The Milky Way galaxy is our home, and yet in some ways, it is the least understood galaxy. One of the biggest challenges astronomers have is in understanding its large-scale structure. Because we’re in the midst of it all, mapping our galaxy is a bit like trying to map the size and shape of a wooded park while standing in the middle of it.
One of the ways astronomers can map our galaxy is to measure the position and distance of thousands upon thousands of stars. This is one of the main goals of the Gaia mission, which studies the location and motion of more than a billion stars. Gaia has already revealed details in the structure of the Milky Way, such as a wave pattern among some stars.
Another method is to look at specific objects in our galaxy, such as star-forming nebulae. Star-forming nebulae tend to be located within the spiral arms of a galaxy, where there is the most gas and dust. The Spitzer infrared space telescope has measured the distances to young stars within many nebulae, which helped us confirm that the Milky Way has four main spiral arms.
A new study combines data from Gaia and Spitzer, comparing the location of some nebulae with the overall spiral distribution of stars.[^1] The study focused on a main spiral arm within the galaxy known as the Sagittarius Arm. It is the spiral arm just inward from the Sun’s arm of Orion. The team hoped to measure an aspect of the spiral arm known as the pitch angle. It tells you how tightly wound a spiral arm is. The larger the pitch angle, the more open the spiral arms are. In the case of the Sagittarius Arm, the pitch angle is about 12 degrees. But pitch the angle of some nebulae are very different.
The team looked at four prominent nebulae in our night sky: the Eagle Nebula (which contains the Pillars of Creation), the Omega Nebula, the Trifid Nebula, and the Lagoon Nebula. These four nebulae are in the same general region and were used in the 1950s to confirm the existence of the Sagittarius Arm. This new study pinned down the location of these nebulae and other stars and found the region has a pitch angle of 60 degrees.
This doesn’t mean our original measure of the Sagittarius Arm is wrong, but it does point to a type of structure known as galactic spurs. Some spiral galaxies have very smooth spiral arms, where gas, dust, and star-forming regions are all along the same curve. Other spiral galaxies have more broken spiral arms, with small feathery offshoots called spurs. We don’t know for sure which type of galaxy the Milky Way is, but this new study points to it being the latter.
Reference: Kuhn, M. A., et al. “A high pitch angle structure in the Sagittarius Arm.” Astronomy & Astrophysics 651 (2021): L10.
'Happy' SpaceX tourist crew spend first day whizzing around Earth – Phys.org
SpaceX’s all-civilian Inspiration4 crew spent their first day in orbit conducting scientific research and talking to children at a pediatric cancer hospital, after blasting off on their pioneering mission from Cape Canaveral the night before.
St Jude tweeted its patients got to speak with the four American space tourists, “asking the questions we all want to know like ‘are there cows on the Moon?'”
Billionaire Jared Isaacman, who chartered the flight, is trying to raise $200 million for the research facility.
Inspiration4 is the first orbital spaceflight with only private citizens aboard.
Earlier, Elon Musk’s company tweeted that the four were “healthy” and “happy,” had completed their first round of scientific research, and enjoyed a couple of meals.
Musk himself tweeted that he had personally spoken with the crew and “all is well.”
By now, they should have also been able to gaze out from the Dragon ship’s cupola—the largest space window ever built, which has been fitted onto the vessel for the first time in place of its usual docking mechanism.
Most humans in space
The Inspiration4 mission also brings the total number of humans currently in space to 14—a new record. In 2009, there were 13 people on the International Space Station (ISS).
There are currently seven people aboard the ISS, including two Russian cosmonauts, and three Chinese astronauts on spaceship Shenzhou-12, which is bound home after its crew spent 90 days at the Tiangong space station.
Isaacman, physician assistant Hayley Arceneaux, geoscientist Sian Proctor and aerospace data engineer Chris Sembroski are whizzing around the planet at an altitude that at times reaches 590 kilometers (367 miles).
That is deeper in space than the ISS, which orbits at 420 kilometers (260 miles), and the furthest any humans have ventured since a 2009 maintenance mission for the Hubble telescope.
Their ship is moving at about 17,500 mph (28,000 kph) and each day they will experience about 15 sunrises and sunsets.
Their high speed means they are experiencing time slightly slower than people on the surface, because of a phenomenon called “relative velocity time dilation.”
Apart from fundraising for charity, the mission aims to study the biological effects of deep space on the astronauts’ bodies.
