NASA's newest Planet Hunter has returned an amazing image containing thousands of
stars that contain a sample of the extrasolar planets it will soon discover.
Welcome back to Launch Pad, I'm Christian Ready, your friendly neighborhood
astronomer. The Transiting Exoplanet Survey Satellite, or TESS, was launched in
April 2018 and spent the last four months getting itself into the right
orbit and generally commissioning its instruments and getting ready for
science observations. On August 7th, TESS completed its first set of science
observations and NASA released the resulting images - and they're spectacular.
The image was taken with TESS' four onboard cameras, each of which contained
four detectors mounted in a 2x2 array. The result is a wide-field image that is
24 degrees across and spans up to 96 degrees from the ecliptic to the poles.
That's an enormous strip of the sky. The first image is dominated by the Large
and Small Magellanic Clouds. These are small dwarf irregular galaxies that are
satellites to our Milky Way. They're home to hundreds of millions of stars and lie
about 160 thousand light-years from Earth.
Just north of the small Magellanic Cloud is a globular cluster called NGC 104,
also known as 47 Tucanae. This is a swarm of several million stars that are a mere
ten thousand light-years from Earth. There are several other globular
clusters in the images as well as some distant background galaxies. But the real
stars of this image are the...well the stars of this image. Some of the stars
like Beta Gruis and R Doradus are so bright, they saturate the detectors
causing electrons to spill over into the adjacent pixels. TESS does its work by
making several images of the same sector of the sky at any given time.
First it completes a sequence of two second exposures that are combined to
form a single 20 second exposure. The light from about 1,000 pre-selected
stars are measured and recorded. These stars are being monitored
for sudden variations in their brightness over time. These brightness
variations are usually caused by fluctuations on the surfaces of the
stars. This allows astronomers to probe the interiors of these stars and
understand their internal structures. This is called asteroseismology, and it's
a great way to learn about a star from afar. See what I did there, I said star...
ok fine. 60 exposures are combined to form a
single two minute exposure which then gets automatically scanned for the
periodic brightness fluctuations in several thousand stars at once. These are
the tell-tale signals of a planet transiting across its host star,
subtracting just a tiny fraction of the star's light. After 1800 exposures,
they're combined to form a single 30-minute exposure which is stored
onboard the spacecraft along with the rest of the star monitoring data, then
the process repeats again for about 2 more weeks until the spacecraft returns
to its closest approach to Earth and downloads its data when the data rate is
the highest. Then it swings back out high above the Van Allen radiation belts and
begins another two weeks of science. TESS spends about 27 days monitoring each
sector of the sky. Then it pivots by 24 degrees to begin a new sector. As a
matter of fact, as of this filming TESS is already working on sector two! After a
year TESS will complete its survey of the southern sky. Then it'll flip 180 degrees
and begin its survey of the northern sky. After its two-year mission, TESS will
have served about 85% of the sky examining over 200,000 stars for nearby
exoplanets. It's expected that TESS should be able to detect anywhere from
4,500 to as many as 20,000 new exoplanets But even if TESS ends up at
the low end of this range, it will have more than doubled the number of
exoplanets that have been discovered since 1992. And by the way, that's just
for the nearby bright stars! The reason astronomers want to study
exoplanets that are close at Earth is because the closer the stars are, the
brighter they appear, making their planets much
here to study. TESS' predecessor mission, the Kepler space telescope, revealed that
most stars in fact have planets around them, and that most of these planets
range in the size between Earth and Neptune. These are the so-called "Super
Earths" and we don't seem to have anything quite like that here in our own
solar system. But because most of Kepler's targets were distant and
therefore very faint, there was little else that we could really learn about
these planets other than their sizes and distances from their host stars. But TESS
will build a catalogue of nearby exoplanets that can be studied in
greater detail with the James Webb Space Telescope, and ground-based telescopes
like Keck, and the upcoming super telescopes such as Giant Magellan,
Thirty Meter, and the Extremely Large Telescope. these follow-up studies will let us
learn much much more about these planets such as their masses, their densities, and
maybe even their atmospheric compositions. TESS is designed for a
two-year primary mission, but it has an orbital trick up its sleeve that would
allow it to remain in the exoplanet business for a lot longer. It's
elliptical orbit is highly inclined to Earth's. This allows TESS to spend most
of its time high above the Van Allen radiation belts, allowing it to take
images that are free of noise and interference. But Earth's tidal forces
will intervene and gradually destabilize TESS' orbit. But TESS' mission
designers were clever enough to ensure that TESS completes two orbits for every
single orbit of the Moon. This allows the Moon to counteract Earth's tidal forces,
ensuring that the spacecraft should remain in a stable orbit for at least a
decade. Imagine what we could learn if TESS was given a 10-year mission to seek
out strange new worlds. So what are you looking forward to learning from the
TESS mission? Let me know in the comments below and I'll be sure to check it out.
And if you'd like to join me on this journey through this amazing universe of
ours, well please make sure to hit that subscribe button and ring that
notification bell so that you don't miss out on any new videos. Until next time
keep watching the skies. [BEEP] ...of a planet transiting across its host star... [airplane overhead]
it's also an airplane transiting across my yard! [airplane noises] Grrr...