Cosmic Curiosities
“Earth is a small town with many neighborhoods in a very big universe.”
- Ronald Garan, American Astronaut
Our Stellar Neighborhood
We live in all kinds of neighborhoods, where certain people, places, and things are “just down the road.” We can call our city our neighborhood—even our state and country. Of course, all of Earth is our neighborhood, too! But let us take a bigger step, venture into the galaxy, and look at our stellar neighborhood. The sun is our closest star, and, you could say, a necessary neighbor, due to its heat and light. But what about other stars near us?
NASA’s Parker Solar Probe
This video shows the closest stars to our solar system. The yellow sun is located at the center. The horizontal plane is an expansion of the Earth’s equator circle. The transparent blue shells mark five light years from the sun, with the outermost shell being 20 light years from the sun.
The colorful dots are the 130 stars closest stars, or neighbors. Stars all work the same—by nuclear fusion—but they come in different sizes and temperatures. Blue color is hot while red is cool. Remember, though, all stars are hot!
Stellar Neighborhood Video Key
| Date | Description | Spectral Class |
|---|---|---|
| Blue | Hot and brighter | A and F |
| Yellow | Stars like the sun | G |
| Orange | Cooler than the sun | K |
| Red | Red Dwarfs | M |
| Purple | Brown Dwarfs, limited fusion | T |
| White | White Dwarfs, dead stars, no fusion | D |
On a dark, clear night, we can only see about 20 of these stars with just our eyes. Only seven of these are identifiable in most cities with night lights around. The top four are easy to spot even in big cities. One star—Alpha Centauri—is not visible in Wisconsin.
| Star | Constellation | Magnitude | Light Years |
|---|---|---|---|
| Sirius | Canis Major | -1.5 | 8.6 |
| Alpha Centauri | Centaurus (not visible in Wisconsin) | -0.3 | 4.3 |
| Procyon | Canis Minor | 0.3 | 11 |
| Altair | Aquila | 0.8 | 17 |
| Achird | Cassiopeia | 3.4 | 19 |
| Tau Ceti | Cetus | 3.5 | 12 |
| Epsilon Eridani | Eridanus | 3.7 | 10 |
All the dwarf stars—red, brown, and white--are far too faint to be seen with the naked eye.
Sirius, Procyon, and Altair are bright because, not only are they close, but they are intrinsically more luminous than the sun. Think of them as a 1,000-watt light bulb while the sun is like a 100-watt bulb.
Alpha Centauri. Achir, and Tau Ceti are close to sun with similar size and intrinsic brightness—around a 100-watt bulb. Epsilon Eridani is a K star—a bit cooler, but close--so it is fairly visible in our skies.
These 130 stars are a miniscule fraction of the 200 billion stars in the Milky Way galaxy. And yes, you could say our entire galaxy is a tiny neighborhood if we compare it to the whole universe!
The Disappearing Rings
Savor your time with Saturn’s rings throughout the next month, because in late March, they will seem to vanish!
On March 23, Saturn’s rings will shift to be “edge-on,” so that we cannot see the bright face of them at all.
Credit: MPM Planetarium
The rings are like a ginormous, skinny donut encircling the planet. They are extremely wide and incredibly thin.
Rings of Saturn Dimensions:
- 175,000 miles wide (282,000 kilometers)
- 0.5 miles thick (almost 1 kilometer)
While they might look solid, they are made of billions of pieces of floating rock and ice, on average about the size of your fist. The ice is especially reflective, and sunlight bouncing off these chunks of space debris gives us the gorgeous view of the rings we love, especially in false-color images that highlight infrared light. The assorted colors indicate heights and compositions of cloud layers which are thought to consist of ammonia ice crystals.
Credit: NASA Hubble Space Telescope
Saturn's equator is tilted 26.7 degrees relative to its orbit around the sun. This tilt is similar to Earth's tilt of 23.4 degrees. As both planets move, the rings appear to tilt up and down, showing more or less of their face. When the radius of the rings is perfectly aligned with our line of sight, we can only see the very thin rim of the disk, which is imperceptible (recall they are 0.5 miles thick), so they disappear.
The rings will slowly reappear after March 23 until they disappear again in November.
HOW DID SATURN’S RINGS FORM?
The leading theory is that Saturn’s rings are the debris from a moon, comet, or asteroid that drifted too close and was torn apart by Saturn’s immense gravity. The strength of gravity gets weaker the further you are from its source, so if a large object like an icy moon gets close to a very massive planet, it will experience tidal forces. The side closest to the planet feels a much stronger pull than the center, which, in turn, feels more gravity than the side facing away from the planet, resulting in a lethal game of tug-of-war that tears the asteroid apart. This is the same effect that causes Earth's tides!
Credit: NASA Hubble Space Telescope
Above is a simulation in which the Moon orbits way too close to the Earth. Tidal forces from the Earth’s gravity rip fragments from the Moon, tearing it apart. Collisions of various nearby asteroids, moons, and comets could have created numerous pieces of rubble that contributed to the formation of Saturn’s rings.
WHY ARE SATURN’S RINGS SO MUCH LARGER THAN THE OTHER JOVIAN PLANETS?
Saturn’s region of space is optimal for large ring formation. It formed closer to the sun than Uranus and Neptune, where there’s a higher density of material, but also far enough from the sun to have lower temperatures which means more frozen, solid matter.
