Astronomers have found the second smallest exoplanet, HD156668b, a so-called “super-Earth” that’s just four times the mass of the Earth. With an orbit of just 4.6 days (compare that to Mercury’s 88-day orbit), this planet would not be a nice place for life. Yet, that such a small planet can be duly reported at AAS amid shoulder shrugging by the scientists and press alike shows just how far the exoplanet field has come in a few years.

The week of AAS began with discoveries from Kepler, and its search for transiting planets. And now it’s ending (or at least my blog posts are ending) with this discovery, which comes from astronomers using the twin 10-metre Keck telescopes in Hawaii to look for the wobble caused by the planet on its parent star.

The two bookends show not only the race between the space-based and ground-based observatories, but also the different approaches they use: transits, which give planet diameter, and the wobble searches, which give mass.

But as much as the two groups are competing, they also need each other. Not just to confirm planets — there are many false positives out there — but also to get both size and mass so that density can be calculated. Density, it turns out, is the crucial measurement that will tell us whether these distant worlds are puffed up and full of gas, buoyant and watery, or hard as rock. For now, all we know about HD156668b is that it is damn hot.

Image: L. Calcada

It’s no surprise that people do the best job conceptualizing the spatial and temporal scales of the everyday — the length of a car; the length of a work day — and have a much harder time with extreme scales, like the age of the universe.

But people are slightly worse at understanding extreme scales of time than space, according to Aaron Price of Tufts University, who gave a neat astronomy education talk on Wednesday.

In a survey of more than 400 undergraduates, Price found that students consistently underestimated big time scales and overestimated the duration of the quickest phenomena — worse than they did for spatial scales. But in both situations, Price says, the mind is trying to condense the two extremes towards something more manageable in the middle — which suggests that mental number lines are inherently logarithmic.

Anyone want some time on a really big telescope? Gemini, the observatory with twin 8-metre telescopes in Hawaii and Chile, could use the money.

In November, the UK cemented its decision to withdraw as a 25% partner from the six-nation observatory by the end of 2012. This is just one of many cuts Britain is making as the STFC tries to climb out of budget hole. The UK had flirted with maintaining some time in the northern hemisphere (since it already has access to ESO telescopes in Chile), but the Gemini board nixed that.

At a town hall meeting at AAS, Gemini director Doug Simons discussed his plans to carry on. Instead of dealing with a sudden drop at the end of 2012, the observatory is cutting budgets by 7% to 10% each of the next three years.

“2010 may be the biggest budget that we have for a very long time,” he said. “I do not expect Gemini to be the same observatory at the end of this process.”

He says the most savings will come from altering the science operations – which may diminish the custom ways in which the observatory manages its science queue.

But Simons is still hopeful that Gemini, which provides the vast majority of large-diameter telescope time for US astronomers through NOAO, will remain relevant. Five new instruments are nearly finished, and Simons wants to keep its unique capabilities in the infrared.

The astronomers heard what they wanted to hear. Even as NASA sits in limbo, awaiting a presidential decision on the future of the human spaceflight programme, NASA Administrator Charles Bolden told hundreds of astronomers that their budget would be sacrosanct. “The future of human spaceflight will not be paid out of the hide of the science budget,” said Bolden on Tuesday in a jam-packed NASA town hall at AAS.

But whether Bolden can deliver on that promise won’t be revealed until February, when the Administration releases its fiscal 2011 budget, and also when President Barack Obama delivers his state of the union address. Rumor has it that the speech will reference NASA’s future, and will contain Obama’s long-awaited decision, one that was supposed to come in the wake of a blue-ribbon report chaired by Norman Augustine last summer. That report laid out the grim options for human spaceflight at NASA, a programme that was perhaps $3 billion a year short of returning to the moon. While Bolden claimed not to know anything about Obama’s impending decision, it is not hard to read the tea leaves. Many of the Augustine report options favor jettisoning the Ares I rocket in favor of commercial providers of rockets. NASA would then focus on a heavy lift vehicle, though it might take a different guise than the current Ares V.

In the absence of hard facts, Bolden stuck to the role of cheerleader, telling war stories about his delivery of Hubble Space Telescope to orbit as a shuttle pilot. He exhorted the scientists to focus on outreach and education, almost exactly the opposite of the approach of former Administrator Mike Griffin, who at a conference two years ago dismissed outreach as not being part of NASA’s core mission. Bolden also told the audience that they better get used to international partners and collaborations. He mentioned how he was encouraging JAXA, the Japanese space agency, to turn a space station cargo rocket into something that could ferry people.

But a reporter pressed him: Will the US have a human-rated rocket by 2020? Bolden said he was confident Obama wouldn’t end human spaceflight. Bolden said he would be shocked if the US didn’t have something by then. Later, Bolden said he was shocked the US didn’t have the capability already. If in 1980, “you had told me that we would not be back on the moon today,” he said, “I would have told you you were smoking dope.”

