Nearly 500 exoplanets — planets orbiting other stars — have been detected since the first was discovered in the mid-90s. A variety of methods have been used to find them: Doppler shift of starlight as the circling planets tug their stars, the dip in light as a planet passes directly in front of its star, even the change in light of a distant star as the gravity of a planet briefly magnifies it a la Einstein.
But getting direct pictures of planets is really hard. A typical star is roughly a billion times brighter than a planet! And from our great distance, the planet and star are so close together that the former is lost in the latter’s glare.
But a new breakthrough has just been announced by astronomers at the University of Arizona — known for their ability to push the frontiers of what’s possible observationally. What they’ve done is complex, but basically, it reduces the glare from a star, allowing the fainter planet to be more easily detected.
The image here shows just such a detection! The planet orbiting the star Beta Pictoris has been known for some time, so it was a good choice to test the new optical design. They knew what they were looking for, and they found it! In the image, the location of Beta Pic is indicated. The ripples around it are diffraction patterns, a bit like ripples in a pond when you drop a rock in it (though more closely related to the ripples you see when water flows around an obstacle in its path like a rock or sandbar).
Any time you observe a star, what you get is a bright core, and a pattern of ripples like that; it’s built into the physics of light being a wave. What the new technique does is steal a bit of light from the core and use it to suppress some of those ripples. It interferes with them, damping them down. It only works on half the image, as you can see: on the right the ripples are obvious, and on the left they are essentially gone. If you’re looking for a planet, it means you have to observe it several times rotating the detector so you can clean up the halo all the way around the star.
I’m very, very impressed with this advance. Detecting planets directly in images is extremely hard; I’ve tried to do it myself with Hubble and it was a monumental pain in the derriere. That’s why we only have a handful of planets directly seen! The planet Beta Pic b is only about 6 times the distance from its star as Earth is from the Sun, so this new technique really allows astronomers to get in close.
I expect that over the next few years we’ll be seeing this technique used to see lots of previously detected planets and confirm their existence, as well as new planets around other stars. Way back when I worked on Hubble, I tried to determine if we could use our camera to spot a Jupiter-sized planet orbiting Alpha Centauri if it had the same separation from its star as Jupiter does from the Sun (about 800 million kilometers). We were really close, but in reality it would’ve been a nearly impossible task.
I suspect this new technique may make it a whole lot easier. So stay tuned. We may be getting a lot more pictures of faint new worlds very soon!
Image credit: ESO. Tip o’ the apodizing phase plate to Fark
Related posts:
- Theoretically, Alpha Centauri should have planets
- Another direct picture of a planet
- Another exoplanet imaged?
- First exoplanet imaged
October 17th, 2010 at 7:34 am
Phil — can you help me with a sense of scale here? Is Beta Pictoris the entire black circle there, or just the smaller circle in the center? If it’s just the smaller circle, that implies that the planet is comparatively HUGE. Although actually even if it’s the larger circle, it looks like the planet is MUCH larger, compared to its star, than, say, Jupiter is compared to our sun.
October 17th, 2010 at 7:40 am
Finding what you know is there is very easy, finding something you didn’t even imagine being there is much more impressive.
By the way, Phil, would you have comments about one of the recent exoplanet discoveries (I think it was the “possibly habitable” one) that “disappeared” when other group(s) tried to locate it? I wonder how many of these exoplanets have been verified by more than one team, preferably using different means of observation, and how many are just promising guesstimates of what could be a planet when you look at the data the right way.
October 17th, 2010 at 7:57 am
#1 Jim: We’re not seeing the actual discs here: just the light accumulating on the sensor. Beta Pic is 1.8 solar radii, and a solar radius is just about 0.005 AU (while you can see the scale of 6 AU on the picture).
