What does one do when frustrated at the lack of affordable, open source portable trackers? If you’re [OG-star-tech], you design your own and give it modular features that rival commercial offerings while you’re at it.

What’s a star tracker? It’s a method of determining position based on visible stars, but when it comes to astrophotography the term refers to a sort of hardware-assisted camera holder that helps one capture stable long-exposure images. This is done by moving the camera in such a way as to cancel out the effects of the Earth’s rotation. The result is long-exposure photographs without the stars smearing themselves across the image.

Interested? Learn more about the design by casting an eye over the bill of materials at the GitHub repository, browsing the 3D-printable parts, and maybe check out the assembly guide. If you like what you see, [OG-star-tech] says you should be able to build your own very affordably if you don’t mind 3D printing parts in ASA or ABS. Prefer to buy a kit or an assembled unit? [OG-star-tech] offers them for sale.

Frustration with commercial offerings (or lack thereof) is a powerful motive to design something or contribute to an existing project, and if it leads to more people enjoying taking photos of the night sky and all the wonderful things in it, so much the better.

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.

Logically we understand that the other planets in the solar system, as well as humanity’s contributions to the cosmos such as the Hubble Space Telescope and the International Space Station, are zipping around us somewhere — but it can be difficult to conceptualize. Is Jupiter directly above your desk? Is the ISS currently underneath you?

If you’ve ever found yourself wondering such things, you might want to look into making something like Space Monitor. Designed by [Kevin Assen], this little gadget is able to literally point out the locations of objects in space. Currently it’s limited to the ISS and Mars, but adding new objects to track is just a matter of loading in the appropriate orbital data.

In addition to slewing around its 3D printed indicator, the Space Monitor also features a round LCD that displays the object currently being tracked, as well as the weather. Reading through the list of features and capabilities of the ESP32-powered device, we get the impression that [Kevin] is using it as a sort of development platform for various concepts. Features like remote firmware updates and the ability to point smartphones to the device’s configuration page via on-screen QR aren’t necessarily needed on a personal-use device, but its great practice for when you do eventually send one of your creations out into the scary world beyond your workbench.

If you’re interested in something a bit more elaborate, check out this impressive multi-level satellite tracker we covered back in 2018.

On February 13th of 2023, ARCA of the kilometre cubic neutrino telescope (KM3NeT) detected a neutrino with an estimated energy of about 220 PeV. This event, called KM3-230213A, is the most energetic neutrino ever observed. Although extremely abundant in the universe, neutrinos only weakly interact with matter and thus capturing such an event requires very large detectors. Details on this event were published in Nature.

Much like other types of telescopes, KM3NeT uses neutrinos to infer information about remote objects and events in the Universe, ranging from our Sun to other solar systems and galaxies. Due to the weak interaction of neutrinos they cannot be observed like photons, but only indirectly via e.g. photomultipliers that detect the blue-ish light of Cherenkov radiation when the neutrino interacts with a dense medium, such as the deep sea water in the case of ARCA (Astroparticle Research with Cosmics in the Abyss). This particular detector is located at a depth of 3,450 meters off the coast of Sicily with 700 meter tall detection units (DUs) placed 100 meters apart which consist out of many individual spheres filled with detectors and supporting equipment.

With just one of these high-power neutrinos detected it’s hard to say exactly where or what it originated from, but with each additional capture we’ll get a clearer picture. For a fairly new neutrino telescope project it’s also a promising start especially since the project as a whole is still under construction, with additional detectors being installed off the coasts of France and Greece.

In all likelihood, asteroid 2024 YR4 will slip silently past the Earth. Based on the data we have so far, there’s an estimated chance of only 2.1% to 2.3% that it will collide with the planet on December 22nd, 2032. Under normal circumstances, if somebody told you there was a roughly 98% chance of something not happening, you probably wouldn’t give it a second thought. There’s certainly a case to be made that you should feel that way in regards to this particular event — frankly, it’s a lot more likely that some other terrible thing is going to happen to you in the next eight years than it is an asteroid is going to ruin your Christmas party.

That being said, when you consider the scale of the cosmos, a 2+% chance of getting hit is enough to raise some eyebrows. After all, it’s the highest likelihood of an asteroid impact that we’re currently aware of. It’s also troubling that the number has only gone up as further observations of 2024 YR4’s orbit have been made; a few weeks ago, the impact probability was just 1%. Accordingly, NASA has recently announced they’ll be making time in the James Webb Space Telescope’s busy scientific schedule to observe the asteroid next month.

So keeping in mind that we’re still talking about an event that’s statistically unlikely to actually occur, let’s take a look at what we know about 2024 YR4, and how further study and analysis can give us a better idea of what kind of threat we’re dealing with.

An Unexpected Visitor

Officially, 2024 YR4 was discovered on December 27th, 2024 by the Asteroid Terrestrial-impact Last Alert System (ATLAS), but by that time we had already dodged a potential impact. It turns out that the asteroid had come within 828,800 kilometers (515,000 miles), or around two times the distance from the Earth to the Moon, on December 25th without anyone realizing.

