Seeking another Earth, by the numbers

December 6, 2013 by Arthur Hirsch, The Baltimore Sun

In a room with concrete block walls from which he can barely see the sky, Drake Deming explores the heavens.

Several days a week he can be found in his office at the University of Maryland, College Park, surrounded by three computer screens, analyzing information about planets outside our solar system. In these remote regions - no closer than four - roughly 24 trillion miles - and as far as hundreds of light years away - scientists hope one day to find an Earth-like world capable of supporting life.

A professor of astronomy and former senior scientist at NASA's Goddard Space Flight Center, Deming is among the leading researchers of extrasolar planets, or exoplanets - entities made of rock, iron or chiefly gas, orbiting their own suns. Last month he weighed in with his latest contribution to the field's literature: a review in the journal Nature considering work done by two research groups on Kepler-78b, an exoplanet named for the Kepler Space Telescope, through which it was observed.

"That's an important planet," said Deming, now in his third year at College Park, where he taught in the late 1970s before spending 30 years with NASA.

His Nature review noted Kepler-78b as significant for its similarities to Earth - the closest in size among the more than 1,000 extrasolar planets yet found, according to NASA. With 80 percent more mass and a 20 percent larger radius, Kepler-78b is "a virtual twin of Earth by astronomical standards," Deming wrote.

The planet, some 400 light years away in the constellation Cygnus, appears from its density to be made of rock and iron, like the Earth. But unlike the Earth, which is about 93 million miles from the sun, Kepler-78b is less than a million miles from its sun.

That makes for hellish conditions: from 3,500 to 5,000 degrees Fahrenheit, with a surface likely consisting of molten rock. Hardly a conducive environment for the development of any known life form, but its mere existence suggests the likelihood of similar planets out there, perhaps not all so close to their suns, or orbiting cooler stars, Deming said.

In looking for other "Earths," planet size matters, Deming said. A life-sustaining planet would be massive enough to maintain an atmosphere, yet small enough so that its gravitational pull would not gather around it a massive gaseous cloak, turning it into a "gas giant" like Jupiter and Saturn.

For these reasons, Deming wrote, Kepler-78b "foreshadows leaps forward in the search for life beyond the Solar System."

Deming knows about leaps forward in these matters, as he's been there himself.

In 2005, when he was with the Goddard Space Flight Center in Greenbelt, Deming led one of two research teams announcing simultaneously that their separate investigations resulted in the first confirmed direct observation of two .

The teams from Goddard and the Harvard-Smithsonian Center for Astrophysics each analyzed information gathered by the Spitzer Space Telescope, launched in 2003 and designed to detect signals in the infrared spectrum.

The significance of the finding is hard for a layman to discern in the three-page article detailing calculations that confirmed the infrared radiation of the planet - some 150 light years away in the constellation Pegasus - as it passed behind its star.

An exoplanet scientist at the University of California, Berkeley, who was not a member of either team, put it more dramatically. In an interview with The New York Times, Geoffrey W. Marcy called the findings "the stuff of history books. ... With this result, we are closer to understanding our own human roots, chemically, among the stars."

Inclined to speak in more measured terms, Deming acknowledged that he's less taken with the grand meaning of it all than with data analysis. His astronomical pursuit is largely a mathematical project.

It's well-suited to Deming, 65, who did his undergraduate degree in mathematics at the University of Chicago before switching to astronomy for his doctorate at the University of Illinois at Urbana-Champaign. Pure math, he said, seemed too "abstract."

Still, the discipline of a boy who grew up in Indiana relishing his math studies serves him well in work involving deep dives into oceans of numbers representing the observations of space and land-based telescopes. In the case of the infrared measurements, a Deming specialty, these are rows of numbers of photons, sent by the telescope.

Deming's challenge is to figure how to analyze the numbers for a reliable planet profile. How to distinguish the planet's signal from the much stronger one from the star? How to correct for distortion from the telescope itself? Is that the infrared light signature of a particular molecule in the planet atmosphere, or could something else account for the numerical pattern?

