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We discovered that Bennu the asteroid is spouting out rocks.
Bennu has been around since the beginning of our solar system, with about 4.5 billion years under it's belt. Scientists think the asteroid probably broke off from a larger asteroid from 700 million to 2 billion years ago when it was floating somewhere between Mars and Jupiter. Since then it has moved closer to Earth, enabling scientists to study it. Because it is so old, Bennu may contain some organic molecules similar to those that could have been around when life started on Earth.
In 2018, a spacecraft from the OSIRIS-REx NASA led mission landed on the 1640 foot wide asteroid to do surveys and mineralogical studies of it's surface, and get some samples to take back to Earth.
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When scientists got information from the OSIRIS-REx, they discovered something shocking: Bennu was spitting out rocks! The rocks are up to 4 inches in size and are shot out at speeds of 10 feet per second. This is more than unexpected, given that until recently it was widely thought that asteroids were dead, not active. Bennu's surface gravity is around 1/100,000th of Earth's, and it's definitely not dead.
Scientists think that the rocks being spat out of Bennu are probably caused by one of the following: the thermal stress caused between cold nights and hot days cause the rocks to fracture; water outgassing from clays in the rocks, which apply pressure to smaller bits and eject them; or micrometeorite impacts dislodging the material and causing them to dislodge.
The OSIRIS-REx will orbit Bennu until March 2020, so we're sure this isn't the last we'll hear about the ancient asteroid.
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We witnessed the first ever impact flash of an asteroid hitting the Moon.
On January 17 2019, we Earthlings experienced a total lunar eclipse when the Moon slipped into the Earth's shadow. Eclipses aren't particularly special events, and not much can be gained from it scientifically. But during this one, something unexpected happened while everyone was watching: a small asteroid collided with the Moon's surface, creating a flash impact large enough to see through a small telescope.
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We later found out that the debris was a 99 pound rock the size of a beach ball which hit the Moon at a speed of 37,900 miles per hour. The result was an impact equivalent to around 1.5 tonnes of TNT, which created an impact crater around 30 to 50 feet wide.
Impacts happen to the Moon all the time (that's why it's covered in craters), but the fact that so many telescopes and cameras were pointed at the Moon when this one occurred is pretty serendipitous.
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We saw a Kuiper Belt Object for the first time.
The Kupier Belt is a region in the outer Solar System beyond the 8 planets (not including poor Pluto, which is actually part of the Kuiper Belt). It contains many remnants from the Solar System's formation, and is similar to the Asteroid Belt (although it's 200 times larger).
Objects in the Kuiper Belt had only been witnessed through ground telescopes and the Hubble Space Telescope until the New Horizons spacecraft came onto the scene. First zipping past Pluto in 2015, the spacecraft continued into the dark unknown beyond Pluto. Astronomers looked for a target that the spacecraft could fly by, and found 2014 MU69 (a Kuiper Belt Object), a cold rock that orbits around the Sun past Neptune. When the mission to approach the object was approved, it was full steam ahead.
New Horizons passed by the Kuiper Belt Object on January 1 2019, but it took a few months to transmit the information back to Earth (because 4.1 billion miles is a pretty big distance). The object, which is double-lobed and looks like a snowman, is now officially dubbed Arrokoth.
New Horizons is still out there travelling away from the Sun, and it will have power for another decade or two, so we can probably expect some more groundbreaking information and photos from the spacecraft.
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Aliens! Well, an alien comet from another galaxy.
In 2017, astronomers spotted an object moving so quickly through our Solar System that they concluded it must be from another star (reminder, our Sun is a star) and called it the first interstellar visitor ever seen.
Then, in 2019, we had another visitor: a second object was found, also moving faster than anything in our Solar System. Our second visitor was called 2I/Borisov, and astronomers spotted it just as it was entering our Solar System, giving them time to study it and watch it approach the Sun, heat up, and become active.
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2I/Borisov turned out to have the same elements and molecules as comets from our Solar System, and looked and behaved in exactly the same way. The only difference was that it came from another star, and it was moving at a high speed (maybe after encountering a giant planet and being slingshotted out of it's own Solar System).
What did we learn from the first alien objects to come into our Solar System? That they're exactly the same as the things in ours. This could be very exciting news for our search for life.
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We finally captured an image of a black hole.
The winner of this list, and 2019's greatest astronomical discoveries, is undoubtedly the first ever photo of a black hole. Black holes are hands down the most mysterious things in the universe; so much is unknown about them.
We can't actually see black holes (hence the name), but we can see the environment around them. As matter gets sucked towards the black hole, it piles up around the edges and becomes extremely hot (on the electromagnetic spectrum) before descending into oblivion, and this is what we "see" when we observe a black hole. The problem is that all of them are too far away from Earth to be captured on camera...until one night in 2017 when seven telescopes were pointed to the M87galaxy, which is 55 million light years away. It was a difficult process that took years to complete, but in April 2019, humans saw what a black hole looked like for the first time ever (which is pretty incredible because many people thought they weren't able to be seen).
The Event Horizon Telescope, is now aiming at the Sgr A* black hole, which is in our galaxy, unlike the M87, so there's no doubt that this will be the last image we see of a black hole. It's a pretty exciting time to be alive.
The Most Fascinating Stories From Space in 2019
2019 has been quite a year, and that includes the news from space. With our ever improving technology, we're able to find out more about the vast unknown galaxies around us. Although many notable things happened in space this year, here are the top five stories. For more interesting science-y things, have a look at the best blobs of 2019.
This article first appeared on SYFY.
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