Thursday, July 31, 2014

Tonight's Sky for July 31: Scorpius Due South at Dusk


It's mid summer now and there is a great sight bearing out this fact: the Zodiac constellation of Scorpius is due South at dusk. To see it, simply head out and look South about an hour after sunset for the bright red star Antares (the scorpion's heart), which rides low in the Southern sky. As the twilight disappears, the full constellation will pop into view, horizon-allowing. 

Wednesday, July 30, 2014

Tonight's Sky for July 30: Mercury at Perihelion


Tonight, the planet
Mercury, first rock from the Sun, is at perihelion, a point in its orbit that is closest to the Sun.


What many people may not realize is the fact that the Mercury (and all other celestial bodies) do not orbit their parent bodies in circles, but ellipses, which are slightly elongated circles with the Sun slightly offset from the center. Result: any given day of an orbital period, any orbiting body will be at a slightly different distance from its parent body. As for Mercury, it is about 28.5 million miles from the Sun right now as opposed to its average distance of about 36 million miles, meaning that its orbit varies by about 7.5 million miles either side of the average, meaning that Mercury's orbit takes it out to about 43.5 million miles at aphelion (farthest point from the Sun).

For the record, Mercury has the greatest eccentricity (deviation from a circle) of any of the 8 planets relative to its orbital size. 

Tuesday, July 29, 2014

Tonight's Sky for July 29: Delta Aquarid Meteors Peak


Today, the Delta Aquarid Meteor Shower is set to come to a peak, thus kicking off 'meteor season,' which culminates with the Geminids in December.

Every July, Earth passes through the stretch of space junk, reaching the deepest concentration on the night of the 29th. According to some estimates, under ideal conditions (dark country skies), one can expect to see 10-15 meteors per hour on peak night. The best time to view is in the hours just before dawn as Aquarius is at its highest then, albeit still rather low in the South. To improve odds of seeing meteors, travel out to the country to escape suburban/urban light domes.

Fortunately, the Moon is near New, which is ideal as this means that the Moon will be out of the way, and thus unable to out-shine the meteors, for this year.


Monday, July 28, 2014

Tonight's Sky for July 28: Apogee 'Young' Moon



How thin of a Moon have you seen? How about one that's just 2 days old and only 4% 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 evening's sky just after sunset.

To see the Moon, you'll need a good Western horizon. How good? One with less than 5 degrees of obstruction. To simulate this, hold your middle three fingers vertically at arm's length to simulate 5 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. The good news, if you have binoculars, you should be good to go, just remember to be patient as the Moon will often appear to suddenly pop into view out of thin air. On the other hand, if you're still looking 30 minutes after sunset, you missed the Moon.

Another point of note: today, the Moon is at apogee, the point in its orbit farthest from Earth. 

Sunday, July 27, 2014

Tonight's Sky for July 27: Flat Ecliptic


The 25th was Old Moon, the 26th New Moon, which should make the 27th a Young Moon. Well, sort of because the Moon is technically Young today but it will be impossible to see from Earth thanks to the fact that the ecliptic plane is so low relative to planet Earth, which means that the 1% illuminated Moon will be setting less than 10 minutes after the Sun, and thus impossible to see. So, why does this happen?

Again, it all has to do with cosmic geometry, namely the Earth's 23 inclination relative to its axis. This is the same reason we have seasons. In summer, the Earth is tilted away from the ecliptic plane as seen from Earth and in winter, it is tilted towards the ecliptic.

As another interesting observation, the ecliptic and Sun are at opposite extremes in height at opposite times of year, too. 

Saturday, July 26, 2014

Tonight's Sky for July 26: 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 us and the Sun, we don't see any of the lit side, thus making the Moon invisible to us as seen from Earth.

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

Friday, July 25, 2014

Tonight's Sky for July 25: Old Moon Meets Mercury


Want to see the planet Mercury but don't know where to look? Well, you're in luck this morning as the waning crescent Moon will be parked right next to Mercury. To see the show, simply go out in the predawn sky, look East and find the Moon and that bright “star” next to it. The Moon is the Moon, of course and that “star” is Mercury, first planet from the Sun and the hardest to see of the Classical Planets. Unlike last morning, optical aid could be required to catch this celestial meet-up thanks to Mercury's dimness, the Moon's 2% illumination, and closer proximity to the Sun.

As an added bonus, impossible to miss Venus will be above this morning's pairing.
 

Thursday, July 24, 2014

Tonight's Sky for July 24: Moon Meets Venus


Want to see the planet Venus but don't know where to look? Well, you're in luck this morning as the waning crescent Moon will be parked right next to Venus. To see the show, simply go out in the predawn sky, look East and find the Moon and that bright “star” next to it. The Moon is the Moon, of course and that “star” is Venus, second planet from the Sun, closest planet to Earth, and third brightest object in the sky after the Sun and Moon. As an added bonus, Mercury will be below today's pairing.

Wednesday, July 23, 2014

Tonight's Sky for July 23: Earth's Near Miss (2012)


It was two years ago that Earth had a close shave with an event that could have sent the world back to the preindustrial age. What was this near catastrophe caused by, a comet? An asteroid? Neither: try a solar 'superstorm.'


