The AMS attached to the space station’s exterior (NASA)
This month is Global Astronomy Month (GAM2013) organized by my friends Astronomers Without Borders (AWB). There is a whole host of events going on right this moment to boost astronomy throughout the international community, and as a part of GAM2013, AWB are hosting daily blogs from guest astronomers, writers, physicists and others with a background in space. Today (April 11) was my turn, so I wrote a blog about the fascinating first results to be announced on the International Space Station instrument the Alpha Magnetic Spectrometer — or AMS for short.
Although the AMS’ most recent findings suggest positrons with a signature energy indicative of the annihilation of dark matter — particularly hypothetical weakly interaction massive particles (WIMPS) — it isn’t final proof of dark matter (despite what the tabloid press might’ve told you). But still, it’s exciting and another component of our enduring search for 95.1% of the mass-energy of the universe that is locked in the mysterious and perplexing dark matter and dark energy.
The M87 black hole blasts relativistic plumes of gas 5000 ly from the centre of the galaxy (NASA)
I just spent 5 minutes trying to think up a title to this post. I knew what I wanted to say, but the subject is so “out there” I’m not sure if any title would be adequate. As it turns out, the title doesn’t really matter, so I opted for something more descriptive…
So what’s this about? Astronomers think they will be able to “see” a supermassive black hole in a galaxy 55 million light years away? Surely that isn’t possible. Actually, it might be.
The most exciting thing is that existing sub-millimeter observations of Sgr. A* (the radio source at the centre of our galaxy where the 4 million solar mass black hole lives) suggest there is some kind of active structure surrounding the black hole’s event horizon. If this is the case, a modest 7-antennae VLBI could observe dynamic flares as matter falls into the event horizon.
It would be a phenomenal scientific achievement to see a flare-up after a star is eaten by Sgr. A*, or to see the rotation of a possibly spinning black hole event horizon.
All of this may be a possibility, and through a combination of Sgr. A*’s mass and relatively close proximity to Earth, our galaxy’s supermassive black hole is predicted to have the largest apparent event horizon in the sky.
Or does it?
M87 Might be a Long Way Away, But…
As it turns out, there could be another challenger to Sgr. A*’s “largest apparent event horizon” crown. Sitting in the centre of the active galaxy called M87, 55 million light years away (that’s over 2,000 times further away than Sgr. A*), is a black hole behemoth.
M87’s supermassive black hole consumes vast amounts of matter, spewing jets of gas 5,000 light years from the core of the giant elliptical galaxy. And until now, astronomers have underestimated the size of this monster.
Karl Gebhardt (Univ. of Texas at Austin) and Thomas Jens (Max Planck Institute for Extraterrestrial Physics in Garching, Germany) took another look at M87 and weighed the galaxy by sifting through observational data with a supercomputer model. This new model accounted for the theorized halo of invisible dark matter surrounding M87. This analysis yielded a shocking result; the central supermassive black hole should have a mass of 6.4 billion Suns, double the mass of previous estimates.
Therefore, the M87 black hole is around 1,600 times more massive than our galaxy’s supermassive black hole.
A Measure for Dark Matter?
Now that the M87 black hole is much bigger than previously thought, there’s the tantalizing possibility of using the proposed VLBI to image M87’s black hole as well as Sgr. A*, as they should both have comparable event horizon dimensions when viewed from Earth.
Another possibility also comes to mind. Once an international VLBI is tested and proven to be an “event horizon telescope,” if we are able to measure the size of the M87 black hole, and its mass is confirmed to be in agreement with the Gebhardt-Jens model, perhaps we’ll have one of the first indirect methods to measure the mass of dark matter surrounding a galaxy…
Oh yes, this should be good.
UPDATE!How amiss of me, I forgot to include the best black hole tune ever:
Publication: The Black Hole Mass, Stellar Mass-to-Light Ratio, and Dark Matter Halo in M87, Karl Gebhardt et al 2009 ApJ 700 1690-1701, doi: 10.1088/0004-637X/700/2/1690.
