Tag: stars

Found: An Exoplanet From Another Galaxy

By Andrew Moseman | November 18, 2010 2:44 pm

ExtragalacticExoplanetA fascinating discovery from today’s edition of the journal Science: Astronomers from Germany report a new exoplanet with two startling characteristics. First, it closely orbits a star that has already exhausted its hydrogen supply and moved past the red giant stage, so this hot Jupiter has so far survived without being evaporated (despite its proximity—just 0.12 astronomical units).

But second, and most striking: This planet and star came from another galaxy.

From Phil Plait:

OK, first, this planet is in our own Milky Way galaxy. The star, called HIP 13044, is about 2000 light years away, well inside our galaxy. So how do we know it’s from a different galaxy? All the stars in our galaxy orbit the galactic center, like planets orbit around a star. But many years ago, astronomers noticed that many stars in the sky have the same sort of motion as they orbit, as if they all belong to streams of stars, flowing like water in a river. Many such streams exist, and eventually astronomers figured out that these were the leftover remnants of entire small galaxies that had collided with, been torn apart, and basically eaten by our Milky Way.

HIP 13044 is part of one of those streams, called the Helmi Stream. It’s the remains of a dwarf galaxy the Milky Way tore apart probably more than 6 billion years ago. So the star and its planet formed in an actual other galaxy, one that either orbited the Milky Way or had an unfortunately too-close pass to it. Either way, wow!

During a web conference this morning, study coauthor Rainer Klement said we shouldn’t be surprised the star and planet are still together even though our galaxy tore theirs apart. Galaxies are structures of stars, but the stars themselves are still so far away that even during a galactic breakup they don’t pass near enough to one another to gravitationally influence a planet. “The timescale upon which such stars play a role is larger than the age of the universe,” he said.

Read the rest of Phil’s post at Bad Astronomy.

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Image: ESO

CATEGORIZED UNDER: Space

Astronomers Predict a Bonanza of Earth-Sized Exoplanets

By Andrew Moseman | October 28, 2010 4:04 pm

keckThe universe abounds with Earth-sized planets. That hopeful notion has been reinforced by individual planets finds like possible Goldilocks planet Gliese 581g, by the hordes of planet candidates discovered by the Kepler mission, and now, by a census of a small space in the sky that tells us one in four sun-like stars should possess worlds that are close to the size of Earth.

Take a moment to think about that: One in four.

In Science, exoplanet hunters Geoffrey Marcy and Andrew Howard published their team’s census of 166 nearby stars like ours, of which they picked 22 at random to investigate for planets. They watched the stars’ doppler shifts to hunt for planets over the last five years, and used the results to extrapolate how common terrestrial planets must be far beyond just this set of stars.

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CATEGORIZED UNDER: Space, Top Posts

Record-Setting Neutron Star Shows Astronomers What It's Made of

By Andrew Moseman | October 28, 2010 10:23 am

neutronstarWhere once there was a star 20 times the size of our sun, now there is a record breaker. Astronomers report this week in Nature that when the huge star went supernova, it collapsed into a neutron star that is heaviest they’ve ever seen, with twice the mass of our sun compacted into a tiny space. Aside from taking its place in the record books, this massive monster could reveal what truly goes on deep in the heart of a deceased star.

The neutron star is part of a binary star system called J1614-2230, in which it and a white dwarf are locked in a spin cycle. Thanks to the neutron star’s steady emission of radio waves and a handy trick of relativity, scientists can measure the size of the two objects despite the fact that they’re 3,000 light years from here.

