Sunday, November 29, 2015

Cloudy with a chance of life: how to find alien life on distant exoplanets

This article was originally published in The Conversation on on 26th November 2015.

Cloudy with a chance of life: 

by Brad Carter, Amanda Bauer, & Jonti Horner

How do you go about hunting for life on another planet elsewhere in our galaxy? A useful starting point is to imagine looking from afar for signs of life on Earth. In a telescope like those we have on Earth, those aliens would likely just see the Earth and sun merged together into a single pale yellow dot.

If they were able to separate the Earth from the sun, they’d still only see a pale blue dot. There would be no way for them to image our planet’s surface and see life roving upon it.

However, those aliens could use spectroscopy, taking Earth’s light and breaking it into its component colours, to figure out what gases make up our atmosphere. Among these gases, they might hope to find a “biomarker”, something unusual and unexpected that could only be explained by the presence of life.

On Earth, the most obvious clue to the presence of life is the abundance of free oxygen in our atmosphere. Why oxygen? Because it is highly reactive and readily combines with other molecules on Earth’s surface and in our oceans. Without the constant resupply coming from life, the free oxygen in the atmosphere would largely disappear.


But the story isn’t quite that simple. Life has existed on Earth for at least 3.5 billion years. For much of that time, however, oxygen levels were far lower than those seen today.

And oxygen alone is not enough to indicate life; there are many abiological processes that can contribute oxygen to a planet’s atmosphere.

The concentration of oxygen in the Earth’s atmosphere over the last billion years. As a reference, the dashed red line shows the present concentration of 21%.  Wikimedia

For example, ultraviolet light could produce abundant oxygen in the atmosphere of a world covered with water, even if it was devoid of life.

The upshot of this is that a single gas does not a biomarker make. Instead, we must instead look for evidence of a chemical imbalance in a planet’s atmosphere, something that can not be explained by anything other than the presence of life.

Here on Earth, we have one: our atmosphere is not just rich in oxygen, but also contains significant traces of methane. While abundant oxygen or methane could easily be explained on a planet without life, we also know that methane and oxygen react with each other strongly and rapidly.

When you put them together, that reaction will cleanse the atmosphere of whichever is least common. So to maintain the amount of methane in our oxygen-rich atmosphere, you need a huge source of methane, replenishing it against oxygen’s depleting influence. The most likely explanation is life.

Observing exoplanetary atmospheres

If we find an exoplanet sufficiently similar to our own, there are several ways in which we could study its atmosphere to search for biomarkers.

When a planet passes directly between us and its host star, a small fraction of the star’s light will pass through the planet’s atmosphere on its way to Earth. If we could zoom in far enough, we would actually see the planet’s atmosphere as a translucent ring surrounding the dark spot that marks the body of the planet.

How much starlight passes through that ring gives us an indication of the atmosphere’s density and composition. What we get is a “transmission spectrum”, which is an absorption spectrum of the planetary atmosphere, illuminated by the background light of the star.

Our technology has only now become capable of collecting and analysing these spectra for the first time. As a result, our interpretation remains strongly limited by our telescopic capabilities and our burgeoning understanding of planetary atmospheres.

Despite the current challenges, the technique continues to develop with great success. In the past few years, astronomers have discovered a wide variety of different chemical species in the atmospheres of some of the biggest and baddest of the known transiting exoplanets.

Many exoplanets may have no atmosphere at all. NASA/JPL-Caltech


Another approach involves observing a transiting planet and its star as they orbit one another. The goal here is to collect some observations when the planet is visible (but not in transit), and others when it is eclipsed by its star.

With some effort, astronomers can subtract one observation from the other, effectively cancelling the hugely dominant contribution of light from the star. Once that light is removed, what we have left is the day-side spectrum of the planet.

[Star + Planet] - [Star] = [Planet] NASA/JPL-Caltech/R. Hurt (SSC/Caltech)

The future

Astronomers are constantly developing new techniques to glean information about exoplanetary atmospheres. One that shows particular potential, especially for the search for planets like our own, is the use of polarised light.