Astronomer Heather A. Knutson, who has collaborated with Deming, said he combines meticulous attention to detail with the ability to see how the small stuff fits into the larger picture, or how it doesn't.

"His reputation in the field is that he's someone very careful," said Knutson, a Johns Hopkins University alumna who's now an assistant professor of planetary science at the California Institute of Technology. "He's sort of an anchor for some of us who run off and think we see something. If Drake says he sees it, you really believe it."

She said Deming refined a method of analyzing infrared information from the Hubble Space Telescope that has become prevalent among astronomers trying to correct for distortions created by the telescope. Two papers now in review for Nature use this approach, she said.

Peter R. McCullough, an associate astronomer at Hopkins' Space Telescope Science Institute, which runs the science side of the Hubble mission, said Deming likes to "get dirt under his fingernails digging at the little bits of information" coming from telescopes, including Hubble.

Deming said he usually has six or eight research projects going at once. Among his next projects will be examining the atmospheres of exoplanets roughly the size of Neptune, a "gas giant" considerably smaller than the Jupiter-like worlds he's been exploring for years, although still much larger than the Earth.

"Small planets are always more interesting; they're more like Earth," Deming said. He's happy analyzing uninhabitable exoplanets, he said, even if he knows finding an Earth look-alike is the "Holy Grail" in this field.

"That would be wonderful," he said.

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2.5 / 5 (4) Dec 06, 2013
Great article. Well-written, too. Since they started discovering dozens (with 1000's of potential) extrasolar planets, I've thought that this should be in mainstream news more, but it stays pretty locked up in science news only. The fact that extrasolar planets have become the rule, instead of the exception, is of hugely great importance.
2.6 / 5 (5) Dec 07, 2013
Earth is a one-of-a-kind planet. Telling people that there's another Earth out there (even though we haven't found it) is just going to make them care even less about this one.
3.7 / 5 (3) Dec 07, 2013
I guess Vsha lives in a universe where there's another Earth right next door. Sorry to break it to ya, but Star Trek isn't real.
2 / 5 (2) Dec 07, 2013
Sinister1811: And how do you KNOW there isn't another Earth "right next door"? If there was one orbiting Alpha Centauri A or B we probably couldn't detect it with current technology. It would be too far from the star and too small for radial velocity detection, the system's plane is tilted to our view, so probably no transits, and we certainly couldn't detect it visually.

I'll agree that it's unlikely that we would find one we could live on without technology, but how many people today could survive on Earth without some form of technology? A world with breathable air, drinkable water, and at least non-toxic, if not edible, life is still quite possible next door.
3.7 / 5 (3) Dec 08, 2013
@nkalanga We haven't detected it. That's the point, so we don't know if there is. And even if there was, how would we get to it? We don't have a way to travel at the speed of light or even close. It would take us forever.

Some people can survive without modern technology, like certain tribes which did for thousands of years. But living on a planet we didn't evolve on could be even harder. There'd still be one thing that isn't right for us (i.e. gravity, atmosphere, temperature or whatever). And what if the life there is different?
3.7 / 5 (3) Dec 08, 2013
I didn't say we could get too it, just that the fact we haven't detected it doesn't mean it isn't there. "Lack of evidence isn't evidence of lack (of existence)".

As for getting there, no, we couldn't, at least today. Gravity and atmosphere are as likely to be acceptable as not, especially since you specified "Earth-like", which includes similar mass and density. Humans live everywhere from the Arabian Desert to the Arctic, so temperature isn't an issue, and "different life" wouldn't be a problem. We can always grow our own food, in greenhouses if needed.

And, yes, I realize that primitive tribes can survive without technology, that's why why I asked "how many people today could survive on Earth without?". The primitive tribes wouldn't be building starships, and the people who would generally don't know how to live without their machines.

5 / 5 (1) Dec 09, 2013
1 -
Telling people that there's another Earth out there (even though we haven't found it) is just going to make them care even less about this one

2 -
it's unlikely that we would find one we could live on

3 -
And even if there was, how would we get to it?

