Annular Solar Eclipse – May 20, 2012

If you haven’t heard, there’s going to be an annular solar eclipse on Sunday, May 20, 2012. For a REAL astronomer’s take on it, I recommend going to Dr. Plait’s blog HERE and HERE. And, of course, the most thorough rundown can be found at the NASA Eclipse Site.

Essentially, an annular eclipse is one in which the moon eclipses the sun sufficiently close to its apogee that it blocks all but a ring of the sun’s surface. Since we just had a “Super Moon” when the moon was at its perigee on the other side of Earth almost two weeks ago, the moon is now at its apogee as it blocks out the sun. Cool, huh?

I live in north Texas, so I’m out of luck seeing the whole eclipse with my own eyes since the sun will set just before the eclipse reaches totality. Even so, I’m not sufficiently in line with the moon’s shadow to see an annular effect in any case. However, with my Android phone and Google Sky Map, I won’t have any problem monitoring the eclipse in real time.

The eclipse begins at 15:56 CDT. Here’s how that will appear on my phone:

Eclipse begins

And at sunset (note the horizon line), just before totality, here’s how things will look:

Eclipse before sunset

For those who witness totality, I’d be interested to know if it was dark enough for Jupiter or Mercury to be visible. Also, if you’ve been tracking the planets, you should be able to answer this question: If Mercury is visible during totality, what will its phase be? You’ve got two choices.

CAUTION: DO NOT LOOK AT THE ECLIPSE WITH UNPROTECTED EYES. JUST DON’T.

As the moon approaches the sun, Sky Map shows it crossing in front of Jupiter. However, that’s just a consequence of Sky Map’s tendency to render planets much larger than they actually appear in the sky. Still, it’s fun to see the sun, Jupiter, Mercury, and the moon so close together.

People (like me) who are somewhat off to the side of the moon’s shadow will not witness totality. They will instead see a crescent sun as the moon obscures a large portion of the sun’s southern or northern hemisphere. If you’re in this situation, and you’re monitoring the solar eclipse in real time on Sky Map, set your location to Albuquerque, NM. People in that city will see totality. Does it look any different than it does in north Texas (depicted above)?

This is the amazing thing about having an app like Sky Map. If you’re stuck in an office cubicle, if the weather’s cloudy, or if you’re not in the right place on Earth to see the eclipse, you can still watch it as it happens on your phone. Yeah, I know, it’s just an app with a digitally-rendered sky. But try it anyway. If you watch the eclipse on your phone as it’s happening, trust me: you’ll feel a connection to the sky that can’t be described. There’s no feeling like it.

Life. You Know? (And Mercury/Pluto Conjunction Coming Up)

Some astronomy blog this turned out to be. Holidays, job, and writing in my spare time have all conspired to keep me away from here.

And it couldn’t have come at a worse time. I missed blogging about:

• The solstice
• Earth’s perihelion
• Comet Lovejoy (I mean, come on!)
• The tidally-induced lava storms of New England
• The reversal of Earth’s magnetic field
• Lightning bolts on the moon
• The explosion of Jupiter (Wasn’t that cool?)

Okay, some of those things didn’t actually happen, but if they had, I wouldn’t me more ashamed.

But here’s some good news: Mercury and Pluto are doing a little dance near the constellation of Sagittarius. They’ll reach their minimum angular separation about January 13.

How cool is that? The closest planet from the sun and the farthest planet from the sun, coming together in the sky? Right? Okay, Pluto isn’t a planet anymore, but I’m not going to let that ruin my day. (And ten points to the first one to identify about how often Mercury and Pluto do this. And, no, I’m not going to let that ruin my day either.)

Even more remarkable, this conjunction will occur only an hour west of the sun, so it can’t be observed with earth-bound telescopes. The only way to observe it is with a tool like the one you have in your hand. With your Android phone, you have the opportunity to see what’s going on in the blue, daylight side of the sky. So take a look, watch how fast Mercury gains on, and then passes, Pluto in the sky.

And while you’re at it, take a moment to think about the power in the palm of your hand. You have a tool that opens up half the infinite sky. Now go ahead. Take a look around. I know you want to.

The Search Has Landed – December 2011

This is the (semi)monthly feature in which I catalog the most notable searches that have landed at this site and do my best to answer any burning questions they might entail.

What observational technique allows astronomers to determine that Venus is rotating backwards?

Good question. Venus is shrouded in a cloudy, totally featureless atmosphere that prevents us from seeing it surface, so it’s impossible to determine rotation by telescope observation.

