This morning, the New Horizons probe zinged safely1 past Pluto. Before it did, it transmitted the best photo we've seen of Pluto so far...the last one we'll get before we get the really good stuff. Look at this:
The probe's "I'm OK!" message will reach Earth around 9pm ET tonight and we'll start seeing photos from the flyby Wednesday afternoon...there's a NASA press conference scheduled for 3pm ET on July 15. So exciting!
Update: The photo above is also the best full-disk image of Pluto that we will get...the rest will be close-ups and such. So that's the official Pluto portrait from now on, folks.
Well, hopefully. The probe is due to transmit a "I'm OK!" message back to Earth later today (at around 9pm ET). *fingers crossed*↩
As the New Horizons probe nears Pluto, I've been reading a bit more about how it's going to work and what sort of photos we're going to get. Emily Lakdawalla has a comprehensive post about what to expect when you're expecting a flyby of Pluto. The post contains an image of approximations of the photos New Horizon will take, using Voyager images of Jovian and Saturnian moons as stand-ins. The highest resolution photo of Pluto will be 0.4 km/pixel...it'll have this approximate level of detail:
Which is pretty amazing and exciting considering that before the mission started this was our best view of Pluto:
NASA's Eyes app lets you see a simulation of the probe as it approaches Pluto, but if you don't want to download anything, you can watch this video of the flyby instead:
I had no idea the probe spun around so much as it grabs photos & scans and then beams them back to Earth. And the flyby is so fast! New Horizons is currently moving at 32,500 mph relative to the Sun...it's travelling just over 9 miles every second. (via @Tim_Meyer_ & @badastronomer)
New Horizons will reach its closest approach to Pluto in just under 6 days, on July 14. The probe will pass within 7,800 miles of the surface...I can't wait to find out what that day's photos look like.
Update: You don't even need to wait until tomorrow for that better image...here's one that NASA released just a short while ago. Tune in tomorrow for an even better view.
"If the Milky Way is a sea of stars, then these newly discovered galaxies are like wisps of clouds", said van Dokkum. "We are beginning to form some ideas about how they were born and it's remarkable they have survived at all. They are found in a dense, violent region of space filled with dark matter and galaxies whizzing around, so we think they must be cloaked in their own invisible dark matter 'shields' that are protecting them from this intergalactic assault."
The night sky in such galaxies would look a lot like our skies do in large cities:
"If there are any aliens living on a planet in an ultra-diffuse galaxy, they would have no band of light across the sky, like our own Milky Way, to tell them they were living in a galaxy. The night sky would be much emptier of stars," said team member Aaron Romanowsky, of San Jose State University.
A group of astronomy enthusiasts rented a plane and flew through the shadow cast by the recent eclipse of the Sun. One passenger took the following video. Look at that shadow creeping across the cloud cover! So cool.
Ok, Pluto fans. They evicted Pluto from our solar system's planetary pantheon, but a NASA mission launched in 2006 is nearing the dwarf planet with its cameras. We'll soon have photos of Pluto that are much more high resolution than we currently have, which means scientists will need names for all the new geographic features. The Our Pluto site has been set up to help suggest and vote on names for these features. Naming themes include historic explorers, travelers to the underworld, and scientists and engineers. Go vote! (via slate)
We see these vents in the ocean bottom on Earth, too. The water there is very hot, heated by tectonic processes inside Earth's crust. It brings up minerals and nutrients, and life thrives there. A lot of the processes are the same as what's imagined is happening on Enceladus; minerals are dissolved in hot water that spews up into the cold ocean, precipitating out. A lot of it is sulfur based, but amazingly life exists there anyway. The environment is highly toxic to humans-huge pressure, boiling water near the vents, freezing a bit farther away, and loaded with icky chemicals-but as a scientist once said, "Life finds a way."
Between the evidence of past flowing water on Mars, Titan's hydrocarbon lakes, Europa's underground ocean, and Enceladus, it seems increasingly probable we'll find life somewhere else in the solar system. That's a pretty exciting prospect! (via @ericholthaus)
Update: It was also announced today that the Hubble has detected signs of a salty underground ocean on Jupiter's moon Ganymede.
New observations of the moon using Hubble support this. Ganymede has a weak magnetic field, and, like on Earth, this generates an aurora-the glow created when high-speed subatomic particles slam into the extremely thin atmosphere. This glow is brightest in ultraviolet, and so astronomers used the Space Telescope Imaging Spectrograph (my old camera!) on Hubble to observe Ganymede. STIS is quite sensitive to UV and detected the aurora.
Now this part is a bit tricky: Jupiter has a powerful magnetic field as well, which interacts with Ganymede's. As they do, the aurora changes position over time, moving up and down in latitude. However, the observations show that the aurorae do not change nearly as much as expected if Ganymede were solid. The best way to explain this is if the moon has a salty ocean under its surface. The ocean would have its own magnetic field and would resist the influence of Jupiter's magnetic field, which in turn keeps the aurora steadier.
Turns out there's water all over the place in the solar system. How about that?
Supernovas are among the most violent and rare events in the universe, occurring perhaps once per century in a typical galaxy. They outshine entire galaxies, spewing elemental particles like oxygen and gold out into space to form the foundations of new worlds, and leaving behind crushed remnants called neutron stars or black holes.
Because of the galaxy cluster standing between this star and the Hubble, "basically, we got to see the supernova four times," Dr. Kelly said. And the explosion is expected to appear again in another part of the sky in the next 10 years. Timing the delays between its appearances, he explained, will allow astronomers to refine measurements of how fast the universe is expanding and to map the mysterious dark matter that supplies the bulk of the mass and gravitational oomph of the universe.
Scientists expect the supernova to reappear in the next few years. Gravitational lensing was predicted by Einstein's general theory of relativity and as Overbye writes, "the heavens continue to light candles for Albert Einstein."
For Scientific American, Jen Christiansen tracks down where the iconic image on the cover of Joy Division's Unknown Pleasures came from. Designer Peter Saville found the image, a stacked graph of successive radio signals from pulsar CP 1919, in a 1977 astronomy encyclopedia but it actually originated in a 1970 Ph.D. thesis.
