Saturday, April 30, 2016

Tonight's Sky for April 30: Third Quarter Moon


Today, the Moon, second brightest object in the sky, has reached the Third Quarter phase, which means that it is exactly 270 degrees around its orbit of Earth.

As for lunar mechanics, the Moon is always half lit. The reason we don't always see it as such is thanks to orientation in relation to us. Right now, with the Moon at a 90 degree angle relative to the Earth and Sun, we see the Moon as half lit and half dark, leading to the popular, erroneous phrase 'half Moon.'

After today, we will see less and less of the Moon as its lit side turns more away from us and heads toward a new lunar cycle.  
 

Friday, April 29, 2016

Tonight's Sky for April 29: Be Alert for Aurora

Tonight into tomorrow, the Earth will be making a solar sector boundary crossing, a fancy way of saying that the Earth will be moving through regions of opposite magnetic polarity. Result: NOAA is forecasting a 60% chance or aurora for high-latitude dwellers, which is a good reason to keep an eye on the sky tonight. 

Thursday, April 28, 2016

Tonight's Sky for April 28: 5 Planets in Retrograde

Starting today, 5 planets will be in retrograde motion, a first in over a decade. Mercury, Mars, Jupiter, Saturn, and Pluto (still a planet in the heart and minds of many) are now, at least as seen from Earth, moving backwards relative to their regular motion against the stars. Why does this happen?It's all an optical illusion caused by a faster planet overtaking a slower one. A real life comparison is when passing a slower car on the highway when the car you're passing appears to fall behind you even though both cars are moving forward. 

Oh yes, this won't cause any crazy Earthly goings-on, either!

Wednesday, April 27, 2016

Tonight's Sky for April 27: Mars is 15 Arc Seconds Across

Mars may be over a month away from opposition, the point in its orbit where it is opposite the Sun as seen from Earth and also the point in its orbit where it appears the brightest as seen from Earth, but that doesn't mean that the Red Planet isn't already putting on a show. As of now, Mars appears to be 15 arc seconds across, 3 arc seconds shy of its peak of 18 arc seconds that will occur at opposition. For comparison, thanks to orbital geometry, this is already as big as Mars got in the 2014 opposition, wherein Mars peaked at 15 arc seconds.

Monday, April 25, 2016

Tonight's Sky for April 25-26: Mars and Saturn at their Closest



This and tomorrow morning, the Moon will be making a pair of close passes with two planets and one of the brightest stars in the sky. This morning, the Moon will be sitting almost directly above Mars and Antares. Tomorrow morning, the Moon,Saturn, and Mars will be in an almost straight line.


Additionally, on the 25th, Mars and Saturn will be at their closest, or at least until Mars quits retrograding.

Saturday, April 23, 2016

Tonight's Sky for April 23: Lyrid Meteors Peak


Today will mark the peak of the Lyrid Meteor shower for 2016, thus marking the climax for the 2-week event. Every April, Earth passes through the stretch of space junk shed by Comet C1861 G Thatcher, reaching the deepest concentration of debris tonight. According to some estimates, under ideal conditions (dark country skies), one can expect to see 15 meteors per hour. The reason the meteors are called Lyra is because the meteors seem to radiate from the constellation Lyra. The best time to view the shower is in the wee hours of the morning, as Lyra is at its highest then.

Don't want to stay up that late? Don't worry, Lyra clears the Eastern horizon around midnight and will climb higher as the night progresses. However, unless one lives out in the country, the early post-midnight hours will probably involve Lyra being low in a light dome. To improve odds of seeing meteors, travel out of the city and to the country if you can. In the suburbs, just going from the front to back yard can make a dramatic difference as this will eliminate glare from those pesky street/house lights to a large extent.

Unfortunately, this year's Lyrid peak coincides with the Full Moon, which means that nature's night light will be at its brightest and up all night. The good news: even the Moon won't be able to outshine the brightest meteors. 

Friday, April 22, 2016

Tonight's Sky for April 22: Full Apogee Moon

Tonight, the Moon will reach its full phase, which means that, as seen from Earth, it is directly opposite the Sun in the sky as seen from Earth and is at the half way point in its current orbit.

