Super-Earth: Astronomers Find a Watery New Planet

An international has spotted a new planet 2.7 times bigger than Earth, circling a dim red star called GJ 1214, just 40 light-years away in the constellation Ophiuchus.

Back in the mid-1990s, when astronomers were just beginning to find new planets around distant stars, nearly every new discovery got front-page headlines. Today, with the extrasolar-planet count up to about 400, it takes something extraordinary to make news.

But extraordinary may be too understated a descriptor for the discovery reported on Wednesday in the journal Nature: an international team led by Harvard astronomer David Charbonneau has spotted a “super-Earth,” a planet 2.7 times bigger than Earth, circling a dim red star called GJ 1214, just 40 light-years away in the constellation Ophiuchus. “It’s spectacular,” says Geoffrey Marcy of the University of California, Berkeley, who is the world’s most prolific planet hunter and is credited with discovering 70 of the first 100 exoplanets. “It’s a top-of-the-top discovery in the quest for Earth-size planets.”

While the new planet, dubbed GJ 1214b, is too big to be considered Earth-like, it comes pretty close. But GJ 1214b’s relatively compact size — smaller than the vast majority of planets identified so far — is only one reason for astronomers’ enthusiasm. Another is GJ 1214b’s likelihood of bearing the stuff of life: water.

If you’re looking for a world where life might thrive, a planet must be at the right temperature for water to exist in liquid form. So it needs to orbit its star in the so-called habitable zone, a “Goldilocks” location that allows a planet to be neither too hot nor too cold. In that respect, GJ 1214b is again a near miss. Its surface temperature hovers at a sweltering 190°C (374°F), which is well above the boiling point of water, at least in Earth’s atmospheric pressure. Fortunately, GJ 1214b’s atmosphere makes the pressure a lot higher than on Earth — “crushing,” as Charbonneau describes it — and increases the odds of liquid water. (Under pressure, water can remain liquid above 100°C, or 212°F.)

Astronomers were further able to estimate the planet’s makeup by calculating its size, based on the amount of light that GJ 1214b blocked when it passed in front of its star, as well as its mass (6.6 times Earth’s mass), based on the wobble in the wavelength of starlight caused by GJ 1214b’s gravitational pull on its star. That analysis revealed the new planet’s density: about one-third of Earth’s. Because water has a much lower density than rock, astronomers figured that the “most plausible scenario is a planet made mostly of water, with a significant atmosphere,” says Charbonneau. So despite its high temperature, GJ 1214b’s high atmospheric pressure and relatively low density mean liquid water could exist there after all.

Nevertheless, it’s too soon to suggest that astronomers have found the site of potential exoplanetary life. “What you want [for life] is a nice toasty ocean with a little bit of atmosphere. That’s not going to happen here,” says Charbonneau. “I think it would be foolish to say categorically that [GJ 1214b] doesn’t have life. But we have no basis for thinking it could.”

If it does, astronomers will be able to look for it in unprecedented detail. Since GJ 1214b is only 40 light-years away, which is practically next door in cosmic terms, its atmosphere can be studied more closely than that of any other exoplanet, both with the Hubble Telescope and with the infrared-sensitive Spitzer Space Telescope. Charbonneau’s team has already applied for observing time on both scopes to do just that.

Perhaps the most exciting thing about the discovery of GJ 1214b is that the planet was found at all. Planet hunters usually focus their attention on Sun-like stars — that is, large and hot — on the assumption that if you’re looking for life, you should look in a place that is as similar to our solar system as possible. Charbonneau, however, focused on about 2,000 small, dim, red stars known as M-dwarfs, nearby Earth. M-dwarfs are much more numerous than Sun-like stars; of the 300 stars closest to Earth, says Charbonneau, 220 or so are M-dwarfs. They’re also much cooler than Sun-like stars, so their habitable zones are close-in. A planet in the Goldilocks position around an M-dwarf doesn’t take a year to orbit, as Earth does; it takes only a few days (1.6 days, in the case of GJ 1214b). So astronomers need to wait only a few days to spot a planet passing by, and only a few weeks to confirm the orbit with several passes.

