Mike Brown is an astronomer, specifically one who studies Kuiper Belt Objects, those giant frozen iceballs that haunt the solar system out past Neptune.

In fact, Neptune’s biggest moon Triton has a lot of characteristics similar KBOs — it may be one captured by Neptune — so observing it gives an interesting opportunity for a compare-and-contrast study. So this past weekend Mike was using the Keck telescope in Hawaii to observe Triton along with its (adoptive?) parent planet, and took this fantastic image of the pair:

[Click to poseidenate.]

This false-color image shows the two worlds in the infrared, specifically at a wavelength of about 1.5 microns, twice what the human eye can see. Methane strongly absorbs this color of light, so where Neptune (in the upper left) looks dark you’re seeing lots of methane clouds, and where it’s bright there are clouds higher up, above the methane. Triton is in the lower right, and is bright because it’s covered in ice which is highly reflective.

Now this is all very pretty and interesting and sciencey, but if you know me at all you know there’s more to this story.

Mike tweeted about the image, and I oohed and ahhhed at it, of course. But then he tweeted again, saying he was also observing Jupiter’s moon Europa, but it was too bright to get good images using the monster 10-meter Keck telescope. It "saturated the detector" which is astronomer-speak for "overexposed".

That’s funny, I thought. Neptune looks fine in the image, and the random noisy grain in it makes it clear Mike wasn’t anywhere near saturating the image. Now I know Europa is closer to the Earth, so it should look brighter, but geez, it’s a moon, and a lot smaller than Neptune. How could it be too bright to image?

It turns out my all–too–human and all–too–miserable sense of scale has failed me again. Math to the rescue!

(more…)

[UPDATE: The article discussed below is now online at Discover Magazine's website, so you can read it there.]

Every now and again I delve back into the ancient art of writing for an actual magazine that has words printed in ink on paper which gets sent to you via the postal service.

Quaint, I know.

But I wrote just such an article for Discover Magazine which is in the December 2010 issue. The article, called "Why Size Matters" is about why defining the word planet is proving to be so difficult.

Funny how writing works sometimes. I got the idea for the article while researching a blog post on a moon in the outer solar system. Curious about its size, I started poking around the web looking for other moon diameters, and then started wondering how big an object you need before gravity crushes it into a ball. I thought I could write the article about just that, but the words apparently had a mind of their own and went in a different direction. I wound up talking about what we think of as planets, and then in the middle of all this I read an advance copy of Mike Brown’s wonderful book How I Killed Pluto and Why It Had It Coming (full review coming soon). Mike spends quite a bit of time on this very topic, as you might imagine (he discovered the Kuiper Belt object Eris, which kick-started the demotion of Pluto). I found his thinking to be very similar to mine, and his writing actually gelled a lot of disorganized thoughts I had about all this.

Anyway, the article was fun to write, and I think anyone who likes my blog will like it. I got the issue in the mail the other day, and it’s on newsstands and at bookstores now. I hope you’ll check it out.

Mike Brown is an astronomer, and in my opinion is mainly responsible for kick-starting the demotion of Pluto as a planet — he and his team found Eris, an object in the outer solar system that was apparently bigger than Pluto. It was this discovery which set in motion the events that led to the foofooraw about Pluto, and the vote that turned it (and Eris and many others) into "dwarf planets".

Mike continues to observe Eris and other dwarf planets (as well as search for new ones). These objects are small and far away — did you know our own Moon is substantially larger than Pluto? — and therefore hard to analyze. Even with huge telescopes, these objects are hardly more than dots.

However, a fortuitous event landed in the laps of astronomers recently: Eris passed directly in front of a faint star. To us on the ground, it appeared as if the star winked out as the dwarf planet passed in front of it. By carefully timing the duration of this mini-eclipse, the size of Eris could be estimated.

And, to everyone’s shock, Eris looks to be roughly the same size as Pluto. Mike describes all this on his blog.

What does this mean for Pluto? (more…)

Mike Brown, who goes by the name plutokiller on Twitter — for good reason — has written a lengthy but interesting post about Saturn’s moon Titan. Why do I like it? Because it involves people, and the people are important to the story. I could write about clouds on Titan here on the BABlog, but I don’t know the people involved. Mike does, and that’s why his post is fun to read.

Gemini/AURA/Henry Roe – Lowell Observatory/Emily Schaller – IfA-University of Hawaii