# Thread: Interesting extrasolar planet discoveries

1. And here are some data about the sizes of each planet in Jupiter masses:

Gliese 876c: 0.56
HD 92788b: 3.86
HD 16175b: 4.5
HD 20367b: 1.07
HD 142415b: 1.62
HD 142b: 1
HD 108874b: 1.36 (that solar system also features a Jupiter sized planet 2.5 times as far away from the sun - maybe helping in the defence of a possible moon with life)
HD 150706b: 1
HD 190228b: 4.99

So from the data above i would say when we get those planets with a size like:

HD 92788b
HD 16175b
HD 190228b

... as possible planets with a Earth-sized moon around them.

Is the calculation of how big a moon typically would be if you for instance double the size of the planet? I mean, taking a planet with 2 Jupiter-masses, would that mean that it is likely we would get a 2 Ganymedes-masses moon around that planet or isn't it a linear calculation?

BTW: Would it be easier or harder to find a Earth-sized moon around a planet than a Earth-sized planet around a star if we would search just as many of each type? I'm not talking about in which situation there are most Earth-sized planets/moons, but what future telescopes like Kepler would find easier finding.

2. Originally Posted by Sporally
And here are some data about the sizes of each planet in Jupiter masses:

Gliese 876c: 0.56
HD 92788b: 3.86
HD 16175b: 4.5
HD 20367b: 1.07
HD 142415b: 1.62
HD 142b: 1
HD 108874b: 1.36 (that solar system also features a Jupiter sized planet 2.5 times as far away from the sun - maybe helping in the defence of a possible moon with life)
HD 150706b: 1
HD 190228b: 4.99

So from the data above i would say when we get those planets with a size like:

HD 92788b
HD 16175b
HD 190228b

... as possible planets with a Earth-sized moon around them.

Is the calculation of how big a moon typically would be if you for instance double the size of the planet? I mean, taking a planet with 2 Jupiter-masses, would that mean that it is likely we would get a 2 Ganymedes-masses moon around that planet or isn't it a linear calculation?

BTW: Would it be easier or harder to find a Earth-sized moon around a planet than a Earth-sized planet around a star if we would search just as many of each type? I'm not talking about in which situation there are most Earth-sized planets/moons, but what future telescopes like Kepler would find easier finding.
If the moons and the planet condense from the same proto-Jovian disk then there has to be some relationship between the masses, but other factors could have a substantial effect. Someone here referenced a paper that concluded that the satellites of a planet that condense with it should be about 1/10000th (?) the mass of the planet. <calculates mentally> the regular moons of Jupiter would add up to about 1/5000th the mass of Jupiter, and Saturn similarly, so that sounds about right. By that token an Earth mass satellite would be unlikely around anything smaller than a brown dwarf. A Mars sized body though wouldn't surprise around a big Jovian.

As to which are easier to find, I dunno. But there's talk of finding exomoons around transiting planets.

I estimated the bolometric luminosities by applying the StefanBoltzmann law to the temperatures (and radii) on exoplanets.eu. The approximation probably gets ratty for cool M dwarfs. Another way would be to have looked up the spectral types in a bolometric correction table. That was too tedious. Note that at least one prominent website devoted to the habitability of exoplanets uses uncorrected visual luminosities resulting in incorrect conclusions (such as Gl581c being cooler than Earth).

3. Originally Posted by Sporally
Thx, but could you give me a more direct link to the page you've read that article about the exoplanet gossip on?
There are no articles, just rumors circulating... most I've learned from Siguršsson's blog, he has an access to the extrasolar planet conferences where these things have been mentioned.

Well, looks like the 1.7 Re planet has been mentioned in a CoRoT press release article from May:

The team also announced that they have detected signals as small as 5 parts in ten thousand. If this arises from a transit it would imply the detection of a planet with a radius 1.7 times that of the Earth.
Since the CoRoT team seems to follow closely ESA's PR tradition, don't expect to hear about it anytime soon.