Good points.

1-There are things we can learn by observing planets similar to Earth, yet not exactly the same, even if only by telescope, which will teach us lessons about Earth. There are questions we need to answer about the Earth, which may be crucial to our survival, that might be studied in no other way (like ice ages?).

2-Yeah, not 'near us' at least.

3-As it stands, it's certainly beyond our reach, and it will be the pinnacle of all human achievement up to that point, if or when we eventually try to do it. The resources it will take to attempt such an adventure are staggering; a task of planetary scale. It is difficult enough just to keep people on Antarctica right now.
1 / 5 (1) Dec 10, 2013
By the time we're ready to try interstellar colonization, we probably won't need a "nice" planet. We'll have enough experience in artificial habitats that we'll take our home with us. Stock up the space station with enough fuel for the journey, including heat and lights, and go. Grow your food as you travel. So it takes two or three generations. It wouldn't be any different than orbiting the Sun to people born and raised on a station. If the destination had raw materials they could resupply, expand the station, build new stations, and eventually send stations to the next star.

Meantime, those who like to have a planet under foot (including me) would stay home. "Home" might be Mars or Mercury, but it would still be a planet. Mars has at least one advantage over a station: it won't lose its air nearly as fast. In case of a leak one can always repressurize.
5 / 5 (1) Dec 10, 2013
By the time we're ready to try interstellar colonization, we probably won't need a "nice" planet.

Yes, I agree. The infrastructure and engineering we need before we get to that point are extensive. I think it is reasonable to assume that we will have multiple off-planet colonies before we have all the other pieces we will need in order to attempt interstellar travel.

As for storage of consumable resources on an interstellar journey, you could harvest hydrogen, oxygen, carbon, etc. from the Kuiper belt on your way out of the solar system. You could store them outside the spacecraft in big frozen blocks. No need for tanks. And the materials would help shield you from radiation and micrometeorites.

A truely revolutionary propulsion system is needed first though. I don't think any mechanical structure as complex as a spacecraft could stay operational for a journey of hundreds of years, not to mention thousands. Logistics are a bitch.
2.5 / 5 (2) Dec 11, 2013
GSwift7: That's why I assumed the first "starship" would be an entire colony station. They'd have the factories to make anything they needed, up to duplicating the station itself, as long as the raw materials were available. Repair parts wouldn't be a problem, and since the journey would be one-way, and take several generations, they'd be planning on colonizing the new system from the start.

In my opinion, the most likely group to try it first would be a colony already in the Kuiper Belt. The most likely business model out there would be volatile mining, trading for metals from the inner system. The Sun isn't much use that far out, so they would have to be fully self-sufficient in energy and food. As you said, many of the volatiles could be stored as ices, and used as a debris shield, so they could just stock up and go whenever they were ready.
5 / 5 (1) Dec 11, 2013
GSwift7: That's why I assumed the first "starship" would be an entire colony station. They'd have the factories to make anything they needed,

That's one way to do it, but probably not the best.

Far better to plan on the ship failing along the way, and just focus on making it small, light, and fast. The trick is that propulsion technology here on Earth will get better over time. That should allow us to build better, faster ships and send them on auto-pilot, loaded with supplies, to catch up with the colony. At that point they move into the new ship, canabalize what's left of the old one, and abandon it. This would need to be repeated many times, but would provide the fastest and safest trip.