Bolden is all heart — an emotional, sincere and passionate speaker. He sometimes chokes up — something that belies his past as a Marine Corps attack pilot. The contrasts between him and the bluntly logical Griffin are impossible to ignore. But no amount of positive thinking will change the reality that NASA is in a pickle. Even if the science budget isn’t robbed, it could be starved: many predict flat budgets for the agency next year, and there is still time for the $4.5 billion James Webb Space Telescope, due for launch in 2014, to continue to eat up the astrophysics budget.

Last year was great for NASA astrophysics, with the launches of Kepler and WISE and Herschel, and the continued success of Fermi. By contrast, when Bolden detailed the years ahead for NASA, the only mission he could point to in 2010 was SOFIA, a 747 with a puncture wound in its side that contains an infrared telescope. It is set to begin science flights in 2010, but its budget has also ballooned over the years and many say the mission will be out-performed by Herschel.

Yet Bolden, ever the optimist, pointed out that, relative to the deeper past, times have never been better. In 1990, astrophysicists could gather data from five missions in operation. In 2000, there were nine. In 2010, he said, there are 15.

UPDATE: I have a story on a slightly different aspect of the Kepler results — asteroseismology — up on the main Nature News site.

So the Kepler mission announced its first exoplanetary discoveries today: four huge planets bigger than Jupiter, and one about the size of Neptune, all hotly hugging their parent stars in tight orbits of a few days. There were a few neat tidbits that Kepler PI Bill Borucki offered up about the finds in talks today. One of the hot Jupiters has a density as fluffy as styrofoam. Some of them are hotter than molten lead. Looking at them is like looking into a “blast furnace”, says Borucki. Overall, the discoveries serve notice: Kepler is in action. The finds themselves? Not so special really. Of the 415 known exoplanets, the vast majority are hot Jupiters.

One interesting angle in the discoveries, however, is the gap between the four Jupiters and the one Neptune. Neptune is just 17 times the mass of Earth; Jupiter is more than 300 times the Earth’s mass. Why didn’t Kepler find anything in between? Dimitar Sasselov, a Kepler co-investigator from Harvard, says it is because the gap is real. There is a cutoff mass, bigger than Neptune, where a runaway accumulation process occurs during planetary formation. Anything bigger than, say, 30 Earth masses, will eat up any gas it can find in a solar disk and become a big hulking Jupiter. Smaller than the cut off, and it will stay Neptune-like. UC Santa Cruz’s Greg Laughlin was pointing this out a year and a half ago on his terrific blog — that this cutoff mass was expected. But Kepler — one of the first instruments to be capable of reaching low mass planets without selection effects — is starting to show that the “Neptune Gap” is real.

Image: NASA

Howdy folks: It’s a frigid morning here in Washington DC, the site for this year’s American Astronomical Society meeting, where 3,500 attendees are expected to pack into the Marriott Wardman Park hotel. This is where I live and work, so instead of tumbling down to the conference from a warm hotel room, I had a lung-scouring walk to the hotel against the wind in 20 degree weather. On the flip side, I know where the bars and restaurants are. Happy to provide advice. After an opening talk from Kepler PI Bill Borucki — stay tuned for the latest discoveries from this mission that could very well bag the first exo-Earth — the conference is underway.

Image: Rob Shenk via Flickr

“Do you realize that we are up to our 11th year of parties?” says Gina Brissenden, who was hemmed within a scrum of astronomers on the patio, but utterly pleased about it. Hundreds of astronomers had turned out to the Rhythm Lounge in Long Beach, and were rapidly starting to get their groove on (aided and abetted by the ‘Galileo 400’ drink special). What began as an impromptu afterparty in a hotel room, organized by Gina, has since turned into a biannual bacchanalia for the young, the old; for those inclined to dance, and for those who you wish weren’t so inclined.

Above the dance floor, an endless short film loop was projected — about the discovery of the period-luminosity function for Cepheid variables. I was pretty sure that it was entirely incidental, however, when the DJ played the Beastie Boys song, “Intergalactic.”

They didn’t need any help on the dance floor anyway. Astronomers are an interesting bunch. Individualists, each and every one of them, but as a fellow observer remarked to me: she had never seen a pack of people devote themselves so quickly and diligently to the collective task of getting down. The dance floor was a black hole, and at one point, there were demands that astronaut John Grunsfeld occupy its singularity (that he might be more concerned about fixing the Hubble space telescope was not an issue). “I heard there were astronomers in the house,” says Kevin Marvel, AAS executive officer, revving up the crowd from the DJ booth. With just a hint of cautionary worry, he implores them: “Don’t go supernova.”

Allright folks, it’s been a pleasure, and it’s time for me to catch a plane back to Washington, DC. And in case you were wondering what’s in a ‘Galileo 400’, it’s vodka, peach schnapps, and Sprite.

Some 70% of the stars in the galaxy are M dwarfs, and so exoplanet surveys will be targeting these relatively cool, small stars. But the habitable zone for Earth-like planets in these systems will be at least five times closer to the M dwarf than the Earth is to the sun. That keeps the planet warm, but also subjects it to the star’s capricious behavior. “They flare as powerfully or even more so than the Sun,” says Lucianne Walkowicz, of the University of California at Berkeley, who gauged the effects of an M dwarf flare on planetary habitability in an AAS poster session. “People assumed that this would just sterilize the planet.”

