All posts by Ron Cowen

Andromeda, Milky Way to Collide [Nature]

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.

Source: NASA, ESA, Z. LEVAY AND R. VAN DER MAREL (STSCI), T. HALLAS, AND A. MELLINGER
Source: NASA, ESA, Z. LEVAY AND R. VAN DER MAREL (STSCI), T. HALLAS, AND A. MELLINGER

Seeing Venus’ Silhouette [Science]

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).

Black Hole’s Newly Seen Y-Rays Suggest Recent Activity [Nature]

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.

Credit: David A. Aguilar (CfA)
Credit: David A. Aguilar (CfA)

NASA’s Visit to Solar System’s 2nd Biggest Asteroid Vesta Yields New Data about Asteroid Families [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.

Update: The Knight Science Journalism Tracker once again notes my science reporting by highlighting this and my previous Vesta-related story:

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.

NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Off to Harvard for a Stay as Visiting Journalist at the Center for Astrophysics

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!

Where’s the Dark Matter? New Study Finds None Near the Solar System [Nature]

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.

Credit: ESO/H.H.Heyer
Credit: ESO/H.H.Heyer

(SCOOP) Coverage of My Recent Early-Universe Scoop

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.

    and

    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.

(SCOOP) about the Early Universe! [Nature]

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.

Image: NASA/STSCI
Image: NASA/STSCI

A Moon-Sized Mystery [Nature]

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.

Read about this research as well as some of the other moon-creation theories!

Image: APOD/NASA
Image: APOD/NASA