An Open Book

This summer, our Parker Solar Probe will launch to travel closer to the Sun than any mission before it, right into the Sun’s outer atmosphere, the corona.

The environment in the corona is unimaginably hot: The spacecraft will travel through material with temperatures greater than 3 million degrees Fahrenheit. 

So…why won’t it melt? 

The Difference Between Heat and Temperature

Parker Solar Probe was designed from the ground up to keep its instruments safe and cool, but the nature of the corona itself also helps. The key lies in the difference between heat and temperature.

Temperature measures how fast particles are moving, while heat is the total amount of energy that they transfer. The corona is an incredibly thin and tenuous part of the Sun, and there are very few particles there to transfer energy – so while the particles are moving fast (high temperature), they don’t actually transfer much energy to the spacecraft (low heat).

It’s like the difference between putting your hand in a hot oven versus putting it in a pot of boiling water (don’t try this at home!). In the air of the oven, your hand doesn’t get nearly as hot as it would in the much denser water of the boiling pot. 

So even though Parker Solar Probe travels through a region with temperatures of several million degrees, the surface of its heat shield will reach only about 2,500 F.

The Heat Shield

Of course, thousands of degrees Fahrenheit is still way too hot for scientific instruments. (For comparison, lava from volcano eruptions can be anywhere between 1,300 to 2,200 F.) 

To withstand that heat, Parker Solar Probe is outfitted with a cutting-edge heat shield, called the Thermal Protection System. This heat shield is made of a carbon composite foam sandwiched between two carbon plates. The Sun-facing side is covered with a specially-developed white ceramic coating, applied as a plasma spray, to reflect as much heat as possible.

The heat shield is so good at its job that even though the Sun-facing side of the shield will be at 2,500 F, the instruments in its shadow will remain at a balmy 85 F.

Parker Solar Probe Keeps its Cool

Several other designs on the spacecraft help Parker Solar Probe beat the heat. 

Parker Solar Probe is not only studying the Sun – it’s also powered by it. But even though most of the surface area of its solar arrays can be retracted behind the heat shield, even that small exposed segment would quickly make them overheat while at the Sun.  

To keep things cool, Parker Solar Probe circulates a single gallon of water through its solar arrays. The water absorbs heat as it passes behind the arrays, then radiates that heat out into space as it flows into the spacecraft’s radiator. 

It’s also important for Parker Solar Probe to be able to think on its feet, since it takes about eight minutes for information to travel between Earth and the Sun. If we had to control the spacecraft from Earth, by the time we knew something went wrong, it would be too late to fix it. 

So Parker Solar Probe is smart: Along the edges of the heat shield’s shadow are seven sensors. If any of these sensors detect sunlight, they alert the central computer and the spacecraft can correct its position to keep the sensors – and the rest of the instruments – safely protected behind the heat shield.

Over the course of its seven-year mission, Parker Solar Probe will make 24 orbits of our star. On each close approach to the Sun, it will sample the solar wind, study the Sun’s corona, and provide unprecedentedly close up observations from around our star – and armed with its slew of innovative technologies, we know it will keep its cool the whole time. 

Parker Solar Probe launches summer 2018 on its mission to study the Sun. Keep up with the latest on the mission at nasa.gov/solarprobe or follow us on Twitter and Facebook.

Why Cosmology’s Expanding Universe Controversy Is An Even Bigger Problem Than You Realize

“The question of how quickly the Universe is expanding is one that has troubled astronomers and astrophysicists since we first realized that cosmic expansion was a necessity. While it’s incredibly impressive that two completely independent methods yield answers that are close to within less than 10%, the fact that they don’t agree with each other is troubling.

If the distance ladder group is in error, and the expansion rate is truly on the low end and near 67 km/s/Mpc, the Universe could fall into line. But if the cosmic microwave background group is mistaken, and the expansion rate is closer to 73 km/s/Mpc, we just may have a crisis in modern cosmology.

The Universe cannot have the dark matter density and initial fluctuations that such a value would imply. Until this puzzle is resolved, we must be open to the possibility that a cosmic revolution may be on the horizon.”

