BAN #85: Crowded galaxy, Flion away

February 4, 2019 Issue #85

February 04, 2019

Subscribers are the voltage differential that engages Newton’s Third Law in me.

Pic o’ the Letter

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

One thing that bugs me when I’m watching a scifi movie or TV show is when you see a spaceship hanging in deep space between the stars, fully lit, with complex and bright astronomical objects crowding the background.

If they’re in deep space, what’s lighting the ship? And if they’re fully lit, how can we see all that stuff behind them, which is incredibly faint? And seriously all that stuff… space is mostly empty!

But then I see something like this and I think, “…oh.”

[M4 and environs, created from Digitzed Sky Survey images. Credit: Giuseppe Donatiello]

That is a spectacular vista in the constellation of Scorpius. The clutch of stars below center is M4, a globular cluster only about 7,000 light years away. That makes it the closest of its kind to us; they have orbits that take them outside the galaxy, and tend to be farther away.

M4 is on that same kind of orbit, but is currently plunging through the disk of the Milky Way, which is why this scene is so crowded: We’re looking toward the galactic center where all the action is. You can see another globular, NGC 6144, to the upper left (it’s 29,000 light years away, so we happen to see it just on the other side of the galaxy). The star to the upper right is Al Niyat, aka Sigma Scorpii, a naked eye star. Antares is a red supergiant marking the heart of Scorpius, and it’s just off frame to the left of this image.

There’s also a lot of gas floating around in this direction, including all that stuff around Al Niyat. That’s called Sharpless 2-9, and it’s hydrogen gas excited by the fierce light of AL Niyat (which is a blue giant, a massive and very luminous star). There’s also a lot of dust in the cloud, and toward the center that’s scattering the blue light from the star, so the dust appears to glow blue — that’s very similar to why the sky is blue. The nebulosity to the left is part of a huge complex of gas and dust around Antares and the star Rho Ophiuchi, off the frame to the upper right.

So scenes like this actually exist! I still don’t think most movies get it right, but still: Truth is in many ways cooler than fiction.

Link o’ the ‘letter

Just a fun link I found or someone told me about

I sometimes wonder, with a green revolution getting started, if we’ll be able to replace everything that currently uses fossil fuels with something greener. I have solar panels on my house and a cluster of batteries to power my house day and night (they’re from Tesla, and if you’re looking to get some yourself, here’s my referral code).

But what about things that use mighty amounts of power, like, say airplanes? Can we ever hope to be able to power them more cleanly?

… maybe. At least maybe some of them. Researchers at MIT have successfully tested ion thrusters on small airplane. By small, I mean model sized, but still. This is very cool.

Ion thrusters use a very strong electric field to work. There are two rows of metal panels in them. The front row strips the electrons off air molecules (ionizing them), and the back row is kept at very high negative charge, which attracts those positive ions. In between are neutral molecules, and those get slammed by the ions screaming toward the back panel. This throws the neutral molecules out the back, creating thrust. This is in very general terms how a propeller or jet engine works: grabbing air from the front and throwing it very hard out the back.

The thust generated isn’t very high, so the plane has big wings with lots of lift, and is made of very light materials. Still, it works. Here’s a video overview with footage of a short flight.

Now mind you, this is a proof of concept and there’s a long way to go. But it’s dang clever, and there’s lots of room for scaling this up. I don’t think we’ll see passenger planes using this tech (more likely battery energy density will improve enough that electric planes will become viable first), but for deliveries, drones, and the like this could be pretty useful. Of course the silent drive makes for useful military applications as well, so I wouldn’t be surprised if they get involved.

You can find a more technical overview at Nature magazine, as well as an editorial about it.

Oh, those magnificent engineers and their flion machines!

Blog Jam

What I’ve recently written on the blog, ICYMI

[From Friday’s blog post. Credit: NASA, ESA, L. Bedin (Astronomical Observatory of Padua, Italy), and Digitized Sky Survey 2]

Monday Jan. 28, 2019: How long is a day on Saturn?

Tuesday Jan. 29, 2019: The year in Mars

Et alia

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