Is a bicycle like a motorcycle? Of course, the answer is it is and it isn’t. Saying something is “like” something else presupposes a lot of hidden assumptions. In the category “things with two wheels,” we have a winner. In the category “things that require gasoline,” not so much. We’ve noticed before that news stories about astronomy often talk about “sun-like stars” or “Earth-like planets.” But what does that really mean? [Paul Gilster] had the same questions, if you want to read his opinion about it.

[Paul] mentions that even textbooks can’t agree. He found one that said that Centauri A was “sun-like” while Centauri B was sometimes considered sun-like and other times not. So while Paul was looking at the examples of press releases and trying to make sense of it all, we thought we’d just ask you. What makes a star like our sun? What makes a planet like our planet?

Part of the problem is we don’t really know as much as we would like about other planets and their stars. We know more than we used to, of course. Still, it would be like wondering if the motorcycle was like that distant point of light. Maybe.

This is one of those things that seems deceptively simple until you start thinking about it. Is a planet Earth-like if it is full of water? What if it is totally covered in water? What if there’s no life at all? But life isn’t it, either. Methane-breathing silicon-based life probably doesn’t live on Earth-like planets.

Maybe Justice Potter Stewart was on to something when he said, “I know it when I see it!” Unfortunately, that’s not very scientific.

So what do you think? What’s a sun-like star? What’s an Earth-like planet? Discuss in the comments.

Don’t even get us started on super-earths, whatever they are. We are learning more about our neighbors every day, though.

While we’re still waiting for ET to give us a ring, many worlds might not have life that’s discovered the joys of radio yet. Scientists ran a two-pronged study to see how bacteria might fare on other worlds.

We currently define the Habitable Zone (HZ) of a planet by the likelihood that particular planet can host liquid water due to its peculiar blend of atmosphere and distance from its star. While this doesn’t guarantee the presence of life, its a good first place to start. Trying to expand on this, the scientists used a climate model to refine the boundaries of the HZ for atmosphere’s dominated by H₂ and CO₂ gases.

Once they determined these limits, they then mixed up some example atmospheres and subjected E. coli to the environments. Their findings “indicate that atmospheric composition significantly affects bacterial growth patterns, highlighting the importance of considering diverse atmospheres in evaluating exoplanet habitability and advancing the search for life beyond Earth.”

If you want to look more into what might be out there, how about analyzing the WOW Signal or looking at what the Drake Equation is all about.

Ever been at a party and landed in a heated argument about exactly where the International Space Station (ISS) is passing over at that very instant? Me neither, but it’s probably happened to someone. Assuming you were in that situation, and lacked access to your smartphone or any other form of internet connected device, you might like the pocket-sized Screen Tracker from [mars91].

The concept is simple. It’s a keychain-sized item that combines an ESP32, a Neopixel LED, and a small LCD screen on a compact PCB with a couple of buttons. It’s programmed to communicate over the ESP32’s WiFi connection to query a small custom website running on AWS. That website processes orbit data for the ISS and the positions of the planets, so they can be displayed on the LCD screen above a map of the Earth. We’re not sure what font it uses, but it looks pretty cool—like something out of a 90s sci-fi movie.

It’s a great little curio, and these sort of projects can have great educational value to boot. Creating something like this will teach you about basic orbits, as well as how to work with screens and APIs and getting embedded devices online. It may sound trivial when you’ve done it before, but you can learn all kinds of skills pursuing builds like these.