Study finds white dwarf stars may hold the key to detecting life on other planets

Apr 24, 2013
Study finds white dwarf stars may hold the key to detecting life on other planets

(Phys.org) —Because it has no source of energy, a dead star—known as a white dwarf—will eventually cool down and fade away. But circumstantial evidence suggests that white dwarfs can still support habitable planets, says Prof. Dan Maoz of Tel Aviv University's School of Physics and Astronomy.

Now Prof. Maoz and Prof. Avi Loeb, Director of Harvard University's Institute for Theory and Computation and a Sackler Professor by Special Appointment at TAU, have shown that, using advanced technology to become available within the next decade, it should be possible to detect biomarkers surrounding these planets—including oxygen and methane—that indicate the presence of life.

Published in the Monthly Notices of the Royal Astronomical Society, the researchers' "simulated spectrum" demonstrates that the (JWST), set to be launched by NASA in 2018, will be capable of detecting oxygen and water in the atmosphere of an Earth-like planet orbiting a white dwarf after only a few hours of observation time—much more easily than for an Earth-like planet orbiting a sun-like star.

Their collaboration is made possible by the Harvard TAU Astronomy Initiative, recently endowed by Dr. Raymond and Beverly Sackler.

Faint light, clear signals

"In the quest for extraterrestrial biological signatures, the first stars we study should be white dwarfs," said Prof. Loeb. Prof. Maoz agrees, noting that if "all the conditions are right, we'll be able to detect " on planets orbiting white dwarf stars using the much-anticipated JWST.

An abundance of heavy elements already observed on the surface of white dwarfs suggest orbit a significant fraction of them. The researchers estimate that a survey of 500 of the closest white dwarfs could spot one or more .

The unique characteristics of could make these planets easier to spot than planets orbiting normal stars, the researchers have shown. Their atmospheres can be detected and analyzed when a star dims as an orbiting planet crosses in front of it. As the background starlight shines through the planet's atmosphere, elements in the atmosphere will absorb some of the starlight, leaving chemical clues of their presence—clues that can then be detected from the JWST.

When an Earth-like planet orbits a normal star, "the difficulty lies in the extreme faintness of the signal, which is hidden in the glare of the 'parent' star," Prof. Maoz says. "The novelty of our idea is that, if the parent star is a white dwarf, whose size is comparable to that of an Earth-sized planet, that glare is greatly reduced, and we can now realistically contemplate seeing the oxygen biomarker."

In order to estimate the kind of data that the JWST will be able to see, the researchers created a "synthetic spectrum," which replicates that of an inhabited planet similar to Earth orbiting a white dwarf. They demonstrated that the telescope should be able to pick up signs of oxygen and water, if they exist on the planet.

A critical sign of life

The presence of oxygen biomarkers would be the most critical signal of the presence of life on extraterrestrial planets. Earth's atmosphere, for example, is 21 percent oxygen, and this is entirely produced by our planet's plant life as a result of photosynthesis. Without the existence of plants, an atmosphere would be entirely devoid of oxygen.

The JWST will be ideal for hunting out signs of life on extraterrestrial planets because it is designed to look into the infrared region of the light spectrum, where such biomarkers are prominent. In addition, as a space-based telescope, it will be able to analyze the atmospheres of Earth-like outside our solar system without weeding out the similar signatures of Earth's own atmosphere.

Explore further: Image: Galactic wheel of life shines in infrared

Related Stories

Can life emerge on planets around cooling stars?

Nov 20, 2012

(Phys.org)—Astronomers find planets in strange places and wonder if they might support life. One such place would be in orbit around a white or brown dwarf. While neither is a star like the sun, both glow and so could be ...

Habitable planets and white dwarfs

Mar 22, 2011

(PhysOrg.com) -- The search for habitable planets similar to Earth has routinely focused around active nuclear burning stars. However, in a recently published paper by Eric Agol from the University of Washington, ...