Most of the light we receive from planets is reflected, originating with the host star. The process of reflection brings with it a subtle benefit - the reflected light gains a degree of polarisation. Different surfaces yield different levels of polarisation, and that polarisation might just hold the key to finding the first oceans beyond the solar system.

By rotating a polarising filter, we can block light of certain polarisation. This is how polarised sunglasses cut the glare from puddles and the ocean on a sunny day.  Wikimedia, CC BY-SA

These methods are still severely constrained by two factors: the relative faintness of the exoplanets, and their proximity to their host star. The ongoing story of exoplanetary science is therefore heavily focused on overcoming these observational challenges.

Further down the line, advances in technology and the next generation of telescopes may allow the light from an Earth-like planet to be seen directly. At that point, the task becomes (slightly) easier, in part because the planet can be observed for far longer, rather than just relying on eclipse/transit observations.

But even then, spectroscopy will be the way to go; the planets will still be just pale blue dots.

What we have seen so far

The exoplanets we have discovered to date are highly inhospitable to life as we know it. None of the planets studied so far would even be habitable to the most extreme of extremophiles.

The planets whose atmospheres we have studied are primarily “hot Jupiters”, giant planets orbiting perilously close to their host stars. As they skim their host’s surface, they whizz around with periods of just a few days, yielding transits and eclipses with every orbit.

Because of the vast amounts of energy they receive from their hosts, many of these “hot Jupiters” are enormous, inflated far beyond the scale of our solar system’s largest planet. That size, that heat and their speed, make them the easiest targets for our observations.

But as our technology has improved, it has also become possible to observe, through painstaking effort, some smaller planets, known as “super-Earths”.

Atmospheres of distant planets…

The hot Jupiter HD189733 has one of the best understood planetary atmospheres beyond the solar system.

Artists impression of the broiling blue marble, HD 189733 b. NASA, ESA, M. Kornmesser

Observations by the Hubble Space Telescope, in 2013, suggest a deep-blue world, with a thick atmosphere of silicate vapour. Other studies have shown its atmosphere to contain significant amounts of water vapour, and carbon dioxide.

Overall, however, it appears to be a hydrogen-rich gas giant like Jupiter, albeit super-heated, with cloud tops exceeding 1,000 degrees. Beneath the cloud turps lies a widespread dust layer, featuring silicate and metallic salt compounds.

The young giant planets in the HR8799 system appear to have hydrogen-rich but complex atmospheres, with compounds such as methane, carbon monoxide and water. They are likely larger, younger, and hotter versions of our own giant planets - with their own unique subtleties.

A direct image of the four planets known to orbit the star HR 8799. Ben Zuckerman

For the super-Earth GJ1214b the lesson is to be careful about making conclusions. Early suggestions that this might be a “water world” or have a cloudless hydrogen atmosphere have since been superseded by models featuring a haze of hydrocarbon compounds (like on Titan), or grains of potassium salt or zinc sulphide.

While the search for Earth-like planets continues using ground- and space-based telescopes, exoplanetary scientists are eagerly awaiting the launch of the James Webb Space Telescope JWST.

That immense telescope, scheduled for launch in around October 2018, could mark the true beginning of the exciting search for distant atmospheric biomarkers and exoplanetary life.

Thursday, November 26, 2015

100 years of general relativity

a nice animated video to explain einstein's general relativity in 3 short minutes!

you might also be interested in a recent conversation article by michael brown on "why einstein's general relativity is such a popular target for cranks".

i get A LOT of emails from random people claiming they have proven einstein wrong, and this offers some insight as to why that might be. 

Tuesday, November 10, 2015

sky schemes: a song

My unofficial hack at last week's .Astronomy 7 conference in sydney was to perform a song i wrote recently called Sky Schemes.  Luckily, Becky recorded it for all to hear!

