July 2017 - Page 2 of 2 - The Spacewriter's Ramblings

What Will YOU Do For the Eclipse?

You may have heard about the upcoming total solar eclipse.

Let me put that another way: there’s no way you haven’t heard about the upcoming solar eclipse set to cross the U.S. in just over a month’s time. Every astronomy publication worth its solar filters is blatting around about it. I can’t look on Facebook or Twitter without seeing a reference to Yet Another Article on How to Safely View the Eclipse and “Top Ten Places to View an Eclipse” and so on. One astro-related magazine that we get is going totally bonkers in coverage for the event. I guess will help sell issues but the drama is overdone.

Eclipse Hype Raises Prices

In any case, the word is out: there’s an eclipse. So, what do you do?

Make no mistake about it: a total solar eclipse is an amazing thing to view. I’ve been to six (this will be my 7th), seen five and marveled at how very cool they looked. And, if you CAN get to a place to watch it, please do. You won’t regret it.

What you MAY regret is waiting too long to get hotel reservations or finding a place to watch it from safely. Like every good capitalist enterprise, hotels are charging out the wazoo for a room. Many are requiring multiple-night stays. I’ve read stories of places in Oregon and elsewhere charging outrageous amounts to people who simply want to camp. Sure, there are costs involved in hosting people to camp, but are they suddenly higher just for a couple of nights? Or, is there a bit of gouging going on?

I was talking to a relative last weekend who lives in Wyoming. It’s a state of about a half million residents that will be inundated by perhaps a million people for the eclipse. Her friend runs a state park and realized that their sleepy town will need to clean up after people who will likely leave their trash lying around after the event. So, they’re charging a small fee for camping to pay for the cleanup. Fair enough — nobody should work to clean up after others for free. But, the random campgrounds that are suddenly jacking rates up to hotel-room prices (and higher) are taking advantage. Too bad for them; the reputation is something you can only squander once.

In any case, don’t let this scare you away. Hit the road and treat yourself to the event. Just be aware there will be stresses on the system. Be prepared for higher prices for goods and services due to increased demand for them. And, be ready for traffic congestion. Lots of people will be heading to see it, too.

Also, make sure you’re going to the zone of totality, where you will experience the deepest eclipse. If you want to know where the zone of totality is, check out the maps at NASA’s very complete eclipse website. Plan ahead. Bring your own food, water, even a roll of TP if you have to. Just don’t miss the event and the chance to watch a very cool natural phenomenon!

Old Tales about Eclipses

I’ve also been seeing a lot of strange suggestions by way of “advice” for watching an eclipse (like “cheaping out” by using welder’s glass, using CDs, etc. to shield your eyes). Also, there’s some hype about photographing the event. And, there are stories everywhere about getting to the zone of totality. Here’s what you need to know:

1) you only need your eyes to watch an eclipse. Use them in a safe place — like a parking lot or a park, not the middle of a highway;

2) observers need to wear eclipse glasses (libraries are giving them away) that will protect your eyes during the partial phases (that is, when the Sun isn’t completely covered by the Moon). Once totality starts, you take off the glasses and look at the Sun safely for about 2.5 minutes. Then, you put them back on, because the Moon will move on, and the Sun will suddenly be uncovered. Not acceptable for viewing: welder’s glass, sunglasses, CDs, tin foil, or other substitutes. They’re your eyes, and we think you probably want to do the best you can to protect them. So, get eclipse viewers. Accept no substitutes. And don’t directly at the Sun without protection, until totality. See below.
3) If you want to take pictures, you can probably safely do so with your smartphone, although it won’t look too great. If you’re not an eclipse photo aficionado, your best bet is just to watch and enjoy. Don’t fiddle with a camera if you don’t have to.
4) Okay, so if you want to do photography and know what you’re doing, check out my friend Jerry Lodriguss’s site for all kinds of good tips and hints.
5) Don’t buy into any hype about how the eclipse will affect your chakras, karma, cosmic energies, and other such nonsense. It’s all designed to mystify something that’s pretty simple to understand.