But we have imaged Venus’s surface with cloud-penetrating radar. And do you want to know the amazing part? We first did this from Earth. So from Earth, we bounced a radar beam off of Venus and found features big enough to see from here that allowed us to determine its period (and direction) of rotation.

We have since sent exploratory probes to Venus and probed its surface in much greater detail, but I don’t think sending probes counts as an “observational technique”. But sending radar from Earth does count, even if it’s not something amateur astronomers are equipped to do. Besides, it’s really cool, to boot.

 If you lived at the equator, what differences would you notice between the solstices?

The solstices (winter and summer) are the moments in time when the sun is farthest north, or farthest south in the sky. Even from the equator, the sun on the December solstice will rise south of due east and set south of due west. And on the June solstice, the sun will rise north of due east and set north of due west.

Other than that, I can’t think of anything.

Google Sky Map can’t find moon

Deepak? Is that you?

If a planet has a tilt of 15 degrees, what would be the line of latitude of the Tropic of Cancer?

It’s actually as simple as can be. The Tropic of Cancer would be 15 degrees north, and the Tropic of Capricorn would be 15 degrees south since these would be the boundaries of the sun’s north-south sweep through the sky throughout the year.

I love it when things are simple. Not like that Venus thing.

The Search Has Landed – November 2011

This is the (semi)monthly feature in which I catalog the most notable searches that have landed at this site and do my best to answer any burning questions they might entail.

If you lived on Mars, which planets would appear to go through phases?

Wow, that’s a good question. From Earth, we see some planets go through phases, but not others. We know from looking at the moon’s phases that our vantage point has a lot to do with that. So wondering what a Martian vantage point is a reasonable (but very big) next step.

The planets we see going through phases are Mercury and Venus because they can come between us and the sun. Mars, not so much. But from the perspective of Mars, all three inner planets — Mercury, Venus, and Earth — would appear to go through phases, because all three have orbits that take them between Mars and the sun. The outer gas giants can’t come between Mars and the sun, so they would still be phase-less.

I’m at the North Pole, and you are at the South Pole, can we ever see the same stars?

In practical terms, no, we can’t ever see the same stars.  Never.  But if one or both of us were to ascend a step ladder, then our views of the sky would begin to overlap slightly at the equator.  The higher you elevate your eyes above the ground, the less sky the horizon obscures.  It’s all a matter of degree, and we may be able to find a handful of stars that we both can see as a consequence of elevation and terrain.  But under theoretically ideal conditions (Earth is a smooth ball, eyes close to the ground), we wouldn’t be able to see the same stars at all, ever.

Can androids detect the rotation of the Earth?

Yes, they can.  And they can detect the firing of the neurons in your brain that control your trigger finger and react with deadly force before your first shot even leaves the barrel.

At least, that’s what I’ve heard about the upcoming Ice Cream Sandwich  update.

Android Calendar Solstice Moon

These are all things I discuss in my POST OF DOOM! Wait, what?  I never mentioned the moon in that post?  I could have sworn I had…

What a Novel Idea

It’s no secret to many of you that I’ve been writing a science fiction novel. Now that it’s completed, there are going to be a few minor changes around here.

• I’m moving this blog from AndroidAstronomer.com to AndroidAstronomer.net. However, for the time being, you’ll be able to get to this site from either URL. Update your bookmarks accordingly.
• Some time between now and the end of the year, AndroidAstronomer.com will become my author website.
• At the top of each domain’s main page, I’ll place a link to the other so people who end up at the wrong one won’t be too inconvenienced.

That’s it, really. I’m doing it this way because I maintain this blog out of of my love for astronomy, and I’d rather it not be assimilated.

However, if you like to read hard science fiction (and what astronomer doesn’t?), then I’d be grateful if you’d pop on over to my author web site and check out my new book.

That is, as soon as my author web site is up. And as soon as my novel is published. If it ever is. (I remain hopeful.)

Now get back out there and look up.

The Search Has Landed – October 2011

This is the (semi)monthly feature in which I catalog the most notable searches that have landed at this site and do my best to answer any burning questions they might entail.

Why do astronomers travel to the southern hemisphere to observe Mars?

This is a very intelligent question that I haven’t answered here, so I’ll give it a go.  While this question suggests that Mars can be seen only from the southern hemisphere, that’s emphatically not the case, and I suspect the questioner knows it.  Mars is in the ecliptic and can be seen from anywhere on the globe (though not all at once, of course, since Mars has to be on one side of the planet or the other).

