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Monday, January 19, 2015

How Long Have Humans Been On Earth?

Lights from the United States glow in this night image based on data taken from the Suomi NPP satellite in April and October 2012. Credit: NASA Earth Observatory/NOAA NGDC

While our ancestors have been around for about six million years, the modern form of humans only evolved about 200,000 years ago. Civilization as we know it is only about 6,000 years old, and industrialization started in the earnest only in the 1800s. While we’ve accomplished much in that short time, it also shows our responsibility as caretakers for the only planet we live on right now.

The effects of humans on Earth cannot be understated. We’ve been able to survive in environments all over the world, even harsh ones such as Antarctica. Every year, we fell forests and destroy other natural areas, driving species into smaller areas or into endangerment, because of our need to build more housing to contain our growing population.

With seven billion people on Earth, pollution from industry and cars is a growing element in climate change — which affects our planet in ways we can’t predict. But we’re already seeing the effects in melting glaciers and rising global temperatures.

Enormous chuck of ice breaks off the Petermann Glacier in Greenland. Credit: NASA.

The first tangible link to humanity started around six million years ago with a primate group called Ardipithecus, according to the Smithsonian Institution. Based in Africa, this group began the path of walking upright. This is traditionally considered important because it allowed for more free use of the hands for toolmaking, weaponry and other survival needs.

The Australopithecus group, the museum added, took hold between about two million and four million years ago, with the abilities to walk upright and climb trees. Next came Paranthropus, which existed between about one million and three million years ago. The group is distinguished by its larger teeth, giving a wider diet.

The Homo group — including our own species, Homo sapiens — began arising more than two million years ago, the museum said. It’s distinguished by bigger brains, more tool-making and the ability to reach far beyond Africa. Our species was distinguished about 200,000 years ago and managed to survive and thrive despite climate change at the time. While we started in temperate climates, about 60,000 to 80,000 years ago the first humans began straying outside of the continent in which our species was born.

GOCE view of Africa.. Credits: ESA/HPF/DLR, anaglyph by Nathanial Burton-Bradford.

“This great migration brought our species to a position of world dominance that it has never relinquished,” reads a 2008 article in Smithsonian Magazine, pointing out that eventually we obviated the competition (most prominently including Neanderthals and Homo erectus). When the migration was complete,” the article continues, “Homo sapiens was the last—and only—man standing.”

Using genetic markers and an understanding of ancient geography, scientists have partially reconstructed how humans could have made the journey. It’s believed that the first explorers of Eurasia went there using the Bab-al-Mandab Strait that now divides Yemen and Djibouti, according to National Geographic. These people made it to India, then by 50,000 years ago, southeast Asia and Australia.

A little after this time, another group began an inland journey across the Middle East and south-central Asia, positioning them to later go to Europe and Asia, the magazine added. This proved important for North America, as about 20,000 years ago, some of these people crossed over to that continent using a land bridge created by glaciation. From there, colonies have been found in Asia dating as far back as 14,000 years ago.

A teensy-tiny Neil Armstrong is visible in the helmet of Buzz Aldrin during the Apollo 11 landing in July 1969. Credit: NASA

Since this is a space website, it’s also worth noting when humans began leaving Earth. The first human mission to space took place April 12, 1961 when Soviet cosmonaut Yuri Gagarin made a single orbit of Earth in his spacecraft, Vostok 1. Humanity first set foot on another world on July 20, 1969, when Americans Neil Armstrong and Buzz Aldrin walked on the Moon.

Since then, our colonization efforts in space have focused mostly on space stations. The first space station was the Soviet Salyut 1, which launched from Earth April 19, 1971 and was first occupied by Georgi Dobrovolski, Vladislav Vokov, and Viktor Patsayev on June 6. The men died during re-entry June 29 due to spacecraft decompression, meaning no further flights went to that station.

There have been other space stations since. A notable example is Mir, which hosted several long-duration missions of a year or more — including the longest single spaceflight duration of any human to date, 437 days, by Valeri Polyakov in 1994-95. The International Space Station launched its first piece Nov. 20, 1998 and has been continuously occupied by humans since Oct. 31, 2000. The first humans to start the continuous occupation included Expedition 1 members Bill Shepard (U.S.) and Russian cosmonauts Sergei Krikalev and Yuri Gidzenko.

About Elizabeth Howell

Elizabeth Howell is the senior writer at Universe Today. She also works for Space.com, Space Exploration Network, the NASA Lunar Science Institute, NASA Astrobiology Magazine and LiveScience, among others. Career highlights include watching three shuttle launches, and going on a two-week simulated Mars expedition in rural Utah. You can follow her on Twitter @howellspace or contact her at her website.

Here’s Dawn’s Best View of Ceres Yet

Here’s Dawn’s Best View of Ceres Yet:

Animation of Ceres made from Dawn images acquired on Jan. 13, 2015 (Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI)

Just sit back and watch the world turn… or should I say, watch the dwarf planet turn in this fascinating animation from Dawn as the spacecraft continues on its ion-powered approach to Ceres!

The images were captured by Dawn’s framing camera over the course on an hour on Jan. 13 at a distance of 238,000 miles (383,000 km) from Ceres. At 590 miles (950 km) wide Ceres is the largest object in the main asteroid belt.

