Earth’s Hot And It’s Cold 🎶(and We Can Tell From Space)

Protecting our Home Planet 🌎

Did you ever wonder how we spots asteroids that may be getting too close to Earth for comfort? Wonder no more. Our Planetary Defense Coordination Office does just that. Thanks to a variety of ground and space based telescopes, we’re able to detect potentially hazardous objects so we can prepare for the unlikely threat against our planet. 

What is a near-Earth object?

Near-Earth objects (NEOs) are asteroids and comets that orbit the Sun, but their orbits bring them into Earth’s neighborhood – within 30 million miles of Earth’s orbit.

These objects are relatively unchanged remnant debris from the solar system’s formation some 4.6 billion years ago. Most of the rocky asteroids originally formed in the warmer inner solar system between the orbits of Mars and Jupiter, while comets, composed mostly of water ice with embedded dust particles, formed in the cold outer solar system.

Who searches for near-Earth objects?

Our Near-Earth Object (NEO) Observations Program finds, tracks and monitors near-Earth asteroids and comets. Astronomers supported by the program use telescopes to follow up the discoveries to make additional measurements, as do many observatories all over the world. The Center for Near-Earth Object Studies, based at our Jet Propulsion Laboratory, also uses these data to calculate high-precision orbits for all known near-Earth objects and predict future close approaches by them to Earth, as well as the potential for any future impacts.

How do we calculate the orbit of a near-Earth object?

Scientists determine the orbit of an asteroid by comparing measurements of its position as it moves across the sky to the predictions of a computer model of its orbit around the Sun. The more observations that are used and the longer the period over which those observations are made, the more accurate the calculated orbit and the predictions that can be made from it.

How many near-Earth objects have been discovered so far?

At the start of 2019, the number of discovered NEOs totaled more than 19,000, and it has since surpassed 20,000. An average of 30 new discoveries are added each week. More than 95 percent of these objects were discovered by NASA-funded surveys since 1998, when we initially established its NEO Observations Program and began tracking and cataloguing them.

Currently the risk of an asteroid striking Earth is exceedingly low, but we are constantly monitoring our cosmic neighborhood. Have more questions? Visit our Planetary Defense page to explore how we keep track of near-Earth objects. 

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Why Do X-Ray Mirrors Look So Unusual?

Does the object in this image look like a mirror? Maybe not, but that’s exactly what it is! To be more precise, it’s a set of mirrors that will be used on an X-ray telescope. But why does it look nothing like the mirrors you’re familiar with? To answer that, let’s first take a step back. Let’s talk telescopes.

How does a telescope work?

The basic function of a telescope is to gather and focus light to amplify the light’s source. Astronomers have used telescopes for centuries, and there are a few different designs. Today, most telescopes use curved mirrors that magnify and focus light from distant objects onto your eye, a camera, or some other instrument. The mirrors can be made from a variety of materials, including glass or metal.

Space telescopes like the James Webb and Hubble Space Telescopes use large mirrors to focus light from some of the most distant objects in the sky. However, the mirrors must be tailored for the type and range of light the telescope is going to capture—and X-rays are especially hard to catch.

X-rays versus mirrors

X-rays tend to zip through most things. This is because X-rays have much smaller wavelengths than most other types of light. In fact, X-rays can be smaller than a single atom of almost every element. When an X-ray encounters some surfaces, it can pass right between the atoms!

Doctors use this property of X-rays to take pictures of what’s inside you. They use a beam of X-rays that mostly passes through skin and muscle but is largely blocked by denser materials, like bone. The shadow of what was blocked shows up on the film.

This tendency to pass through things includes most mirrors. If you shoot a beam of X-rays into a standard telescope, most of the light would go right through or be absorbed. The X-rays wouldn’t be focused by the mirror, and we wouldn’t be able to study them.

