This summer will be a little bit longer than usual. A tiny little bit: one second, to be precise. The world’s official time keepers are adding a single second to the clocks at the end of June. This "leap second" is needed to keep various time scales in synch. It’s a bit of a pain and won’t really affect people much, but if it weren’t done things would get messy eventually.

This gets a bit detailed — which is where the fun is! — but in short it goes like this. We have two systems to measure time: our everyday one which is based on the rotation of the Earth, and a fancy-schmancy scientific and precise one based on vibrations of atoms. The two systems aren’t quite in synch, though, since the Earth counts a day as a tiny bit longer than the atomic clocks say it is. So every now and again, to get them back together, we add a leap second on to the atomic clocks. That holds them back for one second, and then things are lined up once again.

There. Nice and simple. But that’s spackling over all the really cool details! If you want a little more info, you can read the US Naval Observatory’s press release on this (PDF).

If you want the gory details, then sit back, and let me borrow a second of your time.

Time after time

There are lots of ways of keeping time. The basic unit day is based on the physical rotation of the Earth, and year is how long it takes to go around the Sun. But we need finer units than those! So we decided long ago to divide the day into 24 hours, and those into 60 minutes each, and those into 60 seconds each. In that case, there are 86,400 seconds in a day. OK, easy enough.

For most of us, that is enough. But scientists are picky (or "anal" if you want to be technical) and like to be more precise than that. And the thing is, the Earth is a bit of a sloppy time keeper. Tidal effects from the Sun and Moon, for example, slow it a bit. Other effects come in as well, changing the rate of the Earth’s rotation.

To account for this, in 1956 the International Committee for Weights and Measures made a decision: we’ll base the length of the second on the year, not the day. In fact, we’ll take the year as it was in the year 1900 (a nice round number, so why not) and say that the length of the second is exactly 1/31,556,925.9747 of the year as measured at the beginning of January 1900^*.

OK, fine. Now scientists have their anal precise definition, normal people have calendars, and we’re all happy, right?

Right?

Sunrise, sunset

Yeah. Not so much. (more…)

[Apologies, folks, I totally forgot to update this post with the link. Hopefully most of you figured out how to find it. I'll do better next time; I'll make a checklist. ]

I will be doing a live video chat session — what I call Q&BA — on Google+ today at 20:00 UTC (3:00 p.m. Eastern US time). I’ll be using Google+’s Hangouts On Air, which lets an unlimited number of people watch live.

I’ll post a link to the Hangout chat session here when it goes live. You don’t have to sign up for Google+ to see it, but it does help in three ways: 1) whenever I do this again you’ll be notified more in advance by following my posts there; b) when you go to the post with the embedded video stream you can +1 it (G+’s version of liking something) so I can get an idea of how many people are following; and γ) Google+ is pretty cool and you should probably be on there anyway.

I will take questions from folks by reading the comments in the Hangout post, and also on Twitter. A little while after we’re done (it’ll last about an hour, I’m thinking), I’ll post it to YouTube so even if you can’t make it live, you’ll still be able to watch at your leisure.

Hope to see y’all there!

This is a wonderful, wonderful time lapse video made by Minnesota photographer Mark Ellis put to the music of Peter Mayer.

You absolutely must make sure it’s in HD and make it full screen.

I am a lifelong appreciator of music, both listening to it and making it. As much as I love hearing an artist’s creation, there is an amazing synergy that occurs when we get a visual to go with it. Perhaps that’s why I love movie soundtracks so much; two different senses combined add up synergistically to more than their arithmetic sum. This video and the music exemplify that beautifully.

I am very impressed with the photographic work in this, and that’s not even including the incredibly cold conditions under which a lot of it was made! And as an astronomer I have to add a couple of notes. Pay attention at 4:00; the lyrics to the song say, "… counting galaxies like snowflakes…", and Mark artfully puts in a view of M31, the Andromeda Galaxy. I particularly like the shots where foreground trees are in focus while the sky is out of focus; you can really see the colors of Orion’s stars.

Also, in several of the shots, as stars go by I see points of light that are stationary in the sky. I suspect these are geostationary satellites, man-made satellites with orbits 24 hours long. That means they revolve around the Earth at the same rate at which we spin, making them appear to hang motionless (or nearly so) in the sky even as the stars rise and set around them.

You can find out more about the music at Peter Mayer’s website, and more about Mark Ellis’s photography at his site. I hope Mark makes more videos like this. A lot more.

Apparently I could do nothing but post incredible time lapse videos all the time. Watch this staggeringly beautiful video, "Yosemite", and be in awe.

[YES, make it full screen and HD!]

The video was made by Sheldon Neill and Colin Delehanty, and the music? "Outro", by a group called M83.

Ha! That’s the name of a spiral galaxy I’ve written about once or twice before. Even thrice. And it’s appropriate, given how prominently our own galaxy features in this video.