Some would ask, 'why not just wait and send the people with the faster ship', but with the relay system they keep getting fresh supplies and you keep the mass of each ship as low as possible, which makes the journey as fast as possible. It's a monumental task, no matter how you do it.
3 / 5 (2) Dec 11, 2013
I'm glad to see people and enthusiasts in general (myself included) sobering to the fact that we're not going to find "Star Trek" out there. It's highly unlikely we'll find any other intelligent species in our galaxy at all, and if we do find something else out there like us by the time we find it we'll be so far advanced of where we are now it's meaningless to talk about what it might mean to us...because, well we won't even BE "us" anymore....
1 / 5 (1) Dec 12, 2013
GSwift7: IF we can safely assume propulsion will improve steadily that is a good option. On the other hand, it's possible that we'll hit a practical limit. One of those is shielding. Near-light speed is impractical, as far as current physics knows, simply because the same relativistic effects that benefit travel time also dramatically increase the energy of both radiation and matter impacting the ship. At some point a material shield simply couldn't protect the ship.

Also, as long as we're limited to fusion, there is a limit to the speed achievable with a practical mass ratio. We also have to carry fuel to slow down, which has to be accelerated at the start.

I wouldn't be surprised if both methods are tried. Stationers might prefer the slow way, like a turtle, as they take their homes with them. Planet-siders might want to get there faster, so use your method, or perfect hibernation.
2 / 5 (2) Dec 12, 2013
Modernmystic: I'd be more worried that whomever we meet is so far ahead of US that they wouldn't want to talk - or recognize us as intelligent.

"Quick, honey, the cockroaches have invented spaceships! Where's the bug spray?"
not rated yet Dec 12, 2013
On the other hand, it's possible that we'll hit a practical limit. One of those is shielding

That's the one everyone thinks of first, because we all think in terms of atmospheric flight. You've really got to have adequate radiation shielding before you can attempt any interstellar travel, so that'll be a given, or the whole thing is a non-starter. Physical shielding probably isn't that big of a deal. The trade-off between the risk and the weight probably means minimal physical armor.

The fundamental limit that will constrain our propulsion systems the most (in my opinion) is thermodynamics. I think our ability to provide large thrust over long time periods will exceede our ability to deal with waste heat. That means we will have to limit the throttle on our ship to the point where the interior of the spaceship doesn't become too hot. It isn't easy to build electronics or life support systems that will work for long periods of time at high ambient temperatures.
5 / 5 (1) Dec 12, 2013
Travel to another solar system is way off in the future though. We have plenty of exploration and colonization opportunities right here around sol. It will probably take centuries for us to develop the places we have available here, such as the moon, Mars, the main belt, Jupiter and Saturn's moons, maybe the Kuiper belt, etc.

And unless there is a planet or moon worth traveling to, then it doesn't matter whether we can do it or not. By the time our technology makes it possible, we will know whether there is any desirable target within range, but I would place the odds that such a place exists within a few LY at less than 50%.

Oddly enough, it might be medical science, rather than physics, that will be the key to bridging the gap between stars. If humans can live hundreds of years, then interstellar travel becomes much more realistic.
1 / 5 (2) Dec 12, 2013
There is a design for interstellar travel that solves the heat problem, at least as far as the crew is concerned. The idea is to pull the habitat section, rather than pushing it, by putting the engines in front. The best drawing I've seen showed the habitat as a ring, with the tethered engines firing through the center of the ring. Besides minimizing heat transfer, as long as the ring is larger in diameter than the exhaust, it also reduces weight, as a set of cables weighs less than a thrust-support beam. Turning is more difficult, as one can't just rotate the entire craft end-for-end, but that isn't a problem for a starship. There's plenty of time for turnover, and the engines can always be reeled into the center of the ring long enough to make the turn.
5 / 5 (1) Dec 13, 2013
that solves the heat problem, at least as far as the crew is concerned.

Yeah, the crew isn't the problem. You've got to keep the engines and fuel system working, and you don't really want to have any kind of complex system with high speed moving parts or high pressure fluids, because it would be bound to fail too often (seals, joints, bearings, etc). You really need something like a meta-material that only allows heat to flow in one direction, so you can radiate without any moving parts, or evaporate some high melting point metal like copper (but any consumed resource is undesirable).

I've seen articles that ask the question of why the galaxy isn't loaded with interstellar travelers, if we aren't the only intelligent life. Who knows, maybe the technical challenges of interstellar travel are tougher than we realize.

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