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FREE PREVIEW: All About Space issue 73

Posted: 04 Jan 2018 03:34 AM PST

The latest issue of All About Space is now available from My Favourite Magazines as well as all good supermarkets and newsagents. Read on for a taster of what's in store for you in issue 73.

Elon Musk and Richard Branson exclusive: fight for Mars

It’s the battle of the billionaires: two of the private space industry’s most exciting companies – SpaceX and Virgin Galactic – go head-to-head and they’re proving to be fiercely competitive

Brian Cox, Bill Nye, Michio Kaku & more on… the next big breakthroughs

With our quest to understand the universe excelling on every frontier, All About Space asked some of the world’s most renowned what they think the next huge discovery could be.

Space TED talks you need to watch

Be even more inspired by the universe with All About Space‘s top picks of ideas worth spreading.

Why is our Milky Way so weird?

Finding out may help solve some of the universe’s biggest mysteries.

20 hot astronomy products you need to buy this year

Looking for an upgrade on your telescope? Need a comprehensive guide for touring the night sky? Step this way…

 

Keep up to date with the latest reviews in All About Space – available every month for just £4.99. Alternatively you can subscribe here for a fraction of the price!

Alien megastructure confirmed as unlikely cause of star’s weird behaviour

Posted: 04 Jan 2018 02:52 AM PST

This illustration depicts an uneven ring of dust orbiting KIC 8462852, also known as Boyajian's Star or Tabby’s Star. Image credit: NASA/JPL-Caltech

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 per cent 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 disc, planet, or star, or even large structures in space," says 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 colours 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 says.

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.

Could exocomets – comets orbiting stars outside our Solar System – be responsible for Tabby’s Star? Image credit: NASA

"They're ancient; we are watching things that happened more than 1,000 years ago," the authors wrote. "They're almost certainly caused by something ordinary, at least on a cosmic scale. And yet that makes them more interesting, not less. But most of all, they're mysterious."

The method in which this star is being studied — by gathering and analysing 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 behaviour 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 says. "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 probability of other phenomena being behind the dimming," Wright says. "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 favour 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 says, "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."

Keep up to date with the latest reviews in All About Space – available every month for just £4.99. Alternatively you can subscribe here for a fraction of the price!

Super black holes in massive galaxies control star formation

Posted: 04 Jan 2018 02:21 AM PST

The energy pouring out of the black holes at the centre of massive galaxies are hindering star formation in surrounding regions. Image credit: NASA/JPL-Caltech

Young galaxies are known for creating numerous stars at a rapid rate, which gives off copious amounts of energy. However, as the galaxy evolves, star formation eventually ceases. A team at the University of California Santa Cruz (UCSC), United States, has now stated that the mass of the supermassive black hole at the centre of the galaxy determines how soon the star formation stops inside these galactic structures.

To each massive galaxy is a supermassive black hole residing at its core, and they tend to be over a million times more massive than our own Sun. The enormous mass of this object means that not even light can escape its gravity, hence the term 'black hole'. Although we cannot see the object directly, we can observe the effects on its surroundings, such as the galaxy's own stars and sometimes the powerful energy released by its active galactic nucleus (AGN). It is thought that the energy that is emitted from the AGN is what heats up the surrounding gas, making it unable to condense into stars, also known as quenching.

This theory has been around for decades, and astrophysicists have found from simulations that galaxy evolution must take into account feedback from the black hole to properly reproduce the observed properties of galaxies. However, there has always been a missing link between observational evidence of supermassive black holes and star formation. That is until the team at USCS came along.

“We’ve been dialling in the feedback to make the simulations work out, without really knowing how it happens,” says Jean Brodie, professor of astronomy and astrophysics at UC Santa Cruz. “This is the first direct observational evidence where we can see the effect of the black hole on the star formation history of the galaxy.”