October 17th, 2010 at 8:03 am
OK, trying to get a perspective on this. Beta Pictoris is a young, main-sequence star a bit bigger that the sun but quite a bit brighter. Beta Pictoris b is 6 AU from its star, and Jupiter is 5 AU from the sun. Beta Pictoris b is also quite a bit bigger than Jupiter, though. So, could a hypothetical alien astronomer living near Beta Pictoris use this same technique to image Jupiter? Oh, and is it possible to do spectroscopic analysis on the light from the planet?
October 17th, 2010 at 8:21 am
Superluminously (beyond just brilliant) wonderful and exciting news! I can’t wait!
Have they tried using it for the already imaged Fomalhaut b and HR 8799 (“Gadolabove” as I’ve dubbed it!) exoplanetary systems too as another way to confirm & perhaps add to those new found worlds?
October 17th, 2010 at 8:35 am
@4. TreeLobsters Says:
Yes, indeed – Beta Pictoris is quite a lot brighter and more massive being an A5 V or even A3 V Sirian type star versus our G2 V yellow dwarf Sun. For more see :
http://stars.astro.illinois.edu/sow/betapic.html
Which notes that Beta Pictoris has 8.6 times the Sun’s luminosity putting out much more energy in a day than our Sun would radiate in a whole week and having nearly double our Sun’s mass. (Well 1.7 solar mass which is a lot more anyhow.)
Adding just a little extra mass leads to a very big increase in the brightness stellar~wise.
I’ll also second TreeLobsters question on the possibility of doing spectroscopic analysis on the exoplanet’s light here too.
@ 2. Mike :
See :
http://blogs.discovermagazine.com/80beats/2010/10/12/um-that-goldilocks-exoplanet-may-not-exist/
Sadly it seems that the “Goldilocks planet” Gliese 581g may not exist after all – nor might Gl 581f either.
October 17th, 2010 at 8:53 am
BTW. If folks haven’t seen it before then see :
http://blogs.discovermagazine.com/badastronomy/2010/10/13/riding-the-sky/#comment-318986
for an explanation of why I like to dub HR 8799 as “Gadolabove” &, yes, I’m hoping the name grows on y’all and gets adopted! (Hey, I can dream can’t I?
)
Also see :
http://stars.astro.illinois.edu/sow/hr8799.html
for more on that star & its exoplanetary system; incl. a neat finderchart photo that guides you to a lot else of interest too, incl. 51 Pegasi and Messier 15, via Kaler’s superb ‘Stars’ website.
October 17th, 2010 at 8:55 am
TreeLobsters: Beta Pictoris is much younger than the Sun, and the planet is much more massive than Jupiter. The upshot of that is that the planet is much hotter (~1500 K) and more luminous than Jupiter is, which makes it significantly brighter. Detecting even an isolated Jupiter, i.e. one that is not orbiting a star, at that distance would be challenging: IIRC the coolest known brown dwarfs are at ~500K which is substantially warmer than the real Jupiter, and those objects (UGPS 0722-05, DENIS 0817-6155) are located much closer to us than Beta Pictoris is.
October 17th, 2010 at 8:59 am
The first of the ‘related links’ terminates with a pair of double quotes: “”
so the page comes up with ‘Error 404 – Not Found’. It’s easy enough to remove the double quotes in the browser address bar, but I thought I’d let you know…
http://blogs.discovermagazine.com/badastronomy/2008/03/07/theoretically-alpha-centauri-should-have-planets/
October 17th, 2010 at 9:36 am
Prepárate para ver pronto muchas más imágenes de exoplanetas…
Obtener imágenes directas de planetas es muy difícil. Una estrella típica es un billón de veces más brillante que un planeta.A gran distancia,el planeta y la estrella están tan juntos que el primero se pierde en el resplandor de esta última. Pero ha si…
October 17th, 2010 at 9:38 am
I’ve done a bit of investigation into this: all the relevant data is online, and the Systemic console application is freely-available for fitting RV models. That means anyone interested has the opportunity to play around with the data to see what’s there. Turns out that the HIRES data published by Vogt et al. (2010) can only find planets b and c. The HARPS data from Mayor et al. (2009) easily spots planets b, c, d and e, but has no hint of planets f and g. Only the combination of the two finds f and g, and that immediately makes me suspicious that it is an artifact of the data merge.
