A pair of astronomers monitoring an all-sky camera got a surprise (PDF) when they checked data from last February: a half dozen meteors all seemed to come from the same spot in the sky, indicating they all had a common origin. After doing some calculations, they found that they probably come from a parent comet with an orbit that’s at least 53 years long. Moreover, the orbit of this comet crosses that of the Earth, meaning we may have a close encounter with this object sometime in the future.

And because I can sense the oncoming panic on the web over this news, let me break it down for you. I’ll give you the science (which is cool), how we know this unseen comet may be potentially, um, interesting, then the reason you don’t need to run around in circles screaming (spoiler: it’s rude to others nearby, but also unnecessary).

But just to be up front: should you panic? Nope. We know there are objects out there that could hit us in the future sometime. This comet is in many ways just another one. As I’ll point out below, we pass through lots of meteor streams, so there are plenty of other comets that could hit us. I know, I know, that doesn’t sound reassuring, but think about it: how often is the Earth hit by a comet? Not very often, despite having a few on the list of Potentially Hazardous Objects. So having one more we know about out there isn’t great, but in reality doesn’t really make things any worse for us.

Meatier showers

That picture above is one of the meteors in question. You can see the streak as the tiny bit of rock (probably the size of a grain of sand) glowing as it rammed through the Earth’s atmosphere at about 35 km/sec (22 miles/sec, or nearly 80,000 mph). If you go out on any dark night, you’re bound to see the random meteor or five. But meteor showers are when we see lots of them in a short time, and they occur when the Earth passes through the dust debris left behind by a comet.

Most comets are dirty snowballs: dust, pebbles, and boulders held together by ice (water ice, but also frozen carbon dioxide and other things we normally think of as gases). This makes comets the litter bugs of the solar system, shedding material when the Sun warms them up and turns the ice into gas. The vapor blows off, and the looser material forms a ribbon or stream that stays more or less along the same orbit as the comet.

If the path of the comet intersects the orbit of the Earth, we plow through that material at the same time every year. (more…)

A rock about 10 meters in size will fly past the Earth Monday at 13:30 UTC (09:30 Eastern US time) 17:01 UTC (13:01 Eastern US time) [Note: the time of closest approach was updated this morning, June 27]. It’ll be a particularly close shave — passing just 12,400 km (7430 miles) from Earth’s surface; a bit less than the diameter of the Earth itself — but it’ll miss for sure.

[Update 2: Images and an animation of the asteroid are now up at the Remanzacco Observatory blog; thanks to NickAstronomer on Twitter for the tip!]

We’re in no danger from the asteroid, named 2011 MD, since there’s essentially zero chance it will hit us. Even if it did, it’s too small to impact the surface, and would instead break apart and burn up in the atmosphere. That would be exciting, and make quite a show, but that’s about it.

Here’s a diagram of the asteroid’s trajectory (note that the size of the Earth is not to scale!):

On this scale, the Earth is actually about half the size shown; it was enlarged on the diagram to make it clear. In this smaller diagram here the trajectory is shown from a different angle (edge-on to the Moon’s orbit) with the Earth to scale, and you can see better that 2011 MD will miss us.

You can really see in those diagrams just how much the Earth’s gravity bends the orbit. At this close an approach the Earth’s gravity is significant, and the path of the object will be significantly altered. Just how much it’s changed is difficult to know until observations are made after the event. However, I’ll note the asteroid will be on the daylit side of Earth after it passes, making observations a bit tricky. I expect radar observations will be made using radio telescopes, which don’t need darkness to work and can provide very accurate measurements of the orbital path.

Speaking of orbits, this one is interesting. 2011 MD’s orbit is quite similar to Earth’s around the Sun, taking 396 days to go around once. The orbit is more elliptical than Earth’s, with a semi-major axis of 1.056 AU.

What does that mean? (more…)

Much ado was made over the recent news that the Sun’s magnetic activity may be cooling off over the next few years. Can this mean the Earth itself will literally cool off, slipping into an ice age? Some news sites are reporting it that way (of course, the execrable Daily Mail uses the headline "Earth facing a mini-Ice Age ‘within ten years’ due to rare drop in sunspot activity"; which isn’t even within a glancing blow of reality).