However, when Earth is closest to Mars (when Mars reaches opposition), the tilt of the Earth will determine the best place from which to view Mars.  If Earth and Mars are closest in winter (northern-hemisphere centric), then Mars will be highest in the sky for observers in the northern hemisphere.  Likewise, if Earth and Mars are closest in summer, then Mars will be lowest in the sky for observers in the northern hemisphere, but highest in the sky for observers in the southern hemisphere.

This is key, because the lower in the sky an object is, the more atmosphere you have to look through to see it.  And it can be significantly more.  And more atmosphere obscures and blurs objects we’re trying to see.  So astronomers do, in fact, travel to the southern hemisphere to observe Mars, but only if it reaches opposition during the northern-hemisphere summer.  But this can go the other way.  The next time Mars reaches opposition during the winter, then expect a rush of southern-hemisphere astronomers to storm across the equator for more favorable viewing conditions.  And do try not to get in their way.

If Polaris is sighted 35 degrees above the horizon, what is the latitude of the observer?

Polaris is the Northern Star, which means that it’s (very nearly) directly above Earth’s north pole. So if you’re standing on the north pole, Polaris would be straight up, at your zenith, or 90 degrees above the horizon. As it happens, the north pole is also at 90 degrees latitude.

Likewise, if you were standing on the equator, Polaris would be on the horizon, zero degrees above it. And the equator is, lucky for us, at zero degrees latitude.

And everything else in between is everything else in between, in linear fashion. So whatever angle Polaris is above the horizon, that’s the latitude of your location. Therefore, if Polaris is 35 degrees above the horizon, you’re standing at 35 degrees latitude.

It’s pretty cool how that works out, no?

Can you see the same stars wherever you are in the world?

Not quite. Someone at the equator has the best chance of seeing all the stars there are to see. (THAT’s a big thought.) But as you increase your distance from the equator, you diminish your ability to see stars in the opposite hemisphere. Someone south of the equator would probably never see Polaris, for example. If you’re standing on the north pole, all the stars in the southern hemisphere would not be accessible. Likewise, if you’re standing on the south pole, all the stars in the northern hemisphere would not be accessible.

And everything else in between is everything else in between.

Which planets exhibit phases?

Good question. Only the inner planets (Mercury and Venus) exhibit phases from Earth’s perspective, because they’re the only planets that can get between Earth and the sun. You’ll never see a crescent Jupiter the way you see a crescent Venus, because Jupiter is never closer to the sun than Earth.

How long does it take Betelgeuse to rise?

I confess that I don’t really know what’s being asked here. Everything rises in the east and sets in the west. And if you define “rising” as the action of popping into view above the eastern horizon, then that’s not very long for any celestial body.

Celestial bodies are above the horizon about twelve hours at a time, and Betelgeuse isn’t any different.

If the questioner finds this and wishes to clarify, I’ll certainly take another stab at it.

When is Dark Nebula going to be on Android?

Since I define what a Dark Nebula is in my glossary, that’s where this search landed.  But I suspect the searcher is looking for a game of some sort.  Sounds like a fun game.

Do you think the searcher stuck around?

Ecliptic Feature in Sky Map

A recent update in Sky Map features the ecliptic, which is depicted as a huge circle in the celestial sphere with Earth at its center. The ecliptic is the plane of Earth’s orbit around the sun, and all the planets, our moon, and the sun (of course) can be found near the ecliptic. This will make finding the planets much easier than it’s been in the past.

Though the changing seasons appear to shift the angle of the ecliptic with the horizon, this is just an illusion, since we regard the ecliptic almost exclusively at night. Seeing the ecliptic during the daytime and on the other side of Earth will help you gain a bigger picture of the ecliptic relative to the horizon and the changing seasons.

The sun will always be dead center on the line of the ecliptic, as will Earth. When you get a chance, check out the moon and see how far it is from the ecliptic. If the moon were exactly in the ecliptic, we would get a solar eclipse every new moon. But the moon’s orbital plane is tilted slightly with respect to the ecliptic.

And since a tilted ring must intersect a plane at two points, the moon will be in the ecliptic twice during each lunar cycle. (Mostly, anyway. Remember, the lunar cycle rotates as Earth orbits the sun, skewing the phase cycle with respect to the moon’s orbit.)

Knowing that the moon must be in the ecliptic when it is new, you can now track the moon and make a decent stab at predicting solar and lunar eclipses. Though Sky Map doesn’t give you the precision you need to predict such events accurately, it’s still fun to watch even a “near miss” as you track the moon’s oscillation above and below the ecliptic.