Next question is, would we expect to see planets f and g in the 2009 HARPS data if they are present? I’ve done a bit of playing around with generating some synthetic datasets to try to figure it out, and it looks from my admittedly relatively small number of trials that somewhere around 90% of the time the HARPS data should easily show evidence of at least one of planets f and g.
Sure it isn’t conclusive at the moment, and it would be nice if the potentially-habitable planet were there, but right now I’m very sceptical about the existence of either of the two new planets.
October 17th, 2010 at 10:09 am
[...] Πηγη: Bad Astronomy Blog [...]
October 17th, 2010 at 10:41 am
Hey guys I have a couple of Layman’s questions.
Ive seen plenty of planets being detected by the ‘transit method’, but that relies on the planet/s passing directly between the star and us. What are the odds of that ?
It just seems very unlikely to me. Are planetary systems rotating on random planes throughout the galaxy ? or do they tend to follow the galactic plane ?
Also I saw that post about Alpha Centari possibly having planets, but what is the closest exoplanet that we have found so far ?
This is such an exciting subject that I have a ton more questions but I wont bombard you guys just now
Stubby
October 17th, 2010 at 10:50 am
This technique should work for more than just exoplanets, too. What kind of insights should we expect this to give us on contact binaries, accretion disks, brown dwarfs, and such?
October 17th, 2010 at 10:52 am
Sciencists think that about 0.5% of stars will have at least one planet aligned to star in such way that we can spot transit.
October 17th, 2010 at 11:03 am
Stubby: the Solar System is inclined at roughly 60 degrees to the galactic plane. I don’t think there’s any evidence that binary stars show any preference for alignment with the galactic plane, so there’s no reason to suspect that exoplanetary systems should be aligned either.
October 17th, 2010 at 11:20 am
!!!
October 17th, 2010 at 12:25 pm
Soon we will we will know, are we alone.
October 17th, 2010 at 1:00 pm
Imagine… ehr, image that!
@ MTU:
Whether Fomalhaut b is a planet may be up for grabs too:
“More reports from the IAU meeting at Torino, this time on surprises with the putative planet around Fomalhaut. [...] Well, Ray Jay reports on a talk by Kalas: there is new HST data, which apparently shows the plant [sic] still, but in a slightly wrong place – suggesting maybe an eccentric orbit which crosses the dust ring, which is problematic. Further, the speculation, now, on the excess brightness is that it is a co-orbiting dust cloud, which is starting to be a bit of a stretch [sic]”
[HT "Dynamics of Cats"]
I can’t make head or tails of that report, btw, so please clarify if anyone can. I take it that with all these problems, it is uncertain what the object is, but I may be interpreting it wrong. But even if it’s not a planet, it is still a nice image! And the new technique may help clarify matters.
@ andy:
That doesn’t twig with the rumor mill. I got it from an astrophysicist which I can’t place vs the team loop but knows his stuff, that the HARP team sees the signals. But even with a larger data set can’t get sufficient significance for detection. Dunno what their analysis is, but it doesn’t seem to be the Systemic console if so.
OTOH they can’t reject the planet(s) either (this from a press release). So I understand it as an joint argument about the exclusion of false positives, not a lack of them.
October 17th, 2010 at 1:18 pm
@Torbjörn Larsson, OM:
Hmmm going back to the data, it looks like if I search way down in the noise level there are peaks fairly close to the reported periods of f and g, but that may be coincidence (the reported false alarm probabilities are greater than one!!!). The trial systems I ran using simulated 6-planet systems tended to show up planets f and/or g much more strongly than this, but maybe HARPS managed to get unlucky. Of course, this is only the published HARPS data, not the new stuff which isn’t available yet.
October 17th, 2010 at 2:39 pm
This has an eerie quality for me, science fiction come to life. I have been reading SF for over 50 years. It has always been taken for granted that exo-planets were out there, but actually seeing them is something else again: Several centuries of speculation and logical inference confirmed by observation.
