Many new HARPS discoveries?

Many new HARPS discoveries.

It seems that many new planets from the HARPS instrument can be expected. A four year study of 400 stars seems to have found 45 new candidates. All of them are below Jovian mass, and all of them apparently orbiting F, G, and K stars. If all of these planets have been found around F, G, and K stars, I wonder how many candidates HARPS has around M stars, hmm... And another interesting result,

ScienceNews wrote:

As many as 30 percent of sunlike stars posess close-in, relatively small planets -- only four to 30 times as heavy as Earth

(from http://www.sciencenews.org/view/generic/id/32547/title/Many_stars,_many_planets)

This would be pretty neat. The article also says that all of the 45 candidates have orbital periods less than 50 days. So what does this mean for habitability? Well, it's likely that they're all too close to the star to be habitable. Using HD 69830 as a template K star, I found that a planet in a 50 day orbit is about 0.252 AU from the host star. Choosing to use this site, http://www.astro.indiana.edu/~gsimonel/temperature1.html, to calculate the temperature of a planet for me (I could've done the math, but didn't feel like it, and didn't have the appropriate equation handy), I found that such a planet has a surface temperature of 514 K. So, even a K star is too hot for a 50-day habitable planet. So the point is, none of these planets are habitable.

Lovis wrote:

These are preliminary numbers, but there's no doubt that the majority of them will turn out to be real.

The article tells us that the stars range from 0.7 to 1.2 solar masses, and that among the 45 planets, they

ScienceNews wrote:

include at least eight superEarths

. This is pretty good news! It would more than double the known amount of superEarths. So why no press release?

ScienceNews wrote:

At this point, most of the 45 orbs are only candidate planets because their existence has yet to be confirmed by further spectroscopic studies.

That's fine, we can wait some more. It's expected that some of the planets will be announced this coming June. Specifically, three superEarths orbiting a single star. This would make it the second known tripple terrestrial extrasolar system, and the first known orbiting a main-sequence star (The other is PSR B1257+12). The article says (accurately) "The announcement will be the first time researchers have detected such a low-mass trio around a single star".

With 45 low mass planets, all of which orbit somewhat close to their stars, we might be able to expect a transit or two. A transiting superEarth would be a real gem, the first known of it's kind. Transiting Neptunes would also be nice, only one is known so far.

Unfortunately, and as usual, some media take such announcements the wrong way. Mercury News, specifically, wrote

http://www.mercurynews.com/healthandscience/ci_9437039 wrote:

Planet Similar to Earth found

. They claim a superEarth has a mass of four Earth-masses in the habitable zone around a small star. Something that article did seem to get right, is that many of the terrestrial planets are in eccentric orbits.

ScienceNews wrote:

Lovis presented the findings May 20 in Cambrige, Mass, at an International Astronomical Union conference on extrasolar planets.

Fortunately, Greg, at the Systemic blog at www.oklo.org, went that conference. He was able to quickly jot down some notes. His notes say that one planet has a period of 2.34 days, and a mass of 5.8 Earths. Another planet has a period of 4.08 days, and a mass of 22.8 Earths. Two planets in the same system, a 6.1 Earth-mass planet with a 4.22 day orbit, and a 38.3 Earth-mass planet in a 22.8 day orbit. Another two planet system, containing a 4.1 Earth-mass planet in a 3.8 day orbit, and a 40 Earth mass planet in a 35.6 day orbit. A third two-planet system, containing a 10 Earth mass planet in a 7.44 day orbit with a 0.65 eccentricity, and a 20 Earth-mass planet in a 45 day orbit with an eccentricity of 0.23. A single, 10 earth-mass planet with a 39 day orbit with an eccentricity of 0.5. And finally, that tripple SuperEarth system. The planets have masses of 4.3, 6.9 and 10 Earth masses, with periods of 4.3 days, 9.6 days, and 20 days, respectively. The first planet has an eccentricity of 0.02. Greg writes that 80% of the planets appear to belong to multiple planet systems, but low-order mean motion resonances seem to be rare. You can find more information here, http://oklo.org/?p=281 . Additionally, Greg says that the data on HD 69830 was addressed at the IAU meet, and it turns out that more data is available on Mu Arae, and all four planets there are accounted for. The available data on HD 69830 has doubled, with "virtually no changes to the masses and orbits of the three known planets. Long-term scatter in the HD 69830 data set is at the ~90 cm/sec level, indicating either the effect of residual stellar jitter, or perhaps the presence of additional, as-yet uncharacterized bodies".

