The WTF star is possibly the weirdest star I have ever come across
like it is probably the most observed star in the history of astronomy and yet
even with all those observations we still have no idea what it's doing so
the WTF star is also known as the Tabby's star or Boyajian's star after
Tabby Boyajian who was the lead author on the paper in 2015 which announced that
this star had been found by citizen scientists on the planet hunters project
this was a website that asked the public to classified data from the Kepler space
telescope which was observing stars brightnesses so when a dip in the star's
brightness was seen it could be an exoplanet transiting in front of That
star so basically people were asked to label where the dips were on light
curves now these are probably already been looked at by computer algorithms
but you can only train a computer to look for what you know you can only
train it to look for what you expect to see you can't train it to look for the
weird things that you don't know are actually interesting and that's where
humans come along because as soon as they see something that looks weird
they'll flag it and that's what they did here with the way to first start they
were seeing 30 day chunks of observations over its brightness and
people were flagging them as really strange or interesting or a giant
transit ie something that was like really really long or really really deep
and so the team then noticed that all these things that the volunteers were
flagging were all from the same star and instead of having very regular dips in
brightness that were always the same depth because they were caused by a
single planet just orbiting around its star and causing a dip in the brightness
every say 10-20 days however long it was none of these transits were the same
depth none of them were the same length they didn't seem to have any form of
periodicity like they were random they didn't come every certain number of days
and it wasn't like there was one of the same depth every number of days with
lots of little ones in between there was no pattern to it at all it looked
completely random and it wasn't like working with only a little bit of date
here it's like it was like random statistics this was four years worth of
kepler space telescope data in which you had one dip that lasted for days and yet
you had one dip that was so deep it dipped the star by about 0.5% of its
brightness which doesn't sound like a lot because but if you think about it
planets are quite small with respect that's off so they don't cause a huge
dip in brightness so 0.5% is actually really big for a planet
transit so Boyajian et al. 2015 where the first paper to really describe this
star and they did try and look for some periodicity that you know couldn't be
seen by the human eye when you're looking at a light curve just because
there's so much noise in there to dig through but if you sort of process it
with an algorithm and get out the difference between successive dips you
find that there is a peak sort of a dip every 0.88 days that's a
very very short period you know if you have a planet that would be very very
close into the star going very very fast so they said what they were seeing there
was actually the star rotating and so you're seeing all the variability on the
star surface coming back every point eight eight days you know the same as we
see for our Sun we get some spots and so as they rotate out of our view and into
our view will then get a period of that sunspot moving around the Sun same thing
is what they detected here but that everything else was random still so this
stars actually in the constellation of Cygnus pretty famous constellation
pretty easy to spot well it looks like the Swan and the Milky Way runs through
it but this star is about 1,400 light-years away so it's pretty faint
you can't see it with the naked eye you need like a five-inch telescope or a bug
and a really dark sky to do it but it does mean that this star had been
observed way back in the 1890s on saw scopes were good enough to spot it and
it's been observed ever since then except these were only
like single observations it wasn't like it was being observed you know sort of
multiple times in a day like what Kepler did in order to be able to spot those
dips in brightness and in variation and random periodicity that was going on
which means it was one of those unknown knowns way up till 2015 something that
we knew of but didn't really know about but people realize that studying
these historic observations of the star could actually tell you more about it
and have actually found it the average brightness of this star has actually
dimmed over time since 1890 in fact is decreased its brightness overall by
about 20 percent which is unheard of for this kind of star of this mass of this
type it means that it's dimming on average for about 0.34 percent every
year but because it was unheard of it meant that people wondered well our
stars of this specific type and mass all doing this they all didn't get this
weird or not and so they studied 193 more stars the same mass and type and
found that none of those were undergoing this dimming so this was another really
strange property of the water 4 star there's also very recently when another
paper come out just last month by Rappaport
and collaborators and they have found another starlet on explicable as well
this one is called epic two four nine seven zero six six nine four so this
star had been observed in Phase two of the Kepler mission what was called k2
was observed over 87 days and in that time was found to transit 28 times again
though no period it to it at all they were completely random except this
one all of the transits were pretty much exactly the same death which again is
very very strange but again completely different to the water first star and so
any hypothesis you come up to explain this kind of random dipping in the
star's brightness you also need to be able to explain why some of them might
all be the same debt and some of them might all be completely different debts
as well so like a lot of unsolved mysteries there are a lots of hypotheses
floating around that try to explain what we're seeing with this star the problem
is that not all of them fit the data and the thing is a couple of years ago
people announced oh we've decided which one it is but then more data came to
light and it's gone back to being an unsolved mystery again and the reason
that so many have sprung up is because there's so much data on this star not
just the original four years worth of Kepler data but once it was a