What’s a Total Solar Eclipse?

Watch this movie. It gives you a good idea of what the mechanics of a solar eclipse. So, a total solar eclipse is pretty simple to understand from a mechanical viewpoint. It happens when the Moon moves in its orbit between us and the Sun. It just so happens that the Moon will be at a distance of about 227,000 miles from Earth. At that distance, it’s just big enough to hide the disk of the Sun from us for about 2.5 minutes during totality. The Moon casts a shadow onto Earth’s surface. If you’re in the deepest part of the shadow (the zone of totality), you’ll see the Sun become completely eclipsed as the shadow sweeps past.

The actual eclipse takes about three hours as the Moon moves in its orbit around Earth. The moment the Moon first “touches” the Sun’s disk is called “First Contact”. That’s the beginning of the eclipse. From there, the Moon slowly slides between the Sun and Earth. While you can’t look directly at the Sun at that time, you can watch over the next hour or so, as more and more of the Sun is covered. Also, look around you and watch as the ambient light at your location changes. It’ll slowly take on a twilight aspect. Shadows become sharper.

Pro tip: if you have trees nearby, look at shadows of leaves as the Sun shines through. They’ll start to take on the shape of the Sun. This is the same concept as shining the Sun through a telescope and projecting the light through the eyepiece onto a piece of paper. What you’ll see projected onto the paper is a slowly disappearing slice of the Sun. In fact, doing that is a very safe way to look at an eclipse. It’s the projection method. (NEVER LOOK THROUGH THE EYEPIECE OF A TELESCOPE OR THROUGH BINOCULARS AT THE SUN UNLESS YOU HAVE A SPECIFIC SOLAR FILTER ON YOUR TELESCOPE!!!!!)

The Eclipse Continues

eclipse view — The relative positions of the Sun, Moon, planets on August 21, 2017 during eclipse totality in parts of the U.S. Click for a larger view.

Okay, so, the eclipse booms along and suddenly the Sun completely disappears. That’s called “Second Contact” and is the beginning of a very brief period of about 2.5 minutes where you can directly observe the Sun. Do it. You might see streamers of the ghostly white corona radiating out from the Sun. You might also see reddish outbursts on the edge — those are called prominences. Don’t forget to look around you and see how dark the atmosphere is. Also, you probably can’t miss all the yelling and screaming and laughter from the people around you. Animals may get in on the act, too. It’s a unique few minutes; savor it the sights, sounds, and feels. But, don’t get too comfortable because totality comes to an end all too soon. Before it does, look around to see if you can spot Mars, Mercury, and Venus.

When the Moon starts to reveal more of the Sun, that’s “Third Contact” and its time to get those eclipse glasses back on. Don’t stop looking though; you still have an hour to watch as the Moon slips away and slowly uncovers the entire surface. When it completely clears the Sun, that’s “Fourth Contact”, and the eclipse is over. You will, of course, have kept your eclipse shades on and did NOT LOOK THROUGH A TELESCOPE AT THE SUN (unless you KNOW it has a safe viewing solar filter).

There’s a lot more to the eclipse viewing experience and I recommend the American Astronomical Society’s page about what you’ll see, hear, and feel during the August 21, 2017 solar eclipse.

Strange Things That People Believe about an Eclipse

A few years ago I was headed to see an eclipse and mentioned it to a person I met at a tourist spot. She immediately went into a whole tirade about how it would mess with my cosmic aura. She wanted me to wave some burning sage around over my head during totality. I’m sure that there’s some spiritual thing associated with that, but she never really explained it, just urged me to smudge the spirits away. I noped my way outta that one.

Another person I met while standing in line at the airport one year told me that as a kid, he and his family always hid inside during eclipses to keep the bad ghosts away. I couldn’t imagine missing something so spectacular due to such a misguided “belief”. But, they’re out there, along with the people who think that setting off fireworks during eclipses is a thing. It’s really a very natural phenomenon, and of course, gurus, shamans, and others who want to put their mystical interpretations on it. But, they shouldn’t keep you from enjoying this very cool show courtesy of the Sun and Moon.