X-rays can bounce off a specially designed mirror, one turned on its side so that the incoming X-rays arrive almost parallel to the surface and glance off it. At this shallow angle, the space between atoms in the mirror's surface shrinks so much that X-rays can't sneak through. The light bounces off the mirror like a stone skipping on water. This type of mirror is called a grazing incidence mirror.

A metallic onion

Telescope mirrors curve so that all of the incoming light comes to the same place. Mirrors for most telescopes are based on the same 3D shape — a paraboloid. You might remember the parabola from your math classes as the cup-shaped curve. A paraboloid is a 3D version of that, spinning it around the axis, a little like the nose cone of a rocket. This turns out to be a great shape for focusing light at a point.

Mirrors for visible and infrared light and dishes for radio light use the “cup” portion of that paraboloid. For X-ray astronomy, we cut it a little differently to use the wall. Same shape, different piece. The mirrors for visible, infrared, ultraviolet, and radio telescopes look like a gently-curving cup. The X-ray mirror looks like a cylinder with very slightly angled walls.

The image below shows how different the mirrors look. On the left is one of the Chandra X-ray Observatory’s cylindrical mirrors. On the right you can see the gently curved round primary mirror for the Stratospheric Observatory for Infrared Astronomy telescope.

If we use just one grazing incidence mirror in an X-ray telescope, there would be a big hole, as shown above (left). We’d miss a lot of X-rays! Instead, our mirror makers fill in that cylinder with layers and layers of mirrors, like an onion. Then we can collect more of the X-rays that enter the telescope, giving us more light to study.

Nested mirrors like this have been used in many X-ray telescopes. Above is a close-up of the mirrors for an upcoming observatory called the X-ray Imaging and Spectroscopy Mission (XRISM, pronounced “crism”), which is a Japan Aerospace Exploration Agency (JAXA)-led international collaboration between JAXA, NASA, and the European Space Agency (ESA).

The XRISM mirror assembly uses thin, gold-coated mirrors to make them super reflective to X-rays. Each of the two assemblies has 1,624 of these layers packed in them. And each layer is so smooth that the roughest spots rise no more than one millionth of a millimeter.

Why go to all this trouble to collect this elusive light? X-rays are a great way to study the hottest and most energetic areas of the universe! For example, at the centers of certain galaxies, there are black holes that heat up gas, producing all kinds of light. The X-rays can show us light emitted by material just before it falls in.

Stay tuned to NASA Universe on Twitter and Facebook to keep up with the latest on XRISM and other X-ray observatories.

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Today we celebrate the mission that piqued our curiosities, and drove NASA’s perseverance to pursue further exploration of the Red Planet. The Sojourner rover landed on July 4, 1997, after hitching a ride aboard the Mars Pathfinder mission. Its innovative design became the template for future missions. The rover, named after civil rights pioneer Sojourner Truth, outlived its design life 12 times. This panoramic view of Pathfinder's Ares Vallis landing site shows Sojourner rover is the distance. Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com 

How Well Do You Know Venus?

Similar in structure and size to Earth, Venus’ thick, toxic atmosphere traps heat in a runaway greenhouse effect. A permanent layer of clouds traps heat, creating surface temperatures hot enough to melt lead.

How did Venus get its name? It is named for the ancient Roman goddess of love and beauty. It is believed that Venus was named for the most beautiful of the ancient gods because it shone the brightest of the five planets known to ancient astronomers.

Here are a few fun facts that you might not know:

One day on Venus lasts as long as 243 Earth days (aka the time it takes for Venus to rotate or spin once)

Venus is a rocky planet, also known as a terrestrial planet

Venus’ thick and toxic atmosphere is made up mostly of carbon dioxide and nitrogen, with clouds of sulfuric acid droplets

Venus has no moons or rings

More than 40 spacecraft have explored the planet

No evidence of life has been found on Venus. The planet’s extreme high temperatures of almost 480 degrees Celsius (900 degrees Fahrenheit) makes it seem an unlikely place for life as we know it

Venus spins backwards when compared to the other planets. This means that the sun rises in the west and sets in the east

Night Light

Did you know that Venus is the brightest planet in Earth’s dark skies? Only the moon — which is not a planet — is brighter. Venus outshines the other planets because it is closer and its thick cloud cover is excellent at reflecting sunlight.