It was on July 23, 2012 that an extraordinarily powerful coronal mass ejection (CME) blasted through Earth's orbit. For the record, this violent episode of space weather was estimated to have been as powerful as the legendary Carrington Event of 1859, which was so powerful it caused spectacular displays of aurora as far South as Hawaii and telegraph lines to emit sparks and even burst into flames. So why don't we remember this event that took place just two years ago?

Two words: it missed.

While solar flares and resulting CMEs don't harm any living things, the energy they release can wreak havoc on all sorts of electronic devices. At the time of the Carrington Event, the only real major electrical device in existence was the telegraph, which got fried. Now, if such an event were to hit, you might have to forget about using every electronic device you own because there would be a good chance of it becoming high-tech toast, the possibility of which should serve as impetus for further R&D efforts into protecting our electronics, upon which the world is now largely dependent.  

Tuesday, July 22, 2014

Tonight's Sky for July 22: Moon Meets the Bull's Horns


Tonight, the Moon will be in a very unique place: right between the horns of a cosmic bull. Tonight, the Moon will move directly into the Zodiac constellation of Taurus the bull, more specifically, between its horns.

To see the sight, go out and look East in the predawn sky before the sky starts to brighten. The Moon, of course, will be impossible to miss. Moon found, look for a sideways 'V' of stars, the Hyades star cluster, which represent the base of the bull's horns. Extending the lines of the 'V' out, you will run into a pair of stars of roughly 2nd magnitude (though on opposite ends of the scale) that signal the end of the horns.


Cosmic picture realized, there's the Moon, smack in the middle. 

Monday, July 21, 2014

Tonight's Sky for July 21: All Quiet on the Sun


Remember a few months ago when the Sun was popping off flares one after the other? Well, nothing could be farther from the truth now as the Sun has not experienced any major activity in 6 days. What are the chances for a solar flare today? Well, according no NOAA, less than 1%. The good news: if you have a hydrogen alpha filter, there's still stuff to see! 

Sunday, July 20, 2014

Tonight's Sky for July 20: Neil Armstrong Steps onto the Moon (1969)

It was 45 years ago today for us in the United States (your anniversary may be tomorrow depending on your location) when Neil Armstrong became the first human to ever set foot on another world when he took his “giant leap for mankind.”Needless to say, the only explanation this needs is that we did go to the Moon and the Apollo Conspiracy Theories are full of holes.

Saturday, July 19, 2014

Tonight's Sky for July 19: Venus Rises 2 Hours Before the Sun


Venus has been putting on a good show in the predawn sky for the spring and summer, remaining largely stationary in the sky for several months. However, as always happens, the show won't last forever and, right now, Venus is starting to sink towards the Sun, with it now rising just 2 hours ahead of our nearest star this morning. The good news: Venus will remain visible for about another 2 months, so there's no rush to see it just yet!

Friday, July 18, 2014

Tonight's Sky for July 18: Third Quarter Moon Meets Uranus

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.

As a bonus, the Moon will be very near Uranus tonight. To help find the planet, refer to the sky chart below. The good news: while Uranus is dim, it has a very un-star like color: teal, which serves to betray its true identity.

Good luck with planet hunting!

Thursday, July 17, 2014

Tonight's Sky for July 17: Saturn Sets 5 Hours After the Sun


Saturn is sinking, but don't panic! Tonight, the ringed wonder, which reached opposition on May 10, will now be setting 5 hours after the Sun, meaning that Saturn will be well placed for viewing in the South-Southwestern sky as the sky gets dark. To see Saturn, look about a third of the way up from horizon to zenith (straight up) about an hour after sunset. That bright 'star' is, in fact, the planet Saturn. For more fun, bring out the telescope as even a 60mm department store scope will clearly reveal the planet's rings. Bigger scope? Bigger detail!

Tuesday, July 15, 2014

Tonight's Sky for July 15: Comet Shoemaker-Levy 9 Hits Jupiter (1994)


On this date 20 years ago, telescopes all over the world were trained on the planet Jupiter, which was about to experience the first in a week-long series of impacts caused by tidally torn Comet Shoemaker-Levy 9. Going into the event, about the only things that were known was that this would be the first impact event ever to be witnessed by scientists and that no one really knew what would happen when the comet 'impacted' the gassy planet.

What did happen was spectacular.

On July 16, 1994, the first in a series of more than 20 fragments hit the planetary king, creating a large fireball and leaving a dark black area of gasses at the impact site. In time, Jupiter would come to have a virtual necklace of impact sites in its Southern Hemisphere, which also went on to have serious impact here on Earth in that, for the first time, the threat of planetary collisions from large objects shooting through the solar system was taken seriously.  

Monday, July 14, 2014

Tonight's Sky for July 14: 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 is making its best summer appearance right now in the predawn sky.

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 yesterday (but delayed due to the Spica-Mars conjunction), 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 rises about an hour and a half before the Sun! So good that, even 30 minutes before sunrise, 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. 

