Road Map of the Stars: Summer 2021

It can be nice to just get lost in the stars -- the wonderment that comes from staring up at the vast blackness of space, trying to make sense of the universe. But like here on Earth, there’s a certain appreciation that comes from having a map to tell you where you are so you can ponder it all with a sense of understanding and belonging. Come with me, as I give you a guided tour of our night-time sky. Learn what events are happening in the sky, how to find constellations, how they came to be, and what ones are visible all during the months of June, July, and August. Join me as I show you a Road Map of the Stars!

Have Questions That Didn't Get Addressed in the Show, or Are Just Curious!? Ask Those Questions Here: https://www.flyscienceguystarshows.com/contact

Supplementary Material

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Evening Sky Maps

For the most recent sky maps that include current evening constellations and astronomical events, head over to http://www.skymaps.com/downloads.html

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August 11 Night / August 12 Morning - Perseid Meteor Shower

The Perseid Meteor Shower is many people’s favorite annual meteor shower because of its high meteor-per-hour rate (up to 100) and the fact that it occurs in the summer, when nights are warm, making for a comfortable star gazing experience. The peak time (the time around which you’re likely to see the most meteors) is 04:00 EDT on the morning of August 12. 

To understand what causes a meteor shower, you first must know what a comet is. A comet is a ball of mostly ice and rock, typically the size of a small town. Though comets are exciting and rare we often don’t learn much about them in introductory science classes. We’re taught about the planets that orbit the sun -- Earth orbits the sun once every 365.25 days; Neptune, the furthest planet from the sun in our solar system, orbits the sun every 165 Earth-years. (Neptune is MUCH further from the Sun, and orbits far more slowly, so its orbit around the Sun is longer and takes more time). 

An illustration of the Oort Cloud, and the Kuiper Belt. The Kuiper Belt is similar to the asteroid belt in that it’s home to a lot of left over material from the early formation of the solar system. But instead of objects made mostly of rock and metal, like asteroids, they are mostly icy bodies.

NASA, 2009

Our solar system is home to hundreds-of-thousands of comets that have enormous orbits -- orbits even larger than Neptune’s! Most comets lie in a sort of “cloud”, or “shell” surrounding the solar system -- orbiting the sun, but never coming close to it and never passing through our solar system. But some comets -- like Halley’s comet, or Swift-Tuttle (the comet responsible for the Perseids) -- have orbits that DO pass through our solar system, often taking hundreds of years for these comets to complete one orbit around the sun. 

As these comets approach the inner solar system they begin to sublimate (turning from ice directly into gas) leaving a trail of ice and rock bits in their orbital path. If the Earth’s orbit intersects with the orbit of a comet, those bits of rock and ice enter Earth’s atmosphere. Now, you may be wondering, if Earth’s orbit intersects with the orbits of various comets, doesn’t that mean the Earth could collide with those comets? Well because comets have such big orbits, most of the time when Earth passes through a comet’s orbit, that comet is far away at a different part of its orbit. (If you’ve ever been to a track meet at an American football/track stadium, imagine crossing the track to get to the infield at one end zone while the runners are all the way at the other end zone.) But it can happen-- the Earth could (and has) collided with comets. And while that sounds theoretical, it could become a very real and imminent concern sooner than you might think, but to hear more about that, you’ll have to watch our Halloween show! (Or you could research it independently in the meantime.)

So “shooting stars” are these bits of rock burning up in our atmosphere due to friction with the gas and particles in our atmosphere. When they enter Earth’s atmosphere and are plummeting towards Earth’s surface, they’re called meteors. Most meteors are burned up completely before reaching Earth’s surface. But those that do reach the surface are called meteorites. So before reaching Earth’s surface = meteor; after reaching Earth’s surface = meteorite.

The comet whose orbit we pass through to cause the Perseid Meteor Shower is called Swift-Tuttle (not swift turtle, like Becca likes to say). It was officially discovered in 1862 by -- you guessed it -- Swift and Tuttle (Lewis A. Swift and Horace P. Tuttle, to be exact). It has an orbital period of 133 years so it’ll pass through our solar system and we’ll be able to see it from Earth every 133 years. The last time it was visible from Earth was 1992 and the next time it will be visible from Earth is 2126. Its diameter is 16 miles across or about 1.3 times the size of Pittsburgh! (For reference, that’s more than twice the size of the asteroid that took out the dinosaurs!)

August 22 - Full Moon, Blue Moon

On August 22nd there will be a Blue Moon, which is actually more common than you might think. To read more about what a blue moon is, what causes it, and how it got that name, check out this article! 

Planets to Look For

Mercury

The best times to see Mercury this summer will be July 6th through 12th around 04:15 EDT (so super duper early in the morning). Mercury isn’t the “showiest” planet in our solar system. It doesn’t boast the tallest mountain or deepest canyon; it’s not the largest planet; it’s unlikely to host any life. The reason I like to point out Mercury is because it is what I call, our solar system’s shyest planet. Looking for Mercury is like seeking a rare bird while birdwatching. Planets like Jupiter and Saturn-- when they’re visible in our sky, they steal the show, often sailing all the way across our nighttime sky. That’s because they’re superior (in the literal-- not judgemental-- sense of the word) planets, meaning they’re further from the sun than the Earth. By contrast Mercury is an inferior planet-- it’s closer to the sun than Earth is. (Actually, of all 8? Planets in our solar system, Mercury is closest to the sun.) This translates to much less opportunity to see Mercury. 

