Catching a Star’s Helium Flash

Old stellar flashers will be caught in the act in the not-so-distant future, whether they like it or not.

[Smithsonian]

While we have a pretty good idea about how stars like our Sun work, observing all the details that unfold over millions to billions of years of stellar evolution can be difficult, especially if the phenomena occur over short timescales. Take, for example, a particularly explosive and relatively short-lived period our Sun is expected to experience in roughly five billion years.

This event is predicted to happen after our nearest star has burned up all of its hydrogen fuel and starts to burn helium. This is the beginning of the end; the Sun will swell into a vast red giant, ejecting its upper layers of plasma into space via violent solar winds, brightening 1,000 times than it is today. Needless to say, this will be a terribly dramatic time for our solar system (and a definitive apocalypse for anything that remains of our planet’s biosphere), but it will be on the verge of something even more dramatic: a helium flash.

As the solar core starts using helium as fuel, the fusion process will generate carbon and as this begins, a powerful eruption of energy will detonate, as detailed by a UC Santa Barbara statement:

A star like the sun is powered by fusing hydrogen into helium at temperatures around 15 million K. Helium, however, requires a much higher temperature than hydrogen, around 100 million K, to begin fusing into carbon, so it simply accumulates in the core while a shell of hydrogen continues to burn around it. All the while, the star expands to a size comparable to the Earth’s orbit. Eventually, the star’s core reaches the perfect conditions, triggering a violent ignition of the helium: the helium core flash. The core undergoes several flashes over the next 2 million years, and then settles into a more static state where it proceeds to burn all of the helium in the core to carbon and oxygen over the course of around 100 million years.

While the helium flashes of old Sun-like stars have been predicted for 50 years, we have yet to actually observe any kicking off in our galaxy, which isn’t so surprising considering it’s only comparatively recently that we’ve developed the techniques that are capable of precisely measuring the brightness fluctuations of distant stars. This might be about to change, according to a new study published in Nature Astronomy Letters.

“The availability of very sensitive measurements from space has made it possible to observe subtle oscillations in the brightness of a very large number of stars,” said coauthor Jørgen Christensen-Dalsgaard, of the UC Santa Barbara’s Kavli Institute for Theoretical Physics (KITP).

Christensen-Dalsgaard is referring to the growing number of space-based observatories, primed to survey the sky for transiting exoplanets—such as Kepler, CoRoT and TESS—that have extremely sensitive photonics that can detect the slightest changes in stellar brightness. And by virtue of these missions’ wide field of view, taking in the light from many stars at once, the helium flashes and resulting brightness oscillations across the stars’ surfaces could be detected in the near future.

It’s thought that the flash itself should last for no more than two million years, which may sound like a long time to we puny humans, but over cosmic timescales, that’s literally a flash—we need some serious luck to detect them. But with more observatories, longer observation periods, and wider fields of view, luck may be just around the corner.

Solar Email Rage, I Got Some

burning_envelope

I’m no stranger to abusive emails, but I thought I’d share a run-in I had with a particularly angry reader during the week.

Now, why would I be receiving hate mail? You might think it has something to do with my campaign of 2012 smack-downs last year… perhaps it’s an angry author of a doomsday book? Or a prominent religious figure with an axe to grind? Perhaps it’s the guys who think the LHC is going to put a continental-sized divot into Europe?

No, no and nope (although the last one would have been fun, I haven’t heard from them for ages; it’s as if I’ve lost touch with an old friend).

Actually, this particular example of email rage came from a very rare subset of Internet critic, the determined-and-possibly-half-way-intelligent-troll. Not content with flinging abuse around in blog comment boxes, this type of individual will read something, and then come hell or high water, they will hunt the author down to give them a piece of their mind.

The reason why I think this guy is possibly-half-way-intelligent is because he can spell. And he doesn’t spout his alternative theory or type in all-caps. Plus, he uses few exclamation marks. His message was short, sweet and left me in no doubt of what he thought about me:

Subject: The sun is BORING!?

Next time you write about the sun, can you try not to sound like a 15 year old? And thanks for educating me on global warming, I’m sure the sun has a negligible effect on the Earth’s climate…

Actually, next time you write about the sun, DON’T.

–Aaron

Now Aaron, tell me how you really feel.

I hold my hands up in defence. Yes, I did say the Sun was being boring, but that’s not quite the same as me saying, “the Sun is boring!” now is it. I’m not going to throw down the ‘but I’m a solar physicist and I actually have a clue card’… oh, I think I just did.

Although I usually assign these kinds of messages to the trash (when I was in my 2012 prime, I was getting up to 10 of these types of email a day, only with f-bombs, and “!!!!!!1“s), I found this one curious.

It was obviously relating to the op-ed article I did for the Discovery Space Wide Angle this week, but this guy had to do his research to find Astroengine.com and consequently use my email form. Is this a new mainstream breed of critic that I haven’t been exposed to before? Do people really have this much time on their hands?

So my conclusion is, I don’t think he liked my opinion about global warming, or he really does think I write like a 15 year old. Well, it takes one to know one. When you grow up to be a 16 year old Aaron, read my articles again will you? And yes, I do forgive you, it’s okay, consider this strike one.

Introducing Little SDO

The Solar Dynamics Observatory (NASA)

Playing on our love for WALL-E, our amazement for the Pixar Lamp and some great animation, Chris Smith, an employee at NASA Goddard Flight Center, has given the upcoming Solar Dynamics Observatory a personality.

Apart from obviously having too much time on his hands, Smith is a very talented guy (as all NASA employees are) and is showing that, once again, the space agency is doing a fantastic job of reaching out to the public.

As proven by the efforts of the Phoenix Mars Lander team in 2008, communication goes a long way and by harnessing social media, NASA can make its missions household names. Phoenix was tweeting, blogging and podcasting to its hearts content for five months, from touchdown to frozen death; it was Big Brother for robots living on Mars.

Now most NASA missions have Twitter feeds and devoted blogs, ensuring everyone’s interest is piqued. It also helps to have a Twitter feed talking in first-person, giving these brave rovers, landers, orbiters and probes a much needed personality.

So now, Chris Smith has done something very cool with the SDO; he’s given it an animated personality in a short animation reminiscent of a movie teaser for an upcoming Disney-Pixar feature film. Behold, the Little SDO:

It’s a really fun little piece,” says Wade Sisler, a television producer for NASA. “And we’re hoping to use it as a way of waking some kids and folks up to solar science.”

And so NASA should, I like it! It’s going to get people interested in a comparatively small mission, and let’s face it, the satellite lacks character (the boxy 4-eyed robot doesn’t do much for me). However, now that Smith has added squeaky solar panel wings, and blinking “eyes” (without changing the design of the craft at all), he’s boosted the SDO’s likeability. Suddenly I care for the little guy. I hope he doesn’t get hit by a solar flare.

Due for launch in October, the SDO will be inserted into a geosynchronous orbit above New Mexico, gathering data from the Sun, so solar physicists can better understand space weather. The cool thing is that with those four eyes, the SDO will capture high-definition images of the Sun continuously.

It might not have the dazzle of the Phoenix Mars Lander, but it has a personality and people will love him (I await the Twitter feed).

Learn more about the Solar Dynamics Observatory »

Source: Wired Science