Astronomers find star with three super-Earths

July 30, 2015
This artist's rendition released by NASA on July 30, 2015 shows one possible appearance for the planet HD 219134b
This artist's rendition released by NASA on July 30, 2015 shows one possible appearance for the planet HD 219134b

Astronomers said Thursday they had found a planetary system with three super-Earths orbiting a bright, dwarf star—one of them likely a volcanic world of molten rock.

The four-planet system had been hiding out in the M-shaped, northern hemisphere constellation Cassiopeia, "just" 21 from Earth, a team reported in the journal Astronomy & Astrophysics.

It comprises four planets—one giant and three super-Earths orbiting a star dubbed HD219134.

Super-Earths have a mass higher than Earth's but are lighter than gas giants like Neptune, Saturn or Jupiter. They can be made of gas, rock, or both.

The planet with the shortest orbit, HD219134b, zips around every three days, and has now been observed transiting across the face of its star as seen from the vantage point of Earth.

Measurements from the ground and with NASA's Spitzer space telescope showed its mass was 4.5 times higher than Earth's, and that it was 1.6 times larger.

"Its mean density is close to the density of Earth, suggesting a possibly similar composition as well," said a press statement from the University of Geneva, whose took part in the research.

"It's very close to the star. The temperature is about 700 degrees" Kelvin (427 Celsius, 800 Fahrenheit), study co-author Stephane Udry told AFP.

"Probably the surface is melting... kind of a melted lava world with volcanoes... not good for life."

This artist's rendition released by NASA on July 30, 2015 shows a sky map with the location of the star HD 219134 (circle), host
This artist's rendition released by NASA on July 30, 2015 shows a sky map with the location of the star HD 219134 (circle), host to the nearest confirmed rocky planet found to date outside of our solar system

It was not in the so-called "habitable zone" of its star, and would not have liquid water necessary for life.

But HD219134b is exciting for another reason: it is the closest transiting planet known to scientists, and thus offers a rare opportunity for further study of its composition and atmosphere against the backdrop of its star.

"These transiting systems are especially interesting in that they allow characterisation of the atmosphere of the planet (by studying) the light of the star going through the atmosphere," Udry said.

And the system is relatively near at a distance of 21 light years from Earth. By comparison, the closest star to our Sun is three light years away, and the second six light years.

Among HD219134b's fellow , the second furthest from the star weighs 2.7 times as much as Earth and orbits in 6.8 days, the next is 8.7 times more massive than Earth with a 47-day orbit.

A giant planet further out orbits once every three years, the team said.

Explore further: Hubble sees a 'behemoth' bleeding atmosphere around a warm exoplanet (Update)

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Modulus64
1.6 / 5 (7) Jul 30, 2015
These 3 earths may have shared organisms blasted off one or more of their surfaces by asteroids strikes. If, from this they all developed different forms of life independently any intelligent life in that system may have a wildly different view of life in the universe to that here on Earth. Such a thing may have massively accelerated their race for space technology or even just simple things like telescopes and spectrometers.
SciTechdude
2.3 / 5 (3) Jul 30, 2015
If they were transmitting any messages from there, we could see their radio noise by now.
ViperSRT3g
5 / 5 (4) Jul 30, 2015
Did you not read the article? One of the planets orbits the star IN JUST THREE DAYS!
Manfred Particleboard
4 / 5 (7) Jul 30, 2015
By 'three Earths' you mean three habitable worlds with stable atmosphere and liquid water?
No?
Then the article should be titled "Astronomers find star with three planetary bodies".
Not much of an article and not very clickable is it.
PhotonX
4.9 / 5 (7) Jul 30, 2015
These 3 earths may have shared organisms blasted off one or more of their surfaces by asteroids strikes. If, from this they all developed different forms of life independently any intelligent life in that system may have a wildly different view of life in the universe to that here on Earth. Such a thing may have massively accelerated their race for space technology or even just simple things like telescopes and spectrometers.
Except that none of them are in the habitable zone. The *longest* orbit of the three terrestrial planets is 47 days, shorter than Mercury's by half, and the two others orbit in less than a week. In other words, they are magma balls. Not a likely system for organisms, shared or not. The fourth is a gas giant, again, not likely. All that "super Earth" means is that their diameters and masses are *roughly* equivalent to ours, but roughly can mean five times our surface gravity. They don't have oceans and atmospheres; don't assume too much.
PhotonX
5 / 5 (6) Jul 30, 2015
If they were transmitting any messages from there, we could see their radio noise by now.
And close enough that the signals wouldn't be lost in the noise. But they're not, because they are lifeless.
.
By 'three Earths' you mean three habitable worlds with stable atmosphere and liquid water?
No?
Then the article should be titled "Astronomers find star with three planetary bodies".
Yes, I was sick of the "super-Earth" label the second time I heard it, and since far too many people jump to the conclusion of aliens sitting on beaches sipping alien Mai Tais when they hear either "super-Earth" (or "habitable zone"), I'd just as soon see the phrase disappear all together. What's wrong with "terrestrial exoplanet"?
.
.
IronhorseA
5 / 5 (2) Jul 30, 2015
"By comparison, the closest star to our Sun is three light years away, and the second six light years."

