Category: universe

Space Telescope Gets to Work

Our latest space telescope,
Transiting Exoplanet Survey Satellite (TESS), launched in April. This
week, planet hunters worldwide received all the data from the first two months
of its planet search. This view, from four cameras on TESS, shows just one
region of Earth’s southern sky.

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The Transiting Exoplanet Survey Satellite (TESS) captured
this strip of stars and galaxies in the southern sky during one 30-minute
period in August. Created by combining the view from all four of its cameras, TESS
images will be used to discover new exoplanets. Notable features in this swath
include the Large and Small Magellanic Clouds and a globular cluster called NGC
104. The brightest stars, Beta Gruis and R Doradus, saturated an entire column
of camera detector pixels on the satellite’s second and fourth cameras.

Credit: NASA/MIT/TESS

The data in the images from TESS will soon lead to discoveries of
planets beyond our solar system – exoplanets. (We’re at 3,848 so far!)

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But first, all that data (about 27 gigabytes a day) needs to be
processed. And where do space telescopes like TESS get their data cleaned up?
At the Star Wash, of course!

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TESS sends about 10 billion pixels of data to Earth
at a time. A supercomputer at NASA Ames in Silicon Valley processes the raw
data, turning those pixels into measures of a star’s brightness.

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And that brightness? THAT’S HOW WE FIND PLANETS! A dip in a star’s
brightness can reveal an orbiting exoplanet in transit.

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TESS will spend a year studying our southern sky, then will turn
and survey our northern sky for another year. Eventually, the space telescope
will observe 85 percent of Earth’s sky, including 200,000 of the brightest and
closest stars to Earth.

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Dark Matter 101: Looking for the missing mass

Here’s the deal — here at NASA we share all
kinds of amazing images of planets,
stars,
galaxies, astronauts,
other humans,
and such, but those photos can only capture part of what’s out there. Every
image only shows ordinary matter (scientists sometimes call it baryonic
matter), which is stuff made from protons, neutrons and electrons. The problem
astronomers have is that most of the
matter in the universe is not ordinary matter – it’s a mysterious substance called dark matter.  

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What
is dark matter
? We don’t really know.
That’s not to say we don’t know anything about it – we can see its effects on
ordinary matter. We’ve been getting clues about what it is and what it is not
for decades. However, it’s hard to pinpoint its exact nature when it doesn’t
emit light our telescopes can see. 

Misbehaving
galaxies

The first hint that we might be missing
something came in the 1930s when astronomers noticed that the visible matter in
some clusters of galaxies wasn’t enough to hold the cluster together. The
galaxies were moving so fast that they should have gone zinging out of the
cluster before too long (astronomically speaking), leaving no cluster behind.

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Simulation credit: ESO/L. Calçada

It turns out, there’s a similar problem with individual galaxies.
In the 1960s and 70s, astronomers mapped out how fast the stars in a galaxy
were moving relative to its center. The outer parts of every single spiral
galaxy the scientists looked at were traveling so fast that they should have
been flying apart.

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Something was missing – a lot of it!

In
order to explain how galaxies moved in clusters and stars moved in individual
galaxies, they needed more matter than scientists could see. And not just a little more matter. A lot … a lot, a lot. Astronomers
call this missing mass “dark matter”
— “dark” because we don’t know
what it is. There would need to be five times as much dark matter as ordinary
matter to solve the problem.  

Holding
things together

Dark matter keeps galaxies and galaxy clusters
from coming apart at the seams, which means dark matter experiences gravity
the same way we do
.

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In addition to holding things together, it
distorts space like any other mass. Sometimes we see distant
galaxies whose light has been bent around massive objects
on its way
to us. This makes the galaxies appear stretched out or contorted. These distortions provide another measurement of dark
matter
.

Undiscovered
particles?

There have been a number of theories over the
past several decades about what dark matter could be; for example, could dark
matter be black holes and neutron stars – dead stars that aren’t shining anymore?
However, most of the theories have been disproven. Currently, a leading class
of candidates involves an as-yet-undiscovered type of elementary particle
called WIMPs, or Weakly Interacting Massive Particles.

