Well first off, Hello, this is my first time making a thread here at ATS so bare with me.
Anyway I'd like this thread to serve a few purposes, so i will begin by stating those purposes before i get into the meat of the thread.
To educate people on Exoplanets, how they are found and a basic understanding of light curves.
To Encourage you to join the hunt
And to briefly discuss the problems I've seen with members here at ATS whenever there is an announcement made by NASA.
As you may have heard NASA has announced it will be expanding it's list of Exoplanet Candidates on February 2nd, however there is some more info
you may have not heard about this. Today (February 1st), the Kepler Team will also be releasing more data to the public (light curves of distant
stars in the search for
planetary transits and/or Eclipsing Binaries).
In order to understand what NASA is making announcements about, you should probably understand what Exoplanets are, how we find and detect them,
the difference between an exoplanet candidate and an exoplanet, and understand just how much data we have already collected.
Exoplanets, a shorter version of the same term, Extrasolar Planets, are planets that exist outside (exo) of our solar system. Their existence was
speculative until 1992 when radio astronomers Aleksander Wolszczan and Dale Frail announced the discovery of planets around another pulsar, PSR
1257+12, which was quickly
confirmed and generally thought of as the first definitive exoplanet. 1995 however, was when the first definitive announcement was made that a Main
Sequence star (51 Pegasi, 51 light years from earth) much like our own sun was confirmed to host an orbiting planet. It was this discovery in 1995
with improvements in high
resolution spectroscopy that opened the gates to a vast amount of more confirmed exoplanets. Another system discovered in 1988 that was thought to
have hosted a planet, but such a claim could not be definitively proven until 2002 with improved techniques. As of January 20th, 2011, 519
Extrasolar planets have been confirmed
through various methods of detection.
So how are these planets detected? Well, there are quite a few methods of detecting a planet around a star. Such methods include: Radial Velocity
(or the Doppler Method), the Transit Method (the one Kepler uses and i will be focusing on later), Transit Timing Variation, Gravitational
Microlensing, and Direct Imaging. For the purpose of this thread I'll only go into depth on the Transit method but I'll give a brief explanation of
each method so you don't have to go look them up.
1) Radial Velocity and the Doppler Effect
. Planet's don't just orbit around their star, rather the star and the planet will both orbit around
the center of gravity in that system. Variations in the speed at which the star moves towards and away from Earth (Radial Velocity) can be detected by
the movement of the Star's spectral lines due to the Doppler Effect. Thus far this method has been the most successful with 369 confirmed
2) Transit Method
. Ill cover more of this method later on in the thread. But basically it measures the observed brightness of a star and looks
for slight dimming in the light due to transits, which could be a planet or an eclipsing binary. 114 confirmed planets have been discovered using this
3) Transit Timing Variation
. This method is a variation of the transit method and requires a known transit of an existing planet. Variations
in the transit of one planet can be used to detect the existence of another. WASP-3c was found using the transit of WASP-3b in this very method. The
variance in the duration of the transit can also be attributed to exomoons. A possibility that makes me appreciate the transit method, and the
seemingly uninteresting majority of Jovian planets discovered with this method. An expanse of even more possible habitable worlds when we look at
just how many moons the Gas Giant planets of our own solar system. 10 planet's
have been discovered using this method.
4) Gravitational MicroLensing
is the occurrence of a star's gravitational field acting like a lens that magnify the light of a distant star in
the background. However, this is only useful when two stars are almost exactly aligned in relation to the Earth. Not particularly difficult to
observe such occurance but the window of time available to use the micro lense isn't exactly "ideal", what with the constant motion of all celestial
bodies. 11 confirmed planets
have been found using this method.
5) Direct imaging
. The method I'm sure most all of you are familiar with. When you look up at the night sky and are able to see Mercury,
Venus, Mars, Jupiter, the rings of Saturn with the help of binoculars or a telescope...However, direct imaging is a very different story for
exoplanets and the extremely faint light from the
planets is almost always lost in the glare of their host star. Although recently, projects to upgrade scopes with new vortex coronagraphs have
increased the success of this method by blocking much of the star's glare. 15 confirmed planets
have been discovered using this method.
The image above shows the light from three planets orbiting a star 120 light-years away. The planets' star, called HR8799, is located at the spot
marked with an "X."
