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Astronomers Find Earth-Like Planet Just One Star Away

An artist’s impression of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri. Image Credit: ESO/M. Kornmesser

 
The nearest star to Earth (aside from the Sun) might have an Earth of its own, scientists announced today. Proxima b, which orbits the star Proxima Centauri, is a rocky world about our size, mass, and temperature. It orbits within what astronomers call the "habitable zone," and it is able to harbor liquid water on its surface.

In other words, it might be able to support life.

The findings, published today, August 24, in Nature, are the result of work by a research team of more than 30 scientists from around the world who have been documenting their search for just such a planet through the Pale Red Dot campaign (in honor of both Proxima's assumed red hue and the Pale Blue Dot we call home). 

For all the similarities, there are some significant differences between Proxima b and Earth. One year on Proxima b would be 11 Earth days long, and its distance from its host star is less than that of Mercury to the Sun. (Despite being the planet nearest to the Sun, Mercury isn't the boiling cauldron you might expect. It's not even the hottest planet in the solar system—that honor belongs to Venus, whose surface would melt solid lead. Mercury, on the other hand, possesses water ice.) Proxima Centauri is much cooler and smaller than our Sun—it's closer in size to Jupiter—leaving the rocky world of Proxima b suitable for water, atmosphere, and life.

WOBBLY STARS

An exoplanet is a world that orbits a star other than our own. (Scientists have also identified "rogue" exoplanets, which orbit no star at all.) There are more than 3500 identified exoplanets in the universe, orbiting thousands of different stars. Thousands of additional candidate exoplanets have been spotted and await further study before being made official.

Such planets are discovered using several methods. When a planet's orbit places it between its star and Earth, the amount of light we receive from the star is diminished. Dimming over a consistent interval might suggest a planet. Conversely, a planet can sometimes make a star seem brighter, depending on its closeness to the star and the thermal radiation it thus emits. Planets with significant mass have a gravitational pull on stars. We can detect such movements by way of the Doppler effect. Electromagnetic waves produced by a star as it approaches the Earth are of a different frequency than waves produced by a star as it moves away. Shifting frequencies of a star suggest a wobble, and therefore the possible influence of a planet.

It is the latter technique scientists used to find Proxima b. An observed wobble doesn't automatically mean an exoplanet; sunspots can have the same apparent effect. However, research by John Barnes of the Open University in England ruled out sunspots as the cause of Proxima Centauri's oscillations. "Once we had established that the wobble wasn’t caused by star spots, we knew that there must be a planet orbiting within a zone where water could exist, which is really exciting," he said in a press statement.

SECOND STAR TO THE RIGHT

Proxima Centauri is a red dwarf that's much smaller than our Sun—only about one-eighth the mass—and cannot be seen by the naked eye. It has a lower luminosity, though does exhibit occasional, intense flares of brightness. Such activity, combined with other factors, means that the star has a good four trillion years of life left in it. (The universe itself is only 14 billion years old.)

Before you start packing for the journey to visit our neighbor, know that Proxima Centauri is approximately 38.25 trillion kilometers, or about four light-years, from Earth, and it would take us tens of thousands of years to reach it with existing propulsion systems. Still, studying the star and its newly discovered rocky world will be made much easier once the James Webb Space Telescope, the successor to Hubble, launches in 2018 and the European Extremely Large Telescope comes online in Chile in 2024. If subsequent discoveries indicate the presence of a friendly atmosphere, it would be, according to Barnes, "arguably one of the most important scientific discoveries we will ever make."

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NASA, JPL-Caltech
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It's Official: Uranus Smells Like Farts
NASA, JPL-Caltech
NASA, JPL-Caltech

Poor Uranus: After years of being the butt of many schoolyard jokes, the planet's odor lives up to the unfortunate name. According to a new study by researchers at the University of Oxford and other institutions, published in the journal Nature Astronomy, the upper layer of Uranus's atmosphere consists largely of hydrogen sulfide—the same compound that gives farts their putrid stench.

Scientists have long suspected that the clouds floating over Uranus contained hydrogen sulfide, but the compound's presence wasn't confirmed until recently. Certain gases absorb infrared light from the Sun. By analyzing the infrared light patterns in the images they captured using the Gemini North telescope in Hawaii, astronomers were able to get a clearer picture of Uranus's atmospheric composition.

On top of making farts smelly, hydrogen sulfide is also responsible for giving sewers and rotten eggs their signature stink. But the gas's presence on Uranus has value beyond making scientists giggle: It could unlock secrets about the formation of the solar system. Unlike Uranus (and most likely its fellow ice giant Neptune), the gas giants Saturn and Jupiter show no evidence of hydrogen sulfide in their upper atmospheres. Instead they contain ammonia, the same toxic compound used in some heavy-duty cleaners.