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Theorists have envisioned a range of WIMP
types and what happens when they collide with each other. Two possibilities are
that the WIMPS could mutually annihilate, or they could produce an
intermediate, quickly decaying particle. In both cases, the collision would end
with the production of gamma rays — the most energetic form of light — within the detection range of our Fermi Gamma-ray Space Telescope.

Tantalizing
evidence close to home

A few years ago, researchers took a look at
Fermi data from near the center of our galaxy and subtracted out the gamma rays
produced by known sources. There was a left-over gamma-ray signal, which could be consistent with some forms of dark matter.

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While it was an exciting finding, the case is
not yet closed because lots of things at the center of the galaxy make gamma
rays. It’s going to take multiple sightings using other experiments and looking
at other astronomical objects to know
for sure if this excess is from dark matter.

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In the meantime, Fermi will continue the search, as it has over its 10 years
in space. Learn
more about Fermi and how we’ve been celebrating its first decade in space.

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Gobble Up These Black (Hole) Friday Deals!

Welcome to our 6th annual

annual Black Hole Friday! Check out these black hole deals from the past year as you prepare to
head out for a shopping spree or hunker down at home to avoid the crowds.

First things first, black holes have one basic rule:
They are so incredibly dense that to escape their surface you’d have to travel
faster than light. But light speed is the cosmic speed limit … so nothing
can escape a black hole’s surface!

Black
hole birth announcements

Some black holes form when a very large star
dies in a supernova explosion and collapses
into a superdense object. This is even more jam-packed than the crowds at your
local mall — imagine an object 10 times more massive than the Sun squeezed into
a sphere with the diameter of New York City!

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Some of these collapsing stars also signal
their destruction with a huge burst of gamma rays. Our Fermi Gamma-ray Space Telescope and
Neil
Gehrels Swift Observatory
continuously seek out the
signals of these gamma ray bursts — black hole birth announcements that
come to us from across the universe.

NICER
black holes

There are loads of stellar mass black holes,
which are just a few 10s of times the Sun’s mass, in our home galaxy alone —
maybe even hundreds of millions of them! Our Neutron Star
Interior Composition Explorer
, or NICER for short,
experiment on the International Space Station has been studying some of those relatively nearby black holes.

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Near one black hole called GRS 1915+105, NICER found disk
winds — fast streams of gas created by heat or pressure. Scientists are still figuring out some puzzles about these types of wind.
Where do they come from, for example? And do they change the way material falls
into the black hole? Every new example of these disk winds helps astronomers
get closer to answering those questions.

Merging
monster black holes

But stellar mass black holes aren’t the only
ones out there. At the center of nearly every large galaxy lies a supermassive
black hole — one with the mass of millions or billions of Suns smooshed into a region no bigger than our solar
system.

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There’s still some debate about how these
monsters form, but astronomers agree that they certainly can collide and
combine when their host galaxies collide and combine. Those black holes will
have a lot of gas and dust around them. As that material is pulled into the
black hole it will heat up due to

friction and other forces, causing it to emit light.  A group of scientists wondered what light it
would produce and created this mesmerizing visualization showing that most of the light
produced around these two black holes is UV or X-ray light
.
We can’t see those wavelengths with our own eyes, but many telescopes can.
Models like this could help scientists know what to look for to spot a merger.

Black
holes power bright gamma ray lights

It also turns out that these supermassive
black holes are the source of some of the brightest objects in the gamma ray
sky! In a type of galaxy called active galactic nuclei (also called “AGN” for short)
the central black hole is surrounded by a disk of gas and dust that’s
constantly falling into the black hole.

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But not only that, some of those AGN have jets
of energetic particles that are shooting out from near the black hole at nearly
the speed of light! Scientists are studying these jets to try to understand how
black holes — which pull everything in with their huge amounts of gravity —
provide the energy needed to propel the particles in these jets. If that jet is
pointed directly at us, it can appear super-bright in gamma rays and we call it
a blazar. These blazars make up more than half of the sources our Fermi
space telescope sees
.

Catching
particles from near a black hole

Sometimes scientists get a two-for-one kind of
deal when they’re looking for black holes. Our colleagues at the IceCube Neutrino Observatory
actually caught a particle from a blazar 4 billion light-years
away
. IceCube lies a mile under the ice in Antarctica and
uses the ice itself to detect neutrinos, tiny speedy particles that weigh
almost nothing and rarely interact with anything. When IceCube caught a
super-high-energy neutrino and traced its origin to a specific area of the sky,
they turned to the astronomical community to pinpoint the source.

