Kepler Discovers Planets-like Objects Hotter Than Stars

Possible habitable zones around stars. Credit: Kepler mission

The Kepler mission announced the discovery of 5 new extrasolar planets today at the American Astronomical Society meeting in Washington, DC, each with some very unusual properties. But additionally, the space telescope has spotted some Jupiter-sized objects orbiting stars, and these objects are hotter than the host star. The science team has no idea what these objects could be, but they are part of 100 planetary candidates Kepler has observed that are still being analyzed.

The Kepler mission’s objective is to search for Earth-size planets in the habitable zones of other stars, and the planets announced today are comparable in size to Neptune, Jupiter and the other gas giants of our solar system but are substantially less dense. This first set of five new planets discovered by the Kepler mission was discovered in the first six weeks of the telescope’s operation. “The quick discovery indicates that Kepler is performing well,” said William Borucki, from NASA’s Ames Research Center.

One of these new planets is similar in many ways to Neptune, although its irradiation level is much higher. A second planet is one of the least dense planets ever discovered, and along with the other three, confirms the existence of planets with densities substantially lower than those predicted for gas giant planets. Borucki said Kepler 7b has the density of styrofoam, at .17 grams per cubic centimeter, basically a density of zero.
The smallest planet, Kepler 4b, is 4.31 earth radii, or about Neptune-sized. The other four about the size of Jupiter. All five planets have short orbital periods, and follow-up observations will be made with ground-based telescopes.

Since these planets are close to their host stars, they are very hot, hotter than about 1500 K. 1300 K is the temperature where molten lava flows.

Kepler launched in March 2009 and the mission is expected to last 3½ years. The team now has an additional 8 months of data are now available to analyze. Borucki said in 2010 Kepler will focus on the discovery of smaller planets, with an Earth-sized planet being the “holy grail” of exoplanet discoveries.
Other objects detected by Kepler include unusual variable stars, including binaries, oscillating stars, pulsating variables, and more, including other extrasolar planets, but declined to divulge more, saying his team has to be patient and do the confirmations on all the objects before.

Borucki also said data from Kepler will be released to the public on a regular basis starting in June 2010.

Source: AAS Press conference

15 Replies to “Kepler Discovers Planets-like Objects Hotter Than Stars”

  1. I’m glad they overcome the noise problem that was predicted as preventing Earth-size hunting until 2011. Or did they? Perhaps the press conference is spinning the science as much as it can.

    Spare details on that, still, good news so far!

    the space telescope has spotted some Jupiter-sized objects orbiting stars, and these objects are hotter than the host star. The science team has no idea what these objects could be,

    Those are likely the first examples of Nysod spheres, “hypothetical mega-structures” that an alien civilization will spawn as “the logical consequence of the long-term survival and escalating energy needs of a technological civilization”.

    It is the end result of accumulating asteroid resources, generating massive amounts of waste heat to get rid of combined with setting off a massive AGW (Alien Global Warming) effect.

  2. @ Hans-Peter Dollhopf:

    Here is a description of Kepler’s in-situ photometer calibration before flipping the lid, here’s a description of the carefully chosen star-field including known short-period planets to try out its sight on, and here’s a description of one of those try-outs.

    Considering that Kepler was constructed to look at a specific star-field, it’s noise problem was known before it flew, and it spent a month getting to position, stabilize and characterize its instruments, I would say it is as exactly calibrated as they get. At a guess. 😉

  3. That these planets are hotter than their host star seems to run against what I would thermodynamically expect. I suppose a condensing gas giant goes through a phase similar to a T-tauri star, as I recall the name, where heat is generated by gravitational collapse. This is just rather odd IMO.


  4. interesting find.
    What region of the sky is kepler looking at again?

    I think they should check the Zeta Reticuli Binary System (2 yellow main sequence dwarfs 1 is almost exactly like our own sol)
    where the supposed “grey aliens” are from.

    If they found an earthlike planet there it would make it seem that much more plausible.. and if nothings found at least it should put the matter to rest.