M-dwarfs are so small, moreover, that an Earth-size planet casts a relatively big silhouette as it passes in front of it, making the telltale dimming of starlight easy to spot. It’s so easy, in fact, that Charbonneau didn’t even need a giant telescope to see it. Instead, he got away with the kind of scope a serious backyard amateur might use. In other words, says Charbonneau, “we did it on the cheap.”

They also did it fast. “We thought it would take us two years to find something like GJ 1214b,” says Charbonneau. “It took just six months. Either we got really lucky, or these planets are common.” If they are, then it wouldn’t be surprising for astronomers to find planets that are slightly smaller and slightly cooler — in short, more Earth-like — as well.

Charbonneau’s group isn’t the only one looking. An international consortium of observatories just announced the discovery of several other super-Earths around Sun-like stars, though these new planets are far too hot to sustain life and too far away to be able to study. Separately, NASA’s Kepler Mission will present the first results of its planet search at the American Astronomical Society meeting in Washington in January. “[The Kepler team] has already submitted 28 scientific papers based on 43 days of data or less,” says MIT planet theorist Sara Seager. “It’s going to be a big year for planets.”

By Michael D. Lemonick Wednesday, Dec. 16, 2009

Read more: http://www.time.com/time/health/article/0,8599,1947868,00.html#ixzz1U1XEQc4w

One of astronomy’s longest-running “missing persons” investigations has concluded: astronomers have found molecular oxygen in space.

While single atoms of oxygen have been found alone or incorporated into other molecules, the oxygen molecule – the one we breathe – had never been seen.

The Herschel space telescope spotted the molecules in a star-forming region in the constellation of Orion.

The find will be published in the Astrophysical Journal.

Oxygen is the third most abundant element in the cosmos, after hydrogen and helium. Its molecular form, with two atoms joined by a double bond, makes life on Earth possible – but this form had never definitively been seen in space.

A 2007 effort from the Swedish Odin telescope, published in the journal Astronomy and Astrophysics, claimed a discovery of oxygen in a nearby star-forming region, but the discovery could not be independently confirmed.

One possible location for the missing oxygen is locked onto dust grains and incorporated into water ice.

The team chose a star-forming region in the constellation Orion, believing that oxygen would be “baked off” from the ice and dust in a warmer, more turbulent part of space.

Instruments on the Herschel telescope, sensitive to infrared light, picked up small signatures of the elusive molecular oxygen.

“This explains where some of the oxygen might be hiding,” said Paul Goldsmith, principal investigator on the Herschel Oxygen Project.

“But we didn’t find large amounts of it, and still don’t understand what is so special about the spots where we find it. The Universe still holds many secrets.”

2 August 2011

http://www.bbc.co.uk/news/science-environment-14372708#

http://www.time.com/time/health/article/0,8599,2049641,00.html?xid=rss-mostpopular - TimeScience

Mystery Planet: Is a Rogue Giant Orbiting Our Sun? By Michael D. Lemonick Wednesday, Feb. 16, 2011

The quest for Planet X always starts out with celestial objects behaving badly. Astronomers notice that a known planet, or a bunch of comets, begin moving in ways Newton’s laws of motion can’t explain. They propose that it’s caused by the gravity of something massive and still undiscovered lurking out in the Solar System, and they head to their telescopes to search for it.

Most often it’s all a big mistake; the unexplained motion turns out to be just an incorrect measurement. (The great exception concerned Neptune, spotted in 1846 after observers noticed Uranus wandering from its predicted path). So when a pair of University of Louisiana astronomers, writing in the journal Icarus, advanced their recent theory about a new mystery planet in our solar system — and a very, very big one — their colleagues mostly just listened politely, then went back to work.(See TIME’s photoessay “Amazing Photos of the Sun.”)