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Our Fermi spacecraft scans the entire sky
about every three hours and for months it had observed a blazar producing more
gamma rays than usual. Flaring is a
common characteristic in blazars
, so this didn’t attract
special attention. But when the alert from IceCube came through, scientists
realized the neutrino and the gamma rays came from the same patch of sky! This
method of using two or more kinds of signals to learn about one event or object
is called multimessenger astronomy, and it’s helping us learn a lot about the
universe.

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Get more fun facts and information about black
holes HERE
and follow us on
social media
today for other cool facts and findings
about black holes!

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Blowing Bubbles in the Gamma-ray Sky

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Did you know our Milky Way galaxy is blowing
bubbles? Two of them, each 25,000 light-years tall! They extend above and below
the disk of the galaxy, like the two halves of an hourglass. We can’t see them
with our own eyes because they’re only apparent in gamma-ray light, the highest-energy light in the
universe.

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We didn’t even know these humongous structures were smack in the middle of
our galaxy until 2010
. Scientists found them when they
analyzed the first two years of data from NASA’s Fermi Gamma-ray Space Telescope.
They dubbed them the “Fermi bubbles” and found that in addition to being really
big and spread out, they seem to have well-defined edges. The bubbles’ shape
and the light they give off led scientists to think they were created by a
rapid release of energy. But by what? And when?

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One possible explanation is that they could be
leftovers from the last big meal eaten by the supermassive black hole at the
center of our galaxy. This monster is more than 4 million times the mass of our
own Sun. Scientists think it may have slurped up a big cloud of hydrogen
between 6
and 9 million years ago
and then burped jets of hot gas
that we see in gamma rays and X-rays.

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Another possible explanation is that the bubbles
could be the remains of star formation. There are massive clusters of stars at
very the center of the Milky Way — sometimes the stars are so closely packed they’re a million times more dense than in the outer
suburb of the galaxy where we live
. If there was a burst
of star formation in this area a few million years ago, it could have created
the surge of gas needed to in turn create the Fermi bubbles.

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It took us until 2010 to see these Fermi bubbles
because the sky is filled with a fog of other gamma rays that can obscure our
view. This fog is created when particles
moving near light speed bump into gas, dust, and light in the Milky Way. These
collisions produce gamma rays, and scientists had to factor out the fog to
unveil the bubbles.

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Scientists continue to study the possible causes
of these massive bubbles using the 10 years of data Fermi has collected so far.
Fermi has also made many other exciting discoveries — like the the collision of superdense neutron stars
and the nature
of space-time
. Learn more
about Fermi and how we’ve been celebrating its first decade in space
.

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to follow us on Tumblr for your regular dose of space:
http://nasa.tumblr.com

Things That Go Bump in the Gamma Rays

Some people watch scary movies because they like being startled. A bad guy jumps out from around a corner! A monster emerges from the shadows! Scientists experience surprises all the time, but they’re usually more excited than scared. Sometimes theories foreshadow new findings — like when there’s a dramatic swell in the movie soundtrack — but often, discoveries are truly unexpected. 

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Scientists working with the Fermi Gamma-Ray Space Telescope have been jumping to study mysterious bumps in the gamma rays for a decade now. Gamma rays are the highest-energy form of light. Invisible to human eyes, they’re created by some of the most powerful and unusual events and objects in the universe. In celebration of Halloween, here are a few spooky gamma-ray findings from Fermi’s catalog.

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Stellar Graveyards

If you were to walk through a cemetery at night, you’d expect to trip over headstones or grave markers. Maybe you’d worry about running into a ghost. If you could explore the stellar gravesite created when a star explodes as a supernova, you’d find a cloud of debris expanding into interstellar space. Some of the chemical elements in that debris, like gold and platinum, go on to create new stars and planets! Fermi found that supernova remnants IC 443 and W44 also accelerate mysterious cosmic rays, high-energy particles moving at nearly the speed of light. As the shockwave of the supernova expands, particles escape its magnetic field and interact with non-cosmic-ray particles to produce gamma rays. 