Super cold brown dwarf or is it a planet?

Mar 23, 2011

(PhysOrg.com) -- In a month that has already announced the discovery of a brown dwarf 75 light-years from Earth, NASA’s infrared Spitzer Space Telescope has found what could prove to be an even cooler, ...

Recommended for you

Image: Galactic wheel of life shines in infrared

Oct 24, 2014

It might look like a spoked wheel or even a "Chakram" weapon wielded by warriors like "Xena," from the fictional TV show, but this ringed galaxy is actually a vast place of stellar life. A newly released ...

New window on the early Universe

Oct 22, 2014

Scientists at the Universities of Bonn and Cardiff see good times approaching for astrophysicists after hatching a new observational strategy to distill detailed information from galaxies at the edge of ...

User comments : 34

Adjust slider to filter visible comments by rank

Display comments: newest first

vidyunmaya
1 / 5 (11) Apr 24, 2013
Necessity-sequential flow analysis in the interest of Space-Science to Cosmology studies while the drives and origins are ignored..
Kaymen
1.6 / 5 (7) Apr 25, 2013
Wouldn't it be a good idea to send something out to see if we can detect life on this planet?
beleg
1 / 5 (5) Apr 25, 2013
The paradigm shift is finding an isolated stellar celestial body having no object under the body's influence or in accompaniment of that body whatsoever.
Q-Star
2.7 / 5 (14) Apr 25, 2013
Wouldn't it be a good idea to send something out to see if we can detect life on this planet?


It's a great idea,,,, when might ya be sending it out? I mean, considering how busy NASA is with other good ideas, maybe ya could step up and do this thing,,,, as a gift to the curious public.
GSwift7
2.3 / 5 (16) Apr 26, 2013
Of course the problem is observing time. They suggest a few hours of observation per target, and a survey of around 500 targets? And of course, they will need to be pointed at each one at exactly the time of transit. The guys running the time schedule on JWST probably just spit coffee all over their desks when they read that. They'll surely do some close inspections of exoplanets with JWST, but that would need to be previously confirmed exoplanets. Time on JWST will be the most expensive telescope time in history, especially while it still has coolant. (that's assuming we actually get it working)

Is it just me, or do those first three comments seem an aweful lot like it might be one person? All three have kinda messed up language and don't make much sense. That second commenter doesn't seem to have read the article at all, and the first one must be on drugs.
Requiem
1 / 5 (7) Apr 28, 2013
It's frustrating that nobody really has any feasible ideas on how they would even go about building an instrument to get good pictures of exoplanets, and once they do, it'll likely take another monumental multi-decade space telescope project. I'd like to at least see some 320x200 visible light photos of alien worlds before I die.

Somebody should design a constellation of Jupiter Lagrangian Interferometer telescopes. That would be sweet at any wavelength they got it working at.
Fleetfoot
5 / 5 (3) Apr 28, 2013
It's frustrating that nobody really has any feasible ideas on how they would even go about building an instrument to get good pictures of exoplanets,


Webster Cash has been promoting the "New Worlds Imager" based on a particular flower-shaped mask for many years and the project is still being proposed:

http://newworlds.colorado.edu/

and once they do, it'll likely take another monumental multi-decade space telescope project.


No question, and an astronomical heap of money.
Requiem
1 / 5 (7) Apr 28, 2013
Thanks for that. Interesting reading.

On one of the pages on that site, it states:
The final step in extrasolar planet studies will be the ability to study these distant worlds in the same way that Earth-observing systems study the Earth's surface. Such a telescope will of necessity be large, to collect enough light to resolve and analyze small details on the planet's surface. However, these kinds of studies do not lie in the foreseeable future, for it takes square kilometers of collecting area to capture the needed signal.