“Already, the [latest] images hint at first surface structures such as craters,” said Andreas Nathues, lead investigator for the framing camera team at the Max Planck Institute for Solar System Research in Gottingen, Germany. “We have identified all of the features seen by Hubble on the side of Ceres we have observed, and there are also suggestions of remarkable structures awaiting us as we move even closer.”

Although these latest 27-pixel images from Dawn aren’t quite yet better than Hubble’s images from Jan. 2004, very soon they will be.

Comparison of HST and Dawn FC images of Ceres taken nearly 11 years apart

“The team is very excited to examine the surface of Ceres in never-before-seen detail,” said Chris Russell, principal investigator for the Dawn mission, based at the University of California, Los Angeles. “We look forward to the surprises this mysterious world may bring.”

Launched Sept. 27, 2007, Dawn previously spent over 13 months in orbit around the asteroid/protoplanet Vesta from 2011–12 and is now on final approach to Ceres. On March 6 Dawn will arrive at Ceres, becoming the first spacecraft to enter orbit around two different target worlds.

Read more: Find Out How “Crazy Engineering” is Getting Dawn to Ceres

Learn more at JPL’s Dawn mission site here, and find out where Dawn is right now here.

Also, read more from the Max Planck Institute for Solar System Research here.

Source: NASA/MPI

About Jason Major

A graphic designer in Rhode Island, Jason writes about space exploration on his blog Lights In The Dark, Discovery News, and, of course, here on Universe Today. Ad astra!

Where to Look for Comet Lovejoy Until it Fades from Sight

Where to Look for Comet Lovejoy Until it Fades from Sight:

Viewing Comet Lovejoy from dark skies in Portugal. Credit: Miguel Claro

Viewing Comet Lovejoy with binoculars from dark skies in Portugal on January 11th. Credit: Miguel Claro

I hate to admit it, but our dear comet is fading. Only a little though. As Comet Q2 Lovejoy wends its way from Earth toward perihelion and beyond, it will slowly dim and diminish. With an orbital period of approximately 8,000 years it has a long journey ahead. Down here on Earth, we continue to look up every clear night hoping for yet another look at what’s been a wonderful comet.

Comet Lovejoy and the Pleiades on January 19, 2015. Credit: Joseph Brimacombe

Despite its inevitable departure I encourage you to continue following Comet Lovejoy. It’s not often a comet vaults to naked eye brightness, and this one should remain visible without optical aid through mid-February.

Like a human celebrity, Lovejoy’s been the focus of attention from beginners and professionals alike using everything from cheap cellphone cameras to high-end telescopes to capture its magic. Who can get enough of that wildly fluctuating ion tail and greeny-blue coma?

Comet Q2 Lovejoy continues tracking north-northwest now through March. This chart shows the comet’s position at 7 p.m. (CST) every 5 nights through March 5. Stars shown to magnitude +6. Click to enlarge. Created with Chris Marriott’s SkyMap software

The comet continues moving northward all winter long, sliding through the diminutive constellations Aries and Triangulum, across Andromeda and into Cassiopeia, fading as she goes. You can use the map above and binoculars to help you follow it. I like to create lines and triangles using bright stars and deep sky objects to direct me to the comet.

Deep image of Comet Lovejoy taken with a Canon 6D with 50mm f/1.4 lens at f/2. 10 exposure of 30 secs at ISO3200 stacked. The tail, though faint, extends for possibly 18 degrees in this amazing image. Credit: Ian Sharp

Deep image of Comet Lovejoy taken with a Canon 6D with 50mm f/1.4 lens at f/2. Ten exposures of 30 secs at ISO3200 were stacked to create the final photo. The tail extends for possibly 18 degrees in this amazing image. The Pleiades are at top right; Hyades at bottom center. Credit: Ian Sharp

Tonight for instance, Lovejoy one fist held at arm’s length due west of the Pleiades. On the 29th, it’s on a line from Beta Persei (Algol) to Beta Trianguli. On February 3rd, it pulls right up alongside the colorful double star Gamma Andromedae, also called Almach, and on the 8th forms one of the apexes of an equilateral triangle with the two Betas. You get the idea.

The tail rays that show so clearly in photographs as in this image made on January 16th require dark skies and 8-inch or larger telescope to see visually. They're very low contrast. Credit: Greg Redfern

The tail rays that show so clearly in photographs as in this image made on January 16th require dark skies and an 8-inch or larger telescope to see visually. They’re very low contrast. Credit: Greg Redfern

The waxing moon will interfere with viewing beginning next weekend and render the comet nil with the naked eye, you’ll still be able to track it in binoculars during that time. Dark skies return around Feb. 7.

Comet Lovejoy captured from the Dark Sky Alqueva Reserve, Portugal on Jan. 11th by Miguel Claro

Delicate streamers show in Comet Lovejoy’s ion tail in this photo from January 13th. Credit: Bernhard Hubl

About Bob King

I'm a long-time amateur astronomer and member of the American Association of Variable Star Observers (AAVSO). My observing passions include everything from auroras to Z Cam stars. Every day the universe offers up something both beautiful and thought-provoking. I also write a daily astronomy blog called Astro Bob.

