Twosday

Binary Stars

Put your eyes to the test to see if you can spot the first binary stars to ever be known. The second to the end of the Big Dipper’s handle is not one star but two that are both orbiting around their common centre of mass.

Alcor and Mizar are known as a visual binary because although the two stars are gravitationally bound, they are separated enough that both can be viewed individually through a small telescope, or even with a pair of binoculars.

In fact, these stars were considered the opticians of ancient Greece, as Greek soldiers would need to be able to see the two stars as distinct bright dots to be regarded as having excellent vision. We now know that Mizar is actually four stars (two pairs of binaries) and Alcor itself is really a binary too.

It’s estimated that over half of all Sun-like stars are part of multiple star systems, and that figure increases up to 80 percent for massive stars.

Double Quasars

Spotting binary stars is one thing, but you’d need a serious upgrade from your backyard telescope to look to the ancient corners of the universe, where you might come across something brighter than a quasar. What could be brighter than the extremely active nucleus of a galaxy powered by a supermassive black hole? A double quasar of course!

In 2021 scientists found the oldest double quasar – the archaic pair of dazzling lights dates back ten billion years. And the researchers behind the discovery estimate that only one in every 1,000 quasars in the distant universe is a double quasar, so they are rare beasts!

Twin Astronauts

Closer to home are an identical duo, twin brothers Mark and Scott Kelly. Both are now retired NASA astronauts but in 2016 Scott returned to Earth after spending 340 consecutive days in space in the name of research – with he himself being the guinea pig in question. The mission wasn’t to chase British astronaut Tim Peake through the International Space Station (ISS) dressed in a gorilla costume but was instead to help scientists further understand the effects of microgravity, space radiation and confinement in long-duration spaceflights.

Scott was chosen for a unique yearlong mission to the ISS, whilst Mark, his genetic identical, remained on Earth so that researchers could investigate any changes in Scott during and after his time in space. They found that his genes changed while in space (though the majority returned to normal a few weeks after returning to Earth), and his immune response remained heightened, with his mental reasoning and short-term memory becoming dulled and less accurate compared to pre-flight.

Identical Space Probes

Sticking with the theme of twins, Viking 1 and Viking 2 were a pair of identical space probes launched by NASA in 1975 which in the following year became the first successful US mission to land safely on the surface of Mars. Each spacecraft consisted of an orbiter to take images of the Martian terrain from space and to function as a data relay to communicate with Earth, along with a lander that would study the surface of the Red Planet. The Viking 1 lander gave us the first colour images from the ground on Mars and the orbiter captured the famous image ‘Face on Mars’.

More profoundly, the mission found compelling evidence to suggest that Mars once had riverbeds and experienced vast flooding, something that has influenced the continued search for life on Mars and guided the choice of landing sites of current missions. In 2021, NASA’s Perseverance rover touched down in Jezero crater (a previously flooded area that was home to an ancient river delta), with the aim of searching for signs of past life in a potentially habitable region.

Two Moons of Mars

From two feats of human engineering to a couple of odd-looking space potatoes. Phobos and Deimos are the two moons of Mars just 22.2 km and 12.4 km in size, respectively. Phobos has a crater on its surface almost half the size of the moon itself and orbits Mars three times a day making it the closest orbiting natural satellite of any planet in the solar system.

It’s slowly spiralling inwards and in around 50 million years’ time, Mars’ gravity will break the moon apart causing it to form a ring of material around the planet. While the cratered surfaces of both small moons suggest they were captured from the asteroid belt, other theories suggest they formed from the remnants of a larger moon that once orbited around Mars – the jury’s still out on that one.

Galaxy Merging

Not all space duos stay as pairings. As disastrous as it may sound, a galaxy merging, is the universe’s equivalent of a Shakespeare romance. Filled with drama and intimacy, when two galaxies come together, there can be a happy ending.

The Andromeda galaxy is the Milky Way’s closest large neighbouring galaxy and the two are on a collision course set for five billion years from now. When they do merge, their galactic centres will be drawn together, the gas and dust will collide generating a burst of star formation whilst existing stars will likely pass by one another without fuss due to the huge interstellar distances. Stick it in your diaries, it’ll be an event not to miss!