"During our solar system's formation, the balance between nitrogen and sulfur (and hence ammonia and Uranus’s newly detected hydrogen sulfide) was determined by the temperature and location of planet’s formation," research team member Leigh Fletcher, of the University of Leicester, said in a press statement. In other words, the gases in Uranus's atmosphere may be able to tell us where in the solar system the planet formed before it migrated to its current spot.

From far away, Uranus's hydrogen sulfide content marks an exciting discovery, but up close it's a silent but deadly killer. In large enough concentrations, the compound is lethal to humans. But if someone were to walk on Uranus without a spacesuit, that would be the least of their problems: The -300°F temperatures and hydrogen, helium, and methane gases at ground level would be instantly fatal.

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Scott Butner, Flickr // CC BY-NC-ND 2.0
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Look Up! The Lyrid Meteor Shower Arrives Saturday Night
Scott Butner, Flickr // CC BY-NC-ND 2.0
Scott Butner, Flickr // CC BY-NC-ND 2.0

There is a thin line between Saturday night and Sunday morning, but this weekend, look up and you might see several of them. Between 11:59 p.m. on April 21 and dawn on Sunday, April 22, the Lyrid meteor shower will peak over the Northern Hemisphere. Make some time for the celestial show and you'll see a shooting star streaking across the night sky every few minutes. Here is everything you need to know.

WHAT IS THE LYRID METEOR SHOWER?

Every 415.5 years, the comet Thatcher circles the Sun in a highly eccentric orbit shaped almost like a cat's eye. At its farthest from the Sun, it's billions of miles from Pluto; at its nearest, it swings between the Earth and Mars. (The last time it was near the Earth was in 1861, and it won't be that close again until 2280.) That's quite a journey, and more pressingly, quite a variation in temperature. The closer it gets to the Sun, the more debris it sheds. That debris is what you're seeing when you see a meteor shower: dust-sized particles slamming into the Earth's atmosphere at tens of thousands of miles per hour. In a competition between the two, the Earth is going to win, and "shooting stars" are the result of energy released as the particles are vaporized.

The comet was spotted on April 4, 1861 by A.E. Thatcher, an amateur skywatcher in New York City, earning him kudos from the noted astronomer Sir John Herschel. Clues to the comet's discovery are in its astronomical designation, C/1861 G1. The "C" means it's a long-period comet with an orbit of more than 200 years; "G" stands for the first half of April, and the "1" indicates it was the first comet discovered in that timeframe.

Sightings of the Lyrid meteor shower—named after Lyra, the constellation it appears to originate from—are much older; the first record dates to 7th-century BCE China.

HOW CAN I SEE IT?

Saturday night marks a first quarter Moon (visually half the Moon), which by midnight will have set below the horizon, so it won't wash out the night sky. That's great news—you can expect to see 20 meteors per hour. You're going to need to get away from local light pollution and find truly dark skies, and to completely avoid smartphones, flashlights, car headlights, or dome lights. The goal is to let your eyes adjust totally to the darkness: Find your viewing area, lay out your blanket, lay down, look up, and wait. In an hour, you'll be able to see the night sky with great—and if you've never done this before, surprising—clarity. Don't touch the smartphone or you'll undo all your hard ocular work.

Where is the nearest dark sky to where you live? You can find out on the Dark Site Finder map. And because the shower peaks on a Saturday night, your local astronomy club is very likely going to have an event to celebrate the Lyrids. Looking for a local club? Sky & Telescope has you covered.

WHAT ELSE IS GOING ON UP THERE?

You don't need a telescope to see a meteor shower, but if you bring one, aim it south to find Jupiter. It's the bright, unblinking spot in the sky. With a telescope, you should be able to make out its stripes. Those five stars surrounding it are the constellation Libra. You'll notice also four tiny points of light nearby. Those are the Galilean moons: Io, Europa, Ganymede, and Callisto. When Galileo discovered those moons in 1610, he was able to prove the Copernican model of heliocentricity: that the Earth goes around the Sun.

THERE'S BAD WEATHER HERE! WHAT DO I DO?

First: Don't panic. The shower peaks on the early morning of the 22nd. But it doesn't end that day. You can try again on the 23rd and 24th, though the numbers of meteors will likely diminish. The Lyrids will be back next year, and the year after, and so on. But if you are eager for another show, on May 6, the Eta Aquariids will be at their strongest. The night sky always delivers.

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