March & April 2023 – Astronomy & Astrophysics

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March 2023- Astronomy & Astrophysics Part 1

Week 23: Planets, Moons and Binoculars

Week 24: Comets, Asteroids, and Meteorites

Asteroids are smaller than a planet, but they are larger than the pebble-size objects we call meteoroids. A meteor is what happens when a meteoroid – a small piece of an asteroid or comet – burns up upon entering Earth’s atmosphere, creating a streak of light in the sky. We have discovered over 1 million asteroids and 3,700 comets. Previously, it was thought that comets were icy and sprouts tails when they got close to the sun, and asteroids were dead rocks without any volatiles (like ices that can turn from solid to gas when heated up), but then we found comets acting like asteroids and asteroids with tails! Now we know that there is a continuous spectrum that contain both comets and asteroids. Let's take a look together!

Week 25: Galaxies, Telescopes & Big Observatories

If you ask any astronomer over the age of 50 what the single biggest astronomical discovery was in their lifetime, they all seem to say the same thing: GALAXIES. In our week together we're going to learn all about galaxies and explore how we know what we know, and what questions we're asking and how we're making new discoveries!

Week 26: Solar Astronomy, Stellar Astrophysics and Solar Scopes

Bonus Field Trip: Stargazing the Moon with Brian!

This was a fun stargazing event we did with our students, and here's the recording in case you missed it. If you look further down this page, you'll find Dr. Coomb's 7-day Tour of the Moon, which is good to do after watching this lesson below. 

April 2023 Astronomy & Astrophysics Part 2

Week 27: Star Clusters, Double Stars, & Nebulae

The stars you see at night are actually all from our own Milky Way galaxy! Explore different types of stars, how they clump together in different of groups of star clusters, and learn how to star hop using a simple pair of binoculars.

Week 28: Deep Space Objects

When we look up, we see stars. Most of you see with your naked eyes are all inside our galaxy, but outside our solar system. Once you peek through a telescope, you’ll be amazed at how many different kinds of objects are not part of our solar system, such as nebulae, star clusters, and galaxies. We’re going to explore these deep sky objects and learn how to navigate the night sky.

Week 29: Black Holes & Supernovae

Is time travel into the future possible? Are there really such bizarre objects that warp space and freeze time? What about wormholes and tunneling – are those possible? You bet! We’re going to take a sneak peek at the physics behind this and much more!  We're going to discover what happens to stars that wander too close to a black hole, what happens when black holes smack into each other, and figure out the different ways to detect black holes since they are invisible.

Field Trip: UCLA Galactic Center Research Group

This presentation is from one of the astronomers that contributed to the team's award of the Nobel Prize in 2020 for their work on the supermassive black hole at the center of our galaxy. Please note: This presentation may not be suitable for all families, as the astronomer will discuss stellar evolution. Please decide if this presentation is appropriate for your family before viewing.

BONUS CONTENT for Astronomy & Astrophysics

What's up in the sky tonight? How to use the SkyGazer's Almanac

The Skygazer's Almanac is the absolute BEST wall chart for quickly knowing (at a single glance) what's up in the sky tonight, including planets, meteor showers, and lunar phases.  There's a TON of information on it (and complete instructions on how to read it on the back), but it's a little difficult to understand written instructions, so I've created a video you can refer to here. You can purchase your own copy directly from Sky & Telescope, and notice which hemisphere and latitude you're at before you order!

Bonus! Stargazing Sessions and Messier Marathon!

Dr. Lee Coombs' 7 Day Tour of the Moon!

How to Use Binoculars for Stargazing

How can you tell if your pair of binoculars are good for stargazing? And what's the difference between a $50 pair and a $500 pair that are the same size and magnification?  Does it really matter?

The more expensive pair will have clearer, crisper images. Around the edge of the view will continue to be clear without any distortion, but this isn't as important for stargazing as it is for day use. A little out of focus is okay. If the edge is way out of focus, try a different brand.

Stargazing binoculars generally are between a magnification of 7x to 10x. The objective lenses (the larger lenses) are usually between 35mm to 60mm, although I don't recommend anything larger than 50mm because it gets hard to hold steady the longer you look through them. I wouldn't go any smaller than 7x35 for stargazing. 7x50 or 10x50 are a perfect size for astronomy.