It looks like there's a lot of information we can look forward to!

Surely I'm wrong but I could infer the host stars could be these ones:

HD 63765 - G9V 32.61 pc (Car)
HD 65277 - K5V (double?Multiple?) 17.46 pc (Mon)
HD 65562 - K2V 35.06 pc (Pup)
HD 65907 A (this is quite nearby and multiple too) - G0V 16.19 pc (Car)
HD 66221 - G6V 43.02 pc (Pup) HD 67458 - G0V 25.59 pc (Pup)
HD 68607 - K2V 40.03 pc (Vel) HD 68978 A (?) - G0.5V 27.04 pc (Pup)
HD 69655 - G1V 27.07 pc (Vel)

Who knows? From this one Spectroscopic parameters for 451 stars in the HARPS GTO planet search program. Stellar [Fe/H] and the frequency of exo-Neptunes

OH! There are emoticons too...

The entirety of the star sample can be found here,
http://www.astro.up.pt/~sousasag/harps_gto_catalogue.html

Unfortunately, even if unsurprisingly, the table doesn't tell us which stars host the new candidates.

I see. However I "feel" HD 65907 A is hiding us something interesting. I dunno why....
If so, it woult turn very useful for my Science Fiction...

I seem to have been mistaken. HD 69830 is a K0 star, being the hottest possible K-type star. If HARPS found a companion around a cooler star, perhaps K5 or K6, then the habitable zone comes within that which would allow 50-day period planets to be habitable.

Yeah, for example HD 55 is an "Epsilon Indi's kin" with HZ=0.34 AUs (calculated from luminosity).

If I've got the meeting right, it'll be June 16-18, in Nantes, France.
http://www.sciences.univ-nantes.fr/geol/SuperEarths2008/

Low mass planets, the known ones tend to be nearby because it's just easier to find low mass planets around nearby stars. If it's a bright, low-mass star, that's a plus.

From the GTO Catalogue, my guesses/hopes:

Tau Ceti is quite nearby at 11.89 ly. A tad warm at G8V though. I'm hoping there's something there.
HD 13789 is relatively nearby at 74.5484 ly, and is a K2 star.
HD 14635 is relatively nearby at 87.3058 ly, a tad hotter at K0.
HD 16270 is relatively nearby at 69.3027 ly, and a cool K3.5V. It also has a L1 brown dwarf comapnion.
Gliese 9115 A is close at 64.376 ly, and K3.5V
Epsilon Eridani is also in there, 10.724 ly away, and a nice, cool, K2V. But Eps Eri is a rather active star. One known planet, one unconfirmed.
Delta Eridani is close, at 29.4809 ly, K0IV star.
HD 23356 is close at 45.8058 ly, and a K2V star.
Keid A is also under scrutiny, and that's really close at 16.4439 ly. I hope there's something here, too.
Gliese 1079 is a close K2V star at 58.4963 ly.
Gliese 204, quite close and quite cool, 42.3212 ly, and spectral K5V respectively.
HD 40307, 41.8217 ly, K2.5V.

HERE WE GO!!! 3-MULTI-PLANET SYSTEMS, BEARING SUPER-EARTHS!!!

http://exoplanet.eu/star.php?st=HD+40307
http://exoplanet.eu/star.php?st=HD+181433
http://exoplanet.eu/star.php?st=HD+47186

Average separations and eccentricities are not available at the moment. About the former, performing a simulation with Systemic Console and online data at SIMBAD, I found this:

HD 40307

*Mass=0.77 Mso* Luminosity=0.15 Lso HZ=0.39 AUs

Planet b - 0.047 AUs
Planet c - 0.0807 AUs
Planet d - 0.13 AUs

Unluckily none is habitable -__-


HD 47186

*Mass=1.02 Mso* Luminosity=1.1 Lso? HZ=1.05 AUs

Planet b - 0.05 AUs
Planet c - 2.4 AUs

2nd planet is Saturn-sized, but it may bear habitable moons, perhaps.


HD 181433

This is a bit "weird". Spectral class is K3III-IV, but mass is 0.77 Solar and radius likely 0.82 Solar radii. Maybe an old bright K-dwarf?

*Mass=0.77 Mso* Luminosity=0.33 Lso HZ=0.58 AUs

Planet b - 0.079 AUs
Planet c - 1.81 AUs

Planet c is a mere Jupiter analogue. Probable inner terrestrials?

