News Flash: Asteroid Flying Past Earth Today Has Mini-Moon!

Wonderful news! Asteroid 2004 BL86, which passed closest to Earth today at a distance of 750,000 miles (1.2 million km), has a companion moon. Scientists working with NASA’s 230-foot-wide (70-meter) Deep Space Network antenna at Goldstone, California, have released the first radar images of the asteroid which show the tiny object in orbit about the main body.

While these are the first images of it, the “signature” of the satellite was seen in light curve data reported earlier by Joseph Pollock (Appalachian State University, North Carolina) and Petr Prave (Ondrejov Observatory, Czech Republic) according to Lance Benner who works with the radar team at Goldstone.

2004 BL86 measures about 1,100 feet (325 meters) across while its moon is approximately 230 feet (70 meters) across. The asteroid made its closest approach today (Jan. 26th) at 10:19 a.m. (CST), however it will peak in brightness this evening around 10 p.m. (4:00 UT) at magnitude +9.0. Unlike some flybys, 2004 BL86 will remain within a few tenths of a magnitude of peak brightness from 6 p.m. tonight (CST) through early tomorrow morning, so don’t miss the chance to see it in your telescope.

Don’t expect to see the diminutive moon visually – the entire system will only appear as a point of light, but I’m sure you’ll agree it’s cool just knowing it’s there.

The double asteroid (90) Antiope and S/2000 (90) 1. The two objects are separated by 171 km, and they perform their celestial dance in 16.5 hours. The adaptive optics observations could, however, never resolve the shape of the individual components as they are too small. Credit: ESO
The double asteroid (90) Antiope and its companion S/2000 (90) 1. The two objects are separated by 106 miles (171 km), and they perform their celestial dance in 16.5 hours. The adaptive optics observations couldn’t resolve the shape of the individual components as they are too small. Credit: ESO

Among near-Earth asteroids, about 16% that are about 655 feet (200 meters) or larger are either binary or triple systems. While that’s not what you’d call common, it’s not unusual either. To date, we know of 240 asteroids with a single moon, 10 triple systems and the sextuple system of Pluto (I realize that’s stretching a bit, since Pluto’s a dwarf planet) – 268 companions total. 52 of those are near-Earth asteroids.

With a resolution of 13 feet (4-meters) per pixel we can at least see the roughness of the the main body’s surface and perhaps imagine craters there. No details are visible on the moon though it does appear elongated. I’m surprised how round the main body is given its small size. An object that tiny doesn’t normally have the gravity required to crush itself into a sphere. Yet another fascinating detail needing our attention.

Of course the main asteroid will get your attention tonight. Please check out our earlier story on 2004 BL86 which includes more details as well as charts to help you track it as it flies across Cancer the Crab tonight. This is the best view we’re going to get of it for the next two centuries.

New Simulation Offers Stunning Images of Black Hole Merger

A black hole is an extraordinarily massive, improbably dense knot of spacetime that makes a living swallowing or slinging away any morsel of energy that strays too close to its dark, twisted core. Anyone fortunate (or unfortunate) enough to directly observe one of these beasts in the wild would immediately notice the way its colossal gravitational field warps all of the light from the stars and galaxies behind it, a phenomenon known as gravitational lensing.

Thanks to the power of supercomputers, a curious observer no longer has to venture into outer space to see such a sight. A team of astronomers has released their first simulated images of the lensing effects of not just one, but two black holes, trapped in orbit by each other’s gravity and ultimately doomed to merge as one.

Astronomers have been able to model the gravitational effects of a single black hole since the 1970s, but the imposing mathematics of general relativity made doing so for a double black-hole system a much larger challenge. Over the last ten years, however, scientists have improved the accuracy of computer models that deal with these types of calculations in an effort to match observations from gravitational wave detectors like LIGO and VIRGO.

The research collaboration Simulating Extreme Spacetimes (SXS) has begun using these models to mimic the lensing effects of high-gravity systems involving objects such as neutron stars and black holes. In their most recent paper, the team imagines a camera pointing at a binary black hole system against a backdrop of the stars and dust of the Milky Way. One way to figure out what the camera would see in this situation would be to use general relativity to compute the path of each photon traveling from every light source at all points within the frame. This method, however, involves a nearly impossible number of calculations.  So instead, the researchers worked backwards, mapping only those photons that would reach the camera and result in a bright spot on the final image – that is, photons that would not be swallowed by either of the black holes.

A binary black hole system, viewed from above. Image Credit: Bohn et al. (see
The same binary black hole system, viewed from above. Image Credit: Bohn et al. (see

As you can see in the image above, the team’s simulations testify to the enormous effect that these black holes have on the fabric of spacetime. Ambient photons curl into a ring around the converging binaries in a process known as frame dragging. Background objects appear to multiply on opposite sides of the merger (for instance, the yellow and blue pair of stars in the “northeast” and the “southwest” areas of the ring). Light from behind  the camera is even pulled into the frame by the black holes’ mammoth combined gravitational field. And each black hole distorts the appearance of the other, pinching off curved, comma-shaped regions of shadow called “eyebrows.” If you could zoom in with unlimited precision, you would find that there are, in fact, an infinite number of these eyebrows, each smaller than the last, like a cosmic set of Russian dolls.

In case you thought things couldn’t get any more amazing, SXS has also created two videos of the black hole merger: one simulated from above, and the other edge-on.


