BAN #440: Targeting an asteroid, Loop de loupe

[Hubble image of NGC 3603. Credit: NASA, ESA, R. O'Connell (UVa), F. Paresce (NIA, Bologna, Italy), E. Young (USRA/Ames Research Center), the WFC3 Science Oversight Committee, and the Hubble Heritage Team (STScI/AURA)]

Pic o’ the Letter

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

In June 2018, The Japanese Space Agency (JAXA) spacecraft Hayabusa2 arrived at the asteroid Ryugu, a 900-meter-wide rubble pile that orbits the Sun on a mildly elliptical path that takes it from just inside Earth’s orbit to just inside that of Mars. It’s a Potentially Hazardous Asteroid, meaning it’s big enough and gets close enough to Earth that should its orbit change (due to the influence of the gravity of the planets) it would do significant damage to us.

That won’t happen for a long time, if ever, but its orbit does make it relatively easy to send a probe there. Hayabusa2 mapped the asteroid’s surface, did a mineralogical survey, and even dropped down twice to get samples of the asteroid to return to Earth.

Another experiment it did was to measure the mass of the asteroid. It carried five highly reflective roughly spherical beanbag-like devices called target markers. They’re used for navigation: The spacecraft drops them where it needs to land, then uses a bright lamp to illuminate them so that its autonomous navigation can see where they are.

Three of them were to be used to get samples, but two were used to do a gravity experiment. They were dropped from a height of a kilometer and allowed to fall toward Ryugu; the incredibly weak gravity took several days to pull them down.

When one of them was deployed the spacecraft backed off at about 10 centimeters per second, and started snapping images Ryugu and the target marker. JAXA created a composite image, adding together all the frames as the spacecraft moved away, creating this lovely shot:

[Composite image of the target marker and Ryugu as Hayabusa2 backed away. Credit: JAXA, Chiba Institute of Technology, and collaborators]

Whoa. Very cool. It looks like something out of Star Trek, so of course I love it.

Incidentally the mission was a huge success. It got samples from the surface and below the surface, and returned them to Earth in December 2020, and have already yielded a bounty of science.

Here’s the JAXA tweet about the target marker image:

By the way, the second sample was to get material from beneath the surface. To do that it deployed a free-floating cannon! The spacecraft hid behind the asteroid when the cannon shot a 2.5-kilogram projectile at Ryugu, which excavated an 18-meter wide crater. After things settled, the spacecraft went to the crater and repeated the procedure to collect a sample, dropping down, firing a bullet, and collecting the debris.

You may enjoy this video of that process. Because wow!

Since today is Asteroid Day, I figured this is all appropriate. Enjoy!

Life Hacks

Not what you might expect from an astronomer, but in my defense I am alive

My mom was a jeweler, who started in sales at a local store and worked her way up to store manager over the years. I have strong memories of visiting her at the store sometimes when I was a kid — mostly though of my dad giving me a quarter so I could go over to the Sears down the block and get a small bag of Swedish fish or roasted Spanish peanuts. For the record, I still love both.

But when I think of my mom at the store I think of her standing behind the glass showcase counter, a customer on the other side, and her peering closely at a ring or some other doodad with a jeweler’s loupe screwed into her eye.

A loupe at its simplest is a single-lens magnifier, usually with pretty low magnification and a very short focal length, meaning you have to bring something up to it very close to get it in focus. Also in general the lens in a jeweler’s loupe is mounted on the narrow end of a truncated cone, with the wider end designed to fit in your eye socket, so when you scrunch up your face a bit it stays in, allowing hands-free use so you can hold on to whatever it is you’re looking at, plus a tool of some kind.

[My mom’s loupe, somewhat worse for wear due to decades of use, with her initials written on it in faded ink from when she worked at the jewelry store. Credit: Phil Plait]

I’ve had my mom’s old plastic loupe for so long I don’t remember when I got it from her. I vaguely remember asking her if I could have it when she retired from the store, so it’s been in my possession for probably 30 years.

Here’s the thing though: It’s immensely useful. I don’t think a week goes by without me needing it for one thing or another. My wife is the tool user in the family, so she gets splinters all the time, and the loupe is critical for seeing how deep the splinter goes, where it may stick out of the skin a bit for useful grabbing, and for guiding the tweezers, too.

Colorado is dry, so it’s common to have flaky cracked fingertip skin, which is irritating. The loupe is handy for helping snag those with fingernail/cuticle clippers. I use it to look at interesting rocks and meteorites. We get gizmos with instructions written in 0.02 font that’s two tones darker than the paper or plastic it’s printed on (I’m looking at you, Apple) and magnifying it helps a huge amount.

[A piece of the Chelyabinsk asteroid that fell in Russia in 2013 that was given to me by my friend Richard Drumm, magnified via a jeweler’s loupe. The meteorite is just a hair over a centimeter long. Credit: Phil Plait]

My Google phone has pretty decent macro capabilities, especially when you zoom in, but that’s a digital zoom, literally just looking at fewer pixels in the detector, which loses resolution. The loupe allows more magnification and actually works pretty well as a macro lens.

If you want to get one — and you do — they’re much cheaper than I expected. I found them on Ebay and Amazon for under $20. I can’t vouch for the quality but still, I figured they’d be pricier. My mom’s loupe is only 3.3X (you can see that etched in it in the photo above) but I see ones that are 7X and even 10X.

When you get one it won’t have the memories of your mom like maybe mine does, but then if you keep it around long enough maybe someone else will get those memories of you. You never know what’s going to last, and outlast you. In my opinion, something useful that also is fun, even a joy, to use makes the best gift to the future.

Et alia

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