The answer — spoiler alert! — is almost certainly "no". I want to make sure that’s clear, because I will bet essentially any amount of money that some climate change denial sites will run with this story and claim that we don’t need to worry about global warming. That’s baloney, and what follows is why. The reasons take a minute to explain, but of course that’s where the cool stuff (haha!) is. So let’s take this one step at a time. And if you have the attention span of an E. coli bacterium, you can skip down to the conclusion section.

[Note: a lot of this is taken from my book "Death from the Skies!", where I interviewed approximately a bazillion people. One in particular was Caspar Ammann, who was very helpful in explaining the solar connection with the Little Ice Age to me.]

The Quiet Sun

The Sun has a magnetic cycle, its magnetic field waxing and waning in strength roughly every 11 years. The strength and complexity of the solar field governs a lot of the surface activity, including sunspots, solar flares, prominences, and coronal mass ejections.

Right now, in 2011, we’ve just left a period of an extended minimum, and the next max is due in late 2013 and early 2014. But scientists studying the Sun have seen three independent lines of reasoning indicating that the next rise to the solar peak, in 2022 or so, may be delayed or even not occur at all. I wrote about this in an earlier post, so you can get the details there. It’s the core of the "oncoming ice age" claim, so you should read it.

I’ll note right off the bat that not everyone agrees with these findings. Doug Biesecker, a solar physicist NOAA Space Weather Prediction Center [full disclosure: Doug is an acquaintance of mine; I interviewed him for an episode of "Bad Universe" about solar storms] , has written a document calling the findings into question. It’s not exactly a rebuttal; it’s more of a warning not to over-interpret the results. He also points out that a weak cycle may not have an effect on our climate; we simply don’t know for sure.

At this point you may be asking, so what? If the Sun has fewer sunspots and no flares, what difference does that make here on Earth? And how could it possibly trigger an ice age?

(more…)

Perhaps you’ve seen the video of George Hrab and me performing his song "Death from the Skies". And perhaps you’ve seen my own show, "Bad Universe".

Now, thanks to Dana Peters, you can see them together:

After all, these are the real ways the world will end.

Is the solar cycle shutting down?

New results indicate it may very well be, at least temporarily. Even though the Sun is currently approaching the peak of its cycle in 2013, and we’re seeing an increase in activity (more sunspots, flares, and other violent events), there are strong signs that the next expected peak (in 2022 or later) may be weaker, or may not come at all!

Here’s the deal. The Sun is a seething ball of ionized gas, called plasma, and has very complex magnetic fields that interact with this plasma. The overall strength and activity from the magnetic field rises and falls on roughly an 11 year cycle. When the cycle is at its minimum the field strength is weak, and we see few or no sunspots or other activity. Then, a little over five years later, the cycle peaks and there’s lots of fun stuff going on, with flares, coronal mass ejections, and more.

Scientists studying the Sun have been trying to figure out this cycle for over a century. It’s very complex, but as technology has gotten better, some trends have been found. And recently, these indicators are all pointing to the Sun settling down magnetically.

For one, there is an east/west river of gas the flows under the surface of the Sun (it can’t be seen directly, but it generates sound waves that travel from it to the surface, revealing its presence; I describe this in detail in an earlier post). This river comes and goes, but usually forms at mid-latitudes on the Sun and shifts toward the equator as the cycle progresses. As it does so, sunspots form above it. Although the next cycle won’t start for a few years, the river associated with it should already be forming. However, there are no indications it has, making astronomers think the next cycle may be delayed.

For another, scientists have found that the average magnetic strength of sunspots has been declining over the years. Sunspots form when magnetic fields inside the Sun break through the surface. Normally, rising gas from the solar interior would cool and drop back down, but due to the way the magnetic fields interact with the gas, the cool gas is prevented from dropping. Cooler gas is dimmer, so we see this as dark spots on the Sun: sunspots.