I think they need to proofread that first distance ;P
NIPSZX
4 / 5 (3) Jul 30, 2015
I like the name: HD219134b. By the time we explore the planet, it's name will still be googleable because of the complexity.
Enthusiastic Fool
5 / 5 (3) Jul 31, 2015
For those curious about the star's luminosity and mass I found it under a different designation in plain English vs technical language from an academic catalog.

https://en.wikipe.../HR_8832

If they were transmitting any messages from there, we could see their radio noise by now.


Depending on when "they" started transmitting. If it was 17 years ago then nope. Although I doubt its a system conducive to life with those close orbits and stellar mass. Cue Jeff Goldblum "Life finds a way."
Osiris1
1 / 5 (4) Jul 31, 2015
Folks, like PhotonX there, consider that the central star is a DWARF so even that 47 day orbiter may qualify. However the other thing to consider is tidal locking. These may have cold nightsides, or maybe temperate ones who knows in certain zones. if really old than life is certainly there in some form or other. It will turn out that most life comes to worlds from space...panspermia. Life is also practical, so sentient critters will likely look a bit like us.

That said, we WILL be dealing with these and other blokes all over our local group sooner than most folks think. Exolife has a way to come here, so someone found out how and others too. Soon we will as well. Let us hope for our self satisfied bigoted smug souls that they are benevolent. That is in plain Sci-Fi..more like the Vulcans than the Klingons...or the Borg..

We will likely 'Borg' ourselves one day as we play with our body programming and add 'enhancements'. I am so not the first to think so.
Torbjorn_Larsson_OM
5 / 5 (3) Jul 31, 2015
Nice!

- At ~1.6 Earth masses, right in the transition region from superearths to minineptunes, there is a 50+ likelihood for it being terrestrial according to Kepler data. So both lucky and confirming.

- Another solar system analog, with terrestrials in the inner system and gas giants at several AU in the outer.

@Manfred: "By 'three Earths' you mean three habitable worlds with stable atmosphere and liquid water?"

No. It means it isn't an ice or gas giant (neptune or jupiter) but has a scanter non-H atmosphere. The transition region in between is a gray area depending on the system history, but it starts somewhere around 5 Earth masses and end up somewhere @ 10-15 (suspected core size for jupiters).
Torbjorn_Larsson_OM
5 / 5 (5) Jul 31, 2015
@Osiris: Technically our own star is a dwarf too, despite being among the most massive 5 % of stars (IIRC). A K star is just the smaller class down from our G star. See the figure and classification here: https://en.wikipe...fication
ColKlink
1 / 5 (6) Jul 31, 2015
No Proof. Just an animation, not science.
Enthusiastic Fool
5 / 5 (3) Jul 31, 2015

Bored napkin math time
I couldnt find the orbital radius for HD219134b online anywhere so I had to use the mass and period because I wanted to know things.
Using Kepler's Law of Periods and solving for...after getting a different answer 3 or 4 times I found a calculator (http://www.1728.o...r3a.htm)
Period ~ 3 days
Combined Mass ~ 0.7940135 Sol Mass (there's uncertainty here)
Orbital radius = 5,639,700km
Stellar Radius = .8 * Solar Radius = 556,400 km (https://en.wikipe...HR_8832)
Planet Radius = 1.6 Earth Radius = 10,200 km
Which if I mathed properly(lol maybe) means that it orbits only 5,073,100 km above the star with some assumptions about shapes of orbits and planet

Math Fails? to be Continued!
Enthusiastic Fool
5 / 5 (3) Jul 31, 2015
Continued Adventures in American Education System!

Sun Luminosity(L0) = 3.846*10^26 Watts (https://en.wikipe...inosity)
HR_8832 Luminosity(L1) = L0 *.28 (https://en.wikipe...HR_8832)
L1= 1.07688×10^26 Watts
Flux = L1/4πd^2 (https://www.e-edu...p4.html)
d is distance from light source so 5.073*10^9m
Flux = 332,987 W/m^2
Compared to Earth's Mean Flux of ~1,379 W/m^2 (solar constant)
Wolfram Alpha also tells me Temp of Black Body with this radiant excitance is 1557K
Also that it's ~36 x the average solar irradiance on Mercury

"Yeah man, but it's a dry heat" ~Corporal Hudson, Aliens(1986)
viko_mx
1 / 5 (3) Aug 01, 2015
For the calculation of mass of given star the official theory about the formation and evolution of stars use its luminosity and the spectrum of light coming from it. But this theory can not predict the activity of our own star the sun which tells us that is not very objective. The main problem is that physical models which are used to discribe the proceses in the cores of the stars and the structure of stars at all, can not be checked by experiments and the direct observations are impasible. The remain option is computer simulations which use the method of trial and error to guess the real physical processes in the stars which is not very sicentific aproach. It is obvious that the fundamental processes in our physical reality are inaccessible to us. So such kind of calculations are not more than guessing and can be too far from reality.
TechnoCreed
4.5 / 5 (2) Aug 02, 2015
@Enthusiastic Fool