By now I had also combed through early discovery articles in scientific journals and every book anthology on pulsars I could get my hands on to learn more about early pulsar visualizations. The more I learned, the more this descriptor in the 1971 Ostriker caption began to feel significant; "computer-generated illustration." The charts from Bell at Mullard were output in real time, using analogue plotting tools. A transition in technology from analogue to digital seemed to have been taking place between the discovery of pulsars in 1967 to the work being conducting at Arecibo in 1968 through the early 1970's. A cohort of doctoral students from Cornell University seemed to be embracing that shift, working on the cutting edge of digital analysis and pulsar data output. One PhD thesis title from that group in particular caught my attention, "Radio Observations of the Pulse Profiles and Dispersion Measures of Twelve Pulsars," by Harold D. Craft, Jr. (September 1970).
When a star gets old and fat, it explodes in a supernova, leaving a neutron star in its wake. Neutron stars are heavily magnetized and incredibly dense, approximately two times the mass of the Sun packed into an area the size of the borough of Queens. That's right around the density of an atomic nucleus, which isn't surprising given that neutron stars are mostly composed of neutrons. A teaspoon of neutron star would weigh billions of tons.
A pulsar is a neutron star that quickly rotates. As the star spins, electromagnetic beams are shot out of the magnetic poles, which sweep around in space like a lighthouse light. Pulsars can spin anywhere from once every few seconds to 700 times/second, with the surface speed approaching 1/4 of the speed of light. These successive waves of electromagnetic pulses, arriving every 1.34 seconds, are what's depicted in the stacked graph. Metaphorical meanings of its placement on the cover of a Joy Division record are left as an exercise to the reader.
Nothing is faster than the speed of light. But compared to the unimaginable size of the Universe, light is actually extremely slow. This video is 45 minutes long and during that time, a photon emitted from the Sun1 will only travel through a portion of our solar system.
In our terrestrial view of things, the speed of light seems incredibly fast. But as soon as you view it against the vast distances of the universe, it's unfortunately very slow. This animation illustrates, in realtime, the journey of a photon of light emitted from the sun and traveling across a portion of the solar system.
It takes light more than 43 minutes to travel to Jupiter and even to travel the diameter of the Sun takes 4.6 seconds. (thx, andy)
To even fight its way out of the Sun is an incredible journey for a photon. The Sun is so dense that a photon generated at the core is absorbed and re-emitted trillions of times by hydrogen nuclei on its way out. By some estimates, it may take up to 40,000 years for a photon to escape the Sun's surface and head on out to the cold reaches of space.↩
From the Russian Space Agency, a video of what the sky would look like if the Sun were replaced by some other stars. It starts off with the binary star system of Alpha Centuri, but watch until the end for Polaris, which has a radius 46 times that of the Sun.
Although NASA's Hubble Space Telescope has taken many breathtaking images of the universe, one snapshot stands out from the rest: the iconic view of the so-called "Pillars of Creation." The jaw-dropping photo, taken in 1995, revealed never-before-seen details of three giant columns of cold gas bathed in the scorching ultraviolet light from a cluster of young, massive stars in a small region of the Eagle Nebula, or M16.
The second image isn't so immediately amazing but is my favorite of the two. It's a photo of half of the Andromeda galaxy, the big galaxy closest to our own in distance but also in rough size and shape. Here's a very very scaled-down version of it:
The largest NASA Hubble Space Telescope image ever assembled, this sweeping view of a portion of the Andromeda galaxy (M31) is the sharpest large composite image ever taken of our galactic neighbor. Though the galaxy is over 2 million light-years away, the Hubble telescope is powerful enough to resolve individual stars in a 61,000-light-year-long section of the galaxy's pancake-shaped disk. It's like photographing a beach and resolving individual grains of sand. And, there are lots of stars in this sweeping view -- over 100 million, with some of them in thousands of star clusters seen embedded in the disk.
The original image is 1500 megapixels (1.5 gigapixels!), which is so big that you'd need 600 HD televisions to display the whole thing. But if you take the biggest reasonable size available for download (100 megapixels) and zoom in on it, you get this:
That looks like JPEG compression noise, right? Nope, each one of those dots is a star...some of the 100 million individual stars that can be seen in the full image.
As you stroll from one to another, you can't help noticing that the first four planets are really close together. It takes a few seconds, a few tens of steps, to walk from the Sun to Mercury and then on to Venus, Earth and Mars. By contrast, Jupiter is a full two-minute walk down the block, just past Moosewood Restaurant, waiting for someone to stop by and admire it. The remaining planets are even lonelier, each marooned in its own part of town. The whole walk, from the Sun to Pluto, is about three-quarters of a mile long and takes about 15 minutes.
My favorite detail: they added a new station to the Sagan Walk, the star nearest to our solar system. It's in Hawaii.
This is a time lapse of the surface of the Sun, constructed of more than 17,000 images taken by the Solar Dynamics Observatory from Oct 14 to Oct 30, 2014. The bright area that starts on the far right is sunspot AR 12192, the largest observed sunspot since 1990.
The sunspot is about 80,000 miles across (as wide as 10 Earths) and it's visible from Earth with the naked eye. Best viewed as large as possible...I bet this looks amazing on the new retina iMac. (via @pageman)
And here's a neutron star nestled next to Liverpool on the northwest coast of England:
A neutron star also crams in over 1.5 times the mass of the Sun into a tiny ball maybe not much bigger than your daily commute to work, and the Sun is huge (see the size of the Sun later). So this thing is incredibly dense, so dense in fact that just a tea spoon of it would weigh over a billion tonnes, and if you could stand on its surface you'd feel the gravitational pull of 200 billion times that of our planet...not that you'd ever survive it of course.
From Michael Benson comes Cosmigraphics, a survey of many ways in which humans have represented the Universe, from antiquity on up to the present day.
Selecting artful and profound illustrations and maps, many hidden away in the world's great science libraries and virtually unknown today, he chronicles more than 1,000 years of humanity's ever-expanding understanding of the size and shape of space itself. He shows how the invention of the telescope inspired visions of unimaginably distant places and explains why today we turn to supercomputer simulations to reveal deeper truths about space-time.
Among the narrative threads woven into the book are the 18th-century visual meditations on the possible design of the Milky Way - including the astonishing work of the undeservedly obscure English astronomer Thomas Wright, who in 1750 reasoned his way to (and illustrated) the flattened-disk form of our galaxy. In a book stuffed with exquisite mezzotint plates, Wright also conceived of another revolutionary concept: a multigalaxy cosmos. All of this a quarter-century before the American Revolution, at a time when the Milky Way was thought to constitute the entirety of the universe.
Spanning from comets in the south to the termination shock zone in the northern part of the country, The Sweden Solar System is a scale model of the solar system that spans the entire country of Sweden, the largest such model in the world.
