HOT HOT HEAT

An astronomer who’s seen 14 eclipses is ready for her biggest eclipse chase yet

Shadia Habbal has been chasing solar eclipses with telescopes for more than two decades. Habbal, an astronomer with the University of Hawaii, has set up equipment everywhere from India to the icy barrens of Svalbard, Norway over the last 22 years. All this globetrotting has one goal: to stand in shadow for a few brief minutes of totality when the moon passes in front of the sun, revealing the ultra-hot aura of plasma that surrounds our star like a fiery halo.

This aura is the sun’s corona, and it is millions of degrees hotter than the surface of the sun, but no one knows how that temperature difference is possible. Current scientific models about heating mechanisms and energy transfer can’t explain it. It’s not radiation, and it’s not convection. It’s a mystery of physics.

On Aug. 21, Habbal will launch her biggest eclipse mission yet: In a NASA-backed project, her team will image the 2017 North American eclipse from five different locations in the US, all about 600 miles apart, along the path of totality. The data they gather will, she hopes, bring science closer to figuring out how the corona gets so darn hot.

We spoke with Habbal from Hawaii about eclipse hits and misses, and what keeps her going.

Shadia Habbal solar corona 1
An image of the sun’s corona during the total solar eclipse of August 1, 2008. (Miloslav Druckmuller)

Quartz: What was your first eclipse?

Shadia Habbal: The first one was in India, in 1995. I had thought about doing eclipse observations a year before, and I’d submitted a proposal to NASA and I got the money. There were just six of us going there. I had been doing lots of research on the corona before then.

It was the best I’ve seen, because of the beauty of the corona. You just had the feeling the rays were expanding to infinity. I don’t know if it was the timing, or what, but it’s never been like that since.

How many eclipses have you seen?

I’ve been to 14 and I’ve missed five. We missed them all due to weather.

Oh wow, I hadn’t thought of the possibility of missing one. What is that like?

It’s terrible! It’s heartbreaking. And sometimes the weather is perfectly clear and then you get a cloud form right in front of the sun. It can happen within 30 minutes. But the payoff when you do get them is incredible. It’s worth it.

Shadia Habbal and her team in Svalbard, Norway, shortly after the total eclipse of March 20, 2015
Shadia Habbal and her team in Svalbard, Norway, shortly after the total eclipse of March 20, 2015 (courtesy Shadia Habbal)

Why is the eclipse such a good time to study the sun?

Let’s say you want to see the corona. You have to block the solar disc to see it. The best blocker is really the moon. Even the best filter covers part of the sun—and it doesn’t dim the background sky like the moon does, because the intensity of the corona is similar to the intensity of the full moon.

Even if you go to space, you have these blockers [Editor’s note: Space telescopes for solar research can sport shields that aim to blot out the sphere of the sun, with the purpose of making the corona visible. But because extremely precise blocking is so difficult, they often obscure more than just the sphere. Parts of the corona, or corona “emissions,” closest to the sun’s surface may be blocked too], but then they lose the inner part of the corona, and that’s so critical. And we’re just talking about visible light. If you go to the extreme ultra violet, then the intensity of that emission cuts off very quickly near the sun.

With an eclipse, you see everything. And that’s so critical to learning how the magnetic structure formed.

What will this eclipse be like for you?

We’ll have five observing sites along the path, and five or six people at each site. It’s the most ambitious one I’ve ever done. It’s pretty demanding, as far as working out all the details.

All that preparation for a few minutes of observing time. I imagine it’s a lot of pressure.

Before we used to have to do everything manually [operating cameras and telescopes] so we couldn’t enjoy looking up at the sun. But [now] you’re still worried—are the cameras running, are the laptops recording? There’s never a moment of relaxation.

How much do expeditions like these cost?

I underestimated how much it’s going to cost. Usually an [eclipse] expedition is about $250,000—this year I only got $175,000, and it’s a much bigger project. The funding size is disappointingly low.

Image of the total solar eclipse of August 1, 2008, with different ions of the element iron show in different colors.
Image of the total solar eclipse of August 1, 2008, with different ions of the element iron show in different colors. (Miloslav Druckmuller and Shadia Habbal)

What do you hope to get from this eclipse?

Each eclipse gives us something new. In the past we had just one spectrometer [a device that divides and measures light into its various spectra], at one site—now we’ll have four at four sites. This way we’ll be maximizing the data. If we get data from more than one site we can look for very small changes in the corona. We’re trying to observe with a new filter. It’ll image the argon element that has been stripped of nine electrons. [Editor’s note: Different elements lose different numbers of electrons at different temperatures. This is called ionization. Scientists can measure temperature by looking at the presence and distribution of different ionized elements.] We hope with the spectrometers to take a very large span of data.

We have found that when [we observe the corona through] different filters, we get temperature maps of the corona. It gives you an idea of the distribution [of heating], but we still don’t know the mechanism.

If there is enough here it will tell us something about a concentration of an element that we haven’t seen before.

So this eclipse might reveal something.

This is what keeps us going. The anticipation of new discoveries.

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