Tag: astronomy

Why Is The Sky Dark At Night?

That question is not as simple as it may sound. You might think that space appears dark at night because that is when our side of Earth faces away from the Sun as our planet rotates on its axis every 24 hours.

But what about all those other far away suns that appear as stars in the night sky? Our own Milky Way galaxy contains over 200 billion stars, and the entire universe probably contains over 100 billion galaxies.

You might suppose that that many stars would light up the night like daytime!

Until the 20th century, astronomers didn’t think it was even possible to count all the stars in the universe. They thought the universe went on forever. In other words, they thought the universe was infinite.

Besides being very hard to imagine, the trouble with an infinite universe is that no matter where you look in the

night sky, you should see a star.

Stars should overlap each other in the sky like tree trunks in the middle of a very thick forest.

But, if this were the case, the sky would be blazing with light. This problem greatly troubled astronomers and became known as “Olbers’ Paradox.” A paradox is a statement that seems to disagree with itself.

To try to explain the paradox, some 19th century scientists thought that dust clouds between the stars must be absorbing a lot of the starlight so it wouldn’t shine through to us.




But later scientists realized that the dust itself would absorb so much energy from the starlight that eventually it would glow as hot and bright as the stars themselves.

Astronomers now realize that the universe is not infinite. A finite universe—that is, a universe of limited size—even one with trillions and trillions of stars, just wouldn’t have enough stars to light up all of space.

Although the idea of a finite universe explains why Earth’s sky is dark at night, other causes work to make it even darker.

Not only is the universe finite in size, it is also finite in age. That is, it had a beginning, just as you and I did.

The universe was born about 15 billion years ago in a fantastic explosion called the Big Bang. It began at a single point and has been expanding ever since.

Because the universe is still expanding, the distant stars and galaxies are getting farther away all the time. Although nothing travels faster than light, it still takes time for light to cross any distance.

So, when astronomers look at a galaxy a million light years away, they are seeing the galaxy as it looked a million years ago.

The light that leaves that galaxy today will have much farther to travel to our eyes than the light that left it a million years ago or even one year ago, because the distance between that galaxy and us constantly increases.

That means the amount of light energy reaching us from distant stars dwindles all the time. And the farther away the star, the less bright it will look to us.

The universe, both finite in size and finite in age, is full of wonderful sights.

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A Frozen Super-Earth Is Close But You Won’t Want To Visit It

Night by night, star by star, astronomers are edging ever closer to learning just how crowded our universe really is—or at least our galaxy, anyway.

A quarter century after the first exoplanets were found orbiting other stars, statistics from the thousands now known have revealed that, on average, each and every stellar denizen of the Milky Way must be accompanied by at least one world.

Look long and hard enough for a planet around any given star in our galaxy and you are practically guaranteed to find something sooner or later.

But even a crowded universe can be a lonely place. Our planet-rich Milky Way may prove to be life-poor. Of all the galaxy’s known worlds, only a figurative handful resemble Earth in size and orbit.

Each occupying a nebulous “Goldilocks” region of just-rightness—a fairy-tale-simple ideal in which a world is neither too big nor too small, neither too hot nor too cold, to sustain liquid water and life on its surface.

Instead, most of the Milky Way’s planets are worlds theorists failed to predict and have yet to fit comfortably in any conception of habitability: “super-Earths” bigger than our familiar planet but smaller than Neptune.

No super-Earths twirl around our sun for solar system–bound scientists to directly study, making it that much harder to know whether any elsewhere are Goldilocks worlds—or, for that matter, whether any one-size-fits-all metric of habitability is hopelessly naive.




A Frozen Super-Earth?

If you live in a city of millions of people, you are not interested in meeting every one of them—but maybe you want to meet your immediate neighbors,” says lead author Ignasi Ribas, an astronomer at the Institute of Space Studies of Catalonia in Spain.

“This is what we are doing for the planetary systems of the stars that surround us. Otherwise we cannot answer the big questions. How does our solar system and our Earth fit in with the rest of the galaxy?