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Ghost Particles

But the sources of cosmic rays aren’t the only particle mysteries Fermi studies. Just this July, Fermi teamed up with the IceCube Neutrino Observatory in Antarctica to discover the first source of neutrinos outside our galactic neighborhood. Neutrinos are particles that weigh almost nothing and rarely interact with anything. Around a trillion of them pass through you every second, ghost-like, without you noticing and then continue on their way. (But don’t worry, like a friendly ghost, they don’t harm you!) Fermi traced the neutrino IceCube detected back to a supermassive black hole in a distant galaxy. By the time it reached Earth, it had traveled for 3.7 billion years at almost the speed of light!

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Black Widow Pulsars

Black widows and redbacks are species of spiders with a reputation for devouring their partners. Astronomers have discovered two types of star systems that behave in a similar way. Sometimes when a star explodes as a supernova, it collapses back into a rapidly spinning, incredibly dense star called a pulsar. If there’s a lighter star nearby, it can get stuck in a close orbit with the pulsar, which blasts it with gamma rays, magnetic fields and intense winds of energetic particles. All these combine to blow clouds of material off the low-mass star. Eventually, the pulsar can eat away at its companion entirely.

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Dark Matter

What’s spookier than a good unsolved mystery? Dark matter is a little-understood substance that makes up most of the matter in the universe. The stuff that we can see — stars, people, haunted houses, candy — is made up of normal matter. But our surveys of the cosmos tell us there’s not enough normal matter to keep things working the way they do. There must be another type of matter out there holding everything together. One of Fermi’s jobs is to help scientists narrow down the search for dark matter. Last year, researchers noticed that most of the gamma rays coming from the Andromeda galaxy are confined to its center instead of being spread throughout. One possible explanation is that accumulated dark matter at the center of the galaxy is emitting gamma rays!

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Fermi has helped us learn a lot about the gamma-ray universe over the last 10 years. Learn more about its accomplishments and the other mysteries it’s working to solve. What other surprises are waiting out among the stars?

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NASA’s 60th Anniversary: What’s Out ThereIn th…

NASA’s 60th Anniversary: What’s Out There

In the past 60 years, we’ve advanced our understanding of our solar system and beyond. We continually ask “What’s out there?” as we advance humankind and send spacecraft to explore.
Since opening for business on Oct. 1, 1958, our history tells a story of exploration, innovation and discoveries. The next 60 years, that story continues. Learn more: https://www.nasa.gov/60

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NASA’s New Planet Hunter Reveals a Sky Full of…

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NASA’s newest planet-hunting satellite — the Transiting
Exoplanet Survey Satellite, or TESS for short
— has just released its first science image using all
of its cameras to capture a huge swath of the sky! TESS is NASA’s next step in the
search for planets outside our solar system, called exoplanets.

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This spectacular image, the first released
using all four of TESS’ cameras, shows the satellite’s full field of view. It
captures parts of a dozen constellations, from Capricornus
(the Sea Goat) to Pictor
(the Painter’s Easel) — though it might be hard to find familiar constellations
among all these stars! The image even includes the Large and Small Magellanic
Clouds, our galaxy’s two largest companion galaxies.

The science community calls this image “first
light,” but don’t let that fool you — TESS has been seeing light since it
launched in April. A first light image like this is released to show off the
first science-quality image taken after a mission starts collecting science
data, highlighting a spacecraft’s capabilities.

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TESS has been busy since it launched from NASA’s Kennedy Space Center in Cape Canaveral, Florida. First TESS needed to get into position, which required a push from the Moon.

After nearly a month in space, the satellite
passed about 5,000 miles from the Moon, whose gravity gave it the boost it needed to get into a special orbit
that will keep it stable and maximize its view of the sky.

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During those first few weeks, we also got a
sneak peek of the sky through one of TESS’s four cameras. This test image
captured over 200,000 stars in just two seconds! The spacecraft was pointed
toward the constellation Centaurus when it snapped this picture. The bright
star Beta
Centauri
is visible at the lower left edge, and the edge
of the Coalsack
Nebula
is in the right upper corner.

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After settling into orbit, scientists ran a
number of checks on TESS, including testing its ability to collect a set of
stable images over a prolonged period of time. TESS not only proved its ability
to perform this task, it also got a surprise! A comet named C/2018 N1 passed through TESS’s cameras
for about 17 hours in July.

