astronomy

The Mars/Moon Hoax Rears its Ugly Head

Well, the hysterical claims are starting up yet again. Yes, it’s the annual Mars/Moon madness again. Only this time, the folks claiming that the Moon and Mars will be the SAME SIZE OMG!!! NEVER AGAIN IN THIS CENTURY!!!! are claiming that on August 27th, 2014, we’ll be treated to a view of the Moon AND Mars both the same size in the sky.  The stories are accompanied with an image that implies they’ll be *thisclose* in the sky.  The whole idea is so screwed up it’s not even close to reality.   But, before I get to work dismantling the latest flight of fancy about this subject, the good news is that there is something neat to see in the sky that night (and indeed, for the next couple of weeks).  I’ll talk about that in a minute (below the jump).

Mars and Saturn appear close together as dots of light in the August 27th, 2014 post-sunset sky. The moon is a very slim crescent close to the horizon.

Mars and Saturn appear close together as dots of light in the August 27th, 2014 post-sunset sky. The moon is a very slim crescent close to the horizon. (Click to get a bigger version.)

Here’s a star chart that I made using Stellarium for the period of time just a few minutes after sunset on the 27th. This shows the sky with indicators for where the Moon and Mars will be. They are roughly 45 degrees apart — nowhere near each other, as it turns out.  So, that immediately puts the lie to the images I’ve seen showing two Full Moons next to each other (apparently one of them is supposed to be Mars). The insets show about how these objects will really look. The Moon will be a very young crescent (NOT FULL, as is shown in some of the graphics I’ve seen). Mars and Saturn will appear as dot-shaped  objects in the twilight. As it get darker, they’ll look brighter (since we won’t be contending with the twilight glow), but by that time, the Moon will have set. The chart doesn’t lie. You can go to Stellarium, download the free program, run it and see for yourself. It’s easy to do. Where did this huge misunderstanding come from? Apparently someone a few years ago misread (or didn’t understand) an article written about an appearance of Mars in the sky in 2003. The article said that if you looked at Mars through a telescope at that time, the image would be magnified 75x (75 times), and that magnification would make Mars look (through the eyepiece) as big as the Full Moon does to the naked eye. So, the article was making a comparison between two objects, one far away viewed in a telescope and the other closeup viewed with the naked eye (that is, without magnification). The writer was attempting to show that the Moon looks big to us (it’s close, so it should), and that Mars is so far away (even at its closest) that we need magnification to make it look as the Full Moon does to our naked eyes.  It was a size-distance comparison. During that time (in 2003), Mars was at a point in its orbit where it was closer to Earth than anytime in 60,000 years. So, as most urban legends go, a whole new meme was born. It’s usually expressed with lousy pictures (doctored in Photoshop), lots of exclamatory material, and a complete conflation of misunderstanding about the difference between a magnified view of something and a naked eye view. Continue Reading

It’s a World-wide Science

Astronomers without Borders brings astronomy to people around the world. Courtesy AWB.

In July I wrote about the Astronomers Without Borders Indiegogo campaign called “Telescopes to Tanzania”.  The group’s campaign can use a boost and I’m happy to urge you to consider supporting it. AWB spreads the news about astronomy throughout the world, and there’s NO reason why kids in Tanzania shouldn’t get to learn about the same science that kids in other countries get as a matter of course. So, if you’re flush with some bucks (and that might not be more than the cost of a trip to Starbucks), head over there and help ‘em out. And, don’t forget to share your generosity and thoughts on their comments page and through Twitter and other social media. Help spread the word, okay?

Still not convinced? How about participating in “Dollar Donation Day” for the Indiegogo Campaign? Any amount, from a dollar and up will count toward the goal. And, share the fundraising link with your friends!  Head over to their campaign and shake your wallet loose. And, while you’re at it, join and or contribute to AWB’s awesome work to bring astronomy to everybody, regardless of where they live!

Cassini Captures Cloud Movement Over Ligeia Mare

An animated gif of clouds moving across Titan's northern Ligeia Mare (sea). Watch the clouds over the dark area lower center/right. Credit: NASA/JPL-Caltech/SSI

An animated gif of clouds moving across Titan’s northern Ligeia Mare (sea). Watch the clouds over the dark area lower center/right. Credit: NASA/JPL-Caltech/SSI

If you’ve ever been aboard a sailing ship, you probably know the sensation of the craft cutting through the ocean, wind at your back and a breeze in your face. It’s probably the same sensation you get when you go hang-gliding, or water (or snow) skiing.

It turns out, if you lived on Saturn’s icy but intriguing moon  Titan, you could experience the same sensations (provided you could survive the atmosphere and cold temperatures). Of course, your ship would need to be able to withstand the frigid methane sea, and the cold, largely nitrogen (with small amounts of methane and hydrogen) atmosphere.

The clouds would be made of methane, possibly some ammonia, and other hydrocarbons. Feeling the breeze on your face would require you to withstand an atmospheric pressure about 1.5 times that of Earth’s sea level, and near-surface temperatures of about 94 Kelvin (-297 F, or -179 C). Not impossible, but right now, pretty improbable. That’s why we have the Cassini-Solstice Mission — to give us a spacecraft-eye view of what it might look like from above.

So, what would a cloudy, breezy sea day on Titan be like? Cassini scientists just released an animation of clouds blowing across the surface of the northern Titan sea called Ligeia Mare. In the sequence (which you can see here), the clouds blow just over the hydrocarbon-rich sea at speeds of around 7 to 10 miles per hour (3-4.5 meters/second). These images were taken a few weeks ago (late July), and the formation of the clouds and their actions may be harbingers of summer on Titan.

Titan does indeed have seasons during its 30-Earth-year-long year. Each of those seasons lasts about 7 Earth years, giving plenty of time for seasonal change to occur. When Cassini first arrived at Saturn and began studying this moon, its northern pole was pointed away from the Sun, which put it in high winter. At that time, the north polar region was shrouded with a hazy hood. There was a lot of cloud activity in the southern hemisphere (during its summer, when things were a bit warmer (relatively)).

As equinox approached, when both northern and southern hemisphere Titan got equal amounts of light and heat from the Sun, the northern polar hood shrank. Cloud activity continued for a while, until the passing of a large storm in 2010. Then, cloud activity dropped quite a bit. In the approach to northern hemisphere summer (southern hemisphere winter), the northern hood nearly disappeared, and now that we’re starting to see northern summer and southern winter. This latest discovery of clouds above a northern hemisphere ocean could signal summer weather patterns. Their appearance also leads the science team to speculate about whether (or how) the clouds are rela ted in some way to the seas. It’s possible that clouds form over the seas as a matter of course, but it’s also possible that Cassini just happened to catch some clouds racing over the ocean surface as part of a larger-scale circulation pattern.

Cassini will continue studying atmospheric change at Titan during the upcoming northern hemisphere summer (southern hemisphere winter). Already it has given us a great deal of information about the only other world in the solar system (besides earth) that has a fully developed atmosphere (and could possibly be habitable to certain forms of life). Stay tuned!