Mercury’s Morning Debut

For more information on why inferior planets are “shyer” than superior planets, check out this article.

When superior planets are most visible in our nighttime sky, it’s because in space, they are on the opposite side of the Earth from our Sun, so the superior planet is fully illuminated by the sun all night long. For inferior planets, they’re never on the opposite side of Earth from the sun. They’re usually either behind the sun, in which case they’re block from our view by the sun, or they’re in front of the sun, in which case they’re not visible because they’re “drowned out” by the sun’s light. So the window to see an inferior planet is smaller -- only when they’re essentially to the “left or right” of the sun (rather than in front of or behind it) from our perspective on Earth.

When Mercury is in this orientation, we can see it, but not all night long. We can only see it in either the morning (as it starts to rise above the horizon just before sunrise, until it gets drowned out by daylight) or in the evening (as it becomes visible just above the horizon just after sunset, until it descends below the horizon not long after the sun). Because of this, the best time to see Mercury is simply when you have the most time to see it before it either sets or is drowned out by the sun. This summer, the best times to see Mercury are the early mornings of July 6th, through July12th. Those days, it’ll rise above the horizon around 4:15AM (EDT) and will be visible until it gets too light to see stars and planets, around 05:30AM (EDT).

Saturn

Galileo-- what a guy. Am I right? I mean, that guy. Anyways, Saturn is a superior planet. The best time to see it this summer is the night of August 1st / morning of August 2nd, when it’ll sail high across our nighttime sky, rising in the east around 20:16 (8:16PM) EDT and will be visible all night long until the sun rises and drowns out the stars/planets, around 06:00AM EDT. It’ll reach its highest point above our horizon at 01:14 AM EDT. 

Saturn is a great telescope target because of its rings. You’ll easily detect the rings of Saturn with even a low powered telescope, or a good pair of binoculars! When Galileo saw Saturn he called it a planet with ears because of how the rings look through his low powered telescope. 

The rings around Saturn, extend out about 175,000 miles away from Saturn itself, but are just a few yards thick. If you were to shrink Saturn down to the size of a football field -- the rings would be thinner than a piece of paper. Being so thin, when Galileo was studying Saturn, he noticed the “moons” disappear, then reappear a few years later. That’s because during those years where they disappeared, he was viewing Saturn’s rings edge on, causing them to be very difficult to detect!

Another claim to fame of Saturn is -- it’s also the least dense planet in our solar system. Density is mass (the stuff) per volume (the space the stuff takes up). Saturn is almost the same size as Jupiter, but it's far less massive -- this makes it much “lighter”. In fact, if you had a bathtub big enough and you filled it with water and plopped Saturn inside of it -- Saturn would float on the water! Making it like solar systems' very own rubber duck!

Jupiter

The Galilean Moons

Check out this article to learn more about the four Galilean moons, including one that scientists are exploring as a candidate for life!

On August 19th, Jupiter will be in opposition, so that’s a great time to point your telescope at it! With even a good pair of binoculars, you’d be able to see the same moons Galileo did!

When Galileo looked at Jupiter through a telescope (yeah-- that guy looked at lots of things through a telescope) he saw little dots around Jupiter. He was like, “Haha! That’s neat -- how close these stars appear to be to Jupiter through my telescope!” 

Then the next night he looked at them and they were in different places and he's like, “Hol’ up! That’s pretty wild.” He kept observing them and realized they were moons going around Jupiter! This supported Copernicus’s idea that everything doesn't revolve around the earth because the Galilean moons were clearly revolving around Jupiter. 

With a modest powered telescope, you may even be able to see bands of clouds on Jupiter, which are rising and sinking cloud systems traveling in different directions around Jupiter (the brown bands being sinking cloud systems and the white bands being rising cloud systems).  

Jupiter viewed from a low-powered telescope compared to how it looks with sophisticated equipment.

Another notable feature on Jupiter is the Great Red Spot. It's a giant, anti-cyclone storm much like hurricanes here on Earth, but two-to-three times more powerful than the worst hurricanes we'd have on earth. It’s about 1.5 times the size of the Earth and has been raging for at least 150 years, when it was officially and definitively discovered by Samuel Schwab in 1831. But it’s possible that the storm has been raging for longer-- maybe even three-hundred-years-- because one of the first mentions of it (historians/scientists think) was in Galileo's journals when he was studying Jupiter three-hundred-years ago. However it would have been very hard for him to see the Great Red Spot in detail, as his telescope -- that I could find -- would be comparable to low powered refractor telescopes today. Since its official discovery in 1831, the Great Red Spot has been shrinking. Its current size is about one-and-a-half “Earths” in diameter, but when it was discovered it was roughly three-times larger than Earth! This storm is fueled by those bands of rising and sinking cloud systems.

Jupiter is the largest planet in our solar system and our most massive planet as well.  Now, that may seem redundant-- saying Jupiter is both large and massive--but mass and volume are not the same thing (though we often say something is massive in everyday conversation whenever we're talking about it being large in volume). Mass is what makes something up. It's what gives something weight. It's what gives me weight; it's what gives you weight. In fact, Jupiter is so massive that it has more than twice the amount of mass of all of our planets, their moons, and the asteroids in our solar system combined!

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