Ever since we first learned that the Universe was expanding, scientists have worked hard to measure just how fast that expansion rate is. From that, combined with what makes up the Universe, we can learn how old the Universe is and what it was like in the past, as well as what it’s fate will be in the future. Yet the two groups that make independent measurements of that rate, from the cosmic microwave background and the cosmic distance ladder, have gotten inconsistent results. If the distance ladder team has made a mistake, everything will be fine with cosmology. But if that team is right and the microwave background team is wrong, there should be a crisis coming.

Images taken by the International Space Station

2018 February 4

Venus and the Triply Ultraviolet Sun Image Credit: NASA/SDO & the AIA, EVE, and HMI teams; Digital Composition: Peter L. Dove

Explanation: An unusual type of solar eclipse occurred in 2012. Usually it is the Earth’s Moon that eclipses the Sun. That year, most unusually, the planet Venus took a turn. Like a solar eclipse by the Moon, the phase of Venus became a continually thinner crescent as Venus became increasingly better aligned with the Sun. Eventually the alignment became perfect and the phase of Venus dropped to zero. The dark spot of Venus crossed our parent star. The situation could technically be labeled a Venusian annular eclipse with an extraordinarily large ring of fire. Pictured here during the occultation, the Sun was imaged in three colors of ultraviolet light by the Earth-orbiting Solar Dynamics Observatory, with the dark region toward the right corresponding to a coronal hole. Hours later, as Venus continued in its orbit, a slight crescent phase appeared again. The next Venusian transit across the Sun will occur in 2117.

How The James Webb Space Telescope Will Deploy (In An Ideal World)

“Once the launch vehicle reaches a distance of 10,000 kilometers from Earth, just a half hour into its journey, the telescope separates from the upper stage of the rocket. At this point, JWST is free from the launch vehicle, and is now on its own, on its way to its ultimate destination. Two minutes later, the first key, but difficult step must succeed: to deploy its solar array. James Webb has a battery on board, but will only need it until the array is deployed. The thrusters will then fire, pointing the solar panels towards the Sun and orienting the observatory properly for the next step. If the array fails, the battery will last only a few hours. This step, like a great many, is a single-point-of-failure for the entire mission.”

The James Webb Space Telescope is optimized for uncovering so many secrets of the Universe, it’s impossible to list them all in a single article. From the first stars and galaxies to atmospheres around Earth-sized worlds, from the molecules present in newly-forming planets to direct images of Jupiter-sized worlds in distant solar systems, and from the pristine material left over from the Big Bang to finding the majority of water in the Universe, James Webb will answer questions that no observatory has ever addressed before. But only if it successfully launches and deploys! This takes a tremendous amount of work from vastly separate teams, all coming together without a single failure. Yet the plans have been vetted and tested as thoroughly as possible from the ground, and once the final preparatory steps are taken later this year, all that remains will be to execute the plan.

We just finished the second hottest year on Earth since global temperature estimates first became feasible in 1880. Although 2016 still holds the record for the warmest year, 2017 came in a close second, with average temperatures 1.6 degrees Fahrenheit higher than the mean.

2017’s temperature record is especially noteworthy, because we didn’t have an El Niño this year. Often, the two go hand-in-hand.

El Niño is a climate phenomenon that causes warming of the tropical Pacific Ocean waters, which affect wind and weather patterns around the world, usually resulting in warmer temperatures globally. 2017 was the warmest year on record without an El Niño.

We collect the temperature data from 6,300 weather stations and ship- and buoy-based observations around the world, and then analyze it on a monthly and yearly basis. Researchers at the National Oceanic and Atmospheric Administration (NOAA) do a similar analysis; we’ve been working together on temperature analyses for more than 30 years. Their analysis of this year’s temperature data tracks closely with ours.

The 2017 temperature record is an average from around the globe, so different places on Earth experienced different amounts of warming. NOAA found that the United States, for instance, had its third hottest year on record, and many places still experienced cold winter weather.

Other parts of the world experienced abnormally high temperatures throughout the year. Earth’s Arctic regions are warming at roughly twice the rate of the rest of the planet, which brings consequences like melting polar ice and rising sea levels.

Increasing global temperatures are the result of human activity, specifically the release of greenhouse gases like carbon dioxide and methane. The gases trap heat inside the atmosphere, raising temperatures around the globe.  

We combine data from our fleet of spacecraft with measurements taken on the ground and in the air to continue to understand how our climate is changing. We share this important data with partners and institutions across the U.S. and around the world to prepare and protect our home planet.