Friday, January 16, 2015

What Is The Gibbous Moon?

What Is The Gibbous Moon?:

The Moon. Credit: Logan Mancuso

What does it mean when you hear the term “gibbous moon”? It’s when the Moon is more than half full, but not quite fully illuminated, when you look at it from the perspective of Earth. The reason the light changes has to do with how the Moon orbits the Earth.

The average distance between the Earth and the Moon is about 382,500 km (237,675 miles). As the Moon orbits our planet, the illumination of the Sun changes on its surface. The Moon takes about 29.5 days to go from a new moon to a full moon and then back again. This is called a “synodic period” or sometimes, a “synodic month.”

It’s slightly longer than the “sidereal period” or “sidereal month” (27.3 days) for the Moon to return to the same position relative to the stars. That’s because the Earth is moving at the same time along its orbit of the Sun, requiring the Moon to “catch up” to reach the same illumination, according to NASA.

How the phases of the Moon work. Credit: NASA/Bill Dunford

So as the Moon orbits the Earth, the illumination of the Sun changes. When the Moon is in between the Earth and the Sun — with the three objects perfectly aligned — the angle between the Moon and the Sun is 0 degrees. This produces a “new moon”, which is when the Moon is not illuminated or barely illuminated at all.

The first quarter occurs when the Moon is at a 90-degree angle with the Sun, as seen from Earth. Once the Moon’s angle exceeds 90 degrees, that’s when it enters the waxing gibbous phase. At 180 degrees from the Sun, the Moon is fully illuminated (a full moon). Then after it reaches 180 degrees, when the Moon and the Sun are on the opposite sides of the Earth, it becomes a waning gibbous moon.

At 270 degrees, the Moon finishes its gibbous phase, enters the third quarter of its synodic period and becomes a waning crescent, until it reaches the new moon phase and starts the cycle anew. And actually, the Moon’s position around the Earth plays a role in solar and lunar eclipses.

Total solar eclipse in 1999. The alignment of the nearby Moon and massive Sun, the weightiest body in the Solar System by far, didn't cause anyone to float off the ground. To my knowledge. Credit: Luc Viatour

Total solar eclipse in 1999. Credit: Luc Viatour

A solar eclipse can only happen when the Moon is in its “new phase”. This is, again, because of geometry — because the Moon is in between the Sun and the Earth. From time to time, the position of the Moon lines up with the position of the Sun in Earth’s sky. Coincidentally, the Sun and the Moon appear to be about the same size from Earth’s surface, which makes it possible for the Moon to completely (or almost completely) block the Sun. This creates a solar eclipse. The full eclipse phase can last anywhere from seconds to minutes.

By contrast, a lunar eclipse happens when the Moon is in its “full phase.” At this time, the Earth is in between the Moon and the Sun. When the Moon enters the Earth’s shadow, the shadow can completely or partially fall across the Moon’s surface. A total lunar eclipse phase tends to last anywhere from minutes to over an hour. It creates a ruddy (red or brown) glow due to the effect of sunsets and sunrises all around the Earth shining on the Moon at the same time, according to Bad Astronomy’s Phil Plait.

You’ll notice that as the Moon goes through its various phases, it keeps the same side of itself turned towards Earth. This is due to an effect called tidal locking. After the Moon was formed (likely through a near-cataclysmic collision with Earth), its rotation period didn’t align with that of Earth’s. But over millions of years, the tug of the Earth’s gravity produced a bulge in the Moon’s interior on the side closest to Earth.

Tidal locking results in the Moon rotating about its axis in about the same time it takes to orbit the Earth (left side). If the Moon didn’t spin at all, then it would alternately show its near and far sides to the Earth while moving around our planet in orbit, as shown in the figure on the right. Credit: Wikipedia

As Discovery News explains, over time that bulge was pulled back and forth as the Moon orbited Earth. If the rotation is much slower than the orbit, the bulge “lags behind” while the smaller body orbits. Eventually, this causes one side to always face the larger body.

Tidal locking, by the way, is a fairly common phenomenon in our Solar System — particularly at Jupiter and Saturn, which are massive gas giants that (compared to their immense size) have nat-sized moons orbiting close by. Tidal locking also likely takes place with exoplanets that are orbiting close in to their parent stars.

We have done many stories on Universe Today about the Moon. Here’s one about the phases of the Moon. Want to know when the next full moon is going to be? Here’s a handy guide from NASA that covers the phases of the Moon for 6000 years. And here’s a good explainer on the phases of the Moon. We also discussed the formation of the Moon on Astronomy Cast, Episode 17: Where Did the Moon Come From?

About Elizabeth Howell

Like a BOSS: How Astronomers are Getting Precise Measurements of the Universe’s Expansion Rate

Like a BOSS: How Astronomers are Getting Precise Measurements of the Universe’s Expansion Rate:

Distribution of galaxies and quasars in a slice of BOSS out to a redshift of 3, or 11 billion years in the past. (Courtesy: SDSS-III.)