Sky Schemes
By Amanda Bauer (2015)

On winter nights when I was a girl
I’d go to her house after school
We’d play game, make things, discover our dreams
I’d walk home through the dark remembering our schemes

I’d look up at the stars, shining overhead
Make constellations that I saw instead

Of those Greek ones, Islamic ones, they are so old
There are native ones, Indigenous ones, but we’re seldom told
I made one up. It was a bird, wings spread wide
I’d look for it, find it, feel so much pride

So look up at the stars, shining overhead
Make constellations that you see instead

There are new ones, trues ones, you will see first
Share them with us, through us, satisfy your thirst
To know things, understand, how we are here
No true answer you’ll find, but it will become clear

The questions that matter are changing all the time
Rely on your instincts, empower your mind

And then look up at the stars, shining overhead
Make constellations that you see instead

Photo by Andy Green

Photo by Andy Green

also, another quick announcement that you might suspect from the photo below... go to THIS LINK and keep exploring until you uncover the surprise :)  this reveal was also made as a result of .Astronomy hack day.

Photo by Andy Green

Sunday, October 11, 2015

berkeley astronomer guilty of sexual harassment

the best thing i can say is that sexual harassment in academia is being discussed in the media and it's finally out in the open that berkeley's well known exopolanet astronomer, geoff marcy, is a serial sexual harasser.

you see, for YEARS (since 2001) reports of his inappropriate actions have been known to his undergraduate and graduate students and postdocs, and formal complaints were brought to him in 2004.  he was told that his massages and touches and attempted kisses and GROPES were unwanted and inappropriate.   he knew this, even though in his recent semi-apology he tries to express "how painful it is for me to realize that I was a source of distress for any of my women colleagues, however unintentional."  i'm calling bullshit.

surely his senior colleagues knew these formal complaints had been filed as his reputation raged among the international astronomers who worked on his teams. but did any of his colleagues step up and say to him "Dude, this is not cool.  STOP IT!"  nothing of the sort is on record, although i'd love to be corrected on this.

so marcy persisted.

and what happened during the last 15 years?  an informal network of women trying to protect each other from his behaviour naturally formed, warning younger colleagues to "watch out" for him at major conferences.

as the altlantic describes,

Marcy leveraged his considerable fame and power in the world of astronomy to build a nearly consequence-free bubble around himself.

the sad reality is that berkeley is moving forward with NO disciplinary action AT ALL!  this i do not understand.  YET AGAIN the burden to "deal" with the repercussions of this horrific behaviour is placed on the victims.  <::sarcastic truthiness::=""> poor mr famous scientist, please act within the rules already in place for all scientists in this university or else we may just have to be courageous enough to discipline you. </>

i can guarantee that marcy is not the only sexual predator whose actions have been protected by cowardly colleagues and universities.  two years ago i wrote about my personal experience as a victim of sexual harassment as a PhD student at the university of texas at austin (UT).  i took steps to lodge a formal complaint, but was thwarted by senior faculty.  i chose to just "deal" with it and get on with my studies, knowing that there had been others and would be more victims of this man's pathetic advances.

i became part of the internal network of women warning other women to avoid him, while male students sat by saying things like "that sucks" and senior staff went on protecting him - for DECADES.

YES IT DOES SUCK.  and it's not fair.  this man continued to work and teach at UT and FINALLY was lightly forced into early retirement so the department could once and for all stop figuring out how to suppress the complaints of his victims and his continuing bad behaviours.    this professor was not famous in his field.  he was not bringing in large grants.  his research was nothing of note.  but he was surrounded by a "good old boys" network that protected him just the same.

the only action of consequence against marcy so far is that he has been asked to skip one of the biggest professional astronomy meetings in the world this january.  imagine this - instead of telling women to be cautious around known sexual harassers - TELL THE HARASSERS TO STOP FUCKING HARASSING PEOPLE and/or STAY AWAY!

so thank you to yale astronomer and American Astronomical Society (AAS) President Meg Urry who says this about her intolerance for harassment at the conference:

Sexual harassment usually involves a question of a power imbalance. [...]  And one of the saddest things I’ve ever seen is when a young woman realizes that the extra attention she is receiving from an older, male astronomer is not related to her science.