As for lunar mechanics, the Moon is always half lit. The reason we don't always see it as such is thanks to orientation in relation to us. Right now, when the Moon is opposite the Sun and on the far side of Earth, we can see all of its lit side, which is why it appears to be “full.” In the coming nights, we will start to see less of the Moon as its lit side starts to turn away from us as seen from Earth and heads toward Third Quarter.

In addition, this will be, in terms of angular size, the smallest Full Moon of the year. Why? The Moon is at apogee, a point in its orbit that is farthest from Earth.


What many people may not realize is the fact that the Moon (and all other celestial bodies) do not orbit their parent bodies in circles, but ellipses, which are slightly elongated circles. Result: any given day of an orbital period, any orbiting body will be at a slightly different distance from its parent body. As for the Moon, this variance in orbit amounts to about 20,000 miles.

As for tonight, the Moon will be about as far from Earth as it is going to get. When it comes to practical implications, the difference will be hard to notice with the naked eye to all but an experienced observer but, in a telescope, the difference will be obvious

Thursday, April 21, 2016

Tonight's Sky for April 21: Moon at Perigee

Tonight, the Moon is about as big as it will ever get thanks to the fact that the Moon is at perigee, a point in its orbit that is closest to Earth.


What many people may not realize is the fact that the Moon (and all other celestial bodies) do not orbit their parent bodies in circles, but ellipses, which are slightly elongated circles. Result: any given day of an orbital period, any orbiting body will be at a slightly different distance from its parent body. As for the Moon, this variance in orbit amounts to about 20,000 miles.

As for tonight, the Moon will be about as close to Earth as it is going to get. When it comes to practical implications, the difference will be hard to notice with the naked eye to all but an experienced observer but, in a telescope, the difference will be obvious

Wednesday, April 20, 2016

Tonight's Sky for April 20: Corvus Flies South at Midnight


Tonight at midnight, the small, trapezoid-shaped constellation of Corvus the crow is due South. To find Corvus, follow the arc of the Big Dipper's handle to Arcturus, alpha Bootes, speed onto Spica (alpha Virgo), and continue the curve to Corvus, which should be easy to spot as all of its main stars are in the 2nd magnitude, albeit the dimmer half.

Tuesday, April 19, 2016

Tonight's Sky for April 19: Venus Rises 30 Minutes Ahead of the Sun

Anyone wanting to view Venus had better hurry as the bright planet is only rising 30 minutes ahead of the Sun now. Even for the bright Venus, trying to find the planet this close t the Sun will probably require optical aid.

Monday, April 18, 2016

Tonight's Sky for April 18: Mercury at its Best

Want to join a small club of people who have seen the planet Mercury? Well, here's your chance as the first planet from the Sun will be making its best appearance of the fall this morning.

Of all the Classical Planets (those known to the Ancient Greeks and Romans), Mercury is by far the hardest to spot because, as seen from Earth, it never gets very far away from the Sun. As a result, Mercury is often obscured from view by the Sun's glare.

As of today, Mercury has reached a point in its orbit called greatest elongation, which is a fancy way of saying that, as seen from Earth, Mercury is as far from the Sun as it will get on this orbit and making its best morning appearance of the year. How good is it? So good that Mercury sets about an hour and a half after the Sun! So good that, even 30 minutes after sunset, Mercury is still about 10 degrees up from the horizon. To simulate, hold your fist vertically at arm's length. While that may not seem overly high, for elusive Mercury, that's quite good.


So, take a moment or two, go out just before dawn, and try to spot Mercury. If you are successful in spotting the speedy planet, you are accomplishing something that the great astronomer Nicolaus Copernicus (who rediscovered the idea of a sun-centered solar system) supposedly never did. 

Saturday, April 16, 2016

s Sky for April 16-17: The Moon and the Kings



 April 16


April 17

Tonight and tomorrow night, the Moon will be meeting up with a pair of celestial kings. Tonight, the Moon will be parked right next to Regulus, the blue alpha (brightest) star of zodiac constellation Leo the Lion. Perhaps because it is the heart of the lion, Regulus is known as “the King Star” even though is is nowhere near being the brightest star in the sky. Tomorrow night, Luna will be parked right next to Jupiter, king of the planets, too.  

