NGC 602
In the Small Magellanic Cloud, a dwarf galaxy around 200,000 light years away from us, a nebula has given birth to a cluster of large blue stars. The stars are around 5 million years old, and are so energetic, they have carved out the shape in the gas and dust, a shock wave from the radiation of the stars.
In the background are galaxies, 100+ million light years away.
source : https://apod.nasa.gov/apod/astropix.html
NGC 3199 lies about 12,000 light-years away, a glowing cosmic cloud in the nautical southern constellation of Carina. The nebula is about 75 light-years across in this narrowband, false-color view.
Image Credit: Mike Selby and Roberto Colombari
Hubble’s Neptune Anniversary Pictures by NASA Goddard Photo and Video
New Science from our Mission to Touch the Sun
In August 2018, our Parker Solar Probe mission launched to space, soon becoming the closest-ever spacecraft from the Sun. Now, scientists have announced their first discoveries from this exploration of our star!
The Sun may look calm to us here on Earth, but it’s an active star, unleashing powerful bursts of light, deluges of particles moving near the speed of light and billion-ton clouds of magnetized material. All of this activity can affect our technology here on Earth and in space.
Parker Solar Probe’s main science goals are to understand the physics that drive this activity — and its up-close look has given us a brand-new perspective. Here are a few highlights from what we’ve learned so far.
1. Surprising events in the solar wind
The Sun releases a continual outflow of magnetized material called the solar wind, which shapes space weather near Earth. Observed near Earth, the solar wind is a relatively uniform flow of plasma, with occasional turbulent tumbles. Closer to the solar wind’s source, Parker Solar Probe saw a much different picture: a complicated, active system.
One type of event in particular drew the eye of the science teams: flips in the direction of the magnetic field, which flows out from the Sun, embedded in the solar wind. These reversals — dubbed “switchbacks” — last anywhere from a few seconds to several minutes as they flow over Parker Solar Probe. During a switchback, the magnetic field whips back on itself until it is pointed almost directly back at the Sun.
The exact source of the switchbacks isn’t yet understood, but Parker Solar Probe’s measurements have allowed scientists to narrow down the possibilities — and observations from the mission’s 21 remaining solar flybys should help scientists better understand these events.
2. Seeing tiny particle events
The Sun can accelerate tiny electrons and ions into storms of energetic particles that rocket through the solar system at nearly the speed of light. These particles carry a lot of energy, so they can damage spacecraft electronics and even endanger astronauts, especially those in deep space, outside the protection of Earth’s magnetic field — and the short warning time for such particles makes them difficult to avoid.
Energetic particles from the Sun impact a detector on ESA & NASA’s SOHO satellite.
Parker Solar Probe’s energetic particle instruments have measured several never-before-seen events so small that all trace of them is lost before they reach Earth. These instruments have also measured a rare type of particle burst with a particularly high number of heavier elements — suggesting that both types of events may be more common than scientists previously thought.
3. Rotation of the solar wind
Near Earth, we see the solar wind flowing almost straight out from the Sun in all directions. But the Sun rotates as it releases the solar wind, and before it breaks free, the wind spins along in sync with the Sun’s surface. For the first time, Parker was able to observe the solar wind while it was still rotating – starting more than 20 million miles from the Sun.
The strength of the circulation was stronger than many scientists had predicted, but it also transitioned more quickly than predicted to an outward flow, which helps mask the effects of that fast rotation from the vantage point where we usually see them from, near Earth, about 93 million miles away. Understanding this transition point in the solar wind is key to helping us understand how the Sun sheds energy, with implications for the lifecycles of stars and the formation of protoplanetary disks.
4. Hints of a dust-free zone
Parker also saw the first direct evidence of dust starting to thin out near the Sun – an effect that has been theorized for nearly a century, but has been impossible to measure until now. Space is awash in dust, the cosmic crumbs of collisions that formed planets, asteroids, comets and other celestial bodies billions of years ago. Scientists have long suspected that, close to the Sun, this dust would be heated to high temperatures by powerful sunlight, turning it into a gas and creating a dust-free region around the Sun.