So now you've got a pretty good understanding of exoplanets and how they are found. But why am i so concerned with the Transit Method and why am i
telling you this? It has to do with the Kepler Telescope and the data that the Kepler Team has been releasing to the public. Kepler was launched on
March 7, 2009 and is a space-borne telescope equipped with a photometer to gather light intensity data over 30minute intervals for over 145 main
sequence stars in a fixed field of view. Well what makes Kepler so special? It is the increased ability to discover much smaller planets of a size
similar to that of Earth (with the smallest confirmed planet being Kepler 10-b, 1.4x the size of Earth). This increased ability may lead to the
understanding that rocky, terrestrial planets in fact populate more of our galaxy than Gas-Giants. An important idea considering the required
conditions for life (as we know it, big emphasis on this part here, big emphasis!) to take hold would be on those terrestrial planets rather than
Jupiter sized planets.
The Kepler Team has up to this point has found over 700 Planet Candidates
, 1800 Eclipsing binaries, and 9 confirmed planets
So what makes the difference between a planet candidate and a confirmed planet? Well the key difference is that at least 3 Transits must be
observed and follow up observations must have been met.
But the main impetus for making this thread was to encourage you to take part in going through the public data. So far Kepler has made available 30
days worth of data for 150,000 Main Sequence stars in which they found over 700 planet Candidates, and the community has found at minimum about 90
planet candidates and 50 eclipsing binary candidates. Pretty good for only thirty days. The announcement that you've heard about to be made on
February 2nd will be on the 2nd data set that is being released today and tomorrow.
Now why should people take part and help look through the public data, don't computers do a pretty good job of discovering these small dips? Yes,
in fact they do a wonderful job, but computers aren't perfect. The human brain does a wonderful job at observing and recognizing patterns and
anomalies, this is where you come in!
The easiest way to look through this public data is through the ZOONIVERSE team at Yale. You may have
seen other Zooniverse projects like GalaxyZoo, Solar Storm Watch, Moonzoo and a few others, but PlanetHunters.Org is the most exciting in my opinion.
PlanetHunters taps into the remarkable talent of the human brain and the mass number of people with a desire to investigate the cosmos to pluck out
transits that computer algorithms WILL have missed. An easy to use interface (quite a beautiful design i might add, coming from a web
designer/developer), helpful community, and awesome staff makes this website and community one you should consider joining, helping, and learning
with. Oh and I almost forgot to mention, yes, you do get credit when you discover a planet or eclipsing binary.
Im going to go through a bit about the PlanetHunters first run at the data now that the new (good stuff) information will be coming out today and
tomorrow. 150,000 stars and 1.2million classifications later, completed by the community and PlanetHunters, 3553 stars had been picked out that were
marked for a transit by at least 5 people
and were not already published by the Kepler team in the first data set. Out of this selection of
3553 stars an astronomy team at Yale working with the PlanetHunters staff went through and rated on a scale of 1-5 how promising the transits looked
for either a planetary transit or eclipsing binary system, narrowing down the data set to about 800 stars that fell into one or both of those
categories. Further yet, three senior "dip spotters" went through this list even more carefully rating them again and excluding every transit that
wasn't at a 4 or higher leaving quite a good number of planet candidates that would have been missed by planet hunting teams and data sifting computer
algorithms. Final Result
: 90 planet candidates and 42 possible eclipsing binaries.
Hopefully by now you either feel like signing up and sifting through the data that will nearly quadruple the current data, coming out today...Or you
may have a more humble approach upon criticizing NASA and planet hunters everywhere at their "slow progress".
NASA's Kepler spacecraft is one of the most powerful tools in the hunt for extrasolar planets. The Kepler team's computers are sifting through the
data, but we at Planet Hunters are betting that there will be planets which can only be found via the remarkable human ability for pattern
recognition. This is a gamble, a bet if you will, on the ability of humans to beat machines just occasionally. It may be that no new planets are
found or that computers have the job down to a fine art. And yet, it's just possible that you might be the first to know that a star somewhere out
there in the Milky Way has a companion, just as our Sun does. Fancy giving it a try?
