OrbitalHub

NASA dicit:

Scientists have discovered that a mysterious pressure dubbed “dark energy” makes up about 68 percent of the total energy content of the cosmos, but so far we don’t know much more about it. Exploring the nature of dark energy is one of the primary reasons NASA is building the Wide Field Infrared Survey Telescope (WFIRST), a space telescope whose measurements will help illuminate the dark energy puzzle. With a better understanding of dark energy, we will have a better sense of the past and future evolution of the universe.

Astronomers have measured the rate of of the universe’s expansion by using ground-based telescopes to study relatively nearby supernova explosions. The mystery escalated in 1998 when Hubble Space Telescope observations of more distant supernovae helped show that the universe actually expanded more slowly in the past than it does today. The expansion of the universe is not slowing down due to gravity, as everyone thought. It’s speeding up.

While we still don’t know what exactly is causing the acceleration, it has been given a name — dark energy. This mysterious pressure remained undiscovered for so long because it is so weak that gravity overpowers it on the scale of humans, planets and even the galaxy. It is only on an intergalactic scale that dark energy becomes noticeable, acting like a sort of weak opposition to gravity.

What exactly is dark energy? More is unknown than known, but theorists are chasing down a couple of possible explanations. Cosmic acceleration could be caused by a new energy component, which would require some adjustments to Einstein’s theory of gravity — perhaps the cosmological constant, which Einstein called his biggest blunder, is real after all.

Alternatively, Einstein’s theory of gravity may break down on cosmological scales. If this is the case, the theory will need to be replaced with a new one that incorporates the cosmic acceleration we have observed. Theorists still don’t know what the correct explanation is, but WFIRST will help us find out.

Discovering how dark energy has affected the universe’s expansion in the past will shed some light on how it will influence the expansion in the future. If it continues to accelerate the universe’s expansion, we may be destined to experience a “Big Rip.” In this scenario, dark energy would eventually become dominant over the fundamental forces, causing everything that is currently bound together — galaxies, planets, people — to break apart. Exploring dark energy will allow us to investigate, and possibly even foresee, the universe’s fate. Watch this video to learn more about dark energy and how WFIRST will study it.

Video Credit: NASA’s Goddard Space Flight Center/Scott Wiessinger (USRA): Lead Producer/Krystofer Kim (USRA): Lead Animator/Chris Smith (USRA): Animator/Sophia Roberts (AIMM): Narrator/Francis Reddy (University of Maryland College Park): Lead Science Writer/Claire Andreoli (NASA/GSFC): Lead Public Affairs Office

NASA dicit:

NASA’s Transiting Exoplanet Survey Satellite (TESS) has discovered a world between the sizes of Mars and Earth orbiting a bright, cool, nearby star. The planet, called L 98-59b, marks the smallest found by TESS yet.

Two other worlds orbit the same star. While all three planets’ sizes are known, further study with other telescopes will be needed to determine if they have atmospheres and, if so, which gases are present. The L 98-59 worlds nearly double the number of small exoplanets — that is, planets beyond our solar system — that have the best potential for this kind of follow-up.

L 98-59b is around 80 Earth’s size and about 10 smaller than the previous record holder discovered by TESS. Its host star, L 98-59, is an M dwarf about one-third the mass of the Sun and lies about 35 light-years away in the southern constellation Volans. While L 98-59b is a record for TESS, even smaller planets have been discovered in data collected by NASA’s Kepler satellite, including Kepler-37b, which is only 20 larger than the Moon.

The two other worlds in the system, L 98-59c and L 98-59d, are respectively around 1.4 and 1.6 times Earth’s size. All three were discovered by TESS using transits, periodic dips in the star’s brightness caused when each planet passes in front of it.

Video Credit: NASA’s Goddard Space Flight Center/Chris Smith (USRA): producer and lead animator/Jeanette Kazmierczak (UMCP): Science Writer

Wikipedia dicit:

The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between 0.5 and 10 keV. Embedded within the solar-wind plasma is the interplanetary magnetic field. The solar wind varies in density, temperature and speed over time and over solar latitude and longitude. Its particles can escape the Sun’s gravity because of their high energy resulting from the high temperature of the corona, which in turn is a result of the coronal magnetic field.