Friday, April 15, 2016

Tonight's Sky for April 15: Mars Stationary

Tonight, Mars will appear stationary as seen from Earth. In the past month and a half, Mars has noticeably been moving closer to Saturn. However, come tonight, that will change as Mars will begin its period of retrograde motion, during which it will appear to move forward with the stars and pull away from the ringed planet. While the change in motion will not be immediately noticeable, come a couple of weeks, there will undeniably be distance opening up between the planets.

Thursday, April 14, 2016

Tonight's Sky for April 14: Moon Meets the Snake and Bees


Tonight, the Moon will be near a pair of objects that herald the changing of the seasons from winter into spring: the cosmic snake and bees. The key to the whole show is the Moon. Luna found, look below it for an oval shape of 5 stars, which represent the head of Hydra, the mythological water snake that is also the largest of all 88 constellations, snaking (sorry) its way through over 100 degrees of sky. Hydra found, hop back up straight to the Moon and, now grabbing binoculars, to a spot about the same distance above the Moon that Hydras head was below. If you're on target, you'll see a fuzzy patch of sky in small binoculars and even individual stars in large ones. What is this patch? It's the Beehive Cluster, also known as M44, one of the largest open clusters in all the sky. 

Wednesday, April 13, 2016

Tonight's Sky for April 13: First Quarter Moon

Today, the Moon, second brightest object in the sky, has reached the First Quarter phase, which means that it is exactly 90 degrees around its orbit of Earth and is one quarter finished with its current orbit..

As for lunar mechanics, the Moon is always half lit. The reason we don't always see it as such is thanks to orientation in relation to us. Right now, with the Moon at a 90 degree angle relative to the Earth-Sun line, we only see half of the lit side.

After today, we will see more of the Moon each night as its lit side turns more toward from us and heads toward Full in a week. 

Tuesday, April 12, 2016

Tonight's Sky for April 12: Cosmic Soccer, Pollux?


Tonight, there will be a bit of cosmic soccer, of sorts, as the Moon will be parked right next to the cosmic twins, Gemini, and more specifically, next to the foot of Pollux, the lower of the twins as seen when the constellation is just starting to rise in the East. As a second activity, if you have a telescope handy, turn it on Castor, the other twin as it is a binary (multiple) star system and see how many of the companion stars you can spot. For the record, Castor is a 6-star system. 

Monday, April 11, 2016

Tonight's Sky for April 11: Growing Sunspot AR2529

The Sun's blank surface has been not much to look at for the past few weeks but that has changed in a big way this past weekend as sunspot AR2529 has ballooned in size over just the past couple of days, growing from a small dot into a behemoth the size of Neptune. So, if you have solar viewing glasses or a solar filter for your telescope, be sure to take a look. The best part: the sunspot is still growing.

Sunday, April 10, 2016

Tonight's Sky for April 10: Moon Meets the Hyades


This evening, the Moon will meet up with the Hyades, one of the closest and most prominent star clusters. To see the show, simply go outside and find the Moon. That done, look for bright orange Aldebaran, the brightest star in the cluster as well as in the whole constellation of Taurus. To get a full appreciation of the sight, turn even a pair of small binoculars on the Moon to reveal the dozens of stars in the cluster.

Saturday, April 9, 2016

Tonight's Sky for April 9: Uranus at Superior Conjunction

Today, the planet Uranus has reached superior conjunction. What does that mean? In layman's terms, Uranus will be directly opposite the Sun as seen from Earth in a Uranus, Sun, Earth alignment. End result: the planet will be at its worst point for viewing. For the record, since it is a superior planet, Uranus can only have a superior conjunction as it will never come directly between Earth and the Sun.

Friday, April 8, 2016

Tonight's Sky for April 8: Young Moon Meets Mercury


How thin of a Moon have you seen? How about one that's just barely over 1 day old and only 4% illuminated? Well, if you have never seen a Moon this thin, this is your chance to do so as such a Moon will be making an appearance in this evening's sky just after sunset.