Jupiter’s four large Galilean moons (Io, Europa, Ganymede, and Callisto) prevented the formation of a substantial ring system.
HOW LONG HAS SATURN HAD RINGS? WILL IT ALWAYS HAVE THEM?
The age of Saturn’s rings is currently under dispute. Their age is calculated based on how contaminated they are with the cosmic dust that continuously washes through our solar system. This is like determining how long it’s been since a shelf was cleaned by running your finger across it to see how much dust you pick up.
Studies have found Saturn’s rings to be somewhere between 100-400 million years old, extremely young on astronomical scales. If these estimates are correct, Earth has had sharks for longer than Saturn has had rings! But researchers in Japan argue that Saturn’s rings are not young, they are just more dust-resistant than we thought, and that they actually formed with the planet, more than four billion years ago.
Regardless of how long they’ve been around so far, scientists are confident they don’t have much time left. Based on observations from both Voyagers and the Cassini expeditions, NASA researchers have determined that the rings’ material is raining down on the planet at a rate so enormous, they likely have less than 100 million years to live and are sure to be entirely lost within the next 300 million years.
Credit: NASA Hubble Space Telescope
While Saturn’s rings’ disappearance this March is a line-of-sight trick, it may be a sneak peek into what Saturn will really look like in millions of years. So, enjoy the views of this distant world whenever you get the chance. Of all the celestial objects seen through a small backyard telescope or a big NASA spacecraft, Saturn and its dazzling rings often rank at the top of the list!
Mars
Mars has always captured our imagination. From science fiction books and movies to stunning images from visiting spacecraft to simply spotting its red light in our night skies, Mars is one of our top frontiers in space.
Current views of the red planet come from the rovers Curiosity and Perseverance, orbiters like MAVEN and Tianwen-1, and our Earth-based telescopes. But what about the next step: getting people out there?
With recent movies like The Martian, it is a fascinating question; however, scientists must figure out how to get physical things back to Earth in the first place!
Credit: NASA; Rock Collection by Perseverance Rover
NASA’s Mars Sample Return (MSR) program is the main mission to fulfill that important middle step of returning things to Earth, specifically the samples that the Perseverance rover has already been working hard to collect. In April 2024, NASA announced its objective “to seek innovative designs that will lower cost, risk, and mission complexity,” soliciting proposals for retrieval strategies from the larger NASA community and private industry.
This January, NASA shared its plan to explore two paths for potential “landing architectures” during their formulation phase of the MSR mission. These options include the previously demonstrated procedures and designs for the “sky crane method,” used with both the Curiosity and Perseverance missions, or using new “commercial capabilities” in private industry to deliver the payload to Mars.
Credit: NASA; Illustration of Sky Crane Mars Landing of Rovers
According to NASA administrator Bill Nelson in an interview with NPR on January 7, 2025, initial estimates of the MSR mission had put the cost at around 11 billion dollars. The return of Martian rocks would be delayed until the 2040s. With the utilization of these two new options, Nelson explained, the cost could be brought down to a range of $6-7 billion, with a quicker sample turnaround by 2039.
Furthermore, the Artemis Program, which seeks to bring humans back to the moon in September 2026, has a long-term goal of establishing a permanent lunar base for further solar system exploration, a possible launching point for the MSR program.
WE ALREADY HAVE ROCKS FROM MARS!
While we have a long wait for these Martian rocks from the MSR mission, we sometimes forget we already have them: meteorites from the red planet!
Around 300 meteorites are thought to have originated on Mars. That is a tiny fraction of the 70,000 meteorites that have been identified on Earth. Surface explosions from large meteor impacts propel rocks from Mars into space. This Martian debris swirls around the solar system before crashing down onto Earth millions of years later. We know they are from Mars by studying their chemical compositions. Scientists compare these results to the chemical results from previous NASA missions to Mars, and voila! The results match and we have rocks from Mars.
Credit: NASA Mars Meteorite ALH84001
Credit: NASA; Inside Image of Mars Meteorite ALH84001
The most famous Martian meteorite is Allan Hills 84001 (ALH84001). The rock was found in Antarctica in December 1984. By 1996, scientists proposed the rock bore the likeness of microscopic bacteria fossils, suggesting proof of previous life on Mars (Phys.org, 2022). With detailed images of inside the rock, done with electron microscopy, it even looked like living organisms.
It made headlines all over the world! The claim was controversial from the start, but the presence of “organic compounds” was intriguing, propelling further study. It was later proven in the journal Science that the organic molecules in the rock most likely came from water, not life. This still made ALH84001 the only Martian meteorite originating from Mars when it still had liquid water on its surface.
Though to some it was disappointing alien life could not be proved, the intriguing results encourage further scientific inquiry and future missions to the red planet.
Space in Sixty Seconds
See falling hearts, and take a trip to Mars!
Sky Sights
The Moon, Venus, and Saturn form a beautiful celestial trio from January 31 to February 2.
Look high in the south for Jupiter shining brighter than any star. The bright planet makes a great pair with the red star Aldebaran. The Moon orbits by on February 6 and 7.
Mars and the Moon shine brightly in Gemini the Twins from February 8 through 10.
Catch the waning gibbous Moon glowing near the bright blue star Spica on February 16 through 18. Then, see the waning crescent Moon shine among the stars of Scorpius and Sagittarius.
Mercury is low in the WSW sky in the last few nights of February. Look about 45 minutes to one hour after sunset.
February Star Map
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