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The James Webb Space Telescope has just completed a successful first year of science. Let’s celebrate by seeing the birth of Sun-like stars in this brand-new image from the Webb telescope!

This is a small star-forming region in the Rho Ophiuchi cloud complex. At 390 light-years away, it's the closest star-forming region to Earth. There are around 50 young stars here, all of them similar in mass to the Sun, or smaller. The darkest areas are the densest, where thick dust cocoons still-forming protostars. Huge red bipolar jets of molecular hydrogen dominate the image, appearing horizontally across the upper third and vertically on the right. These occur when a star first bursts through its natal envelope of cosmic dust, shooting out a pair of opposing jets into space like a newborn first stretching her arms out into the world. In contrast, the star S1 has carved out a glowing cave of dust in the lower half of the image. It is the only star in the image that is significantly more massive than the Sun.

Thanks to Webb’s sensitive instruments, we get to witness moments like this at the beginning of a star’s life. One year in, Webb’s science mission is only just getting started. The second year of observations has already been selected, with plans to build on an exciting first year that exceeded expectations. Here’s to many more years of scientific discovery with Webb.

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Credits: NASA, ESA, CSA, STScI, Klaus Pontoppidan (STScI)

Celebrating 10 Years of Revolutionary Solar Views

Twin spacecraft give humanity unprecedented views of the entire sun at one time, traveling to the far side of our home star over the course of a 10-year mission.

These two spacecraft are called STEREO, short for Solar and Terrestrial Relations Observatory. Launched on Oct. 25, 2006, and originally slated for a two-year mission, both spacecraft sent back data for nearly eight years, and STEREO-A still sends information and images from its point of view on the far side of the sun.

STEREO watches the sun from two completely new perspectives. It also provides information invaluable for understanding the sun and its impact on Earth, other worlds, and space itself – collectively known as space weather. On Earth, space weather can trigger things like the aurora and, in extreme cases, put a strain on power systems or damage high-flying satellites.

Because the rest of our sun-watching satellites orbit near our home planet, STEREO’s twin perspectives far from Earth give us a unique opportunity to look at solar events from all sides and understand them in three dimensions.

We use data from STEREO and other missions to understand the space environment throughout the solar system. This helps operators for missions in deep space prepare for the sudden bursts of particles and magnetic field that could pose a danger to their spacecraft. 

STEREO has also helped us understand other objects in our solar system – like comets. Watching how a comet’s tail moves gives us clues about the constant stream of particles that flows out from the sun, called the solar wind.

STEREO is an essential piece of our heliophysics fleet, which includes 17 other missions. Together, these spacecraft shed new light on the sun and its interaction with space, Earth, and other worlds throughout the solar system. 

To celebrate, we’re hosting a Facebook Live event on Wednesday, Oct. 26. Join us at noon ET on the NASA Sun Science Facebook page to learn more about STEREO and ask questions. 

Learn more about how NASA studies the sun at: www.nasa.gov/stereo

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What do *you* think is inside a black hole? Or If they sun was a black hole what would we see in the sky? Thanks!

For more information, visit: https://www.missionjuno.swri.edu/junocam/processing?id=182

Purple haze, all around. See Jupiter in a whole new light in this citizen scientist-created JunoCam image.

1,000 Days in Orbit: MAVEN’s Top 10 Discoveries at Mars

On June 17, our MAVEN (Mars Atmosphere and Volatile Evolution Mission) will celebrate 1,000 Earth days in orbit around the Red Planet.

Since its launch in November 2013 and its orbit insertion in September 2014, MAVEN has been exploring the upper atmosphere of Mars. MAVEN is bringing insight to how the sun stripped Mars of most of its atmosphere, turning a planet once possibly habitable to microbial life into a barren desert world.