“Missions like Inspiration4 help advance spaceflight to enable ultimately anyone to go to orbit & beyond,” added Musk in a tweet.
The space adventure bookends a summer marked by the battle of the billionaires Richard Branson and Jeff Bezos to reach the final frontier.
But these flights only offered a few minutes of weightlessness—rather than the three full days of orbit the Inspiration4 crew will experience, before splashing down off the coast of Florida on Saturday.
© 2021 AFP
‘Happy’ SpaceX tourist crew spend first day whizzing around Earth (2021, September 17)
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Chinese astronauts return after 90-day mission to space station – Al Jazeera English
Shenzhou-12 mission carrying three Chinese men landed safely in the autonomous region of Inner Mongolia in northern China.
Three Chinese astronauts have returned to earth after a 90-day visit to an unfinished space station in the country’s first crewed mission since 2016.
In a small return capsule, the three men – Nie Haisheng, Liu Boming and Tang Hongbo – landed safely in the autonomous region of Inner Mongolia in the north of China at 1:34pm (05:34 GMT), state media reported.
The Shenzhou-12 mission was the first of four crewed missions planned for 2021-2022 as China assembles its first permanent space station. The process requires 11 missions, including the launches of the station’s three modules.
Construction kicked off in April with the launch of the Tianhe module, the future living quarters of the space station. Slightly larger than a city bus, Tianhe was where Nie, Liu and Tang have stayed since mid-June, marking China’s longest spaceflight mission.
While in orbit, the astronauts conducted spacewalks, validated Tianhe’s life-support system, tested the module’s robotic arm, and sorted supplies for upcoming crewed missions.
The second crewed mission is planned for October, with the next batch of astronauts expected to stay on Tianhe for six months.
Ahead of that Shenzhou-13 mission, China will send an automated cargo spacecraft – Tianzhou-3 – to Tianhe carrying supplies needed by the next crew.
Tianzhou-3 will be launched in the near future, state media said recently.
Blocked by US law from working with NASA and by extension on the US-led International Space Station (ISS), China has spent the past 10 years developing technologies to construct its own space station.
China’s space station, expected to be completed by the end of 2022, will be the sole alternative to the 20-year-old ISS, which may be retired in 2024.
900-year-old Chinese supernova mystery points to strange nebula – Space.com
In the year 1181 AD, a new bright point of light as luminous as the planet Saturn appeared to Chinese and Japanese skygazers for a little more than six months before disappearing. Hundreds of years later, researchers believe they have finally found the source of this mysterious appearance.
The event, like the famous Crab Nebula-forming stellar explosion of 1054, is one of just a handful of bright nearby flashes noted in historical records, but unlike the Crab Nebula, the 1181 spectacle was tricky to pin down.
The historical record leaves a few clues that have been useful to modern astronomers. First, the timing: this “guest star” shined for 185 days, from Aug. 6, 1181, to Feb. 6, 1182. The record also indicates its place in the sky, which was a spot located between two Chinese constellations, Chuanshe and Huagai, near the modern Cassiopeia.
These cosmic puzzle pieces led a research team to the ancient flash’s likely culprit: a supernova whose remnants now form a fast-expanding nebula called Pa30. The nebula’s clouds move so quickly that, in the new research, scientists from Hong Kong, the U.K., Spain, Hungary and France found that Pa30’s dust and gas could travel the distance from Earth to the moon in a whopping five minutes. By using that speed and calculating backward, the researchers determined that the nebula would fit a supernova that exploded around 1181.
The team found that Pa30 formed from a rare and relatively faint type of supernova, called a ‘Type Iax supernova.’ “Only around 10% of supernovae are of this type and they are not well understood. The fact that SN1181 was faint but faded very slowly fits this type,” Albert Zijlstra, an astrophysicist at the University of Manchester in the U.K., said in a statement about the new research.
Scientists also found that Parker’s star, one of the hottest stars in the Milky Way, is also a likely counterpart to the supernova. The nebula and the star are thought to be the result of a massive collision and subsequent merger of two dim stellar corpses known as white dwarfs.
“This is the only Type Iax supernova where detailed studies of the remnant star and nebula are possible,” Ziljlstra added. “It is nice to be able to solve both a historical and an astronomical mystery.”
The study was published on Wednesday (Sept. 15) in the journal Astrophysical Journal Letters.
Follow Doris Elin Urrutia on Twitter @salazar_elin. Follow us on Twitter @Spacedotcom and on Facebook.
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