Astrophysicists studying the expansion of the Universe with the largest galaxy catalogs ever assembled are ushering in an exciting era of precision cosmology. Last week, the Sloan Digital Sky Survey (SDSS) issued its final public data release, and scientists working in its largest program, the Baryon Oscillation Spectroscopic Survey (BOSS) also presented their final results at the American Astronomical Society meeting in Seattle, Washington.

By mapping over 10,000 square degrees — 25% of the sky — BOSS is “measuring our universe’s accelerated expansion with the world’s largest extragalactic redshift survey,” according to SDSS-III Director Daniel Eisenstein of the Harvard-Smithsonian Center for Astrophysics. The BOSS results include new and precise measurements of the universe’s expansion rate (called the “Hubble constant”) and matter density, which includes dark matter, stars, gas, and dust.

BOSS conducted its observations at 2.5-meter Sloan Foundation Telescope at Apache Point Observatory in New Mexico, producing spectra and spatial positions for 1.5 million galaxies and 300,000 quasars in a volume equivalent to a cube with length 8.5 billion light-years on a side (see image above). Astronomers used this rich dataset to map the objects’ distributions and to detect the characteristic scale imprinted by baryon acoustic oscillations in the early universe. Sound waves propagate outward with time, like ripples spreading in a pond, and are indicated by a large-scale clustering signal in the positions of galaxies relative to each other (see illustration below). By analyzing this signal at different times, it is possible to study the behavior of the mysterious “dark energy” causing the accelerating expansion of the universe.

An illustration of the concept of baryon acoustic oscillations, imprinted in the early universe and seen today in galaxy surveys. (courtesy: Chris Blake and Sam Moorfield)

In BOSS’s final results, hundreds of scientists in the international collaboration measured this scale with unprecedented precision. In particular, Ashley Ross from Ohio State University presented results that demonstrated the power of combining an analysis of the transverse and line-of-sight distributions of galaxies. In a paper by Eric Aubourg and collaborators, BOSS astronomers measured the cosmic distance scale of galaxies in the “local” universe and of quasars in the distance universe with impressively small systematic errors—at less than the 1% level—when combined with cosmic microwave background constraints. Their cosmological analysis yields a measurement of the Hubble constant and of the matter density of the universe consistent with a “flat” cold dark matter cosmology with a cosmological constant (see below). Cosmological models including curvature, evolving dark energy, or massive neutrinos are not completely ruled out but are less supported by the data than before. Other results from the collaboration will be submitted for publication in the coming months.

Cosmological constraints on the Hubble parameter h, matter density Ω_m, and curvature parameter Ω_k from BOSS’s baryon acoustic oscillations (BAO) combined with supernovae (SN) and Planck results. (Courtesy: Aubourg et al. 2014)

The BOSS dataset “represents the gold standard in mapping out the network of galaxies that comprises the large-scale structure of the Universe…The data enables us to trace, with greater precision than ever before, the presence of dark energy, the behaviour of gravity on cosmic scales, and the effect of massive neutrinos,” says Chris Blake of Swinburne University, not affiliated with the collaboration.

Where will the BOSS team go from here? The collaboration has begun work on SDSS-IV, whose six-year mission includes an ambitious extended BOSS (eBOSS) survey. According to eBOSS Targeting Coordinator Jeremy Tinker of New York University, eBOSS observations of over 700,000 quasars will precisely measure the distance scale “at a much higher redshift regime that is not covered by current large-scale surveys.”

You can read more about BOSS and updates about the three other componenets of the SDSS in our previous article here.
SDSS website

(Full disclosure: Ramin Skibba had been a member of the BOSS collaboration during 2010-2012.)

About Ramin Skibba

Ramin Skibba is an Assistant Project Scientist at the Center for Astrophysics and Space Sciences at the University of California, San Diego. He writes about astronomy and science policy news at his blog (http://raminskibba.net) and about his scientific research at his work website (http://cass.ucsd.edu/~rskibba/).

Big Asteroid 2004 BL86 Buzzes Earth on January 26: How to See it in Your Telescope

Big Asteroid 2004 BL86 Buzzes Earth on January 26: How to See it in Your Telescope:

Artist view of an asteroid passing Earth. On January 26th, beefy 2004 BL86 passes within 750,000 miles of our planet and will become bright enough to see in small telescopes and large binoculars. Credit: ESA/P.Carril

Artist view of an asteroid passing Earth. On January 26th, beefy 2004 BL86 passes within 3.1 times the distance of the Moon to our planet and become bright enough to see in small telescopes and large binoculars. Credit: ESA/P.Carril

A lot of asteroids pass near Earth every year. Many are the size of a house, make close flybys and zoom out of the headlines. 2004 BL86 is a bit different. On Monday evening January 26th, it will become the largest asteroid to pass closest to Earth until 2027 when 1999 AN10 will approach within one lunar distance.

Big is good. 2004 BL86 checks in at 2,230 feet (680-m) wide or nearly half a mile. Add up its significant size and relatively close approach – 745,000 miles (1.2 million km) – and something wonderful happens. This newsy space rock is expected to reach magnitude +9.0, bright enough to see in a 3-inch telescope or even large binoculars.

