An Asteroid with Its Own Moon Will Zip Past Earth Tonight

An animation shows what the orbit of a moon around asteroid 1999 KW4 looks like.

(Image: © Dr. Steven Ostro et al./NASA)

A very big asteroid with its own little moon is going to zip past Earth tonight (May 25) — close enough that, with some preparation and a decent telescope, amateur astronomers may spot it blotting out the stars.

This moon-and-asteroid system, called 1999 KW4, is made up of two rocks. The big one is about 0.8 miles (1.3 kilometers) wide, according to NASA, and shaped like a spinning top. The smaller one is more elongated and stretches 0.35 miles (0.57 km) along its longest dimension. It points lengthwise toward its much larger twin.

Together, the asteroid and its minimoon will pass Earth at such a strange, steep angle that NASA called them “the least accessible … for a spacecraft mission of any known binary near-Earth asteroid.”

Related: Doomsday: 9 Real Ways Earth Could End

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But that doesn’t mean they aren’t interesting to look at.

The two asteroids will pass closest to Earth at 7:05 pm EDT (1105 GMT), when they’ll be just 3,219,955 miles (5,182,015 km) from the planet’s surface. That’s more than a dozen times the distance between the Earth and the moon in its orbit around our planet, and much too far for the space rocks to pose any threat. In fact, this is the fourth approach the binary asteroids have made toward Earth since they were discovered in 1999, and not the closest. This is not the first time, according to EarthSky, that astronomers plan to make radar images of these asteroids as they pass.

A 2001 series of radar images taken with NASA's Goldstone radar telescope shows 1999 KW4.

(Image: © Dr. Steven Ostro et al./NASA)

Back on May 25, 2001, according to NASA, the asteroids passed about 6.7% closer to Earth than they will this time, at a distance of 3,005,447 miles (4,836,798 km). Seventeen years from now, on May 25, 2036, the rocks will pass 55.2% closer to Earth, at a distance of just 1,443,511 miles (2,323,106 km) — again, posing no threat worth worrying about.

These big rocks have been frequent flyers in our planet’s neighborhood for a long time.

“1999 KW4 approaches within 0.05 AU of Earth several times each century,” NASA’s report on the object said. “This trend exists from at least [the year] 1600 [to] 2500.” [Black Marble Images: Earth at Night]

“AU” refers to “astronomical units,” a unit equal to the distance between Earth and the sun. So 0.05 AU is equal to one-twentieth the distance between Earth and sun, or about 4,650,000 miles (7,480,000 km). The two asteroids have passed even closer to Earth, without incident, several times a century since William Shakespeare was writing, and they will continue to do so until this article is at least 500 years old.

EarthSky reported that during the space rocks’ closest approach, they’ll be most visible in the Southern Hemisphere, appearing as fast-moving shadows against stars in the constellation Puppis. The two asteroids will remain visible for several days, though, according to EarthSky. North American asteroid hunters may spot the objects near the constellation Hydra on the evening of May 27.

NASA said that its Planetary Defense Coordination Office will continue to closely monitor the asteroids.

Originally published on Live Science.

NASA Just Discovered Seven New Exoplanets… So What?

On Wednesday, the scientists at NASA kind of freaked out. They announced the discovery of some seemingly Earth-like planets outside of our solar system, a group of rocky globes they’re calling ‘TRAPPIST-1.’

How far away are these newly-discovered worlds? They’re about 40 light years from Earth. That means using today’s rocket technology (and a whole lot of cash), it would probably take about 11,250 years to get to TRAPPIST-1.

I called up one of NASA’s exoplanet experts, Aki Roberge, to help us break down the find. A specialist in planet formation, Roberge helps plan future missions for NASA, and confirms that the space agency nerds are just about “as excited as we get” about TRAPPIST-1.

Here are 5 reasons why:

Q: Why Are Scientists Freaking Out About TRAPPIST-1?

Roberge: To be completely blunt, the most exiting thing for actual scientists is that these planets are close enough that we’re actually going to be able to study them – particularly when the James Webb Space Telescope launches (October 2018.) When that launches, it will have a real shot at actually taking a look at the atmospheres of these planets – or if they have atmospheres at all. So it’s like a promise of future excitement, in some ways.

I can see why people would think this is more of the same stuff [NASA’s] already been doing. And in some aspects, it is. But it’s a smaller star, it’s closer to us, and it’s got more planets – really tightly packed. The closer the system is to our solar system – the more the star is like the Sun and the planet is like the Earth, the more likely we are to understand what we’re looking at. That’s what makes it exciting.

Q: Why is everyone calling these planets ”Earth-like?’

Roberge: At the moment, all you really tell from the transits is these are small black dots. We just get a radius – and if we’re super lucky – as they were in the case of this system, they can get masses. The sizes and masses of these planets is really valuable information though, because it does suggests that most of them are rocky. Six of the seven planets look like they’re rocky.  And being Earth-sized, we think it’s a good place: an atmosphere thick enough to keep you warm and last for billions of years, but not so thick that you end up being a gas giant planet.

There are, however, several reasons to think that being a rock in the habitable zone of a red dwarf star is not actually a nice place to live, and that those environments are very different from our solar system. A lot of these investigations that are going forward over the next decade are to find the answers to these questions.

The TRAPPIST-1 star has seven Earth-size planets orbiting it. This artist's concept appeared on the cover of Nature on Feb. 23, 2017. (Credit: NASA/JPL-Caltech)

The TRAPPIST-1 star has seven Earth-size planets orbiting it. This artist’s concept appeared on the cover of Nature on Feb. 23, 2017. (Credit: NASA/JPL-Caltech)

Q: Is there water on the surface of these planets?

Roberge: Most of them are the right distance from a star that maybe they could have liquid water on their surfaces. But that’s a huge maybe. Just look at our solar system: we have three rocky planets – about the size of the TRAPPIST-1 planets. We’ve got Earth, Venus and Mars in or near what astronomers call the “habitable zone” – and they couldn’t be more different!

Q: What’s the big deal about ‘rocky’ planets?

Roberge: As far as we know, that’s the only kind of planet that we could have habitable conditions of life on – life that we could actually understand or recognize from interstellar distances. The Earth is unique in the solar system in one really important way: it’s the only planet that has surface life so abundant that it’s affecting the atmosphere. That is noticeable from interstellar distances. So it’s not really that we think Earth-like life is the only life that can be out there. It’s just the only life we can detect.

Q: What can non-scientists get excited about here?

I think this would really bring it home to people that we have neighbors. I think a lot of people are used to thinking “oh, exoplanets, those are all really distant.” As far as the laws of physics go, you could get to TRAPPIST-1 in a human lifetime (~40 years) [But, again, as stated earlier, with toaday’s technology it would probably take about 11,250 years to get to TRAPPIST-1. Hense, the ‘so what’? sentiment. Surely, we can learn to live on this wonderful planet–or not–by then]. So it becomes more of an engineering problem than a laws of physics problem.

Editor’s Note: Questions and answers have been edited for length and clarity.

For more of the best science & technology coverage, follow me on Twitter @hilarx.