“Are there other habitable or inhabited planets? Barnard’s Star b is not giving us those answers just yet, but it is telling us part of the story we need to know.”

Located in the constellation of Ophiuchus, Barnard’s Star is so dim in visible light that it cannot be seen with unaided eyes.

Yet it has been a favorite of astronomers since 1916, when measurements revealed its apparent motion across the sky was greater than that of any other star relative to our sun.

A sign of its extremely close cosmic proximity. The star’s nearness to us is only temporary—within tens of thousands of years, its trajectory will have swept it out of our solar system’s list of top five closest stars.

According to Ribas and his colleagues, the candidate planet is at least three times heavier than our own, and circles its star in a 233-day orbit.

That would put it in the torrid orbital vicinity of Venus around our yellow sun, but Barnard’s Star is a comparatively pint-size and dim red dwarf star.

This means its newfound companion is near the “snow line,” the boundary beyond which water almost exclusively exists as frozen ice—a region around other stars thought to be chock-full of planets, but that astronomers have only just begun to probe for small worlds.

Alternatively, the planet might be covered by a thick, insulating blanket of hydrogen leftover from its birth in a spinning disk of gas and dust around its star.

Although hydrogen on smaller, hotter worlds would dissipate into space, super-Earths in frigid orbits might manage to hang on to enough of the gas to build up a massive planet-warming greenhouse effect—a possibility that throws Earth-centric Goldilocks ideas into tumult.

If this mechanism operates on Barnard’s Star b or other cold super-Earths, “our dreams that every star may have a habitable planet could well come true,” says Sara Seager, a planet-hunting astrophysicist at Massachusetts Institute of Technology who was not involved with Ribas’s study.

“There are some crazy worlds out there.”

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Mysterious Interstellar Object Floating In Space Might Be Alien, Say Harvard Researchers

A graphic showing `Oumuamua’s path through the Solar System.

The head of Harvard’s department of astronomy thinks that there’s a possibility that a strange object that visited our Solar System from interstellar space may be an alien probe sent from a distant civilization.

He and a colleague outlined their idea in a paper published this week analyzing what the mysterious space object might be, setting off a media frenzy.

But let’s take a breath before we jubilantly cry “aliens.” A single idea about what this object could be doesn’t make it the only explanation, and many scientists still argue that a natural explanation is more plausible.

To add a bit of context, one of the scientists making this “exotic” claim is currently working on an initiative to look for extraterrestrial life in deep space, by sending probes from Earth to other star systems.

The paper that captured everyone’s attention is written by Harvard astrophysicists Avi Loeb and Shmuel Bialy, who tried to describe some weird behavior exhibited by a space rock called `Oumuamua.

Spotted last October, `Oumuamua is a mysterious object that is passing through our Solar System, coming from some unknown deep-space origin.

Objects like this one are thought to pass through our Solar System all the time, but this is the first exo-comet — or a comet from outside our cosmic neighborhood — that we’ve ever detected.

In addition to being a rare find, `Oumuamua is a bit bizarre. Astronomers expected a visitor of this kind to be an icy comet, surrounded by a trail of gas and dust as it passed close to the Sun.




But `Oumuamua seems to lack this kind of cloud, making it look more like an asteroid, which is mostly made of rock and metal. So no one was quite sure what this thing was — a comet, an asteroid, or something totally new.

Then after analyzing `Oumuamua’s orbit, scientists from the European Space Agency noticed that the object was accelerating, more so than it should be if it was just interacting with the gravity of the planets and Sun in our Solar System.

They concluded that `Oumuamua must be a comet; the Sun is likely heating up ice within the object, creating gas that provides an extra boost of speed.

However, Loeb and Bialy are skeptical about this “outgassing” claim, mostly because no one was able to observe gas and dust coming from `Oumuamua.

They also point to recent research from another lab, which is still under review by other scientists, that indicates that if gas were coming from this object, it would change how the rock is rotating — something that hasn’t been observed.