The images show a treasure
trove of cosmic curiosities
. There are some stars whose
brightness changes over time and asteroids visible as small moving white dots.
You can even see an arc of stray light from Mars, which is located outside the
image, moving across the screen.

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Now that TESS has settled into orbit and has
been thoroughly tested, it’s digging into its main mission of finding planets around other stars.
How will it spot something as tiny and faint as a planet trillions of miles
away? The trick is to look at the star!

So far, most
of the exoplanets we’ve found
were detected by looking
for tiny dips in the brightness of their host stars. These dips are caused by
the planet passing between us and its star – an event called a transit. Over
its first two years, TESS will stare at 200,000 of the nearest and brightest stars
in the sky to look for transits to identify stars with planets.

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TESS will be building on the legacy of NASA’s Kepler spacecraft, which also used
transits to find exoplanets. TESS’s target stars are about 10 times closer than
Kepler’s, so they’ll tend to be brighter. Because they’re closer and brighter,
TESS’s target stars will be ideal candidates for follow-up studies with current
and future observatories.

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TESS is challenging over 200,000 of our
stellar neighbors to a staring contest! Who knows what new amazing planets
we’ll find?

The
TESS mission is led by MIT
and came together with the help of many
different partners
. You can keep up
with the latest from the TESS mission by following mission updates.

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What Can We Learn from the Universe’s Baby Pic…

If you look at your baby photos, you might see hints of the person you are today — a certain look in the eyes, maybe the hint of your future nose or ears. In the same way, scientists examine the universe’s “baby picture” for clues about how it grew into the cosmos we know now. This baby photo is the cosmic microwave background (CMB), a faint glow that permeates the universe in all directions.

In late September, NASA plans to launch a balloon-based astronomical observatory from Fort Sumner, New Mexico, to study the universe’s baby picture. Meet PIPER! The Primordial Inflation Polarization Explorer will fly at the edge of our atmosphere to look for subtle patterns in the CMB.

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The CMB is cold. Really, really cold. The average temperature is around minus 455 degrees Fahrenheit. It formed 380,000 years after the big bang, which scientists think happened about 13.8 billion years ago. When it was first discovered, the CMB temperature looked very uniform, but researchers later found there are slight variations like hot and cold spots. The CMB is the oldest light in the universe that we can see. Anything before the CMB is foggy — literally.

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Credit: Rob van Hal

Before the CMB, the universe was a fog of hot, dense plasma. (By hot, we’re talking about 500 million degrees F.) That’s so hot that atoms couldn’t exist yet – there was just a soup of electrons and protons. Electrons are great at deflecting light. So, any light that existed in the first few hundred thousand years after the big bang couldn’t travel very far before bouncing off electrons, similar to the way a car’s headlights get diffused in fog.  

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After the big bang, the universe started expanding rapidly in all directions. This expansion is still happening today. As the universe continued to expand, it cooled. By the time the universe reached its 380,000th birthday, it had cooled enough that electrons and protons could combine into hydrogen atoms for the first time. (Scientists call this era recombination.) Hydrogen atoms don’t deflect light nearly as well as loose electrons and the fog lifted. Light could now travel long distances across the universe.

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The light we see in the CMB comes from the recombination era. As it traveled across the universe, through the formation of stars and galaxies, it lost energy. Now we observe it in the microwave part of the electromagnetic spectrum, which is less energetic than visible light and therefore invisible to our eyes. The first baby photo of the CMB – really, a map of the sky in microwaves – came from our Cosmic Background Explorer, which operated from 1989 to 1993.

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Why are we so interested in the universe’s baby picture? Well, it’s helped us learn a lot about the structure of the universe around us today. For example, the Wilkinson Microwave Anisotropy Probe produced a detailed map of the CMB and helped us learn that the universe is 68 percent dark energy, 27 percent dark matter and just 5 percent normal matter — the stuff that you and stars are made of.

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Right after the big bang, we’re pretty sure the universe was tiny. Really tiny. Everything we see today would have been stuffed into something smaller than a proton. If the universe started out that small, then it would have followed the rules of quantum mechanics. Quantum mechanics allows all sorts of strange things to happen. Matter and energy can be “borrowed” from the future then crash back into nothingness. And then cosmic inflation happened and the universe suddenly expanded by a trillion trillion times.

