Starsglaxiesspace - SPACE

Jupiter’s surface

The aurora australis at Saturn’s southern pole.

Right now Chandra is studying a galaxy in Ursa Major. Nearby in this dwarf galaxy, stars are forming at a furious rate! The galaxy, known as I Zwicky 18, is located about 59 million light years from Earth.

The constellation name, Ursa Major, means Big Bear. The “bear” association has its origins in two major civilizations which saw two very different bears in the sky. The Greeks who named this constellation (later translated into the Latin name we use today) thought that the stars outlined the shape of a bear walking about on its clawed feet. It and its smaller companion, Ursa Minor were said to be the prey of Boötes and his hunting dogs. The long cat-like tail on the bears was part of the ancient pattern and is somewhat of a mystery. A story in Ovid tried to offer an explanation. In that myth, Zeus fell in love with Callisto. Hera changed her into a bear out of jealousy. Her son Arcus (the namesake of Arcturus, the alternate name for the constellation Boötes) came upon her in the forest and she ran to greet him. Not knowing the bear was his mother, he was about to kill her. To save her, Zeus turned Arcus into a smaller bear, grabbed them both by their tails and flung them into the sky, causing their tails to be stretched. A number of Native American tribes also referred to this constellation as a bear, but with a clever addition. In their description of these stars, the bear is the same, but without the “tail”. Instead, those three stars are three hopeful hunters, and the middle one is carrying a cooking pot for cooking up the bear. Johannes Hevelius’ Ursa Major from Uranographia (1690) The most common pattern seen in this constellation is composed of a smaller group of the brightest stars (called an asterism) that outline the Big Dipper. This name comes from many different cultures which have seen in these stars a long handled spoon, often used for dipping water for drinking. Others call this pattern a plow, seeing instead of a dipper, an old-style, ox-pulled farm plow. The plow pattern, pulled by oxen, is the shape referenced in the myth of the Triones, the oxen and plow driven by Bootes the herder. The Egyptians and the Chinese saw different associations. Even in relatively more modern times, early European civilizations continued to invent new meanings for this pattern.

Constellation map from: http://www.lunarplanner.com/StarsProperMotion/UrsaMajor/

For a list of objects in Ursa Major that Chandra has observed and article, see link:  http://chandra.si.edu/photo/constellations/ursamajor.html

3D Motions of Stars in Sculptor Dwarf Galaxy Hint at Underlying Dark Matter

http://www.sci-news.com/astronomy/sculptor-dwarf-galaxy-dark-matter-05477.html

Alien megastructure not the cause of dimming of the ‘most mysterious star in the universe’

A team of more than 200 researchers, including Penn State Department of Astronomy and Astrophysics Assistant Professor Jason Wright and led by Louisiana State University’s Tabetha Boyajian, is one step closer to solving the mystery behind the “most mysterious star in the universe.”

KIC 8462852, or “Tabby’s Star,” nicknamed after Boyajian, is otherwise an ordinary star, about 50 percent bigger and 1,000 degrees hotter than the Sun, and about than 1,000 light years away. However, it has been inexplicably dimming and brightening sporadically like no other.

Several theories abound to explain the star’s unusual light patterns, including that an alien megastructure is orbiting the star.

The mystery of Tabby’s Star is so compelling that more than 1,700 people donated over $100,000 through a Kickstarter campaign in support of dedicated ground-based telescope time to observe and gather more data on the star through a network of telescopes around the world.

As a result, a body of data collected by Boyajian and colleagues in partnership with the Las Cumbres Observatory is now available in a new paper in The Astrophysical Journal Letters.

“We were hoping that once we finally caught a dip happening in real time we could see if the dips were the same depth at all wavelengths.

If they were nearly the same, this would suggest that the cause was something opaque, like an orbiting disk, planet, or star, or even large structures in space” said Wright, who is a co-author of the paper, titled “The First Post-Kepler Brightness Dips of KIC 8462852.” Instead, the team found that the star got much dimmer at some wavelengths than at others.

“Dust is most likely the reason why the star’s light appears to dim and brighten. The new data shows that different colors of light are being blocked at different intensities. Therefore, whatever is passing between us and the star is not opaque, as would be expected from a planet or alien megastructure,” Boyajian said.

The scientists closely observed the star through the Las Cumbres Observatory from March 2016 to December 2017. Beginning in May 2017 there were four distinct episodes when the star’s light dipped.

Supporters from the crowdfunding campaign nominated and voted to name these episodes. The first two dips were named Elsie and Celeste. The last two were named after ancient lost cities – Scotland’s Scara Brae and Cambodia’s Angkor. The authors write that in many ways what is happening with the star is like these lost cities.

The method in which this star is being studied – by gathering and analyzing a flood of data from a single target – signals a new era of astronomy. Citizen scientists sifting through massive amounts of data from the NASA Kepler mission were the ones to detect the star’s unusual behavior in the first place.

The main objective of the Kepler mission was to find planets, which it does by detecting the periodic dimming made from a planet moving in front of a star, and hence blocking out a tiny bit of starlight. The online citizen science group Planet Hunters was established so that volunteers could help to classify light curves from the Kepler mission and to search for such planets.

“If it wasn’t for people with an unbiased look on our universe, this unusual star would have been overlooked,” Boyajian said. “Again, without the public support for this dedicated observing run, we would not have this large amount of data.”

Now there are more answers to be found. “This latest research rules out alien megastructures, but it raises the plausibility of other phenomena being behind the dimming,” Wright said. “There are models involving circumstellar material – like exocomets, which were Boyajian’s team’s original hypothesis – which seem to be consistent with the data we have.”

Wright also points out that “some astronomers favor the idea that nothing is blocking the star – that it just gets dimmer on its own – and this also is consistent with this summer’s data.”

Boyajian said, “It’s exciting. I am so appreciative of all of the people who have contributed to this in the past year – the citizen scientists and professional astronomers. It’s quite humbling to have all of these people contributing in various ways to help figure it out.”

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