Exoplanet Targets in Nearby Space

by Paul Gilster on June 18, 2013

I’m a coffee fanatic. Not only do I drink a lot of the stuff, but I roast my own beans and love fiddling with roasting times and fan speeds, trying to hit exactly the right note. And with a just-brewed carafe of Burundi by my side this morning, it’s natural enough that I would be drawn to an exoplanet tool called ESPRESSO. Echelle SPectrograph or Rocky Exoplanet and Stable Spectroscopic Observations is the next generation spectrograph for the European Southern Observatory’s Very Large Telescope, which has already played such a huge role in finding distant worlds.

Using the HARPS spectrograph, the VLT already holds the record for most exoplanet discoveries from equipment on the ground. Upgraded with ESPRESSO, the VLT should be primed for even more fine-tuned radial velocity measurements. HARPS was designed to get us down to about the 1 m/s level, although its effective precision is considerably tighter. But we’re still not in range of Earth-like planets in the habitable zone. The Earth creates a radial velocity variation of 9 cm/s on the Sun, about three times smaller than HARPS can work with. ESPRESSO makes up the difference, taking us down to a few cm/s if all goes well, making detection of habitable planets in Earth-like orbits feasible from the ground.

Installation at the VLT is currently scheduled for 2016. As we ponder near-term developments like this, it’s intriguing how much is happening to push our knowledge of smaller exoplanets forward right here on Earth. The Next-Generation Transit Survey (NGTS), like ESPRESSO, follows a highly successful predecessor, in this case the Super-WASP project that went after exoplanets on the cheap. That’s ‘cheap’ as in camera lenses bought on eBay that have found 65 exoplanets.

Although Super-WASP (Wide Angle Search for Planets) demonstrated how successful searches could be managed from the ground, the Kepler ‘long stare’ into the Lyra/Cygnus star field examined planets whose transits are in many cases at the limit (or beyond it) of ground-based follow-up observations. NGTS goes after ‘hot Neptunes’ and ‘super-Earths’ from its site at Cerro Paranal at the European Southern Observatory in Chile, looking for transits around bright, nearby stars. These are transits that would allow follow-up observations by radial velocity methods, revealing not only the radius but also the mass and density of these worlds.

ngts_small

Image: Artist’s impression of the completed NGTS, a robotic facility to be sited at ESO-Paranal. Credit: Next-Generation Transit Survey.

Quoted in this feature in Astrobiology Magazine, Warwick University’s Peter Wheatley, co-principal investigator for NGTS, says the idea is to gather “… the first statistical sample of measured densities for small planets.” He adds: “We believe this sample will allow quantitative tests of planet formation, migration and evolutionary models, and will drive the development of future models.” But with space-based equipment like Hubble and the James Webb Space Telescope in the mix, we can also look toward identifying useful targets, smaller planets bright enough for their atmospheres to be studied through ‘transmission spectroscopy,’ where starlight that is absorbed as it passes through the atmosphere is analyzed to flag its components.

From the NGTS site:

The observation of the planet during its transit at many different wavelengths allows us to obtain its transmission spectrum (stellar light passing through the planet atmosphere). The transmission spectrum is measured by identifying the small differences in transit depth as a function of wavelength. This technique usually requires extremely high signal to noise data and has been successfully applied only on a few planets orbiting bright stars, like for example HD189733. However it is a powerful technique measuring the distinct signature of chemical components in the atmosphere of a planet. This technique can be used to search for water on some planets, and even eventually for biomarkers on rocky planets. It has been successfully carried out on GJ1214b, a Neptune type planet, using FORS [FOcal Reducer and low dispersion Spectrograph] observations. However, the discovery of additional bright targets is essential for this technique to be more widely applied to planets in the Neptune size range.

And here’s the GJ1214b work, showing how the transit light curve can be used to tease out atmospheric information:

transmission_spectrum

Image: Transmission spectrum of GJ1214b measured by FORS (Bean et al. 2010). Credit: Next-Generation Transit Survey.

The Next-Generation Transit Survey is to be a robotic installation using an array of small telescopes operating in the 600-900 nm band, maximizing their sensitivity to K and early M-class host stars. Finding the brightest exoplanets in the ‘hot Neptune’ and ‘super-Earth’ categories will give us fodder for study by the VLT as well as Hubble and JWST, with all key technologies already demonstrated through a successful prototype. Also aided by NGST data will be the European Space Agency’s CHEOPS (CHaracterising ExOPlanets Satellite), slated for 2017 launch, which will target already identified planets to improve their transit measurements.