This graphic depicts the passage of asteroid 2004 BL86, which will come no closer than about three times the distance from Earth to the moon on Jan. 26, 2015. Due to its orbit around the sun, the asteroid is currently only visible by astronomers with large telescopes who are located in the southern hemisphere. But by Jan. 26, the space rock's changing position will make it visible to those in the northern hemisphere. Click to see an animation. Credit: NASA/JPL-Caltech

This graphic depicts the passage of asteroid 2004 BL86, which will safely pass by the Earth on January 26th. Closest approach occurs around 10 a.m (CST) that day. The asteroid is currently only visible by astronomers with large telescopes who are located in the southern hemisphere. But by Jan. 26, the space rock’s changing position will make it visible to those in the northern hemisphere. Click to see an animation. Credit: NASA/JPL-Caltech

This is a rare opportunity then to see an Earth-approaching asteroid so easily. All you need is a good map as 2004 BL86 will be zipping along at two arc seconds per second or two degrees (four Moon diameters) per hour. That means you’ll see it move in real time like a slow satellite inching its way across the sky. Cool!

As you can see from its name, 2004 BL86 was discovered 11 years ago in 2004 by the Lincoln Near-Earth Asteroid Research (LINEAR), an MIT Lincoln Laboratory program to track near-Earth objects funded by the U.S. Air Force and NASA. As of September 15, 2011, the search has swept up 2,423 new asteroids and 279 new comets.

Map showing the hourly progress of 2004 BL86 Monday evening January 26th as it treks across Cancer the Crab not far from Jupiter. Stars are shown to magnitude +9. Numbers at the tick marks show the time (CST) each hour starting at 6 p.m., then 7 p.m., 8 p.m. and so on. Click for a larger version. Created with Chris Marriott’s SkyMap program

All asteroids with well-known orbits receive a number. The first asteroid, 1 Ceres, was discovered in 1801. The 4,150th asteroid, 4150 Starr and named for the Beatles’ Ringo Starr, was found in 1984. 2004 BL86 will likely be the highest-numbered asteroid any of us will ever see. How does 357,439 sound to you?

Some observers prefer a black on white map for tracking asteroids and deep sky objects. Click to view a larger version. Created with Chris Marriott’s SkyMap program

Observers in the Americas, Europe and Africa will have the best seats for viewing the asteroid, which will shine brightest between 7 p.m. and midnight CST from a comfortably high perch in Cancer the Crab not far from Jupiter. The half-moon will also be out but over in the western sky, so shouldn’t get in the way of seeing our speedy celeb.

Not only will 2004 BL86 pass near a few fairly bright stars but the Beehive Cluster (M44) will temporarily gain a new member between 11 p.m. and midnight as the asteroid buzzes across the well-known star cluster.

“Monday, January 26 will be the closest asteroid 2004 BL86 will get to Earth for at least the next 200 years,” said Don Yeomans, who’s retiring as manager of NASA’s Near Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, California, after 16 years in the position.

More detailed map showing the hourly position of the asteroid through central Cancer. Stars plotted to magnitude +9.5. Created with Chris Marriott's SkyMap software

More detailed map showing the hourly position of the asteroid through central Cancer. Stars plotted to magnitude +9.5. Click to get a larger version. Created with Chris Marriott’s SkyMap software

To learn more about the space rock and acquire close-ups of its surface, NASA’s Deep Space Network antenna at Goldstone, California, and the Arecibo Observatory in Puerto Rico will attempt to ping the asteroid with microwaves to create radar-generated images of the asteroid during the days surrounding its closest approach to Earth.

“When we get our radar data back the day after the flyby, we will have the first detailed images,” said radar astronomer Lance Benner of JPL, principal investigator for the Goldstone radar observations of the asteroid. “At present, we know almost nothing about the asteroid, so there are bound to be surprises.”

NASA’s Deep Space Network will be watching during 2004 BL86’s flyby Monday Jan. 26. Credit: NASA

While 2004 BL86 will be brightest Monday night, that’s not the only time amateur astronomers might see it. It comes into view for southern hemisphere observers around magnitude +13 on Jan. 24 and leaves the scene at a similar brightness high in the northeastern sky in the northern hemisphere on the 29th. If you use a star-charting program like Starry Night, Guide, MegaStar and others, you can get updated orbital element packages HERE. Just select your program and download the Observable Unusual Minor Planets file. Open it in your software and create maps for the entire apparition.

One last observing tip before you go your own way. Close asteroids will sometimes be a little bit off a particular track depending on your location. Not much but enough that I recommend you scan not just the single spot where you expect to see it but also nearby in the field of view. If you see a “star” on the move – that’s it.

Let us know if you see our not-so-little cosmic friend. Good luck!

About Bob King

When Two Supermassive Black Holes Merge, It’s a Galactic Train Wreck

When Two Supermassive Black Holes Merge, It’s a Galactic Train Wreck:

An artist's conception of a black hole binary in a heart of a quasar, with the data showing the periodic variability superposed. Credit: Santiago Lombeyda/Caltech Center for Data-Driven Discovery

An artist’s conception of a black hole binary in a heart of a quasar, with the data showing the periodic variability superposed. Image Credit: Santiago Lombeyda / Caltech Center for Data-Driven Discovery

Most large galaxies harbor central supermassive black holes with masses equivalent to millions, or even billions, of Suns. Some, like the one in the center of the Milky Way Galaxy, lie quiet. Others, known as quasars, chow down on so much gas they outshine their host galaxies and are even visible across the Universe.