Is it not possible, in theory, to have say 5 Hubble-scale space telescopes, complete with occulters, positioned at various Jupiter or Saturn Lagrangian points and perform interferometry, even in visible wavelengths, on exoplanets that vaguely coincide with the vertical planes of our solar system? Does a solar-system-scale angular resolution enhancement not make up for the lack of collection area, even within only say 20-100 light-years?
GSwift7
2.2 / 5 (13) Apr 29, 2013
Somebody should design a constellation of Jupiter Lagrangian Interferometer telescopes


There's a pair of satellites preparing to launch right now with the purpose of attempting to fly in the type of precise formation required to build a space interferometer. Once we know whether this is possible, or rather, what the error tollerence needs to be, we might begin to design such a system.

As far as where to place it, I don't think Jupiter would be the first choice. You would probably want to pick the simplest gravity situation we can find. That probably means orbiting the sun well inside the Jupiter orbit. Maybe orbit sol along the orbit of Mars, but opposite of Mars? Something like that, but probably not a Lagrange point. Gravity is funky around L points, and I think it would make formation flying difficult, if not impossible. L points have saddle shaped gravity wells, so the formation would wobble around.
Fleetfoot
5 / 5 (3) Apr 29, 2013
Such a telescope will of necessity be large, to collect enough light to resolve and analyze small details on the planet's surface. However, these kinds of studies do not lie in the foreseeable future, for it takes square kilometers of collecting area to capture the needed signal.


Is it not possible, in theory, to have say 5 Hubble-scale space telescopes, complete with occulters, positioned at various Jupiter or Saturn Lagrangian points and perform interferometry, even in visible wavelengths, on exoplanets ....


It would give you the resolution (although there are limitations) but it would only collect the number of photons intercepted by the total surface area. The problem would be the signal to noise ratio. You could improve that using very long exposures but the target planet will rotate so you would have to reconstruct the image.
Requiem
1 / 5 (7) Apr 30, 2013
There's a pair of satellites preparing to launch right now with the purpose of attempting to fly in the type of precise formation required to build a space interferometer. Once we know whether this is possible, or rather, what the error tollerence needs to be, we might begin to design such a system.

As far as where to place it, I don't think Jupiter would be the first choice. You would probably want to pick the simplest gravity situation we can find. That probably means orbiting the sun well inside the Jupiter orbit. Maybe orbit sol along the orbit of Mars, but opposite of Mars? Something like that, but probably not a Lagrange point. Gravity is funky around L points, and I think it would make formation flying difficult, if not impossible. L points have saddle shaped gravity wells, so the formation would wobble around.


Do you remember the name of the project?

Also, I was talking about placing 1 telescope at each Lagrangian point, including the one on the far side of Sol.
Requiem
1 / 5 (7) Apr 30, 2013
It would give you the resolution (although there are limitations) but it would only collect the number of photons intercepted by the total surface area. The problem would be the signal to noise ratio. You could improve that using very long exposures but the target planet will rotate so you would have to reconstruct the image.


My understanding is that you only get the collection capacity of a single collector, not all of them combined. I wish I knew how to do the math to see exactly how far one Hubble could swiftly resolve an Earth-sized disc to 320x200 if it had the angular resolution of Saturn's orbit.
Requiem
1 / 5 (7) Apr 30, 2013
Well I guess since it's a disc it would be 300x300 lol.

But you know what I mean. CGA style resolution at least.
Fleetfoot
5 / 5 (2) Apr 30, 2013
I wish I knew how to do the math to see exactly how far one Hubble could swiftly resolve an Earth-sized disc to 320x200 if it had the angular resolution of Saturn's orbit.


I'm not sure what you mean, you need a fleet of them to do interferometry. There was an article recently (on this site I think) about the problems of resolving ambiguities depending on the number and separation of elements of interferometers like the SKA, it's not a trivial topic.
GSwift7
1.7 / 5 (12) May 01, 2013
Do you remember the name of the project?


