Unique exoplanets, moonquakes, underground lakes on Mars — the big space stories of 2019

Close encounter with the farthest solar system object ever

Pluto’s visitor, the New Horizons spacecraft, flew along on its journey and performed a close encounter with an object named 2014 MU69, officially named 486958 Arrokoth.

Formerly named Ultima Thule, a name that was later abandoned due to its Nazi connotations, the trans-Neptunian object is a contact binary. It consists of two bodies fused together. Arrokoth is also the most primitive object ever visited by a spacecraft.

China creates history, lands on the far side of the moon

China’s ambitious space plans took a giant leap after China landed its Chang’e 4 lander on the far side of the moon, the side that can’t be seen from Earth and has been untouched before.

The Chinese mission was quite similar to India’s second moon mission Chandrayaan-2, and was fortunately a success.

The lander carries with it a biosphere experiment consisting of tomato, potato and a flowering plant’s seeds, and silkworm eggs, within a sealed container.

Since the far side is not visible to us, the rover uses the Yutu-2 orbiter to communicate with Earth.

Unfortunately, both India’s Chandrayaan-2’s Vikram lander as well as the private Israeli Beresheet lander crashed in their attempts to touch down gently on the lunar surface.

Scientists do think that a canister of tardigrades may have survived on the moon after the Beresheet lander crashed, in what could potentially be a violation of the international space treaty, which prohibits organic contamination. The issue didn’t escalate as the moon is barren and unable to support life in any way.

Also read: Fresh discoveries—18 earth-sized exoplanets & a 50 million-year-old fossil of 259 fish

Developments on Mars 

Mars is always in the news. As a planet fully populated by robots performing active science, and as a planet that could have been potentially hospitable to life, there is always something exciting happening in the red world. 

This year saw a series of discoveries having to do with water: A former planet-wide underground water system’s evidence was discovered and researchers later showed promising evidence of even existing underground lakes. Ground penetrating radar also discovered water under the Martian North Pole, while more evidence was discovered that a mega-tsunami had occurred on the planet once upon a time. 

Even water ice, and not just carbon dioxide ice was discovered. Meanwhile, scientists this year confirmed the presence of methane on Mars, a strong indicator of present or future life, or geological activity. That too was confirmed when towards the end of the year, the first active fault zone was discovered on Mars and indicated that the planet was currently undergoing marsquakes.

Series of Fast Radio Bursts

In January, scientists detected a series of Fast Radio Bursts (FRBs) coming from outer space. These are not intelligent in origin, but clearly come from a repeating radio source and are always a matter of great excitement. The source of the first series was estimated to be 1.5 billion light years away. 

Later in the year, Russian astronomers detected more FRBs from the direction of the Andromeda and Triangulum Galaxy while analysing existing archival data.

Yet another discovery was made to a galaxy, nearly 8 billion light years away. The increasing frequency of detecting these FRBs, which were earlier thought to be rare and unique, indicates that any regular galaxy is capable of producing them. As our technology improves for detecting radio signals, we hope to be able to find a decent explanation for what causes FRBs. 

Oldest known Earth rock is on the moon

Scientists found out this year that one of the lunar rocks brought back from the moon by astronauts aboard the Apollo 14 in 1971 was actually a rock from Earth.

Analysing the rock showed that it dated back to more than 4.011 billion years, and contains fragments of Earth’s ancient crust. The rock is special because of the nature of the oldest rocks on Earth.

Currently, the oldest rock ever is considered to be 4.4 billion years old, which is in Jack Hills, Australia, but it is most likely debris from rock that disintegrated before. So the moon’s Earth-rock is technically a rock, while the Jack Hills rock is just dust pieces, which are 4.4 billion years old. The finding once again gives an insight into the evolution of Earth and moon. 

Also read: A planet being eaten up, another blacker than coal — bizarre finds in quest for 2nd Earth

Shrinking moon generating moonquakes

When Apollo astronauts reached the moon, they left multiple seismometers on the moon to see if the moon also generated quakes, much like earthquakes. Analysis of this Apollo-era data reveals that it indeed does. 

However, the moon isn’t geologically active. Unlike Earth, it doesn’t have tectonic plates that move and slide around creating earthquakes. On the contrary, the moon is a single piece of solid crust. But it turns out that like a shrivelling raisin, the moon is rapidly cooling and shrinking in the process. As it shrinks, its solid crust breaks at places and develops ‘cracks’, which cause these moonquakes to occur. 

Bizarre dimming and shrinking in stars

This year, astronomers detected three stars that dimmed unexpectedly. A system of binary stars, named EPIC 249706694, started dimming rapidly and then multiple times randomly, suggesting that maybe an exoplanet was orbiting them.

But the suggestion doesn’t fit all the values, and the dimming remains unexplained. Another star dropped in brightness by more than 80 per cent, which is a huge amount of light to have been blocked by a star. It dimmed very quickly and then brightened up slowly, in an asymmetrical fashion. It actually took twice as long to brighten as it did to dim. 

Currently, the star Betelgeuse (pronounced ‘beetle-juice’) is rapidly dimming. Its radius is twice the distance of Sun to Mars and it has dimmed by a factor of two in just three months.

From being one of the brightest objects in the night sky, it is now not even among the 20 brightest stars. Scientists are considering the possibility of it exploding and becoming a supernova.

Voyager-2 sends information about Sun’s bubble boundary

Voyager-2 became the second object to reach interstellar space. It crossed the bubble of solar wind of charged particles emanating from the Sun, which maintains an internal pressure against the pressing material outside called the interstellar medium.

The boundary of this bubble, called the heliosphere, is not fully understood. There are multiple layers here of electromagnetic forces. Comparison of findings from Voyager-1, which crossed the boundary at a different location six years ago, and Voyager-2 shows that the boundary is not uniform and both spacecraft encountered different phenomena on their way out. 

Interstellar visitors

The solar system this year saw the second visitor come in from beyond. Oumuamua was the first interstellar visitor that flew close enough to us to be detectable two years ago. It was flat and cigar-shaped, and we aren’t sure where it came from or what it is, but it is classified as an interstellar asteroid.

This year, we encountered 2I/Borisov, which also came in from outside the solar system. It is the first interstellar comet and studying its structure and tail reveals that it is 14 times the size of Earth. The comet is evaporating as it gets close to Earth and Sun, and the size of its cometary tail of dust and gas is more than 1,50,000 km.

Exomoon & exoplanets

This year, unique discoveries were made to go into our database of planets and moons beyond the solar system. The very first volcanically active exomoon was discovered orbiting a gas planet 550 light years away.

Within our solar system, Jupiter’s moon Io is the most volcanically active one, spewing lava through hundreds of volcanoes, as the moon gets tugged and pulled at by the giant planet and other surrounding large moons. This new moon is thought to be even more volcanic than Io.

Scientists also discovered the first exoplanet exhibiting water vapour in its atmosphere — K2-18b is 110 light years away and resides in what is considered to be a traditional habitable zone for planets. Astronomers confirmed that it is known to have both water vapour in its atmosphere and temperatures that could sustain liquid water on its surface.

Scientists also discovered planets that orbit so close to a star that they are being evaporated, with the star sucking them in, in a process called ablation, and forming a disc. 

Also read: Exoplanet and its host star assigned to India set to get Sanskrit or Bengali names