55 Cancri e is an extrasolar planet with an identity crisis. After its opening in 2004 on a very close orbit a star 40 light years from us, the astronomers named the planet “super-earths”. Being just 8 times more mass and 2 times the size than our world, 55 Cancri e is in the category Welterweight, limit of which varies between gas giants and terrestrial planets. Nothing like that in our Solar system has not yet been found.
For years scientists believed the best explanation for its Middleweight presence of a solid core the size of Earth, surrounded by a dense vaporous atmosphere. However, the new map of the planet — the first of its kind for such a small little world — suggests that 55 Cancri e may not have the atmosphere and to be airless, half molten ball of slag.
For the month of observation (clear time) on the infrared space telescope NASA Spitzer, a team led by Brice-Olivier Demory from the University of Cambridge roughly sketched map heat “phase curve” of the planet — the variation of its brightness as it moves around the star. The planet is tidal locked with its star, i.e. the world rotates once around its axis per orbit, therefore, one hemisphere is forever bathed in sunshine and the other lies in darkness. Measurements showed that the night side of the planet should show a ruddy glow, as the temperature of it exceeds 1000 degrees Celsius — like a blast furnace. But on the daytime side of 55 Cancri e temperature twice, and the hot spot shifted to the East from the expected position directly under the star. The results of the scientists were published in Nature.
Very noticeable difference between the temperatures of day and night sides to indicate the lack of on 55 Cancri visible atmosphere, as the winds should shift heat between the two hemispheres. But shifted hot spot dayside suggests that something is still redistributes heat, destroying him just a little further to the East, away from point “under the star” on the planet’s surface, where the light from the star most intensively.
“We first used remote sensing to map the distribution of temperature in super-earths, says study co-author Nikku Madhusudhan of Cambridge University. It was a great result, but it is very peculiar: one piece of data suggests that the planet may not be the atmosphere, the other part says that something must flow”.
And this “something”, according to Demory most likely molten rock. “Hot spot 55 Cancri e, if it had no atmosphere, means that we see bare solid planet with a current on its surface with lava, which partially distributes the heat on the day side,” says Demory. Day side should be covered with water circulating lava, and the easiest and less viscous lava should flow in the direction of the night side, where it cools, and crystallizes naturally accumulated in the form of solid rock.
Otherwise, he says, the planet must be the atmosphere, although very strange — with the clouds of evaporated rock. Powerful winds moved the clouds to the East along with the rotation of the planet, shifting hot spots, but also stone pairs would quickly cool and fall to the surface upon reaching the night side.
“It’s hard to find the mixture components that would behave this way, says Demory. — We need something cheerful that would be gaseous on the daytime side, but condense on the night side. We were looking for, but have not yet found any substance that meets these criteria, so we like the option of lava, until we confirm return”.
“It’s very interesting that we have a phase curve of super-earths, says Sara Seager, astronomer and planetary scientists at mit. — This shows that astronomers are doing everything possible to optimize methods for working with smaller and smaller planets, and what the nature once again gave us a curious planet, orbiting close to bright stars.”
But not everyone is convinced that 55 Cancri e is a lava world, or that the phase curve of the planet from Spitzer are generally correct. Nicolas Cowan, an astronomer at McGill University, who used Spitzer data to create heat maps of the gas giants among the exoplanets, not sure if the old telescope could cope with the problem of the study of the worlds smaller.
“Raw telescope data often exhibit variations of a few percent, which any side does not affect the question of the planet or even its parent star,” says Cowan. But in contrast, the changes announced to offset the brightness of 55 Cancri e, is measured in parts per million. Such thinnest dimension generally steel, in principle, because the native star, the planet is very bright and therefore provides more photons for astronomers. Moreover, 55 Cancri e passes in front of the star when viewed from Earth, casting a shadow in which astronomers can search for information about a possible planet’s atmosphere and its surface.
“But honestly, it’s an exciting result, which marks the collision of ecogeology and ecoclimatology — continues Cowan. — I suspect that the signal is an instrumental rather than astrophysical in nature. Spitzer works better than it should, but we tend to harness it, don’t bother. We learn science, carefully studying all options on which the spacecraft and instruments could cause are gradually changing the brightness of the system. We are very confident that we can entrust our models of the work of Spitzer ten thousand times without one; we’re in uncharted territory right up until we are concerned about the behavior of the detector”.
Heather Nutson, an astronomer at the California Institute of technology, which invented the thermal mapping of giant exoplanets for Spitzer, skeptical. “The issue is a billion dollars really is like this: 55 Cancri e is, in fact, a solid planet, but absolutely no or little atmosphere?”, she says.
Nutson part of a team under the leadership of her former graduate students Bjorn, Bennike, which now uses the Hubble space telescope to explore planets in search of a long day. In particular, they look at the planet during transit, waiting for the expansion of the planetary shadow associated with the fact that starlight is absorbed by hydrogen-rich atmosphere. Another group of researchers took publicly available data Supervisory program Bennecke to say about the discovery of the atmosphere on 55 Cancri e, but Nutson and doubts in these results.
“This planet was the target of many observational campaigns with the Hubble and Spitzer, and we still haven’t found answers to simple questions about the composition of the subsoil and the atmosphere, says Nutan. — This speaks to the difficulty of observing such small planets.”
If 55 Cancri e is a lava world it can open new frontiers in the study of exoplanets. Out of the thousands of exoplanets now known, is the most warm supersell, staying close to their stars, which speaks of the great prevalence of this type of planets in our galaxy. Launched in 2017, the satellite TESS and CHEOPS must collectively discover and learn a lot more planets like 55 Cancri e.
CHEOPS the band is already planning extensive observations of 55 Cancri e, says Demory, in search of plumes or other emissions associated with possible volcanic eruptions. Space telescope the James Webb, is scheduled for launch in 2018, could study the chemical composition of the vaporized material from the surface of a scorched planet’s powerful radiation from the stars, “to smell gunpowder breeds”, like pyroxene and olivine, to study geochemical cycles distant world. And to dispel the notion that 55 Cancri e contains oceans of lava, once and for all.
“People may wonder why this kind of planets is interesting, if it is completely unsuitable for life, unlike the Earth, says study co-author Vlada Stamenkovic, a geologist at Caltech. But to understand the terrestrial planets, we need to understand their chemistry and internal processes that control essential to the life of the oceans and atmospheres. Partially molten planets like 55 Cancri e could help us learn more about what is inside them and how they are made”.
These planets are useful, but look like hell — you would not want them to live. And yet they will be extremely useful for understanding other planets, one of which one day we might get to meet a local and spend local dawn the sun, sipping a delicious local coconut.