Comets


The rarest of all celestial visitors visible to the naked eye, comets are capable of, by far, the most variety. When one hears the word 'comet,' the thought of a long-tailed object comes to mind. Yes, while comets can look like this, these 'great comets;' are exceedingly rare. To illustrate, the last great comet, McNaught (above), was visible in 2006-7. Before that, Hale-Bopp (1997) was the last great comet. While there was Hyakutake the year before in 1996, Halley's Comet's 1986 appearance was the last great comet before that. Just by looking at these examples, the pattern becomes obvious: great comets are, on average, a once a decade event. 



Now, while not all comets are the pop culture image great comets present, they are fun to look at. With the naked eye, comets can be visible as diffuse fuzzball-like objects in the sky. In binoculars and telescopes, comets can take on a lot more detail, especially in regards to color. For comets, the most common color is a greenish blue, which can be extremely delightful to look at in the telescope as there are no green objects in the sky.

Another interesting point to comets is that they are unpredictable. While forecasters will make predictions about what any given comet will do months in advance of its arrival, comets often have other ideas. A prime example of this was Comet Holmes in 2007, which morphed from a small, normal binocular/telescopic comet just on the edge of naked eye visibility into a massive body as large as the full Moon. The same can be said of Comet McNaught. While bright, no one could have ever expected it to erupt a sky-spanning tail after making its close passage to the Sun. To the contrary, in 2013, the much-hyped Comet ISON promptly disintegrated upon close approach to the Sun. To say the least, comets are true cosmic wild cards that are always worth a look.  

The Moon


Diameter: 2,160 miles
Volume: .02 Earth
Gravity: 0.16x Earth
Distance from Earth: 238,000 miles
Orbital Period: 27.32 days
Orbital Inclination: 5.18 degrees
Orbital Eccentricity: .055
Length of Day: 27.32 days
Temperature: -387 to 253F
Composition: Rock, silicates
Atmosphere: none
Notable Exploration: Apollo 11-17 (1969-72), Lunokhod Rovers (1969-77), LRO (2009-present), LCROSS (2009), Yutu (2013-present)

Of all heavenly bodies, the Moon is perhaps the most fun to observe with the naked eye thanks to the fact that it changes phases and because one can actually see surface features without optical aid.




When it comes to Moon's phases, they are actually very easy to explain. Although it may not always appear so to us, the Moon is always half lit. What we can see and when we can see it depends on where the Moon is in its orbit relative to the observer. To explain what is happening, let’s take a trip around the Earth by way of the Moon. A total orbit of the Moon around the Earth takes about 29 days. At new Moon, the alignment is Sun, Moon, and Earth in that order and in a straight line. From the Earth, the Moon is lost in the glare of the Sun, hence why we cannot see it. As the days progress, the Moon will move out of the Sun’s glare and the Sun will set before the Moon. In the days just after new Moon, from the Earth, we will begin to see a tiny bit of the lit side of the Moon just after sunset.

As the days progress, we will continue to see more of the lit side of the Moon as our cosmic companion distances itself from the Sun’s glare. As the Moon moves from new to first quarter, it is called a waxing crescent. At first quarter, the point in its orbit where the Moon has gone a quarter of the way around the Earth, the Sun, Earth, and Moon form a 90 degree angle, with Earth serving as the right angle of an imaginary cosmic triangle. Because of this 90 degree angle, the Moon appears half lit to us on Earth because we see exactly half of its lit side. At first quarter, the Moon also rises exactly half way between sunrise and sunset.

As the moon continues in its orbit from First Quarter, it is now farther from the Sun than the Earth. After the angle to the Moon relative to the Earth is over 90 degrees, we see more than half of the lit side of the Moon and the Moon continues to rise later each night. At this point of being over half full, the Moon is now called a waxing gibbous.

At full Moon, the Sun, Earth, and Moon are all in a straight line relative to each other. The Moon is now appears full as we can see the entire lit side because it is directly opposite the Sun in the sky. After full Moon, the Moon continues its orbit, now traveling back toward the sun as a waning gibbous. We see less and less of the lit side of the Moon as it returns toward the Sun. At third quarter, when the Moon reaches a 270 degree angle from the Sun, we again see half of the lit side and half of the dark side. The Moon now rises exactly between sunset and sunrise. After third quarter, the Moon now moves even closer to the Sun as a waning crescent, rising later each day until it is again lost in the glare of the Sun as a new Moon.




The Sun


Diameter: 864,000 miles
Volume: 1.3 million Earths
Inclination to Ecliptic: 7.25 degrees
Length of Day: 25.38 Earth Days
Surface Temperature: 5500F
Atmospheric Temperature: Up to 1,000,000F
Composition: Plasma
Atmospheric Pressure: .06% Earth
Atmospheric Composition: hydrogen, helium
Notable Exploration: Pioneers 5-9 (1959-68), Helios 1 and 2 (1975-1985), SOHO (1995-present), SDO (2010-present)

First of all, this should go without saying, but NEVER look at the Sun without specialized eye protection, whether it be in the form of eclipse glasses or solar filters for binoculars/telescopes. For penny pinchers who do not want to use eclipse shades, a #14 or darker welder's shield will work when observing the Sun with the eye alone. When looking at the Sun with the naked eye, it will often appear as a single-colored disk save a few large, dark sunspots. When turning binoculars and even or powerful telescopes on the Sun, the spots will appear more detailed, with clear shapes becoming visible.