  5. @ Lawrence B. Crowell,

    There is also the possibility that in a newly formed planet, whose surface is hotter than its star, there is a fast nuclear fission reactor at its core resulting from the accumulation of heavy elements, such as uranium, contributing to the thermal energy output of that planet.

  6. @IVAN3MAN: That is also strange. There is enough uranium in the planet to generate that sort of nuclear reactor? That is also rather interesting. I know that in geophysics circles there is some discussion on whether the Earth’s core is a nuclear reactor, instead of being heated by weak decay processes. I suppose some planets do win the prize for high AMU metallicity.

    It sounds like an interesting planet to study from afar. It sounds like absolute hell to actually visit.


  7. Folks – did anyone see mention of when the next update is due?

    I do wish they’d make real time data available – from a PR point of view it would be a boon – looking at the readings from the starts that showed candidate signals – and waiting for the next dip – it might not be a traditional disciplined publication process, but it would draw a huge amount of popular interest…. I betcha some people will just sit there staring at the data…

  8. Lawrence B. Crowell:

    I know that in geophysics circles there is some discussion on whether the Earth’s core is a nuclear reactor, instead of being heated by weak decay processes.

    Yeah, that’s what got me thinking; Neptune (but not Uranus, for some reason) radiates 2.61 times as much energy as it receives from the Sun. I wonder: how much warmer, or even hot, Neptune was early in the Solar System’s history?

    Also, I found this paper, “Magnetic Field Generation in Planets and Satellites by Natural Nuclear Fission Reactors”, which makes interesting reading.

  9. LC, IVAN – I want to run an oddball theory by you – something I’ve heard and don’t have the knowledge to refute directly (and thus am mildly curious about it).

    The idea is simple – there’s a very small black hole at the center of a planet, and Its growth is limited by its surface area and by radiation pressure, and so it doesn’t gobble up the planet, but is rather at equilibrium, eating mass at a constant rate.

    I wouldn’t know how to write down the equations to figure out if such an equilibrium exists – not enough physics in me.

    We have very little observational data on extra-solar planets, so know very little about their beginning of life and end of life – but this comment about hot planets made me remember this idea.

    I guess my question is not whether this is a likely scenario, but rather do we have a concrete argument that rules it out.

  10. @Lawrence B. Crowell
    J. Marvin Herndon proposed the georeactor theory in about 1993 (Feasibility of a nuclear fission reactor at the center of the Earth as the energy source for the geomagnetic field. J. Geomag. Geoelectr. 45, 423-437.) Herndon is a good multidisciplinary scientist:Ph.D. degree in nuclear chemistry in 1974 from Texas A&M University. For three years, J. Marvin Herndon was a post-doctoral assistant to Hans Suess and Harold C. Urey in geochemistry and cosmochemistry at the University of California, San Diego.

    As I understand it, he was quite impressed by the discovery of a nuclear fission reaction that took place in an underground uranium deposit in Oklo, Gabon, Africa. Apparently, about 1.5 billion years ago a fission reaction continued sporadically for hundreds of thousands of years in this location. (And in a few others discovered since .) Herndon hypothesizes that uranium and other fissionable elements sank to the centre of the earth during its formation and initiated an ongoing fission reaction there that powers the geomagnetic field. His idea is not generally accepted within the geophysical community.

  11. Black holes are not a source of the energy. The reason is simple to see. Consider a model where you have a black hole in a background temperature T which equals the temperature of the black hole horizon. The horizon has a temperature due to Hawking radiation. Now if the black hole emits a quanta of radiation is mass decreases and its temperature thus increases. This pushes it to a temperature higher than the background and it radiates faster. The opposite happens if the black hole absorbs quantum from the environment, it get cooler. radiates less and gets bigger. Equal temperature is not equilibrium, whch is contrary to our usual sense of thermodynamics.

    So the problem is this. A micro-black hole is not stable and will either runaway in a large pulse of radiation, or explosion, or it will grow and within a rather short time consume the planet. The system is not stable.

    The nuclear reactors in Gabon I have read about. It does make some sense that heavy elements such as uranium makes its way to the center of planets during formation. I must confess I have no idea how you would test this hypothesis.


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