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.
Vesta confirmed as venerable planet progenitor
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.
My article highlights Vesta’s importance in our understanding of asteroids and meteorites, as well some remaining mysteries that continued study may illuminate.
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.
Ron is a visiting journalist at Harvard from April 23 to May 18, 2012. He’ll be a guest at the Harvard-Smithsonian Center for Astrophysics’ Institute for Theory and Computation, attending seminars and lectures and chatting with scientists at both Harvard and MIT. Hope to come back with several cool stories so stay tuned!
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.
Several sites highlighted my breaking news story on what may be the most distant galaxy known in the Universe:
- Knight Science Journalism Tracker, one of the most respected trackers of science stories, highlights the article:
[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.
Update: The National Science Foundation’s Science360 also highlights the scoop.
Infant galaxy offers tantalizing peek at early Universe
Astronomers are claiming a new benchmark in the quest to see the Universe’s first galaxies. By taking advantage of a rare cosmic zoom lens — where the gravity of a large mass magnifies light from objects in the distant background — a team of US and European researcher has spotted a galaxy so remote its light was emitted just 490 million years after the Big Bang, when the Universe was a mere 3.6% of its current age.
Read my entire article, which includes how existing and upcoming telescope capabilities could be used to investigate this galaxy further and what the find means for our understanding of the Universe’s number of galaxies.
My latest article is about new research that adds to the uncertainty of how the Moon was formed by looking at the Moon’s isotopic composition:
Question over theory of lunar formation
A chemical analysis of lunar rocks may force scientists to revise the leading theory for the Moon’s formation: that the satellite was born when a Mars-sized body smacked into the infant Earth some 4.5 billion years ago.
If that were the case, the Moon ought to bear the chemical signature of both Earth and its proposed ‘second’ parent. But a study published today in Nature Geoscience1 suggests that the Moon’s isotopic composition reflects only Earth’s contribution.
My latest Scientific American article reports a major breakthrough in modeling…snowflakes:
Snowflake Growth Successfully Modeled from Physical Laws
Mathematicians have re-created the intricate patterns of ice formation, a breakthrough that could lead to new models of red blood cells, soap bubbles and other surfaces that evolve over time
Scientists as far back as Johannes Kepler have pondered the mystery of snowflakes: Their formation requires subtle physics that to this day is not well understood. Even a small change in temperature or humidity can radically alter the shape and size of a snowflake, making it notoriously difficult to model these ice crystals on a computer. But after a flurry of attempts by several scientists, a team of mathematicians has for the first time succeeded in simulating a panoply of snowflake shapes using basic conservation laws, such as preserving the number of water molecules in the air.