Via: New Scientist
From Pluto, looking at its icy moons in the Kuiper belt (NASA)
The Pioneer Effect is a mysterious observation of a number of man-made probes that venture through and beyond the Solar System. Originally noticed in the slight drift of the Pioneer 10 and Pioneer 11 spacecraft (launched in 1972 and 1973) from their calculated trajectories, scientists have been at a loss to explain the tiny, yet constant, extra-sunward acceleration.
However, there are other, more mundane ideas. Perhaps there is a tiny fuel leak in the probes’ mechanics, or the distribution of heat through the spacecraft is causing a preferential release of infrared photons from one side, nudging them off course.
Finding an answer to the Pioneer effect probably won’t surface any time soon, but it is an enduring mystery that could have a comparatively simple explanation, within the realms of known science, but there’s also the possibility that we could also be looking at some entirely new physics.
In an attempt to single out whether the Pioneer anomaly is an artefact with the spaceships themselves, or unknown in the physics of the Universe, astronomers decided to analyse the orbits of the planets in the outer Solar System. The rationale being that if this is a large-scale influence, some observable periodic effects should be evident in the orbit of Pluto.
So far, no effect, periodic or otherwise, has been observed in the orbit of Pluto. If the effect isn’t big enough to influence Pluto, does this mean we can narrow the search down to spaceship-specific artefacts?
Not so fast.
Gary Page and John Wallin from George Mason University in Virginia and David Dixon from Jornada Observatory in New Mexico, have published a paper pointing out that the suggestion that the Pioneer effect doesn’t influence Pluto is flawed. Pluto’s orbit is far less understood than the orbits of the inner Solar System planets, as, let’s face it, Pluto is far away.
We simply don’t possess the data required to cancel out the Pioneer effect on planetary bodies in the outer-Solar System to reach the conclusion the anomaly doesn’t influence Pluto.
“Of course, this does not mean that the Pioneer effect exists. It does mean that we cannot deny the existence of the Pioneer effect on the basis of motions of the Pluto as currently known.” — Page et al., 2009
So, back to the drawing board. This is a fascinating study into a true Solar System mystery; bets are on as to the real reason why our interplanetary probes are being knocked off course…
Immediately after the Big Bang, 13.72 billion (±120 million) years ago, the Universe was filled with energy. Nothing but energy. No protons, electrons, quarks or photons; just energy. Even the fundamental forces of nature (gravity, weak, strong, electromagnetic) were a confused mess and could not be distinguished, but that issue didn’t last for long. 10-43 seconds after the Big Bang the grand unification epoch began, when gravity is thought to have separated from the soup. Shortly after, the strong force separated from the electroweak force in a period called the electroweak epoch. Continue reading “Did Dark Matter Reionize the Universe?”
I especially liked the Slacker question concerning the growing number of people opposed to the idea of dark energy accusing cosmologists of “drinking the same Kool Aid” (in reference to the perceived thought that dark energy might be a crazy idea), to which Turner replies with, “Well we do all drink the same Kool Aid, that is true. I’m Mr Kool Aid!”
It is a really entertaining interview, providing an insight to the cutting edge of cosmological thought and excitement for the continuing work being done in the field.
Great work Slacker Astronomy! Now I feel like the slacker, Astroengine.com didn’t manage any podcasts direct from the scene of the AAS… I must remember by dictaphone in June for the next AAS in Pasadena!
When the Galileo probe used the Earth for a gravitational slingshot, an anomaly in its velocity was observed (NASA)
This is a captivating mystery. In 1990 and 1992 when the Jupiter probe Galileo used the Earth for gravitational assists (or “slingshots”), ground-based observers noticed a small (unexpected) boost in velocity as the spacecraft approached Earth. A boost in a few millimetres per second had also been observed in the slingshot of NASA’s NEAR probe two years previously. The same was seen in the flybys of Cassini (in 1999), MESSENGER and Rosetta (in 2005). Many explanations have been put forward – including my favourite that it could be dark matter in Earth orbit kicking our robotic explorers around – but flyby anomalies may have a more mundane explanation.
In keeping with Occam’s Razor (i.e. the simplest explanation is usually the right one), a short paper has been published suggesting that flyby anomalies can be accounted for by using conventional physics… Continue reading “Flyby Anomalies Solved?”
astroengine.com 