Sunday, August 28, 2016
Proxima Centauri b, The Exoplanet Next Door
When I was in high school (mumble) years ago, our zoology teacher was a bit of a science fiction buff, which gave her extra credit points in the eyes of a science fiction loving teenager. She set us one assignment to write about organisms on a tidally locked world. A key intersection of my twin loves of biology and astronomy, I turned in a fairly ummm...average assignment none the less, about burrowing animals on the dessert like sunny side of the world (I didn't think much about the atmospherics and hot pole/cold pole heat transfer).
This was all brought back by the announcement of a planet orbiting Proxima Centauri. Proxima Centauri is part of the triple star system Alpha Centauri. Alpha A and B are orange sun-like stars, but Proxima is a red dwarf orbiting somewhat distant from the other two.
 |  |
| The sky as seen from the southern hemisphere and hour and a half after sunset. Proxima Centauri is almost mid way between Riget Kent (alpha Centauri) and the dim star alpha Circinus off to the left. Click to embiggen | A binocular field view of the location of Proxima Centauri. Proxima is too dim (magnitude 11) to be seen in binoculars, but is visible intelescopes and long duration exposures. But is hard to tell from the other stars. Click to embiggen. |
The planet around Proxima is both "earth-like" and in the habitable zone. This is particularly exciting. Proxima is only 4.26 light years away, so in principle future instruments might be able to resolve it. If we are really lucky, the planet will transit its sun, so we can get some ideas about its diameter and atmosphere without new instruments.
As well, Proxima Centauri is the closest star to us, only a hop skip and a jump galactically speaking. To be sure, the technical challenge is enormous. Our current speediest spacecraft, Voyager 1 and New Horizons, woul take on the order of 8,000 years to get there. These craft travel at only around 0.005% of the speed of light, a recent proposal for a fleet of "starchips"; postage sized spacecraft carried on light salis, could reach 20% of light speed and get to Proxima b in a lifetime (including development).
The challenges of such a spacecraft are enormous, but not insurmountable. It will be very interesting to see what the next decade brings.
"Earth like" merely means it is small and rocky, "habitable zone measn nothing more than it is in the region around the star that liquid water can possibly exist on. But as a reminder, both Venus (searing hell) and Mars (frozen wasteland) are also (just) in the Sun's habitable zone. Whether liquid water exists on the world depends on if it has an atmosphere, and how dense it is. The occasional flares from the star, more powerful than our solar flares, will be a challenge to atmospheric stability, let alone life.
I have as usual made a Celestia file for the system. Original paper here. Copy the data here to a plain text file (Proximab.ssc) and copy the file to the Celestia extras folder.
=======================================8<==cut===8<===Proximab.ssc=======================================================
"b" "Proxima"
# Earth-like world that orbits the red dwarf star Proxima Centauri, the closest star to the Solar system
# Nature 536, 437–440 (25 August 2016) doi:10.1038/nature19106
# http://www.nature.com/nature/journal/v536/n7617/full/nature19106.html
{
Texture "venussurface.*"
# Using Venus as it is close to the leading edge of the habitable zone.
Mass 1.27 # M.sin(i) = 1.27 (1.10-1.46)
Radius 6300 # 1.27 Earth Mass radius a guess
#InfoURL "http://en.wikipedia.org/wiki/Alpha_Centauri_Bb"
EllipticalOrbit {
Period 0.0306251
SemiMajorAxis 0.0485
Eccentricity 0.0 #fixed
ArgOfPericenter 310 #from paper
Inclination 90.0322 #guess
#MeanAnomaly 271
}
# likely to be in captured synchronous rotation
}
AltSurface "limit of knowledge" "Proxima/b"
{
Texture "venussurface.*"
OverlayTexture "ganymede-lok-mask.png"
}
}
===================================8<==cut===8<===================================================================
Labels: celestia, exoplanet, extrasolar planet
Sunday, July 26, 2015
Celestia Files for Kepler 452b (the "so called" Earth 2.0)
Friday's announcement from the Kepler mission of the discovery of Kepler 452b had the media galvanised, with some calling it "Earth 2.0".
Kepler 452b is earth-like, and in a habitable zone, but that doesn't meant that it is Earth's twin. Similarly, not being Earth's twin does not make it disappointing.
Kepler-452b is in the habitable zone of it's star, with a radius 1.6 times that of Earth (technically making it a super Earth). While there is a lot of to-do about habitable zones, it simply means the zone where liquid water can exists on a planets surface. Other factors may be involved in habitability too. Mars is in our habitable zone, but was too small to hold on to a substantial atmosphere, and is now a freezing desert.
As of this discovery there are 13 earth-like worlds orbiting stars in their habitable zomes, and Kepler-186f is one that is closer in size to Earth than Kepler 452b. However, all but Kepler-452b orbit smaller, cooler stars and most are tidally locked to their sun (Kepler-186f orbits roughly where Mercury would be in our solar system, but because its sun is a cool red dwarf, it is not baking hot).
Kepler-452b orbits a sun-like G2 star, and has a year of 385 days, failry similar to our 365 days (all the others are much shorter, as they are closer in).
We don't know if Kepler-452b is a rocky world like our own, or a water world, however, it is the first time we have found an earth-like world around a sun that is the near twin of our own. Technically, it is quite difficult for find these kinds of planets (finding planets that have short years around dim cool stars is much easier) and gives us hope that we can find more of them in the near future.
Once again I've made Celestia files for the system. One for the star (which isn't in the default files) and one for the planet.
As usual, copy the data here to plain text files (Kepler452.stc and Kepler452b.ssc), copy both of the files to the Celestia extras folder. The star is around 1400 lightyears away in Cygnus, so in the Celestia star browser, you will have to show around 500 stars to see Kepler-452 in the list. You can find the paper from which I took the data here.
===============Kepler452.stc===============================
#Kepler survey DISCOVERY AND VALIDATION OF Kepler-452b
# The Astronomical Journal 150 (2): 56. doi:10.1088/0004-6256/150/2/56
"Kepler-452:2MASS 19440088+4416392:2KOI-7016.01:KIC 8311864"
{
RA 296.0042
Dec 44.2775556
Distance 1400 # light years from published data
SpectralType "G2"
AppMag 13.4
Radius 772005 # in km, 1.11 Sun radii
}
========================================================
===============Kepler452b.ssc=========================================
"b" "Kepler-452"
# earth like, possibly water world
{
Texture "exo-class4.*"
NightTexture "exo-class4night.*"
Mass 5 # M.sin(i) = 5 Earth, from paper
Radius 10400 # 1.63 Earth radi, from paper
#InfoURL "http://en.wikipedia.org/wiki/Kepler-452b"
# The Astronomical Journal 150 (2): 56. doi:10.1088/0004-6256/150/2/56
EllipticalOrbit {
Period 1.054364
SemiMajorAxis 1.046
Eccentricity 0.02
ArgOfPericenter 267 #guess
Inclination 89.806
#MeanAnomaly 271
}
}
AltSurface "limit of knowledge" "Kepler-452/b"
{
Texture "venussurface.*"
OverlayTexture "ganymede-lok-mask.png"
}
================================================================
Labels: celestia, exoplanet, extrasolar planet
Sunday, June 30, 2013
Three Exoplanets in a Habitable Zone? The Gliese 667 C System in Celestia
 |  |
| Gliese 667 C f (Exoplanet names in triple star systems are confusing) looking back towards it's primary (Gliese 667 C) and the binary it orbits (Cliese 667 A and B). Also visible are several of the other planets in the system. Visualised in Celestia. Click to embiggen. | The Gliese 667 C system. I have tilted the orbital plane sightly so that all three stars in the triple star system can be seen. |
Our search for extrasolar planets keeps turning up science-fiction worlds! The latest is a planetery system around one star in a triple star system that hosts not one, but three planets in its habitable zone (c, f [illustrated above] and e).