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All this chaos creates a sea of gravitational waves. (These are called “primordial” gravitational waves and come from a different source than the gravitational waves you may have heard about from merging neutron stars and black holes.) The signal of the primordial gravitational waves is a bit like white noise, where the signal from merging dead stars is like a whistle you can pick up over the noise.

These gravitational waves filled the baby universe and created distinct patterns, called B-mode polarization, in the CMB light. These patterns have handedness, which means even though they’re mirror images of each other, they’re not symmetrical — like trying to wear a left-hand glove on your right hand. They’re distinct from another kind of polarization called E-mode, which is symmetrical and echoes the distribution of matter in the universe.

That’s where PIPER comes in. PIPER’s two telescopes sit in a hot-tub-sized container of liquid helium, which runs about minus 452 degrees F. It’ll look at 85 percent of the sky and is extremely sensitive, so it will help us learn even more about the early days of the universe. By telling us more about polarization and those primordial gravitational waves, PIPER will help us understand how the early universe grew from that first baby picture.

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PIPER’s first launch window in Fort Sumner, New Mexico, is in late September. When it’s getting ready to launch, you’ll be able to watch the balloon being filled on the Columbia Scientific Balloon Facility website. Follow NASA Blueshift on Twitter or Facebook for updates about PIPER and when the livestream will be available.

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Black Holes are NICER Than You Think!

We’re learning more every day about black holes thanks to one of the instruments aboard the International Space Station! Our Neutron star Interior Composition Explorer (NICER) instrument is keeping an eye on some of the most mysterious cosmic phenomena.

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We’re going to talk about some of the amazing new things NICER is showing us about black holes. But first, let’s talk about black holes — how do they work, and where do they come from? There are two important types of black holes we’ll talk about here: stellar and supermassive. Stellar mass black holes are three to dozens of times as massive as our Sun while supermassive black holes can be billions of times as massive!

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Stellar black holes begin with a bang — literally! They are one of the possible objects left over after a large star dies in a supernova explosion. Scientists think there are as many as a billion stellar mass black holes in our Milky Way galaxy alone!

Supermassive black holes have remained rather mysterious in comparison. Data suggest that supermassive black holes could be created when multiple black holes merge and make a bigger one. Or that these black holes formed during the early stages of galaxy formation, born when massive clouds of gas collapsed billions of years ago. There is very strong evidence that a supermassive black hole lies at the center of all large galaxies, as in our Milky Way.

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Imagine an object 10 times more massive than the Sun squeezed into a sphere approximately the diameter of New York City — or cramming a billion trillion people into a car! These two examples give a sense of how incredibly compact and dense black holes can be.

Because so much stuff is squished into such a relatively small volume, a black hole’s gravity is strong enough that nothing — not even light — can escape from it. But if light can’t escape a dark fate when it encounters a black hole, how can we “see” black holes?

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Scientists can’t observe black holes directly, because light can’t escape to bring us information about what’s going on inside them. Instead, they detect the presence of black holes indirectly — by looking for their effects on the cosmic objects around them. We see stars orbiting something massive but invisible to our telescopes, or even disappearing entirely!

When a star approaches a black hole’s event horizon — the point of no return — it’s torn apart. A technical term for this is “spaghettification” — we’re not kidding! Cosmic objects that go through the process of spaghettification become vertically stretched and horizontally compressed into thin, long shapes like noodles.

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Scientists can also look for accretion disks when searching for black holes. These disks are relatively flat sheets of gas and dust that surround a cosmic object such as a star or black hole. The material in the disk swirls around and around, until it falls into the black hole. And because of the friction created by the constant movement, the material becomes super hot and emits light, including X-rays.  

At last — light! Different wavelengths of light coming from accretion disks are something we can see with our instruments. This reveals important information about black holes, even though we can’t see them directly.

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So what has NICER helped us learn about black holes? One of the objects this instrument has studied during its time aboard the International Space Station is the ever-so-forgettably-named black hole GRS 1915+105, which lies nearly 36,000 light-years — or 200 million billion miles — away, in the direction of the constellation Aquila.

Scientists have found disk winds — fast streams of gas created by heat or pressure — near this black hole. Disk winds are pretty peculiar, and we still have a lot of questions about them. Where do they come from? And do they change the shape of the accretion disk?