Sunspots are an intrinsically magnetic phenomenon, so this trend of weaker magnetic fields inside them may be indicating, again, the next cycle may be delayed or not come at all.

Moving farther outward yet we come to the third line of evidence of a weak upcoming cycle. The Sun has an atmosphere, called the corona, of very thin but extremely hot plasma. It too is greatly affected by magnetic fields; every cycle the magnetic activity in the corona tends to form near the Sun’s equator and then slowly move toward the poles over the next few years. This "rush to the poles", as the scientists call it, is very weak this year, and may indicate that the peak in 2013 may not be terribly active. It’s unclear what this might mean for the cycle peak after that.

So what does this mean for us? (more…)

Is this the most distant object ever seen?

[Click to deathfromtheskiesenate.]

That is GRB 090429B, a gamma-ray burst (or just GRB to those who want to sound nerdcool), the catastrophic and extremely violent detonation of a massive star. Think of it as a super-supernova, the death throes of a star that lived a short, hot, turbulent life. I wrote about them extensively in my book "Death from the Skies!", or you can get the details about how they form and why they’re so awesome in an earlier post.

Its distance is estimated to be a whopping 13.14 billion light years. If this holds up, it may be the single most distant object ever seen by humans.

But is this really a record-breaker? And why aren’t we sure? OK, this takes a wee bit o’ explaining, but I think you’ll like it. After all, it’s an explosion so big it’ll crush your mind into dust.

[UPDATE: Due to a typo in my math notes early on, I incorrectly said the distance to this burst was 13.4 billion light years. D'oh! I have corrected all the numbers below, and I apologize for the error.]

Boom! goes the dynamite

The important thing here is that they are so bright — emitting more light in a few seconds than the Sun will over its entire lifetime — that they can be seen for tremendous distances. In fact, they can be detected from clear across the Universe, which is where GRB 090429B comes in.

It was first seen on April 29, 2009 (hence the name 090429B — it was actually the second GRB seen that day) by Swift, NASA’s satellite specifically designed to detect GRBs and rapidly transmit their locations to telescopes on the ground. GRBs fade very quickly, in minutes or even seconds, so rapid response is critical. In this case, observations by ground-based telescopes quickly revealed this was an unusual burst. Within hours astronomers began to suspect it was vastly distant. Estimates started putting it at greater than 13 billion light years away, almost as far as an object can be in the distant Universe.

Far, far away

Frustratingly, clouds prevented the monster Gemini 8-meter telescope from getting a spectrum of the burst, which would have nailed down its distance. Without that, the distance can only be estimated. However, several factors indicate it really is at this extreme distance:

(more…)

The Carina nebula is a sprawling, monstrous complex of gas located a mere 7500 light years from Earth. Hundreds of light years across, it’s massive enough to create thousands of stars like the Sun. Tens of thousands.

And churn out stars it does. Embedded in the nebula are several clusters of newborn stars, and many of these stars are so massive they’re nearly at the limit of how big a star can be without tearing itself apart. Stars that big explode as supernovae, and a new mosaic by the orbiting Chandra X-ray Observatory indicate they’ve been popping off in the nebula for quite some time:

[Click to enchandrasekharlimitenate.]

This image is pretty amazing: it’s a mosaic of 22 separate images by Chandra, covering 1.4 square degrees (seven times the area of the full Moon on the sky), and represents an exposure time of 1.2 million seconds! Since it shows X-rays coming from astronomical objects, it’s false color: red is from lower energy X-rays, green is medium energy, and blue from the highest energy photons.

The diffuse glow is from two sources: the stellar winds from those massive stars slamming into surrounding ambient gas at high speed, and from the shock waves generated when supernovae explode. Both are extremely high-energy events, and produce copious amounts of X-rays. That long, horizontal arc is probably the edge of a bubble, a shell of gas piled up from the winds of stars and supernovae like snow piled up in front of a snowplow.

That’s evidence right there that Carina has been cranking out supernovae over the past few million years. Interestingly, it’s what’s missing that provides more proof. (more…)