They reckoned without the Web, though. A few days ago, the British Independent ran an article about the possible planet, and suddenly the idea went viral. The likely reason the story caught fire: a key sentence that read “But scientists now believe the proof of its existence has already been gathered by a NASA space telescope, WISE, and is just waiting to be analysed.”

That’s just close enough to the truth to be dangerous, something that John Matese, co-author of the Icarus paper, admits — sort of. “What we’re really saying,” he explains, “is that there’s suggestive evidence there might be something out there.” And if a new planet exists — something Matese is emphatically not claiming at this point — then the Wide-field Infrared Survey Explorer (WISE) satellite should already have an image of it stored somewhere in its enormous database.

How suggestive the evidence actually is, though, depends on whom you ask. If you ask Ned Wright, a UCLA astrophysicist and WISE principal investigator, he’ll tell you, “It’s really kind of flimsy. It’s there, but they don’t have super data.”

The argument Matese and his colleague Dan Whitmire have been making since the late 1990s is that some comets seem to be moving in toward the Sun from a skewed direction. They start out in the Oort Cloud, a vast collection of perhaps trillions of small, icy chunks that hover at the very outer edges of the Solar System. Every so often, a passing star or the tidal effect of the Milky Way itself jostles the cloud, sending some of the chunks sunward to light up the night sky as comets.(See The Hubble Telescope’s Greatest Hits.)

When Matese and Whitmire analyzed the orbits of these Oort Cloud comets, about 20% of them seemed to come not from the random directions you’d expect, but from a narrower section of sky. This might suggest a giant planet, at least the size of Jupiter and maybe up to four times as big. Its size would not be its only remarkable feature; it’s remote orbit would be another — a tidy trillion miles from the Sun, or more than a thousand times more distant than Pluto. “This is not a crazy idea” says Bad Astronomy blogger Phil Plait. And indeed, WISE project scientist Davy Kirkpatrick went so far as to propose a name for the possible new world: Tyche, for the Greek goddess of good fortune.

That might have been a subtle dig, though. In Greek mythology, Tyche was usually invoked along with Nemesis, the goddess of bad luck. Nemesis was also the name given to a mystery object that was in vogue in the 1980s, shortly after it was generally agreed that a comet might have killed the dinosaurs. A few astronomers thought they could see even more of a dino-cosmos link — a pattern of mass extinctions occurring like clockwork in the geologic record. Their explanation: a faint, far-off companion star to the Sun was sending down a rain of comets when it reached just the right point in its orbit. That sounds an awful lot like the current thinking about Tyche’s possible influence — and thus the possible dig.See TIME’s graphic: “Where Things Are Just Right for Life.”

After a brief flurry of interest, most astronomers decided the evidence of Nemesis was pretty flimsy, and the idea went away. So did the long-ago speculation about another huge putative planet, one that was said to be messing with Neptune’s orbit; astronomers who went looking for that version of Planet X in the 1920s could only scare up puny Pluto — whose influence on schoolchildren is huge, but which doesn’t affect Neptune a whit (the original evidence for Neptune’s orbital anomalies turned out to be wrong). And Pluto itself has recently lost its planetary distinction and been busted down to dwarf planet. Then too there was the mystery planet said to be orbiting Barnard’s Star, detected via wobbles in the star’s motion by Swarthmore astronomer Peter Van de Kamp in the 1960s.. Turns out that the wobbles were caused by the removal, cleaning and replacement of his telescope’s mirror. No planet there either.

So while the latest version of Planet X could certainly exist in theory, it’s way too early to start rewriting the textbooks. The evidence isn’t even strong enough to have triggered an active search for Tyche; it’s only because WISE happens to be surveying the heavens anyway that it could be found at all. If Tyche really is out there, says Wright, “we might be able to tell you something in a year or two.”

Read more: http://www.time.com/time/health/article/0,8599,2049641,00.html#ixzz1ShkCi0dj