This new study has shown that there is a continuous interplay between black hole activity and star formation throughout the galaxy's life. This interplay affects all generations of stars that have formed as the structure evolves. The study focused primarily on massive galaxies that have had their supermassive black holes mass measured in previous studies. To determine the star formation history, the USCS team analysed spectroscopic data of the galaxies' light, gathered by the Hobby-Eberly Telescope Massive Galaxy Survey.

By separating the light of galaxies into their constituent wavelengths, a postdoctoral researcher at USCS, Ignacio Martín-Navarro, used computational techniques to determine each galaxy's star formation history it's spectra. By matching the best combination of stellar populations to fit the spectroscopic data, the evolutionary state of the galaxy can be deduced.

Supermassive black holes are thought to be surrounded by a thick ring of material known as a 'torus'. Image credit: ESA/V. Beckmann (NASA-GSFC)

When Martín-Navarro compared the star formation history with the black holes of different masses, there were some striking differences. Noticeably, the variations only correlate with black hole masses, but not any other properties such as morphology, size, or others.

“For galaxies with the same mass of stars but different black hole mass in the centre, those galaxies with bigger black holes were quenched earlier and faster than those with smaller black holes," says Martín-Navarro. "So star formation lasted longer in those galaxies with smaller central black holes.”

There has been unsuccessful work into correlations between star formation and the luminosity of AGNs, and Martín-Navarro suggests this may be due to the time-scales being so different. As star formation occurs over hundreds of millions of years, and AGN experiencing outbursts of a much shorter time period, these are noticeable time differences.

A supermassive black hole is only luminous when it is eating surrounding matter. Whereas, AGNs are highly variable and their properties rely on the size of the black hole, the rate of accretion of material among many other factors.

“We used black hole mass as a proxy for the energy put into the galaxy by the AGN, because accretion onto more massive black holes leads to more energetic feedback from active galactic nuclei, which would quench star formation faster,” explains Martín-Navarro.

What exactly is causing this feedback from the black hole that quenches star formation remains unclear. “There are different ways a black hole can put energy out into the galaxy, and theorists have all kinds of ideas about how quenching happens, but there’s more work to be done to fit these new observations into the models,” says Aaron Romanowsky, an astronomer at San Jose State University and UC Observatories.

Keep up to date with the latest reviews in All About Space – available every month for just £4.99. Alternatively you can subscribe here for a fraction of the price!

NIGHT SKY: Where and when to catch the Quadrantid meteor shower

Posted: 04 Jan 2018 01:29 AM PST

The Quadrantids appear to radiate from the asterism, The Plough. Image Credit: Brian Emfinger

The Quadrantids appear to emanate not too far away from The Plough, also known as The Big Dipper. Image Credit: Brian Emfinger

Early January sees the annual maximum of the Quadrantid meteor shower. Meteors – popularly known as ‘shooting stars’ – are the result of small particles entering the Earth’s atmosphere at high speed. These heat the air around them, causing the characteristic streak of light seen from the ground.

The Quadrantids appear to emanate from a point located in the defunct constellation Quadrans Muralis, not far from the familiar asterism of the Plough. They are best viewed in the Northern Hemisphere and just after midnight on 4 January, with around 80 or more expected per hour from dark sites. Unfortunately, the Moon will be present near the constellation of Leo, brightening the sky with a illumination of 94 per cent, as it was only a Full Moon two days prior.

The beauty of watching a meteor shower is that you don't need any equipment other than your eyes. You should find a dark spot with a wide-open view overhead and, in order to watch the sky in comfort, a reclining chair or a blanket that you can lay on the ground is ideal. It is also essential to wrap up warm.

Any light pollution will cut down the number of meteors visible. The best views are on the outskirts of towns and cities and away from artificial light. If you need to find your way around or look at a star map, then you should use a red flashlight to preserve your night vision. Remember, that you should allow 20 minutes for your eyes to adapt to the dark.

Keep up to date with the latest reviews in All About Space – available every month for just £4.99. Alternatively you can subscribe here for a fraction of the price!