The shots of the park during the day aren’t too shabby, either.

I’ve lived out west for twelve years now, and I’ve never made it to Yosemite park. Maybe it’s time to change that.

Tip o’ the piton to Chris Perriman.

In July of last year, I wrote about a comet that passed extremely close to the Sun. Astronomers have now had a chance to pore over that data, and were able to determine some very cool stuff.

First, here’s the video of the comet’s fiery demise (watch it in HD to make it easier to spot the comet):

See it? It’s faint, but there. Actually, there are a lot of observations from multiple observatories and detectors, which allowed astronomers to find out quite a bit about this doomed chunk of ice and rock.

For one thing, it was screaming along at about 650 kilometers per second (400 miles/second) as it flamed out. To give you an idea of how flippin’ fast that is, it would’ve crossed the entire United States in about eight seconds.

Yeah, I know.

It also passed an incredible 100,000 km (62,000 miles) above the Sun’s surface. Have you ever stood outside on a hot day, and thought the Sun would cook you? Now imagine the Sun filling half the sky. That’s what that comet saw. No wonder it disintegrated.

As it approached the Sun, it was watched by NASA’s Solar Dynamics Observatory. In its final 20 minutes or so, the comet broke up into a dozen pieces ranging from 10 – 50 meters in size (and no doubt countless smaller ones too small to detect), with a tail of vaporized material streaming behind it that went for thousands of kilometers. For that size, it would’ve had a mass of hundreds of thousands of tons — about what a loaded oil tanker weighs on Earth!

We’ve learned a lot about how comets break up and disintegrate by observing this event, but it’s raised further questions: like, why did we see this at all? Comets are faint, and to be able to see it this way against the bright Sun is odd. It was definitely one of the brightest comets seen, but it’s interesting to me that it appears to glow in the ultraviolet, as it did in the above video. That means, at that wavelength, it was brighter than the Sun! It wasn’t like a meteor, burning up as it slammed through material, so some other process must have affected it. I suspect that the Sun’s strong magnetic field may have had something to do with it; in the far ultraviolet magnetism is a strong player. Gas under the influence of intense magnetic fields can store a lot of energy, which is why sunspots — themselves the product of magnetic squeezing — look bright in UV.

Perhaps as the comet broke up, the particles inside got excited by the magnetic fields of the Sun and glowed. I’m no expert, and I’m spitballing here. The thing is, no one is exactly sure. But that doesn’t mean we won’t find out. Nothing makes a scientist’s noggin itch as much as a mystery like this, something apparently misbehaving.

One of the single most important words in science is "yet". We don’t know yet. But we will. Someone’ll figure this out, and we’ll have one more victory in our quest to better understand the Universe.

Science! I love this stuff.

Credits: Credit: NASA/SDO; SOHO (ESA & NASA)

There’s been a lot of exoplanet news lately! Part of that is due to the American Astronomical Society meeting recently — in fact, there was so much I wrote four articles just from that (Part 1, Part 2, and Part 3, and Part 4). This next story wasn’t released at the meeting, yet may honestly be the most mind-blowing of them all.

Astronomers have found what appears to be a planet literally boiling away from the blast-furnace heat of its star.

Holy cosmic oxyacetylene torch!

[Image: Reign of Fire by the extremely talented space artist Inga Nielsen. She has prints of them for sale, too!]

There’s a bit of a back story here. The star, KIC 12557548, is about 1500 light years away, and is one of many thousands being observed by the orbiting Kepler Observatory (KIC stands for Kepler Input Catalog, a list of stars under Kepler’s watchful eye). The observatory stares at one spot in the sky, looking for stars whose brightness dips periodically. There can be many causes of such behavior, one of which is the presence of planets orbiting the star and blocking the light from it as they pass in front of it. This is called a transit, and has proven to be wildly successful; hundreds of planets have been discovered this way.

What the authors of this new study are saying is that they see a periodic dip in the brightness of KIC 12557548 every 15.685 hours. Yes, hours. The star is a bit smaller and cooler than the Sun (a K star with about 0.7 times the mass of the Sun, if you want specifics), but even so, the planet must orbit the star a mere 1.5 million kilometers (900,000 miles) from its surface — that’s less than four times the distance of the Moon from the Earth!

That’s close. You’d expect the planet to be cooking… and you’d be right. It’s probably somewhere around 2000°C (3600°F).

Usually, with most planets, the amount of light blocked as the planet passes in front of the star is the same every time. That makes sense, because the planet itself isn’t changing. But not for KIC 12557548. What they saw was that every transit was different. Sometimes more than 1% of the light is blocked, sometimes they detect no dimming at all at the appointed time. That’s really weird.

They looked at and eliminated a few different scenarios, but the fact that the planet is that close to the star really leaves just one idea: a rocky world, probably half the diameter of Earth, being vaporized by the heat of its parent star^*.

Yegads.

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