This is an amazing time we live in. Familiarity with the sky has never been more attainable.

The Search Has Landed – September 2011

This is the (semi)monthly feature in which I catalog the most notable searches that have landed at this site and do my best to answer any burning questions they might entail.

Which objects are more easily located knowing where the ecliptic is?

This search landed at the Ecliptic category page, where you’d have to do a lot of reading to get your answer.  Not that that’s a bad thing, but the quick answer is that the ecliptic is strictly defined as the plane of Earth’s orbit around the sun.  But the more common loose definition is that the ecliptic is the plane of the entire solar system.  So in the plane of the ecliptic, you will find all the planets, the moon, the sun, the asteroids, and even most comets.  Objects in the plane of the ecliptic also transit the constellations of the Zodiac.

Define Skymap Nadir

I suspect the originator of this search saw the word “Nadir” in Sky Map and sought its definition.  This search would land you in the Glossary, where you’d learn that the Nadir is…  Hold on just a sec.  What?  It’s not in the glossary?  Well, that’s just embarrassing.

Okay, I’ve updated the Glossary, and now you all look crazy for saying it wasn’t there.

Oh, right.  The definition.  The Nadir is the point on the celestial sphere that is directly below your feet.

Ecliptic is Higher

I love this one, because this obviously came from someone who’s monitoring the sky and noticed that the nighttime ecliptic rises higher above the horizon as winter approaches.  This person truly has the heart of an astronomer.  This search landed at Getting to Know the Sky: Part 2, which fully explains the phenomenon the searcher is questioning.

Since Earth’s orbit is a little bit closer to the sun in January than July, rank the two hemispheres, norethern and souther, in order of which should have the larget seasonal change in temperatures: northern hemisphere, southern hemisphere.

Yikes! Okay, this is an excellent question. For us northerners, winter is closer to the sun, and summer is farther away from the sun. For you southerners, it’s just the opposite. It makes sense, therefore, that northern seasons would be less extreme.

We can calculate the difference this makes. The minimum distance between Earth and the sun is 146 million kilometers, and the maximum distance is 152 million kilometers. Knowing that the heat we receive from the sun is inversely proportional to its distance squared, we can calculate that Earth receives about 8% more heat in January than in July. So the southern hemisphere’s seasons should be about 8% more extreme. That’s nothing to sneeze at.

But it’s not that simple. Earth’s atmosphere and vast oceans add a drastic amount of hysteresis to its heat cycle. Moreover, the northern continents significantly block the ocean’s heat-distributing ability, which is not the case in the southern hemisphere.

Consequently, instead of the northern seasons being less extreme as a result of the eccentricity of Earth’s orbit, it’s the southern hemisphere that enjoys this moderation, thanks to the oceanic heat sponge that dominates the southern hemisphere. So it’s the northern hemisphere that has more extreme seasons, even though this 8% difference is fighting against it.

But Earth’s axis wobbles a bit, so in about 13,000 years or so, the effect will be reversed. The southern hemisphere will still enjoy moderation of its extremes as a result of the oceans, but the northern hemisphere will experience even more extreme seasons than it does now.

Age of Starlight

We live in a remarkable time. Had we lived billions of years earlier, we wouldn’t have been able to measure the acceleration of the expansion of the universe, and we would never know about dark energy or the ultimate fate of the universe. Were we to live billions of years in the future, we would live in the Milky Way/Andromeda supergalaxy, with no observable structures outside our galaxy, and no evidence of a Big Bang. Though our galaxy would be huge, that’s all we would see of the observable universe, making the universe seem cramped compared to what we experience now.

Live too soon, and knowledge of the future is cut off. Live too late, and knowledge of the beginning is inaccessible. Of all the times to be alive, to be curious about the wonders around us, this moment in time couldn’t be more revealing or more amazing.  Only in this brief moment in the life of the universe can we gain knowledge of both the beginning and end of time. Only now can we see the the universe in all its glory, throughout all its ages, laid out before us.

The Perseid meteor shower peaks tonight. If you get a chance, lie down on a blanket after sunset and see what you can see. Now is the perfect time.

Product Review: TerraTime

My favorite gadget in the whole world has got to be my Yes watch. An Android phone, it seems to me, would be a great platform on which to replicate and expand on this kind of functionality. Fortunately,  TerraTime has risen to the occasion. More than just a clock, TerraTime connects us to the solar and lunar cycles that impact our lives on Earth.

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