Ground- and space-based instruments are intertwined as we push exoplanet studies toward smaller and smaller planets. We already confirm many transits through radial velocity methods with tools like HARPS, but to take the study of exoplanet atmospheres to the next level will require even larger observatories like the planned European Extremely Large Telescope, or the proposed Colossus. In an era of big equipment, it’s heartening to think that relatively inexpensive tools like the NGTS can play so vital a role in finding the targets for these behemoths.

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{ 21 comments }

Paul W June 18, 2013 at 12:39

I am very cognizant that telescopes which operate in space have a better resolving capability than those placed conveniently here on earth.
However, so long as we lack the capability to service the ultra expensive scopes in space, I feel that maximum push should go to efforts on the ground.
The wonderful Herschel Space Telescope has run out of cryogenic liquids that cool it sufficiently to see faint objects. Frustrating that it worked just fine, it just lacks coolant! On the other hand, the beautiful LBT atop Mt. Graham in Az is “down” because an accident occurred with the light adaptive secondary mirror. Well, it will be back. Little nerdy techs are swarming over it and will not rest until it is repaired.
Many of the large light adaptive ground telescopes are claiming that their optics now exceed the resolution of the Hubble. Experts, how true is this?
When people eventually have space-going mobility, just imagine a Herschel type scope sitting in that naturally cryogenic crater at the south lunar pole. No coolant required, ever!
And radio scopes are sure for more than SETI.

ljk June 18, 2013 at 14:49

Paul W June 18, 2013 at 12:39

“And radio scopes are sure for more than SETI.”

Why did you make that comment? Most of the radio telescopes on Earth and any that I know of in space are used for regular astronomical work. SETI usually happens on old telescopes that are no longer of interest to the professional astronomers or they piggyback on them, getting whatever scraps fall from the cosmic table and hoping for something viable.

The ATA is the only group of radio dishes devoted to SETI and that is running into financial and data analyzing troubles.

And there are optical telescopes being used for Optical SETI (lasers, infrared), but again that is not the majority of such instruments.

I hope one day we do have a radio telescope in space and on the lunar farside for the express purpose of conducting SETI. If we ever get past this economic crisis and grow up as a society.

Daniel June 18, 2013 at 15:58

Paul W – ” Little nerdy techs…” ? Condescending?

That scope at the south lunar pole will need a self sufficient nearby colony to maintain it, among other things. We should have been there already and I hope I live to see it.

Paul W June 18, 2013 at 17:44

Paul W – ” Little nerdy techs…” ? Condescending?

Hardly…I put them above me, though that is not saying much. I do love flying over their baby on Mt. Graham and I have visited the site personally. I am a big fan of LBT and the people who work there.

Tarmen June 18, 2013 at 20:26

Clearly we need a permanent manned telescope base on Luna staffed with nerdy techs, not necessarily little. Like Antarctica. Let us take the necessary steps.

David Cummings June 19, 2013 at 6:56

Daniel: “That scope at the south lunar pole will need a self sufficient nearby colony to maintain it…”

As much as I would love to see humans back on the moon — a Lunar Hotel would be great! — I don’t think we should shackle the concept of a telescope on the moon to the necessity of a return by humans.

The entire project — transport, construction, maintenance — can be done by robots. Maybe not by the robots of today, but certainly by the robots of the very near future (10 years? 5 years?).

Putting a telescope on the moon should be on a priority level above and beyond the wish list of getting humans back on the moon. It can be done so much more cheaply without people.

Long-term presence of humans on the moon is not in the cards right now. Just the subject of radiation alone — forgetting all the other problems sustaining human life presents — is enough to make a human lunar colony a very long-term project. Much more long term than building that telescope.

ljk June 19, 2013 at 9:09

Tarmen said on June 18, 2013 at 20:26:

“Clearly we need a permanent manned telescope base on Luna staffed with nerdy techs, not necessarily little. Like Antarctica. Let us take the necessary steps.”

Do not count on NASA making that happen any time soon…

http://www.geekosystem.com/nasa-says-no-new-lunar-missions/

The Republicans want a Moon and Mars base, but with what money?

http://nasawatch.com/archives/2013/06/wheres-the-mone.html

But apparently there is also no funding for the Asteroid Rendezvous Mission:

http://nasawatch.com/archives/2013/06/draft-only-high.html

Private industry may be our only hope of a permanent foothold in space. China and Russia may be ready in twenty or so years, with India eventually showing up. If they cancel the planetoid retrieval plan and with no lunar missions and nothing definite for Mars in the next three or four decades, I am not quite sure what NASA plans to become in the future. Do not tell me that Orion won’t get cancelled; Obama got rid of Constellation in 2009.