In telescopes, the real fun starts when moving out of visible light into very specific wavelengths, which can be isolated by the use of wavelength-specific filters, which can be used to bring out specific details.





White Light
The cheapest and most simple solar filters, white light filters simply block out all but 0.001% of the incoming sunlight. The result is a dramatically dimmed solar disc that allows the viewer to now see surface detail in the form of sunspots, which are cooler (and thus appear darker) regions of the Sun that are caused by a twisting of magnetic fields in and around the Sun. Due to different materials used in the manufacturing process, the Sun can appear yellow, white, or even bluish in color.




Hydrogen Alpha
Hydrogen alpha (Ha) filters only transmit a deep red light given off by hydrogen atoms at a wavelength of 656.3 nanometers. The end result of this type filter is red Sun with easily visible granulation that turns the blank disc seen through a white light filter into a seething cauldron at the expense of rendering sunspots invisible. Another benefit: the ability to now see flames on the solar limb.





Calcium
Calcium filters, like Ha filters, only transmit light at a very specific wavelength, this time at 393.4 nanometers. The interesting implication here is that the color one sees on the Sun mirrors the magnetic field strength. Result: the Sun will appear as a blue-violet disc but points of intense magnetic activity will appear white.

Now, while there are other types of solar filters out there, the above 3 are those that are economical enough to be bought by amateurs.

Sunday, July 13, 2014

Neptune



Order from Sun: 8
Named For: Roman god of the sea
Diameter: 30,600 miles
Volume: 57x Earth
Gravity: 1.14x Earth
Distance from Sun: 2.8 billion miles
Orbital Period: 164 years
Orbital Inclination: 1.77 degrees
Orbital Eccentricity: .008
Length of Day: 16.11 hours
Temperature: -353F
Composition: Gasses, ices
Atmospheric Composition: hydrogen, helium, methane
Moons: 14
Rings: faint, partial
Notable Exploration: Voyager 2 (1989)

The only planet ever predicted by mathematical calculations, Neptune was discovered by Johann Gallee in 1846 and is invisible to the unaided eye thanks to its shining at an apparent magnitude of around +8. Uranus takes about 84 years to orbit the Sun and thus spends over 13 years in any given constellation of the zodiac.

Thanks to its immense distance, even in telescopes, the only way to tell Neptune apart from background stars is to observe it at high powers and look for the distinctive, clean-cut planetary disc.




Uranus



Order from Sun: 7
Named For: Greek god of the sky
Diameter: 31,520 miles
Volume: 63x Earth
Gravity: 0.91 Earth
Distance from Sun: 1.7 billion miles
Orbital Period: 84 years
Orbital Inclination: 0.77 degrees
Orbital Eccentricity: .047
Length of Day: 17.23 hours
Temperature: -357F
Composition: Gasses, ices
Atmospheric Composition: hydrogen, helium, methane
Moons: 27
Rings: yes, thin
Notable Exploration: Voyager 2 (1986)

The first planet discovered by telescope, Uranus was discovered in 1781 by William Herschel and appears to the naked eye as indistinguishable from the stellar background under dark skies thanks to its shining around magnitude +6.5, which is near the naked eye limit for keen-eyed observers under dark skies. Uranus takes about 84 years to orbit the Sun and thus spends about 7 years in any given constellation of the zodiac.

Thanks to its distance, even in telescopes, the only way to tell Uranus apart from background stars is by its distinctive teal color. At high powers, one can also tell its true nature thanks to the distinct disc at its edges, which present a crisp line, rather than the diffuse light that characterizes stars.

Saturn



Order from Sun: 6
Named For: Roman god of agriculture
Diameter: 72,370 miles
Volume: 763x Earth
Gravity: 1.07x Earth
Distance from Sun: 886 million miles
Orbital Period: 29.44 years
Orbital Inclination: 2.49 degrees
Orbital Eccentricity: .053
Length of Day: 10.65 hours
Temperature: -288F
Composition: Gasses
Atmospheric Composition: hydrogen, helium
Moons: 150+
Rings: yes, prominent
Notable Exploration: Pioneer 11 (1979), Voyager 1 and 2 (1980, 81), Cassini-Huygens (2004-present)


The last planet known to the ancients and the second largest planet, Saturn appears to the naked eye as a star shining around magnitude -.5. Saturn takes about 30 years to orbit the Sun and thus spends just over two years in any given constellation of the zodiac. Like Jupiter, Saturn shines at a relatively constant brightness thanks to its immense distance from Earth.

In high-powered binoculars on a tripod, Saturn's famous rings, while not being truly resolved, do present themselves in that the planet seems to have an oval shape to it, which Galileo termed as “ears.”