Here’s a countdown of the top 10 discoveries from the mission so far:

10. Unprecedented Ultraviolet View of Mars

Revealing dynamic, previously invisible behavior, MAVEN was able to show the ultraviolet glow from the Martian atmosphere in unprecedented detail. Nightside images showed ultraviolet “nightglow” emission from nitric oxide. Nightglow is a common planetary phenomenon in which the sky faintly glows even in the complete absence of eternal light.

9. Key Features on the Loss of Atmosphere

Some particles from the solar wind are able to penetrate unexpectedly deep into the upper atmosphere, rather than being diverted around the planet by the Martian ionosphere. This penetration is allowed by chemical reactions in the ionosphere that turn the charged particles of the solar wind into neutral atoms that are then able to penetrate deeply.

8. Metal Ions

MAVEN made the first direct observations of a layer of metal ions in the Martian ionosphere, resulting from incoming interplanetary dust hitting the atmosphere. This layer is always present, but was enhanced dramatically by the close passage to Mars of Comet Siding Spring in October 2014.

7. Two New Types of Aurora

MAVEN has identified two new types of aurora, termed “diffuse” and “proton” aurora. Unlike how we think of most aurorae on Earth, these aurorae are unrelated to either a global or local magnetic field.

6. Cause of the Aurorae

These aurorae are caused by an influx of particles from the sun ejected by different types of solar storms. When particles from these storms hit the Martian atmosphere, they can also increase the rate of loss of gas to space, by a factor of ten or more.

5. Complex Interactions with Solar Wind

The interactions between the solar wind and the planet are unexpectedly complex. This results due to the lack of an intrinsic Martian magnetic field and the occurrence of small regions of magnetized crust that can affect the incoming solar wind on local and regional scales. The magnetosphere that results from the interactions varies on short timescales and is remarkably “lumpy” as a result.

4. Seasonal Hydrogen

After investigating the upper atmosphere of the Red Planet for a full Martian year, MAVEN determined that the escaping water does not always go gently into space. The spacecraft observed the full seasonal variation of hydrogen in the upper atmosphere, confirming that it varies by a factor of 10 throughout the year. The escape rate peaked when Mars was at its closest point to the sun and dropped off when the planet was farthest from the sun.

3. Gas Lost to Space

MAVEN has used measurements of the isotopes in the upper atmosphere (atoms of the same composition but having different mass) to determine how much gas has been lost through time. These measurements suggest that 2/3 or more of the gas has been lost to space.

2. Speed of Solar Wind Stripping Martian Atmosphere

MAVEN has measured the rate at which the sun and the solar wind are stripping gas from the top of the atmosphere to space today, along with details of the removal process. Extrapolation of the loss rates into the ancient past – when the solar ultraviolet light and the solar wind were more intense – indicates that large amounts of gas have been lost to space through time.

1. Martian Atmosphere Lost to Space

The Mars atmosphere has been stripped away by the sun and the solar wind over time, changing the climate from a warmer and wetter environment early in history to the cold, dry climate that we see today.

Maven will continue its observations and is now observing a second Martian year, looking at the ways that the seasonal cycles and the solar cycle affect the system.

For more information about MAVEN, visit: www.nasa.gov/maven

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Stop. Drop. And Apply to #BeAnAstronaut!

Feel like your place is in the stars? Are you an adventure seeker, an explorer, a person passionate about science and space? We need you!!

Applications are OPEN for our newest class of #Artemis astronauts. Once chosen, you could be the next person to step foot on the Moon and eventually embark on missions to Mars!

Do you have a friend who should apply? Tag them. Do you know someone who's still in school? Encourage them to follow their dreams and aim high.

To give you a sneak peak of what life will be like if you decide to #BeAnAstronaut, we’re taking you behind-the-scenes of astronaut life over the course of March. 

APPLY NOW AND GET MORE INFORMATION HERE! 

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