For older stargazers, exit pupil size matters. This is the size of the bright disk of light you see in the eyepiece when you hold up the binoculars. A 7x50 pair of binoculars will have an exit pupil of 50/7 = 7mm.  If this number is larger than the size of your pupil (when adapted to the dark), that will be light that doesn't enter your eye. If that's you, then look for binoculars with an exit pupil of 5-6mm.  You can easily (and carefully!) have someone  measure the size of your pupils using a ruler.

In general, you don't use eyeglasses when you look through the binoculars. The binoculars can adapt to your eyes, unless you have an astigmatism. Try looking both with glasses on and off to see if you need to keep them on when stargazing. If you find you do need to wear eyeglasses  when using binoculars, then look for a pair that has at least 15mm of eye relief (most binoculars will have this already).

When you pick up a pair of binoculars, look at the light reflected in the objective lenses. They should be mostly dark, if they are white or red, try a different brand. Now look through the lens at the prisms inside. If they have a good anti-reflection coating, you'll see a rainbow colored surface. If it's white, try a different brand. 

I've outlined the main points above, and then I thought it might be easier to show you a video how to test for everything you need to know to be sure your pair is good for the night sky (and chances are, they are!)

My good friend, retired university chemistry professor, Dr. Tom Frey, also has a passion for astronomy... specifically binoculars. Here are two videos from  Dr. Frey about how he made his own personal "binocular chair" - I hope you enjoy it!

How to Set up a Telescope

Whether you have a telescope or are just interested in learning how telescopes work, this instructional video will talk you through the basic information for setting up a telescope. 

Best Accessories for your Telescope

Once you have a telescope, the next thing you'll need are all the cool gadgets to make it perform better! Here is a short list of the most-used accessories for telescopes that I think you will find useful to learn about.

First, you'll need a finder scope. These are small, low-powered telescopes that are on the side of the main telescope to help you point your telescope in the right direction. You can use a laser finder or an optical finder. Laser finders don't actually magnify anything, they just put a small dot on the night sky.

Eyepieces! My personal joke is that I spend more on eyepieces than I do on a telescope. You'll need at least one (your telescope probably came with one), and I recommend a short, medium and long focal length so you can change the range of your magnification depending on what you are looking at. 

If you have a refractor or a compound telescope, you'll need a star diagonal to make it easy to look through the eyepiece. (If you have a large reflector telescope, then you'll need a ladder. )  

Filters aren't something you need at first, but as you get better at finding objects in the night sky, you'll probably want to start looking at different types of filters. There are dozens to choose from, depending on what you want to look at as well as your "seeing" conditions. 

Red flashlights are essential, as are red "transparencies" to  put on computer screens and tablet/cell phone screens. You can use "gels" or "acetate" filters used for theater lighting or art supply stores.

Star maps are essential, and can be on a laptop or cell phone to help guide you through the night sky. You can also get a printed version, a star wheel, or use the free monthly publications from skymaps.com

The Most Important Numbers on your Telescope

What size is it? How "fast" is it? What is the magnification? What is the "light collecting" ability? What is the focal length? We'll take an in-depth look at all this and more. 

The first number to know about your telescope is how big the main mirror or main lens is. Think of your telescope as a light-bucket. The bigger the "aperture", the brighter the image will be when you look at it through the eyepiece. A good telescope will have an aperture between 4 to 12 inches (100mm to 300 mm).  A telescope with a 200mm lens will have four times the light collecting ability than a 100mm lens. 

The next number to consider is the focal length of your telescope. When light hits the main mirror (or lens if it's a refractor), the mirror/lens focuses the light at a certain distance away, called the focal length. A 12" telescope will have a focal length of about five feet, which makes these telescopes hard to handle when they are that long. Some telescopes bounce the light back and forth a few times inside of the telescope, which makes these telescopes shorter and easier to use (but heavier and more expensive).

A long focal ratio means higher magnification and narrower field of view when you look through the eyepiece. The  Focal Ratio is the focal length divided by the size of the main mirror (or lens).  A typical focal ratio of f/10 is great for looking at double stars, planets and moons. If you want to look at galaxies, star clusters and deep sky objects, you don't need as much magnification and you'd actually prefer a wider field of view like an f/7 or f/5. You'll also notice a difference in brightness when you compare an f/10 and f/5 telescope. The galaxy in a f/5 ("short" telescope) will appear four times as bright as the f/10 ("long"), but only be half as large.  (If you're just looking at individual stars, it's only aperture that really matters here.) A f/6 or f/7 is a medium telescope, good for all purpose viewing.