Proba3

http://phys.org/n...ion.html

An interferometer gives you the angular resolution of a lense as wide as your individual telescopes are spread apart. So two telescopes 1000 miles apart would have the angular resolution of a 1000 mile wide telescope. HOWEVER, there's a catch. Of course they don't collect as many photons as a 1000 mile wide telescope would, so the image has high resolution but it is still a very faint image. You tend to use interferometry on distant but bright objects.

The maximum distance between the elements of your interferometer is limited by your ability to measure and control the distance between them in real time. We do not yet know if this is possible in space with current technology, much less what the limit on spacing between elements will be. I'm not aware of any place in the solar system where gravity is uniform enough to allow the scale you talk about
Modernmystic
1.4 / 5 (9) May 01, 2013
Earth-like planet orbiting a white dwarf.


Oxymoron. You're not going to find an "Earth like" planet orbiting a white dwarf.

They were burnt to a crisp in the red giant phase.

Any planet currently orbiting a white dwarf that WASN'T fried in the red giant phase is so cold now the oxygen is probably sitting on its surface as ice (depending on distance) or was blown off (if it was too close during the giant phase but wasn't obliterated).

Not a good use of money IMO....
Requiem
1 / 5 (7) May 01, 2013
I'm not sure what you mean, you need a fleet of them to do interferometry. There was an article recently (on this site I think) about the problems of resolving ambiguities depending on the number and separation of elements of interferometers like the SKA, it's not a trivial topic.


Sorry, I didn't really relate what I meant well in that post. In interferometery, you only get the collection "power" of one single collector. So 10 100m2 collectors = 100m2 of collection power, not 1000m2, but the angular resolution is enhanced as some function of the maximum distance between any 2 given collectors.

So therefore the reference to a single Hubble with an angular resolution corresponding to an aperture the size of Saturn's orbit is apt when considering a constellation of Hubble-scale spacecraft performing interferometry in Saturn Langrangian wells.

Continued...
Requiem
1 / 5 (7) May 01, 2013
Regarding how complicated it is, it can't be as complicated as you make it out to be, because Russia's Spektr-R program, which has a highly variable earth-moon surrounding orbiter and ground telescopes(although it's radio), happily reported that they were making great progress and had already identified interference fringes in something like 3 weeks after launch. They anticipate 7 micro-arcsecond resolution out to some specific range.

Again, this involves a limited number of ground sites(I believe just 1 actually), spinning around on the face of the Earth, while a satellite circumorbits Earth and the Moon. If this is possible with such a dymanic combination of collectors, surely it's easier to launch some number of Hubbles(It's worth noting that Cassini is about that size, it has been in operation in Saturn for about a decade now, and didn't launch from a Space Shuttle) than it is to build one massive collector that can just look straight at it.
Noumenon
1.4 / 5 (27) May 01, 2013
Study finds white dwarf stars may hold the key to detecting life on other planets


I always thought Danny DiVito was a little peculiar.
Requiem
1 / 5 (7) May 01, 2013
Proba3

http://phys.org/n...ion.html


That article makes no mention of interferometery, it talks about formation flying a lens and a detector very far apart for very long focal lengths. This would indeed require very precise relative positioning.
Q-Star
2.9 / 5 (15) May 01, 2013
Proba3

http://phys.org/n...ion.html


That article makes no mention of interferometry, it talks about formation flying a lens and a detector very far apart for very long focal lengths. This would indeed require very precise relative positioning.


Ya are absolutely correct,,,, that mission is to test the feasibility of creating a space telescope with a very long focal length by using separate satellites for the lens and the detector. That mission has nothing to do with interferometry.

We can already do space interferometry any time the politicians loosen up the purse strings. It doesn't require the precise alignment that this mission is testing. Computers can make adjustments to the image during processing that is not dependent on exact positioning. All that is necessary is KNOWING the exact position.
Requiem
1 / 5 (7) May 01, 2013
We can already do space interferometry any time the politicians loosen up the purse strings...