It is not for nothing that the Science Fiction Encyclopedia includes a lengthy article entitled “Science Fiction Overtaken by Events.”
October 17th, 2010 at 4:18 pm
Kinda the sad part – it was actually expected we’d be locating planets by actually going to the star and looking around.
October 17th, 2010 at 4:48 pm
That is aweseome- I love it when a big advance comes from clever,inventive, thinking, rather than mega bucks brute force. Although i do love that to…..
October 17th, 2010 at 5:02 pm
[...] via Discover] Categories: Science Tags: astronomy, asu, exoplanets, light, planets, space, stars, telescopes [...]
October 17th, 2010 at 5:13 pm
I want to see the calculations which led to whatever pattern was scribed. The “glass” shown looks like ZnSe. I’m not such a fan of using diamond to scribe the surface though – what a painful operation. I’d bet lithography and etching would do better, or even good ol’ electron beam etching. I’d like to see a SEM image as well.
October 17th, 2010 at 5:35 pm
So, lets ask this: What technology would it take life on any of the known exoplanets to spot us? How ‘visible’ is our planet from any of these places we have found. Are we invisible to the rest of the galaxy inessence because of resolution limits of known technology?
A quirky paradox it would be if life could only exist on a planet below a set of technological parameters, therefor making every life-bearing planet invisible. A neat sci-fi conundrum….galaxy doused with life, but they all think they are alone because of some finicky limitation of some basic technology.
October 17th, 2010 at 6:27 pm
[...] Astronomers expect to use this technique to confirm the 500 exoplanets discovered so far are the real deal (sometimes they’re false positives), and then they’ll use it to find even more. [Eurekalert via Discover] [...]
October 17th, 2010 at 6:53 pm
Awesome. Totally freaking awesome. This wasn’t from Hubble? Adaptive optics rock my world.
HJ
October 17th, 2010 at 7:24 pm
Well, we’re not going to get a LOT more images of extra-solar planets soon, at least not until (if) the New Worlds Explorer is launched. Beta Pic B seems to be at about 0.1 arc-second from Beta Pic and few if any of the known exo-planets fall in that range (and they pretty much all have fainter primaries also). Also, by definition, because of their higher inclinations, the already known exo-planetary systems are quite poor candidates for this technique. A FEW new planets will likely be found using this advance though, which is a good thing (and more once the next generation of ground based telescopes are built) . Also, I don’t understand how “we were really close” and “but in reality it would’ve been a nearly impossible task” can both me true. If you are really close to doing something then clearly it can’t also be “nearly impossible”!
October 17th, 2010 at 7:25 pm
@Jamey
Think of the timeline, think of the timeline!!!!
October 17th, 2010 at 9:29 pm
[...] Astronomers expect to use this technique to confirm the 500 exoplanets discovered so far are the real deal (sometimes they’re false positives), and then they’ll use it to find even more. [Eurekalert via Discover] [...]
October 17th, 2010 at 11:55 pm
@ 19. Torbjörn Larsson, OM : Thanks for that update on Fomalhaut b.
Its good that the science is finding out more and making corrections, but sad to discover that what we thought were real exoplanets may not be there or may not be what we thought they were.
@13. Stubby Says:
Epsilon Eridani which has a Jovian planet in an eccentric orbit ranging from 5 to 1 AU forming about it. Epsilon Eridani is only ten and a half light years distant – it is the tenth nearest star to our own and is a K2 orange dwarf star visible to the unaided eye.
There were early suggestion in the mid 90′s that an even closer star – Lalande 21185 a red dwarf & the 4th nearest star – might have an exoplanet orbiting it but this seems to have been rejected or at best remains unconfirmed. Much older past claims of planets around Proxima Centauri, Van Biesbroek 8 and Barnard’s Star among others have also been disproven having turned out to be instrument error.
@30. Monkey Says:
Of course, its very hard to predict what the timeline will be and what discoveries – technological breakhroughs esp. – may lie ahead .. You never know!