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It’s been difficult to answer these questions, but NICER is more sensitive than previous missions designed to return similar science data. Plus NICER often looks at GRS 1915+105 so it can see changes over time.

NICER’s observations of GRS 1915+105 have provided astronomers a prime example of disk wind patterns, allowing scientists to construct models that can help us better understand how accretion disks and their outflows around black holes work.

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NICER has also collected data on a stellar mass black hole with another long name — MAXI J1535-571 (we can call it J1535 for short) — adding to information provided by NuSTAR, Chandra, and MAXI. Even though these are all X-ray detectors, their observations tell us something slightly different about J1535, complementing each other’s data!

This rapidly spinning black hole is part of a binary system, slurping material off its partner, a star. A thin halo of hot gas above the disk illuminates the accretion disk and causes it to glow in X-ray light, which reveals still more information about the shape, temperature, and even the chemical content of the disk. And it turns out that J1535’s disk may be warped!

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Image courtesy of NRAO/AUI and Artist: John Kagaya (Hoshi No Techou)

This isn’t the first time we have seen evidence for a warped disk, but J1535’s disk can help us learn more about stellar black holes in binary systems, such as how they feed off their companions and how the accretion disks around black holes are structured.

NICER primarily studies neutron stars — it’s in the name! These are lighter-weight relatives of black holes that can be formed when stars explode. But NICER is also changing what we know about many types of X-ray sources. Thanks to NICER’s efforts, we are one step closer to a complete picture of black holes. And hey, that’s pretty nice!

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Why Bennu? 10 Reasons

After traveling for two years and billions of kilometers from Earth, the OSIRIS-REx probe is only a few months away from its destination: the intriguing asteroid Bennu. When it arrives in December, OSIRIS-REx will embark on a nearly two-year investigation of this clump of rock, mapping its terrain and finding a safe and fruitful site from which to collect a sample.

The spacecraft will briefly touch Bennu’s surface around July 2020 to collect at least 60 grams (equal to about 30 sugar packets) of dirt and rocks. It might collect as much as 2,000 grams, which would be the largest sample by far gathered from a space object since the Apollo Moon landings. The spacecraft will then pack the sample into a capsule and travel back to Earth, dropping the capsule into Utah’s west desert in 2023, where scientists will be waiting to collect it.

This years-long quest for knowledge thrusts Bennu into the center of one of the most ambitious space missions ever attempted. But the humble rock is but one of about 780,000 known asteroids in our solar system. So why did scientists pick Bennu for this momentous investigation? Here are 10 reasons:

1. It’s close to Earth

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Unlike most other asteroids that circle the Sun in the asteroid belt between Mars and Jupiter, Bennu’s orbit is close in proximity to Earth’s, even crossing it. The asteroid makes its closest approach to Earth every 6 years. It also circles the Sun nearly in the same plane as Earth, which made it somewhat easier to achieve the high-energy task of launching the spacecraft out of Earth’s plane and into Bennu’s. Still, the launch required considerable power, so OSIRIS-REx used Earth’s gravity to boost itself into Bennu’s orbital plane when it passed our planet in September 2017.

2. It’s the right size

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Asteroids spin on their axes just like Earth does. Small ones, with diameters of 200 meters or less, often spin very fast, up to a few revolutions per minute. This rapid spinning makes it difficult for a spacecraft to match an asteroid’s velocity in order to touch down and collect samples. Even worse, the quick spinning has flung loose rocks and soil, material known as “regolith” — the stuff OSIRIS-REx is looking to collect — off the surfaces of small asteroids. Bennu’s size, in contrast, makes it approachable and rich in regolith. It has a diameter of 492 meters, which is a bit larger than the height of the Empire State Building in New York City, and rotating once every 4.3 hours.

3. It’s really old

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Bennu is a leftover fragment from the tumultuous formation of the solar system. Some of the mineral fragments inside Bennu could be older than the solar system. These microscopic grains of dust could be the same ones that spewed from dying stars and eventually coalesced to make the Sun and its planets nearly 4.6 billion years ago. But pieces of asteroids, called meteorites, have been falling to Earth’s surface since the planet formed. So why don’t scientists just study those old space rocks? Because astronomers can’t tell (with very few exceptions) what kind of objects these meteorites came from, which is important context. Furthermore, these stones, that survive the violent, fiery decent to our planet’s surface, get contaminated when they land in the dirt, sand, or snow. Some even get hammered by the elements, like rain and snow, for hundreds or thousands of years. Such events change the chemistry of meteorites, obscuring their ancient records.