4. Originally Posted by Sporally
I think we were talking past each other. Guess Drunk Vegan meant that by the planets we have found it is very likely that there are moons out there, and looking at the sizes of the planets i would say that there probably are Earth-sized moons in orbit around them.
Indeed I was. That's why I specified "we only have data on the Jovians they orbit."

It's entirely plausible that there's at least one habitable moon orbiting an exoplanet we've already discovered. Somewhere in our catalogues there could be a hidden gem where we actually have the coordinates, distance, distance from sun, and data on the planet that moon orbits.

We just don't know it yet because our instruments can't resolve moons around exoplanets yet.

5. Originally Posted by Drunk Vegan
Indeed I was. That's why I specified "we only have data on the Jovians they orbit."

It's entirely plausible that there's at least one habitable moon orbiting an exoplanet we've already discovered. Somewhere in our catalogues there could be a hidden gem where we actually have the coordinates, distance, distance from sun, and data on the planet that moon orbits.

We just don't know it yet because our instruments can't resolve moons around exoplanets yet.
Actually there is a possibility of one system thats been discovered with two jovians in it's stars Habital zone, each of which could sport habitable moons.

Not saying they will, but its certainly possible.

6. As a point of interest does anyone have any details on the location of WASP-12B? I have been trying to find its RA and Dec online, but to no avail. I have its (presumably approximate) distance, but not its whereabouts.

7. It doesn't seem to be public information yet.

8. Does that happen a lot? Do they think someone will steal the discovery or something?

9. 2008 exoplanet discovery count, 42 so far, gives us the second best year, but this is 20 short of last years final result of 62. I assume some diminishing returns was expected; it is a law.

10. Originally Posted by George
2008 exoplanet discovery count, 42 so far, gives us the second best year, but this is 20 short of last years final result of 62. I assume some diminishing returns was expected; it is a law.
Nitpick 1: Year's not over!
Nitpick 2: Diminishing returns only if effort put in is equal to, or more than last years.

(Sorry! Couldn't resist)

p.s 42 is a good number though... and are they qualitatively better than last years? Closer to Earth characteristics I mean..

11. Originally Posted by PraedSt
Nitpick 1: Year's not over!
Nitpick 2: Diminishing returns only if effort put in is equal to, or more than last years.
My guess is that the "big guns" are not up there yet. Then, we will back to more of an exponential growth in the count.

12. How fortunate we are, that we can be disappointed by a possible non-exponential growth in the number of planets discovered beyond our solar system.

Whereas just a dozen-odd years ago we'd have to be disappointed by the continued lack of discovered planets outside our solar system...

13. Established Member
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Originally Posted by Kullat Nunu
There are no articles, just rumors circulating... most I've learned from Siguršsson's blog, he has an access to the extrasolar planet conferences where these things have been mentioned.

Well, looks like the 1.7 Re planet has been mentioned in a CoRoT press release article from May:

Since the CoRoT team seems to follow closely ESA's PR tradition, don't expect to hear about it anytime soon.
Has the CoRoT team ever announced a planet without RV confirmation? My impression was that they had originally planned to but probably ran into too many false positives. OTOH it's very, very strange to mention something like this in a press release then never follow up.

14. Originally Posted by Kullat Nunu
40 Eridani = Omicron2 Eridani = Keid = the parent star of Vulcanus. You mean Epsilon Eridani.
USA Today: Earth-like planet in Epsilon Eridani? It is logical, Captain

Star Trek fans, take heart — Mr. Spock's fabled home star, the nearby Epsilon Eridani, could harbor an Earth-like planet.

NASA astronomers today report that the triple-ringed star has an asteroid belt and a Jupiter-like giant planet in roughly the same orbits as in our own solar system. Only 850 million years old, a fifth the age of Earth's sun, Epsilon Eridani resembles a younger twin to our solar system. About 62 trillion miles away, it is the closest known solar system.
NASA Spitzer Telescope Mission News: Closest Planetary System Hosts Two Asteroid Belts

New observations from NASA's Spitzer Space Telescope indicate that the nearest planetary system to our own has two asteroid belts. Our own solar system has just one.