Although their brilliant light varies across all wavelengths, it does so randomly — there’s no regularity in the peaks and dips of brightness. Now Matthew Graham from Caltech and his colleagues have found an exception to the rule.

Quasar PG 1302-102 shows an unusual repeating light signature that looks like a sinusoidal curve. Astronomers think hidden behind the light are two supermassive black holes in the final phases of a merger — something theoretically predicted but never before seen. If the theory holds, astronomers might be able to witness two black holes en route to a collision of incredible scale.

The light curve combines data from two CRTS telescopes (CSS and MLS) with historical data from the LINEAR and ASAS surveys, and the literature15, 16 (see Methods for details). The error bars represent one standard deviation errors on the photometry values. The red dashed line indicates a sinusoid with period 1,884 days and amplitude 0.14 mag. The uncertainty in the measured period is 88 days. Note that this does not reflect the expected shape of the periodic waveform, which will depend on the physical properties of the system. MJD, modified Julian day. Image Credit: Graham et al.

The light curve combines data from two CRTS telescopes (CSS and MLS) with historical data from the LINEAR and ASAS surveys. Image Credit: Graham et al.

Graham and his colleagues discovered the unusual quasar on a whim. They were aiming to study quasar variability using the Catalina Real-Time Transient Survey (CRTS), which uses three ground-based telescopes to monitor some 500 million objects strewn across 80 percent of the sky, when 20 or so periodic sources popped up.

Of those 20 periodic quasars, PG 1302-102 was the most promising. It had a strong signal that appeared to repeat every five years or so. But what causes the repeating signal?

The black holes that power quasars do not emit light. Instead the light originates from the hot accretion disk that feeds the black hole. Orbiting clouds of gas, which are heated and ionized by the disk, also contribute in the form of visible emission lines.

“When you look at the emission lines in a spectrum from an object, what you’re really seeing is information about speed — whether something is moving toward you or away from you and how fast. It’s the Doppler effect,” said study coauthor Eilat Glikman from Middlebury College in Vermont, in a news release. “With quasars, you typically have one emission line, and that line is a symmetric curve. But with this quasar, it was necessary to add a second emission line with a slightly different speed than the first one in order to fit the data. That suggests something else, such as a second black hole, is perturbing this system.”

So a tight supermassive black hole binary is the most likely explanation for this oddly periodic quasar.

“Until now, the only known examples of supermassive black holes on their way to a merger have been separated by tens or hundreds of thousands of light years,” said study coauthor Daniel Stern from NASA’s Jet Propulsion Laboratory. “At such vast distances, it would take many millions, or even billions, of years for a collision and merger to occur. In contrast, the black holes in PG 1302-102 are, at most, a few hundredths of a light year apart and could merge in about a million years or less.”

But astronomers remain unsure about what physical mechanism is responsible for the quasar’s repeating light signal. It’s possible that one quasar is funneling material from its accretion disk into jets, which are rotating like beams from a lighthouse. Or perhaps a portion of the accretion disk itself is thicker than the rest, causing light to be blocked at certain spots in its orbit. Or maybe the accretion disk is dumping material onto the black hole in a regular fashion, causing periodic bursts of energy.

“Even though there are a number of viable physical mechanisms behind the periodicity we’re seeing — either the precessing jet, warped accretion disk or periodic dumping — these are all still fundamentally caused by a close binary system,” said Graham.

Astronomers still don’t have a good handle on what happens in the final few light-years of a black hole merger. And of course these two black holes still won’t collide for thousands to millions of years. Even watching for the period to shorten as they spiral inward would dwarf human timescales. But the discovery of a system so late in the game proves promising for future work.

The results have been published in Nature.

About Shannon Hall

Shannon Hall is a freelance science journalist. She holds two B.A.'s from Whitman College in physics-astronomy and philosophy, and an M.S. in astronomy from the University of Wyoming. Currently, she is working toward a second M.S. from NYU's Science, Health and Environmental Reporting program. You can follow her on Twitter @ShannonWHall.

Astronomers are Predicting at Least Two More Large Planets in the Solar System

Astronomers are Predicting at Least Two More Large Planets in the Solar System:

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At least two unknown planets could exist in our solar system beyond Pluto. / Credit: NASA/JPL-Caltech.

Could there be another Pluto-like object out in the far reaches of the Solar System? How about two or more?

Earlier this week, we discussed a recent paper from planet-hunter Mike Brown, who said that while there aren’t likely to be any bright, easy-to-find objects, there could be dark ones “lurking far away.” Now, a group of astronomers from the UK and Spain maintain at least two planets must exist beyond Neptune and Pluto in order to explain the orbital behavior of objects that are even farther out, called extreme trans-Neptunian objects (ETNO).

The presently known largest small bodies in the Kuiper Belt are likely not to be surpassed by any future discoveries. This is the conclusion of Dr. Michael Brown, et al. (Illustration Credit: Larry McNish, Data: M.Brown)

We do know that Pluto shares its region Solar System with more than 1500 other tiny, icy worlds along with likely countless smaller and darker ones that have not yet been detected.