To see the Moon, you'll need a good Western horizon. How good? One with less than 10 degrees of obstruction. To simulate this, hold your fist vertically at arm's length to simulate 10 degrees. Hint: if you can't think of a good location off-hand, scout out one during the day. Location found, head there at sunset and start looking, preferably with optical aid, and start scanning the sky. The Moon may not be visible at first, often seeming to suddenly pop into visibility as if it were flipped on like a light.

Believe me, when this happens, it's an exhilarating experience.


Additionally, Mercury is nearby, too. 

Thursday, April 7, 2016

Tonight's Sky for April 7: Apogee New Moon

Today, the Moon, second brightest object in the sky, has reached the New Moon phase, which means that it is directly between the Sun and Earth, and thus invisible for us Earthlings as of now.

As for lunar mechanics, the Moon is always half lit. The reason we don't always see it as such is thanks to orientation in relation to us. Right now, with the Moon directly between the Earth and Sun, e can't see any of its lit side.

After today, we will see more of the Moon each night as its lit side turns more toward from us and heads toward first quarter.

Additionally, the Moon is at apogee, which means that the Moon will be about as far from Earth as it is going to get. When it comes to practical implications, the difference will be hard to notice with the naked eye to all but an experienced observer but, in a telescope, the difference will be obvious

Wednesday, April 6, 2016

Tonight's Sky for April 6: Old Moon Meets Venus


How thin of a Moon have you seen? How about one that's just barely a day before New and only 2% illuminated? Well, if you have never seen a Moon this thin, tonight's your chance to do so as such a Moon will be making an appearance in this morning's sky just before sunrise.

To see the Moon, you'll need a good Eastern horizon. How good? One with less than 3 degrees of obstruction. To simulate this, hold two fingers vertically at arm's length to simulate 3 degrees. Hint: if you can't think of a good location off-hand, scout out one during the day. Location found, arrive there just before sunrise and start looking with optical aid, even a pair of cheap 7x50 binoculars will work here. The bad news: you'll have to hurry because, as soon as the Sun clears the horizon, you can forget about seeing the Moon.

Additionally, Venus is nearby and can serve as a useful finder to help locate the Moon, too. 

Tuesday, April 5, 2016

Tonight's Sky for April 5: Mercury at Perihelion

Today, Mercury is as close as it will ever to from the Sun thanks to the fact that it is at perihelion, a point in its orbit that is closest to Sun.

What many people may not realize is the fact that Mercury (and all other celestial bodies) do not orbit their parent bodies in circles, but ellipses, which are slightly elongated circles. Result: any given day of an orbital period, any orbiting body will be at a slightly different distance from its parent body. As for those planetary distances taught in schools, they're the planet's average distance from the Sun.


Additionally, Mercury is as fast as it will get today, too. Why is this? As a planet locked in an orbit gets closer to the Sun, the Sun's gravitational force on the planet increases and the planet will speed up. Then, as the planet rounds the perihelion point and begins to move farther away from the Sun, its speed will decrease as the distance to the Sun increases, culminating at minimum speed at, you guessed it, aphelion. This fact was first discovered in the early 1600s by Johannes Kepler and serves as his 2nd law of planetary motion.  

Monday, April 4, 2016

Tonight's Sky for April 4: Project Ozma Begins (1960)

It was on this date in 1960 that the first search for alien radio signals commenced. Working at the Green Bank Radio Observatory, a then-29 year old Frank Drake was inspired to point a radio telescope at Sun-like stars after reading a paper in the journal Nature that speculated that radio signals from an alien civilization could be detected with radio telescopes on Earth. For his project, Drake pointed an 85-foot radio dish at two stars for 6 hours a day from April to July, 1960, with no results. While modest, this first search for extraterrestrial intelligence (SETI) would lead to much bigger, more ambitious searches that continue to the present. 

