This morning I want to circle around to a story I had planned to write about a couple of weeks ago. One thing writing Centauri Dreams has taught me is that there is never a shortage of material, and I occasionally find myself trying to catch up with stories long planned. In this case, the imaging of an exoplanet around the star Beta Pictoris demands our attention because of the methods used, which involve charge-coupled devices and wavelengths close to visible light. The detection marks real progress in visible light imaging of exoplanets.
The work, which is slated to appear in The Astrophysical Journal, was conducted by researchers from the University of Arizona led by Laird Close. Charge-coupled devices (CCD) are the same kind of technology we find in digital camera imaging sensors, used here in a setting where we’d normally expect an infrared detector. But using infrared means viewing massive young planets hot enough to put out considerable heat. As the exoplanet hunt develops and we push the search for life in the cosmos, we’re after much trickier game, says Close:
“[W]e now are a small step closer to being able to image planets outside our solar system in visible light. Our ultimate goal is to be able to image what we call pale blue dots. After all, the Earth is blue. And that’s where you want to look for other planets: in reflected blue light.”
Image: An image of the exoplanet Beta Pictoris b taken with the Magellan Adaptive Optics VisAO camera. This image was made using a CCD camera, which is essentially the same technology as a digital camera. The planet is nearly 100,000 times fainter than its star, and orbits its star at roughly the same distance as Saturn from our Sun. (Image: Jared Males/UA).
Beyond young, hot planets, we’d like to image planets that have long since cooled, the kind of worlds where the passage of time has allowed for the development of life. Beta Pictoris b certainly does not fit that bill, but the technology points in the right direction. Now deployed at the Magellan 6.5-meter instrument in Chile, the system Close and team have developed — Magellan Adaptive Optics — can manipulate a deformable mirror so that its shape changes a thousand times a second in real time, overcoming atmospheric distortion. The team used the MagAO system in tandem with VisAO, a visible wavelength camera. The detection points toward future space-based observatories that can ‘drill down’ to the detection of cooler terrestrial worlds.
“[W]e were able to record the planet’s own glow because it is still young and hot enough so that its signal stood out against the noise introduced by atmospheric blurring,” added lead author Jared Males. “But when you go yet another 100,000 times fainter to spot much cooler and truly earthlike planets, we reach a situation in which the residual blurring from the atmosphere is too large and we may have to resort to a specialized space telescope instead.”
The imaged planet orbits at 9 AU from the host star, a bit closer than Saturn in our own Solar System, and appears 100,000 times fainter than the star. Males describes the image as having the highest contrast ever achieved on an exoplanet this close to its star. That the image was actually that of Beta Pictoris b, an object about twelve times the mass of Jupiter with an atmospheric temperature in the range of 1700 Kelvin, was confirmed using a second MagAO image taken in the infrared spectrum, where the giant world shines much more brightly.
So we’re a long way from directly imaging Earth-like planets around other stars, but tuning up our methods in visible light will eventually pay off with future space-based planet finders. The paper is Males et al., “Magellan Adaptive Optics ?rst-light observations of the exoplanet ? Pic b. I. Direct imaging in the far-red optical with MagAO+VisAO and in the near-IR with NICI,” accepted at The Astrophysical Journal (preprint). A University of Arizona news release is also available.
Give or take two or three radii away from the planet and the temperature on the facing side of any orbiting moon will be about the liquid water range through thermal emission alone. Tidal heating could increase the distance away from the planet that could allow liquid water considerably.
Are you aware of any attempts to measure the reflex motion of Beta Pictoris due to the planet? Having a dynamical mass for this object would be quite useful in constraining formation models.
I’m the first author of the subject paper. Great blog post, and thanks for highlighting our work!
Andy – yes indeed, there are radial velocity measurements of this system. So far only upper limits have been reported because a full orbit hasn’t been monitored, but since the planet is orbiting nearly edge on we will have very good constraints within about 10 years or so. Using our position measurement, the RV measurements constrain the planet to be 12 Jupiters in mass, give or take a Jupiter (this is an UPPER limit). This is pretty close to the mass we derive from our measurement of the planet’s brightness. Here’s a reference: http://adsabs.harvard.edu/abs/2012A%26A…542A..18L
Another point to consider is that there is small, though noticeably non-zero, chance that the planet will transit in a few years. So we might even get a radius measurement too. This would be a huge step in understanding planet formation and evolution. Keep your fingers crossed.
