NEOWISE needed a cryogen coolant to keep its sensors cool, and that ran out.
Back in the day, I've heard, particularly with the near-Earth asteroids, there were some asteroid hunters that knew the names of every one.
If we found a hazardous asteroid, we could nudge it out of the way.
NASA has hit a comet with an impactor, during the Deep Impact mission. The goal of that mission was to study the surface by making a crater and stirring up the surface material so it could be studied.
Changing the asteroid's velocity changes the time when the asteroid crosses Earth's orbit. After all, just because it crosses Earth's path doesn't mean there is necessarily going to be a collision. It has to cross Earth's path when the Earth is right there.
By searching the sky now, me and other asteroid hunters hope to give us the early warning - ideally decades - that we need. But that strategy of focused searching hasn't stopped people from thinking about what we might do if an asteroid was on its way toward us.
On the whole, asteroids tend to leave Earth alone. And day to day, there really isn't cause for most people to give them any thought. But despite being remote objects that most people have never seen, asteroids, and the threat they pose, come up an awful lot in popular culture.
I love studying asteroids because they are relatively simple, just rocks in space. They can be understood with physics and described with elegant equations. For the most part, they are serene celestial bodies.
When I tell people I'm a space scientist studying asteroids, they sometimes assume I'm a super-smart math whiz. The kind of person who skipped a bunch of grades and went to college when they were sixteen. Although I am good at math, school was difficult for me, and I didn't get straight A's.
I think every time we send a spacecraft to an asteroid or comet, we learn more.
People have discovered asteroids in the Main Belt that outgas like comets, and things on cometary orbits that no longer outgas - that don't have tails. We're finding all of these unique cases.
I think the public perception about asteroids is that they're kind of metaphors for acts of God, the fact that we have no control over the universe. They're always seen as these uncontrollable events. But when you look at the science, they're actually the exact opposite.
The best thing to do is to study these asteroids so we know the range of parameters we would have to deal with and also to find them so we have as much time as possible to prepare.
There's been a lot of really great intensive research into earthquakes, but we can't predict an earthquake down to the day. We can't predict where a hurricane is going to be a month in advance.
The basic method to find asteroids hasn't changed much in hundreds of years. So asteroids in a telescope look just like stars with one exception: They move with time.
Most astronomical work has to do with things that are very, very far away and don't affect our lives very much.
Astronomers are using every technique at their disposal to discover and study asteroids.
One of the reasons NEOWISE is so valuable is that it sees the sky in the thermal infrared. That means that instead of seeing the sunlight that asteroids reflect, NEOWISE sees the heat that they emit. This is a vital capability, since some asteroids are as dark as coal and can be difficult or impossible to spot with other telescopes.
It has only been within my lifetime that asteroids have been considered a credible threat to our planet. And since then, there's been a focused effort underway to discover and catalog these objects. I am lucky enough to be part of this effort. I'm part of a team of scientists that use NASA's NEOWISE telescope.
Asteroids are our oldest and most numerous cosmic neighbors.