Like Jupiter, even the smallest telescopes transform Saturn from a featureless disc into a wonderful world that must be seen to be believed. First of all, there are the famous rings, which appear easily at around 50x power. With larger scopes and higher powers, one can see gaps in the rings, most famously the Cassini Division, named after its discoverer, 17-18th century astronomer Giovanni Cassini. With very large scopes under steady skies, smaller divisions may also appear on a good night. Another thing to look for with Saturn are color bands, which are far more subtle than on Jupiter. With Saturn's rings, there is an interesting phenomenon that takes years to present itself. Because of the angles of Earth and Saturn relative to each other, Saturn's rings appear to 'open' and 'close,' with, once every # years, the rings becoming edge-on and disappearing from view altogether. This slow progression can be observed in even the smallest of telescopes. Back to the big scopes, look for Saturn's moons. While giant Titan is easy to see, it can be possible to spot some of the other, much smaller ones, too.

Jupiter



Order from Sun: 5
Named For: Roman king of the gods
Diameter: 86,880 miles
Volume: 1321x Earth
Gravity: 2.53x Earth
Distance from Sun: 483 million miles
Orbital Period: 11.86 Earth years
Orbital Inclination: 1.30 degrees
Orbital Eccentricity: .048
Length of Day: 9.92 hours
Temperature: -234F
Composition: Gasses
Atmospheric Composition: hydrogen, helium
Moons: 67+
Rings: Yes, thin
Notable Exploration: Pioneer 10, 11 (1973-4), Voyager 1 and 2 (1979), Galileo (1995-2003)


Jupiter is the largest planet in the solar system and, because of its great distance, shines at a relatively constant -2.5 magnitude. Because of its twelve year orbit, Jupiter takes spends about a year in each zodiac constellation before moving on to the next. To the naked eye, Jupiter appears only as a bright star.

 With optical aid, the game changes dramatically. In binoculars, while the cloud bands will still be invisible, one should be able to see the 'Galilean Moons,' named after their discoverer, the Italian astronomer Galileo. These four largest moons of Jupiter are named Io, Europa, Ganymede, and Callisto and are in that same order, with Io being closest to Jupiter and Callisto farthest. A simple way to remember them is to say 'I(Io) Eat(Europa) Green(Ganymede) Caterpillars(Callisto).' Okay, it's a little juvenile, but it works. For historical implications, the discovery of Jupiter's moons proved that not all objects went around the Sun, which was preached as gospel by science and Church until that time. Also, in binoculars, Jupiter transforms from looking like a bright star into a very obvious planetary disc. To see this, just look at the edges of the planet, which appear as a crisp line and not a diffuse glow.

 In telescopes, Jupiter transforms from a featureless disc into a world alive with color. In even small telescopes, one can see distinct, reddish-pink cloud bands on the planet. The higher the power, the more detail one can resolve. In large scopes under steady skies, expect to see, with relative ease, swirling in the clouds along with the Great Red Spot. Another cool feature to be seen in a telescope at high power is the shadows of the Galilean Moons transiting the disc of the planet itself. Though not overly rare, these are fun events to observe, especially for a beginning astronomer.

Mars


Order from Sun: 4
Named For: Roman god of war
Diameter: 4212 miles
Volume: .151 Earth
Gravity: 0.38 Earth
Distance from Sun: 142 million miles
Orbital Period: 686 Earth days
Orbital Inclination: 1.85 degrees
Orbital Eccentricity: .093
Length of Day: 24.62 hours
Temperature: -125F to 25F
Composition: Rock, silicates
Atmospheric Pressure: .06% Earth
Atmospheric Composition: carbon dioxide, nitrogen, sulfuric acid
Moons: 2
Rings: none
Notable Exploration: Mariner 4 (1964), Vikings (1975-6), Pathfinder/Sojourner (1997), Twin Mars Rovers (2004-present), Mars Reconnaissance Orbiter (2006-present), Mars Science Laboratory (2012-present)


Of all the planets, Mars is often considered the most fun to visually observe. Because it is a superior planet, Mars retrogrades. But the real bonus with Mars comes about because of its highly elliptical orbit. While all planets change in brightness, most do only slightly. Mars is the notable exception. At its dimmest, Mars shines just shy of +2 magnitude. At its brightest, an obviously red Mars nearly reaches magnitude -3.

Because of the highly elliptical orbit, the distance from Mars to Earth van vary greatly. The changes in distance bring about the dramatic changes in brightness. Mars is also notable because detail of the planet, its red color, can be observed without a telescope. Of all the planets, Mars is the probably the most fun planet to observe today while it was probably the biggest anomaly for ancient astronomers to explain. By observing Mars over the course of its 2-year bit and various changes, it's no wonder that the ancients thought that it was alive.
In binoculars, Mars does not appear any different than it does to the naked eye, just a bigger, and more red.