In two new paper published this week, scientists at the Complutense University of Madrid and the University of Cambridge noted that the most accepted theory of trans-Neptunian objects is that they should orbit at a distance of about 150 AU, be in an orbital plane – or inclination – similar to the planets in our Solar System, and they should be randomly distributed.

But that differs from what is actually observed. What astronomers see are groupings of objects with widely disperse distances (between 150 AU and 525 AU) and orbital inclinations that vary between 0 to 20 degrees.

“This excess of objects with unexpected orbital parameters makes us believe that some invisible forces are altering the distribution of the orbital elements of the ETNO,” said Carlos de la Fuente Marcos, scientist at UCM and co-author of the study, “ and we consider that the most probable explanation is that other unknown planets exist beyond Neptune and Pluto.”

He added that the exact number is uncertain, but given the limited data that is available, their calculations suggest “there are at least two planets, and probably more, within the confines of our solar system.”

In their studies, the team analyzed the effects of what is called the ‘Kozai mechanism,’ which is related to the gravitational perturbation that a large body exerts on the orbit of another much smaller and further away object. They looked at how the highly eccentric comet 96P/Machholz1 is influenced by Jupiter (it will come near the orbit of Mercury in 2017, but it travels as much as 6 AU at aphelion) and it may “provide the key to explain the puzzling clustering of orbits around argument of perihelion close to 0° recently found for the population of ETNOs,” the team wrote in one of their papers.

The discovery images of 2012 VP113. Each one was taken about two hours apart on Nov. 5, 2012. Behind the object, you can see background stars and galaxies that remained still (from Earth’s perspective) in the picture frame. Credit: Scott S. Sheppard: Carnegie Institution for Science

They also looked at the dwarf planet discovered last year called 2012 VP113 in the Oort cloud (its closest approach to the Sun is about 80 astronomical units) and how some researchers say it appears its orbit might be influenced by the possible presence of a dark and icy super-Earth, up to ten times larger than our planet.

“This Sedna-like object has the most distant perihelion of any known minor planet and the value of its argument of perihelion is close to 0°,” the team writes in their second paper. “This property appears to be shared by almost all known asteroids with semimajor axis greater than 150 au and perihelion greater than 30 au (the extreme trans-Neptunian objects or ETNOs), and this fact has been interpreted as evidence for the existence of a super-Earth at 250 au. In this scenario, a population of stable asteroids may be shepherded by a distant, undiscovered planet larger than the Earth that keeps the value of their argument of perihelion librating around 0° as a result of the Kozai mechanism.”

Of course, the theory put forth in two papers published by the team goes against the predictions of current models on the formation of the Solar System, which state that there are no other planets moving in circular orbits beyond Neptune.

But the team pointed to the recent discovery of a planet-forming disk around the star HL Tauri that lies more than 100 astronomical units from the star. HL Tauri is more massive and younger than our Sun and the discovery suggests that planets can form several hundred astronomical units away from the center of the system.

The team based their analysis by studying 13 different objects, so what is needed is more observations of the outer regions of our Solar System to determine what might be hiding out there.

Further reading:
Carlos de la Fuente Marcos, Raúl de la Fuente Marcos, Sverre J. Aarseth. “Flipping minor bodies: what comet 96P/Machholz 1 can tell us about the orbital evolution of extreme trans-Neptunian objects and the production of near-Earth objects on retrograde orbits”. Monthly Notices of the Royal Astronomical Society 446(2):1867-1873, 2015.

C. de la Fuente Marcos, R. de la Fuente Marcos. “Extreme trans-Neptunian objects and the Kozai mechanism: signalling the presence of trans-Plutonian planets? Monthly Notices of the Royal Astronomical Society Letters 443(1): L59-L63, 2014.

SiNC press release

Comet Lovejoy Now at its Brightest: Images from Around the World

Comet Lovejoy Now at its Brightest: Images from Around the World:

C/2014 Q2 Lovejoy comet passing over perseus and Taurus molecular cloud forming a triangle with the California Nebula (the red nebula on the left), the M45 Pleaides and Hyades in Taurus. Taken on January 14, 2015 from Pragelato, Turin, Italy. Credit and copyright: Leonardo Orazi.

Last night was the first time I was able to spot Comet Lovejoy with unaided eyes. The latest images from our readers and dedicated astrophotographers confirm that now is a good time to see the comet, which is reaching maximum brightness at his week. Spaceweather.com reports that many experienced observers say the comet is now shining at magnitude +3.8. With clear, dark skies C/2104 Q2 is easily seen with binoculars.

Enjoy this gallery of recent images, and if you’ve taken an image, consider joining our Flickr pool and submitting it. We may use your image in an upcoming article!

Comet Lovejoy C/2104 Q2 cruising past the open star Cluster M45 “Pleiades” or “The Seven Sisters.” Credit and copyright: John Chumack.

Comet Lovejoy taken on January 15, 2015 from Singapore. Credit and copyright: Justin Ng.

Comet C/2014 Q2 Lovejoy in a widefield false color image taken on January 16, 2015 from New Mexico Skies. Credit and copyright Joseph Brimacombe.