The Sun is represented by the Ericsson Globe in Stockholm, the largest hemispherical building in the world. The inner planets can also be found in Stockholm but the outer planets are situated northward in other cities along the Baltic Sea.
I do not officially have a bucket list1 but if I did have one, watching a total solar eclipse would be on it. Was just talking about it the other day in fact. Well. I am pretty damn excited for the Great American Eclipse of 2017!
In August 21, 2017, millions of people across the United States will see nature's most wondrous spectacle -- a total eclipse of the Sun. It is a scene of unimaginable beauty; the Moon completely blocks the Sun, daytime becomes a deep twilight, and the Sun's corona shimmers in the darkened sky. This is your guide to understand, prepare for, and view this rare celestial event.
It goes right through the middle of the country too...almost everyone in the lower 48 is within a day's drive of seeing it. Cities in the path of the totality include Salem, OR, Jackson, WY, Lincoln, NE, St. Louis, MO (nearly), Nashville, TN, and Charleston, SC.
Weather will definitely play a factor in actually seeing the eclipse, so I will be keeping an eye on Eclipser ("Climatology and Maps for the Eclipse Chaser") as the event draws near. Early analysis indicates Oregon as the best chance for clear skies. Matt, I am hereby laying claim to your guest room in three years time. So excited!!
The black hole at the center of the Milky Way galaxy is estimated to have a mass of 4 million Suns. The largest black hole astronomers have found so far has a mass of 18 billion solar masses, or more than 4000 times as massive as the Milky Way's.
Around 3.5 billion light-years away, this galaxy is estimated to contain the largest black hole presently known, at 18 billion solar masses. (Although, the error bars for this one and NGC 1277's overlap substantially.) But the most spectacular part of this galaxy -- and why we're able to learn so much about it's central region -- is because there's a 100 million Solar mass black hole (that's 25 times larger than the one at the Milky Way's core) that's orbiting the even larger one!
Also, the largest know galaxy in the Universe is IC 1101, with a mass of 100 trillion solar masses.
We can fit the orbits of four gas giants in the habitable zone (in 3:2 resonances). Each of those can have up to five potentially habitable moons. Plus, the orbit of each gas giant can also fit an Earth-sized planet both 60 degrees in front and 60 degrees behind the giant planet's orbit (on Trojan orbits). Or each could be a binary Earth! What is nice about this setup is that the worlds can have any size in our chosen range. It doesn't matter for the stability.
Let's add it up. One gas giant per orbit. Five large moons per gas giant. Plus, two binary Earths per orbit. That makes 9 habitable worlds per orbit. We have four orbits in the habitable zone. That makes 36 habitable worlds in this system!
If the Moon orbited the Earth at the same distance as the International Space Station, it might look a little something like this:
At that distance, the Moon would cover half the sky and take about five minutes to cross the sky. Of course, as Phil Plait notes, if the Moon were that close, tidal forces would result in complete chaos for everyone involved.
There would be global floods as a tidal wave kilometers high sweeps around the world every 90 minutes (due to the Moon's closer, faster orbit), scouring clean everything in its path. The Earth itself would also be stretched up and down, so there would be apocalyptic earthquakes, not to mention huge internal heating of the Earth and subsequent volcanism. I'd think that the oceans might even boil away due to the enormous heat released from the Earth's interior, so at least that spares you the flood... but replaces water with lava. Yay?
Historic observations as far back as the late 1800s  gauged this turbulent spot to span about 41 000 kilometres at its widest point -- wide enough to fit three Earths comfortably side by side. In 1979 and 1980 the NASA Voyager fly-bys measured the spot at a shrunken 23 335 kilometres across. Now, Hubble has spied this feature to be smaller than ever before.
"Recent Hubble Space Telescope observations confirm that the spot is now just under 16 500 kilometres across, the smallest diameter we've ever measured," said Amy Simon of NASA's Goddard Space Flight Center in Maryland, USA.
Amateur observations starting in 2012 revealed a noticeable increase in the spot's shrinkage rate. The spot's "waistline" is getting smaller by just under 1000 kilometres per year. The cause of this shrinkage is not yet known.
Clive Thompson recently saw the moons of Jupiter with his own eyes and has a moment.
I saw one huge, bright dot, with three other tiny pinpoints of light nearby, all lined up in a row (just like the image at the top of this story). Holy moses, I realized; that's no star. That's Jupiter! And those are the moons of Jupiter!
I'm a science journalist and a space buff, and I grew up oohing and aahing over the pictures of Jupiter sent back by various NASA space probes. But I'd never owned a telescope, and never done much stargazing other than looking up in the night unaided. In my 45 years I'd never directly observed Jupiter and its moons myself.
So I freaked out. In a good way! It was a curiously intense existential moment.
For my birthday when I was seven or eight, my dad bought me a telescope. (It was a Jason telescope; didn't everyone have a telescope named after them?) We lived in the country in the middle of nowhere where it was nice and dark, so over the next few years, we looked at all sorts of celestial objects through that telescope. Craters on the Moon, the moons of Jupiter, Mars, and even sunspots on the Sun with the aid of some filters. But the thing that really got me, that provided me with my own version of Thompson's "curiously intense existential moment", was seeing the rings of Saturn through a telescope.
We had heard from PBS's Jack Horkheimer, the Star Hustler, that Saturn and its rings would be visible and he showed pictures of what it would look like, something like this:
But seeing that with your own eyes through a telescope was a different thing entirely. Those tiny blurry rings, visible from millions of miles away. What a thrill! It's one of my favorite memories.
Super Planet Crash is half game, half planetary simulator in which you try to cram as much orbital mass into your solar system without making any of your planets zing off beyond the Kuiper belt. You get bonus points for crowding planets together and locating planets in the star's habitability zone. Warning: I got lost in this for at least an hour the other day.
NASA announced the discovery of 719 new planets today. That brings the tally of known planets in our universe to almost 1800. 20 years ago, that number was not more than 15 (including the nine planets orbiting the Sun). Here's a rough timeline of the dramatically increasing pace of planetary discovery:
In 1976, legendary cosmologist and astronomer Carl Sagan tried to recruit a 17-year-old Neil deGrasse Tyson to Cornell University. In April of that year, Tyson wrote Sagan a letter informing him of his intention to enroll at Harvard instead:
The Viking Missions referred to in the letter were the two probes sent to Mars in the mid-1970s.