The astronomers took detailed measurements of the radio pulses that reached Earth. As these pulses, which originate from the rotation of the neutron star, passed by the companion white dwarf, their timing was delayed due to the highly warped nature of spacetime—an effect known as Shapiro delay. In a highly inclined, nearly edge-on system such as J1614-2230 the effect allows astronomers to make very accurate measurements both of the neutron star and its companion. [Ars Technica]

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CATEGORIZED UNDER: Space

Hubble Spots a Galaxy Born 13 Billion Years Ago

By Eliza Strickland | October 20, 2010 3:51 pm

most-distant-galaxyFrom Phil Plait:

The record for the most distant object in the Universe ever seen has been smashed: a galaxy has been found at the staggering distance of 13.1 billion light years!

It’s so dim that the faintest star you can see with your unaided eye is 4 billion times brighter. Its distance is simply numbing; the Universe itself is only 13.7 billion years old, so the light from this object began its journey on its way to Earth just 600 million years after the Universe itself formed.

Head to the full post at Bad Astronomy for all the details about how astronomers used the Hubble Space Telescope to find this faraway galaxy, and what the discovery tells us about the infant universe.

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CATEGORIZED UNDER: Space

How Primordial Galaxies Grew Like Gangbusters

By Eliza Strickland | October 14, 2010 3:27 pm

galaxy-gasWhen the universe was young, massive galaxies formed quickly but surprisingly peacefully. Researchers say they’ve found evidence that these galaxies didn’t grow by sucking up the remnant materials from supernovae or by violent collisions with other galaxies–instead they were fed by streams of cold gas that were funneled into their central star-forming region.

Astronomers using the European Southern Observatory’s Very Large Telescope in Chile have observed three primeval galaxies with patches of star formation near their centers, away from the heavy elements that signal the remains of previous stars. The team found that these galaxies were sucking in cool hydrogen and helium from the space between galaxies as fuel. “It solves the problem of providing to the galaxies fuel to form their stars in a continuous way, without having to invoke violent mergers and galaxy interactions,” said study researcher Giovanni Cresci. [SPACE.com]

The study, published in Nature, describes three galaxies that formed just 2 billion years after the Big Bang–which created lots of hydrogen and helium to feed hungry, growing galaxies, but created few heavier elements. Those formed later in stars and supernovae.

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Image: L. Calcada (ESO)

CATEGORIZED UNDER: Space
MORE ABOUT: Big Bang, galaxies, stars

Um… That "Goldilocks" Exoplanet May Not Exist

By Jennifer Welsh | October 12, 2010 5:44 pm

Gliesewhut2A group of Swiss astronomers announced yesterday at the International Astronomical Union’s annual meeting in Turin, Italy, that they couldn’t detect the “goldilocks” exoplanet found by U.S. researchers a few weeks ago. That news of that planet, dubbed Gliese 581g, generated much excitement, since researchers said it was only three times the size of Earth, and it appeared to lie in the habitable zone where liquid water could exist on the surface.

It didn’t take long for some cold water to be thrown on the astronomical community and the space-loving public. Presenter Francesco Pepe and his colleagues claim that it will be years before the data is clear enough to see such a planet.

“We do not see any evidence for a fifth planet … as announced by Vogt et al.,” Pepe wrote Science in an e-mail from the meeting. On the other hand, “we can’t prove there is no fifth planet.” No one yet has the required precision in their observations to prove the absence of such a small exoplanet, he notes. [ScienceNOW].

Such small planets are very hard to find. Astronomers discover these planets by calculating how they interact with the star they orbit, making it wiggle ever so slightly. The American team that identified the planet a few weeks ago saw the wiggles when analyzing a combination of two sets of data.

Astronomer Paul Butler, a member of the U.S. team who is at the Carnegie Institution for Science in Washington, D.C., says he can’t comment on the Swiss work because he wasn’t at the meeting and the data are unpublished. He notes, however, that more observations will likely be needed to solidify the existence of Gliese 581g. “I would expect that on the time scale of a year or two this should be settled.” [ScienceNOW].

There will be more information available when the Swiss team releases its data and methods, but for now you might want to unpack your bags.

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Image: NSF

CATEGORIZED UNDER: Space

How Excited Should We Be About the New "Goldilocks" Exoplanet?