Earth’s long-term warming trend can be seen in this visualization of NASA’s global temperature record, which shows how the planet’s temperatures are changing over time, compared to a baseline average from 1951 to 1980.

Learn more about the 2017 Global Temperature Report HERE. 

Discover the ways that we are constantly monitoring our home planet HERE. 

This image of Jupiter was taken by Juno on December 16 and then processed by citizen scientist David Marriott.

Ask Ethan: Why don’t comets orbit the same way planets do?

“Why [do] comets orbit the Sun in a parabolic path, unlike planets which orbit in an elliptical one? Where do comets get the energy to travel such a long distance, from the Oort cloud to the Sun & back? Also, how could interstellar comets/asteroids come out of their parent star [system] and visit other ones?”

When we see comets in our Solar System, they can be either periodic, passing near the Sun and then extending very far away, to return many years later, or they could be a one-shot deal. But comets are driven by the same gravitational laws that drive the planets, which simply make fast-moving, nearly-circular ellipses around the Sun. So what makes these orbits so different, particularly if they’re obeying the same laws? Believe it or not, most of the would-be comets out there are moving in exactly the same nearly-circular paths, only they’re far more tenuously held by the Sun. Gravitational interactions might make small changes in their orbits, but if you’re already moving very slowly, a small change can have a very big effect!

Earth images taken from the International Space Station

“Nikola Tesla For The First Time Describes His New System For Supplying Wireless Power To Run All The Earth’s Industries.”

By a series of discoveries and inventions just perfected, Nikola Tesla, the electrical scientist, has upset what has hitherto been regarded as one of the fixed laws of nature. “Every effect diminishes with distance,” is the way the textbooks have expressed it. Tesla now says that instead of decreasing like other forces, electricity may be made to increase in intensity with the distance traveled.

The full significance of this discovery may not be at once apparent. It is obvious, however, that it annihilates space. There can be no limit to the power of the electric wave which increases in intensity the further it travels.

For nearly 20 years Tesla has been working on his plan, he calls it his wireless “World System.” If it is put into successful execution it will convert the earth into a gigantic conduit, which will pass power for all earthly activities, and make possible communication with other planets.

From time to time Tesla has made partial announcements as his work progressed. This, however, is the first comprehensive account of his system as a whole that the inventor has consented to give to the world.

“Through ages past man has anyways attempted to project in some way or other energy into space. In all his attempts, no matter what agent he employed, he was hampered by the inexorable law of nature which says every effect diminishes with distance, generally as the square of the same, sometimes more rapidly.

“I saw at once that space was annihilated in all the three aspects; in the transport of our bodies and materials and in the earth, transmission of the energies necessary for our existence. You can imagine how profoundly I was affected by this revelation. Technically, it meant that the earth, as a whole, had certain periods of vibrations, and that by by impressing electrical vibrations of the same periods upon it, it could be thrown into oscillations of such nature that innumerable benefits could be derived.

“It is difficult to convey an idea of these inventions without resorting to technical terms. The first and best known of these is my transformer, which enables the production of electrical vibrations of transcending intensities. I have already attained activities of many millions of horse power; but this is nothing compared to those which I am expecting to get with my improved apparatus.

“The second is what I have termed my magnifying transmitter, which I look upon as my best electrical invention, and with which any distance can be bridged. I have already passed of this wonderful instrument and am confident that a message can be flashed to such a distance as the planet Mars.

“Some technical men would be disposed to look upon such statements as those of a dreamer, but it is only because they have not had opportunities to see experiments which I have actually performed. The third invention I have designated as the “Art of individualization,” which enables the transmission of an unlimited number of messages through a wire or wireless, without the slightest interference. Not before this improvement is universally adopted will the world fully realise the benefits of telegraphy and telephony. The fourth invention is my receiver, which concentrates the energy transmitted over a wide area into the operating device.”

What would the voltage in your transmitter be?

“In the transmission of telegraphic and telephonic messages I shall employ from five to ten million volts, but in transmitting power in great quantities, as much as one hundred million volts will be used.“

How will your “World System” compare with those now in use as regards to cost?

“We could easily afford to offer a transmission of telegraphic and telephonic messages to any terrestrial distance for five cents a word. In a short while no one will think it anything out of the way to dictate or to write a long letter across the Pacific.”