Dmitri June 19, 2013 at 13:37

Radiation on Moon is counted in and it’s planned to be tackled either by building settlements deep into the ground or build walls of artificial igloos and fortify with the Lunar soil to shield against the radiation. Of course the discussion is also into building settlements into a Lunar crater.

Don’t know much about ambitious plans of China, probably there is a significant one as they have bough all the former Soviet space technology and developing for their need. I think Moon is quite possibly high on their agenda as it allows to make its mark in history and world around.

Russians will have a family of reusable new generation manned Lunar landing vehicle by 2018 and they have plans for manned mission around 2024.

Rob Flores June 19, 2013 at 14:36

One thing that the Kepler spacecraft could not give us (even with 5-6 year
lifetime) is the prevalence of gas giants in F,G,K, stars, at 4AU and up.
Planetary scientists have already been surprised about the statistical distribution of planets in terms of size and orbits inside of 2AU.
What would it mean if the average star only had Icy Neptune and smaller
bodies beyonnd the equivalent of our asteroid belt. Obcourse that does
not rule out cool brown dwarfs much further out, which would be very hard
hunt down.

Incidentaly:
The more we learn about Mars the less I like it as a colony site, it’s advantages over the Moon as great as we might like to think.

Mars atmosphere is so tenous meteorites regularly strike its surface at
high kinetic energy. If you were impacted 1mm sized iron piece you
can bet it woudn’t just leave a bruise.
The power yield from solar power is half that of Earth.
The soil of Mars is fairly reactant and fine.
There is a significant temperature gradient. (materials degradation)

Its three great advatages are ,plentyfull raw materials , more gravity.
Atmosphere. (on balance it’s only useful in aerobraking)

A location on the moon chosen at the right place could support
10-20 thousand colonists. While mars could easily support millions
it’s distance will make it cost prohibitive to colonize there in the near future.

ljk June 19, 2013 at 16:12

Dmitri said on June 19, 2013 at 13:37:

“Russians will have a family of reusable new generation manned Lunar landing vehicle by 2018 and they have plans for manned mission around 2024.”

With all due respect, Dmitri, will they have learned by then from the problems with Phobos-Grunt?

http://www.russianspaceweb.com/phobos_grunt.html

I predict that should the Chinese or Russians set up a manned base on the Moon that they will create a large illuminated representation of their national flags or some other recognizable symbol of their culture across the lunar surface that will be visible from Earth without optical aid.

Perhaps that will spur NASA or American businesses to do something about the situation. It always seems to be that we need a kick in the pants to get moving and then we go gangbusters, at least for a while.

ljk June 19, 2013 at 16:31

Another problem with settling Mars that I do not see addressed very often is the problem with landing vehicles on that planet’s surface.

The fine Martian dust combined with the exhaust flare of landing rockets will make a very potent sandblasting effect. A manned landing vehicle will need a powerful thruster to touch down all that tonnage safely.

That might not be a problem for the first few manned missions to the Red Planet, but what happens when a base is set up? The landing zone will have to be placed fairly far away in order not to sandblast the base, its external equipment, and any unfortunate astronauts who happen to be outdoors at the time.

It is not an unsolvable problem, to be sure, but it might be an issue during the critical times in establishing a permanent base. If a base failed, I can see whoever funded it being quite reluctant to dole out more money – especially if it is a corporation where the bottom line is all.

And the Moon (can we please call it Luna since there are hundreds of moons in our Sol system) has its own big problems with gritty surface dust. Just ask the Apollo astronauts who were only there for three Earth days at the most.

Some details here:

http://www.4frontierscorp.com/dev/assets/Anita%20and%20Dick%20-%20Requirements%20for%20Space%20Settlements%20on%20the%20Moon%20and%20Mars.pdf

Dmitri June 19, 2013 at 16:59

LRO fresh observational data shows that plastic will do fine shielding for the radiation on Moon.

http://phys.org/news/2013-06-moon-health-astronauts.html

Dmitri June 19, 2013 at 17:08

ljk, yes they have. They agreed that first they test a new platform in ghe flight and later gradually deploy on other mission. But this is just for unmanned missions. Phobos-Grunt was doomed due to high complexity of mission and lots of new solutions. Anyway on Phobos-Grunt the engines for reaching the orbit failed and this failed the whole mission. Maybe there wasn’t more glitches.

Now regaeding manned missions this is completely another fairytale. They built for that purpose a new fully digital spacecraft with Lunar and Mars landing capability. Russians told that Moon is an ideal test ground for Mars landing rehearsals.