At a distance of more than a few solar radii from the Sun, the solar wind is supersonic and reaches speeds of 250 to 750 kilometers per second. The flow of the solar wind is no longer supersonic at the termination shock. The Voyager 2 spacecraft crossed the shock more than five times between 30 August and 10 December 2007. Voyager 2 crossed the shock about a billion kilometers closer to the Sun than the 13.5-billion-kilometer distance where Voyager 1 came upon the termination shock. The spacecraft moved outward through the termination shock into the heliosheath and onward toward the interstellar medium. Other related phenomena include the aurora (northern and southern lights), the plasma tails of comets that always point away from the Sun, and geomagnetic storms that can change the direction of magnetic field lines.

Video Credit: NASA’s Goddard Space Flight Center/Conceptual Image Lab/Krystofer Kim (USRA): Animator

NASA dicit:

Among the most striking features in the image are the rich colors of the clouds moving toward the Great Red Spot, a storm rolling counterclockwise between two bands of clouds. These two cloud bands, above and below the Great Red Spot, are moving in opposite directions. The red band above and to the right (northeast) of the Great Red Spot contains clouds moving westward and around the north of the giant tempest. The white clouds to the left (southwest) of the storm are moving eastward to the south of the spot.

All of Jupiter’s colorful cloud bands in this image are confined to the north and south by jet streams that remain constant, even when the bands change color. The bands are all separated by winds that can reach speeds of up to 400 miles (644 kilometers) per hour.

Video Credit: NASA Goddard

NASA dicit:

Tour the GJ 357 system, located 31 light-years away in the constellation Hydra. Astronomers confirming a planet candidate identified by NASA’s Transiting Exoplanet Survey Satellite subsequently found two additional worlds orbiting the star. The outermost planet, GJ 357 d, is especially intriguing to scientists because it receives as much energy from its star as Mars does from the Sun.

Credit: NASA’s Goddard Space Flight Center/Chris Smith (USRA): Lead Producer/Chris Smith (USRA): Lead Animator/Francis Reddy (University of Maryland College Park): Lead Science Writer

NASA dicit:

NASA’s Transiting Exoplanet Survey Satellite (TESS) has discovered 21 planets outside our solar system and captured data on other interesting events occurring in the southern sky during its first year of science. TESS has now turned its attention to the northern hemisphere to complete the most comprehensive planet-hunting expedition ever undertaken.

TESS began hunting for exoplanets (or worlds orbiting distant stars) in the southern sky in July of 2018, while also collecting data on supernovae, black holes and other phenomena in its line of sight. Along with the planets TESS has discovered, the mission has identified over 800 candidate exoplanets that are waiting for confirmation by ground-based telescopes.

To search for exoplanets, TESS uses four large cameras to watch a 24-by-96-degree section of the sky for 27 days at a time. Some of these sections overlap, so some parts of the sky are observed for almost a year. TESS is concentrating on stars closer than 300 light-years from our solar system, watching for transits, which are periodic dips in brightness caused by an object, like a planet, passing in front of the star.

On July 18, the southern portion of the survey was completed and the spacecraft turned its cameras to the north. When it completes the northern section in 2020, TESS will have mapped over three quarters of the sky.

Credits: NASA’s Goddard Space Flight Center/Scott Wiessinger (USRA): Lead Producer/Ravyn Cullor (GSFC Interns): Lead Writer/Claire Saravia (NASA/GSFC): Public Affairs Officer/Padi Boyd (NASA/GSFC): Narrator/Scott Wiessinger (USRA): Editor/Chris Smith (USRA): Animator/Walt Feimer (KBRwyle): Animator/Brian Monroe (USRA): Animator/Music: “Elapsing Time” from Killer Tracks