In telescopes, though, Mars can be a real treat. By using a medium-sized (4” and up) scope at around 200x power or greater, surface detail of Mars can become apparent, especially when Mars makes a close approach to Earth. The first things to look for on Mars are its polar ice caps, not unlike those of Earth, which can actually build and recede according to the Martian seasons. If you have a really big scope and really steady skies, more can be seen on the Martian surface, namely Mariner Valley, a canyon that would stretch from New York to Los Angeles if transported to Earth. Under the best conditions, one can observe differing colors on the Martian surface, which can, from time to time, be obscured my massive sand storms, whose existence is evidenced by temporary changes to the Martian surface coloring. In years past, it was thought that such changes in surface color were caused by the blooming and dying of of vegetation, much like that of deciduous trees here on Earth


Venus




Order from Sun: 2
Named For: Roman goddess of love
Diameter: 7520 miles
Volume: .86 Earth
Gravity: 0.90 Earth
Distance from Sun: 67 million miles
Orbital Period: 224 Earth days
Orbital Inclination: 3.4 degrees
Orbital Eccentricity: .006
Length of Day: 262 Earth Days
Temperature: 865F
Composition: Rock, silicates
Atmospheric Pressure: 93x Earth
Atmospheric Composition: carbon dioxide, nitrogen, sulfuric acid
Moons: none
Rings: none
Notable Exploration: Soviet Veneras (1967-83), Magellan (1990-4)

As the third brightest object in the solar system, only out-shown by the Sun and Moon, Venus is a true sight to behold. Venus is the second planet from the Sun and, because it lies within Earth's orbit, is classified as inferior. Because of its location relative to Earth, Venus can only be seen in the morning or evening. Averaging out at about magnitude -4, Venus cannot be missed. The greatest elongation possible for Venus is about 47 degrees. The best times for viewing Venus are Spring evenings and Fall mornings, when Venus can be seen about half way up to the zenith during a good appearance. At other times of year when the ecliptic is at a flatter angle, Venus appears much closer to the horizon. Because of its brightness and movement in relation to the Sun, Venus was given special significance by many ancient cultures, especially the Maya of Central America, who considered Venus just as important as the Sun. Because of its brightness, Venus is very easy to spot. So go outside when Venus is at its best placement, you can’t miss it.

When looking at Venus through binoculars, it may be possible to see phases if the binoculars are strong enough (above 15x power) and are mounted on a tripod.

In telescopes, Venus can appear to be a mini Moon because of its very obvious phases. Because it is closer to us then Mercury, when watching the phases of Venus, look for changes in the planet's angular size as the planet will appear at its largest as a crescent and its smallest as it nears full.


Mercury



Order from Sun: 1
Named For: Roman messenger of the gods
Diameter: 3030 miles
Volume: .056 Earth
Gravity: 0.38 Earth
Distance from Sun: 36 million miles
Orbital Period: 88 Earth days
Orbital Inclination: 7 degrees
Orbital Eccentricity: .205
Length of Day: 59 Earth Days
Temperature: -280F to 800F
Composition: Rock, silicates
Atmospheric Pressure: trace
Atmospheric Composition: oxygen, sodium, hydrogen
Moons: none
Rings: none
Notable Exploration: Mariner 10 (1974-5), Messenger (2011-present)

Of all the planets, Mercury is the one most people never see. The great astronomer Nicholas Copernicus, who finally rediscovered the idea that the sun is the center of the solar system, reportedly never saw Mercury. The reason that Mercury is so difficult to spot is that it is so close to the Sun. The greatest possible elongation only takes Mercury about 28 degrees away from the sun. Because the ecliptic is rarely vertical, Mercury at greatest elongation actually appears much lower that 28 degrees in the sky most of the time. Because Mercury is an inferior planet, it is only seen in the early morning just before sunrise and early evening just after sunset. Mercury is best seen in spring evenings and on fall mornings when the ecliptic is nearly vertical, allowing Mercury to appear highest in the sky. When seen, Mercury averages out to be about a zero magnitude object near the horizon. Even though it is bright, because it is so close to the Sun, Mercury is often difficult to spot. Binoculars cure this problem. Because the sky needs to dim before the planet can be seen, any time that Mercury appears about ten degrees above the horizon is considered a good appearance. If you see Mercury, you will join an exclusive club of people who have seen the planet nearest to the Sun.

When looking an Mercury with binoculars, it still looks like a bright star without any special features. 

 In the higher power of telescopes, Mercury appears to go through a complete set of phases from new to full and back again, just like the Moon. While interesting to watch in the present, in the past, the phases of Mercury (and Venus) conformed the theory that the planets do go around the Sun, not vice versa.


Tonight's Sky for July 13: Mars Meets Spica


Tonight, the Red Planet Mars, fourth from the Sun, will come within about a degree of bright blue star Spica, alpha star of the Zodiac constellation Virgo. The best news is that this is a naked eye event that can be seen simply by going out and looking up. To see the pairing, go out and look low in the Southwestern sky for a pairing of 'stars' about an hour and a half after sunset. The blue star is Spica and the red one is Mars. As an interesting aside, this provides a great opportunity to observe color contrasts in the night sky as, despite a star being described as 'yellow,' 'blue,' or 'red,' these differences aren't often clear to a beginning observer unless contrasting objects are right next to each other.  

Saturday, July 12, 2014

Tonight's Sky for July 12: Full Moon


Tonight, the Moon will reach its full phase, which means that, as seen from Earth, it will appear fully lit. As for why it appears this way, read on! The moon is always half lit no matter where it is in its orbit. As seen from Earth, it does not always appear so thank to simple geometry. When the Sun is 90 degrees relative to Earth, it appears half lit as we can only see half of the lit side. At new phase, when the Moon is between the Sun and Earth, we can't see any of the lit side, which is why it appears to be invisible. At full phase, 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.” 

