Mars Sample Non-return, Betelgeuse in the infrared

November 6, 2023   Issue #639

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SciAm What SciAm

Stuff I’ve written for Scientific American

Right now, NASA is in some hot water when it comes to Mars. The Perseverance rover is collecting samples of Mars and sealing them up so a future mission, called Mars Sample Return, can come get them and bring them to Earth. But the retrieval mission is more complex than originally proposed, and the costs are running pretty high. NASA had to scrap the whole thing and start all over again.

I wrote an OpEd about this for Scientific American that was just published a few days ago. Please give it a read! This article took a lot more effort than usual for me; there’s a stiff political aspect to it that is somewhat complex, and boiling it down to a paragraph or two was hard. Support for NASA politically is a weird mix of politicians loving what the space agency does, but then always going after it for costing too much. Thing is, it sounds like a lot (two billion for a rover? What?) but in reality that kind of money is peanuts compared to what we spend on utter garbage. Politicians can always seem to find a hundred billion lying around to fund their pet partisan pork barrel, but when it comes to stuff that actually can make humanity better, they whine about deficits and austerity.

It’s always BS when they say that. Always. Republicans complain about spending, then give their richest donors a two trillion dollar tax cut, as but one example. The US has plenty of money. We just waste a lot of it. We could easily house our homeless, feed our hungry, educate our children, and, yes, explore the universe like we never have before.

We — in the form of our representative government — just choose not to.

Some states have elections coming over the next few weeks, and again next year. Choose wisely.

Pic o’ the Letter

A cool or lovely or mind-bending astronomical image/video with a description so you can grok it

Oh, how I remember going outside at night in the winter of 2019/2020 to look at Orion, and see with my own eyes how faint Betelgeuse was. The Great Dimming, as it’s been nicknamed, made a lot of headlines, especially since a lot of people thought (erroneously) that it could mean Big B was about to go supernova (in reality it probably won’t for many tens of thousands of years).

But the star did fade, a lot, dropping down to half its usual brightness for many months before brightening again. Astronomers argued back and forth over what caused the dimming, though it became more and more clear (to make a pun) that the root cause was dust.

Betelgeuse is a red supergiant, a massive star near the end of its life, and these are known to be unstable. Huge pressure pulses generated deep inside the star work their way outward, creating immense shock waves that blast away material from the outer layers into space. A lot of this material is carbon and silicon, which condenses as it cools to form grains of cosmic dust. This material is fairly opaque, which is what causesdBetelgeuse to dim.

Using an infrared spectrometer called MATISSE on the Very Large Telescope Interferometer, astronomers made observations that support the idea of the star violently expelling prodigious quantities of dust (link to journal paper):

The top row shows infrared images from 2018, early 2020, and late 2020 from before, during, and after the dimming — note the size of Earth’s orbit in the upper left panel to get an idea of just how ridiculously huge the star is.

Remember, these are not in visible light! That’s important: Dust is opaque to the kind of light we see, so the star dimmed in 2019. But the dust is warm, and glows in the infrared, so in those wavelengths the star actually got brighter. The early 2020 image, taken during the dimming, shows that it was brighter.

The bottom row shows images taken with a filter that lets through the light of silicon monoxide, or SO, one ingredient that can make dust. You can see that where there’s more of the SO in a bottom row pic, the star is also brighter overall in infrared in the top row pic. That means that where the SO was blowing out it could make dust, which was warm and brighter, supporting the idea that it was dust that dimmed the star.

That’s a nice scientific result, and helps us understand how these Brobdingnagian stars make dust, material that litters the galaxy everywhere.

And it also shows that, holy wow, we can get images that show details on a star’s surface! At 650 light-years or so away, Betelgeuse is tiny, but by combining the light from 4 separate 8.2-meter telescopes, we can see details that are incredibly small on the sky. That will never not amaze me.

Et alia

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