An amazing phenomenon is happening today that won’t happen for another 13 years — Mercury is passing in front of the Sun! What exactly is going on?
so it's very exciting day here on planet earth. Earth and all of the planets in
our solar system are orbiting in a plain around the Sun and so what that means is
that on very special days when the geometry is aligned perfectly
we can watch the planets that are interior to us actually cross the face
of the Sun just glide across the face of the Sun and today that's happening
mercury is passing in front of the face of the Sun from the East Coast we can
watch it pretty much all morning long.
NASA uses events like this one to find planets around other stars. How does that work?
so it's basically the exact same phenomenon that we're seeing here today
with mercury passing in front of our Sun we can use that now to look for planets
transiting across the face of their suns or stars. So when we look out at the
nearby stars we're looking for transits and right now we h ave a mission in space
called TESS, the transiting exoplanet survey satellite, measuring transits to
discover planets around nearby bright stars and TESS is very capable of
measuring just the tiniest dip in light from a star when a planet like the earth
passes in front of a star like the Sun it's 84 parts per million fainter and so
that's a really tough measurement to make but we have the technology now to
do so and we're finding planets through this method.
We’ve always been told not to look directly at the sun. So how can our viewers see today’s event?
so it's very important not to look directly at the Sun even when exciting
things like planets are transiting in front of the Sun but there are all kinds
of ways that you can enjoy this event happening. One of the most amazing views
you can get is on the internet. NASA will be showing a near live stream of this
event from the Solar Dynamics Observatory and this is a solar
telescope in orbit right now in space that is very powerful and as a solar
observer and it's going to have a great view of mercury transiting. So tune in on
the internet if you're lucky enough to live near a science museum or an
astronomy club that is setting up telescopes to show you this in real time
go online and see if you can be there in person for that as well.
What do transits and eclipses teach us about our own solar system?
so they've been so important historically in giving us a sense of
what our solar system looks like and how big it is. It's easy to predict when
transits happened because we understand the laws of nature that all the planets
in our solar system follow in their movements. So for hundreds of years
astronomers could predict transits of mercury, transits of Venus, and they would
travel for hundreds of miles to observe these events was one of the first ways
we started to really get a hold on the size of our solar system the Sun is 93
million miles from Earth and the first measurements of that distance were made
by measuring transits and working with the geometry to figure out our distance.
Where can we learn more about stars and planets?
so there's a huge amount of information online and growing all the time a great
place to start for information about transits and tests would be in NASA at
nasa sun or at nasa universe.