The best thing to do about an eclipse is enjoy it. We all live under the laws of orbital mechanics, but it’s not very often we get to see them in action quite so dramatically.

Get out there if you can. And, when you do, enjoy! It’s a perk of living on a planet, with a star, and a Moon.

2015 MU69 Occults a Star

sofia occultation run — SOFIA cartoon showing flight path of airborne observatory catching the occultation; observers also watched it from the ground. Courtesy NASA

On January 1, 2019, the New Horizons spacecraft is going to pass close to a Kuiper Belt object called 2014 MU69. Not much is known about this distant little world, so it’s important to know how big it is, whether it has companions or a debris field or even a ring around it. Most importantly, the New Horizons team needs to get a very precise fix on the object’s position and orb it so they can plan the flyby to gather maximum science with minimum danger to the spacecraft. This is very similar to work done by the team as their spacecraft approached Pluto in 2015 during the fantastic flyby exploration of the distant planet.

One way to get that information is to watch as MU69 passes in front of (occults) a star. As the star “winks out” and then reappears, the team can get a much better guide on the position and size of the object. So, the team gathered star position data using a star catalog amassed by observations using the European Space Agency’s GAIA telescope, and the positions of the object gathered by the Hubble Space Telescope to plot out a series of occultation observations. The second of those observation runs took place on July 10th aboard the SOFIA aircraft high over the southern hemisphere skies. Groups of ground-based observers also looked for the occultation, as well.

This is an incredibly tough set of measurements to make. MU69 is not very bright, it’s small, and its very far away. The good news is, the SOFIA observers reported they were able to fly through the “shadow” of this tiny world and get occultation measurements. It’ll be a short while (perhaps a few days) before we know the full results, but coupled with the ground-based info, the chances are very good that we’ll know more about this little object. That’ll be of immense help to the New Horizons planners as they chart the close flyby in less than a year and a half.

Occultations and their Meaning for New Horizons

So, how can an object occulting a distant star reveal information about the object?

If you know the distance of the object, you can use simple geometry to figure out at least one of its dimensions using time it takes for the object to traverse in front of the star. The starlight winks out (or dims) at one point and then some minutes (or hours) later, it comes back. Astronomers can use that to plot an angular distance that the object traveled as it passed in front of the star. Imagine watching a car pass in front of a tree. You note the time it begins the pass, and then note when its rear bumper clears the tree. That gives you the time it took to occult the tree. If you know how far away it is, you can the figure out how long the car is. Occultations by asteroids are most commonly studied, as well as occultations of stars by the Moon.

Multiple occultations from different places can also help astronomers understand more about the object’s shape. Different parts of the object will occult the star at different times, and when you put all that data together, you will get a rough estimate of the “roundedness” or “lumpiness” of its shape (what planetary scientists refer to as its “morphology”). If there are multiple occultations before and after the main occultation, that might be a clue to the existence of a ring system or moons or co-orbital objects (maybe it has a clump of objects traveling with it).

For planets and other solar system objects, the more distant stars act as an indirect measuring stick that reveals a lot more information than you’d think. While it’s likely not an issue at MU69 (but never say “never”), an occultation could also reveal whether it has an atmosphere or not. The starlight passing through that atmosphere would absorb certain wavelengths of light, and that would show up in a spectrum of the starlight taken during the occultation.

We Should Hear Soon from the New Horizons Team

I hope we hear soon from the New Horizons team about this set of occultation studies. The first one was somewhat inconclusive, but this one appears to be successful. You can follow the news at the New Horizons mission web site, and on Twitter using the hashtag #mu69occ — presumably, there’ll be an announcement in the next few weeks, once the data analysis is complete.

Other Observations Today

Also, keep an eye out for images from the Juno spacecraft. It’s flying over Jupiter’s Great Red Spot today and the images should be downright amazing! Look for those in a few days, too.

The Spacewriter's Ramblings

Monthly Archives: July 2017

The Shadow of the Eclipse Approaches