Tyson occupies a role in today's society similar to Sagan's in the 1980s as an unofficial public spokesman of the wonderous world of science. Tyson is even hosting an updated version of Sagan's seminal Cosmos series for Fox, which debuts on March 9th. Here's a trailer:
It will take it just 6 months to burn up its oxygen. Again, when there's not enough oxygen being fused to generate energy to balance the pressure of gravitational contraction, the star begins to shrink, almost doubling the temperature, tripling the density, and causing the silicon (which was produced by the oxygen fusion) to begin fusing, in its own complicated sequence involving the alpha process, with the end result of nickel-56 (which radioactively decays into cobalt-56 and iron-56). This, as before, balances against the gravitational pressure and returns the star to equilibrium.
And now it will take merely 1 day to burn up its silicon. Finally, when there's not enough silicon being fused to generate energy to balance the pressure of gravitational contraction, the star begins to shrink.
This time, however, the core of the star is mostly nickel and iron, and they cannot ordinarily be fused into heavier elements, so as the star shrinks and the temperature and density increase, there is no nuclear fusion ignition of the nickel and iron to counteract the contraction. Here the limit of pressure and density is the electron degeneracy pressure, which is the resistance of electrons being forced to occupy the same energy states, which they can't.
A supernova erupted recently1 in galaxy M82, a mere 11.4 million light years away from Earth, which means that it was close enough to be discovered by someone using an ordinary telescope in London and may be visible with binoculars sometime in the next two weeks.
M82's proximity means that there are many existing images of it, pre-explosion, including some from the Hubble Space Telescope. Cao and others will comb through those images, looking for what lay in the region before. It will not be easy: M82 is filled with dust. But the light the supernova shines on the dust could teach astronomers something about the host galaxy, too. One team is already looking for radioactive elements, such as nickel, that theories predict form in such supernova, says Shri Kulkarni, an astronomer at California Institute of Technology. "Dust has its own charms."
Ok, it didn't erupt recently. M82 is 11.4 million light years away, so the supernova happened 11.4 million years ago and the light is just now reaching us here on Earth.↩
NASA's Solar Dynamics Observatory is getting some really amazing shots of the Sun, including this 200,000 mile-long solar eruption that left a huge canyon on the surface of the Sun:
Different wavelengths help capture different aspect of events in the corona. The red images shown in the movie help highlight plasma at temperatures of 90,000° F and are good for observing filaments as they form and erupt. The yellow images, showing temperatures at 1,000,000° F, are useful for observing material coursing along the sun's magnetic field lines, seen in the movie as an arcade of loops across the area of the eruption. The browner images at the beginning of the movie show material at temperatures of 1,800,000° F, and it is here where the canyon of fire imagery is most obvious.
The level of detail shown is incredible. (via @DavidGrann)
LIGO works by shooting laser beams down two perpendicular arms and measuring the difference in length between them-a strategy known as laser interferometry. If a sufficiently large gravitational wave comes by, it will change the relative length of the arms, pushing and pulling them back and forth. In essence, LIGO is a celestial earpiece, a giant microphone that listens for the faint symphony of the hidden cosmos.
Like many exotic physical phenomena, gravitational waves originated as theoretical concepts, the products of equations, not sensory experience. Albert Einstein was the first to realize that his general theory of relativity predicted the existence of gravitational waves. He understood that some objects are so massive and so fast moving that they wrench the fabric of spacetime itself, sending tiny swells across it.
How tiny? So tiny that Einstein thought they would never be observed. But in 1974 two astronomers, Russell Hulse and Joseph Taylor, inferred their existence with an ingenious experiment, a close study of an astronomical object called a binary pulsar [see "Gravitational Waves from an Orbiting Pulsar," by J. M. Weisberg et al.; Scientific American, October 1981]. Pulsars are the spinning, flashing cores of long-exploded stars. They spin and flash with astonishing regularity, a quality that endears them to astronomers, who use them as cosmic clocks. In a binary pulsar system, a pulsar and another object (in this case, an ultradense neutron star) orbit each other. Hulse and Taylor realized that if Einstein had relativity right, the spiraling pair would produce gravitational waves that would drain orbital energy from the system, tightening the orbit and speeding it up. The two astronomers plotted out the pulsar's probable path and then watched it for years to see if the tightening orbit showed up in the data. The tightening not only showed up, it matched Hulse and Taylor's predictions perfectly, falling so cleanly on the graph and vindicating Einstein so utterly that in 1993 the two were awarded the Nobel Prize in Physics.
An amateur astronomer discovered asteroid J002E3 orbiting the Earth in 2002. By observing how the object was moving and measuring its spectrum, it was determined that the asteroid was man-made and probably the third stage of Apollo 12's Saturn V rocket.
In early September 2002, spectral and photometric observations of J002E3 were made at IRTF and Mt. Biglow in an effort to determine whether the object was an asteroid or a human-made. Early observations yielded a possible spin-rate and orientation. Additional spectral observations were completed in May 2003 at the Air Force Maui Optical Supercomputing (AMOS) site. Through the modeling of common spacecraft materials, the observations of J002E3 show a strong correlation of absorption features to a combination of human-made materials including white paint, black paint, and aluminum. Absorption features in the near IR show a strong correlation with paint containing a titanium-oxide semiconductor. Using the material model and the orbital information, it was concluded that J002E3 is a human-made object from an Apollo rocket upperstage, most likely Apollo 12.
Paul Bogard recently published a book on darkness called The End of Night. Nicola Twilley and Geoff Manaugh interviewed Bogard about the book, the night sky, astronomy, security, cities, and prisons, among other things. The interview is interesting throughout but one of my favorite things is this illustration of the Bortle scale.
Twilley: It's astonishing to read the description of a Bortle Class 1, where the Milky Way is actually capable of casting shadows!
Bogard: It is. There's a statistic that I quote, which is that eight of every ten kids born in the United States today will never experience a sky dark enough to see the Milky Way. The Milky Way becomes visible at 3 or 4 on the Bortle scale. That's not even down to a 1. One is pretty stringent. I've been in some really dark places that might not have qualified as a 1, just because there was a glow of a city way off in the distance, on the horizon. You can't have any signs of artificial light to qualify as a Bortle Class 1.
A Bortle Class 1 is so dark that it's bright. That's the great thing-the darker it gets, if it's clear, the brighter the night is. That's something we never see either, because it's so artificially bright in all the places we live. We never see the natural light of the night sky.