But, well, yeah.
October 18th, 2010 at 1:05 am
For more info. on Epsilon Eridani & its exoplanet – see :
http://stars.astro.illinois.edu/sow/epseri.html
via Kaler’s Stars website which notes :
There’s also a good little photographic finderchart for Epsilon Eri. and other nearby stars there too.
More info. on the false alarm over Van Biesbroeck’s Star (8) is linked here :
http://en.wikipedia.org/wiki/Van_Biesbroeck_8b
& click here :
http://en.wikipedia.org/wiki/Lalande_21185#Claims_of_a_planetary_system
for the false alarm (probably we now think!) claims of exoplanets for Lalande 21185.
October 18th, 2010 at 1:35 am
NB. Like Wilhelm Gliese & Max Wolf, George Van Biesbroeck compiled a star catalogue which lead to many stars having the Van Biesbroeck or VB prefix. The star involved here is Van Biesbroeck 8 and NOT VB 10 with the latter (VB-10) being the star most commonly known as Van Biesbroeck’s Star. VB 10 is another faint red dwarf with an unusually high proper motion. (Apparent movement across the sky.) See :
http://en.wikipedia.org/wiki/VB_10
&
http://en.wikipedia.org/wiki/Van_Biesbroeck%27s_star_catalog
&
http://en.wikipedia.org/wiki/Van_Biesbroeck_8
for more. Sorry if that causes any confusion.
PS. Epsilon Eridani is a very young star and its planetary system is still forming – there’s a good article on it by Ken Croswell in Astronomy magazine, December 1995 starting page 46.
October 18th, 2010 at 1:48 am
It’s a shame that the ‘Star Shield’ : http://physicsworld.com/cws/article/news/25276 didn’t take off (ah ha. ah ha.) as I would have liked to have seen the resulting images. This is pretty incredible and I am glad it was managed from a ground-based telescope. It makes the endeavour much more feasible.
October 18th, 2010 at 2:37 am
@Torbjörn Larsson
That doesn’t twig with the rumor mill. I got it from an astrophysicist which I can’t place vs the team loop but knows his stuff, that the HARP team sees the signals.
I just wanted to comment on this issue of Gl 581. I was at the Torino meeting. Your source sounds like they’re getting their wires crossed a little. To quote from a couple of other posts from Andy:
Only the combination of the two finds f and g, and that immediately makes me suspicious that it is an artifact of the data merge.
and
Of course, this is only the published HARPS data, not the new stuff which isn’t available yet.
This is indeed what happened. The original team took some data with HARPS, combined it with the data set that found the original planets, and got some signals that implied the presence of an additional two planets. Since then the team from Geneva have continued to take RV measurements of GL 851 using HARPS, getting about 50% more data than previously accumulated. That data shows no sign of planets f and g. They also replicated the signal found by Vogts that led to the announcement of GL851f &g, but found that the only way that it appeared was with a process that made it a false signal.
Before anyone asks I can’t remember/don’t know the details of their analysis method. If I can find my notes from the meeting or get some better info, I’ll of course let you all know.
Finally, @Mike (#2): The vast majority of the exoplanets that we know of are solid discoveries. Certainly for transiting planets (my area), confirmation of planetary status is not usually given out until several transits have been observed and RV measurements have been made. The problems begin when you start trying to go to smaller planets, with weaker signals. Then you have to take extreme care that you’re not looking at a false positive. Unfortunately if we ever want to find anything remotely earthlike, that’s what we’re going to have to do.
October 18th, 2010 at 6:43 am
[...] Get ready to see lots more exoplanet images soon – Nearly 500 exoplanets — planets orbiting other stars — have been detected since the first was discovered in the mid-90s. A variety of methods have been used to find them: Doppler shift of starlight as the circling planets tug their stars, the dip in light as a planet passes directly in front of its star, even the change in light of a distant star as the gravity of a planet briefly magnifies it a la Einstein. -Phil Plait / Bad Astronomy [...]
