Saturday, July 25, 2015

Tonight's Sky for July 25: Moon Meets Saturn

New to astronomy? Want to see Saturn but don't know where to look? Well, it's your lucky night as the Moon will be right next to Saturn tonight.

The moon is, of course, impossible to miss. As for Saturn, it's that bright 'star' right next to Luna. The way to tell that Saturn is a planet? Unlike stars, planets don't twinkle thanks to the fact that they shine from reflected light. 

Thursday, July 23, 2015

Tonight's Sky for July 23: 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.

Wednesday, July 22, 2015

Tonight's Sky for July 22: Venus, Jupiter, and Regulus Triangle

Tonight will feature a last notable sight for three prominent heavenly bodies: the two brightest planets, Venus and Jupiter, as well as the star Regulus, alpha Leo. As for what there is to see, go out and look low in the Western sky just after sunset, preferably with optical aid, as the planets and star will form a just about perfect triangle low in the Western sky.  

Monday, July 20, 2015

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

It was 46 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.

Sunday, July 19, 2015

Tonight's Sky for July 19: Dropping Venus

About a week ago, when I pointed out that Venus and Jupiter were now separated by 5 degrees, I hinted that there was one final act to the planetary dance and tonight, this change is now obvious in that Venus is now clearly below Jupiter. Coming up to the conjunction, Venus was, far and away, the higher of the planets. Following conjunction, the two seemed almost welded at the same altitude while pulling away from each other. Now, though, the heights have clearly flipped as Venus now leads Jupiter into the Sun's glare for an upcoming period of invisibility. 

Saturday, July 18, 2015

Tonight's Sky for July 18: Moon Meets Jupiter and Venus

New to astronomy? Want to see Venus and
 Jupiter but don't know where to look? Well, it's your lucky night as the waning crescent Moon will be right next to the planets this evening. 

To see the show, just go out after sunset and look low in the West. The Moon is, of course, impossible to miss. As for the planets, they're bright 'stars' flanking Luna, with Venus being the brighter and Jupiter the dimmer. The way to tell that these are planets? Unlike stars, planet's don't twinkle thanks to the fact that they shine from reflected light. 

Friday, July 17, 2015

Tonight's Sky for July 17: “Young” Moon

How thin of a Moon have you seen? How about one that's just barely over 2 days old and only 5% 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.

Wednesday, July 15, 2015

Tonight's Sky for July 16: Comet Shoemaker-Levy 9 Hits Jupiter (1994)

On this date 21 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 cosmic 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.  

Tonight's Sky for July 15: 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.

Tuesday, July 14, 2015

Tonight's Sky for July 14: New Horizons Flys by Pluto

Today, NASA's New Horizons space probe will complete its much anticipated, 9-years in the making flyby of Pluto, which was still the solar system's 9th planet at the probe's launch in 2006. Stay tuned for the first close pass pictures, which are expected to make it to Earth sometime tomorrow. 

Monday, July 13, 2015

Tonight's Sky for July 13: Venus and Jupiter Separated by 5 Degrees

They were only about 1/5th degree apart on June 30 and now, two weeks later, Venus and Jupiter are separated by about 5 angular degrees. As the month progresses, the gap won't widen all that much but, when remembering how the planets were placed relative to each other coming up on the conjunction versus now, there's another change in the winds, so keep your eyes to the sky as the show's not over.

Sunday, July 12, 2015

Tonight's Sky for July 12: Moon Meets the Hyades

The calendar may have just flipped to summer a few weeks ago but the predawn sky is saying winter as the Moon will be visible amongst the Hyades in the predawn sky. To see the show, go out just before sunrise and find the Moon. Moon found, look for the 'V' of stars that surrounds it. These stars are the Hyades Cluster, located in Taurus the Bull. 

Saturday, July 11, 2015

Tonight's Sky for July 11: Solar Storm, Round 2?

Yesterday, NOAA predicted a 40% chance of a geomagnetic storm for observers at high latitudes. Well, the space weather wizards were right on track (and perhaps a little conservative with hindsight) as aurora were reported as far South as approaching the 40 degrees North latitude mark. Now, NOAA is predicting that the storm could pick up strength again tonight as the solar wind that set it into motion yesterday continues to build strength. Needless to say, keep an eye on the sky if it's clear tonight and you live in the Northern United States.

Friday, July 10, 2015

Tonight's Sky for July 10: Aurora Alert

NOAA is forecasting a 40% chance of geomagnetic storms (and hence aurora, also known as the Northern Lights) in the Arctic Circle. However, the Lights have been known to creep farther South in major storms so, if its clear, keep an eye on the sky tonight.

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 7, 2015

Tonight's Sky for July 7: Saturn Sets 5 Hours, Jupiter and Venus 2 Hours After the Sun

It's the month of the plunging planets as is reflected by the 3 for 1 deal being described for today. For starters, Venus and Jupiter are both setting roughly 2 hours after the Sun, which means that anyone wanting to get a look at them had better hurry up as the 1-2 hour after sunset window is often the last opportunity to just go out, look up, and say “there it is!” before optical aid starts being a necessity. Interestingly enough, Saturn also sets just about on an even hour after the Sun, 5 hours as of tonight, meaning that there are still plenty of opportunities to catch it under a dark sky. 