Turning the Sun into a giant radio telescope through gravitational lensing will take some work, but it is possible.
An Italian space scientist, Claudio Maccone, believes that gravitational lensing could be used for something even more extraordinary: searching for radio signals from alien civilizations. Maccone wants to use the sun as a gravitational lens to make an extraordinarily sensitive radio telescope. He did not invent the idea, which he calls FOCAL, but he has studied it more deeply than anyone else. A radio telescope at a gravitational focal point of the sun would be incredibly sensitive. (Unlike an optical lens, a gravitational lens actually has many focal points that lie along a straight line, called a focal line; imagine a line running through an observer, the center of the lens, and the target.) For one particular frequency that has been proposed as a channel for interstellar communication, a telescope would amplify the signal by a factor of 1.3 quadrillion.
New prints in the Dorothy shop: these really cool Hollywood Star Charts, available in Golden Age and Modern Day editions.
The Modern Day version of our Hollywood Star Chart features constellations named after some of the most culturally significant films to have appeared on the silver screen since 1960 - present day. The stars that make up the clusters are the Hollywood stars that appeared in them.
The chart is based on the night sky over New York on June 16th 1960 -- the date of the first showing of Hitchcock's 'Psycho' at the DeMille Theater. With its new approach to storytelling, characterisation and violence it is seen as a key movie in the start of the post-classical era of Hollywood.
The 108 films featured include those chosen for preservation in the US National Film Registry due to their cultural, historical, or aesthetic significance; Academy Award winners; and a few personal favourites. Films include Easy Rider, Bonnie and Clyde, The Exorcist, The Godfather, Chinatown, Star Wars, Pulp Fiction and Avatar.
Click through to YouTube to watch it in the original 4K resolution, which is much better than even 1080p. They produced the video in conjunction with the Night Sky edition of their Field Notes notebooks.
In complete defiance of its parents, NASA's Solar Dynamics Observatory has stared directly at the Sun for the past three years. Here's a video of those three years made from still images taken by the SDO.
During the course of the video, the sun subtly increases and decreases in apparent size. This is because the distance between the SDO spacecraft and the sun varies over time. The image is, however, remarkably consistent and stable despite the fact that SDO orbits the Earth at 6,876 miles per hour and the Earth orbits the sun at 67,062 miles per hour.
The video notes say the animation uses two images per day...it would be nice to see the same animation with a higher frame rate. (via ★interesting)
Great article by Burkhard Bilger about NASA's Curiosity mission to Mars.
The search for life on Mars is now in its sixth decade. Forty spacecraft have been sent there, and not one has found a single fossil or living thing. The closer we look, the more hostile the planet seems: parched and frozen in every season, its atmosphere inert and murderously thin, its surface scoured by solar winds. By the time Earth took its first breath three billion years ago, geologists now believe, Mars had been suffocating for a billion years. The air had thinned and rivers evaporated; dust storms swept up and ice caps seized what was left of the water. The Great Desiccation Event, as it's sometimes called, is even more of a mystery than the Great Oxygenation on Earth. We know only this: one planet lived and the other died. One turned green, the other red.
Perfect read if you've been curious about what Curiosity is up to on Mars but needed something a bit more narrative than the mission home page or Wikipedia page to guide you. Also features the phrase "a self-eating watermelon of despair", so there's that. Oh, and here's the Seven Minutes of Terror video referred to in the story.
Click through for an animated GIF of all the comparisons. Not bad for the telescopic state of the art in 1610. For a taste of how celestial objects actually appeared when viewed through Galileo's telescope, check out this video starting around 7:30. (thx, john)
At a distance of just over 4.3 light years, the stars of Alpha Centauri are only a cosmic stone's throw away. To reach Alpha Centauri B b, as this new world is called, would require a journey of some 25 trillion miles. For comparison, the next-nearest known exoplanet is a gas giant orbiting the orange star Epsilon Eridani, more than twice as far away. But don't pack your bags quite yet. With a probable surface temperature well above a thousand degrees Fahrenheit, Alpha Centauri B b is no Goldilocks world. Still, its presence is promising: Planets tend to come in packs, and some theorists had believed no planets at all could form in multi-star systems like Alpha Centauri, which are more common than singleton suns throughout our galaxy. It seems increasingly likely that small planets exist around most if not all stars, near and far alike, and that Alpha Centauri B may possess additional worlds further out in clement, habitable orbits, tantalizingly within reach.
Saw one of the coolest things ever tonight: a meteor burning up in the lower atmosphere. Super bright, exploded at the end like a firework.
It turned out that "one of the coolest things ever" wasn't hyperbole. You see, earlier that day over the UK, a meteor streaked across the sky for about 50 seconds:
And then the one I saw happened about two-and-a-half hours later. Spurred by this unlikely coincidence, mathematician Esko Lyytinen of the colorfully named Finnish Fireball Working Group of the Ursa Astronomical Association did some calculations and determined that the two events were actually the same meteor.
He believes a large body grazed the upper atmosphere, dipping to an altitude of 33 miles (53 km) over Ireland before escaping back to space. Because it arrived moving at only about 8 miles (13 km) per second, barely above Earth's escape velocity, it lingered for more than a minute as it crossed the sky. (This explains why some witnesses mistook it for reentering spacecraft debris.)
Lyytinen says the brief atmospheric passage took its toll. As the meteoroid broke apart, its velocity dropped to just 5.7 miles (9.2 km) per second, too slow to make an escape back to space. Instead, it became a temporary satellite of Earth, looping completely around the globe before reentering the atmosphere -- this time for good. "It looks now that the fireball witnessed 155 minutes later in U.S. and Canada, may have been one fragment of the British fireball, most probably the biggest one," Lyytinen explains.
These earth-grazers are not common but they do happen from time to time. But a visible Earth grazing meteor that enters the atmosphere twice? Unprecedented. So cool! (thx, alex)
The rest of you can have your Olympics, but the early August event I'm most looking forward to is the arrival on Mars of the Curiosity rover. But NASA has had someproblems in the past delivering payloads to Mars, so this is going to be somewhat of a nail-biter. If you haven't seen it, Curiosity's Seven Minutes of Terror is well worth watching to see the logistical challenge of getting the rover down to the surface.
Curiosity will hopefully land on the surface on Aug 6 at about 1:30 am ET.
Cory Poole made this video of the annular solar ecplise yesterday using 700 photographs from a telescope with "a very narrow bandpass allowing you to see the chromosphere and not the much brighter photosphere below it."