October 18th, 2010 at 8:19 am
[...] Planet hunters no longer blinded by the light Get ready to see lots more exoplanet images soon [...]
October 18th, 2010 at 10:19 am
One aspect of the potential usefulness of this technique mentioned in the PR (but, alas, not here) is in the studies of objects like young stars and distant quasars. The study of Young Stellar Objects( jets, disks) and Active Galactic Nuclei (jets from SMBHs, host galaxies of Quasars & Blazars) could benefit greatly from this technique. As great as the potential is for future exo-planetary science, this technique could prove valuable in a number of sub-fields of astronomy. It will be interesting to see how it is employed over the next few years.
October 18th, 2010 at 10:29 am
I can see my house from here!
October 18th, 2010 at 10:45 am
@Messier Tidy Upper:
Regarding the comments about Epsilon Eridani b, the orbit for that planet is highly uncertain. The problem seems to be that Eps Eri is a highly active star, which probably messes things up quite a bit.
The real problem is that the published orbits (particularly the extremely eccentric radial velocity+astrometry solution) are inconsistent with the presence of an inner asteroid belt around the star at a distance of 3 AU which was detected by Spitzer. In order for the planet and the asteroid belt to exist, the planet’s orbit has to be highly circular. See Brogi et al. (2009) “Dynamical stability of the inner belt around epsilon Eridani.”
If so, this makes Epsilon Eridani look like a very good analogue for the young solar system: a Jupiter-like planet (scaling for the lower luminosity of Epsilon Eridani relative to the Sun, it is at pretty much the same place in its solar system as Jupiter is in ours) orbiting outside an asteroid belt, with a cold debris disk located at a large distance in the outer system. Then again, I’ve seen rumours that it is possible to model the Spitzer data that implied the asteroid belt’s existence using only dust produced in the Epsilon Eridani outer disk, which would nullify this constraint on the planet’s eccentricity.
All in all, a confirmed image of Epsilon Eridani b would definitely be a very useful thing: it would certainly resolve a lot of uncertainty about its orbit!
October 18th, 2010 at 11:34 am
Mike @ 2:
That is one of the usual laments of lay-men, and it unfortunately shows some lack of understanding of how science works. First of all you always have to check and document your methods before you can rightfully claim new discoveries. That is, science always progresses by small steps that are tightly connected to previous (and published) work. When your method has been proven, you can go out and make new discoveries. And developing this method really deserves a lot of credit – it is an incredible feat they have pulled off – succesfully as shown by their proof-of-concept picture.
In this case, however, I don’t think it is ideal for discovering new planetary system – that is not what this method is about – it is about separating the light from the planet from the overwhelming light of the star. With that accomplished we can image the planets (as shown here), and much more importantly (since we still can’t resolve the planets) we can take spectra and learn about the temperature, composition and chemistry of the planet. This is where we are going to make discoveries – and maybe find signs of life! Of course, the method will most likely also find new planets in already known planetary systems.
Cheers, Regner
October 18th, 2010 at 11:41 am
@lordbubonicus: Thanks for the info. Nice to see my amateur analysis arrived at some of the same conclusions as the professionals did.
One of the neat things about the history of exoplanet discovery is that it has come at a time when the computing power and astronomical equipment available to amateurs is such that it is possible for them to make useful contributions to the research, most notably where transits are concerned.
October 18th, 2010 at 11:51 am
[...] på ett sätt som får en fin förklaring på engelska här hos astrobiologen Caleb Scharf. Phil Plait gör ett eget försök och ett annat finns i pressmeddelandet hos University of Arizona. Tekniken används faktiskt sedan [...]
October 18th, 2010 at 4:28 pm
@Monkey#26: That’s only half the problem. For aliens to even observe us they must have (1) evolved with some means of manipulating the environment, (2) developed an intelligence which allows them to examine and understand how nature works, and (3) exploited knowledge as humans had, and discover and invent many devices (or functional equivalents) which we humans had invented.