We already knew that there were three planets around Gliese 667, but longer data collection and reanalysis found more of them.
While there is a lot of to-do about habitable zones, it simply means the zone where liquid water can exists on a planets surface. Other factors may be involved in habitability too. Mars is in our habitable zone, but was too small to hold on to a substantial atmosphere, and is now a freezing desert. The M star these planets revolve around is potentially a flare star, with powerful solar eruptions that may make life difficult on these planets. We also don't know if they are rocky worlds of water worlds.
Still, the growing inventory of stars with terrestrial style planets in their habitable zones suggests that the possibility of life on other worlds is not remote.
The ESO press release is here, and nice backgrounders from the Universe Today and Space.com. Once again I've made Celestia files for the system.
As usual, copy the data here to a plain text file (GJ667.ssc), copy the file to the Celestia extras folder. Celestia already has Gliese 667 triple star system, so you don't need to have a star definition file. The images you get from Celestia look a bit different to the artists interpretations in the press release, in part because of the way the stars and planets are rendered in Celestia, and in part because of how the stars orbit is defined. But it will still give you a good feel fro the system.
I'll have to update my Celestia Exoplanet Tour as well.
===============GJ1667.stc======================================
"b" "Gliese 667 C"
# Neptune like world
# All data from original paper http://www.eso.org/public/archives/releases/sciencepapers/eso1328/eso1328a.pdf
{
Texture "exo-class4.*"
NightTexture "exo-class4night.*"
Mass 5.94 # M.sin(i) = 5.94 Earth
Radius 12181.98 # 1.91 Earth radii, guess
#InfoURL "https://en.wikipedia.org/wiki/Gliese_667_Cb"
EllipticalOrbit {
Period 0.019713845
SemiMajorAxis 0.050432
Eccentricity 0.112
ArgOfPericenter 267 #guess
Inclination 30 #greater than 30 actually, but no clear figure
#MeanAnomaly 271
}
# likely to be in captured synchronous rotation
}
AltSurface "limit of knowledge" "Gliese 667 C/b"
{
Texture "extrasolar-lok.*"
}
"c" "Gliese 667 C"
# Venus-like world maybe, on edge of habitable zone
{
Texture "venussurface.*"
# Using venus although it may be a water world
Mass 3.9 # M.sin(i) = 3.9 Earth
Radius 11480.4 # 1.8 Earth radi, from paper
#InfoURL "https://en.wikipedia.org/wiki/Gliese_667_Cc"
EllipticalOrbit {
Period 0.076995587
SemiMajorAxis 0.12507
Eccentricity 0.001
ArgOfPericenter 267 #guess
Inclination 30
#MeanAnomaly 271
}
}
AltSurface "limit of knowledge" "Gliese 667 C/c"
{
Texture "extrasolar-lok.*"
}
"d" "Gliese 667 C"
# Neptune like world
{
Texture "exo-class4.*"
NightTexture "exo-class4night.*"
Mass 10.4 # M.sin(i) = 10.4 Earth
Radius 17539.5 # 2.75 Earth radii, guess
#InfoURL "https://en.wikipedia.org/wiki/Gliese_667_Cd"
EllipticalOrbit {
Period 0.252131656
SemiMajorAxis 0.2758
Eccentricity 0.19
ArgOfPericenter 267 #guess
Inclination 30
#MeanAnomaly 271
}
# likely to be in captured synchronous rotation
}
AltSurface "limit of knowledge" "Gliese 667 C/d"
{
Texture "extrasolar-lok.*"
}
"e" "Gliese 667 C"
# earth like world
{
Texture "venussurface.*"
# Using venus although it may be a perfectly earth-like world
Mass 2.68 # M.sin(i) = 2.68 Earth, upper limit of theoretical range
Radius 9567 # 1.5 Earth radii,
#InfoURL "https://en.wikipedia.org/wiki/Gliese_667_Ce"
EllipticalOrbit {
Period 0.170471395
SemiMajorAxis 0.212
Eccentricity 0.001
ArgOfPericenter 267 #guess
Inclination 30
#MeanAnomaly 271
}
}
AltSurface "limit of knowledge" "Gliese 667 C/e"
{
Texture "venussurface.*"
OverlayTexture "ganymede-lok-mask.png"
}
"f" "Gliese 667 C"
# earth like world
{
Texture "ganymede.*"
# Using Ganymede as it may be giant water world
# NightTexture "gasgiantnight.jpg"
Mass 1.94 # M.sin(i) = 1.94 Earth theoretical maximum
Radius 9567 # 1.5 Earth radii,
#InfoURL "https://en.wikipedia.org/wiki/Gliese_667_Cf"
EllipticalOrbit {
Period 0.106998653
SemiMajorAxis 0.15575
Eccentricity 0.001
ArgOfPericenter 267 #guess
Inclination 30
#MeanAnomaly 271
}
}
AltSurface "limit of knowledge" "Gliese 667 C/f"
{
Texture "ganymede.*"
OverlayTexture "ganymede-lok-mask.png"
}
"g" "Gliese 667 C"
# Neptune like world
# All data from original paper
{
Texture "exo-class4.*"
NightTexture "exo-class4night.*"
Mass 4.41 # M.sin(i) = 4.41 Earth
Radius 12181.98 # 1.91 Earth radii, guess
#InfoURL "https://en.wikipedia.org/wiki/Gliese_667_Cg"
EllipticalOrbit {
Period 0.68861018
SemiMajorAxis 0.5389
Eccentricity 0.107
ArgOfPericenter 267 #guess
Inclination 30 #greater than 30 actually, but no clear figure
#MeanAnomaly 271
}
# likely to be in captured synchronous rotation
}
AltSurface "limit of knowledge" "Gliese 667 C/g"
{
Texture "extrasolar-lok.*"
}
============================end========================
Labels: celestia, exoplanet, extrasolar planet
Saturday, April 20, 2013
Kepler-62 and Kepler-69, a Bonanza of Exoplanets in the Habitable Zone.
 |  |
| The Kepler-62 system, simulated in Celestia, click to embiggen. | The view looking from the Super-Earth Kepler-62e, looking to the Inner solar system and the Water World 62f, the smallest world currently known in a habitable zone, beyond. Simulated in Celestia, click to embiggen. |
The plethora of exoplanets pouring out of the Kepler mission keeps amazing me. As you know, I'm quite an exoplanet fan, but I just can't keep up with the discoveries. As of today there are 866 confirmed exoplanets, and Kepler has 2,740 (yes, you read that right) planetary candidates that need to be worked through and confirmed.
The latest batch are the systems Kepler-62 and Kepler -69. Kepler-62 hosts 5 planets, and Kepler-69 two. Gone are the days when exoplanets were all Super-Jupiters or Jupiter sized, we are picking up lots of Terrestrial sized planets now (even if they are mostly Super-Earths).
Importantly, both these systems host planets in their respective habitable zones. Kepler-62 has two planets in its habitable zone and Kepler-69 has one. Kepler 62-f is the smallest known world in a habitable zone, and Kepler 69-c is the smallest planet in the habitable zone of a sun-like star (Kepler 62 is substantially smaller and cooler than the Sun).
While these worlds are similar in size to Earth (although bigger), it looks like the Kepler 62 planets are Water Worlds, occupied by a global ocean rather than having continents like Earth.
As well, Kepler-62-c is the smallest exoplanet found yet, about the size of Mars (but much hotter).
For more detailed discussion of the meaning of these exoplanets see the Kepler press release (with link to the published paper) and this Australian ABC report. Nancy Atkinson at Universe today has a nice image and animation roundup of the new systems.
Me, what can I contribute? As usual I've made Celestia files. I've just done the Kepler-62 system, I'll do Kepler-69 later. One for the star (which isn't in the default files) and one for the planet.
Copy the data here to plain text files (Kepler62.stc and Kepler62Planets.ssc), copy both of the files to the Celestia extras folder. The star is around 1200 lightyears away in Lyra, so in the Celestia star browser, you will have to show around 500 stars to see Kepler-62 in the list.