For the first time, Parker’s imagers saw the cosmic dust begin to thin out a little over 7 million miles from the Sun. This decrease in dust continues steadily to the current limits of Parker Solar Probe’s instruments, measurements at a little over 4 million miles from the Sun. At that rate of thinning, scientists expect to see a truly dust-free zone starting a little more than 2-3 million miles from the Sun — meaning the spacecraft could observe the dust-free zone as early as 2020, when its sixth flyby of the Sun will carry it closer to our star than ever before.
These are just a few of Parker Solar Probe’s first discoveries, and there’s plenty more science to come throughout the mission! For the latest on our Sun, follow @NASASun on Twitter and NASA Sun Science on Facebook.
TODAY IN HISTORY: Blurry but beautiful images of Earth, captured from the orbiting Gemini 7 space capsule on December 8, 1965.
Source: humanoidhistory
A close relationship
Some galaxies are closer friends than others.
While many live their own separate, solitary lives, others stray a little too close to a near neighbour and take their relationship to the next level.
The galaxy in this Picture of the Week, named NGC 6286, has done just that!
Together with NGC 6285, the duo is named Arp 293 and they are interacting, their mutual gravitational attraction pulling wisps of gas and streams of dust from them, distorting their shapes, and gently smudging and blurring their appearances on the sky — to Earth-based observers, at least.
The NASA/ESA Hubble Space Telescope has viewed a number of interacting pairs.
These can have distinctive, beautiful, and downright odd shapes, ranging from sheet music to a spaceship entering a sci-fi-esque wormhole, a bouquet of celestial blooms, and a penguin fiercely guarding its precious egg.
Arp 293 is located in the constellation of Draco (The Dragon), and lies over 250 million light-years from Earth.
ESA/Hubble & NASA, K. Larson et al.; CC BY 4.0
(The dwarf galaxy Sculptor, above, is a companion to the Milky Way galaxy. Astronomers will use Webb to study the motions of stars in Sculptor and Draco, another dwarf companion to the Milky Way. By studying how the stars move, the researchers will be able to determine how the dark matter is distributed in these galaxies. Credits: ESA/Hubble, Digitized Sky Survey 2)
The nearest galaxies to our own Milky Way are its companion dwarf galaxies, which are much smaller than the Milky Way. Van der Marel and his team plan to study the motions of stars in two of these dwarf galaxies, Draco and Sculptor. The orbits of the stars are governed by the gravity arising from the dark matter in each galaxy. By studying how the stars move, the researchers will be able to determine how the dark matter is distributed in these galaxies.
“How structures in the universe formed depends on the properties of the dark matter that comprises most of the mass in the universe,” explained van der Marel. “So we know there’s dark matter, but we don’t know what actually makes up this dark matter. We just know that there is something in the universe that has gravity and it pulls on things, but we don’t really know what it is.”
The team will study the distribution of dark matter in the centers of the dwarf galaxies to determine the temperature properties of this mysterious phenomenon. If dark matter is “cold,” its density will be very high near the centers of the galaxies. If dark matter is “warm,” it will be more homogenous throughout the area approaching the galactic centers.
The nearest large neighbor galaxy of our Milky Way, Andromeda has numerous dwarf galaxy companions, just as the Milky Way does. Van der Marel and his team plan to study how four of those dwarf galaxies are moving around Andromeda, to determine if they are grouped within a flat plane in space, or whether they are moving around Andromeda in all directions.
Unlike the first observation program, the team is not trying to measure how stars inside the dwarf galaxies move. In this study, they are trying to determine how the dwarf galaxies as a whole move around Andromeda. This will provide insights into the process whereby large galaxies form by accretion and accumulation of smaller galaxies, and how exactly that works.
In most models, dwarf galaxies that surround larger galaxies are not expected to lie in a plane. Typically, scientists would expect dwarf galaxies to fly around bigger galaxies in random ways. Slowly, these dwarf companions would lose energy and be accreted into the larger galaxy, which would grow larger still.
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