Comet Lovejoy, C/2014 Q2, a wide binocular field west of M45, the Pleiades star cluster in Taurus, on January 15, 2015, shot from Silver City, New Mexico. The long blue ion tail stretched back for about 8°. Credit and copyright: Alan Dyer.

Comet Lovejoy photographed from Torrance Barrens Dark-Sky Preserve (30 km from Gravenhurst, Ontario, Canada; 200 km north of Toronto) on January 13, 2015. Credit and copyright: Michael Watson.

Comet Lovejoy as seen from Lahore, Pakistan on January 15, 2014, 10:30 pm local time. 35 single images stacked in DSS. Each 8 seconds, ISO 2000, f/5.6, edited in Photoshop. Credit and copyright: Roshaan Bukhari

High resolution 3 panel mosaic of C/2014 Q2 on January 11, 2015. Field of view is approximately 3.5° x 2° and composed of three fields. Many fine streamers are visible emanating from the nucleus. Credit and copyright: SEN/ Damian Peach.

Comet LoveJoy photographed from Kosovo on January 13, 2015. Credit and copyright: Suhel A. Ahmeti.

C2014 Q2 Lovejoy on January 13, 2015. Credit and copyright: Shahrin Ahmad.

Comet Lovejoy on January 11, 2015. Credit and copyright: Henry Weiland.

Wide angle shot of Comet Lovejoy with the constellation Orion, showing rich fields of red nebula, star clouds and dark nebula with the bright green naked eye comet. Credit and copyright: Chris Schur.

Comet Lovejoy traveling through Taurus. Imaged on January 12, 2015 from Bathurst, New South Wales. Credit and copyright: Wes Schulstad.

C2014 Q2 Lovejoy on January 7, 2015, taken from Bannister Green, England. Credit and copyright: Wendy Clark.

NASA Photos Photography

The National Aeronautics and Space Administration (NASA) is the United States government agency responsible for the civilian space program as well as aeronautics and aerospace research. President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA's predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

UFO SIGHTINGS PHOTO PHOTOGRAPHY

The Oxford English Dictionary defines a UFO as "An unidentified flying object; a 'flying saucer'." The first published book to use the word was authored by Donald E. Keyhoe. The acronym "UFO" was coined by Captain Edward J. Ruppelt, who headed Project Blue Book, then the USAF's official investigation of UFOs. He wrote, "Obviously the term 'flying saucer' is misleading when applied to objects of every conceivable shape and performance. For this reason the military prefers the more general, if less colorful, name: unidentified flying objects. UFO (pronounced Yoo-foe) for short." Other phrases that were used officially and that predate the UFO acronym include "flying flapjack", "flying disc", "unexplained flying discs", "unidentifiable object", and "flying saucer". The phrase "flying saucer" had gained widespread attention after the summer of 1947. On June 24, a civilian pilot named Kenneth Arnold reported seeing nine objects flying in formation near Mount Rainier. Arnold timed the sighting and estimated the speed of discs to be over 1,200 mph (1,931 km/h). At the time, he described the objects' shape as being somewhat disc-like or saucer-like, leading to newspaper accounts of "flying saucers" and "flying discs". In popular usage the term UFO came to be used to refer to claims of alien spacecraft. and because of the public and media ridicule associated with the topic, some investigators prefer to use such terms as unidentified aerial phenomenon (or UAP) or anomalous phenomena, as in the title of the National Aviation Reporting Center on Anomalous Phenomena (NARCAP).

UFO PHOTO PHOTOGRAPHY

UFO - Unidentified Flying Object An unidentified flying object, or UFO, in its most general definition, is any apparent anomaly in the sky that is not identifiable as a known object or phenomenon. Culturally, UFOs are associated with claims of visitation by extraterrestrial life or government-related conspiracy theories, and have become popular subjects in fiction. While UFOs are often later identified, sometimes identification may not be possible owing to the usually low quality of evidence related to UFO sightings (generally anecdotal evidence and eyewitness accounts). Stories of fantastical celestial apparitions have been told since antiquity, but the term "UFO" (or "UFOB") was officially created in 1953 by the United States Air Force (USAF) to serve as a catch-all for all such reports. In its initial definition, the USAF stated that a "UFOB" was "any airborne object which by performance, aerodynamic characteristics, or unusual features, does not conform to any presently known aircraft or missile type, or which cannot be positively identified as a familiar object." Accordingly, the term was initially restricted to that fraction of cases which remained unidentified after investigation, as the USAF was interested in potential national security reasons and/or "technical aspects" (see Air Force Regulation 200-2). During the late 1940s and through the 1950s, UFOs were often referred to popularly as "flying saucers" or "flying discs". The term UFO became more widespread during the 1950s, at first in technical literature, but later in popular use. UFOs garnered considerable interest during the Cold War, an era associated with a heightened concern for national security. Various studies have concluded that the phenomenon does not represent a threat to national security nor does it contain anything worthy of scientific pursuit (e.g., 1951 Flying Saucer Working Party, 1953 CIA Robertson Panel, USAF Project Blue Book, Condon Committee).

Photos of Nature | Nature Photography What is The Universe