This rules out the possibility that it’s a comet,” Loeb said.

The comet ISON and its tail of gas and dust, as seen by the Hubble Space Telescope

Of course, the possibility exists. But aliens are a very bold claim to make when natural explanations are still on the table.

I can understand the excitement, and as a scientist, I can’t sit here and say I have 100 percent evidence this was a natural object,” Fitzsimmons says. “It’s just that all the observations can be matched with a natural object.”

And that could be a problem when we actually do find signs of alien life one day.

Astronomers are finding new planets outside our Solar System all the time, and we’re working on more sophisticated technology to peer into the atmospheres of these worlds.

One day, we may find solid evidence that life exists in deep space, but it may be hard for the public to swallow if they think aliens have already been discovered.

I don’t want people to think we already saw that when it actually happens,” says Mack. “I want people not to be super cynical about claims about aliens by the time we actually have something that is really solid evidence.”

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Why Is Pluto No Longer A Planet?

In 2006, Pluto was voted out of the planetary club by members of the International Astronomical Union

But in 2006, it was relegated to the status of dwarf planet by the International Astronomical Union (IAU). So why was Pluto demoted?

Where did the controversy start?

Pluto was discovered in 1930 by US astronomer Clyde Tombaugh, who was using the Lowell Observatory in Arizona.

Textbooks were swiftly updated to list this ninth member in the club. But over subsequent decades, astronomers began to wonder whether Pluto might simply be the first of a population of small, icy bodies beyond the orbit of Neptune.

This region would become known as the Kuiper Belt, but it took until 1992 for the first “resident” to be discovered.

The candidate Kuiper Belt Object (KBO) 1992 QBI was detected by David Jewitt and colleagues using the University of Hawaii’s 2.24m telescope at Mauna Kea.




How did this change things?

Confirmation of the first KBO invigorated the existing debate. And in 2000, the Hayden Planetarium in New York became a focus for controversy when it unveiled an exhibit featuring only eight planets.

The planetarium’s director Neil deGrasse Tyson would later become a vocal figure in public discussions of Pluto’s status.

But it was discoveries of Kuiper Belt Objects with masses roughly comparable to Pluto, such as Quaoar (announced in 2002), Sedna (2003) and Eris (2005), that pushed the issue to a tipping point.

Eris, in particular, appeared to be larger than Pluto – giving rise to its informal designation as the Solar System’s “tenth planet“.

The discovery of other icy objects similar in size to Pluto forced a re-think by the IAU

Prof Mike Brown of the California Institute of Technology (Caltech), who led the team that found Eris, would later style himself as the “man who killed Pluto”, while deGrasse Tyson would later jokingly quip that he had “driven the getaway car”.

The finds spurred the International Astronomical Union to set up a committee tasked with defining just what constituted a planet, with the aim of putting a final draft proposal before members at the IAU’s 2006 General Assembly in Prague.

Under a radical early plan, the number of planets would have increased from nine to 12, seeing Pluto and its moon Charon recognised as a twin planet, and Ceres and Eris granted entry to the exclusive club. But the idea met with opposition.

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Scientists Are Tracing the Source of One of the Most Mysterious Signals in Space

Over the past decade, we’ve found out a great deal about what fast radio bursts (FRBs) are — millisecond-long blips of intense radio emissions from deep space — but their origins remain a mystery.

Now, astronomers have tracked a repeating FRB to a dwarf galaxy nearly three billion lightyears from Earth, according to a report.

The international team, which presented its work at the annual American Astronomical Society meeting last January 2018, observed that the radio beam was being contorted by a magnetic field within a cloud of ionized gas, telling us more about the conditions these bursts take place in.




The study detailing the team’s results was recently published in Nature.

We see a sort of ‘twisting’ of the radio bursts caused by an effect known as Faraday rotation,” Jason Hessels, one of the co-authors of the study from the Netherlands Institute for Radio Astronomy, told Futurism.