How long does it take for the transmission of a message, by your system, around the world?

“The exact time is, according to my measurements, 43-1000 of a second, which is a speed about 50 per cent greater than that of light.

“The impulse starts from my magnifying transmitter with infinite speed, slows first rapidly and then at a lesser rate until, when it has penetrated to a distance of 6000 miles from the transmitter, it proceeds with approximately the speed of light. From there on it accelerates, first slowly and then more rapidly, and reaches the opposite point of the globe again with infinite speed only to rebound and pass through the same phases on its way back to the transmitter.

“This movement of electricity through the Earth, which takes place strictly in accordance with a mathematical law, and enables a great number of accurate measurements and determinations to be made, which are of immense practical and scientific value.”

Is your universal marine service based upon this principle?

“Largely so. In setting up and maintaining stationary waves in the earth its entire surface is subdivided in perfectly definite zones of electric activity, so that any observer of all those data which are of importance to navigators as the latitude and longitude, the position with reference to a given point, the speed of travel, and the course followed. This method is quite exact and reliable, and once introduced will be instrumental in a great saving of time, life and property.”

When your system of time distribution is introduced what kind of devices will be used for indicating the hour?

“They will be ever so much simpler than the ordinary clocks or watches, being entirely devoid of wheel work. For personal use a small case will be provided resembling that of a watch which would indicate precisely the time and require no more attention than a compass for instance. The large clocks on towers and public edifices in general will be replaced by extremely simple devices operated on the same principle.

“All these will be ‘tuned’ to a wireless wave sent out at a certain time. This will automatically set the hands of every ‘tuned’ time piece.”

In operating stock tickers, will the present instruments have to be replaced by others?

“Not at all, they will remain intact. A great financier told me that this should be one of the most valuable and practical applications of my system, inasmuch as the instantaneous operation of such instruments all the world over will go far toward allaying panics and failures which are at present mostly due to the inadequacy and stagnation of channels of information.”

“A business man will be able to dictate in his office a letter which will appear in type at any other place he wishes without loss of time in the transmission. It will be exactly as though he had his stenographer close by. In the same manner it will be practicable to send a handwritten letter or even a check, and what is more important, it will not be possible to falsify the signature.”

Will the transmission of complex musical productions require complicated apparatuses?

“Not at all. The apparatus at any of the master plants, transmitting a great number of musical compositions, will be of necessity complicated, but the subscriber will need only a telephone receiver, and, if he desires exclusiveness, and individualizing device in connection, which, however, will be rarely required. He will be none the less able to listen to the most complex opera played in some remote party of the world. What is more, he can carry the entire outfit with him on his walks and travels, and whenever he desires to listen to the music he can do so.

“The wireless system which I have developed does not contemplate competition with established lighting systems in densely populated districts, but it offers an ideal solution for the illumination of isolated places. The light will be furnished by exhausted glass tubes, bent in all sorts of ornamental shapes, and is of surpassing beauty, resembling closely the daylight. The lamps will last forever. The entire apparatus for lighting the average country dwelling will contain no moving part whatever, and could be readily carried about in a small valise. It will be quite immaterial in which region of the earth the house to be lighted is located. Distance will not affect the charge.“

How far from the Earth’s surface can power be transmitted by this wireless system?

“To any distance; in fact, the greater the elevation above the ground that easier it is to supply the power to the vehicle, such as an airship crossing the ocean.”

What do you consider the most important application of your system?

"The transmission of power, of course. The operation of aerial machines alone will be of a revolutionizing influence, in as much as it will afford a perfect solution of this important problem.

"Another great field will be the irrigation and fertilization of the soil by wireless power. The time is not distance when a farmer will have installed on his place an apparatus for continuously manufacturing, from the gases of the atmosphere, nitric compounds which will be used to fertilize, while a motor will pump the water and perform other duties; all the energy being supplied from a plant perhaps thousands of miles away. This system can be extended so as to make productive vast tracts of now barren lands located in various countries. I believe that the export of wireless power will be one of the chief resources of the United States and other fortunately situated countries in times to come.“

By Marcel Roland. New York American, September 3, 1911.

Mercury ☿

Equatorial Diameter: 4.879 km

Satellites: None

Orbit Distance: 57,909,050 km (0,39 AU)

Orbit Period: 88 Earth days

Surface Temperature: -183 to 427C°