10 things in space that come in pairs – NASA Solar System Exploration

The February calendar has many twos. There was 02-02-2022 and now 22-02-2022 – which some people call “Twosday”. To mark this Duos Day, we bring you our list of things in the solar system that come in twos or pairs.

1. Binary Asteroids – Sometimes asteroids come in pairs

Asteroids don’t always fly solo. Some have a moon – or a small moon – orbiting the larger body. This is called a binary asteroid system. NASA has a spacecraft traveling to a near-Earth binary asteroid: The Double Asteroid Redirection Test, or DART, is heading to Didymos, which means “twin” in Greek (and explains the word “double” in the name of the mission). Didymos has a moon named Dimorphos. DART will impact Dimorphos almost head-on to demonstrate a method of deflecting asteroids.

The DART target is NOT a threat to Earth. This asteroid system is a perfect testing ground to see if intentionally crashing a spacecraft into an asteroid is an effective way to change its trajectory, should an Earth-threatening asteroid be discovered in the future. No known asteroid larger than 460 feet (140 meters) has a significant chance of hitting Earth in the next 100 years.


2. Double craters

This image shows a remarkable double crater on Mars. Scientists believe the craters must have formed simultaneously. Maybe Mars got hit by a double asteroid. Or it may have been impacted by an asteroid or comet that split into two pieces before hitting the surface.


Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwestern Research Institute/Roman Tkachenko | Full image and caption

3. Kuiper Belt Objects – Strange and Distant Worlds

The small Kuiper Belt Arrokoth Object is the most distant and primitive object ever explored by spacecraft. It was discovered in 2014 by NASA’s New Horizons science team, using the Hubble Space Telescope. The New Horizons spacecraft flew by Arrokoth on January 1, 2019, capturing images that showed a double-lobed object that looked like a partially flattened snowman. It is also very red – even redder than Pluto. The strange shape of the object – unlike any other object visited so far – was the biggest surprise of the flyby.


4. The Earth and its Moon – Quite the pair

The brightest and largest object in our night sky, the Moon makes Earth a more livable planet by moderating the wobble of our home planet as it spins on its axis, leading to a relatively stable climate. . It also causes tides, creating a rhythm that has guided humans for thousands of years, and life in Earth’s oceans for much longer. The Moon likely formed after a Mars-sized body collided with Earth several billion years ago.


5. Pluto and Charon – Double Planet

Pluto has five known moons: Charon, Nix, Hydra, Kerberos, and Styx. The largest of these moons, Charon, is about half the size of Pluto. This makes it the largest satellite relative to the planet it orbits in our solar system. It orbits Pluto at a distance of just 12,200 miles (19,640 kilometers). For comparison, our Moon is a quarter the size of Earth and 20 times farther from Earth. Pluto and Charon are often referred to as a twin planet. This composite of enhanced color images of Pluto (bottom right) and Charon (top left) was taken by NASA’s New Horizons spacecraft as it passed through the Pluto system on July 14, 2015.


6. Two interstellar travelers

NASA’s Voyager 1 and 2 twin spacecraft are exploring where nothing on Earth has gone before. Launched in 1977, each probe is much further from Earth and the Sun than Pluto. In August 2012, Voyager 1 made its historic entry into interstellar space, the region between stars, filled with matter ejected by the death of nearby stars millions of years ago. Voyager 2 entered interstellar space on November 5, 2018. Both spacecraft are still sending scientific information about their surroundings through NASA’s Deep Space Network, or DSN.


Sirius

Credit: NASA/JPL-Caltech

7. Double Stars

Sirius is the brightest star in our sky. It is nicknamed “the Dog Star” because it is the brightest star in the constellation Canis Major (“the Great Dog” in English). The main reason why Sirius is so bright is that it is one of the closest stars to our Sun, just 8.6 light years away. Sirius is actually a binary star system, with a small white dwarf (although you’d need a decent-sized telescope to see it). Sirius is super easy to locate: just look for the constellation Orion. The three bright stars that make up Orion’s belt point downward, toward Sirius. (Unless you’re in the southern hemisphere, and they’re pointing *up* towards Sirius.) Bonus note: The Voyager 2 spacecraft is actually heading towards Sirius. It will pass within 4.3 light-years of the bright star in about 300,000 years.


8. A world with two suns

NASA’s Kepler mission discovered a world where two suns were setting on the horizon instead of just one. The planet, called Kepler-16b, is the most “Tatooine-like” planet ever found in our galaxy and is depicted here in this artist’s concept with its twin stars. (Tatooine is the name of Luke Skywalker’s homeworld in the sci-fi movie “Star Wars”.) In this case, the planet is not considered habitable. It’s a cold world, with a gaseous surface. NASA missions have since discovered at least a dozen other planets orbiting two suns.


9. See Double

No, these are not two images of the same moon. Saturn’s sister moons Rhea and Dione appear side by side in this image captured by NASA’s Cassini spacecraft. The image was taken in visible light on November 1, 2005, when Cassini was approximately 1.1 million miles (1.8 million kilometers) from Rhea, the top image, and 800 000 miles (1.2 million kilometers) from Dione.


10. Rovers on Mars

NASA has two rovers operating on Mars: Perseverance (Mars 2020), which just passed the one-year mark on the red planet; and Curiosity (Mars Science Laboratory), which landed Aug. 5, 2012. This isn’t the first time NASA has had two rovers on Mars. The twin rovers Opportunity and Spirit landed on Mars in 2004. Spirit lasted 20 times longer than its original design until its final communication with Earth in March 2010. Opportunity’s mission ended in February 2019.

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