4. It’s well preserved

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Bennu, on the other hand, is a time capsule from the early solar system, having been preserved in the vacuum of space. Although scientists think it broke off a larger asteroid in the asteroid belt in a catastrophic collision between about 1 and 2 billion years ago, and hurtled through space until it got locked into an orbit near Earth’s, they don’t expect that these events significantly altered it.

5. It might contain clues to the origin of life

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Analyzing a sample from Bennu will help planetary scientists better understand the role asteroids may have played in delivering life-forming compounds to Earth. We know from having studied Bennu through Earth- and space-based telescopes that it is a carbonaceous, or carbon-rich, asteroid. Carbon is the hinge upon which organic molecules hang. Bennu is likely rich in organic molecules, which are made of chains of carbon bonded with atoms of oxygen, hydrogen, and other elements in a chemical recipe that makes all known living things. Besides carbon, Bennu also might have another component important to life: water, which is trapped in the minerals that make up the asteroid.

6. It contains valuable materials

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Besides teaching us about our cosmic past, exploring Bennu close-up will help humans plan for the future. Asteroids are rich in natural resources, such as iron and aluminum, and precious metals, such as platinum. For this reason, some companies, and even countries, are building technologies that will one day allow us to extract those materials. More importantly, asteroids like Bennu are key to future, deep-space travel. If humans can learn how to extract the abundant hydrogen and oxygen from the water locked up in an asteroid’s minerals, they could make rocket fuel. Thus, asteroids could one day serve as fuel stations for robotic or human missions to Mars and beyond. Learning how to maneuver around an object like Bennu, and about its chemical and physical properties, will help future prospectors.

7. It will help us better understand other asteroids

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Astronomers have studied Bennu from Earth since it was discovered in 1999. As a result, they think they know a lot about the asteroid’s physical and chemical properties. Their knowledge is based not only on looking at the asteroid, but also studying meteorites found on Earth, and filling in gaps in observable knowledge with predictions derived from theoretical models. Thanks to the detailed information that will be gleaned from OSIRIS-REx, scientists now will be able to check whether their predictions about Bennu are correct. This work will help verify or refine telescopic observations and models that attempt to reveal the nature of other asteroids in our solar system.

8. It will help us better understand a quirky solar force …

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Astronomers have calculated that Bennu’s orbit has drifted about 280 meters (0.18 miles) per year toward the Sun since it was discovered. This could be because of a phenomenon called the Yarkovsky effect, a process whereby sunlight warms one side of a small, dark asteroid and then radiates as heat off the asteroid as it rotates. The heat energy thrusts an asteroid either away from the Sun, if it has a prograde spin like Earth, which means it spins in the same direction as its orbit, or toward the Sun in the case of Bennu, which spins in the opposite direction of its orbit. OSIRIS-REx will measure the Yarkovsky effect from close-up to help scientists predict the movement of Bennu and other asteroids. Already, measurements of how this force impacted Bennu over time have revealed that it likely pushed it to our corner of the solar system from the asteroid belt.

9. … and to keep asteroids at bay

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One reason scientists are eager to predict the directions asteroids are drifting is to know when they’re coming too-close-for-comfort to Earth. By taking the Yarkovsky effect into account, they’ve estimated that Bennu could pass closer to Earth than the Moon is in 2135, and possibly even closer between 2175 and 2195. Although Bennu is unlikely to hit Earth at that time, our descendants can use the data from OSIRIS-REx to determine how best to deflect any threatening asteroids that are found, perhaps even by using the Yarkovsky effect to their advantage.

10. It’s a gift that will keep on giving

Samples of Bennu will return to Earth on September 24, 2023. OSIRIS-REx scientists will study a quarter of the regolith. The rest will be made available to scientists around the globe, and also saved for those not yet born, using techniques not yet invented, to answer questions not yet asked.

Read the web version of this week’s “Solar System: 10 Things to Know” article HERE.

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