently located about 1.58 astronomical units from Earth. (An astronomical unit, or AU, is the average Earth-Sun distance.) Venus is almost on the other side of the Sun from Earth as our two planets orbit, but will be visible in our sky by the end of this year. And Venus orbits the Sun in the same direction, with Venus now trying to “catch up” with Earth, the distance between our planets decreasing as it circles the Sun behind us.
Sunrise: 6:52 am
sunset: 7:20 pm
Moonrise: 1:41 pm
Moonset: 4:08 am
Moon phase: Waxing Gibbous (75%)
*Times of sunrise, sunset, moonrise and moonset are given as per local time from 40° North to 90° West. The moonlight is illuminated from the same location at 10 pm local time.
Saturday, March 28
Today is the best day of the year to see the constellation Corvus the Crow, as it is now located directly in front of the Sun in the sky and remains above the horizon all night.
Around 10 p.m., Corvus is 20° high in the southeast, hanging just below the much larger Virgo to the right. Corvus is a small constellation, covering approximately 184 square degrees and ranking 70th in size among the 88 constellations. But four of its five prominent stars are brighter than (or at all) brighter than third magnitude, making it easier to spot in the sky.
Around 10 a.m., look for bright Spica in Virgo. Look to its right – about 14.5° west of Spica is magnitude 2.9 Delta (δ) Corvi. From here, look 3.5° west to find the magnitude 2.6 gamma (γ) CRV. If you think of Corvus as a box, right now these two stars serve as its tops. At 5.3° south-southeast of Gamma there is magnitude 3.0 Epsilon (ε) Crv, and at 5.7° east of this star we close the bottom of the box with magnitude 2.7 Beta (β) Crv. The fifth star in the constellation lies just 2.1° south of Epsilon: magnitude 4.0 Alpha (α) Crv – despite its designation, the faintest star in the group.
Sunrise: 6:50 am
sunset: 7:21 pm
Moonrise: 2:53 pm
Moonset: 4:43 am
Moon phase: Waxing Gibbous (84%)
Sunday, March 29
The moon passes 0.3° north of Leo’s alpha star, Regulus, at 4 p.m. EDT. By the time it gets dark, our satellite stands about 3.5° east of this bright star.
Shining at magnitude 1.4, Regulus sits almost on the ecliptic – the imaginary line on the sky along which the planets, the Sun and the Moon travel. In fact, draw a line between Regulus and the rising Moon this evening, and you’ll locate the ecliptic almost precisely.
Regulus serves as the basis for the Sickle of Leo, a constellation that is shaped like a backward question mark and is intended to trace the shape of its eponymous form tool in the sky. The top of the sickle’s handle is marked with magnitude 3.5 Eta (η) Leonis, which is 4.8° north of Regulus. The next several stars traverse the blades: magnitude 2.0 Gamma Leo, 4.3° northeast of Eta; magnitude 3.4 Zeta (ζ) Leo, 3.7° north of Gamma; Magnitude 3.9 mu (μ) Leo, 6° northwest of Zeta; and magnitude 3.0 Epsilon Leo, 2.7° southwest of MU. Epsilon marks the tip of the blade.
Many observers also depict the outline of the sickle as a lion’s head, complete with a hairy mane, visible in profile. The figure of the lion is usually drawn with its nose towards the west, back and tail towards the east.
Sunrise: 6:49 am
sunset: 7:22 pm
Moonrise: 4:03 pm
Moonset: 5:12 am
Moon phase: Waxing Gibbous (91%)
Monday, March 30
By local midnight, a familiar summer friend finally arrived on the scene: the surprise star Vega in Lyra. Cataloged as Alpha Lyre, this magnitude 0.0 star is the fifth-brightest Sun in the sky. It forms one point of the famous Summer Triangle asterism, which flies overhead late on summer nights and is anchored at its other two points by Deneb in Cygnus and Altair in Aquila.
You can find Vega more than 10° above the northeastern horizon around local midnight, rising further in the morning. It is the brightest star in this area of the sky, and as spring progresses into summer it will rise earlier each day.
Vega is about twice as massive as our Sun and about 40 times brighter. Despite the fact that it is much younger than our Sun – 400 million years, versus our star’s 4.5 billion – both stars are about halfway through their normal (main sequence) hydrogen-burning lifetimes, thanks to Vega’s higher mass. Higher mass stars evolve more rapidly and live shorter lives.
Vega is particularly unusual because it is oriented in space so that its pole points almost directly toward Earth, so we see it rotating toward us. As it rotates, its shape becomes slightly out of round, making it slightly wider at the equator than at the poles. This causes the poles to become hotter and brighter than the equator, resulting in so-called gravitational darkening. On Vega, because it is tilted toward us, the outer edges (limbs) of the star appear darker than the center (poles).