I'll have to update my Celestia Exoplanet Tour as well.
===============Kepler62.stc======================================
#Kepler survey
"Kepler-62:2MASS J18525105+4520595:KIC 9002278"
{
RA 283.2125
Dec 45.3497
Distance 1200 # light years from published data
SpectralType "K2V"
AppMag 14.0
}
=======================================================
==================Kepler62Planets.ssc============================
"b" "Kepler-62"
# Neptune like world?
{
Texture "exo-class4.*"
NightTexture "exo-class4night.*"
Mass 9 # M.sin(i) = 9 Earth
Radius 8355.18 # 1.31 Earth radi, from paper
#InfoURL "http://en.wikipedia.org/wiki/Kepler-62b"
EllipticalOrbit {
Period 0.015646374
SemiMajorAxis 0.0553
Eccentricity 0
ArgOfPericenter 267 #guess
Inclination 89.2
#MeanAnomaly 271
}
# likely to be in captured synchronous rotation
}
AltSurface "limit of knowledge" "Kepler-62/b"
{
Texture "extrasolar-lok.*"
}
"c" "Kepler-62"
# Mercury-Like world
{
Texture "mercury.*"
Mass 4 # M.sin(i) = 4 Earth
Radius 3444.12 # 0.54 Earth radi, from paper
#InfoURL "http://en.wikipedia.org/wiki/Kepler-62c"
EllipticalOrbit {
Period 0.034062959
SemiMajorAxis 0.0929
Eccentricity 0.0
ArgOfPericenter 267 #guess
Inclination 89.7
#MeanAnomaly 271
}
# likely to be in captured synchronous rotation
}
AltSurface "limit of knowledge" "Kepler-62/c"
{
Texture "extrasolar-lok.*"
}
"d" "Kepler-62"
# Neptune like world
{
Texture "exo-class4.*"
NightTexture "exo-class4night.*"
Mass 14 # M.sin(i) = 14 Earth
Radius 12437.1 # 1.95 Earth radi, from paper
#InfoURL "http://en.wikipedia.org/wiki/Kepler-62d"
EllipticalOrbit {
Period 0.049729669
SemiMajorAxis 0.120
Eccentricity 0.0
ArgOfPericenter 267 #guess
Inclination 89.7
#MeanAnomaly 271
}
# likely to be in captured synchronous rotation
}
AltSurface "limit of knowledge" "Kepler-62/d"
{
Texture "extrasolar-lok.*"
}
"e" "Kepler-62"
# earth like, possibly water world
{
Texture "exo-class4.*"
NightTexture "exo-class4night.*"
Mass 36 # M.sin(i) = 36 Earth, upper limit of theoretical range
Radius 10268.58 # 1.61 Earth radi, from paper
#InfoURL "http://en.wikipedia.org/wiki/Kepler-62e"
EllipticalOrbit {
Period 0.335072935
SemiMajorAxis 0.427
Eccentricity 0.0
ArgOfPericenter 267 #guess
Inclination 89.98
#MeanAnomaly 271
}
# likely to be in captured synchronous rotation
}
AltSurface "limit of knowledge" "Kepler-62/e"
{
Texture "venussurface.*"
OverlayTexture "ganymede-lok-mask.png"
}
"f" "Kepler-62"
# earth like world
{
Texture "ganymede.*"
# Using Ganymede as it may be giant ice world
# NightTexture "gasgiantnight.jpg"
Mass 35 # M.sin(i) = 35 Earth theoretical maximum
Radius 8992.98 # 1.41 Earth radi, from paper
#InfoURL "http://en.wikipedia.org/wiki/Kepler-62f"
EllipticalOrbit {
Period 0.731790854
SemiMajorAxis 0.718
Eccentricity 0.0
ArgOfPericenter 267 #guess
Inclination 89.9
#MeanAnomaly 271
}
# likely to be in captured synchronous rotation
}
AltSurface "limit of knowledge" "Kepler-62/f"
{
Texture "ganymede.*"
OverlayTexture "ganymede-lok-mask.png"
}
==============================================================
Labels: celestia, exoplanet, extrasolar planet
Wednesday, December 19, 2012
Tau Ceti has Planets? maybe even an Earth-Like One in a Habitable Zone.
If you go out at around 10 pm tonight (or over the next week or so) and look north, you will see a unprepossessing star (magnitude 3.5) about 11 hand-spans up from the horizon. This is the star Tau Ceti.
A mere 12 light years away and a close twin of our sun, Tau Ceti has been the focus of many science fiction stories based on imagined planets.
But today it was announced that, like our neighbours Alpha Centauri and Epsilon Eridani, Tau Ceti may have real planets, Earth-like ones, with one possible world in Tau Ceti's habitable zone.
The Earth-likeness may be a bit strained, the planets have periods of 13.9, 35.4, 94, 168, and 640 days and minimum masses of 2.0, 3.1, 3.6, 4.3, and 6.6 M earth, respectively. It's the M earth 4.3 planet with a 168 day orbit which is in the habitable zone (that means its mass is 4.3 times that of Earth, it may be a water world rather than a rocky world). I'll make a Celestia file after New Year.
Note the "may", which appears to have been dropped from many press releases. The planets have been uncovered by an international team of astronomers using clever statistical techniques on 14 years of observational data. the signals of these planets have been sifted from the years of noise. Their technique is a clever one, and has the potential to uncover more Earth-like systems, but requires independent confirmation before we get too excited.
The preprint of the paper is here.The PDF of the preprint is here (warning, big). ABC science online reporting here, Astrobiology Magazine article here. PhysOrg news article here.
Labels: exoplanet, extrasolar planet
Thursday, October 18, 2012
Alpha Centauri B has a (red hot) Earth-sized Planet
Australian's can never look at the sky the same way again. When you go out tonight to look at the southern sky, you know that alpha Centauri, the red star in the iconic pointers, the pair of stars that point to the Southern Cross, has an Earth-sized world orbiting it.A hellish, red hot world, true. One that screams around it's sun (alpha Centauri B, alpha Centauri is a triple star system) in just over 3 days. It snuggles closer to its sun than Mercury does to ours and its surface is most likely covered in a magma ocean. Not the place that bright eyed pioneers would fly to in gleaming silver spaceships.
But its a world around one of the southern hemisphere's iconic and brightest stars. Sure we have something like 800+ confirmed planets around other stars, a fair few solar systems, and even one or two have planets in the hypothetical habitable zones of their suns.
But the vast majority are too dim to see with the unaided eye, or barely visible, and rejoice in names like GJ 1214b, Gleise 581 e, Upsilon Andromedae A and 55 Cancerii e.
Alpha Centauri Bb, simulated in Celestia with two of its three suns visible. In contrast alpha Centauri is bright, and part of an easily recognisable asterism. It looms large not only in the skies of the southern hemisphere, but also our fiction and imaginations.
In terms of our stepping stones into space, The Moon, Mars* and then alpha Centauri, the triple star system on our doorstep a little over 4 light years away, has loomed large. Alpha Centauri has featured heavily in science fiction too, and Pandora, the world of the Na'vi, orbits Alpha Centauri A. The new world orbits alpha Centauri B as mentioned above.
Could there be other planets in the alpha Centauri system, ones that are more like our familiar planets?
Certainly, although they may be hard to find. This new world (we have to think of a name for it, Mustafar is already taken, how about magmamare) was discovered by the slight doppler shift in its stars light as the planet tugged on its sun as it orbited.
This means in these kinds of searches its easier to find big things close to their suns (which explains why until recently most of the extrasolar planets we found were massive things bigger than Jupiter as close or closer than Mercury). To find a Jupiter- like world in a Jupiter like orbit, we would have to watch the system for 36 years (as we need to watch 3 orbits to make sure the signal is real).
So there's a real chance that there are other, more familiar worlds circling the alpha Centauri system, and you can bet people will be looking for them now.