The real question is, I think, how far a purpose-built Hubble(or just the existing one for academic sake) constellation spanning Saturn's orbit could overcome it's lack of collection surface area to the point that it would be able to resolve Earth at 300x300. Assuming an occulter or some other novel technology to overcome the star's glare.

I'm pretty sure there is a straightforward way to get an absolute value measured in light years. I just have no idea where to start.
Requiem
1 / 5 (7) May 01, 2013
Or maybe there's showstoppers, like some collector to synthetic aperture area ratio, or spacial coverage requirement that scales with the area of the synthetic aperture, meaning that we'd need 50, or 500 Hubbles orbiting at all of the inner planetary Lagrangian points to satisfy the requirements of having a Saturn-orbit-sized synthetic aperture, or that we'd need 100m lenses or something else prohibitive.

As a baseline I'd say that it's not very useful(for this purpose) if it can't at least image an Earth at 300x300 at 20 light years.

I've never met anybody who can say, and I've never read anything that indicates that such barriers are present.
GSwift7
1.9 / 5 (14) May 02, 2013
Actually, a long baseline visible light space interferometer would require the same level of formation precision as the long focal length telescope. The requirement is the same either way. You can compensate with computer enhancement, but there's a limit to that.

See the section at the bottom of the following link regarding Labeyrie's hypertelescope:

http://en.wikiped...erometer

Labeyrie's hypertelescope is what Requiem is talking about. As the article says, formation precision would need to be within a fraction of a wavelength.

ESA's proposed Darwin telescope was similar:

http://en.wikiped..._Mission

Here's a quote from the Darwin page:

The study of this proposed mission ended in 2007 with no further activities planned. To produce an image, the telescopes would have had to operate in formation with distances between the telescopes controlled to within a few micrometres


That includes computer image processing.
Q-Star
2.5 / 5 (13) May 02, 2013
Actually, a long baseline visible light space interferometer would require the same level of formation precision as the long focal length telescope. The requirement is the same either way. You can compensate with computer enhancement, but there's a limit to that..


Interferometry does not depend on precise alignment. It depends on KNOWING precise position. All ya are doing is combining and relating two (or more) SEPARATE images. It gives greater resolution without the necessity of greater collection. Meaning, ya can't necessarily see further, ya can just resolve smaller things. Again position doesn't matter as much KNOWING the position precisely.

The long focal length DOES depend on precise alignment. It must be precise because the single image must be FOCUSED on the detector. Basically ya increase your magnification by increasing your focal length. PRECISE position IS necessary to precisely focus the image.
GSwift7
1.3 / 5 (12) May 02, 2013
Again position doesn't matter as much KNOWING the position precisely.


again, that's not actually correct.

If you need another source, try this one:

http://en.wikiped...ynthesis

The computer synthesized aperature you're talking about doesn't work with visible light. See the section in my link titled "techincal issues".

Visible light is not the same as radio waves when it comes to interferometry.
Q-Star
2.7 / 5 (14) May 02, 2013
Again position doesn't matter as much KNOWING the position precisely.


again, that's not actually correct.


Actually that is very correct.

If you need another source, try this one:

http://en.wikiped...ynthesis

The computer synthesized aperature you're talking about doesn't work with visible light. See the section in my link titled "techincal issues".

Visible light is not the same as radio waves when it comes to interferometry.


Ya should try reading your own links, ya might have noticed this from the wiki page ya're using.

Accurate optical delay and atmospheric wavefront aberration correction is required, a very demanding technology which became possible only in the 1990s. This is why imaging with aperture synthesis has been used successfully in radio astronomy since the 1950s and in optical/infrared astronomy only since the 2000 decade.


Which is moot, because those aberrations wouldn't present themselves in space.
GSwift7
1.9 / 5 (14) May 03, 2013
Wow, you're really dense when you choose to be.