Cory says: "The filter only allows light that is created when hydrogen atoms go from the 2nd excited state to the 1st excited state." Very cool.
The Dyson sphere, also referred to as a Dyson shell, is the brainchild of the physicist and astronomer Freeman Dyson. In 1959 he put out a two page paper titled, "Search for Artificial Stellar Sources of Infrared Radiation" in which he described a way for an advanced civilization to utilize all of the energy radiated by their sun. This hypothetical megastructure, as envisaged by Dyson, would be the size of a planetary orbit and consist of a shell of solar collectors (or habitats) around the star. With this model, all (or at least a significant amount) of the energy would hit a receiving surface where it can be used. He speculated that such structures would be the logical consequence of the long-term survival and escalating energy needs of a technological civilization.
Needless to say, the amount of energy that could be extracted in this way is mind-boggling. According to Anders Sandberg, an expert on exploratory engineering, a Dyson sphere in our solar system with a radius of one AU would have a surface area of at least 2.72x1017 km2, which is around 600 million times the surface area of the Earth. The sun has an energy output of around 4x1026 W, of which most would be available to do useful work.
The downside: we'd have to part with Mercury to do it.
And yes, you read that right: we're going to have to mine materials from Mercury. Actually, we'll likely have to take the whole planet apart. The Dyson sphere will require a horrendous amount of material-so much so, in fact, that, should we want to completely envelope the sun, we are going to have to disassemble not just Mercury, but Venus, some of the outer planets, and any nearby asteroids as well.
I emailed Astronomer Phil Plait about this project, who told me in no uncertain terms that the project doesn't make sense.
"Dismantling Mercury, just to start, will take 2 x 10^30 Joules, or an amount of energy 100 billion times the US annual energy consumption," he said. "[Dvorsky] kinda glosses over that point. And how long until his solar collectors gather that much energy back, and we're in the black?"
I've spent years studying all this, and it still sometimes gets to me: just how flipping BIG the Universe is! And this picture is still just a tiny piece of it: it's 1.2 x 1.5 degrees in size, which means it's only 0.004% of the sky! And it's not even complete: more observations of this region are planned, allowing astronomers to see even deeper yet.
Here's a full view of the image that looks sorta unimpressive:
Indian lunar orbiter Chandrayaan-1 has discovered a large cave on the Moon. Aside from the hey, cool, there's a cave on the Moon factor, the other big feature of the cave is its constant and temperate temperature.
Temperatures on the moon swing wildly, from a maximum of 262 degrees Fahrenheit to a minimum of -292. The cave holds steady at a (relatively) comfortable -4, since the moon's weather can't penetrate its 40-foot-thick wall. It could also protect astronauts from "hazardous radiations, micro-meteoritic impacts," and dust storms, according to paper published by the journal Current Science.
This equation's initial purpose, he wrote, was to put meaningful prices on the terrestrial exoplanets that Kepler was bound to discover. But he soon found it could be used equally well to place any planet-even our own-in a context that was simultaneously cosmic and commercial. In essence, you feed Laughlin's equation some key parameters -- a planet's mass, its estimated temperature, and the age, type, and apparent brightness of its star -- and out pops a number that should, Laughlin says, equate to cold, hard cash.
At the time, the exoplanet Gliese 581 c was thought to be the most Earth-like world known beyond our solar system. The equation said it was worth a measly $160. Mars fared better, priced at $14,000. And Earth? Our planet's value emerged as nearly 5 quadrillion dollars. That's about 100 times Earth's yearly GDP, and perhaps, Laughlin thought, not a bad ballpark estimate for the total economic value of our world and the technological civilization it supports.
Early this week, I started seeing a little traffic to a post I wrote way back in March of 1999 called The new Zodiac.
An interesting calendrical tidbit: the Zodiac that everyone is familiar with today is actually based upon the movement of the sun through the constellations of 2500 years ago. Today, due to shifts in the earth's rotation and orbit, the sun moves through 13 constellations, not just 12.
Capricorn: Jan 20 - Feb 16
Aquarius: Feb 16 - Mar 11
Pisces: Mar 11 - Apr 18
Aries: Apr 18 - May 13
Taurus: May 13 - Jun 21
Gemini: Jun 21 - Jul 20
Cancer: Jul 20 - Aug 10
Leo: Aug 10 - Sept 16
Virgo: Sept 16 - Oct 30
Libra: Oct 30 - Nov 23
Scorpio: Nov 23 - Nov 29
Ophiuchus: Nov 29 - Dec 17
Sagittarius: Dec 17 - Jan 20
Aries: Apr 19 - May 14
Taurus: May 14 - Jun 21
Gemini: Jun 21 - Jul 21
Cancer: Jul 21 - Aug 11
Leo: Aug 11 - Sept 17
Virgo: Sept 17 - Oct 31
Libra: Oct 31 - Nov 21
Scorpio: Nov 21 - Nov 30
Ophiuchus: Nov 30 - Dec 18
Sagittarius: Dec 18 - Jan 21
Capricorn: Jan 21 - Feb 17
Aquarius: Feb 17 - Mar 12
Pisces: Mar 12 - Apr 19
Which calendar to believe? Who knows, but one thing is for sure: astrology remains a steamingpile of horseshit.
The object, called AFGL 3068, is a binary star, two stars in an 800-year orbit around one another. One of them is a red giant, a star near the end of its life. It's blowing off massive amounts of dark dust, which is enveloping the pair and hiding them from view. But the system's spin is spraying the material out like a water sprinkler head, causing this giant and delicate spiral pattern on the sky. And by giant, I mean giant: the entire structure is about 3 trillion kilometers (about 2 trillion miles) across.
Astronomer Francesco Pepe of the Geneva Observatory in Switzerland, who spoke Oct. 11 at an International Astronomical Union symposium on planetary systems, reported a new analysis using only HARPS data, but adding an extra 60 data points to the observations published in 2008. He and his colleagues could find no trace of the planet.
The paper reports the discovery of two new planets around the nearby red dwarf star Gliese 581. This brings the total number of known planets around this star to six, the most yet discovered in a planetary system other than our own solar system. Like our solar system, the planets around Gliese 581 have nearly circular orbits.
The most interesting of the two new planets is Gliese 581g, with a mass three to four times that of the Earth and an orbital period of just under 37 days. Its mass indicates that it is probably a rocky planet with a definite surface and that it has enough gravity to hold on to an atmosphere, according to Vogt.