To try and accomplish one of the last things i listed earlier in the thread im going to go through and explain Light curves a bit for those who may
find themselves venturing over to PlanetHunters.org to being searching and discovering for themselves. As i mentioned in the methods of discovery
section, the method used by the Kepler Space Telescope to discover planets is the Transit method, in which an extremely slight dimming of the Star's
light can indicate a transit of some sort. First, let's see what a normal lightcurve looks like, and for the sake of this thread and people who may
decide to head on over to Planethunters.org I will use their interface
to enlarge the view to be able to read it more clearly. I have
labeled a few things in orange on the picture. The star we are looking at in this picture is a star very much like our own sun, pretty close in size
and the same spectral type. When you look at the graph you will notice it is a scatter plot of little dots. Each dot represents one measurement taken
by the Kepler spacecraft of the stars light, each dot seperated by 30 minute intervals. The above picture is a star i have already classified but when
you go through classification of the star you will have a slightly different view. Not every star is quiet like this one, in fact many of them are
variable in their light output, meaning the apparent light as seen from Earth varies in intensity due either to blocking of some of the light in
space, or an actual change in the star's intensity. Our own star varies by about 0.1% over an 11 year cycle. So when you are classifying, you will
see a bubble that will ask you to try and identify what type the star is, Variable (including further regular, pulsating, or irregular), or Quiet (a
flat band of light like the above picture).
Now what do the transits look like? Well before i show some pictures, there is going to be 2 different types of "transits" you will encounter if you
decide to take part. One being a planetary transit, and the other not really a transit but an eclipsing binary. Eclipsing binaries are very different
from planetary transits, because it is in fact an eclipse of one of the stars in a binary system by the other and vice versa. In a binary system both
stars orbit around a common center of gravity (this same mechanic was mentioned earlier in radial velocity). The following GIF animation uploaded by
Wikipedia user Stanlekub demonstrates the nature of eclipsing binaries very well. When both stars are visible we see that highest amount of light, but
when the larger star totally eclipses the smaller we get a dip in the light curve. One way we distinguish this from a planetary transit is observing
this eclipse in reverse, when the smaller star only partially eclipses the larger star but still blocks out more light than the previous eclipse where
we can see a much larger dip
Okay now you can see some pictures of this in action courtesy of the PlanetHunters and the individuals credited with the discoveries.
This first picture is that of a possible eclipsing binary SPH10133951 first identified on 01/01/11 by planet hunters hillbillybob, samasinter,
cyril.tabut, liszu, echong, Vince1912, zephyr7, cmorford, Zaberish, honken, marrigo, robert gagliano, marcosmza62. I tried to pick an example with a
very extreme difference in the dips.
And this second picture is that of planet candidate SPH10007403 First identified on 01/01/11 by planet hunters snitramoriaj, jayrhns, rlangos, marmet,
howardhallmark, fbarnet, nhazel.
And finally i would like to address the NASA announcements. First off, these announcements which come very often and regularly aren't supposed to be
revolutionary and Earth-Shattering, though it's possible it may one day be, but expecting that type of an announcement EACH and EVERY time is going to
do you no good. Especially when you haven't bothered to look at what the announcement is going to be about, nearly every time I come across a thread
about one of these announcements, most of the replies consist of highly speculative ideas on what the announcement will be about. Typically, NASA has
either already said what the topic will be about or has been dedicating a significant amount of attention of one team/project towards the topic of the
future announcement. Such is the case with the conference tomorrow. If you had been paying attention to exoplanetology, which i won't assume you
have, you would know about the Kepler telescope and it's scheduled public data release dates.
Last time they released Quarter 1 of the Data they followed it with a conference of their planet candidates and confirmations. Now they plan to
release the data today, and follow that with a conference about guess what...Yup you got it, exoplanet candidates. And for those of you always want to
be disappointed with NASA going "Ahh only more boring planets" hopefully this thread may have humbled you on the amount of work, confirmation,
reconfirmation, rereconfirmation required, the difficulty at picking out buried planet transits in this field, and maybe even sparked some interest in
you. Astronomy and Astrophysics is cool damnit! Haha thank you.
The Kepler team will have a press conference on 2 February 2011, announcing their new candidates and releasing new data that will more than quadruple
the amount of data that is available on Planethunters.org. You can join the live broadcast on NASA TV at 1pm EST
Well now you know, and im hungry after writing this thread. Thanks for taking the time to read/comment ATS. Deny Ignorance!
Some good links:
- Confirmed Exoplanets
- Released Kepler Candidates
- Released Kepler Confirmations
- Eclipsing Binaries
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