Sunday, April 3, 2016

Tonight's Sky for April 3: Continued Chances for the Northern Lights

Yesterday, the Earth entered a turbulent stream of the solar wind, which makes for increased chances of aurora, also known a the Northern Lights. After spectacular displays of high-latitude aurora last night, NOAA is forecasting a 55% chance of more geomagnetic storms, and hence aurora, today. So, if you live at a high latitude and have a clear sky, be sure to look up tonight!

Saturday, April 2, 2016

Tonight's Sky for April 2: Weekend Aurora Alert


NOAA is forecasting a 60% chance of geomagnetic activity tonight and into tomorrow morning as the Earth will be entering a co-rotating interaction region (CIR), which is a fancy way of saying that the Earth will be transitioning from being in a fast to slow stream of the solar wind. Such transition zones are often good for sparking displays of aurora, also known as the Northern Lights. 

Friday, April 1, 2016

The April Sky, Tonight's Sky for April 1


With the new month of April here, the lengthening of the days will continue at a brisk pace as the equinox is still within recent memory, which means that, for the first time of the new year, staying up late to observe under truly dark skies will become a chore for many. On the good news front, April is usually the first month of the year where the persistent winter clouds and cold finally loosen their grasp after months of winter weather, revealing the stunning celestial sights that had been so often shrouded in clouds for the first 3 months of the year in no longer bone-chilling temperatures.

Cool Constellations
If March was the last time to see many winter constellations under dark sky conditions, April is the last chance to see them, period. So, come sundown, look low in the West-Southwest for Cassiopeia, Cepheus, Perseus, Orion, Canis Major, and Canis Minor. A few later/more Northerly winter constellations, including Auriga, Taurus, Gemini, and the Pleiades are now in that twilight zone where one needs to observe them under dark skies now or miss them for the year. By the time April rolls around, the Big Dipper signpost to the stars is well up for all to see. Starting at the Dipper, follow the arc of the Dipper to bright orange Arcturus, alpha Bootes, and the brightest star in the spring sky. To the left of the kite-shaped Bootes, look for the arc of stars that is Corona, the crown. Next, speed onto blue Spica, alpha Virgo, and one of the brightest spring stars. Next, continue the curve to trapezoidal constellation Corvus, the crow. Finally, conclude in dim Crater the cup. Moving higher in the sky, zodiac constellations Cancer and Leo are well-placed as well. Speaking of Cancer, look just below the cosmic crab for a distinct ring of stars, the head of Hydra, the sky's biggest constellation, which snakes (sorry) through over 120 degrees of sky. For those who like to stay up late (or get up extremely early), there's mythological strongman Hercules and the Summer Triangle high overhead and, to the South, Ophiuchus, Serpens, and Scorpius. However, unlike in previous months, the later time of year will not bring new predawn constellations thanks to the Sun, which is rising ever earlier in the morning.

Planetary Perceptions
On the planet front, the big highlight is Mercury, which is making its best evening appearance of the year mid-month. Visible all month, itself rare, Mercury will peak in apparent height on April 18 in the Western sky just after sunset. How good is this apparition? So good that, even half an hour after sunset, Mercury is still well over 10 degrees above the horizon (hold a fist at arm's length to simulate 10 degrees). Additionally, at its best, Mercury will set almost two hours after the Sun. Moving into the night, Jupiter, which reached opposition on March 8 is still up just about all night. By month's end, Jupiter is just about crossing the Meridian, and is hence at its highest, as the sky finally gets dark. Later in the night, Mars is next to break the horizon, albeit in middle of the night, followed closely by Saturn. An item of note: Mars is still converging with, but not as fast as last month. Still, Mars and Saturn will continue to converge until their closest meeting takes place at month's end. Additionally, Mars will appear stationary mid month, after which it will eventually begin to retrograde and move forward with the stars through June. Moving to the immediate predawn sky, it's now or never (or at least until evening reappearance) to catch Venus, hangs very close to the predawn Eastern horizon and will be nearly impossible to spot by month's end.


Tonight's Sky for April 1: Mercury Rising
Mercury is on the rise and this has nothing to do with the trend of warmer temperatures. Right now, Mercury is low in the Western sky immediately after sunset. However, as the month progresses, Mercury will climb higher and higher in the Western twilight, peaking in height mid month. Still, why not start looking now?