Friday, July 11, 2014

Tonight's Sky for July 11: Jupiter Sets a Half Hour After the Sun

Jupiter, 5th planet from the Sun and 4th brightest object in the sky, is now setting just a half hour after the Sun come tonight, which means that it is truly now or never to catch the king of the planets before it disappears into the Sun's glare. To see it, go out just after sunset and use binoculars to scan very low in the Western sky. The bad news: Jupiter is only about 3 degrees (3 little finger widths at arm's length) above the horizon. The good news: it's almost magnitude -2, which should help it pop out from the twilight glow. 

Thursday, July 10, 2014

Tonight's Sky for July 10: ESA's Giotto Completes Flyby of Comet Grigg-Skjellerup (1992)


On this date in 1992, the European Space Agency's Giotto space probe, which had become the first space probe to photograph a comet up close when it completed a flyby of Halley's Comet in 1986, re-awoke and completed another such mission with a lesser-known comet, Grigg-Skjellerup. On its flyby, Giotto came to within about 100 miles of the nucleus.


Wednesday, July 9, 2014

Tonight's Sky for July 9: Voyager 2 Visits Jupiter (1979)


On this date 35 years ago, the Voyager 2 space probe, which would become the only space probe in history to encounter all 4 gas giant planets, made its first planetary encounter when it flew past Jupiter, fifth planet from the Sun, coming within 350,000 miles of the cloud tops. While exciting in itself for professional and amateur astronomers, for the greater public, there was not an overwhelming wave of attention for this mission thanks to the fact that Voyager 1 had done the same in March.

Although observed for centuries by astronomers, the Voyagers helped scientists learn more about the planet in the 48 hours of either side of close approach than had been discovered since Galileo first turned his telescope on the planet more than 350 years beforehand at the start of the Renaissance.

In all, the Voyagers discovered volcanism on Io, a probable ocean on Europa, rings around the planet, more moons, and radiation belts, all while providing the first up close pictures of the Jovian system.

Tuesday, July 8, 2014

Tonight's Sky for July 8: Can You Spot Mercury Yet?


Starting now, the Mercury is going to really be rising (not in reference to the temperature) as the first planet from the Sun is now becoming visible in the predawn, Eastern sky. To try and spot the planet, go out and look low in the East-Northeast sky starting about 45 minutes before sunrise. Hints: grab binoculars and look low, as within 5 degrees of the horizon (three fingers held at arm's length). Good luck!

Monday, July 7, 2014

Tonight's Sky for July 7: Moon Meets Saturn

It's an encore of a few nights ago when the Moon made an extremely close pass by Mars, except tonight that it's the sixth planet, Saturn, that will have a close shave with the Moon, at least as seen from Earth. To see the show, simply look for the Moon and that bright 'star' right next to it. That 'star' is, in fact Saturn. For more fun, bring out the telescope!

Sunday, July 6, 2014

Tonight's Sky for July 6: Sojourner Rover Begins Exploring Mars (1997)


On this date in 1997, NASA's Pathfinder mission truly got underway as the miniature Sojourner rover drove off of its landing craft and onto t he surface of Mars, becoming the first mobile vehicle to land on another planet. Being a first of its kind mission in that it was the first rover to land on another planet and the first planetary lander to use giant airbags to cushion the landing, the world was transfixed on the mission thanks to the fact that Pathfinder/Sojourner was the first great planetary mission in the era of mass access to cable and/or satellite television as well as the Internet, which made it possible to watch live by previously unimaginable numbers of people.

As for the mission, the name was appropriate as it paved the way for the later, far more ambitious Twin Mars Exploration Rovers and (Spirit and Opportunity) of 2004 and the Mars Science Laboratory (Curiosity) of 2012. AS for this mission itself, Pathfinder/Sojourner transmitted data for 83 days (far exceeding its 30-day design life) that included roughly 2.6 billion bits of information, 16,000 images, analysis for 15 rocks, and numerous weather data measurements.

Needless to say, this was the mission that truly re-ignited the interest in planetary science that would result in a quick succession of missions culminating with the Cassini/Huygens probe, which reached Saturn in late 2004.

Unfortunately, thanks to budget cuts, NASA's ambitions of traveling to the planets and answering questions raised by the 1997-2004 series of missions will, more than likely, be restricted for the foreseeable future.  

Saturday, July 5, 2014

Tonight's Sky for July 5: First Quarter Moon Meets Mars

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. 

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 more and more of the Moon as its lit side turns more toward us as it heads for a straight line in Sun, Earth, Moon order, and thus Full phase.

As an added bonus, Mars will be very, very close to the Moon tonight so, if you want to see Mars but don't know where to look, tonight's your night!

Friday, July 4, 2014

Tonight's Sky for July 4: Earth at Aphelion


For people living in the Northern Hemisphere, it may be hard to believe but, right now, Earth is at a point in its orbit called aphelion, which is a fancy way of saying that it is as far as it will get from the Sun. Actually, aphelion occurs tomorrow (but there's already 2 key things going on tomorrow) but it's close enough to call it aphelion now.