By Andrew Moseman | September 30, 2010 10:03 am

gliese581From Phil Plait:

Astronomers have announced the discovery of a planet with about three times the Earth’s mass orbiting the nearby red dwarf star Gliese 581. That in itself is cool news; a planet like that is very hard to detect.

But the amazing thing is that the planet’s distance from the star puts it in the Goldilocks Zone: the region where liquid water could exist on its surface!

Gliese 581 is about 20 light years away, and astronomers think the planet in the habitable zone is one of at least six in that star system. The new exoplanet orbits much closer to its star than Earth orbits the sun, but its star is a red dwarf, so it needs to be closer to stay warm enough to support liquid water.

But just how like the Earth is this new world? And what does it mean for the prevalence of ‘Goldilocks” planets out there? To find out, read the rest of the post at Bad Astronomy. And check out the scientists’ paper about Gliese 581 (pdf).

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Image: ESO

CATEGORIZED UNDER: Space

Lost and Found: Supernova Remnant Recaptured by Hubble

By Andrew Moseman | September 3, 2010 2:55 pm

SupernovaRingThe one ring is back, and it’s beautiful.

What you see here is the aftermath of stellar death, rediscovered after NASA temporarily lost the ability to watch it play out. Astronomers tracked supernova 1987A after its discovery that year, picking up insights into what happens after a huge star expends itself. But in 2004, the Hubble Space Telescope‘s Space Telescope Imaging Spectrograph went kaput. The May 2009 space shuttle servicing mission repaired this eye in the sky, leading to a study in this week’s edition of the journal Science that reveals what’s behind this fluorescent view, and why that ring shines so brightly.

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CATEGORIZED UNDER: Space

Astronomers Find 2 Giant Exoplanets Locked in an Endless Dance

By Andrew Moseman | August 26, 2010 4:19 pm

Kepler2planetsThe two newest planets spied by the Kepler space telescope are locked in a forever back-and-forth.

When Kepler’s scientists saw a star 2,000 light years away dim slightly, they knew there was the chance it was the telltale signature of a planet passing in front. But when the calculations were done and the confirmation came in, they found a surprise—what they’d seen was actually two planets transiting in front of the star.

NASA says it’s the first time they’ve ever caught such a sight, and today the scientists officially announced the finding with a study in Science. While other studies have found multiple planets around a single star–in fact, it happened earlier this week–those studies have used different planet-detection techniques like the wobble method.

The two worlds, both gas giants, do more than orbit the same star on the same plane, though. They push and pull each other in a motion that keeps the two exoplanets close to arithmetic celestial perfection. Kepler-9B, the larger, orbits the star in 19.24 days on average, the astronomers saw. Kepler-9c, the smaller, completes a revolution in an average of 38.91 days. But every time the scientists checked, 9b’s orbit was getting 4 minutes longer, while 9c’s shrank by 39 minutes.

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CATEGORIZED UNDER: Space

Homey-Looking Alien Star System May Host 7 Planets

By Andrew Moseman | August 25, 2010 10:53 am

NewStarSystemIn August 2006, Pluto received its official demotion to dwarf planet status, taking our solar system down to eight planets. In August 2010, exoplanet hunters say they’ve found a haul of new worlds around a single star; that alien solar system may have seven known planets, meaning the system could be more like our home system than any ever discovered. And one of those worlds could be the smallest exoplanet ever found, too.

The star these planets orbit is called HD 10180, and it lies 127 light years from here. Astronomers at the European Southern Observatory in Chile used a spectrograph called HARPS to track tiny variations in the starlight caused by the pull of the planets.

It found clear evidence for five giant planets similar in size to Uranus or Neptune in our own solar system. But there were also tantalising signs that two other planets are also present, one of which would be the smallest, or least-massive, yet found orbiting another star [Christian Science Monitor].

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CATEGORIZED UNDER: Space
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