February 20, 2013

Checking out JupiterMoons

Yesterday was a beautiful day in the Seattle area and the evening began mild and clear, so I decided to take a break from some work tasks, drag the telescope out to the deck, and have a few quick looks at Jupiter. It was also my first time to give a test drive to the new “JupiterMoons” iPhone app that I purchased from Sky & Telescope a couple of weeks ago.

The “Jupiter’s Moon” app for iPhone from Sky & Telescope
magazine shows you at a glance which of the planet’s Galilean
satellites is which, and also includes times for the day’s events
involving the moons and the Great Red Spot.
JupiterMoons doesn’t give away any secrets. You can get the same information from your favorite astronomy magazine or software package. In fact, S&T has Javascript utilities on its website that do the same things. But there are three advantages to the app that I can think of.

First, my iPhone is almost always in my pocket, so whenever I wonder what’s up with Jupiter the answer is handy. Second, on the app what you see is what you get. I always find those squiggly charts of Jupiter’s Galilean moons difficult to interpret, and usually have to take off my shoes to translate Universal Time into Pacific Standard. When you fire up JupiterMoons you get a snapshot of which moons are where right now and where you are. You can also look up times past and future. The view can be flipped or inverted to match the view in the gear with which you’re observing. Finally, the app is easy to read at night. There’s even a night mode that runs it in red light—not that we’re getting much in the way of night vision in our city backyards, but the feature may be important if you have a good, dark observing site.

A couple of other features are useful. Tap on the “events” button and you get a listing of the current day’s transits, eclipses, and occultations of the moons and their shadows, and transit times for the Great Red Spot as well. The “learn more” tab leads the user to some quick facts about Jupiter, Io, Europa, Ganymede, and Callisto.

Alas, there were no events going on during the short time I had for observing yesterday, save for the GRS being in view. But I was able to identify the moons, and JupiterMoons would have let me know if there was a double shadow transit or some other notable event coming up later in the night.

JupiterMoons is a great little app to enhance your impromptu viewing sessions. At $3 it’s a steal. It’s available for iPhone and iPad from the iTunes store.

February 12, 2013

Washington Legislature considers measure to allow more digitalbillboards

The Washington State Legislature is considering measures that have the local astronomy community concerned about the potential of increased light pollution in the state. Senate Bill 5304 and an identical companion House Bill 1408 would change the law to give cities and towns in the state the option to allow electronic billboards within their boundaries.

Both bills received hearings Feb. 5 and must be voted on by committees in the next few weeks for the proposal to have a chance to become law. The House Transportation Committee has a deadline of Feb. 22 to take action on HB 1408, while the Senate Transportation Committee has until March 1 to consider SB 5304.

Proponents of the bill–mainly Clear Channel Outdoor Seattle, the billboard company–touted the traffic safety and amber alert messages that could be given via the billboards, as well as support the company could offer through billboard advertisements on behalf of nonprofit enterprises. Meanwhile opponents contended the billboards would be unsightly and create a distraction for motorists.

David Ingram of Dark Skies Northwest spoke on behalf of the astronomy community, raising concern about the light pollution that the electronic billboards would cause, and also alluding to ill effects of nighttime lighting on human health and wildlife.

February 1, 2013

Avoiding asteroid armageddon

NASA’s chief asteroid hunter says one spectacular comet and two lousy motion pictures are probably the reasons that we are keeping a close watch for asteroids or comets that could potentially smack into Earth and wipe out life on our planet.

“The collision of comet Shoemaker-Levy 9 with Jupiter in 1994 sensitized the public to impacts in the solar system,” said Don Yeomans, senior research scientist and manager of the Near-Earth Object Program Office at the Jet Propulsion Laboratory. “Then there were those two dreadful movies around 1998—’Armageddon’ and ‘Deep Impact.’ They sensitized the public. The public contacted their Congressmen, their Congressmen said, ‘NASA, what the heck are you doing about this problem?’”

Thus were born the agency’s efforts to track near-Earth objects.

Yeomans, author of Near-Earth Objects: Finding Them Before They Find Us, spoke last week at Town Hall Seattle. He must know his stuff; after all, he’s got an asteroid—2956 Yeomans—named after him! Yeomans gave an engaging presentation about the history of rocks slamming into our planet, from the football-sized meteorite that wrecked a New York woman’s Chevy Malibu in 1992 to the 10-kilometer asteroid that nailed us 65 million years ago and snuffed the dinosaurs. He noted that asteroids and comets probably delivered the water and carbon-based materials to the early Earth that allowed life to form, but they could potentially destroy life, too.

Near Earth ObjectsYeomans’ job is to make sure that doesn’t happen. He says an army of professional and amateur observers are tracking thousands of near-Earth objects and feeding the data to JPL.

“It’s up to us to compute orbits for all of these objects and run their motions a hundred years into the future to see if any of them make any interesting close-Earth approaches,” Yeomans said. JPL then figures the likelihood of any of these objects actually hitting the Earth.

“If any objects represent a threat we ask for additional observations from the observing community,” Yeomans explained, adding that this helps them pin down an object’s orbit. “As we get more and more data the uncertainties get smaller and smaller and we can run that for a couple of hundred years into the future to see if it is actually going to hit the Earth.”

Yeomans said the probability of something hitting us is not zero.

“There are almost 100 objects on our risk page for which we cannot yet rule out an Earth impact,” he said. “But all of the impact probabilities are very small—one in 10 to the sixth or smaller—so no one should lose sleep over near-Earth objects coming in and taking us by surprise. Still, there are a number of them that we’re keeping an eye on.”

The good news is that there is something we can do about it if we discover an object on a collision course with Earth. In fact, it’s a relatively simple maneuver that we’ve already pulled off: send up a spacecraft and ram it into the thing.

“You could slow it down a millimeter per second and change its orbital period, so in 10 to 20 years when it was predicted to hit the Earth it would miss by a wide margin,” Yeomans said.

His biggest concern is with a comet impact. Comets often aren’t discovered until they reach the orbit of Jupiter. It takes a comet just nine months or so to get from Jupiter to Earth, so if one were headed for us there would be little time to do anything. The good news is that asteroids far outnumber comets, and so a comet impact is a much more remote possibility.

Earlier this month NASA ruled out the chances that the asteroid Apophis will slam into us in 2036, though it will miss Earth by less than 20,000 miles in 2029. Yeomans said they will keep a constant eye out for other near-Earth objects.

“We need to find them before they find us if we are indeed to have a future,” he said.
UPDATE: Speaking of asteroids and Yeomans, Alice’s Astro Info has posted about Asteroid 2012 DA14, which is going to miss us by that much Feb. 15.

Listen to a recording of Yeomans’ talk on the Town Hall Seattle website.