Gliese 581, located 20 light years away from Earth in the constellation Libra, has a somewhat checkered history of habitable-planet claims. Two previously detected planets in the system lie at the edges of the habitable zone, one on the hot side (planet c) and one on the cold side (planet d). While some astronomers still think planet d may be habitable if it has a thick atmosphere with a strong greenhouse effect to warm it up, others are skeptical. The newly discovered planet g, however, lies right in the middle of the habitable zone.
Sam Arbesman's prediction of May 2011 might have been too conservative. And 20 light years...that means we could send a signal there, and if someone of sufficient technological capability is there and listening, we could hear something back within our lifetime. Contact! (thx, jimray)
Back in July, Ben Terrett wrote a post about how many instances of the word "helvetica" set in unkerned 100 pt Helvetica it would take to go from the Earth to the Moon:
The distance to the moon is 385,000,000,000 mm. The size of an unkerned piece of normal cut Helvetica at 100pt is 136.23 mm. Therefore it would take 2,826,206,643.42 helveticas to get to the moon.
But let's say you wanted to stretch one "helvetica" over the same distance...at what point size would you need to set it? The answer is 282.6 billion points. At that size, the "h" would be 44,600 miles tall, roughly 5.6 times as tall as the Earth. Here's what that would look like:
The Earth is on the left and that little speck on the right side is the Moon. Here's a close-up of the Earth and the "h":
And if you wanted to put it yet another way, the Earth is set in 50.2 billion point type -- Helvetically speaking -- while the Moon is set in 13.7 billion point type. (thx, @brainpicker)
A new Hubble discovery was announced today and it's not for the faint of heart. At least, that is, if you care deeply about mysterious exoplanets 600 light years away.
WASP-12b is orbiting a sun-like yellow dwarf star 600 light-years away and it has such a tight orbit (of only 1.1 days) that it is being roasted to nearly 2,800 degrees Fahrenheit. This superheated state has caused the doomed exoplanet to puff up to nearly twice the size of Jupiter.
WASP-12b is in trouble and there's no Willis/Affleck/Bay mission planned to save it. That said, it's going to take about another 10 million years for WASP-12b to be totally eaten, so it has time to cross a few things off its bucket list.
We have a stellar cluster with thousands of times the Sun's mass embedded in a nebula furiously cranking out newborn stars. A lot of them are near the physical upper limit of how big a star can get. The whole thing is only a couple of million years old, a fraction of the galaxy's lifespan. One beefy star with 90 times the Sun's mass got too close to some other stars, which summarily flung it out of the cluster at high speed, fast enough to cross the distance from the Earth to the Moon in an hour (it took Apollo three days). The star is barreling through the flotsam in that galaxy, its violent stellar wind carving out a bubble of gas that points right back to the scene of the crime, nearly 4 quadrillion kilometers and a million years behind it.
Click through to see the pictures and read a more thorough write up.
PS: 70% of the reason I linked to this is because of the title, "Rampaging cannonball star is rampaging."
In 2004, the Hubble Space Telescope took an image called the Hubble Ultra Deep Field; basically astronomers pointed the Hubble toward an "empty" part of space and took a long-exposure shot in the visible spectrum. What they found were thousands of far away galaxies from early in the development of the universe. Now the Hubble has peered even deeper into the universe in near-infrared and captured this image:
Each one of those little specks is an entire galaxy, some only 600 million years old. Here's a zoomed-in section:
NASA announced that it has found pretty hard evidence of significant amounts of water on the Moon.
"We are ecstatic," said Anthony Colaprete, LCROSS project scientist and principal investigator at NASA's Ames Research Center in Moffett Field, Calif. "Multiple lines of evidence show water was present in both the high angle vapor plume and the ejecta curtain created by the LCROSS Centaur impact. The concentration and distribution of water and other substances requires further analysis, but it is safe to say Cabeus holds water."
I don't have to tell you about the implications here. Just think of how much you could sell authentic Moon bottled water for.
The winner's photo of the Horsehead Nebula (mpastro2001 also had a second photo in the top five) used a 12 1/2" Ritchey-Chretien telescope ($21,500) and an SBIG STL11000 camera ($7,195 and up) with an AO-L adaptive optics accessory ($1,795) on a Paramount ME mount ($14,500). Total cost for just the equipment mentioned here: $44,990.
Within hours, telegraph wires in both the United States and Europe spontaneously shorted out, causing numerous fires, while the Northern Lights, solar-induced phenomena more closely associated with regions near Earth's North Pole, were documented as far south as Rome, Havana and Hawaii, with similar effects at the South Pole.
We Choose the Moon is a site that tracks the activities of the Apollo 11 mission as it happened 40 years ago. Nice work. The transmissions from the spacecraft, CAPCOM, and the lunar lander are cleverly published to and pulled in from Twitter.
With all this 40th anniversary stuff, I'm having trouble getting my mind around that the first Moon landing is as far removed from the present as the low point of The Great Depression was from my birth (i.e. the Moon landing, culturally speaking, is Ollie's Great Depression). See also timeline twins. (via jimray)
When they are passing in front of their stars, their atmospheres are backlit in a way that can make spectroscopic analysis of the different chemicals in their atmospheres comparatively easy: the wavelengths of light absorbed by the various chemicals will show up, in a tiny way, in the spectrum of the starlight. And this is what makes it possible to imagine looking at them for signs of life.
What scientists would look for are planets with unstable atmospheres, which James Lovelock said was an indication of life.
After the extragalactic planet post this morning, Sam Arbesman sent me a link to systemic, a blog dedicated to the search for extrasolar planets written by Greg Laughlin, one of the scientists involved in the effort. Here are two relevant posts. In Forward, Laughlin says we're very close to finding a nearby Earth-like planet:
Detailed Monte-Carlo simulations indicate that there's a 98% probability that TESS will locate a potentially habitable transiting terrestrial planet orbiting a red dwarf lying closer than 50 parsecs. When this planet is found, JWST (which will launch near the end of TESS's two year mission) can take its spectrum and obtain resolved measurements of molecular absorption in the atmosphere.
In Too cheap to meter, Laughlin presents a formula for the land value of such a discovery that depends on how far away the planet is, the age of the star it orbits, and the star's visual magnitude.
Applying the formula to an exact Earth-analog orbiting Alpha Cen B, the value is boosted to 6.4 billion dollars, which seems to be the right order of magnitude. And applying the formula to Earth (using the Sun's apparent visual magnitude) one arrives at a figure close to 5 quadrillion dollars, which is roughly the economic value of Earth (~100x the Earth's current yearly GDP)...