Next time you go outside and look south at the pointers, you will now know that there is a world, out there, not of our solar system, that is tantalisingly just beyond our reach.
You can find the original paper describing the discovery here. A good discussion at Nature, and another good article at Centauri Dreams.
Once again I've made Celestia files for the system. As usual, copy the data here to plain text files (alphacentBb.ssc) and copy the file to the Celestia extras folder.
=====================8<=cut===================================
"b" "Rigel Kentaurus B"
# Earth like world around alpha centauri B
# Found by ESO HARP instrument
{
Texture "venussurface.*"
# Using venus although it may be a magma world
Mass 1.13 # M.sin(i) = 1.13 Earth
Radius 3844.5167 # 0.868 Earth radi, ballant guess
#InfoURL "http://en.wikipedia.org/wiki/Alpha_Centauri_Bb"
EllipticalOrbit {
Period 0.00885954
SemiMajorAxis 0.04
Eccentricity 0.0 #fixed
ArgOfPericenter 267 #guess
Inclination 88.8 #guess
#MeanAnomaly 271
}
# likely to be in captured synchronous rotation
}
AltSurface "limit of knowledge" "Rigel Kentaurus B/b"
{
Texture "venussurface.*"
OverlayTexture "ganymede-lok-mask.png"
}
}
=====================8<=cut===================================
*Venus, despite looking like Earth's twin, never seems to garner quite the same attention, perhaps because Mars is in the direction of out.
Wednesday, October 17, 2012
Breaking News! Earth-Like World around Alpha Centauri B
The ESO has announced the discovery of a (very hot) Earth-like world around the nearest known star system to Earth, Alpha Centauri.
The Bad Astronomers reaction here.
Next Big Future reaction here.
The Universe today reaction here.
More later.
The Bad Astronomers reaction here.
Next Big Future reaction here.
The Universe today reaction here.
More later.
Labels: exoplanet, extrasolar planet
Thursday, February 23, 2012
Not Kevin Costner's Water World (in Celestia)
GJ 1214b visualised in Celestia.I'm still continually amazed about what we find out about extrasolar planets, I know I shouldn't be, but I am.
Just finding these worlds is amazing enough, but for a couple of these worlds we know what's in their atmospheres. For a Neptune sized world 40 light years from us, GJ 1214b, it looks like it's a water world.
Weeellll sort a water world, according to a recently released paper, it's a hellish steam bath world, with perhaps 50% of it's atmosphere water vapour at a temperature of 230° Celsius (but see this paper as well, which is more suggestive of haze). The rest of the atmosphere is more likely hydrogen and helium. Of course, more onservation is needed, but it's amazing to think we can glimpse what this world is like from fleeting dips in a stars light.
Hubble press release here, and thoughtful commentary by the Bad Astronomer. Once again I've made Celestia files for the system. One for the star (which isn't in the default files) and one for the planet.
As usual, copy the data here to plain text files (GJ1214.stc and GJ1214b.ssc), copy both of the files to the Celestia extras folder. The star is around 950 lightyears away in Lyra, so in the Celestia star browser, you will have to show around 500 stars to see Kepler-20 in the list.
I'll have to update my Celestia Exoplanet Tour as well.
===============GJ1214.stc======================================
#Mearth Project
"GJ 1214"
{
RA 258.8292
Dec 4.9639
Distance 40 # light years from published data
SpectralType "M4.5"
AppMag 14.67
}
=======================================================
==================GJ1214b.ssc============================
"b" "GJ 1214"
# Neptune like world
# All data from original papers or URL
{
Texture "exo-class4.*"
NightTexture "exo-class4night.*"
Mass 6.55 # M.sin(i) = 6.55 Earth
Radius 17080.284 # 2.678 Earth radi, from URL
#InfoURL "http://en.wikipedia.org/wiki/GJ_1214_b"
#InfoURL "http://exoplanet.eu/star.php?st=GJ+1214"
EllipticalOrbit {
Period 0.004326842
SemiMajorAxis 0.014
Eccentricity 0.27
ArgOfPericenter 267 #guess
Inclination 88.8
#MeanAnomaly 271
}
# likely to be in captured synchronous rotation
}
AltSurface "limit of knowledge" "GJ 1214/b"
{
Texture "extrasolar-lok.*"
}
==============================================================
Labels: celestia, exoplanet, extrasolar planet
Sunday, February 12, 2012
The Kepler-20 Exoplanetary System in Celestia
 |  |
Left image: The Kepler-20 solar system, simulated in Celestia. Right image: Simulation of the view from orbit around Kepler-20e, with Kepler-20b visible in the sky. Click on an image to embiggen.
The Kepler-20 system made a bit of a splash back in December, when it was announced that the system, previously known to have three Neptune sized worlds in it, had two Earth-sized worlds in it.
And this time Earth-Sized actually Means Earth-Sized, with the planets Kepler-20e being 0.87 times the radius of Earth and Kepler-20f being 1.03 times the radius of Earth. The previously smallest world was 1.42 times Earth’s radius, and most of the "Super Earths" are much larger.
This report was an important demonstration that earth-sized worlds can be picked up by Kepler. Kepler 20 is a G8 star very similar to the Sun, but its solar system is crammed into a space inside Mercury's orbit. Kepler-20e would have a surface temperature hotter than 1000 degrees C, and Kepler-20f would be more Venus like.
The interesting thing is that these are almost certainly rocky worlds. Many exoplanetary systems have gas giants very close to the parent star, and the current thinking is that the Gas giant form far out in the developing solar system, then migrate inwards. This should expel any rocky worlds closer to the star. The fact the Kepler-20e and f have survived suggests that we may still find terrestrial worlds in some of these systems (Kepler-20e could have been an ice-world that migrated in and had its ocean boiled off, leaving a rocky core, but Kepler-20f is too far out to be a boiled down ice-world).
You can read the NASA press release here, and thoughtful commentary by the Bad Astronomer and Emily Lakdawalla. The paper just came out in the print copy of nature, so I've used this as an excuse to make Celestia files for the system. One for the star (which isn't in the default files) and one for the planet.
As usual, copy the data here to plain text files (Kepler-20.stc and Kepler-20-planets.ssc), copy both of the files to the Celestia extras folder. The star is around 950 lightyears away in Lyra, so in the Celestia star browser, you will have to show around 500 stars to see Kepler-20 in the list.
I'll have to update my Celestia Exoplanet Tour as well.
