When we talk about the enormity of the cosmos, it’s easy to
toss out big numbers – but far harder to wrap our minds around just how large,
how far and how numerous celestial bodies like exoplanets – planets beyond our
solar system – really are.
So. How big is our Milky Way Galaxy?
We use light-time to measure the vast distances of space.
It’s the distance that light travels in a specific period of
time. Also: LIGHT IS FAST, nothing travels faster than light.
How far can light travel in one second? 186,000 miles. It
might look even faster in metric: 300,000 kilometers in one second. See? FAST.
How far can light travel in one minute? 11,160,000 miles.
We’re moving now! Light could go around the Earth a bit more than 448 times in
one minute.
Speaking of Earth, how long does it take light
from the Sun to reach our planet? 8.3 minutes. (It takes 43.2 minutes for
sunlight to reach Jupiter, about 484 million miles away.) Light is fast, but
the distances are VAST.
In an hour, light can travel 671 million miles. We’re still
light-years from the nearest
exoplanet, by the way. Proxima Centauri b is 4.2 light-years away. So… how far
is a light-year? 5.8 TRILLION MILES.
A trip at light speed to the very edge of our solar system –
the farthest reaches of the Oort Cloud, a collection of dormant comets way, WAY
out there – would take about 1.87 years.
Our galaxy contains 100 to 400 billion stars and is about
100,000 light-years across!
One of the most distant exoplanets known to us in the Milky
Way is Kepler-443b. Traveling at light speed, it would take 3,000 years to get
there. Or 28 billion years, going 60 mph. So, you know, far.
The first confirmation of a planet orbiting a star outside our solar system happened in 1995. We now know that these worlds – also known as exoplanets – are abundant. So far, we’ve confirmed more than 4000. Even though these planets are far, far away, we can still study them using ground-based and space-based telescopes.
Our upcoming James Webb Space Telescope will study the atmospheres of the worlds in our solar system and those of exoplanets far beyond. Could any of these places support life? What Webb finds out about the chemical elements in these exoplanet atmospheres might help us learn the answer.
How do we know what’s in the atmosphere of an exoplanet?
Most known exoplanets have been discovered because they partially block the light of their suns. This celestial photo-bombing is called a transit.
During a transit, some of the star’s light travels through the planet’s atmosphere and gets absorbed.
The light that survives carries information about the planet across light-years of space, where it reaches our telescopes.
(However, the planet is VERY small relative to the star, and VERY far away, so it is still very difficult to detect, which is why we need a BIG telescope to be sure to capture this tiny bit of light.)
So how do we use a telescope to read light?
Stars emit light at many wavelengths. Like a prism making a rainbow, we can separate light into its separate wavelengths. This is called a spectrum. Learn more about how telescopes break down light here.
Visible light appears to our eyes as the colors of the rainbow, but beyond visible light there are many wavelengths we cannot see.
Now back to the transiting planet…
As light is traveling through the planet’s atmosphere, some wavelengths get absorbed.
Which wavelengths get absorbed depends on which molecules are in the planet’s atmosphere. For example, carbon monoxide molecules will capture different wavelengths than water vapor molecules.
So, when we look at that planet in front of the star, some of the wavelengths of the starlight will be missing, depending on which molecules are in the atmosphere of the planet.
Learning about the atmospheres of other worlds is how we identify those that could potentially support life…
…bringing us another step closer to answering one of humanity’s oldest questions: Are we alone?
Watch the full video where this method of hunting for distant planets is explained:
To learn more about NASA’s James Webb Space Telescope, visit the website, or follow the mission on Facebook, Twitter and Instagram.
Text and graphics credit Space Telescope Science Institute
Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com.
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.
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.
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.
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.
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.
TESS is challenging over 200,000 of our
stellar neighbors to a staring contest! Who knows what new amazing planets
we’ll find?
One of the greatest mysteries that life on Earth holds is, “Are we alone?”
At NASA, we are working hard to answer this question. We’re scouring the universe, hunting down planets that could potentially support life. Thanks to ground-based and space-based telescopes, including Kepler and TESS, we’ve found more than 4,000 planets outside our solar system, which are called exoplanets. Our search for new planets is ongoing — but we’re also trying to identify which of the 4,000 already discovered could be habitable.
Unfortunately, we can’t see any of these planets up close. The closest exoplanet to our solar system orbits the closest star to Earth, Proxima Centauri, which is just over 4 light years away. With today’s technology, it would take a spacecraft 75,000 years to reach this planet, known as Proxima Centauri b.
How do we investigate a planet that we can’t see in detail and can’t get to? How do we figure out if it could support life?