The idea is to use gravitational microlensing, in which a distant source star is briefly magnified by the gravity of an object passing in front of it. This technique has already found several planets in our galaxy, out to distances of thousands of light years. Extending the method from thousands to millions of light years won't be easy, says Philippe Jetzer of the University of Zurich in Switzerland, but it should be possible.
RV shifts are how the vast majority of extrasolar worlds have been discovered, but only because these planets, called "hot Jupiters," are extremely massive and in hellishly close orbits around their stars. Their stellar wobbles are measurable in meters per second; seeing the much smaller centimeters-per-second wobble of an Earth twin is orders of magnitude more difficult. For the Alpha Centauri system, the feat is akin to detecting a bacterium orbiting a meter from a sand grain-from a distance of 10 kilometers. But by devoting hundreds of nights of telescope time to collecting hundreds of thousands of individual observations of just these two stars, Fischer believes she can eventually distill the faint RV signal of any Earth-like planets. It's simply a matter of statistics and brute force. The planets wouldn't reveal themselves as images in a telescope, but as steadily strengthening probabilistic peaks.
Long experience has taught me this about the status of mankind with regard to matters requiring thought: the less people know and understand about them, the more positively they attempt to argue concerning them, while on the other hand to know and understand a multitude of things renders men cautious in passing judgment upon anything new.
There has never been a generation of humans in all of history who could see such an event. If you ever get a little depressed, or lonely, or think like there's nothing going on that's interesting any more, think on that for a moment or two. A thousand generations of people could only imagine such a thing, but we can actually do it.
Start worrying in a few million years about a cosmic dust collision, when the sun hits the closest spiral arm of our galaxy. Take your chances with an exploding star. Or manage to escape these threats, and you just get an extra 10^35 years before all matter decays anyway.
Meg bought Ollie this ball a couple of weeks ago. It's got all the planets of the solar system on it, plus the Sun. But no Pluto. That's right, it's barely been two years since Pluto was demoted to dwarf planet status and the toy manufacturers have already made the adjustment.
It saddens me that Ollie has to grow up in a world where Pluto isn't considered a planet, although I take comfort that his textbooks probably won't be updated by the time he's in school. In the meantime, I've Sharpied Pluto onto his ball.
The southern wall of the Grand Concourse, facing 42nd Street, has semicircular grills high up, with small curlicued spaces like those in a leafy tree. Many of those spaces act like the aperture of a pinhole camera, reflecting an image of the sun that, when it reaches the floor, will be 8 to 12 inches wide. The smaller grill spaces will produce dimmer but sharper solar images on your paper.
The "Pillars of Creation" may be the most iconic Hubble photograph ever taken. "Located in the Eagle Nebula, the pillars are clouds of molecular hydrogen, light years in length, where new stars are being born," says Aguilar. "However, recent discoveries indicate these pillars were destroyed by a massive nearby super nova some 6,000 years ago. This is a ghost image of a past cosmic disaster that we won't see here on Earth for another thousand years or so-and a perfect example of the fact that everything we see in the universe is history."
Finding the Moon when its slim crescent is still less than about 24 hours past the New Moon phase requires careful timing and planning, a challenging project even for experienced observers. In this sighting, only about 0.8 percent of the Moon's disk appears illuminated.
An Einstein Ring happens when two galaxies are perfectly aligned. The closer galaxy acts as a lens, magnifying and distorting the view of a more distant galaxy. But today astronomers announced that they've discovered a double Einstein Ring: three galaxies are perfectly aligned, creating a double ring around the lensing galaxy.
The Moon has been a stabilizing factor for the axis of rotation of the Earth. If you look at Mars, for instance, that planet has wobbled quite dramatically on its axis over time due to the gravitational influence of all the other planets in the solar system. Because of this obliquity change, the ice that is now at the poles on Mars would sometimes drift to the equator. But the Earth's moon has helped stabilize our planet so that its axis of rotation stays in the same direction. For this reason, we had much less climatic change than if the Earth had been alone. And this has changed the way life evolved on Earth, allowing for the emergence of more complex multi-cellular organisms compared to a planet where drastic climatic change would allow only small, robust organisms to survive.
In Galileo's time, nighttime skies all over the world would have merited the darkest Bortle ranking, Class 1. Today, the sky above New York City is Class 9, at the other extreme of the scale, and American suburban skies are typically Class 5, 6, or 7. The very darkest places in the continental United States today are almost never darker than Class 2, and are increasingly threatened. For someone standing on the North Rim of the Grand Canyon on a moonless night, the brightest feature of the sky is not the Milky Way but the glow of Las Vegas, a hundred and seventy-five miles away. To see skies truly comparable to those which Galileo knew, you would have to travel to such places as the Australian outback and the mountains of Peru.
Arecibo Observatory, the world's largest radio telescope, is in danger of being shut down due to budget cuts. Arecibo could run for almost two years for the cost of a single F-16 fighter jet...to say nothing of the small fraction of the cost of the War in Iraq required.
Is the search for aliens such a good idea? If/when we find evidence of extraterrestrial intelligent life, will they welcome us as neighbors, treat us as vermin in their universe or something inbetween? "Jared Diamond, professor of evolutionary biology and Pulitzer Prize winner, says: 'Those astronomers now preparing again to beam radio signals out to hoped-for extraterrestrials are naive, even dangerous.'"
How to survive a black hole. If you're in a rocket ship about to fall into a black hole, you might live a bit longer if you turn on your engines. "But in general a person falling past the horizon won't have zero velocity to begin with. Then the situation is different -- in fact it's worse. So firing the rocket for a short time can push the astronaut back on to the best-case scenario: the trajectory followed by free fall from rest."
On tonight's to-do list: total lunar eclipse. Totality occurs at 5:44pm ET and will last about an hour. On the east coast of the US, the moon will already be eclipsed when it rises. Best bet for seeing it is Africa, Europe, and the Middle East (see map).
Astronomers are tracking a 250-meter-wide asteroid called Apophis which will come within 30,000 km of earth in 2029. However, it's too soon to tell if that near-miss will pull the asteroid into a collision course with the earth 7 years later. "Lu says the best way to deflect an asteroid is with a 'gravity tractor' -- a spacecraft displacing about 1 metric ton that simply hovers near an asteroid and gently tweaks its orbit."