Lucianne modeled a 4-hour flare — a classic one that astronomers had observed carefully on a nearby M dwarf -and calculated its effects on an Earth-like planet, with an Earth-like atmosphere, orbiting at 0.16 astronomical units – six times closer than the Earth is to the Sun. She measured the effect of the flare — which for our Sun, can rise up to heights 50 times the diameter of the Earth — on temperature, ozone, UV flux and water vapour.

Turns out, the flare wasn’t that big of a deal. Temperatures only changed a tenth of a degree. Most of the energy of the flare went into the upper atmosphere where it broke down ozone. The fraction of the radiation that did make it through, she says, is less than you’d get on a sunny day walking around Earth.

The 10-foot-tall tub, full of 500 gallons of liquid helium, dangled underneath a high-altitude balloon over the skies of Texas for just a few hours. But the bucket came back with a big mystery.

In the 2006 flight, Alan Kogut of Goddard Space Flight Center in Greenbelt, Maryland and his colleagues were aiming to use the seven super-cooled antennae in the tub to hear the faint, relic radio signal of ‘first light’, the epoch a few hundred million years after the Big Bang when big lumbering stars ruled the roost.

But instead, they heard a really loud radio hiss. “To our surprise, we found an unexplained radio static… that fills the early universe and is currently unexplained,” says Kogut, speaking at a press briefing on Wednesday.

Astronomers, using balloons and satellites, have mapped the cosmic microwave background — the faint, 2.7 degree Kelvin fabric created by the Big Bang itself — at slightly shorter wavelengths, and ground based astronomers have conducted radio survey at longer wavelengths. But Kogut says his group was the first to notice something in this strange, in-between regime.

In four papers submitted to the Astrophysical Journal, they are careful to rule out the possibility that the radio background signal came from the Milky Way. It’s much bigger than the total signal from all known radio galaxies, and it’s way too big to have anything to do with the first light stars (they would have looked for the radio signal associated with hot gas near these first stars).

But they were reluctant to speculate what it could be. “We really don’t know,” Kogut says. The balloon experiment didn’t have much resolving power to pinpoint individual sources of the static, and it only looked at a few frequencies. Pressed for ideas, Kogut said that it could be radio radiation from the collapse of these huge, first stars into black holes. There would have hundreds, if not thousands, of these first stars in each proto-galaxy, he says, and their collective death rattle, so many of them across the sky, just might appear as a background signal to his relatively crude balloon instrument. “We may have accidentally backed into the epoch we were interested in.” It would be the first signal from one of the deepest, and heretofore darkest, reaches of the universe.

I was just pleased to see yet again that simple balloon experiments can have a potentially big impact. At $4 million, the experiment, called ARCADE, is another example of how cost effective balloons can be.

In just a matter of months, the Fermi gamma ray observatory since its launch has found dozens of new pulsars — spinning, magnetized remnants of supernovae — that emit a flashing signal in the gamma-ray part of the spectrum only. This new class of pulsar has revolutionized scientists’ view of its general structure: Early in a pulsar’s lifetime, it blasts a broad gamma-ray signal rather than a narrow polar one, as was previously thought. The findings, announced Tuesday at AAS, also includes a club within a club: a subclass of the gamma-ray-only pulsars that flash exceptionally quickly, an indication that they are revving up as they partially devour their dying partners in binary star systems.

The supernovae that come at the end of a star’s life cast off much of a star’s mass, but what’s left collapses to form a neutron star, a fantastically dense object just shy of being a black hole. The spinning magnetic fields produce a narrow cone of radio waves that jet out from the poles. Some 1,800 radio pulsars have been discovered this way.

But there were only a handful that also produced gamma-rays, and these signals were also thought to emanate from the poles. Fermi has boosted the number of known gamma-ray pulsars up to 38, including 13 that lack a radio signal altogether — an indication that the gamma rays can’t be coming from the poles. The results, says mission scientist Roger Romani of Stanford University, “have put the nail in the coffin of the polar cap model.”

He is still working out the mechanisms and geometries by which the intense magnetic fields create the powerful gamma-ray signal, which is expected to arise only in the first million years or so of the pulsar’s life. His models show a trumpet-like bell shape that emerges and sweeps across the pulsar’s face, higher in its magnetosphere, rather than only at the poles. “It means the gamma rays are being beamed widely across the sky,” he says.

The newest phenomenon — seven so-called ‘millisecond’ pulsars that flash hundreds of times faster than normal — has led mission scientist Alice Harding, of Goddard Space Flight Center, to envision how this happens. In binary stars systems — relatively common in the universe — one may die first and become a pulsar. Before the second star explodes, it expands, and its excess material can be sucked into the spinning maw of the pulsar thereby speeding it up. “These guys must have strong stomachs,” Harding says. That’s the scenario pictured here. After the jump, Fermi’s all sky map, and the new gamma-ray pulsars.

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