Regarding HD 181433, the star's Hipparcos catalogue entry gives the spectral type as K5V, which given the distance and magnitude seems more plausible than the K3III-IV given by SIMBAD.

Out of interest where did you get the data on the stellar masses?

Lazarus wrote:

Regarding HD 181433, the star's Hipparcos catalogue entry gives the spectral type as K5V, which given the distance and magnitude seems more plausible than the K3III-IV given by SIMBAD.

Out of interest where did you get the data on the stellar masses?

HD 40307's parameters should be available here

http://cdsads.u-strasbg.fr/cgi-bin/nph-bib_query?2005ApJS..159..141V&db_key=AST&nosetcookie=1


About HD 47186 and HD 181433 I did a quick search with Simbad Online data, finding temperature and radii.

You can also find a heap of information in the GTO catalogue I linked to earlier.

This is an awesome discovery!!

All I can say is "wow". It's finally happenning, the flood of exoplanetary discovery. I wonder how long it will take us to have discovered planets around half of the nearest 100 stars?

The sweetest thing is that there are still 37 solid candidates left to be announced

Have fun browsing this funny journal issue at DeviantArt

303?! This is ...SUPEREARTHA!!

Shoot, when I heard that the triple super-earth system HD 40307 was a little less than 50 light years away, I had hoped that a bunch of the other systems that got lost in the large amount of discoveries would also be that near, but there weren't any more that nearby. Oh well, one of these days a survey will have to target the nearest stars with the latest capabilities, and they should find a bunch.

youknowandy wrote:

Shoot, when I heard that the triple super-earth system HD 40307 was a little less than 50 light years away, I had hoped that a bunch of the other systems that got lost in the large amount of discoveries would also be that near, but there weren't any more that nearby. Oh well, one of these days a survey will have to target the nearest stars with the latest capabilities, and they should find a bunch.

I remind you there are still 37 Super earth hosts left to be announced...no despair

Has anybody the temperatures of this three planets?

Stalker wrote:

Has anybody the temperatures of this three planets?

Uhm, nope. I can give you the habitable zones of each star:

HD 40307 HZ=0.4 AUs
HD 47186 HZ=1.05 AUs
HD 181433 HZ=0.6 AUs

What is expression has use to find the temperature?

Stalker wrote:

What is expression has use to find the temperature?

There should be some. However if you do the average separation of the planet : the habitable zone, you should get the equivalent orbital zone.
For example:

Habitable zone= 0.4 AUS


Planet lies at 0.4 AUs

0.4/0.4=1 AUs (=habitable)

0.08/0.4=0.2 AUs (hotter than Mercury)

If you want an estimate of the temperature, use the formula:

T=[L(1-A)/(16πσd²)]^1/4

Where

• T is the temperature in kelvin
  
• L is luminosity of the star in watts
  
• A is the planet's albedo
  
• σ is the Stefan Boltzmann constant = 5.6704×10^-8 W m^-2 K^-4
  
• d is the planet-star distance in metres
  

Typical values for the albedo:

• Moon - 0.1
  
• Earth - 0.35
  
• Venus - 0.65
  

Note that both Earth and Venus come out at 250 K (about -25 degrees C) according to this formula: greenhouse heating by the atmosphere is not taken into account.

Tx

Oh great

are you on your expression? because for the first planet, and with an albedo as Venus I find 357581441K (impossible I think)

You've made a mistake somewhere then.

Using the values given by Edasich in this post...

Luminosity of HD 40307 = 0.15 times solar
Distance of first planet = 0.047 AU

Units conversion to SI:

Solar luminosity = 3.839×10²⁶ (according to the Wikipedia article)
1 AU = 149597870691 m (according to the IAU)

Taking A=0.65:

T=((0.15×(3.839×10²⁶))*(1-0.65)/(16×π×(5.6704×10^-8)×(0.047×149597870691)²))^1/4

This works out as 615 K when I do it.

To put this into Google calculator (which can also handle the units conversion and includes the Stefan Boltzmann constant), do a search for the following:

Code:

((0.15*3.839e26 W)*(1-0.65)/(16*pi*Stefan Boltzmann constant*(0.047 AU)^2))^(1/4)

(note that this is case sensitive, you must type "Stefan Boltzmann constant" exactly as shown here.

You can specify that the final result is in kelvin by doing a search for:

Code:

((0.15*3.839e26 W)*(1-0.65)/(16*pi*Stefan Boltzmann constant*(0.047 AU)^2))^(1/4) in K