The SXS collaboration will continue to investigate gravitationally ponderous objects like black holes and neutron stars in an effort to better understand their astronomical and physical properties. Their work will also assist observational scientists as they search the skies for evidence of gravitational waves.

Check out the team’s ArXiv paper describing this work and their website for even more fascinating images.

Failed Star Is One Cool Companion


Astronomers have located a planet-like star that’s barely warmer than a balmy summer day on Earth… it’s literally the coldest object ever directly imaged outside of our solar system!

WD 0806-661 B is a brown “Y dwarf” star that’s a member of a binary pair. Its companion is a much hotter white dwarf, the remains of a Sun-like star that has shed its outer layers. The pair is located about 63 light-years away, which is pretty close to us as stars go. The stars were identified by a team led by Penn State Associate Professor of Astronomy and Astrophysics Kevin Luhman using images from NASA’s Spitzer Space Telescope. Two infrared images taken in 2004 and 2009 were overlaid on top of each other and show the stars moving in tandem, indicating a shared orbit.

These two infrared images were taken by the Spitzer Space Telescope in 2004 and 2009. They show a faint object moving through space together with a white dwarf. Credit: Kevin Luhman, Penn State University, October 2011. (Click to play.)

Of course, locating the stars wasn’t quite as easy as that. To find this stellar duo Luhman and his team searched through over six hundred images of stars located near our solar system taken years apart, looking for any shifting position as a pair.

The use of infrared imaging allowed the team to locate a dim brown dwarf star like WD 0806-661 B, which emits little visible light but shines brightly in infrared. (Even though brown dwarfs are extremely cool for stars they are still much warmer than the surrounding space. And, for the record, brown dwarfs are not actually brown.) Measurements estimate the temperature of WD 0806-661 B to be in the range of about 80 to 130 degrees Fahrenheit (26 to 54 degrees C, or 300 – 345 K)… literally body temperature!

“Essentially, what we have found is a very small star with an atmospheric temperature about cool as the Earth’s.”

– Kevin Luhman, Associate Professor of Astronomy and Astrophysics, Penn State

Six to nine times the mass of Jupiter, WD 0806-661 B is more like a planet than a star. It never accumulated enough mass to ignite thermonuclear reactions and thus more resembles a gas giant like Jupiter or Saturn. But its origins are most likely star-like, as its distance from its white dwarf companion – about 2,500 astronomical units – indicates that it developed on its own rather than forming from the other star’s disc.

There is a small chance, though, that it did form as a planet and gradually migrated out to its current distance. More research will help determine whether this may have been the case.

Brown dwarfs, first discovered in 1995, are valuable research targets because they are the next best thing to studying cool atmospheres on planets outside our solar system. Scientists keep trying to locate new record-holders for the coldest brown dwarfs, and with the discovery of WD 0806-661 B Luhman’s team has done just that!

A paper covering the team’s findings will be published in The Astrophysical Journal. Other authors of the paper include Ivo Labbé, Andrew J. Monson and Eric Persson of the Observatories of the Carnegie Institution for Science, Pasadena, Calif.; Didier Saumon of the Los Alamos National Laboratory, New Mexico; Mark S. Marley of the NASA Ames Research Center, Moffett Field, Calif.; and John J. Bochanski also of The Pennsylvania State University.

Read more on the Penn State science site here.


A White-Hot Relationship



Two stars have been discovered locked in a mutually-destructive embrace, a relationship that will end with both losing their individual identities as they spiral increasingly closer, eventually becoming a single hot body that is destined to quickly fizzle out.

No, we’re not talking about the cover of a Hollywood tabloid, these are two white dwarf stars 1,140 light-years away in the constellation Leo, and they are the second such pair of their kind ever to be discovered.

Astronomers at the University of Warwick in the UK have identified a binary pair of white dwarf stars named CSS 41177 that circle each other closely in an eclipsing orbit. What’s particularly unique about this pair is that both stars seem to have been stripped down to their helium layers – a feature that points at an unusually destructive history for both.

White dwarfs typically form from larger stars that have burned through their hydrogen and helium, leaving behind hot, dense cores composed of carbon and oxygen – after going through a bloated red giant phase, that is. But when stars are very close to each other, such as in the case of binary pairs, the expanding hydrogen shell from the larger one undergoing its red giant phase is stripped away by its smaller companion, which absorbs the material. Without the compression and heat from the hydrogen layer the first star cannot fuse its helium into heavier elements and is left as a helium white dwarf.

When the time comes for the smaller star to expand into a red giant, its outer layers are likewise torn away by the first star. But the first star cannot use that hydrogen, and so both are left as helium white dwarfs. The unused hydrogen is ultimately lost to the system.

It’s a case of a destructive codependent relationship on a stellar scale.

The white dwarf stars in CSS 41177 will eventually merge together in about a billion years, gaining enough mass in the process to begin fusing their combined helium, thus becoming a single star called a hot subdwarf. This period could last another 100 million years.

This discovery was made using data gathered from the Liverpool Telescope in the Canary Islands and the Gemini Telescope on Hawaii. The paper was accepted for publication in the Astrophysical Journal and is entitled A deeply eclipsing detached double helium white dwarf binary. (Authors: S. G. Parsons, T. R. Marsh, B. T. Gaensicke, A. J. Drake, D. Koester.)


The image above was created by Andrew Taylor, a.k.a. digital_drew. He specializes in starry-night landscapes as seen from speculative planets orbiting familiar stars in our galaxy and was kind enough to provide me with this custom binary pair image. Check out his photostream for more!