I’ve posted links on this before but later will dig them up and repost h

David Cummings June 19, 2013 at 19:56

Interesting discussion but anyway a telescope on the moon is not dependent on any off-earth colony at all… and certainly a lot cheaper. What’s the price-tag of a lunar telescope compared to a lunar or Martian colony? Many orders of magnitude cheaper.

And in the meantime, a telescope on the moon will be a big assist at planet-finding.

Eniac June 19, 2013 at 22:28

As we have discussed before, there is little reason to put a telescope on the moon. There are far better locations elsewhere, in a large variety of free-floating locations, devoid of gravity, dust, scattered light, temperature changes, and other nuisances. They are also easier to get to, for the most part.

Whether we need techs (nerdy, little, or otherwise), is an interesting question. One which has pretty much already been answered given the existing missions and plans: The answer is NO. I am pretty sure that the corrective lens for Hubble was the swan song of human telescope repair missions. An expensive one, no doubt, if you add it all up.

Tarmen June 20, 2013 at 9:41

We are fortunate that we have a halfway decent rocky planet like Mars in the next orbit. It could have been another gas planet. And also lucky that we have Luna as a stepping stone just 3 days away from our Earth orbital facilities. So, good fortune has provided the path for us. Rus, Chin, Euros, Americans can all choose to take the road or stay home and watch.

ljk June 20, 2013 at 11:22

Tarmen said on June 20, 2013 at 9:41:

“We are fortunate that we have a halfway decent rocky planet like Mars in the next orbit. It could have been another gas planet. And also lucky that we have Luna as a stepping stone just 3 days away from our Earth orbital facilities. So, good fortune has provided the path for us. Rus, Chin, Euros, Americans can all choose to take the road or stay home and watch.”

Even if Jupiter existed where Mars is now – and assuming its massive presence did not disrupt our region of the Sol system so that Earth either did not exist or was pushed into an orbit unfavorable for life (that is why the Main Planetoid Belt is where it is due to Jupiter keeping anything larger than Ceres from forming) – the gas giant has a number of large moons, with Callisto being outside Jovian radiation belts.

Yes we did have Luna shining up the sky as a goal, but note our personal ventures to it came about due to geopolitical purposes and no human has set foot there since 1972. Apollo was an exciting abberation. It is now far enough in the past that if we ever do start sending humans beyond Earth orbit, this will not be because of that program.

Oh, Apollo will get its recognition and tributes as the ones who got there first, but the technology to reach and settle other worlds will not have come from that program except in the largely abstract sense (the computer system aboard Apollo was scary primitive by today’s standards and will be just this side of an abacus in the near future).

The people who do land on Luna and Mars and beyond one day will not know any of the first astronauts except from their history lessons and will be going there for reasons other than following in their footsteps. Though expect the propoganda machine to be in full force that they are going to the stars on the shoulders of these guys to expand human knowledge. The real reasons will be for much more basic human needs: Profit, religion and political freedom, vacations, and such.

Laura June 20, 2013 at 18:09

Burundi, mmmmmm. It just turned up after a long absence at my local coffee emporium.

coolstar June 21, 2013 at 19:24

Small technical correction: HARPS is installed on ESO’s 3.6m telescope at La Silla Observatory and not on one of the VLT telescopes. HARPS North is going on the TNG on La Palma in the Canaries. ESPRESSO should be a great instrument, just don’t hold your breath waiting for something as good on an American backed telescope.

ljk September 3, 2013 at 23:29

Blue Light Observations Indicate Water-Rich Atmosphere of a Super-Earth

September 3, 2013

A Japanese research team of astronomers and planetary scientists has used Subaru Telescope’s two optical cameras, Suprime-Cam and the Faint Object Camera and Spectrograph (FOCAS), with a blue transmission filter to observe planetary transits of super-Earth GJ 1214 b (Gilese 1214 b) (Figure 1).

The team investigated whether this planet has an atmosphere rich in water or hydrogen. The Subaru observations show that the sky of this planet does not show a strong Rayleigh scattering feature, which a cloudless hydrogen-dominated atmosphere would predict.

When combined with the findings of previous observations in other colors, this new observational result implies that GJ 1214 b is likely to have a water-rich atmosphere.

Full article here:

http://www.naoj.org/Pressrelease/2013/09/03/index.html

ljk December 17, 2013 at 12:04

Review: From Dust to Life

The formation of the solar system from a cloud of dust and gas turns out to be far more complicated than what even recent models suggested. Jeff Foust reviews a book that provides a detailed overview of the formation of the planets, moons, and other bodies that comprise the solar system.

Monday, December 16, 2013

http://www.thespacereview.com/article/2419/1

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