===============Kepler-20.stc======================================
#Kepler survey
"Kepler-20"
{
RA 287.7000
Dec 49.3386
Distance 945.9 # light years from published data
SpectralType "G8"
AppMag 12.423
}
==============================================================================
==================Keper-20_Planets.ssc=================================
"b" "Kepler-20"
# Neptune like world
# All data from original papers
{
Texture "exo-class4.*"
NightTexture "exo-class4night.*"
Mass 8.7 # M.sin(i) = 8.7 Earth
Radius 12181.98 # 1.91 Earth radi, from paper
#InfoURL "http://en.wikipedia.org/wiki/Kepler-20b"
EllipticalOrbit {
Period 0.0101
SemiMajorAxis 0.04537
Eccentricity 0.32
ArgOfPericenter 267 #guess
Inclination 86.50
#MeanAnomaly 271
}
# likely to be in captured synchronous rotation
}
AltSurface "limit of knowledge" "Kepler-20/b"
{
Texture "extrasolar-lok.*"
}
"c" "Kepler-20"
# Neptune like world
{
Texture "exo-class4.*"
NightTexture "exo-class4night.*"
Mass 16.1 # M.sin(i) = 16.1 Earth
Radius 19580.46 # 3.07 Earth radi, from paper
#InfoURL "http://en.wikipedia.org/wiki/Kepler-20b"
EllipticalOrbit {
Period 0.0297
SemiMajorAxis 0.0930
Eccentricity 0.4
ArgOfPericenter 267 #guess
Inclination 88.39
#MeanAnomaly 271
}
# likely to be in captured synchronous rotation
}
AltSurface "limit of knowledge" "Kepler-20/c"
{
Texture "extrasolar-lok.*"
}
"d" "Kepler-20"
# Neptune like world
{
Texture "exo-class4.*"
NightTexture "exo-class4night.*"
Mass 20.17 # M.sin(i) = 20.1 Earth
Radius 17539.5 # 2.75 Earth radi, from paper
#InfoURL "http://en.wikipedia.org/wiki/Kepler-20d"
EllipticalOrbit {
Period 0.21249
SemiMajorAxis 0.3453
Eccentricity 0.6
ArgOfPericenter 267 #guess
Inclination 89.570
#MeanAnomaly 271
}
# likely to be in captured synchronous rotation
}
AltSurface "limit of knowledge" "Kepler-20/d"
{
Texture "extrasolar-lok.*"
}
"e" "Kepler-20"
# earth like world
{
Texture "venussurface.*"
# Using venus although it may be a magma world
Mass 1.67 # M.sin(i) = 1.67 Earth, upper limit of theoretical range
Radius 3844.5167 # 0.868 Earth radi, from paper
#InfoURL "http://en.wikipedia.org/wiki/Kepler-20e"
EllipticalOrbit {
Period 0.0167
SemiMajorAxis 0.05073
Eccentricity 0.28
ArgOfPericenter 267 #guess
Inclination 87.50
#MeanAnomaly 271
}
# likely to be in captured synchronous rotation
}
AltSurface "limit of knowledge" "Kepler-20/e"
{
Texture "venussurface.*"
OverlayTexture "ganymede-lok-mask.png"
}
"f" "Kepler-20"
# earth like world
{
Texture "ganymede.*"
# Using Ganymede as it may be giant ice world
# NightTexture "gasgiantnight.jpg"
Mass 3.04 # M.sin(i) = 3.04 Earth theoretical maximum
Radius 6569.34 # 1.03 Earth radi, from paper
#InfoURL "http://en.wikipedia.org/wiki/Kepler-20f"
EllipticalOrbit {
Period 0.0536
SemiMajorAxis 0.11038
Eccentricity 0.32
ArgOfPericenter 267 #guess
Inclination 88.68
#MeanAnomaly 271
}
# likely to be in captured synchronous rotation
}
AltSurface "limit of knowledge" "Kepler-20/f"
{
Texture "ganymede.*"
OverlayTexture "ganymede-lok-mask.png"
}
==============================================================================
Labels: celestia, exoplanet, extrasolar planet
Saturday, September 17, 2011
Evolution News and Views Fails at Exoplanets Too
Evolution News and Views noticed my previous post, and wrote a little reply. Unfortunately for them they completely missed the point, that Dembski claimed "Darwinists" were making stuff up, when there was good theoretical and (indirect) observational evidence to be confident that planets abounded in the galaxy.
The 55 Cnc system (excluding the outermost planet), 55 Cnc e is marked by the red cross near the sun. The 55 Cne system has features similar to our solar system.
Instead, they chose to focus on whether the planets we have found are habitable, which was beside the point. Guillermo Gonzalez wrote a response for them, which included this:
Distribution of orbital periods of the currently discovered exoplanets. The pink bars are "Super Jupiters" and the yellow bars are Jupiter-like planets in Jupiter period orbits.
Well, that's sort of true, but deeply misleading. When we first started looking Super Jupiters were the norm. To explain why, and why this is no longer true, I'm going to digress for a moment to explain the main methods used to find exoplanets. The first is the radial velocity method. Here the slight wobbles produced in the position of a star by the gravitational tug of an orbiting planet are detected by Doppler shift.
In the transit method, the slight dimming in the stars light as the planet passes in front of it.
Naturally, the changes are very small, right at the limit of our ability to detect them. This means that bigger planets are easier to find than smaller ones, a big planet tugs more, and can block more light. Planets that are closer to their suns are also easier to find, big close worlds tug more, and can block more light.
Distribution of exoplanets distance from their suns. Red is "Hot Jupiters", Green is multiplanet systems and blue is Jovian planets at jovian orbits.
When we first found exoplanets, back in 1995, they were jaw-dropping hot super-Jupiters closer to their suns than Mercury and screaming around their suns in a handful of days! This was a big surprise, no one expected big planets to be that close. There were also lots of weird orbits (although some of these eccentric orbits turn out to be artifacts of the way multiple stars systems orbits sum up).
Finding solar systems like ours is rather difficult even given the limitations of the telescopes we are using (which will have great difficulty finding Earth sized worlds in the first place). For example, if you were looking at the Sun for Jupiter, you would have to watch for 12 years to detect it, and you would need to wait 24 years to confirm your detection. So it is no wonder that our explanet detections up until now have been dominated by massive planets orbiting closer to their suns then Mercury is to ours.
Now with Kepler, HARPS and MOST we are seeing a wider range of solar systems, although still biased away from Earth-like worlds and solar systems like our own you can see from the diagrams above that Super Jupiters no longer predominate, and we have more normal sized planets in more normal sized orbits predominating.
While the typical extasolar system is different from our own, with more Saturn and Neptune sized worlds (quite a few are closer in, but these are orbiting smaller suns, so their relative positions aren't to far off), the way Dr. Gonzales has written his piece suggests that the typical extrasolar system is hot Jupiters in eccentric orbits. Which they are not.
We are still getting weird ones, like the planet where it rains pebbles, but even with the gross under-sampling of Earth-like worlds in the current surveys; of the 677 official and 1270 still to be confirmed planets, 54 are in the habitable zone, and 4 are Earth-like (although they are "super -Earths"). When you use these (grossly underestimated) figures to estimate the number of terrestrial worlds in their stars habitable zone (around stable, long lived stars) you get between 50 million to 50 billion habitable worlds depending on the assumptions you make.
If you take the low end estimate, and factor in habitable exomoons (shades of Avatar), then you get a figure of roughly 100 million habitable environments per galaxy which can now be used to come up with an estimate of habitable worlds in the visible universe. The number works out to 1018, or 10 million trillion.
I'll let that number sink in a bit. Now, Dr.Gonzales has written that there is a lot of work going on understanding habitable zones, which there is, but he implies that it is all shrinking the habitable zones (which it isn't). As well, some old constraints (like having a large Moon to stabilise a worlds orbit) see to be less constraining than we thought).
Even with very conservative estimates, we still have more than enough worlds in the Habitable zones of stars of our Universe to make Dembski's original statement false. As well, we have seen how once again the Discovery Institutes members try to distort facts. The DI still fails at exoplanets.
(PS, NASA's big announcement was a planet orbiting a binary star, a bit like Tatooine, if Tatooine was a frigid gas giant. It could have a habitable Moon though.)
(PPS, I'm an amateur astronomer, not a professional, but I have been using the STEREO spacecraft images to hunt for exoplanets. Boy, do I suck at it. Other teams have found an exoplanet using this system though. I'm also a member of the Planet Hunters and search the Kepler data for planetary candidates)
The 55 Cnc system (excluding the outermost planet), 55 Cnc e is marked by the red cross near the sun. The 55 Cne system has features similar to our solar system.Instead, they chose to focus on whether the planets we have found are habitable, which was beside the point. Guillermo Gonzalez wrote a response for them, which included this:
The typical exoplanetary system is very different from our Solar System. Jovian planets are being discovered in very tight or highly eccentric orbits. Jovian planets in our Solar System are characterized by large nearly circular orbits. Our Solar System looks ever more like the exception, and it is exceptional in ways that are life friendly.
Distribution of orbital periods of the currently discovered exoplanets. The pink bars are "Super Jupiters" and the yellow bars are Jupiter-like planets in Jupiter period orbits. Well, that's sort of true, but deeply misleading. When we first started looking Super Jupiters were the norm. To explain why, and why this is no longer true, I'm going to digress for a moment to explain the main methods used to find exoplanets. The first is the radial velocity method. Here the slight wobbles produced in the position of a star by the gravitational tug of an orbiting planet are detected by Doppler shift.
