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.

No comments:

Post a Comment