Are there massive black holes that move about the universe? In my recent article in Science notes, initial observations with the Hubble Space Telescope and follow-up data collection using NASA’s Chandra x-ray Observatory suggest this is the case. If so, then this would verify Einstein’s theory of general relativity under previously untested conditions.
Do Solo Black Holes Roam the Universe?
Even gravitational monsters can get the heave-ho. Two mysterious bright spots in a disheveled, distant galaxy suggest that astronomers have found the best evidence yet for a supermassive black hole being shoved out of its home.
Observations with NASA’s Chandra x-ray Observatory revealed that only one of the compact visible-light sources—a blob that lies about 8000 light-years from the galaxy’s estimated center—emits x-rays. The high-energy radiation is believed to be a sign that this blob is a supermassive black hole munching away on surrounding gas.
Even better than the image below, this short video explains how the big black hole may have formed.
Our galaxy, the Milky Way galaxy, is set to change dramatically if new findings about the Andromeda galaxy’s direction and path are correct. My latest Nature article, excerpted below, reports the new findings and what they mean.
Andromeda on collision course with the Milky Way
It’s a definite hit. The Andromeda galaxy will collide with the Milky Way about 4 billion years from now, astronomers announced today. Although the Sun and other stars will remain intact, the titanic tumult is likely to shove the Solar System to the outskirts of the merged galaxies.
For decades, scientists have known that Andromeda is falling towards our home Galaxy at a rate of 110 kilometres per second and that the two might eventually collide as a result of their mutual gravity. But because astronomers could easily measure Andromeda’s velocity only along the line of sight to Earth, no one could be sure whether the future encounter would constitute a major merger, a near-miss or a glancing blow.
The image below is how the Milky Way may look after the Andromeda galaxy hurtles through.
For the last time this century, Venus will pass across the face of the sun on June 5-6. Adorning the sun with a black beauty mark as big as a large sunspot, this 6.5-hour minieclipse (only part of which can be seen from the U.S. mainland) mimics the way most planets beyond the solar system are now detected. See my preview in Science magazine (pdf version available for those who do not subscribe).
The quiescent monster at the center of the Milky Way—a supermassive black hole weighing about four million sun—used to be a lot more active.
Ghostly jets seen streaming from Milky Way’s core
Astronomers have found the best evidence yet that the dormant gravitational monster that lies at the centre of the Milky Way — a supermassive black hole known as Sagittarius A* — recently emitted a pair of γ-ray jets.
As they feed on stars and clouds of gas that stray too close, black holes at the centres of other galaxies create bright jets that can be seen across cosmic distances. But the Milky Way’s black hole shows no signs of such activity. Now, the Fermi Gamma-ray Space Telescope has picked up some faint γ-ray signals that suggest that Sagittarius A* has not always been so tranquil. The black hole could even have been active as recently as 20,000 years ago, after gulping down a gas cloud with a mass about 100 times that of the Sun, says Douglas Finkbeiner of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.
Not part of my Nature article, but interesting nonetheless, is that the jets—composed of gamma-ray emitting charged particles—could have inflated the bubbles. To do so, the “faint, pathetic jets” observed by Fermi would have had to be much brighter, and carried more energy, in the past, says Finkbeiner. “We infer that that most of the time over the last million years, the jets have been perhaps ten times as bright.”
He adds that Fermi does not see the jets within about 10,000 light-years of the galaxy’s center, an indication that Sagittarius A* switched off its activity some 20,000 to 30,000 years ago, assuming the jets travel at about one–third the speed of light.
The artist’s illustration below, which shows the jets going all the way to the Milky Way’s center, reflects how the jets used to appear, not how they appear now.
Is the blob seen near the bright star Fomalhaut a planet or not? Only Hubble has ever seen the point of light, but new Hubble observations scheduled for end of May, plus a reanalysis of previous Hubble data may help settle the question. See my story posted May 23 at news section of Nature.
NASA’s Dawn spacecraft won’t end its 13-month-long visit to Vesta, the Solar System’s second biggest asteroid, until August, but researchers have now solidified the rock’s reputation as an archetype for understanding planetary evolution. In six reports in the 11 May edition of Science, Dawn mission scientists have confirmed several long-held assumptions about Vesta and detailed some puzzles about the roughly 520-kilometer-diameter body.
NatureNews (blog) Ron Cowen: Vesta confirmed as venerable planet progenitor ; the ‘confirmed’ in the hed is a good way to say this is not surprise news, but incremental news. Cowen, on constant prowl for news before it is wide news, includes a link to a previous post on Vesta’s topography and what it might mean, from meetings last fall.
Survey finds no hint of dark matter near Solar System
In the largest survey of its kind to date, astronomers scouring the space around the Solar System for signs of dark matter — the hypothetical material believed to account for more than 80% of the mass in the Universe — have come up empty-handed.
If confirmed, the surprising result would upend a long-established consensus, researchers not involved in the study say. For decades, cosmic theories have relied on dark matter — which exerts gravitational pull but emits no light — to be the hidden scaffolding that explains how structure arose in the Universe, how galaxies formed and how the rapidly spinning Milky Way manages to keep from flying apart. Without dark matter, theorists say, the visible material in the Universe, such as stars and gas, would not have the heft to do the job alone.
The rest of the article explains how the research was conducted and what the scientific community thinks of the finding.
[NatureNews’] ace scoop-hungry reporter Ron Cowen late last week filed on a report, at the preprint server for physics-related news arXiv, that a large international team has gotten an image of a galaxy as it was when the universe was a mere 490 million years old.
Cowen writes the story well, and includes the enticing angle that if NASA’s Webb Telescope survives its budgetary excesses and goes into operation, its large IR mirror should offer a much better look at this galaxy – dubbed MACS1149-JD1.
American Scientist republished part of the article as part of its Science in the News section, which is a roundup of the most important and exciting science news pieces.
The article was mentioned here, on my Tumblr site, shortly after publication.