Monday, July 6, 2015

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

On this date in 1997, NASA's Pathfinder mission truly got underway (it arrived on July 4) as the miniature Sojourner rover drove off of its landing craft and onto the 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 surface mission in the era of mass access to cable/satellite TV and 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, including: 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 Mars, which had largely waned since the Vikings came up empty in their search for life in the 1970s.

Sunday, July 5, 2015

Tonight's Sky for July 5: 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. 

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.

Saturday, July 4, 2015

Tonight's Sky for July 4: Cosmic Fireworks

It's July 4, which means that, for us in America, tonight is really our only holiday where fireworks are a given. Keeping with the exploding theme, why not look at some cosmic fireworks tonight, or at least the smoky remnants of them?

For the record, the cosmic fireworks are supernovae, high mass stars that explode at the end of their lives as their fuel runs out and all nuclear fusion ceases. As for the smoky remnants, they are supernova nebulae, often irregular, inkblot-like clouds of glowing gasses left over from these stellar deaths. Additionally, as not all the fireworks at July 4 displays are big boomers, the same rings true in the cosmos as low mass stars like our Sun will slowly puff off their outer atmospheres as clouds of glowing interstellar gasses at the end of their lives. The remnants here are called planetary nebulae for the fact that they are often small and have high surface brightness even though they have nothing to do with planets.

So, here we go, a list of summer nebulae with finder charts. . .

Disclaimer: there are far more nebulae out there, but these are the brightest, most famous, and easiest to find. Needless to say, the other seasons are loaded with nebulae, too. . .

Lagoon (M8)

Trifid (M20)

Swan/Omega (M17)

Eagle (M16)

Ring (M57)

Dumbbell (M27)

Friday, July 3, 2015

Tonight's Sky for July 3: The 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!

Thursday, July 2, 2015

Tonight's Sky for July 2: Venus and Jupiter Still Close

They may no longer be only 1/5th of a degree apart, but Venus and Jupiter are still extremely close on the dusk sky, so why not go out for a look at them as all that you need to do is go out after sunset and look just about due West.

Wednesday, July 1, 2015

The July Sky and Tonight's Sky for July 1

With the arrival of July, the Summer Solstice is still a recent memory, which means that the Sun won't be going anywhere anytime soon. Result: those short nights are going to be sticking around, making for abbreviated, 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
Thought last month was on the dull side for planet watching? Well, July is really going to be a drag as there is not much at all to see when it comes to our planetary neighbors. For starters, Mercury and Mars are really non-issues with the former making a quick, anything but impressive appearance in the morning sky at the start of the month and the latter being lost in the Sun's glare just about all month long though it will be possible to spot Mars at month's end in the predawn sky with optical aid and a sky chart. More bad news: Jupiter is now a dusk-only object, too. Next up: Venus, which has blazed away like a celestial beacon in the early evening sky for several months but by month's end, it too will disappear into the Sun's glare. That leaves Saturn, which is about as high as it will get in the South come the arrival of truly dark skies. Good news: it is at its best positioning of the night as soon as the sky gets dark. Bad news: this is summer and the ecliptic plane is very low, which means that Saturn, the only planet visible all month, isn't exactly that well placed, either. Looking for something interesting to watch over the course of the month? Well, there is something, namely the increasing angular separation of Venus and Jupiter, which got to within 1/5th degree of each other on June 30. Additionally, the planets will change position, with Venus dropping beneath Jupiter post-conjunction.

The Milky Way and its Treasures
Summer is the season to view the Milky Way, the plane of our home galaxy, which takes the form of a ghostly river of light made up of stars too faint to resolve with the human eye running from South to North in areas that still have dark skies. From the country, far away from any cities, the Milky Way is stunning and it is possible to even discern details in the form of shape and areas of exceptional brightness from horizon to horizon. In suburbia/small cities, the Milky Way can be seen near zenith if the light pollution is not overly obscene. Additionally, the weather can play a factor, too, as humidity magnifies light pollution. Bottom line: don't go out to your suburban backyard (going from front to back to escape street lights is a huge help) on a sticky, humid night, but rather wait for a cool front to bring cool, dry air to your area and then go out, let your eyes adjust to the dark, then look up. Believe me, humid and dry nights can result in two dramatically different skies.

For people with medium to large telescopes, there's more: globular clusters, which are tight groupings of stars numbering in the hundreds of thousands, the majority of which cluster around the plane of the Milky Way near the galactic center, which is located in Sagittarius. Yes, while there are other globulars that can be seen in other seasons, the summer sky contains the lion's share and brightest of them, so make it a point to view these cosmic firefly swarms while they're visible.

Tonight's Sky for July 1: Full 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.