In the transit method, the slight dimming in the stars light as the planet passes in front of it.
Naturally, the changes are very small, right at the limit of our ability to detect them. This means that bigger planets are easier to find than smaller ones, a big planet tugs more, and can block more light. Planets that are closer to their suns are also easier to find, big close worlds tug more, and can block more light.
Distribution of exoplanets distance from their suns. Red is "Hot Jupiters", Green is multiplanet systems and blue is Jovian planets at jovian orbits. When we first found exoplanets, back in 1995, they were jaw-dropping hot super-Jupiters closer to their suns than Mercury and screaming around their suns in a handful of days! This was a big surprise, no one expected big planets to be that close. There were also lots of weird orbits (although some of these eccentric orbits turn out to be artifacts of the way multiple stars systems orbits sum up).
Finding solar systems like ours is rather difficult even given the limitations of the telescopes we are using (which will have great difficulty finding Earth sized worlds in the first place). For example, if you were looking at the Sun for Jupiter, you would have to watch for 12 years to detect it, and you would need to wait 24 years to confirm your detection. So it is no wonder that our explanet detections up until now have been dominated by massive planets orbiting closer to their suns then Mercury is to ours.
Now with Kepler, HARPS and MOST we are seeing a wider range of solar systems, although still biased away from Earth-like worlds and solar systems like our own you can see from the diagrams above that Super Jupiters no longer predominate, and we have more normal sized planets in more normal sized orbits predominating.
While the typical extasolar system is different from our own, with more Saturn and Neptune sized worlds (quite a few are closer in, but these are orbiting smaller suns, so their relative positions aren't to far off), the way Dr. Gonzales has written his piece suggests that the typical extrasolar system is hot Jupiters in eccentric orbits. Which they are not.
We are still getting weird ones, like the planet where it rains pebbles, but even with the gross under-sampling of Earth-like worlds in the current surveys; of the 677 official and 1270 still to be confirmed planets, 54 are in the habitable zone, and 4 are Earth-like (although they are "super -Earths"). When you use these (grossly underestimated) figures to estimate the number of terrestrial worlds in their stars habitable zone (around stable, long lived stars) you get between 50 million to 50 billion habitable worlds depending on the assumptions you make.
If you take the low end estimate, and factor in habitable exomoons (shades of Avatar), then you get a figure of roughly 100 million habitable environments per galaxy which can now be used to come up with an estimate of habitable worlds in the visible universe. The number works out to 1018, or 10 million trillion.
I'll let that number sink in a bit. Now, Dr.Gonzales has written that there is a lot of work going on understanding habitable zones, which there is, but he implies that it is all shrinking the habitable zones (which it isn't). As well, some old constraints (like having a large Moon to stabilise a worlds orbit) see to be less constraining than we thought).
Even with very conservative estimates, we still have more than enough worlds in the Habitable zones of stars of our Universe to make Dembski's original statement false. As well, we have seen how once again the Discovery Institutes members try to distort facts. The DI still fails at exoplanets.
(PS, NASA's big announcement was a planet orbiting a binary star, a bit like Tatooine, if Tatooine was a frigid gas giant. It could have a habitable Moon though.)
(PPS, I'm an amateur astronomer, not a professional, but I have been using the STEREO spacecraft images to hunt for exoplanets. Boy, do I suck at it. Other teams have found an exoplanet using this system though. I'm also a member of the Planet Hunters and search the Kepler data for planetary candidates)
Labels: exoplanet, extrasolar planet
Friday, September 16, 2011
Kepler finds a World with Twin Suns
The Star Kepler16 B about to eclipse Kepler16 A as seen from Kepler 16 (A/B) b. Image simulated in Celestia.Well, it's now clear why representatives of Industrial Light and Magic (Lucas Films) were at the NASA press conference this morning. The Kepler team announced the finding of Kepler-16b, a world that circles two suns, like Tatooine from Star Wars.
Admittedly, Tatooine orbited two stars that were very like our sun, while Kepler 16-b sun's are mismatched dwarf red stars. Also, Kepler 16-b is about 2/3rds the size of Jupiter, like Saturn, and just outside it's habitable zone; more like Hoth or Bespin than the parched, rocky desert world of Tatooine.
Kepler 16 (AB) system face on.It's also not the first world in a multiple star system, although a white dwarf/pulsar system isn''t very Tatooine like. We've even found a planet in a triple star system as far back as 2005, but it is the first world that circles both stars, and both of which are at least notionally Sun-like. What does it mean overall? We originally thought that it would be difficult for planets to form around close binaries, that the dynamics of binary star formation would disrupt any protoplanets. Kepler 16 b shows that recognisable worlds can also form under these conditions, which greatly expands the number of stars which can have planets.
What does this mean for finding life? In this case Kepler 16 b is just outside the habitable zone, but a moon with a thick atmosphere might be warm enough for life. Another issue is whether the varying distances of the component suns would make planetary temperature swings too large for any form of complex life.
For Earth, the major driver of seasonal variation is the angle of inclination to the Sun, rather than the distance (northern hemisphere summer occurs at aphelion, when the earth is at it's furthest from the Sun, but Kepler 16 B comes closer and further from this world than Earth does to our Sun, and 20 day seasons could be interesting.
NASA's Kepler website has some good illustrations and animations, as well as some "Artists Concepts" with the press release. You can find more thoughts on this report at Universe Today, the Bad Astronomer, Greg Laden's blog and Dynamics of Cats. The original paper can be found here.
Of course, I've made a Celestia file. Two actually, one for the binary star system and one for the planet. I've had to guess the distance of the main star from the solar system barycenter, based on the illustration in et al., 2011, but the rest comes from the discovery paper except for the rotation period of the B component.
As usual, copy the data here to plain text files (Kepler16_binary.sts and Kepler16b.ssc), the copy both the files to the Celestia extras folder. The stars are 195 lightyears away, so in the Celestia star browser, you will have to show around 250 stars to see Kepler16 in the list. I'll have to update my Celestia Exoplanet Tour as well.
======================== Kepler16_binary.sts =========================
Replace Barycenter "Kepler16:2MASS 19161817+5145267:KIC 12644769" # replace the old star definition
{
RA 289.0750 # in degrees 19 16 18
Dec 51.7575 # in degrees +51 45 27
Distance 195.6981756 # in light years 60 pc
}
"Kepler16 A:2MASS 19161817+5145267 A:KIC 12644769 A" # Mass = 0.69 Sun masses
{
OrbitBarycenter "Kepler16"
SpectralType "K8V"
AppMag 12
Radius 451634 # in km, 0.6 Sun radii
EllipticalOrbit {
Period 0.1125 # P or T, in years
SemiMajorAxis 0.00496 # a, in AU (mass ratio MA/MB = 0.96/0.13)
Eccentricity 0.15944 #
Inclination 90.304 # in degrees
AscendingNode 0.0 # in degrees
ArgOfPericenter 263.464 # in degrees
MeanAnomaly 0.0 # in degrees
}
UniformRotation {
Period 842.4 # in hours, 35.1 days
}
}
"Kepler16 B:2MASS 19161817+5145267 B:KIC 12644769 B" # Mass = 0.33 Sun masses
{
OrbitBarycenter "Kepler16"
SpectralType "M4V"
AppMag 13
Radius 157456.08 # in km, 0.23 Sun radii
EllipticalOrbit {
Period 0.1125 # P or T, in years
SemiMajorAxis 0.22431 # a, in AU (mass ratio MA/MB = 0.96/0.13)
Eccentricity 0.15944 # guess, to be determined
Inclination 90.304 # in degrees
AscendingNode 0.0 # in degrees
ArgOfPericenter 0.0 # in degrees
MeanAnomaly 0.0 # in degrees
}
}
========================end======================================
=========================>8 Kepler16b.ssc >8==========================
"b" "Kepler16 A"
# Saturn-like world that orbits a binary star system, a bit Like Tatooine
{
Texture "exo-class4.*"
NightTexture "exo-class4night.*"
# Using Gas Giant
Mass 105.86 # M.sin(i) = 0.333 Jupiter
Radius 53890.6696 # 0.7 Jupiter radi, from paper
InfoURL "http://exoplanet.eu/planet.php?p1=Kepler-16+%28AB%29&p2=b"
EllipticalOrbit {
Period 0.626344263
SemiMajorAxis 0.7048
Eccentricity 0.0069
ArgOfPericenter 318
Inclination 90.0322
AscendingNode 0.003
MeanLongitude 106.51
#MeanAnomaly 271
}
# likely to be in captured synchronous rotation
}
AltSurface "limit of knowledge" "Kepler16 A/b"
{
Texture "extrasolar-lok.*"
}
===========================>8 cut >8============================
Labels: exoplanet, extrasolar planet, Kepler Space Telescope, spacecraft
Wednesday, September 14, 2011
The Discovery Institute Fails at Exoplanets
KOI-701.03, an as yet unconfirmed, Earth-like world probably in the habitable zone of its Sun. KOI-703.03 visualized in Celestia (click to embiggen).Still, despite coming hard on the heels of the 50 new exoplanets found by HARPS, the existing bonanza of Kepler worlds and discovering the atmospheric composition of some exoplanets, one can hardly suppress a thrill at the prospect of learning something new about the plethora of extrasolar worlds we have found.