In general, the maximum useful magnification of a telescope is around 50 times the mirror diameter (in inches). If you have a 6" telescope, then anything above 300x will appear fuzzy or dim.  

Most folks without any telescope experience will ask: "What's the magnification of that telescope?" An experienced astronomer will ask: "What's the diameter of your mirror?"

You can change the magnification of your telescope by simply swapping out eyepieces. To figure out the magnification of your telescope, divide the telescope focal length by the eyepiece focal length. 

When you look at a star cluster, they will at first look like a faint fuzzy. The resolution of a telescope will allow you to make out the tiny details, like the spacing ("separation")  between stars. Resolution is really important when you look at the surface of the moon or a planet, or if you're looking at double stars or star clusters. A 200mm telescope can resolve details twice as well as a similar 100mm telescope. 

How to use Stellarium Stargazing Program

Stellarium is the planetarium software I used in class to demonstrate how to find different objects and constellations. It's free (download it here) and set it up on your computer by setting it up for your specific location. Use the video below to help you get started with the program.

How to tell TIME by the Stars!

From the northern hemisphere, the big dipper is above the horizon for most of the year. In the spring time (especially in March), it's fun and easy to learn how to tell time by the stars!

First, go outside after sunset and find the Big Dipper. Use a compass if you need to to find NORTH, then tilt your head back and look up from the horizon for seven bright stars. Draw a line through two bowl stars (furthest from the handle) and extend that line so it hits the north "pole" star Polaris. The "sky clock" is a 24-hour clock, not a 12-our clock like the one in your house. Polaris is the center of the clock, and the hour hand is the line you drew from the Big Dipper to Polaris.

Now use this simple formula: The current TIME = the clock reading MINUS twice the number of months after March 6. (You can use March 1 to make it easier to figure out.) Since we're in March, right now, that "number of months past March" is ZERO. (See why it's easy in March?) So go look up at the sky clock and read what time it is!

Notice how we read the sky clock COUNTERCLOCKWISE. This is opposite of the clock in your kitchen.

Let's take another example. Suppose it's Dec. 1st. Dec 1 is close to Dec 6, so let's figure about 9 months (to be exact, it would be 8.75 months, but let's make it easy to calculate this time through). The night sky looks like the second image (without the clock superimposed over it). Can you tell me what time it is?

ANSWER:   The clock reads 2PM. The correction is 2 x 9 = 18. So the time I read on the clock is about 2PM (you could say 1:30PM, but I am trying to make it easier here). Now turn that "PM" into "AM" by subtracting 12 hours. Now subtract 6 more hours (18-12=6) from 2AM to get 8PM! The more you practice this, the easier it will be!

Visualizing Spacetime and Gravity

This high school teacher did a fantastic demonstration on how large objects like stars and planets affect the fabric of spacetime. 

Astrophysicist explains gravity from simple to hard

Right now, you might feel heavy in your chair. But what does the chair have to do with it? Imagine standing in a black elevator, and the cable is cut and you and the elevator are both in freefall. You will float in the elevator as you experience weightless. What you are really doing when you feel heavy in your chair is is falling weightlessly in the gravitational field.  Think of gravity as weightlessness and falling (like zero-gravity experiences in airplanes as it nose-dives).

If you were floating in empty space, and you threw a ball, it would travel in a straight line. But if you threw the ball while standing on the Earth, it would trace a curve, and the faster you threw  it, the longer the arc through the air. When things fall freely around something like the Earth, they traced curved paths, as if space-time itself is curved. 

The fabric of space can curve and twist around objects like stars and planets. Spacetime itself is curved. That's how Einstein gets to thinking that spacetime itself is curved.  There is this field that permeates all of space, and there are curves that things fall along.  

If we look at how things fall, and you see how they follow curves, you can realize that the space and time don't just contract or dilate but they can bend and curve and really warp. If the sun were to disappear tomorrow, the curves that the sun imprinted on space and time would actually begin to ripple (gravitational waves), and flatten out because the sun was no longer there, and that would take the light-travel time for that information to get to us to tell us the sun was no longer there, and we would stop orbiting and just travel along in a straight line.