All of the observations of the asteroid made since its discovery have therefore been made while the object is moving away from the planet and back into deep space. This is a less than ideal situation when you consider that the asteroid is estimated to be between 40 to 90 meters (130 to 300 ft) in diameter.

With each passing day, it becomes more difficult to track and resolve 2024 YR4, and it’s currently estimated that observing it with ground-based telescopes will no longer be possible beyond April.

That is, until 2028. As you might have put together by now, 2024 YR4 is in such an orbit that it comes within close proximity of Earth every four years. If current orbital projections hold true, during the summer of 2028, the asteroid will be close enough again that we can observe it on the way towards us.

That will include a fly-by of Earth in early December before it swings back out of range. Hopefully by that time we’ll have collected enough data to know whether or not we’ll need to brace for impact the next time it swings by our neighborhood.

Deflect, or Evacuate?

As far as potentially dangerous Near Earth Objects (NEOs) go, 2024 YR4 is about as ideal as they get. While it did sneak up on us in 2024, now we know it’s on a fairly predictable schedule and there’s enough time that we could actually do something about it if the chance of impact gets high enough to take it more seriously. In 2028, we’ve even got a chance to deflect it as it zooms past Earth.

That would have been science fiction a few years ago, but after NASA’s successful DART demonstration mission, we now know it’s possible to significantly alter the orbit of an asteroid simply by ramming a spacecraft into it at high velocity. The target asteroid in that test was much larger than 2024 YR4, with a diameter of 177 meters (581 ft). Yet the head-on impact of the 500 kg (1,100 lb) DART spacecraft was able to slow it down enough to make a noticeable change in its orbit.

Given how close 2024 YR4 would be passing by Earth, it’s not hard to imagine that a spacecraft with several times the mass of DART could be put on a collision course with the asteroid in 2028. Even if such an impact would not be enough to entirely prevent a collision with 2024 YR4, if applied carefully, it could certainly be sufficient to move the calculated point of impact.

But would such a mission even be necessary? Current estimates put around half of the potential impact points for 2024 YR4 over the ocean. Even where the path of the asteroid does cross over land, most of it is sparsely populated. The biggest risks to human life would be in Nigeria and India, but the chances of a direct hit over either area is particularly remote, especially given the estimated blast radius of 50 km (31 miles).

Unless updated orbital data for 2024 YR4 indicates that it’s going to directly impact one of these densely populated areas, the most cost effective approach may be to simply move as many people out of the impact area as possible. While an evacuation of this scale would still be a monumental task, we’d at least have several years to implement the plan.

Bringing Out the Big Guns

While the chances are still excellent that 2024 YR4 will zip harmlessly past our Blue Marble in 2032, it’s not outside the realm of possibility that some big decisions might need to be made in the next few years. So how do we figure out how large of a threat this asteroid really is before it’s too late?

That’s where advanced space-bound observatories like the James Webb Space Telescope (JWST) come in. While our instruments on Earth soon won’t be able to see 2024 YR4, the JWST will not only be able to keep its gaze on the asteroid for longer, but the infrared observatory is uniquely suited for capturing critical data about its size and shape.

Up to this point, the size of 2024 YR4 has been estimated based on its visible appearance, but that can be misleading. It could be that only part of the asteroid is reflective, which would give the impression that its smaller than it actually is. But the JWST doesn’t rely on visible light, and instead can use its IR instruments to detect the heat being given off by the asteroid’s rocky surface.

With definitive data about the asteroid’s size, shape, and rotation, astronomers will be able to better model how 2024 YR4 is moving through space. That’s going to be key to figuring out whether or not that 2.3% chance of impact is going to go up or down — and if it does go up, will help narrow down exactly where the asteroid is likely to hit.

Did you ever hear of a satellite called Parcae (pronounced like park-eye)? If you haven’t, don’t feel bad—it was, after all, a top-secret project only revealed in July 2023. [Ivan Amato] not only heard about it, but also wrote a fascinating peek into the cloak-and-dagger world of cold-war spy satellites for this month’s IEEE Spectrum.

According to [Ivan], the satellite helped the United States to keep track of Russian submarines and was arguably the most capable orbiting spy platform ever. Or, at least, that we get to hear about.

Given that it was built in the 1970s, it was amazing that the satellite wasn’t very large. The craft itself seemed small compared to its solar panels. Even today, the satellite remains a bit of a mystery. While the NRO—the US spy satellite agency—did acknowledge its existence in 2023, there is very little official information about it, although, apparently, other curious people have unearthed data on Parcae over the years. According to the NRO, the satellites have not been in use since 2008.

The Parcae—named after the Romans’ three fates—worked in groups of three and launched in a “dispenser” that carried the trio of spaceships. They could listen to radio emissions from ships and use very accurate clocks to pinpoint their location based on the slight differences in the time each satellite heard the signal.

One of the system’s unique features was that thanks to a minicomputer, ship positions could be in users’ hands in minutes. That doesn’t sound so impressive today, but it was an amazing achievement for that time.

The article goes into more detail about how the individual satellites used a gravity boom for orientation and a lot of details about the designers. Of course, some of what Parcae could do is still secret for now, so there may be more to this story later.

Spy satellites can’t always hide from backyard telescopes. Spy satellites always have impressive technology and—presumably—big budgets.