As for how Earth can be its hottest (at least North of the Equator) when it's at its farthest from the Sun, it has nothing to do with distance, but everything to do with geometry.

The Earth's seasons are caused by the planet's 23.5 degree tilt relative to its axis. As Earth goes around the Sun, the angle of a location relative to the incoming solar rays changes. This is the reason why the Sun apparently takes a different path through the sky (high in summer and low in winter resulting in long and short days, respectively) during the year. It is this difference in angle (and resultant day length) that causes the seasons to change.

Oh yes, Earth is roughly 95 million miles from the Sun today rather than the 93 million mile average distance taught in schools.

Thursday, July 3, 2014

Tonight's Sky for July 3: Dog Days Begin


It's roughly two weeks from the start of summer for us living in the Northern Hemisphere, which means that the heat is on, but it has nothing to do with a certain Dog Star. In the time of the Ancient Egypt, the people noticed that the hottest days of the year correspond to a point in time wherein Sirius, brightest star in the sky, is very close to the Sun, so close that Sirius lent its heat to the Sun and helped make summer, particularly the 40 days between July 3 and August 10, the hottest month of the year.

Well, we now know that Sirius is 8.6 light years distant and plays no part in Earthly weather. Still, this is an interesting space history lesson and the explanation for a common phrase whose origin is unknown by many of the people who actually use it!


Wednesday, July 2, 2014

Tonight's Sky for July 2: Jupiter Sets an Hour After the Sun

The planet Jupiter, 5th from the Sun and 4th brightest object in the sky, is setting exactly an hour after the Sun. For observing purposes, early July presents the last chance to catch Jupiter in the twilight sky. As the days progress, Jupiter will sink more into the twilight every day. By the middle of the month, the king of the plants will be lost in the Sun's glare. Look for it to reappear in the predawn sky come early August. 

Tuesday, July 1, 2014

July 2014: Month at a Glance

With the arrival of July, the Summer Solstice is still a recent memory, which means that the Sun won't be going anywhere soon. Result: those short nights are going to be sticking around, making for short, but good times under the stars as the summer sky is, more than any other season, a cosmic picture book.

Cool Constellations
With the arrival of July, the summer sky is at its peak for viewing as all the major sights are now visible without having to stay up half the night. First of all, spring leftovers Hydra (or at least its head end), Corvus, Cancer, Leo, and Crater will be disappearing for the year. Virgo, highlighted by bright Spica, is also getting very low in the Southwest. Also, the Big Dipper signpost is now obsolete as the last two stops in the chain are gone with only Arcturus (alpha Bootes ) and Spica (alpha Virgo ) still remaining in the sky. Back to the Dipper, it's now pointing downward come nightfall. Onto the summer sky and the cosmic picture book. First up, Corona the crown, with a little imagination, looks like its namesake, or at least a tiara. Moving over, mythological hero Hercules looks somewhat human. Continuing into the Summer Triangle, Lyra looks vaguely like an ancient lyre. Going down, Cygnus is very swan-like
and Aquila, with a little imagination, looks like an eagle. The mini constellations Delphinus and Saggita? Yes, they look like their namesakes, too. Now, moving to the South, Libra, though dim, does look like an ancient string scale. Scorpius? Well, using your imagination, the profile can resemble a scorpion. Finally, Sagittarius, one look at it instantly reveals why it is nicknamed the Teapot. Also, there is the Milky Way, which arches high overhead on summer nights and serves as a good measure of how good (or bad) your sky is when it comes to light pollution. By the time the sky starts to brighten, a fall preview in the form of Pegasus, both Pisces, Cetus, Andromeda, Aries, Capricorn, Aquarius, and even Perseus is on tap, too.

Planetary Perceptions
On the planet front, July is shaping to be a pretty good month for planet viewing. First of all, there's Jupiter, the king of the planets, which is rapidly disappearing into the dusk twilight. At the start of the month, Jupiter sets only about an hour after the Sun. Needless to say, the time to view Jupiter is very limited. Moving to around the 5th, elusive Mercury will start to appear in the predawn sky, peaking in height around mid-month. Don't wait, though, the little planet won't be visible for long! Moving into the evening, July also presents the last chance to catch Mars under truly dark skies. Moving into the night, Saturn is still visible most of the night, the only bad news is that it is rather low thanks to the time of year and the low ecliptic plane, which means that telescopic viewing might be rather problematic thanks to having to look through a lot of atmosphere. Moving to the morning, Venus, third brightest object in the sky, is visible in the hours before sunrise all month.




Tonight's Sky for July 1: Hercules Reaches Zenith at Midnight
Want to see the constellation of Hercules but have no idea where to look? Well, early July is the perfect time to spot the mythological strongman as Hercules is directly overhead (or very near so) at the mid-Northern latitudes come early July. However, for people new to astronomy expecting an Orion-like stellar signpost, forget it as the stars that make up the constellation are anything but strong, with most being somewhere in the 3rd magnitude.