this is the discovery files podcast from the us national science foundation with the excitement
of new images coming from the james webb space telescope pointing everyone's eyes to the skies
a flashing star some 3000 light years away has captured the attention of a team of curious
astronomers who believe they may have discovered a neutron star that is consuming a companion star
this type of event is known as a black widow binary when two stars are bound to one another
by gravity and the neutron star created by the supernova of a giant star has a super dense
collapsed core and is feeding on its partner like a black widow spider we spoke with joseph
e pesce an astrophysicist with 30 years of experience in a program director at the nsf
director for mathematical and physical sciences division of astronomical science dr pesce can
you tell us what a binary star system is stars form out of collapsing gas clouds they turn on
and they start fusing and shine and produce heat and light and energy just like our sun our sun is
isolated in space it has no stellar companion that's that's gravitationally bound to it lots
of planets of course but there's not a stellar companion and on the contrary most stars
are formed with another companion if there's another one so there's two stars we call that
a binary star system where they are locked gravitationally and they orbit each other
and so that's the more common way that stars are formed in the universe so in a binary star system
usually the stars have the same mass mass is important for the subsequent
life cycle of a star the more massive star is the faster they consume their their fuel
and their lifetimes and while we have you can you tell us why the black widow variation is rare
it's rare because you know binary stars can be in multiple configurations they can be very close
they can be further apart and the further they are apart the wind is still coming off of the
evolved companion the neutron star in this case but it's far enough away that it's not
damaging the nearby companion if they're too close then that wind can ablate can remove the outer
atmosphere of the companion star supported in part by nsf researchers at mit were studying the
luminescence of stars looking to add to the dozen known widow binaries when they found this neutron
star with a companion orbiting every 62 minutes a binary system of this type alone is a refined but
they were even more amazed to see what appears to be a third distant object orbiting the pair
every ten thousand years this wide orbit companion is a rare low metallicity cool subdwarf star
and would make this system the first of its kind ever observed to hear more about this discovery we
spoke with dr kevin burdge one of the researchers at mit who found this unique system dr burdge how
did you see these stars well we have visible light curves so these basically measurements of how
bright something is versus time for over a billion stars now thanks to the spiky transient facility
uh ztf was largely funded through the national science foundation that's its biggest thunder
and so now basically for every part of the sky in the northern hemisphere we've got thousands
of images on this 48 inch telescope and what i do is i basically look at each of the stars in
those images and say what is the star doing over these thousand images and i specifically look for
stars that are getting brighter and fainter and brighter again and fainter and repeating that on
a particular schedule and it just so happens that these black widow systems are some of the most
extreme things that get brighter and fainter very few things get brighter by factors of more than
10. and so this is really the first time that someone has used only visible light to try to
find a neutron star of any kind to my knowledge there's a strong possibility that this could
even be something like completely different than anything we've seen before and we've interpreted
it as a black widow because it behaves most similarly to those of the things we know but
something that i'm trying to keep an open mind until we see the pulsar i'm also still considering
whether there are other interpretations to explain what we're seeing here whatever
it is what is clear is we've never seen something quite like this object before what does your
research on this binary star system teach us so this is a triple system actually there's like an
inner binary with an hour orbital period that we think is a black widow there's an outer companion
and a 10 000 year orbit going around those that's actually kind of unexpected and the reason is is
when you form a neutron star from a star what happens is it's called a core collapse supernova
basically the star collapses in on itself to form the neutron star core but during that very violent
event there's also an explosion that explosion is usually not symmetric it doesn't eject the matter
out in exactly isotropic distribution of the sphere usually more gets ejected towards one side
if you inject too much matter towards one side what happens is you basically take the core in
the opposite direction and conserve momentum these are called neutron star natal kicks so we
think most neutron stars are probably born with these kicks and we see evidence that they move
with pretty high velocities uh to corroborate that the problem is if you have a wide triple
with a companion in a 10 000 year orbit you can't really kick the neutron star very much
or it would just go flying off in one direction and leave behind this white companion because it's
not very strongly gravitationally bound i mean so one thing this system is letting us probe is if it
is indeed a black widow it's testing neutron star kick physics um because it means either the system
must have formed a neutron star before it became a triple or if it was already a wide triple when
you form the neutron star it had to form out of a really low kick mechanism so really symmetric
way of collapsing and making the neutron star so that's like a very specific bit of physics that
we can study from the system i think the bigger picture fun thing is that we've got hundreds of
billions of sources of light and each one of them is a little experiment that lets us test
these little details in our models the national science foundation has largely been responsible
for driving a lot of these instruments that are making this possible and the bigger thing on the
horizon is the vera reuben observatory which is also a huge national science foundation effort
that's going to be the center piece of my research for the next five to 10 years how far away is this
binary yeah so it's about one kiloparsec which is about 3 000 light years um to give reference the
distance to the center of the galaxy from earth is about eight kiloparsec so one kiloparsec is kind
of in our local part of the galaxy it's getting kind of far away but still close enough that we
can see it and that's the key these things are really faint because the irradiated objects are
brown dwarfs so if you put them too far away you just can't see them with something like
ztf on a one meter telescope and knowing that we're measuring distance by light moving over time
can you tell us how long ago what you've observed occurred yeah so about three thousand years ago
um we're seeing it uh delay because the light travel time is so long from the system finally do
you have any advice for young people interested in astrophysics this is a great time to get into the
field it's really being revolutionized because of advances not just in our abilities to build
bigger telescopes and that's been something that's been happening for the last 50 years
the big game changer has been electronics digital cameras have been a huge invention
and the thing is is they keep getting better and the other thing that's improving is our ability
to analyze that data so something i spend a lot of time doing is writing algorithms on computers
that takes all those images and actually finds something interesting the needle in the haystack
and so i would say it's a great time to get into this because there's so much potential coming in
the next 10 to 20 years because of our advances in digital technology both like computing technology
like gps but also digital cameras all we need to do is basically have that keep advancing and keep
installing it on telescopes and use it to analyze the data special thanks to dr kevin burge dr
joseph pesce terrence after henderson adam eggers and dena headlee for the discovery files i'm nate
potker please subscribe wherever you get podcasts and if you like our program consider leaving a
review discover how the us national science foundation is advancing research at nsf.gov