Sunrise: 6:47 am
sunset: 7:23 pm
Moonrise: 5:11 pm
Moonset: 5:37 am
Moon phase: Waxing Gibbous (96%)
Tuesday, March 31
As the familiar winter constellations begin to set earlier each evening, this is our last chance to capture some of the deep sky treasures they contain.
The Monoceros constellation is located in the sky just east of Orion the Hunter, now dipping in the southwest after dark. You can find it at the upper left of Orion’s belt around 9 a.m. local daylight time. Shining at 6th magnitude, NGC 2301 is an open cluster of young stars located less than 16° southeast of Betelgeuse in Orion and about 5.1° northwest of 4th-magnitude Delta (δ) Monoceros in central Monoceros.
Spanning approximately 12′ across, NGC 2301 is also known as the Great Bird Cluster (or, more fully, the Great Bird of Galaxy Cluster). It was given this nickname Astronomy Contributor Phil Harrington, who imagines the cluster as a bird in flight. Visible through binoculars or a small scope, NGC 2301 consists of about 80 members of varying brightness.
Sunrise: 6:45 am
sunset: 7:24 pm
Moonrise: 6:16 pm
Moonset: 5:59 am
Moon phase: Waxing Gibbous (99%)
Wednesday, April 1
April evening begins with the full moon, which occurs tonight at 10:12 p.m. EDT. The April full moon is also called the Pink Moon after the wild flowers that begin to bloom in abundance as spring begins.
When the Moon is full, deep-sky observations become difficult – but not impossible. Double stars still make excellent targets even in bright moonlight. Tonight, we’re looking northeast of the Moon, located in Virgo, toward the heart of Boots the Herdsman.
The brightest star in Boötes is the famous Arcturus (Alpha Boötis), which shines at magnitude -0.1. We’re traveling about 10.3° to the northeast of this star to find second-magnitude Izar (Epsilon Boo). This Sun splits into two stars about 3″ apart through a telescope – this can be challenging through a small scope, but possible. Larger scopes will make this even easier. The two resulting stars are of third and fifth magnitude and have surprisingly contrasting colors. Most observers see them as gold and blue. However, some people think they appear more golden and green – note that this is a trick of the eye, as there are no green stars.
The pair was considered so lovely by astronomer Friedrich Georg Wilhelm von Struve that he called it Pulcherrima – “most beautiful” in Latin. What do you think?
Sunrise: 6:44 am
sunset: 7:25 pm
Moonrise: 7:21 pm
Moonset: 6:20 am
Moon phase: full
Thursday, April 2
You’ll want to keep an eye on Jupiter this evening as Europa passes north of Callisto while Ganymede’s large shadow crosses the gas giant’s cloud tops. Begin observing at 11 p.m. EDT, as the bright planet hangs in the west just below the heads of Gemini’s twins: Castor and Pollux.
At that time, Ganymede’s shadow was already crossing the tops of the clouds, having begun its journey an hour earlier (so feel free to start looking at it if you’re able!). Ganymede itself lies to the west of the planet, with Io further west. On Jupiter’s eastern side, Europa and Callisto are close to each other, with Europa just east of Callisto. This is where you’ll want to look: Both are moving west, toward the planet, but Europa is moving faster. At 11:30 PM EDT, the smaller moon moves north of Callisto, leaving the two 7″ apart. After that, Europa will overtake its companion moon, moving closer to Jupiter as Callisto lags behind.
Ganymede’s shadow transit also continues, ending shortly after 1:22 a.m. EDT, now on April 3 for the eastern half of the Americas — where the view is also diminished due to Jupiter’s lower position. The western part of the US gets a better view as Ganymede’s shadow reaches Jupiter’s western limb and disappears.
Sunrise: 6:42 am
sunset: 7:26 pm
Moonrise: 8:24 pm
Moonset: 6:41 am
Moon phase: Waning Gibbs (99%)
Friday, April 3
Today at 7 pm EDT, Mercury has reached greatest western expansion, standing at 28° from the Sun.
Now visible in the morning sky, the tiny planet shines at magnitude 0.4 and rises around 5:45 a.m. local daylight time. It doesn’t take long to see it, but early risers can see it about 4° above the eastern horizon about half an hour before sunrise. Mercury is now in Aquarius and is currently tracking east, or moving opposite the background stars.
Through a telescope, the planet’s disk extends 8″ across the sky. It’s about half illuminated (49 percent) and its brightness will increase over the coming days as Mercury remains about the same height above the horizon, while Mars and Saturn slowly rise to meet it in the morning sky. Currently, Mars is above the horizon a half-hour before sunrise, but barely — the red planet is only 1 degree higher at the moment and much fainter at 1.3 magnitude. You You can try to see it in binoculars or a telescope at 9.1° north-east of Mercury (below Mercury), but you will need a very clear horizon free of trees or buildings. Take care to remove any optics before sunrise from your location, which may differ from the time shown below.
Sunrise: 6:40 am
sunset: 7:27 pm
Moonrise: 9:29 pm
Moonset: 7:05 am
Moon phase: Waning Gibbs (96%)