We hypothesize that the source of the bursts could be a neutron star in the proximity of a massive black hole that is accreting material from its surroundings, or maybe that it is a very young neutron star embedded in a nebula (a sort of cocoon around the source).

We are basically pushing forward and zooming in even further on where these fast radio bursts are coming from,” co-author Shami Chatterjee, a senior research associate from the Cornell Center for Astrophysics and Planetary Science said.

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What Makes A Star A Star?

How do you separate a true star from the stellar wannabes of the Universe? After a decade of collecting data, astronomer Trent Dupuy thinks he finally has the answer.

With so many objects known to sit in that weird middle ground between giant planets and tiny stars, scientists have struggled to boil it down to a simple answer. What Dupuy boils it down to is mass.

Mass is the single most important property of stars because it dictates how their lives will proceed,” Dupuy, from the University of Texas at Austin, explained at the American Astronomical Society’s summer meeting earlier this month.

We benefit from that here on Earth, as our Sun is in the stellar goldilocks zone – its mass is just right to sustain nuclear fusion within its core for billions of years. This has provided the conditions for life to develop and evolve on our planet.

But not everything in the galaxy is so nice and stable. More massive stars burn through their nuclear fuel quicker, dye young, and go out with a violent bang in the form of a supernova.

Less massive objects, like brown dwarfs, are like stellar runts, possessing more mass than a planet, yet not enough mass to be a fully fledged star.

Often referred to as failed stars, they’re ubiquitous throughout the Universe, but their exceedingly dim glow makes these objects difficult to study.




First proposed to exist 50 years ago, these enigmatic objects help bridge the gap between stars and planets, but it wasn’t until more recently that astronomers began to study them in great detail.

Stars like the Sun shine as a result of nuclear reactions that constantly converts the supply of hydrogen in their cores into helium.

These same reactions determine how bright a star shines – the hotter the core, the more intense the reaction and subsequently the brighter the star’s surface will be. As expected, less massive stars are dimmer due to cooler centres, which produce slower reactions.

Don’t let the name fool you – brown dwarfs aren’t always brown. These stellar wannabes are actually red when they form, then turn to black as they slowly fizzle out over trillions of years.

That’s because despite outweighing even the largest of planets, brown dwarfs have so little mass that their centres aren’t hot enough to sustain nuclear reactions.

In the 1960s, astronomers theorised that there must be a mass limit for fusion.

Previous studies of stellar evolution have suggested that the boundary between red dwarfs (the smallest stars) and brown dwarfs was around 75 Jupiter masses (or roughly 7-8 percent of the Sun).

But until now, his measurement was never directly confirmed.

Dupuy and Michael Lui of the University of Hawaii spent the past 10 years studying 31 binary pairs of brown dwarfs with the help of the most powerful telescopes on Earth – the Keck Observatory and the Canada-France-Hawaii Telescope, as well as some input from Hubble.

By analysing a decade’s worth of imagery, Dupuy and Liu have created the first large sample study of brown dwarfs masses.

According to Dupuy, an object must weigh the equivalent of 70 Jupiters in order to spark nuclear fusion and become a star, which is slightly less than previously suggested.

The duo also determined there’s a temperature cut-off, with any object cooler than 1,600 Kelvin (approximately 1,315 Celsius and 2,400 degrees Fahrenheit) classified as a brown dwarf.

The study will help astronomers better understand the conditions under which stars form and evolve – or in the case of brown dwarfs, fail.

It could also provide new insight into planetary formation as the success or failure of star formation directly impacts the star systems they could potentially produce.

The research will be published in an upcoming edition of The Astrophysical Journal Supplement, and a pre-print is available here.

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Astronomers May Have Discovered The First Moon Ever Found Outside Our Solar System

An artistic rendering of the Kepler-1625b planetary system.

A pair of astronomers believes they’ve found a moon orbiting a planet outside our Solar System — something that has never before been confirmed to exist.

Though they aren’t totally certain of their discovery yet, the find opens up the possibility that more distant moons are out there. And that could change our understanding of how the Universe is structured.