One wonders how William Dembski feels after proclaiming in 1992:
"Dawkins, to explain life apart from a designer, not only gives himself all the time Darwin ever wanted, but also helps himself to all the conceivable planets there might be in the observable universe (note that these are planets he must posit, since no planets outside our solar system have been observed, nor is there currently any compelling theory of planetary formation which guarantees that the observable universe is populated with planets)"Three years later the first exoplanet was confirmed, and the current count stands at 677.
Exoplanets visualized at "Data is Beautiful" for Wired.It's not the first time a pundit has been wrong, after all the philosopher Auguste Comte claimed that we would never know the composition of the stars, yet 25 years later the spectroscope revealed the elements they were made of (and in 1814 Frauenhoffer had seen the spectral lines that would reveal the stars secrets when chemistry improved).
But it's not the fact the Dembski was wrong (or Paul Nelson, who quoted him approvingly in 1993), but the way that they were wrong. The claim is that "Darwinists" posited a plethora of worlds to fulfil the needs of evolutionary theory, without any strong evidence. Yet Dembski and company couldn't be more wrong.
The 55 Cnc system (excluding the outermost planet), 55 Cnc e is marked by the red cross near the sun.Note that Dembski says "nor is there currently any compelling theory of planetary formation which guarantees that the observable universe is populated with planets". You might think this hedges his bets a bit, with the qualifications "compelling" and "guarantees", but it doesn't
By the 60's the dominant theory of planetary formation was a variant of the nebular hypothesis, which with further modification became dominant in the 1970's.
It was abundantly obvious even in the 60's that the implication of this hypothesis was that planet formation would not be a rare event (for example the RAND corporation study "Habitable Planets for Man" published in 1964 used this model as a basis for estimating the number of stars with planets).
Then there was stellar rotation. In the solar system, most of the angular momentum is in the planets, and the sun has most of the mass but just a fraction of the angular moment momentum because during planet formation the momentum of the spinning protostellar disk is transferred to the planets. Most sun-like stars have angular momentum like the Sun's suggesting that the majority of these systems had planets.
Observations in the early 80's of dusty disks around young T-Tauri stars and then dust disks around stars like Beta Pictoris were in line with the nebula hypothesis and strengthened the case that planets were common.
George Wetherill's classic paper "The Formation and Habitability of Extra-Solar Planets" did not come out until 1996, but his work in 1988, 19989 and 1991 on planet formation made scientists confident that solar system equivalents were not rare in the galaxy.
Certainly, when Dawkins published "the Blind Watchmaker" in 1986, there was a compelling theory of planetary formation, along with astromomical observations which guaranteed that there would be planets around other suns. When Dembski wrote his words in 1992, astronomers were busy designing the very instruments that would reap a harvest of extrasolar planets just a few years later.
Dembski was trying to claim that "Darwinists" make things up to bolster their arguments. If Dembski had taken a few moments to read the astronomical literature, or even asked an astronomer, he could not have made his statement.
Based on the Kepler data of 2010, we can say that around 50% of Sun-like stars have planets, and there may be at least one million Earth-like planets in habitable zones in the Milky-Way alone. And that is probably an underestimate. Some good resources are the Exoplanet encyclopaedia, Exoplanet.org (with the exoplanet data plotter) and the Habitable Zone as well as my posts on exoplanets.
Saturday, September 10, 2011
And Meanwhile ...
... comet 213P van Ness has fragmented again, two new comets have been discovered and there is a new Nova in Scorpius.
Not to mention that GRAIL made it into orbit okay, and the newly discovered planet in a habitable zone. I just don't have time too keep up (I still have to process my images of C/2009 P1 Garrad and Vesta and the latest STEREO images).
Not to mention that GRAIL made it into orbit okay, and the newly discovered planet in a habitable zone. I just don't have time too keep up (I still have to process my images of C/2009 P1 Garrad and Vesta and the latest STEREO images).
Labels: comet, exoplanet, miscelaneous, news, nova
Tuesday, May 03, 2011
Want to see a Star with a Transiting Exoplanet?
55 Canceri is a dim, unprepossessing star in the constellation of Cancer. It's a double star, whose claim to fame is that the yellow, Sun-like star of the double is host to a solar system of at least 5 planets, one of the few stars with extensive planetary systems so far discovered.It's fame has now increased as transits of the innermost planet, 55 Cnc e, has been observed. This makes 55 Cnc the closest system with a transiting exoplanet, and also the only transiting system whose star is visible to the unaided eye (well providing you live in the country with dark skies).
If you head out tonight (well, tomorrow night. as 55 Cnc has set now as seen from Australia), around 8 pm and look north east, You will easily see the twins, Castor and Pollux. Just above and to the right is a very dim star, just above that is a dimmer star (suburban dwellers will need binoculars to see it) which is 55 Cnc.The planetary system was originally discovered by the radial velocity method, which fixes some parameters of the system.
)
The 55 Cnc system (excluding the outermost planet), 55 Cnc e is marked by the red cross near the sun.When the inner planet ,55 Cnc e, transits were observed, the radius of the exoplanet could be determined more precisely. It turns out to be a mere 1.6 times that of Earth, placing it as one of the smallest "Super Earths" yet discovered. With a mass of nearly 9 times that of Earth, it must be a rocky world, almost as dense as lead.
The orbit was also revised, it turns out the planet screams around it's sun in a year that lasts 18 hours. It's surface temprature, depending on whether it has an atmosphere or not, can range between 2100 and 2900 degrees C.
As always, I've created a Celestia file for 55 Cnc e. Celestia already has a file with the 55 Cnc system in it. If you wish, you can comment out the old 55 Cnc e data in exoplanets.ssc or replace the data with the following.
==================55Cnce.ssc===================================
"e" "HD 75732" # Rho1 Cnc A
{
Texture "venuslike.*"
NightTexture "venuslikenight.*"
Mass 8.57 # M.sin(i) = 8.57 earths
Radius 10396.14
InfoURL "http://arxiv.org/PS_cache/arxiv/pdf/1104/1104.5230v1.pdf"
EllipticalOrbit {
Period 0.002016503
SemiMajorAxis 0.01573
Eccentricity 0.07
# Inclination 90.0 # inclination is differnt from rest of system as measured with radial velocity
ArgOfPericenter 107
MeanAnomaly 181
}
# likely to be in captured synchronous rotation
}
AltSurface "limit of knowledge" "HD 75732/e"
{
Texture "extrasolar-lok.*"
}
=============================================================
The original paper is here, more commentary at Universe Today and Centauri Dreams.