that it has been identified as a strange star there was a shout put out to say if
you're at an observatory at any point or if you're an amateur astronomer where
the telescope please observe the brightness of this star and report back
please take a spectra of this star and report back and then send them to hobby
boy adjourn so that she can go through them and figure out what is going on for
this star and with all of that data it means that we've been able to rule out
certain hypotheses so one that was put forward for example was that there was
this huge debris field around the star so for example maybe a collision between
two planets had occurred which is vaporized those planets to the molten
flung out a load of molten rock which is then solidified into this sort of like
debris cluster around the star thing is if you have that the star heats that
material that material starts to glow in the infrared and so we can spot it now
people have constantly observed tabi star in the infrared and found that
there's no infrared excess they call it the star itself will give out infrared
and you should see an excess of light around it but that isn't there so that
rules out that sort of debris field theory that also ruled out the favorite
theory that was sort of agreed upon in 2017 and sort of announced to the world
that it was this like field of comets around the star very similar like the
Oort cloud in the solar system but much closer into the star and also by the
notion that you know you need something that's gonna work 22% of the light from
the star and comets aren't gonna do that and then of course the big thing that
hit the headlines alias it's never a lian's little green men turned out to be
rotating neutron stars which we called pulsars quasars turned out to be
accreting supermassive black holes gamma-ray bursts turned out to be
supernovae it's never a lian's but what if it's not what bond paper did
suggest was that it could be this Dyson swarm mega-structure put into place by
alien civilization around their star to essentially draw power from it you can
imagine it is like a load of solar panels in a big array around the star
that they would draw energy to power their civilization that was completely
ruled out in 2017 by Meng and collaborators when they found that the
dimming is actually wavelength dependent so you get more dimming in the
ultraviolet and you get less dimming in the infrared that's really significant
because you have any solid object whether it is solar panel from an alien
civilization or whether it is like a solid planetesimals or a moon or a
planet or comment whatever they would all block the all wavelengths of light
equally they wouldn't cause wavelength dependent dimming so essentially any
theory that attributes all of these transits to anything larger than a dust
particle got ruled out by the magnetar result in 2017 so even though it's not
aliens SETI have still got it on its watchlist they've tried to see if they
can detect radio signals or any laser activity from the star nothing as of yet
yet so there are two theories then still up in the air that haven't really been
ruled out yet by any other theory one of them is this idea of dust around the
star and instead of a cloud or a disk that's completely irregular you know
it's very very clumpy and the clumps cause this sort of dips in the star's
brightness that look like a planet transit but obviously they're randomly
scattered so there's no periodicity to them and they're irregularly clumped so
there's no pattern in how deep the transit is either
the thing is though with the dust we should have seen it in the infrared so
this idea of an infrared excess again where you have the infrared light from
the star and then you should see an excess around the star as well which we
haven't we know some stars are dusty and have these sort of dips because of the
dust that they have an infrared excess so it's really important that we keep
observing it in the infrared perhaps it's just incredibly faint and
we need best telescopes to see it or perhaps it's not there we don't know
still more observations are needed then there's magnetic fields the long-running
joke in astronomy that nobody understands magnetic fields nobody ever
considered the magnetic fields and everyone always forgets about magnetic
fields well the water first are could be due to magnetic fields if you have a
very complicated magnetic field it could affect how your Stars outer atmosphere
is cooling what we call the photosphere and so that could affect its brightness
and cause this strange variability that would be completely unpredictable
because magnetic fields are random and a complete
unpredictable and there are other known stars in the Kepler field that have been
observed unknown to have very strong magnetic fields and they have sort of
strange variation in their brightnesses as well but nowhere near as bad as tabby
star the way to first star with these ridiculously deep and random dips and
brightness so perhaps to verify that theory we need to do some more
simulations of a very extreme magnetic field around a star and see whether it
can cause such extreme dips in the brightness like had been seen around the
water first off the good news is that right now from the 18th of June to the
11th of September Tess the transiting exoplanet survey satellite which is the
follow up to Kepler is actually observing the water first star and it's
gonna be observing it every two minutes that kind of high cadence observation is
so important for us to be able to understand these dips in brightness you
know from the very beginning to the very end of the different brightness what
really happens as the dip starts and ends and cannot give us clues to what's
going on now there's no guarantee that will actually see a different brightness
during that sort of full month period that Tess is observing it because
they're completely random we can't predict if one's gonna happen in that
time if there isn't a dip then it's just a waiting game it requires people on the
ground to keep monitoring the star and seeing if it starts to dip in brightness
and then that happens a big shout will be put out worldwide essentially
astronomers assemble the water first star is dipping again we need as many
observations as we can to try and figure out this unsolved mystery but another
paper come out by rapid or Rappaport wrap a torch no put up a port report
light a transiting exoplanet search and the reason this and the cool thing is
that the cool thing is and the cool thing is since it was first spotted it
and the cool thing is that
you