The star at the center of the nearby system, called Epsilon Eridani, is a younger, slightly cooler and fainter version of the sun. Previously, astronomers had uncovered evidence for two possible planets in the system, and for a broad, outer ring of icy comets similar to our own Kuiper Belt.

Now, Spitzer has discovered that the system also has dual asteroid belts. One sits at approximately the same position as the one in our solar system. The second, denser belt, most likely also populated by asteroids, lies between the first belt and the comet ring. The presence of the asteroid belts implies additional planets in the Epsilon Eridani system.

"This system probably looks a lot like ours did when life first took root on Earth," said Dana Backman, an astronomer at the SETI Institute, in Mountain View, Calif., and outreach director for NASA's Sofia mission. "The main difference we know of so far is that it has an additional ring of leftover planet construction material." Backman is lead author of a paper about the findings to appear Jan. 10 in the Astrophysical Journal.

15. The published exoplanet orbit is not compatible with the observed disk structure. Perhaps the orbit modellers need to redo their optimization with the penalties biassed to two planets in nearly circular orbits. I don't know if the state of the art has advanced greatly, but it used to be the case that there was sometimes ambiguity between, for example, solutions with two planets in low eccentricity orbits and one planet in an eccentric ("loopy" seems to be the media friendly word) orbit.

16. Isn't it funny that a report that a few years ago would have been monumental, is now boring.

17. Yeah, great Just as the number of exoplanet discoveries per year is exponential, so is our expectation about the exoplanets - in a way great, in a way sad. What i mean by this is when i think about the future in all astronomy aspects aswell as engineering feats aspects, i can only say that we unfortunately take things for granted too soon. One day i was hoping to hear news about water on Mars or exoplanets just smaller than Jupiter - today we have found both things but are already getting too easy about it and just looking forward to the next big thing. If only i could enjoy our discoveries some more

18. Such is the hedonic treadmill of progress. Actually the five (or six, exoplanet finders like to count brown dwarfs as planets) gas giants are slightly interesting in that they are cool (a ~3AU) rather than hot (a ~0.05AU). Their orbits are all quite loopy, which could be seen as part of an emerging consensus that stellar systems like ours (circular orbits, an inner system free of gas giants) are rare. This might help explain the apparent lack of aliens.

19. Low Mass Companions for Five Solar-Type Stars from the Magellan Planet Search Program. Note the lowest mass of these low mass companions is 1.2Mjup. Fig.9 is a little disturbing.

20. Hubble Announces A Major Extrasolar Planet Discovery

NASA will hold a Science Update to report on a significant discovery about planets orbiting other stars at 2:30 p.m. EST, Thursday, Nov. 13, in NASA's James E. Webb auditorium. This unique discovery, made by the Hubble Space Telescope's Advance Camera for Surveys instrument, also will be featured in the Nov. 14 issue of the journal Science.

21. Oh my god, i can't wait for this. Great news, thx:surprised

A couple of questions:

1) If we assume that the magnificant about this particular discovery has to do with nothing else but size, what could we expect from Hubble? I mean, Hubble has a limit, and i've never consider it the best exoplanet searcher.

2) Has this even happened before that they call a press conferance about an exoplanet discovery?

3) Since Hubble isn't the mail exoplanet searcher we have, could it be that they are just calling the press conferance because it is an amazing achievement for Hubble or can we expect it to be an amazing thing for exoplanet searching as a whole?

I will be streaming the conferance live - i guess you can do that from nasa.gov...

Are you guys in for a bet for what will be announced to see who is closer?

22. Can somebody decipher this?

23. That has to be it.

24. 51 exoplanets found thus far in 2008... and counting.

25. Originally Posted by Bynaus
Damn, i read it as tuesday instead of thursday - and i barely could wait until tuesday in the first place

So the big thing is that it is a direct observation of an exoplanet?

Size: 1.6 - 3.4 M(jup)
Distance from parent star: 18AU

26. Originally Posted by Sporally
Damn, i read it as tuesday instead of thursday - and i barely could wait until tuesday in the first place

So the big thing is that it is a direct observation of an exoplanet?
That's what I'm guessing, but maybe something else was found on the follow-up?

27. Right.

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