I see that this system is almost edge on, if we get a really good look at the planet is there the possibility of detecting moons around it by transit?
Based on the above image made in wavelengths close to visible light, can we conclude Beta Pictoris b would appear as a bright white planet to our eyes?
The existence of Beta Pictoris b and Fomalhaut b (if it exists) suggests that massive stars, perhaps even B class stars, may host families of planets. A B class star would support a wide zone of continuous habitability, perhaps containing more than one terrestrial planet, although it would exist briefly due to the star’s rapid evolution.
Regarding transits of Beta Pictoris b, according to the Wikipedia article on Beta Pictoris , “A ‘transit-like event’ was observed in November 1981”. The cited reference is here:
http://www.aanda.org/articles/aa/abs/2009/14/aa11528-08/aa11528-08.html
Robert Feyerharm said on March 26, 2014 at 14:05:
Regarding transits of Beta Pictoris b, according to the Wikipedia article on Beta Pictoris , “A ‘transit-like event’ was observed in November 1981?. The cited reference is here:
http://www.aanda.org/articles/aa/abs/2009/14/aa11528-08/aa11528-08.html
I assume and hope that the astronomical records have been and are being checked for other stellar transits of a suspicious nature from before 1990?
And this just in – we should also pay more attention to Class F stars for exoplanets and the chances of habitability upon them:
http://www.spacedaily.com/reports/Could_Alien_Life_Cope_with_a_Hotter_Brighter_Star_999.html
http://www.uta.edu/news/releases/2014/03/FStars-paper.php
https://www.technology.org/2014/03/25/alien-life-cope-hotter-brighter-star/
http://arxiv.org/pdf/1312.7431.pdf
These days does it pay to ignore just about any celestial object when it comes to the possibility of life? The fact that we are learning just how much we have to learn about the Cosmos is a hopeful sign that we are finally heading in the right directions.
@ljk: with regard to habitable planets around F stars: I did not find much new in the referred articles.
Apart from the mentioned aggressive UV overdose, the main problem would be rapid evolution and hence the moving outward of the HZ, thereby rendering the Continuous HZ (CHZ) rather narrow after all.
Interesting are fig. 7 and table 4 in the published paper, where the ‘continuous domains of the CHZs’ (I think this is rather double) are shown between the two blue lines in the 4 graphs. This amount of space is actually rather narrow, not more, possibly less, than for a later spectral type (G, K) star.
Robert, that image is false color. The colors just show relative brightness, and don’t correspond to what your eye would see at all.
Further to my previous comment: on the basis of the decreasing lifespan, and rapidly outward moving and narrowing CHZ toward increasingly brighter (earlier spectral type) stars, I suspect that before about F9, very optimistically F7 or 8, main sequence lifespan of stars becomes too short to offer a sufficient window of opportunity for any higher life.
@Jared Males: thanks for the reply… I actually had in mind the astrometric reflex orbit, but it is certainly interesting that radial velocities can get into the planetary mass domain for this type of star.
Transit is an interesting possibility, especially for the possibility of dust clouds associated with an irregular satellite swarm.
Do we have sufficient resolution to detect a wobble due to an Earth-size moon, or indeed a super Earth sized one?
@Ronald – Stars follow trends very well. If the HZ expands for every other spectral class of stars, I’d say the same pretty much applies for ‘F’ class stars too. They should be able to offer more area than stars like our own. Don’t get stuck on graphs too much. I recently stumbled upon a webpage discussing habitability (something like Habitable Zone for dummies), it was from all intents and purposes a professional website but it showed G class and K class stars as having the same size of the HZ.
As for lifespan of F dwarfs – well, maybe life there wouldn’t take as much time to emerge, and as much time to develop intelligence, like it did here on Earth. This shouldn’t apply just to F class stars, but pretty much anything below .. say …. A8V/A9V.
Consider it would be bathed in UV, probably more prone to mutate than life in this environment, pressures and challenges not encountered here. If it emerges, I’d say it has a chance of getting somewhere more long-term as a home.
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As far as Beta Pictoris is concerned, I’m very much looking forward to that transit event