Come on astronomers, let's expect MORE from our senior colleagues and tell them so.  it's worth it to hold them to humane behaviour standards, regardless of their scientific achievements or potential.  

Sunday, September 13, 2015

collecting SAMI galaxies

I've been up at Siding Spring Observatory visiting this beauty this week.

The dome of the 4-metre Anglo-Australian Telescope
I enjoy walking around the dome's catwalk to see the views in all directions.

Hello from the catwalk!
 The first night provided a lovely (cloudy) sunset.

But then the skies cleared BEAUTIFULLY for most of the observing run and the Milky Way glowed brilliantly across the early evening sky.

We have been using the SAMI instrument during this run to observe over 100 galaxies so far!

Perched at Prime Focus with SAMI
Kristin was the telescope operator for the beginning of the run. Here she is with the original control panel that was installed 40 years ago!  while it still looks roughly the same - systems and displays have been upgraded over the years :)

we had some time for enjoying the clear night skies while exposing with the big telescope

The Magellanic Clouds and the AAT dome. (Credit: Jesse van de Sande)

Milky Way (Credit: Angel Lopez-Sanchez)
And we may have started to write a few songs for "SAMI - then Musical"  ;)

Monday, August 10, 2015

A 2dF night at the Anglo-Australian Telescope

A new video from AAO!

"A 2dF night at the AAT" assembles 14 time-lapse sequences taken at the 4-metre Anglo-Australian Telescope (AAT) located at Siding Spring Observatory NSW, Australia. This time-lapse video shows not only how the Two Degree Field (2dF) instrument works but also how the AAT and the telescope dome move in tandem, and the beauty of the Southern Sky in spring and summer.   
The video is 2min 50sec long and combines more than 4000 frames obtained using a CANON EOS 600D with a 10-20mm wide-angle lens. All sequences were taken during September and November 2011 by astronomer Dr Ángel R. López-Sánchez while he was working as the 2dF support astronomer for the AAT. The music is the song “Blue Raider” from Composer Cesc Villà's album “Epic Soul Factory”

Saturday, August 8, 2015

the star talker - neil degrasse tyson

what a fun, almost surreal evening talking with Neil DeGrasse Tyson.

pre-show with Neil deGrasse Tyson
He reminded us to "look the hell up every once in a while" and not to take evidence of science and technology in our everyday lives (phones!) for granted.

I didn't realize for the first few minutes that we were on the HUGE screen behind us on stage!

one of the best parts about spending time with neil is realising that he is constantly observing the world around him and thinking about it, questioning it, interpreting it - not taking it at face value. it's something we should all do more, as it keeps us present in the moment and prevents us from not appreciating all the amazing things around us.

With Neil DeGrasse Tyson after our conversation in Melbourne, thanks to Think Inc
I'll host his next show in brisbane next weekend, so there's still time to let me know what questions you would ask him if you had the chance!

also, should i wear the boots again, or change it up?  serious questions of the universe....

Wednesday, August 5, 2015

Hosting Neil DeGrasse Tyson

dr neil degrasse tyson is one of the most recognised scientists in the world right now and he has recently embarked on an australian tour!

i'm thrilled to report that i will be hosting two of his shows: August 7th in Melbourne and August 16th in Brisbane!

there are still tickets available for each show, so if you're around, please join us!

what does hosting mean?   i will pop up on stage first and welcome everyone to the event then introduce neil and invite him to the stage.  he and i will then sit in a couple comfy chairs and have an hour long conversation on topics ranging from pluto to science education to alien life to the (lack of) edge of the universe!

then a few audience members will have a chance to ask him questions as well.

i'm thrilled for this opportunity and will hopefully have a full report after the events are finished. here we go...!