The astronomy team from Columbia University found this distant satellite, known as an exomoon, using two of NASA’s space telescopes.

They first spotted a signal from the object in data collected by the planet-hunting telescope Kepler, and then they followed up with the Hubble Space Telescope, which is in orbit around Earth.

Thanks to the observations from these two spacecraft, the team suspect this moon orbits around a Jupiter-sized planet located about 4,000 light-years from Earth. And this planet, dubbed Kepler-1625b, orbits around a star similar to our Sun.

Scientists have strongly believed for decades that moons exist outside our Solar System, but these objects have remained elusive for scientists up until now.




There have been just a couple of candidates that astronomers have speculated about in the past, but nothing has been confirmed.

That’s because moons are thought to be too small and too faint to pick up from Earth. However, this suspected exomoon, detailed today in the journal Science Advances, is particularly large, about the size of Neptune, making it one of the few targets that our telescopes can detect.

You can make the argument that this is the lowest hanging fruit,” Alex Teachey, an astronomy graduate student at Columbia University and one of the lead authors on the paper said.

“Because it is so large, in some ways, this is the first thing we should detect because it is the easiest.”

Teachey argues that finding more moons outside our Solar System will change our understanding of how planetary systems formed thousands of light-years away.

Our cosmic neighborhood is filled with moons, and they explain a lot about how our planets came to be. Exomoons could tell similar tales.

NASA’s Hubble Space Telescope.

However, none of our moons come close to the size of this one, which creates a puzzle for astronomers.

Because it is so unusual, or at least has not been anticipated largely by the community, this poses new challenges to explain it,” says Teachey. “How do you get something like this?

It was only a few decades ago — in the late 1980s and early 1990s — that astronomers confirmed the existence of planets outside our Solar System.

Since then, thousands of these distant worlds, known as exoplanets, have been confirmed by spacecraft like Kepler and other telescopes.

Perhaps the most popular way to find exoplanets is by staring at stars, waiting for them to flicker. When a planet crosses “in front” of its host star, it dims the stars’ light ever so slightly.

These dips in brightness can be used to determine how big a planet is and the kind of orbit it’s on.

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Over The Past Nineteen Years, This Man Has Dedicated His Work To The Study Of Our Solar System

Dr. Franck Marchis is a senior planetary astronomer and chair of the exoplanet group at the Carl Sagan Center of the SETI Institute and Chief Scientific Officer and Founder at Unistellar.

He began full-time work at the Institute in June 2011 after leaving a joint position with Institute and the department of astronomy at University of California, Berkeley.

Marchis moved to the United States in October 2000 shortly after getting a Ph.D. from the University of Toulouse in France that he acquired while traveling around the world for his research and for the sake of exploration.

Over the past nineteen years, he has dedicated his work to the study of our solar system, specifically the search for asteroids with moons, using mainly ground-based telescopes equipped with adaptive optics (AO).

More recently he has been also involved in the definition of new generation of AOs for 8 -10 m class telescopes and future Extremely Large Telescopes.

He has also developed algorithms to process and enhance the quality of astronomical and biological images.




He is currently the collaboration manager of the Gemini Planet Imager Exoplanet Survey, which consists in imaging and characterizing Jupiter-like exoplanets using an extreme AO system designed for the Gemini South telescope.

Today, Marchis dedicates most of his energy to instruments capable of imaging and characterizing Earth-like exoplanets by being involved in education, public outreach, technology, and scientific investigations related to those ambitious projects both in the United States and in Europe.

Marchis is also involved in startups related to astronomy so he joined Unistellar as a Chief Scientific Officer and VR2Planets as a scientific advisor in 2017.

Marchis is a member of numerous science committees including the SETI Science council, the GPI steering Committee, the TMT Science Definition Team, PLOS One editor board, the Project Blue and the PLANETS Foundation Advisory board.

He has co-authored more than 380 scientific publications, trained numerous students, and served as a science consultant and interviewee for numerous documentaries and movies in English, French, and Spanish.