Enthused by your math time!
I found an arXiv preprint on the subject: http://arxiv.org/...07.08532
Orbital radius (page 7): 0.0382AU (eccentricity e=0.0 almost perfectly circular) = 5.715*10^9m. (5.715-5.640)/5.715 a 1.3% difference from your estimation; that is impressive.
Stellar radius (page 4): 0.778 solar = 5.41*10^8
Effective stellar temperature (page 4): 4699K
Stellar luminosity using L= 4 πR² σT⁴: 1.017*10^26 joules / second
Energy flux at HD219134b using F=L/ (4πd²): 247818 W/m² note that you do not have to subtract the solar radius; the energy source is assumed to be punctual.
As for the equilibrium temperature (page 11): under 800 (Celsius I presume). I will explain.

Cont.
TechnoCreed
5 / 5 (2) Aug 02, 2015
...

-The energy flux is not received evenly by the surface because it is a sphere.
-The whole planet radiates back the energy it received.
Because the planet is a sphere not a disk, the energy it receives from the star is equal to 2/3 of the hemisphere facing the star, minus the reflected energy (Bond albedo). I do not know what number they used for the albedo but since the planet is presumed to be high in magnesium silicate let me propose 0.15. Also since the emissivity of planets is not perfect let me propose 0.9.

Cont.
TechnoCreed
5 / 5 (2) Aug 02, 2015
...

Like I wrote earlier the energy is received by 2/3 of the hemisphere facing the star, but it represent only 1/3 of the surface of the whole planet so.
(Flux – (Flux * albedo)) / 3 = Energy that is going to be radiated by HD219143b = 70215W/m²
If you look at the results given by 70215W/m² with 0.9 emissivity, you get 1083K = 809.9°C and that closely concur with the graph on page 11. http://www.wolfra....eps_0.9
This is the equilibrium temperature but a planet so close to its star will be in gravity lock so, off course the hemisphere permanently facing the star will be much hotter and the hemisphere permanently in the dark will be much colder.
Enthusiastic Fool
5 / 5 (2) Aug 02, 2015
Yeah, I knew the flux wasn't perfect but I felt like it would take some calculus to get a real handle on the spherical surface. Thanks for the followup. I accidentally 4'd your first post after I read them all in a rush to 5 them. Thanks again! I like to know things about things and sometimes the articles and news releases don't have it. Sorry for the 4.
Enthusiastic Fool
5 / 5 (2) Aug 02, 2015
I should add that at the beginning of the math time I had a lot of things I didn't know I didn't know so I had to learn about some things to figure out what I wanted to know. I'm glad everything wasn't completely blown apart by someone more seasoned.
Rumsfeld's "Unknown Unknowns"
TechnoCreed
5 / 5 (1) Aug 02, 2015
I should add that at the beginning of the math time I had a lot of things I didn't know I didn't know so I had to learn about some things to figure out what I wanted to know. I'm glad everything wasn't completely blown apart by someone more seasoned.
Rumsfeld's "Unknown Unknowns"

It was all very good, especially for the orbital radius where you were spot on. For the temperature of the planet, my attempt is highly speculative; I do not know the specifics of their method so my explanations can be somewhat off (I hope not). Keep on doing that, your comments are enjoyable and refreshing.
EnricM
not rated yet Aug 03, 2015
These 3 earths may have shared organisms blasted off one or more of their surfaces by asteroids strikes. If, from this they all developed different forms of life independently any intelligent life in that system may have a wildly different view of life in the universe to that here on Earth. Such a thing may have massively accelerated their race for space technology or even just simple things like telescopes and spectrometers.


What a setup for a Sci-Fi novel (or a whole series), Asimov would have loved it!

TechnoCreed
5 / 5 (1) Aug 16, 2015
I have to revise my comment of August 2nd.

I misread the temperature chart of page 11 on http://arxiv.org/...32v1.pdf You have to correlate the colour of the symbolized planet from the graph on the left with the temperature scale on the right. The pale blue colour of the symbol put it at around 1000K (not Celsius as I said before).

tbc.
TechnoCreed
5 / 5 (1) Aug 16, 2015
...

The stellar energy flux received by the planet relates only the cross section of the planet http://scied.ucar...alculate So we end up with Energy flux at HD219134b / 4 = blackbody temperature of the planet: 247818W/m² / 4 = 61954.5 If we plug that number on WolframAlpha the result is 1022K http://www.wolfra...perature Of course, we could plug some numbers for albedo and emissivity but it would be wildly speculative.

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