This is where computer models come into play. First we take the information that we DO know about a far-off planet: its size, mass and distance from its star. Scientists can infer these things by watching the light from a star dip as a planet crosses in front of it, or by measuring the gravitational tugging on a star as a planet circles it.
We put these scant physical details into equations that comprise up to a million lines of computer code. The code instructs our Discover supercomputer to use our rules of nature to simulate global climate systems. Discover is made of thousands of computers packed in racks the size of vending machines that hum in a deafening chorus of data crunching. Day and night, they spit out 7 quadrillion calculations per second — and from those calculations, we paint a picture of an alien world.
While modeling work can’t tell us if any exoplanet is habitable or not, it can tell us whether a planet is in the range of candidates to follow up with more intensive observations.
One major goal of simulating climates is to identify the most promising planets to turn to with future technology, like the James Webb Space Telescope, so that scientists can use limited and expensive telescope time most efficiently.
Additionally, these simulations are helping scientists create a catalog of potential chemical signatures that they might detect in the atmospheres of distant worlds. Having such a database to draw from will help them quickly determine the type of planet they’re looking at and decide whether to keep observing or turn their telescopes elsewhere.
A simulated image of NASA’s Nancy Grace Roman Space Telescope’s future observations toward the center of our galaxy, spanning less than 1 percent of the total area of Roman’s Galactic Bulge Time-Domain Survey. The simulated stars were drawn from the Besançon Galactic Model.
Exploring the Changing Universe with the Roman Space Telescope
The view from your backyard might paint the universe as an unchanging realm, where only twinkling stars and nearby objects, like satellites and meteors, stray from the apparent constancy. But stargazing through NASA’s upcoming Nancy Grace Roman Space Telescope will offer a front row seat to a dazzling display of cosmic fireworks sparkling across the sky.
We hope you like your planetary systems extra spicy. 🔥
A new system of seven sizzling planets has been discovered using data from our retired Kepler space telescope.
Named Kepler-385, it’s part of a new catalog of planet candidates and multi-planet systems discovered using Kepler.
The discovery helps illustrate that multi-planetary systems have more circular orbits around the host star than systems with only one or two planets.
Our Kepler mission is responsible for the discovery of the most known exoplanets to date. The space telescope’s observations ended in 2018, but its data continues to paint a more detailed picture of our galaxy today.
Here are a few more things to know about Kepler-385:
How will the James Webb Space Telescope change how we see the universe? Ask an expert!
The James Webb Space Telescope is launching on December 22, 2021. Webb’s revolutionary technology will explore every phase of cosmic history—from within our solar system to the most distant observable galaxies in the early universe, to everything in between. Postdoctoral Research Associate Naomi Rowe-Gurney will be taking your questions about Webb and Webb science in an Answer Time session on Tuesday, December 14 from noon to 1 p.m EST here on our Tumblr!
Dr. Naomi Rowe-Gurney recently completed her PhD at the University of Leicester and is now working at NASA Goddard Space Flight Center as a postdoc through Howard University. As a planetary scientist for the James Webb Space Telescope, she’s an expert on the atmospheres of the ice giants in our solar system — Uranus and Neptune — and how the Webb telescope will be able to learn more about them.
The James Webb Space Telescope – fun facts:
Webb is so big it has to fold origami-style to fit into its rocket and will unfold like a “Transformer” in space.
Webb is about 100 times more powerful than the Hubble Space Telescope and designed to see the infrared, a region Hubble can only peek at.
With unprecedented sensitivity, it will peer back in time over 13.5 billion years to see the first galaxies born after the Big Bang––a part of space we’ve never seen.
It will study galaxies near and far, young and old, to understand how they evolve.
Webb will explore distant worlds and study the atmospheres of planets orbiting other stars, known as exoplanets, searching for chemical fingerprints of possible habitability.
Space telescopes like Hubble and our upcoming James Webb Space Telescope use light not only to create images, but can also break light down into individual colors (or wavelengths). Studying light this way can give us a lot of detail about the object that emitted that light. For example, studying the components of the light from exoplanets can tell us about its atmosphere’s color, chemical makeup, and temperature. How does this work?
Remember the primary colors you learned about in elementary school?
Those colors are known as the pigment or subtractive colors. Every other color is some combination of the primary colors: red, yellow, and blue.
Light also has its own primary colors, and they work in a similar way. These colors are known as additive or light colors.
TVs make use of light’s colors to create the pictures we see. Each pixel of a TV screen contains some amount of red, green and blue light. The amount of each light determines the overall color of the pixel. So, each color on the TV comes from a combination of the primary colors of light: red, green and blue.