The asteroid (6639) was named Marchis in honor of his discovery of the first triple-asteroid system in 2007. He has been an affiliated Astronomer at Observatoire de Paris since 2003.

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Gravitational Wave Detection Is Going Through An Even Tighter Squeeze

A team of researchers from the Max Planck Institute for Gravitational Physics (Albert Einstein Institute; AEI) in Hannover and from the Institute for Gravitational Physics at Leibniz Universität Hannover has developed an advanced squeezed-light source for the gravitational-wave detector Virgo near Pisa.

Now, the Hannover scientists have delivered the setup, installed it, and handed it over to their Virgo colleagues.

Beginning in autumn 2018 Virgo will use the squeezed-light source to listen to Einstein’s gravitational waves together with the worldwide network of detectors with higher sensitivity than ever before.

The German-British gravitational-wave detector GEO600 near Hannover has been routinely using a squeezed-light source since 2010.

“It has increased the part of the Universe that GEO600 listens to by a factor of up to four,” says Prof. Karsten Danzmann, director at the AEI Hannover and director of the Institute for Gravitational Physics at Leibniz Universität Hannover.

“The development and perfection of the cutting-edge technology is another successful chapter in the history of GEO600 as think thank of gravitational-wave research.”




Both US LIGO instruments and the Virgo detector based in Tuscany are currently being upgraded and improved in preparation of the next joint observation run “O3” which is planned to commence in autumn 2018.

O3 is expected to usher in full-scale gravitational-wave astronomy through a large number of further gravitational-wave detections from merging binary black holes and additional signals from merging neutron star pairs.

For this purpose, Virgo has now received a valuable addition from Hannover: A setup called a squeezed-light source is expected to significantly increase Virgo’s sensitivity from the beginning of O3.

The custom-made device is a permanent loan of the AEI to Virgo and is worth about 400,000 Euros.

The sensitivity of all interferometric gravitational-wave detectors (LIGO, Virgo, and GEO600) to the ripples of space-time from large cosmic events is fundamentally limited by quantum mechanical effects.

They cause a background noise which overlaps with the gravitational-wave signal that is measured with laser light.

The sensitivity of all interferometric gravitational-wave detectors can only be further increased in the future through the use of similar squeezed-light sources.

Planned third-generation detectors like the Einstein Telescope will also depend on this technology.

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Mars Is Spectacular This Month – Here’s The Best Way To Spy The Red Planet

If you look at the sky tonight and spot a very bright star, it may well be a planet. Mars is the closest it has been to Earth for 15 years – and therefore the brightest.

Mars shines through reflected light,” says Robert Massey, the deputy executive director of the Royal Astronomical Society.

That means that when it’s closer to the Earth it appears brighter, because its apparent size is bigger.” It won’t be this visible again until 2035.

So, how best to see it? First, make sure tall trees or buildings are not obscuring the view. Ideally, you want a clear horizon. Then, look south.




It will be obvious, because it’s bright, it doesn’t twinkle and it has a distinct reddish tinge,” says Massey, who suggests Somerset, Devon and Dorset as good locations for spotting it.

The best Mars-gazing time is 1am, but it rises earlier in the evening.

You can see Mars with the naked eye, but a pair of binoculars would help,” says Massey. “If you have a small telescope, you may be lucky to see a polar ice cap.

If you are an amateur with good equipment, the details to look out for are two polar ice caps, mountains or volcanoes, and sunken, crater-like features. Massey suggests contacting your local astronomical society about public viewing events.

Hubble’s views of Mars at two recent oppositions

When is the best time to see Mars?

According to NASA, Mars Opposition begins Friday, July 27 around midnight.

Mars will be visible between Friday, July 27 and Monday, July 30, making its closest approach — 35.8 million miles to be exact — on Tuesday, July 31 at around 4 a.m. E.T.

Mars will be at its brightest Friday night due to an opposition surge that is affected by the planet’s angle of the sun — giving you the clearest view of the Red Planet.

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