The page on synthetic aperature seems to be WAY over your head. I can see that you are holding onto several misconceptions here. I'm not going to fight with you over this one.

Here's the official ESA Darwin mission page:

http://www.esa.in...overview

Here's a quote in black and white:

as the light collected by the telescopes was supposed to be recombined at very high precision. A deviation of more than just 100 thousandths of a millimetre could have ruined the observation


In addition to advanced optical and computer tricks:

The spacecraft was probably to be equipped with tiny ion engines that need just five kilograms of fuel to last the entire five-year mission.


We still do not have any way to get around the requirement of precision in the distance between elements of an optical interferometer. It must remain steady while observing.
Q-Star
2.7 / 5 (14) May 03, 2013
Wow, you're really dense when you choose to be.


Thanks.

The page on synthetic aperature seems to be WAY over your head. I can see that you are holding onto several misconceptions here. I'm not going to fight with you over this one.

Here's the official ESA Darwin mission page:

http://www.esa.in...overview

as the light collected by the telescopes was supposed to be recombined at very high precision. A deviation of more than just 100 thousandths of a millimetre could have ruined the observation


In addition to advanced optical and computer tricks:

We still do not have any way to get around the requirement of precision in the distance between elements of an optical interferometer. It must remain steady while observing.


Ya should try to stay more current. The stuff on that page varies from 20 to 5 years old. That's the problem with ya internet experts, the devil is the details.
Q-Star
2.7 / 5 (14) May 03, 2013
@GSwift,

I'm sure ya are an earnest sort,,,, But ya to seem to pick up misconceptions by reading the simplest presentations and run with them. On reflecting on your comments, I think I understand where the disagreement lay.

The Darwin system was proposed for several collectors, each sending their images back to a remote detector,,, the same precision problem that the system using two satellites as separate lens & detector. Yes that must be precise.

But a spaced based interferometer, even in optical or infrared, need not fly in a precise formation (relatively speaking) to function at peak performance. AS LONG as the lens & detector are on the SAME platform, several such platforms can provide the input for optical interferometry, in that situation the only requirement is KNOWING the precise SEPARATION when the separate imaged are acquired.

MaiioBihzon
2 / 5 (16) May 14, 2013
This is excellent SETI. Find the planets, find the biomarkers, find the life. One step at a time. Maybe they'll find some industrial pollutants mixed in with the water and oxygen. If they do, we'll have a pretty good idea where to focus future searches.

Now if we, as new to astrophysics as we are, stand on the brink of finding other biospheres, it's safe to say more advanced civilizations in our corner of the Galaxy have already catalogued all the living worlds within reach of their instruments. So the more advanced civilizations out there? They have already found us.
beleg
1 / 5 (3) Jun 01, 2013
"the only requirement is KNOWING the precise SEPARATION when the separate imaged are acquired." - Q
Does a static separation exist in space for two unique objects? Look at LIGO or any earth based interferometry system - reconstructions schemes for images accounting for thermal noise in the individual components the system is made of. You can do this. On earth.
I see G7 point. Your point overlooks his point.
Q-Star
2.5 / 5 (13) Jun 01, 2013
Does a static separation exist in space for two unique objects? .


At each instant in time yes. As long as ya know the precise time AND precise location of each detector, combining them is relatively easy. LIGO is a different animal altogether. The difficultly being in the thing ya are detecting.

Ya realize to detect these hoped for gravity waves, ya are dealing with changes on the order of a couple of proton diameters over kilometers? Right?

Gravity waves are an entirely different animal than electromagnetic radiation. The word interferometer is the only thing the two examples have in common.
Q-Star
2.3 / 5 (12) Jun 01, 2013
P.S.

Does a static separation exist in space for two unique objects? Look at LIGO or any earth based interferometry system - reconstructions schemes for images accounting for thermal noise in the individual components the system is made of. You can do this. On earth.


Interferometry telescopes on earth move relative to each other all the time. The movement is accounted for during the image processing.