Labels: celestia, exoplanet, extrasolar planet, unaided eye observation
Tuesday, February 22, 2011
And No, One in Two Stars Do NOT Have an Earth-Like Planet Around Them.
They have discovered the Kepler planet bonanza (somewhat late).
But, no, sorry. They have mangled the quite reasonable statement that one in every two sun-like stars may have planets per se by conflating planets with Earth-like planets (and Earth-like planets in the habitable zone). Only 54 of the 1200+ planets detected by Kepler were found to be in their stars habitable zone, and of those only two were roughly Earth mass (and a couple of Super Earths like KOI 702.03, visualized above) . There may be a lot more Earth-like planets out there, but not 50% of them having Earth-like worlds based on present data.
Labels: exoplanet, extrasolar planet, science communicators
Visualizing Exoplanets Part 2
Exoplanets visualized at "Data is Beautiful" for Wired.I have previously pointed you at some amazing visualizations of the Kepler Exoplanet data.
My friend Stuart has just alerted me to a stunning visualization at "Data is Beautiful", showing some of the most interesting and important exoplanets. The post also shows the step by step process of taking the data and building an infographic out of it, which is in itself ineteresting. A truly amazing piece of work (and one of my posts is referenced in it) and they make the spreadsheet they used to build the exoplanet graphic available to all.
Labels: exoplanet, extrasolar planet, science communicators
Thursday, February 10, 2011
Cool Visualization of the Kepler Extrasolar Planet Data
I've posted links to the data from the Kepler Extrasolar planet mission (now linked to in Wikipedia, I'm not worthy), data on over 1,200 extrasolar planets and their stars. My Excel graph was rather sucky, but Flowing Data has some stunning visualizations of the data, and a cool animation from Jer Thorp. Rush over there right away.
(tip of the spreadsheet to Cosmic Variance)
(tip of the spreadsheet to Cosmic Variance)
Labels: exoplanet, extrasolar planet, Kepler Space Telescope
Tuesday, February 08, 2011
The Kepler Bonanza, Making Sense of Over a 1200 Extrasolar Worlds
KOI-701.03, an as yet unconfirmed, Earth-like world probably in the habitable zone of its Sun. KOI-703.03 visualized in Celestia (click to embiggen).As well as the unusual Kepler-11 solar system, the Kepler spacecraft has so far reported 1235 planetary candidates around 997 stars. See the paper here for more detail (warning, huge PDF file over 100 pages long)
To put this in perspective, in four months of staring a a patch of sky in Cygnus the size of your outstretched hand, Kepler has come up with 3 times as many extra-solar planets (maybe), as we had discovered from 1995 to June 2010.
Trying to understand this firehose of information will be a bit of an effort. First off, all these transit candidates have to be independently confirmed. This will be a massive piece of work, especially and ground based telescopes can only monitor the region of space Kepler scanned for about 6 months of the year, and multiple transits will have to be observed.
Distribution of planetary systems picked up by Kepler, I've used slightly different cutoffs that the Kepler folks (eg, I've used a 0.8-1.25 Earth radii as the criteria for 'Earth-like" but Kepler goes down to smaller radii). Click to embiggen.Secondly, there is so much data. Trying to wrap our heads around the data will be bewildering, even for folks who are used to large data sets.
As a service to the amateur community, I've made Excel Spread sheets of tables 1 and 2 of Borucki et al, "Characteristics of planetary candidates observed by Kepler, II: Analysis
of the first four months of data", the Star Characteristics (table 1) and the Planet Candidates (Table 2) so you can play with the exoplanet data. Also, Kevin Schlaufman has made a plain text formatted electronic table that joins up Tables 1 and 2 (hat tip to Systemic) which is good for correlating planetary characteristics with stellar characteristics.
If you use this please a) remember to cite Borucki et al., (they did all the hard work after all) and b) remember that most candidates are unconfirmed, so don't get too excited. Most candidates will be real, but perhaps 5% are false positives, so be careful.
As an example of what can be done I've made a Celestia file of the unconfirmed Super-Earth KOI 701.03, which may be in the systems habitable zone (it is currently the most Earth-like world in a habitable zone). First download newextrasolar.stc here, (I've updated it with KOI 701 if you have downloaded a previous version) then copy it into the Celestia extras folder. Then you need the file the sets out the exoplanet Kepler701b.ssc, download it here and copy it into the extras folder.
Now, at -11 ºC the calculated black-body temperature of the planet is hotter than the black-body temperature of Venus (how hot Venus would be if it didn't have it's crushing carbon dioxide atmosphere, for comparison, without earth atmosphere our black body temperature would be -18 ºC) . How hot it is really depends on the nature of its atmosphere.
If I get enough time I'll make a script which will auto-magically extract data from the spreadsheets into Celestia format.
Other implications of the Kepler data are that if it's results are representative of the galaxy in general, then around 50% of Sun-like stars have planets, and they may be at least one million Earth-like planets in habitable zones in the Milky-Way alone.
While Kepler has only found planets around 0.6% of the stars it's looked at, it has been looking for only 4 months, and for example, it would be very unlikely to pick up a transit of a planet with an Earth-like orbital period or longer. As well, most stars will not be correctly oriented for Kepler to see a transit, which is why a 0.6% find rate implies that there are LOTS of planetary systems out there.
The Journal Nature has some free articles on the hunt for exoplanets here and here, the Bad Astronomers take is here, and Life at the SETI Institute here. Systemic has thoughtful posts here and here and a great video here, Centauri Dreams muses here.
Join the Planet Hunters and search the Kepler data for planetary candidates yourself!
Labels: exoplanet, extrasolar planet, Kepler Space Telescope
Thursday, February 03, 2011
Kepler -11, Kepler Bags A Very Strange Solar System
Left Panel: The Kepler-11 solar system, 6 confirmed planets orbiting around a sun-like star, all within what would be the orbit of Venus. Right Panel: Kepler-11c transit as seen from Kepler-11d, with 11B about to transit next. Kepler-11 system visualized in Celestia (click to embiggen).
The Kepler spacecraft has been really busy. Hot on the heels of the magma world Kepler-10b comes a very different solar system, Kepler-11. Kepler 11 is a multi-planet solar system, with 6 confirmed planets it ties with HD 10180 the biggest solar system known to date ( HD may have a 7th planet, but it is currently unconfirmed, Gliese 581 may have 6 planets, but two of the planets are currently unconfirmed).
However, this solar system is unlike that of ours. Kepler-11 is a Sun-like G class star, around the same size and luminosity as our Sun. However, its stable of detected planets all huddle well inside the equivalent of the orbit of Venus. They zip around their central star in a handful of days, and the two innermost are quite close to each other. Of the 6, 4 are Neptune-like and two, b and f, are most likely water worlds (boiling water in the case of b).
Multi-planet systems are rather rare, of the 521 planetary systems found by transit and radial velocity measurements, only 59 are multiple planetary systems. This is most likely an artifact of how we discover exoplanets; small planets are hard to find against a background of big planets, as are planets with long orbital periods. Also, with transiting planets the system has to be in the right orientation to have the outer planets observably transit.
Of course, you can visualize this system in Celestia. First you need to create a file in the extras folder that has the star Kepler-11 in it (see the Kepler-10b post), I've already created one, and you can download newextrasolar.stc here, then copy into the Celestia extras folder. Then you need the file the sets out the exoplanets (Kepler11abcdef.ssc, download it here and copy into the extras folder), and Robert is your avuncular relative.
So download the files and have a play. (I'll post about the 1200 planets Kepler has found, and the Earth-like ones, tomorrow).
Labels: celestia, exoplanet, extrasolar planet, transit
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