Top Ten Astronomy Stories of 2018

Top Ten Astronomy Stories of 2018
The year 2018 was a good one for astronomers. Mars, asteroids, and the outer Solar System had the limelight more than once. Gaia is bringing the Milky Way into focus, and Hubble found the most distant star ever seen. It was hard to select only ten, but here are my choices for the top stories of 2018.

Lunar eclipse and Mars opposition
The most popular public spectacle was July's total lunar eclipse accompanied by a splendid bright Mars at opposition. It was the longest eclipse of the 21st century, with totality lasting for 1 hr 43 mins, nearly the theoretical maximum. At opposition, Mars lines up with the Earth and the Sun, and this opposition was a particularly close one. [Photo: Kiko Fairbairn]

Dust storm on Mars
The most massive dust storm in over forty years covered Mars from June to August. NASA lost touch with its two rovers, Opportunity and Curiosity. The storm blotted out the sunlight that they need to generate power. Curiosity was back in contact in September, but by the end of the year, nothing had been heard from Opportunity. Intrepid Opportunity had arrived on Mars for a three-month mission, and it was in its fifteenth year of operations when the storm hit.

The Gaia spacecraft of the European Space Agency (ESA) has been making ultra high-precision measurements of the position and brightness of over a billion stars and thousands of other celestial objects. The second data release was in April, and it included a 3D map of the Milky Way, and other virtual reality resources available to scientists and the public.

Very far out
In mid-December Scott Sheppard, David Tholen and Chad Trujillo announced the discovery of the most distant known Solar System body. Its official designation is 2018 VG18, but the discovery team nicknamed it Farout. It's about 100 times farther from the Sun than Earth is.

Organic molecules and an underground lake on Mars
In the search for life, scientists look for certain conditions. Two of these are: organic molecules (molecules containing carbon), and water. The Curiosity rover has found a selection of organic molecules in ancient Martian rocks. Although this isn't a guarantee of living things, it means that life was a possibility. Despite evidence of water in the Martian past, and polar ice caps containing frozen water, liquid water has not been found. Until now. Using data from ESA's Mars Express orbiter, researchers have discovered a lake about 20 km (12.5 mi) across, hiding under the south pole.

A new visitor to Mars arrived at the end of November. NASA's InSight landed on Elysium Planitia, where it will stay put in order to study the Martian interior. It had company on its journey in the form of two small cubesats that launched with it, and provided mission updates in what was almost real time.

Asteroid visits
Two sample-return missions reached their asteroids this year. Japan's Hayabusa2 [Peregrine Falcon-2] arrived at asteroid Ryugu at the end of June. It brought small rovers and a lander to study the surface. Three of them have already dropped to the surface and begun work. Meanwhile NASA's OSIRIS-ReX made its way to asteroid Bennu in early December. It went into orbit around the asteroid on New Year's Eve, and it will study the small body for about a year and a half. Both of these missions will provide clues to the history of the Solar System.

NASA's planet hunters
The Kepler spacecraft revolutionized our knowledge of planets orbiting other stars. It discovered thousands of exoplanets, and the data is still being analyzed. But the craft ran out of fuel last autumn, and it was officially decommissioned in mid-November. However, we might say that the baton has been passed to a new planet hunter, the Transiting Exoplanet Survey Satellite (TESS), launched in April. TESS is expected to find 10,000 new planets, including some Earth-sized ones. Kepler concentrated on a small area of sky, but TESS will be looking at the 200,000 brightest stars around the sky that lie within 200 light years of Earth.

Most distant star
There is usually a limit to how far away astronomers can see an ordinary star. They've seen brilliant stellar explosions called supernovae at great distances, and the most distant objects ever found are galaxies. However, in April the Hubble Space Telescope detected the most distant ordinary star ever. It was 9 billion light years away. Because of the time its light took to get here, astronomers saw it as it was when the Universe was 30% of its current age. This was possible through a rare alignment of a massive galaxy between the star and the telescope. The galaxy acted as a powerful gravitational lens, magnifying the star by around 2000 times.

Voyager 2 crosses into interstellar space
Launched in 1977, Voyager 2 is the only spacecraft that has visited all four of the Solar System's giant planets. In November it left the heliosphere and crossed into the space between the stars. The heliosphere is a protective bubble created by the Sun's solar wind as it blows into the far reaches of the Solar System. The spacecraft's twin, Voyager 1, had already crossed the boundary in 2012, but Voyager 2 has instruments that its twin lacked. This means that it will be able to collect some new types of data. [Photo: NASA/JPL-Caltech]

The back of beyond
Here's an honorable mention for New Horizons which, on New Year's Eve, was nearing its target, Kuiper Belt object 2014 MU69. Informally, the object is known as Ultima Thule, a Latin name given to a place deemed the extreme limit of exploration. Since the flyby actually occurred on New Year's Day, it has already earned a place among the top stories of 2019.

You Should Also Read:
Search for Earth's Twin – book review
Voyager 2 – the Grand Tour
ABC of Astronomy – G is for Gravitational Lens

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