Space telescope images of celestial objects are also a combination of the colors of light.
Every pixel that is collected can be broken down into its base colors. To learn even more, astronomers break the red, green and blue light down into even smaller sections called wavelengths.
This breakdown is called a spectrum.
With the right technology, every pixel of light can also be measured as a spectrum.
Images show us the big picture, while a spectrum reveals finer details. Astronomers use spectra to learn things like what molecules are in planet atmospheres and distant galaxies.
An Integral Field Unit, or IFU, is a special tool on the James Webb Space Telescope that captures images and spectra at the same time.
The IFU creates a unique spectrum for each pixel of the image the telescope is capturing, providing scientists with an enormous amount of valuable, detailed data. So, with an IFU we can get an image, many spectra and a better understanding of our universe.
Watch the full video where this method of learning about planetary atmospheres is explained:
The James Webb Space Telescope is our upcoming infrared space observatory, which will launch in 2021. It will spy the first galaxies that formed in the universe and shed light on how galaxies evolve, how stars and planetary systems are born and tell us about potentially habitable planets around other stars.
To learn more about NASA’s James Webb Space Telescope, visit the website, or follow the mission on Facebook, Twitter and Instagram.
Text and graphics credit: Space Telescope Science Institute
Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com.
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.
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.
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.
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.
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.
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.
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.
But before we get to dark energy, let’s first talk a bit about the expanding cosmos. It started with the big bang — when the universe started expanding from a hot, dense state about 13.8 billion years ago. Our universe has been getting bigger and bigger ever since. Nearly every galaxy we look at is zipping away from us, caught up in that expansion!
The expansion, though, is even weirder than you might imagine. Things aren’t actually moving away from each other. Instead, the space between them is getting larger.
Imagine that you and a friend were standing next to each other. Just standing there, but the floor between you was growing. You two aren’t technically moving, but you see each other moving away. That’s what’s happening with the galaxies (and everything else) in our cosmos … in ALL directions!
Astronomers expected the expansion to slow down over time. Why? In a word: gravity. Anything that has mass or energy has gravity, and gravity tries to pull stuff together. Plus, it works over the longest distances. Even you, reading this, exert a gravitational tug on the farthest galaxy in the universe! It’s a tiny tug, but a tug nonetheless.
As the space between galaxies grows, gravity is trying to tug the galaxies back together — which should slow down the expansion. So, if we measure the distance of faraway galaxies over time, we should be able to detect if the universe’s growth rate slows down.
⬆️ This graphic illustrates the history of our expanding universe. We do see some slowing down of the expansion (the uphill part of the graph, where the roller coaster is slowing down). However, at some point, dark energy overtakes gravity and the expansion speeds up (the downhill on the graph). It’s like our universe is on a giant roller coaster ride, but we’re not sure how steep the hill is!
We don’t know exactly what dark energy is, and we’ve never detected it directly. But we do know there is a lot of it. A lot. If you summed up all the “stuff” in the universe — normal matter (the stuff we can touch or observe directly), dark matter, and dark energy — dark energy would make up more than two-thirds of what is out there.
That’s a lot of our universe to have escaped detection!
Researchers have come up with a few dark energy possibilities. Einstein discarded an idea from his theory of general relativity about an intrinsic property of space itself. It could be that this bit of theory got dark energy right after all. Perhaps instead there is some strange kind of energy-fluid that fills space. It could even be that we need to tweak Einstein’s theory of gravity to work at the largest scales.
Our Wide Field Infrared Survey Telescope (WFIRST) — planned to launch in the mid-2020s — will be helping with the task of unraveling the mystery of dark energy. WFIRST will map the structure and distribution of matter throughout the cosmos and across cosmic time. It will also map the universe’s expansion and study galaxies from when the universe was a wee 2-billion-year-old up to today. Using these new data, researchers will learn more than we’ve ever known about dark energy. Perhaps even cracking open the case!
You can find out more about the history of dark energy and how a number of different pieces of observational evidence led to its discovery in our Cosmic Times series. And keep an eye on WFIRST to see how this mystery unfolds.
LaRue Burbank, mathematician and computer, is just one of the many women who were instrumental to NASA missions.
4 Little Known Women Who Made Huge Contributions to NASA
Women have always played a significant role at NASA and its predecessor NACA, although for much of the agency’s history, they received neither the praise nor recognition that their contributions deserved. To celebrate Women’s History Month – and properly highlight some of the little-known women-led accomplishments of NASA’s early history – our archivists gathered the stories of four women whose work was critical to NASA’s success and paved the way for future generations.